8.25 Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

8.25 Hydrometallation Group 4 (Si, Sn, Ge, and Pb) AP Dobbs, University of Greenwich, Chatham Maritime, UK, and Queen Mary University of London, London, UK FKI Chio, Queen Mary University of London, London, UK r 2014 Elsevier Ltd. All rights reserved.

8.25.1 8.25.2 8.25.2.1 8.25.2.1.1 8.25.2.1.2 8.25.2.2 8.25.2.2.1 8.25.2.2.2 8.25.2.2.3 8.25.2.2.4 8.25.2.3 8.25.2.3.1 8.25.2.3.2 8.25.2.4 8.25.2.5 8.25.2.5.1 8.25.2.5.2 8.25.3 8.25.3.1 8.25.3.1.1 8.25.3.2 8.25.3.2.1 8.25.3.2.2 8.25.3.2.3 8.25.3.3 8.25.3.3.1 8.25.3.3.2 8.25.3.3.3 8.25.3.4 8.25.4 8.25.4.1 8.25.4.1.1 8.25.4.1.2 8.25.4.2 8.25.4.3 8.25.4.4 8.25.5 8.25.5.1 8.25.5.1.1 8.25.5.2 8.25.5.3 8.25.5.4 References

Introduction Hydrosilylation Introduction Hydrosilanes available Theoretical and mechanistic aspects Hydrosilylation of Carbon–Carbon Triple Bonds Hydrosilylation of ethyne Hydrosilylation of monosubstituted alkynes Hydrosilylation of disubstituted alkynes Applications of alkyne hydrosilylation Hydrosilylation of Carbon–Carbon Double Bonds Hydrosilylation of monosubstituted alkenes Hydrosilylation of disubstituted alkenes Hydrosilylation of Conjugated and Related Systems Synthetic Transformations and Applications Applications of hydrosilylation reactions Applications of hydrosilylation reactions in total synthesis Hydrostannylation Introduction Hydrostannanes available Hydrostannylation of Carbon–Carbon Triple Bonds Hydrostannylation of ethyne Hydrostannylation of monosubstituted alkynes Hydrostannylation of disubstituted alkynes Hydrostannylation of Carbon–Carbon Double Bonds Hydrostannylation of monosubstituted alkenes Hydrostannylation of disubstituted alkenes Synthetic transformations and applications Applications of Hydrostannylation Reactions in Total Synthesis Hydrogermylation Introduction Available germanes Synthesis of organohydrogermanes Hydrogermylation of Carbon–Carbon Triple Bonds Hydrogermylation of Carbon–Carbon Double Bonds Synthetic Transformations and Applications Hydroplumbation Introduction Available plumbanes Hydroplumbation of Carbon–Carbon Triple Bonds Hydroplumbation of Carbon–Carbon Double Bonds Synthetic Transformations and Applications

Glossary Hydrogermylation The addition of H–Ge, i.e., a hydrogen and a germanium-containing group across a multiple bond, such as an alkyne, alkene, or carbonyl group. Hydroplumbation The addition of H–Pb, i.e., a hydrogen and a lead-containing group across a multiple bond, such as an alkyne or alkene.

964

965 965 965 965 965 966 967 967 970 970 976 977 977 978 978 978 978 979 979 979 979 979 979 981 981 981 981 982 982 982 982 983 983 984 986 988 991 991 991 991 994 994 995

Hydrosilylation The addition of H–Si, i.e., a hydrogen and a silicon-containing group across a multiple bond, such as an alkyne, alkene, or carbonyl group. Hydrostannylation The addition of H–Sn, i.e., a hydrogen and a tin-containing group across a multiple bond, such as an alkyne, alkene, or carbonyl group.

Comprehensive Organic Synthesis II, Volume 8

doi:10.1016/B978-0-08-097742-3.00827-2

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

8.25.1

965

Introduction

This chapter will discuss the addition reactions of the hydrides of the Group IV elements to carbon–carbon double and triple bonds. Although there is no corresponding chapter in the first edition of Comprehensive Organic Synthesis, the material presented here will follow on from Chapters 3.9 and 3.12 and the reader is referred back to these.

8.25.2

Hydrosilylation

8.25.2.1

Introduction

The addition of hydrosilanes to alkenes and alkynes is called hydrosilylation, a reaction that was discovered when a mixture of L-octene and trichlorosilane was heated in the presence of diacetyl peroxide. This reaction is particularly useful for the synthesis of organosilicon compounds. Since then, a variety of catalysts and conditions have been reported. The characteristic features and applications of the reactions are discussed in this chapter. A review of the synthesis of silicon-containing compounds via Lewis acid-catalyzed reactions has been published.1 Reactions of organosilanes and organogermanes have developed as popular alternatives to the Stille and Suzuki reactions for Pd-catalyzed cross-coupling reactions. Their use has been reviewed.2 Si-C coupling reaction of hydrosilanes with activated organic compounds have also been reviewed.3 Before discussing hydrosilylation or the related reactions covered in this chapter, it is worth mentioning the nomenclature associated with the adducts obtained; this is illustrated in the example below the hydrosilylation of 1-hexyne 1, where it is possible to obtain three isomeric products: β-(E), β-(Z), and α (Scheme 1). The selectivity of the hydrosilylation/stannylation reactions is briefed as follows. n-Bu n-Bu

H

+

SiR3

n-Bu

H

n-Bu

H

SiR3

R3Si

H

R3SiH

1

H

H -(Z )

H

-(E )



Scheme 1

8.25.2.1.1

Hydrosilanes available

Many hydrosilanes are now commercially available from all the leading suppliers and are too numerous to list here.

8.25.2.1.2

Theoretical and mechanistic aspects

A detailed review of the reactivity of the metal–silicon bond in organometallic chemistry has been published.4 Carbene complexes of the type M¼ E (E¼ Si or Ge) have been reported with hydrogen atoms on both the metal center and the E atom. These readily undergo hydrosilylation and hydrogermylation reactions, as well as reaction with nitriles, ketones, and heterocumulenes.5 Lewis has studied the relative rates of platinum-catalyzed hydrosilylation of terminal olefins versus internal alkynes in competitive reactions. (EtO)3SiH added almost exclusively (97%) to PhC¼ CPh rather than styrene. With equimolar amounts of 2-decyne and 1-hexene, it gave a 78:22 ratio of alkyne products to alkene products. Its reaction with equimolar amounts of styrene and 1-phenyl-1-propyne gave a 78:22 ratio of alkyne products to alkene ones. The silane, Me3SiOSiMe2H reacted with equimolar amounts of 2-decyne and 1-hexene to give a 90:10 ratio of alkyne products to alkene products. All of the products had E stereochemistry about the C ¼ C double bond.6 The mechanisms and kinetics of the hydrosilylation of phenylacetylene by iridium complexes including [Ir(COD) (η2-iPr2PCH2CH2OMe)][BF4] have studied.7 Alkyne hydrosilylation has been examined in detail for the catalysts [IrH(H2O)(bq) L2]SbF6 (L ¼ PPh3, bq ¼ 7,8-benzoquinolinato) and RhCl(PPh3)3. In addition to the expected products, two unusual products are reported, namely the dehydrogenative silation product RC¼ CSiR3, formed by β-elimination from a vinylmetal intermediate, and secondly allylsilane products of vinylsilane isomerization. The iridium catalyst is advantageous in that it does not give fast vinylsilane isomerization cf RhCl(PPh3)3, thus allowing formation and isolation of the thermodynamically less stable cis rather than the more stable trans-vinylsilane isomer RCH¼ CH(SiR3′).8 The photoactivated hydrosilylation of alkynes has been reported, involving irradiation at λ¼ 350 nm and a platinum(II) bis (acetylacetonato) catalyst.9 Ozawa has studied the crossover in selectivity (E/Z) with substrate and terminal alkynes for rutheniumcatalyzed hydrosilylation.10 A detailed investigation of the platinum-catalyzed hydrosilylation of internal arylalkynes has demonstrated that the position of substituents on the aromatic ring can influence regioselectivity (Scheme 2).11 On addition of triethylsilane to the triple bond, an ortho-substituent in arylalkylalkynes and diarylalkynes always gave the α-isomer 2 regardless of the electronic nature (π-electron withdrawing or σ-electron donating) of the substituent. Both H2PtCl6 and, for the first time, PtO2 were efficient catalysts for the hydrosilylation reaction.

966

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)



Et3SiH (1.5 equivalents) [Pt] cat. 5 mol%



R1 R

60 °C, 1 h

R

H SiEt3

-isomer 2

R1

R1

R1 + R

SiEt3 H -isomer

+

H

R

H Z+E

R = CO2Et, R1 = n-C5H11 [Pt] cat. = H2PtCl6, Pt (PPh3)4, Pt/C, PtO2 Scheme 2

There is evidence for the intermediacy of colloids in hydrosilylation reactions involving Karstedt's catalyst (Pt[(vinyl) Me2SiOSiMe2(vinyl)]).12 The hydrosilylation of deuterated acetylene with triethoxysilane13 is important because the hydrosilylation may be directed to be either cis or trans, by the use of an appropriate metal catalyst, thus permitting selective D labeling. The hydrosilylation of non-1ene with phenylsilane in the presence of yttrium and lutetium bisguanidinate hydride complexes14 is first order in olefin and zero order in phenylsilane, indicating that the insertion of non-1-ene into the Ln–H bond is the rate-determining stage of the process. The current mechanism of asymmetric induction in catalytic hydrogenation, hydrosilylation, and cross-coupling reactions on metal complexes has been reviewed.15

8.25.2.2

Hydrosilylation of Carbon–Carbon Triple Bonds

A number of excellent reviews have appeared covering both alkyne hydrosilylation reactions16,17 and methods for preparing vinylsilanes from alkynes. A comprehensive review of iron-catalyzed hydrosilylation reactions has been published.18 Anderson has published a comprehensive review on the synthesis of vinylsilanes, including many examples involving hydrosilylation reactions of alkynes.19 Trost has reviewed the addition of metalloid hydrides to alkynes, with particular emphasis on boron, silicon and tin.20 Yi has published a short review/summary of his own group's work on regio- and stereoselective hydrosilylation and oxidative silylation of alkenes and alkynes.21 Treatment of terminal alkynes with HSiEt3 in the presence of (PCy3)2(CO)RuHCl gave the cisalkenes, whereas dehydrosilylation of α-olefins under the same conditions gave the trans-vinylsilane. A review has been published on the preparation and applications of heterogenous catalysts for hydrosilylation reactions22 and solid-phase hydrosilylation reactions with the participation of modified silica surfaces have been reviewed.23 There have been many reports of novel catalysts being developed for the hydrosilylation of alkynes; some are described in detail in this section, whereas others will simply be listed here. For example, using AlCl3/hydropolysilanes24 including for the cyclization of 1,6-heptadiyne; ethyl aluminum dichloride and diethyl aluminum chloride are efficient Lewis acids for the regioselective hydrosilylation of propiolate esters with tris(trimethylsilyl)silane giving β-silicon substituted Z-alkenes;25 lithium aluminum hydride for dehydrogenative coupling reactions;26 N-heterocyclic carbene complexes of zero-valent platinum divinyltetramethyldisiloxane (for alkynes, alkenes, ketones, and α,β-unsaturated ketones) giving in the former cases high selectivity for the 1-functionalized product;27 iron(0) dinitrogen (iPrPDI)Fe(N2)2 and silane complexes;28 rhodium(I) complexes with hemilabile N-heterocyclic carbenes gave predominantly β-(Z)-vinylsilanes with 1-hexyne and β-(E) and α-bis(silyl)alkenes with trimethylsilylacetylene;29 silver and platinum complexes of N,C-chelating oxazole-carbene ligands;30 using [Cp⁎Ru(MeCN)3] PF6;31–35 diphosphinidenecyclobutene ruthenium complexes [RuCl(μ-Cl)(CO)(DPCB-OMe)]2 and [RuH(μ-Cl)(CO)(DPCBOMe)]236 for both Ru–C and H–Si metathesis and hydrosilylation of terminal alkynes; one example of solvated gold atoms being used to catalyze the hydrosilylation of 1-hexyne, giving primarily β-(E) products;37,38 organoyttrium complexes such as Cp⁎2YCH3·THF.39 Although the majority of transition metal-catalyzed hydrometalations and carbometalations proceed in a cis manner, the Lewis acid promoted reactions tend to proceed in a trans manner, as reported by Yamamoto: hydrosilylation, hydrostannylation, carbosilylation, and carbostannylation or unactivated alkynes with organosilanes or organostannanes all gave the trans-vinylsilyl or vinylstannyl compounds.40 A detailed study of the catalytic hydrosilylation of acetylenes mediated by phosphine complexes of cobalt(I), rhodium(I), and iridium(I) has been reported by Field and has demonstrated that complexes including [Co(PPh3)3Cl], [Co(PPh3)2(CO)2Cl], [Co (PMe3)3Cl], [Co(PMe3)2(CO)2Cl], [Rh(dppe)(CO)Cl], [Rh(PPh2Me)2(CO)Cl], [Ir(dppe)(CO)Br], and [Ir(PPh2Me)2(CO)Cl] all catalyze the hydrosilylation of a number of alkynes including 1-hexyne, phenylacetylene, and 1-phenyl-1-propyne with triethylsilane.41 Iridium complexes including [Ir(COD)(η2-iPr2PCH2CH2OMe)][BF4] have also been studied for the hydrosilylation of phenylacetylene.7 Rhodium(III) and iridium(III) complexes of Tröger's base (TB) have been prepared by reaction of TB with MCl3 (M ¼ Rh or Ir) and the rhodium complex found to be a highly regio- and stereoselective catalyst for the hydrosilylation of alkynes.42 Eisen has started to report the use of organoactinide metal complexes in dimerization and hydrosilylation reactions of terminal alkynes.43–45 The cationic actinide complex [(Et2N)3U][BPh4] was reported as an active catalyst precursor for the dimerization of terminal alkynes. Furthermore, in the presence of PhSiH3, the complex promoted the hydrosilylation of terminal alkynes, albeit producing a myriad of products depending on the nature of the alkene, the solvent, and reaction temperature.45 An intermediate

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

967

uranium-hydride complex is proposed. The same authors reported Cp⁎2AnMe2 (An¼ Th or U) also as efficient hydrosilylation catalysts for terminal alkynes.44 Organothorium complexes have also been reported and studied in hydrosilylation reactions.43

8.25.2.2.1

Hydrosilylation of ethyne

The vapor-phase hydrosilylation of acetylene with trichlorosilane or trimethoxysilane using a tetraammineplatinum(II) chloride catalyst in polyethylene glycol medium supported on silica gel has been reported.46 The insertion of ethyne into the Ru–Si bond of coordinatively unsaturated ruthenium silyl complexes has been reported by Roper, including the crystal structures of several adducts.47 Reaction of Mes2Si(F)H with ethyne in the presence of H2PtCl6 gives dimesitylvinylfluorosilane Mes2Si(F)CH¼ CH2, which on reaction with tert-butyllithium gives a highly stable silene, dimesitylneopentylsilene, Mes2Si¼ CHCH2tBu.48

8.25.2.2.2

Hydrosilylation of monosubstituted alkynes

Trost has widely studied and applied the ruthenium-catalyzed hydrosilylation of alkynes. The cationic complex [Cp⁎Ru(MeCN)3] PF6 catalyzed the hydrosilylation of numerous alkynes:31,34 terminal alkynes afforded the α-vinylsilane product via trans-addition; the same complex also gave trans-addition with internal alkynes. Propargylic alcohols and α,β-alkynyl carbonyl compounds gave regioselective vinylsilane formation. An order of reactivity for the silanes was reported as SiEt3≈SiMe2Cl4SiMe2OR≈Si (OR)34SiMe2Bn≈SiMe2Ph. The authors have performed a theoretical study, using density functional calculations – the B3LYP method with 6–31 G⁎ basis set (for C, H, N, and O atoms) and Lanl2dz basis set and ECP for Si and Ru atoms – to understand the anti-addition stereochemistry and Markovnikov regiochemistry of the hydrosilylation of terminal alkynes and the endo-dig product of intramolecular hydrosilylation of homopropargylic alcohols, all catalyzed by the same [Cp⁎Ru(MeCN)3]PF6 catalyst.49 Markovnikov alkyne hydrosilylation is catalyzed by the same ruthenium complexes.31 The same group have also utilized the vinylsilanes produced in the reaction as a masked form of α-hydroxyketones. Thus internal alkynes bearing either propargylic, homopropargylic, or bishomopropargylic hydroxyl groups undergo regioselective hydrosilylation catalyzed by [Cp⁎Ru(MeCN)3] PF6 to give vinylsilanes which may subsequently be oxidized to a ketone.35 This masking approach has also been used in ‘synthetic stitching with silicon’: geminal alkylation-hydroxylation of alkynyl carbonyl compounds to give β-carbonyl-substituted tertiary alcohols.33 The catalyst produced regioselective alkyne hydrosilylation by a trans-addition process, followed by one-pot C–C bond formation by Si→C migration and subsequent silane oxidation. The same catalyst was used by Trost in a late-stage Ru-catalyzed hydrosilylation as part of a formal synthesis of aspergillide B.50 Finally, Trost has also investigated the use of the same catalyst in the intramolecular endo-dig hydrosilylation of alkynes (Scheme 3).32 Cox has shown that Grubbs' first generation Ru metathesis catalyst efficiently catalyzes the hydrosilylation of terminal alkynes.51 The product selectivity depended on both reaction concentration and the silane employed: use of Et3SiH with 1-hexyne gave predominantly the β-(Z)-stereoisomer, whereas the bulkier 3,3-dimethylbut-1-yne have the β-(E)-product and propargyl alcohol gave the α-stereoisomer (cf (EtO)3SiH, which gave in all cases the α-stereoisomer as the major product). Two complementary Rh catalysts have been reported for the hydrosilylation of phenylacetylene.52 In the hydrosilylation reaction of triethylsilane, triethoxysilane, or triphenylsilane with phenylacetylene, [Cp⁎RhCl2]2 was found to give predominantly anti-addition to the β-Z-isomer, whereas [Cp⁎Rh(BINAP)](SbF6)2 added in the syn manner to form the β-E-isomer. An inorganic-organic hybrid mesoporous material incorporating organoruthenium complexes within its organosilica framework (HMM-phRuCpPF6) has been reported as a unique heterogenous catalyst for hydrosilylation, and in the case of 1-hexyne produced α-vinylsilane at elevated temperatures.53 With the exception of the cationic [Cp⁎Ru(MeCN)3] PF6 catalyst and also Cp⁎RuH(PPh3), which both afford selectively α-vinylsilanes, there is only a handful of other examples of methods for the preparation of the Markovnikov product with Ru catalysis. Cossy has developed several ruthenium-alkylidene complexes for just this outcome.54 Oro has reported trans-additions of silanes to 1-alkynes by ruthenium complexes and investigated the role of in situ formed polynuclear aggregates.55 Faller has reported various Cp⁎Rh complexes, including [Cp⁎RhCl2]2 and [Cp⁎Rh(BINAP)](SbF6)2 as effective catalysts for the hydrosilylation of phenylacetylene with triethylsilane, triethoxysilane, and triphenylsilane.52 The former was selective for the β-(Z)-isomer, whereas the latter gave the β-(E) isomer (Scheme 4).

OH

1. 3 equivalents (Me2HSi)2NH, neat, 50 °C

O

Si

2. cat. [Cp*Ru(MeCN)3]PF6, DCM, 0 °C 79% Scheme 3

Ph

SiR3

HSiR3

HSiR3

Ph

Ph [Cp*RhCl2]2 -Z/cis Scheme 4

[Cp*Rh(BINAP)]2+

SiR3 -E/trans

968

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

The RhCl(PPh3)3-catalyzed hydrosilylation of phenylacetylene and styrene with phenylsilanes (Ph2SiH2 and PhSiH3) has been reported by Osakada and proceeds in THF in high yields, giving primarily PhSiH2(CH ¼ CHPh) from phenylacetylene and Ph2SiH (CH2CH2Ph) (from styrene).56 A (Rh(COD)Cl)2 catalyst has given high stereoselectivity in the hydrosilylation of alk-1-ynes giving either the E- or the Z-vinylsilane depending on the conditions. Using the catalyst in ethanol or DMF as a solvent gave Z-selective reactions, whereas the same catalyst with additional PPh3 and using acetonitrile as a solvent gave E-selective reactions.57 A followup paper from the same group demonstrated that E-vinylsilanes could be obtained with high selectivity using Rh(COD)2BF4/ 2PPh3-catalyzed hydrosilylation of 1-alkynes and alkenes with triethylsilane.58 Oshima has developed a rhodium-catalyzed hydrosilylation of alkynes in an aqueous micellar system, combining [RhCl(nbd)]2 and sodium dodecylsulfate (SDS). Although the rhodium chloride dimer is insoluble in water, in combination with SDS formed a homogenous solution. Addition of dppp favored (E)-selective hydrosilylation while adding NaI gave predominantly the (Z)-product.59 A number of reports have started to emerge involving rhodium complexes with N-heterocyclic carbenes. For example, Jimenez has reported a series of alkylammonium-imidazolium chloride salts as precursors for a library of rhodium(I) complexes with hemilabile character by varying the substituent on the heterocyclic ring and the length of the linker with the dimethylamino moiety. The rhodium complexes were good hydrosilylation catalysts for terminal alkynes using HSiMe2Ph. Excellent selectivities were found in the β-(Z)-vinylsilane with 1-hexyne and β-(E) and α-bis(silyl)alkene isomers with trimethylsilylacetylene.29 Rhodium complexes of PCNHCP have been prepared from the silver transfer reagent [Ag3(PCNHCP)2Cl]Cl2 and [Rh(COD)Cl]2; these novel complexes catalyzed the hydrosilylation of alkynes and showed excellent selectivity for (E)-alkenylsilanes.60 Mazzoni has also repeated an in-depth study of N-heterocyclic carbene-amide rhodium(I) complexes.61 Their catalysts led only to the formation of the β-(E)-vinylsilane and α-bis(silyl)alkene isomers. Rhodium(III) complexes with monoanionic C,C,C-tridentate dicarbene ligands activate Si–H bonds and also further catalyze the hydrolysis of hydrosilanes to form silanols and siloxanes; in the presence of alkenes rapid hydrosilylation occurred, whereas carbonyl groups were unaffected.62 Fluorinated N-heterocyclic carbene rhodium(I) complexes have been used in the hydrosilylation of propargylic alcohols.63 Although strictly not hydrosilylation, a number of related and relevant silylformylation reactions of alkynes have been reported. Ojima has published a detailed investigation of the Rh2Co2(CO)12-catalyzed silylformylation of terminal alkynes.64,65 Solvated rhodium atoms – prepared by metal vapor synthesis technique – have been shown to promote the silylformylation reaction of terminal alkynes with excellent chemoselectivity (for silylformylation rather than hydrosilylation) and giving exclusively Z-silylalkenals (Scheme 5).66 The tetracationic complex [Rh2(MeCN)2(Naft)4](BF4)4 (where Naft ¼ μ−1,8-naphthyridine) is an efficient catalyst for the silylformylation of internal and functionalized alkynes.67 Matsuda has reported an efficient silylformylation of alkynes (internal and terminal) catalyzed by Rh4(CO)1268 and has also published detailed mechanistic studies on the rhodium-catalyzed silylformylation reaction of alkynes.69

Me2PhSiH

Rh/mesitylene cocondensate

n-Bu

H

CO (10 bar)

OHC

SiMe2Ph

+ n-Bu

Scheme 5

Many platinum catalysts have been developed for hydrosilylation reactions of alkynes, including: platinum on titania;70 platinum complexes synthesized with polydentate N-heterocyclic carbenes for hydrosilylation phenylacetylene and p-tolylacetylene;71 a tetraammineplatinum(II) chloride catalyst in polyethylene glycol medium supported on silica gel for vapor-phase hydrosilylation of acetylene with trichlorosilane or trimethoxysilane;46 PtCl2/XPhos for the hydrosilylation of propargylic alcohols;72 a platinum/ mesitylene solution (i.e., solvated Pt atoms) for the stereo- and regioselective functionalization of propargylic alcohols via intramolecular hydrosilylation;73 platina-β-diketones as catalysts for the hydrosilylation of alkenes and alkynes;74 platinum on titania;70 the Karstedt catalyst;75 Pt(II) mono- and biscarbene complexes formed by reaction of imidazolium; and benzimidazolium halides with PtBr2 and/or PtI2.76 Unusually, the α-addition products are greatly favored (rather than the trans-β-addition) in the chloroplatinic acid-catalyzed hydrosilylation of terminal acetylenes catalyzed by (η5-C5H5)Fe(CO)2SiPh2H when the reaction is performed in the presence of CO.77 Platinum on carbon has been shown to be a cheap and efficient catalyst for the hydrosilylation of alkynes under mild conditions. High-resolution electron microscopy showed that colloidal Pt is formed during the reaction. Excellent yields were obtained, with chlorosilanes usually producing one vinylsilane, whereas alkoxysilanes and alkylsilanes usually yielded a mixture of two or more isomeric vinylsilanes.78 Bulky phosphabarrelene ligands act as very efficient ligands in the Pt(0)-catalyzed hydrosilylation of terminal alkynes, using [(COD)PtCl2] as the Pt source and give excellent β(E) selectivity.79 Markó has reported a highly β-(E)-selective hydrosilylation of both terminal and internal alkynes catalyzed by a novel (IPr)Pt (AE) diene complex X (IPr ¼ bis(2,6-diisopropylphenyl)imidazo-2-ylidene; AE ¼ allyl ether) (Scheme 6).80 They have also reported the same reaction catalyzed by N-heterocyclic carbene platinum(0) complexes, including [Pt(N,N′-dicyclohexylimidazol2-ylidene)(η2-dimethylacetylenedicarboxylate)2].81 A more unusual example is the photoactivated hydrosilylation of alkynes, involving irradiation at λ ¼ 350 nm and a platinum (II) bis(acetylacetonato) catalyst.9 Park has demonstrated that palladium nitrate catalyzes the anti-hydrosilylation reaction of terminal alkynes to give predominantly the thermodynamically less stable cis isomers, together with low quantities of dialkynylated silanes.82 The palladium-catalyzed

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

969

Catalyst = Catalyst (0.1 to 0.05 mol%) R2

R1

+ R3SiH

SiR3 +

60 °C THF, 30 min

R1

O

SiR3

R2

N

R2

R1

N

Pt

Selectivity up to 100:1 Scheme 6

regio- and stereoselective hydrosilylation of electron-deficient alkynes has been described by Hosoya.83 A variety of silyl groups were introduced to the alkynes bearing a single electron-withdrawing group using Pd(dba)2/PCy3 (Scheme 7). The product αsilylalkenes were utilized in both Hiyama couplings (with retention of configuration) and stereoinverting iododesilylation/ Suzuki–Miyaura coupling reactions. The electron-rich Pd(0) complex Pd2(dba)3 CHCl3-tricyclohexylphosphine catalyzes a highly efficient hydrosilylation of alkynes at room temperature with Ph3SiH or Ph2MeSiH in the absence of a solvent. The regioselectivity was higher than that with the corresponding conventional Pt(0)-catalyzed hydrosilylation.84 Palladium(0) complexes obtained in situ from ½[(η3-C3H5)PdCl]2 and P(OAr)3 catalyze the hydrosilation of 1-alkynes with HSiCl3 at room temperature giving 1,3dienylsilane derivatives in which alkyne dimerization accompanies hydrosilation. The head-to-tail adduct, R–CH¼ CH–C(R) ¼ CHSiCl3 predominates over other regioisomers.85 Tomooka has employed a dimethylvinylsilyl (DMVS) directing group – a substructure of the Karstedt catalyst – in the Pt(0)-catalyzed hydrosilylation of unsymmetrical alkynes to afford a single silylalkene regioisomer from proparglyic and homopropargylic alcohols.86 The reaction pathway was studied by density functional theory (DFT). The E-silylalkenes produced are utilized in the synthesis of multisubstituted alkenes and oxy-functionalized compounds. The principle of Tomooka's approach is presented in Scheme 8.

EWG

R

+

5 mol% Pd(dba)2 10 mol% PCy3

H

Si

R EWG

Toluene, r.t.

Si

PhMe2SiH or (EtO)3SiH EWG = EtO(CO), MeO(CO), Me(CO), Ph(CO), CHO, Me2N(CO), p-Tol(SO2) R = Me, Ph, TMS, OTBS, alkyl, (CH2)3C(CH) Time = 0.5−16 h Yield range: 42−99% Scheme 7

R1

SiR3

R2

R1 Introduction of directing group (DG)

R1

R2

DG =

Si DMVS group

DG R2

DG

SiR 3 R1

SiR3

>>

Distal product

i-Pr3Si

HO R

HO

R2

R1

R2

Proximal product

Scheme 8

R2

Removal of DG

R3SiH Pt(0)

DG

R1

SiR3

+

Sii-Pr3 R

HO

R

Si O Si Karstedt catalyst

Pt (0)

970

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

Mixed metals complexes have also been employed in alkyne hydrosilylation reactions, including cobalt-rhodium Co2Rh2(CO)12 and Co3Rh(CO)12 (both giving cis-1-triethylsilyl-1-hexene as the major product from the hydrosilylation of 1-hexyne with triethylsilane);87 a homologous series of catalysts of general formula MPt2(CO)5(PPh3)2(PhC2Ph) where M¼ Fe, Ru, or Os has been investigated mechanistically for its ability to catalyze the hydrosilylation of diphenylacetylene with triethylsilane.88 The preparation and reactions of pentafluorophenyldimethylvinylsilanes have been developed, providing a convenient and robust method for the diversity-orientated synthesis of E-, Z-, and α-disubstituted alkenes, all starting from terminal alkynes. The pentafluorophenyldimethylvinylsilanes were shown to be an attractive alternative to existing masked silanols89 and have been utilized in cross-coupling reactions.90 Ab initio Car–Parrinello simulations have been employed to help determine the mechanism of grafting of phenylacetylene on the crystalline, hydrogenated surfaces of silicon catalyzed by the Lewis acid aluminum trichloride.91 A unique white-light promoted hydrosilylation reaction of alkenes and terminal alkynes has been studied in detail, using photoluminescent nanocrystalline (porous) silicon.92 It is claimed to be one of the safest methods for hydrosilylation. Features of the reaction included no significant loss of the photoemissive qualities of the material and its quenching both by charge-transfer and energy-transfer complexes (but not by radical spin traps).

8.25.2.2.3

Hydrosilylation of disubstituted alkynes

The overall transformation of alkyne hydration has been achieved by Floreancig by combining intramolecular alkyne silylation using Pt(DVDS) (DVDS ¼ divinyl dimethyldisoloxane) and Tamao oxidation (Scheme 9).93

SiMe3

SiMe3 Bu4NF, KF, KHCO3, H2O2, THF, DMF 40 °C

Pt(DVDS), THF

O OEt

OR

H i O Si Pr2

O

O

O

O OEt

57%

OH

OEt O

O

R = iPr2SiH Scheme 9

The stereoselective synthesis of α-silylenones has been achieved through PtCl2 catalysis.94 α-Hydroxypropargylsilanes react, via alkyne activation, to give Z-silylenones through a highly selective silicon-migration process, whereas the complementary E-silylenones were obtained via regioselective hydrosilylation of the appropriate ynone precursor.94 The hydrosilylation of internal alkynes has also been studied under the same catalytic conditions, with the regioselectivity being governed primarily by electronic effects (Scheme 10).94,95 Molander has reported that the organoyttrium complex Cp⁎2YCH3.THF is an effective precatalyst for the hydrosilylation of internal alkynes.39 Symmetrical alkynes gave the single cis-addition hydrosilylation product, whereas nonsymmetrical alkynes gave the silane-addition product to the least hindered carbon of the alkyne. The reaction tolerated a wide range of functional groups elsewhere in the alkyne (halides, amines, protected alcohols, and olefins). The same group has subsequently shown that the catalyst may be employed for the selective sequential cyclization/silylation of 1,6- and 1,7-enynes (Scheme 11).96,97 Nitrogencontaining enynes have been cyclized to azabicycles using the same catalyst or the lutetium equivalent in high yields and good-toexcellent diastereoselectivity.98 Roesky has reported bis(phosphinimino)methanide rare earth (Y, La, Sm, Ho, Lu) amides catalyze hydrosilylation and sequential hydroamination/hydrosilylation reactions of both alkenes and alkynes.99 A highly efficient and broad substrate alkyne hydrosilylation reaction has been reported involving Ni(0) complexes of N-heterocyclic carbenes.100 The variable regioselectivity of the process depended on the structure of the alkyne, silane, and N-heterocyclic carbene ligand. Berding has also developed nickel(II) dihalide complexes with small monodentate N-heterocyclic carbene ligands as catalysts for hydrosilylation reactions of internal alkynes; the nickel(0) active species being generated from the complex using diethylzinc.101 Silicon (II) hydride-stabilized Ni(CO)3 has also been reported as efficient for the hydrosilylation of diaryl alkynes (Scheme 12).102 An efficient end-capping method for the preparation of [2]rotaxanes, using acetylene–dicobalt hexacarbonyl complexation has been reported, along with their subsequent transformation into a series of vinylsilanes through hydrosilylation.103

8.25.2.2.4

Applications of alkyne hydrosilylation

Furstner has reported a highly chemo and stereoselective two-step reduction of cycloalkynes to (E)-cycloalkenes via trans-selective hydrosilylation followed by a AgF-mediated desilylation (Scheme 13).104

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

971

O

R1 HO R3Me2Si

PtCl2 (5 mol%)

R2

R2

PhMe (0.1 M), 80 °C

R1 SiMe2R3

R1 = CH2CH2Ph, n-Hept, t-Bu, homoallyl, CH2CH2CH2OTBS, CH2CH2CH2OAc, CH2CH2CH2CO2NHPh R2 = n-Bu, Ph, CH2OTBS, CH2OPMB, CH2OTHP R3 = Me, Ph Yield = 76 to 99% Z:E = 10:1 to > 19:1

PtCl2 (5 mol%) Et3SiH or BnMe2SiH (1.1 to 1.2 equivalents)

O R1 R2

R2

O R1

PhMe (0.15−0.25 M) 23 °C

3

SiR

R1 = CH2CH2Ph, t-Bu, CH2CH2CH2OTBS R2 = n-Bu R3 = Et, Me2Bn Yield = 65−99%; Z:E = >19:1 PtCl2 (5 mol%) Et3SiH or BnMe2SiH (1.1−1.2 equivalents)

O Ph OTBS

PhMe (0.15−0.25 M) 23 °C; Yield = 87%

TBSO

TBSO

O Ph +

Et3Si

O Ph

SiEt3 -isomer : -isomer 2:1

Scheme 10

Various (hex-5-ynyl)silanes have been prepared and undergo intramolecular hydrosilylation to give the corresponding 2-methylidene-1-silcyclohexane (Scheme 14).105 Welker has reported the synthesis of enynyloxy dimethyl and diisopropylsilanes and their conversion into siloxacyclopentenes containing a 1,3-diene moiety via intramolecular hydrosilylation reactions of the alkyne. The products underwent facile Diels–Alder reaction (Scheme 15).106 The formal addition of an aryl-H or alkenyl-H bond across a terminal alkyne has been achieved by the combination of platinum-catalyzed hydrosilylation followed by palladium-catalyzed cross-coupling. The catalytic system of t-Bu3P-Pt(DVDS) in combination with tetramethyldisiloxane gave the highest yields and best regio- and stereoselectivity (Scheme 16).107 A hydrosilylative cross-coupling reaction of alkynes with several alkenes is catalyzed by cationic palladium complexes without or with an added triphenylphosphine ligand and using HSiCl3.108 Functionalized 1,6-diynes undergo facile cyclization/ hydrosilylation catalyzed by cationic platinum complexes containing bidentate nitrogen ligands (Scheme 17).109 The palladium complex, [(η3-C3H5)Pd(cod)]+[PF6]−, catalyzes the hydrosilylation of 1-dodecene-6,11-diyne and 1-tridecene-6,11-diyne, and their 9-oxo congeners, with HSiCl3 to form regioisomeric cyclization products.110 The use of rhodium(I) iodide complexes in the hydrosilylation of terminal alkynes at differential temperatures affords (Z)silanes (room temperature) or (E)-silanes (60 °C). The stereodivergent hydrosilylations have been applied to the polyaddition of bifunctional alkynes and silanes to generate silicon-containing polymers – poly(aryleneethylenesilylenes)s.111 RhI(PPh3)3 has also been used as a polymerization catalyst to effect the hydrosilylation polymerization of D-(−)-p-hydroxyphenylglycine-derived diethynyl monomers with dihydrosilanes to give novel optically active poly(silylenevinylenephenyleneethynylene)s.112 Rh(I) catalysts have also been immobilized on polyamide supports, but are still able to catalyze the hydrosilylation of alkenes, dienes, and alkynes.113 The physical characteristics of the immobilized Rh(I) catalyst were studied by WAXS, SAXS, DSC, the nitrogen BET adsorption method, ISEC and pycnometry: catalyst activity was decreased with increasing polymer crystallinity. The presence of 2,5- and 2,6-pyridines in the polymer also affected the cis/trans selectivity of the hydrosilylation. Alkyne polymers obtained by radical polymerization of conjugated enynes (CH2 ¼ CH–C≡C–R where R¼ Ph or nBu) have been modified by various process, including radical addition of thiol fragments, hydrosilylation, and reduction by hydroalumination to give polymers bearing alkenyl sulfide, alkenylsilane, and alkene moieties.114 Bis(dichlorosilyl)methane 3 undergoes a double hydrosilylation and a dehydrogenative double silylation on reaction with alkynes such as acetylene and activated phenyl-substituted acetylenes in the presence of Speier's catalyst to give 1,1,3,3-tetrachloro1,3-disilacyclopentanes and 1,1,3,3-tetrachloro-1,3-disilacyclopen-4-enes (Scheme 18).115

972

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

R

R1

R

Cp*2YCH3. THF +

C6H12

PhH2Si

R

PhH2Si

R1

R1

R = cyclohexyl; R1 = OTBDMS, OTIPS, OTr, isoindoline, Me, Et, CH2OMe, CH2OTBDMS; Yield = 64−93%; E:Z = >50:1 to 6.5:1 R = TBDMSOCHCH3; R1 = OTr; Yield = 77% R = (CH3)2CO2(CH2)2CH; R1 = OTr; Yield = 88%; E:Z = 35:1

RL H

RS Cp*2YMe. THF

SiH2Ph

PhSiH3

RL

Rs

“Cp*2YH”

PhSiH3

RL

RL = large group RS = small group

RS

H

RL

Rs

YCp*2 H YCp*2

Scheme 11

R2

Ar N Si N Ar

H

Ar N

R1

Si N

Ni(CO)3

Ar

R1 R2 Ni(CO)3

Ar = 2, 6-i-Pr2C6H3 R1 and R2 = Ph or p-Tol Scheme 12

R1

(EtO)3SiH [Cp*Ru(MeCN)3]PF6(1 mol%) CH2Cl2, r.t.

R1

Si(OEt)3

H

R2

THF/aqueous MeOH r.t.

R2 e.g. Si(OEt)3

Scheme 13

R1 AgF (2 equivalents) R2

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

Me

R H Si

R Si Me

H2PtCl6 (8×10−3 mol%) Cyclohexane, reflux

R = alkyl, Ph, allyl 18−66% Scheme 14

1. i) DMAP, NEt3; ii) i-Pr2Si(H)Cl; 0 °C o/n OH

H

Si O

2. KOtBu, THF, r.t. 1 hr 65% (2 steps)

O THF 90 °C 24 hr 46% (endo) + 40% (exo)

N Ph O

H O H

i-Pr i-Pr

Si O

N Ph H O

endo Scheme 15

H R2

[HMe2Si]2O

H

R2

t-Bu3P-Pt(DVDS)

SiMe2

O 2

R1I Bu4N+F− (2.0 equivalents)

H R1

R2

Pd(dba)2 (5 mol%) THF, r.t.

H

R1= 1-naphthyl, 4-(CH3CO)C6H4, 4-(CH3O)C6H4, 3-(NO2)C6H4, 3-(CH3)C6H4, 2-(CH3OCO)C6H4, 2-(CH3O)C6H4, (E)-ICH=CHC5H11, (E)-BrCH=CHC6H5; R2 = n-C5H11; Yield = 67 to 94%; E:Z = 91.4:8.6 to 99.4:0.6 R1 = 4-(CH3CO)C6H4 or 4-(CH3O)C6H4; R2 = C6H5, HO(CH2)3, C6H5C(OH)(CH3), CH2 = CHCH2O(CH2)3; Yield = 72 to 89%; Ratio: > 99% Scheme 16

(phen)PtMe2, B(C6F5)3 (5 mol%)

MeO2C MeO2C

MeO2C

SiEt3

MeO2C

HSiEt3 Toluene 100 °C

Scheme 17

Cl2HSi

SiHCl2 3

Scheme 18

R1

R2

R1, R2 = H, Ph

Pt

Cl2Si R1

SiCl2 R2

45−98%

Cl2Si

SiCl2

R1 <10%

R2

973

974

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

The stereocontrolled synthesis of poly(phenylenevinelene)s (PPVs) with (E)- and (Z)-vinyl units has been achieved using ruthenium-catalyzed hydrosilylation of p-diethynylbeneze; RuHCl(CO)(PPh3)3 was found to give the (E,E) product with HSiMe2Ar and p-diethynylbenzene, whereas RuCl2(CO)(PiPr3)2 afforded the (Z,Z) product.116 RuHCl(CO)(PPh3)3 and RhCl(CO)(PPh3)3 complexes both catalyze the hydrosilylation reaction of a terminal alkyne moiety in several pseudorotaxanes at ambient temperature.117 This has proven to be a powerful end-capping method for pseudorotaxanes having an alkyne at the axle terminal, and the reaction proceeded in high yields and excellent regio- and stereoselectivities (Scheme 19).

Where

is:

PF6

N H2

+

O

O

R = H, CO2Et, CH2OH, Br

O R

O

O

O

O

PhMe2SiH (2.0 equivalents) Catalyst 5 mol% CDCl3, r.t.

O

O

or PF6

N H2

O O

 

O

O

O

O

O

SiPhMe2

Catalyst = H2PtCl2.nH2O, RuHCl(CO)(PPh3)3, RhCl(PPh3) Yield = 18 to 88% -trans/-cis/ = 93:2:5 to 99:1:0

O

O

Scheme 19

Dialkylsilanes have been used as silylene synthetic equivalents in a Ni(0)-catalyzed multicomponent oxidative cyclocondensation cyclization with an aldehyde and an alkyne to form silacycles (Scheme 20).118

O R1

R3 H

+ R2

+

Et2SiH2

Et Et O Si

Ni(COD)2 IMes.HCl, t-BuOK, Al(O-i-Pr)3

R1

R3

R2

R1 =

Ph, Cy, n-Pr, n-pentCH(OTBS) R2 = Me, Et, H R3 = Ph, Et, n-pent, n-hex, CH(Me)CH2 Yield = 53 to 85%, regioselectivity 62:38 to 98:2 Scheme 20

Roesky has reported bis(phosphinimino)methanide rare earth (Y, La, Sm, Ho, Lu) amides catalyze hydrosilylation and sequential hydroamination/hydrosilylation reactions of both alkenes and alkynes.99

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

975

Hydrosilylation reactions have been widely used to secure a variety of molecules on to silicon surfaces, to investigate certain properties or reactions at the other end of a carbon chain, once attached to the surface. For example, the relative reactivity of alkynes and alkenes on silicon(100) surfaces has been assessed, by preparing monolayers of each via hydrosilylation.119 X-ray photoelectron spectroscopy (XPS) and electrochemical studies showed that the alkynes were more reactive than the alkenes, in the ratio c. 1.7–2.0:1 at 120 °C, although the ratio was lowered as the temperature decreased. Another study has shown that functionalization of the surface of porous silicon with organic monolayers can have important effects on the electrochemiluminescence (ECL) characteristics (Scheme 21).120 Surfaces could be terminated with alkyne, alkene, and alkyl functionalities through cathodic electrografting, Lewis acid-mediated hydrosilylation, and anodic electrografting. R

Si

R H Si

Si

Si

EtAlCl2 or h R

R

R

R

R R

Si

H Si

Si

R

Si

−10.4 mA/cm−2 cathodic electrografting (CEG)

H Si

R

R

H Si

Si H

Si H

Si Si

+ 10.4 mA/cm−2 anodic electrografting (CEG)

Si Si

Scheme 21

Despite the densest monolayers preventing good electrical contact between electrolyte and the nanocrystallites, the surface was protected from degradation, leading to extended lifetimes but low light emission. The nanopatterning of alkynes on hydrogenterminated silicon surfaces has been reported by scanning probe-induced cathodic electrografting.121 The copper-catalyzed azidealkyne ‘click’ cycloaddition reaction has been utilized on many occasions to functionalize monolayers on Si(100) surfaces122 (which themselves were prepared via hydrosilylation). For example, a ‘click’ reaction was utilized to covalently confine substituted ferrocene derivatives on passivated silicon(100) surfaces (Scheme 22).123 The electronic communication between the ferrocene

Fe

R N N

N

N

N N RN3 =

Fe

Method A, B or C N3

Surface

Si (100)

Method A: i) 10mM RN3, 1 mol% CuI-P(OEt)3, dry PhMe, reflux, 12 h ii) 0.05% EDTA, r.t., 24 h Method B: i) 10mM RN3,1 mol% CuI, dry PhMe, reflux, 12 h ii) 0.05% EDTA, r.t., 24 h Method C: i) 10mM RN3, 1 mol% CuSO4. 5H2O, Na ascorbate, H2O/i-PrOH 1:2, r.t., 24 h ii) 0.05% EDTA, r.t., 24 h Scheme 22

976

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

center and semiconductor surface was examined by cyclic voltammetry and found to be in agreement with that expected for a redox interface. The same group has reported the synthesis of functionalized oligoethylene glycol molecules, with an azido group at one end and an ionizable group at the other, and their attachment on to alkyne-terminated silicon(100) surfaces using click chemistry. The surfaces were characterized using XPS and water contact angle goniometry. The surfaces were found to possess antifouling properties.124 A similar approach allowed the differential functionalization of the internal and external surfaces of mesoporous materials, for biosensing applications,125 and in the preparation of ‘clickable’ monolayers grown from α,ω-alkenynes, with the alkyne-terminus protected with a trimethylgermanyl (TMG) group. After degermylation, the alkynes readily underwent click reactions with various azides to tag various biological molecules (e.g., mannose, biotin) on to the surface. The mannosetagged material was used to capture living targets (E. coli) on to the surface. The regio- and stereoselective hydrosilylation reactions of ferrocenylalkyne-dicobalthexacarbonyl complexes with either HSiEt3 or dendrimer Si[CH2CH2CH2Si(CH3)2H]4 have been reported by Delgado and Alonso and generated a range of ferrocenylvinylsilanes and ferrocenylvinyl-functionalized carbosilane dendrimers which were studied by cyclic voltammetry (Scheme 23).126 Porphyrins – such as nickel(II) β-azido-meso-tetraphenylporphyrin – have been anchored on to a Si(100) surface at the β-pyrrolic position and utilizing a linker with two terminal alkynes by the sequence: (1) hydrosilylation of a C≡C bond of the linker by surface Si–H groups and (2) 1,3-Huisgen cycloaddition between the alkyne-terminated silicon surface and the azidoporphyrin derivative.127,128

Fe H Fe Si

Si

Si

Si

Si Scheme 23

8.25.2.3

Hydrosilylation of Carbon–Carbon Double Bonds

A number of excellent reviews have appeared covering alkene hydrosilylation reactions.16,17 Marciniec has published a detailed review on all aspects of transition metal-catalyzed alkene silylation, covering topics including silylation of alkenes by hydrosilanes, silylation of alkenes by vinylsilanes, silylative couplings and competitive silylation of alkenes with vinylsilanes and hydrosilanes.129 Full mechanistic discussions are included through the review. Anderson has published a comprehensive review on the synthesis of vinylsilanes, including many examples involving hydrosilylation reactions.19 The same group has also reported the one-step preparation of functionalized E-vinylsilanes from aldehydes via a chromium(III)-mediated olefination, employing dihalomethylsilane reagents.130 A review of the challenges in late transition metal-catalyzed olefin hydrosilylation reactions, from an industrial perspective, has been published,131 which has a detailed review of iron-catalyzed hydrosilylation reactions.18 A number of platinum-based catalysts have been developed for the hydrosilylation of alkenes, including platina-β-diketones;74 expanded ring N-heterocyclic carbene complexes of zero-valent platinum divinyltetramethyldisiloxane;27 platinum supported on styrene-divinylbenzene copolymer for the hydrosilylation of terminal n-alkenes and allyl chloride;132 several carboxylated polyethylene glycols have been used as promoters for the platinum-catalyzed hydrosilylation of alkenes, giving the β-adduct as the major product and with polyethylene glycol maleic acid monoester being particularly studied;133 polymeric monolith supported Pt-nanoparticles have been used as ligand-free catalysts for terminal olefin hydrosilylation under both batch and continuous flow conditions.134 A new concept for chirality transfer from an optically active ligand of the catalyst to prochiral olefins has been discussed by Brunner for the asymmetric hydrogenation of alkenes, and extended to the development of new catalysts for enantioselective hydrosilylation of alkenes.135 Rather than focussing on the metal, Gibson has published a structure-activity survey of monophosphane ligands for the asymmetric palladium-catalyzed hydrosilylation reaction of alkenes, in an attempt to assess the role of secondary interactions on catalyst activity and selectivity.136 In an attempt to move away from precious metal catalysts, Chirik has published extensively on the use of iron catalysts for hydrosilylation reactions,137,28,138–142 in particular the iron-catalyzed selective anti-Markovnikov addition of sterically hindered tertiary silanes to alkenes under mild conditions.141

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

977

A rare metal-free N-heterocyclic carbene catalyst has been reported for the hydrosilylation of styryl and propargylic alcohols with dihydrosilanes.143

8.25.2.3.1

Hydrosilylation of monosubstituted alkenes

Yi has published a short review/summary of his own group's work on region- and stereoselective hydrosilylation and oxidative silylation of alkenes and alkynes.21 Treatment of terminal alkynes with HSiEt3 in the presence of (PCy3)2(CO)RuHCl gave the cisalkenes, whereas dehydrosilylation of α-olefins under the same conditions gave the trans-vinylsilane. The RhCl(PPh3)3-catalyzed hydrosilylation of styrene and phenylacetylene with phenylsilanes (Ph2SiH2 and PhSiH3) has been reported by Osakada and proceeds in THF in high yields, giving primarily Ph2SiH(CH2CH2Ph) (from styrene) and PhSiH2(CH¼ CHPh) from phenylacetylene.56 The reactivity of the Rh(I) complex Rh(CF3COO)(NHC)(COD) (where NHC¼ 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) in the hydrosilylation of 1-alkenes, alkynes, and α,β-unsaturated compounds has been thoroughly investigated, with TONs up to 1000 reached.144 A poly(styrene-codivinylbenzene) supported version of the catalyst is also reported. Widenhoefer has reported the cyclization/hydrosilylation of 1,6- and 1,7-dienes catalyzed by cationic palladium complexes. For example, the reaction of dimethyl diallylmalonate with triethylsilane with the catalyst 4 gave the trans-silylated cyclopentane in 93% after 5 min (Scheme 24).145–151 This has been developed into an asymmetric version using optically active palladium bisoxazoline and pyridine-oxazoline complexes.147 CF3 Me Pd

B OEt2 CF3

4

MeO2C MeO2C

4 MeO2C

(5 mol%) HSiEt3 CH2Cl2, 0 °C

SiEt3

MeO2C

CH3

Scheme 24

The commercial catalyst [Ir(OMe)(COD)]2 and 4,4-di-tert-2,2-bipyridine catalyze the Z-selective dehydrative silylation of terminal alkenes (but not 1,2-disubstituted alkenes) with triethylsilane or benzyldimethylsilane in THF at 40 °C.152 A rare metal-free N-heterocyclic carbene catalyst has been reported for the hydrosilylation of styryl and propargylic alcohols with dihydrosilanes.143 In conjunction with TBAF, this gave a highly efficient method for the reduction of alkenes (Scheme 25). Li has also reported the use of rhodium N-heterocyclic carbene complexes for the hydrosilylation of alkenes in an ionic liquid medium BMimPF6.153 Strassner has investigated the use of platinum(II)-bis-(N-heterocyclic carbene) complexes in hydrosilylation reactions of alkenes and found that they favor the β-product.154 Pleasingly, the catalyst 5 did not decompose during the reaction to platinum black, offering an important advantage over the Karstedt catalyst. OMe OH Ph

dipp N

N

N dipp

H2SiPh2 DMF, r.t. then TBAF 99% conversion, 82% yield

OH Ph

N

Cl Pt Cl

N N

OMe 5

Scheme 25

A silica-supported chitosan-platinum complex has been prepared and characterized by ICP-AES, FT-IR, and XPS, and found to show high catalytic activity in the hydrosilylation of allyl glycidyl ether with triethoxysilane.155 The hydrosilylation of n-alkenes and allyl chloride over platinum supported on styrene-divinylbenzene copolymer has been reported.132 A range of alkyllanthanum biphenolate complexes have been prepared and screened as catalysts. One, [La{(R)-Biphen}]2 and its THF adduct [La{(R)-Biphen}{CH(SiMe3)2}(THF)3] exhibited good catalytic activity and diastereoselectivity in the hydrosilylation of styrene, 1-hexene, and norbornene.156

8.25.2.3.2

Hydrosilylation of disubstituted alkenes

Roesky has reported bis(phosphinimino)methanide rare earth (Y, La, Sm, Ho, Lu) amides catalyze hydrosilylation and sequential hydroamination/hydrosilylation reactions of both alkenes and alkynes.99 A rare catalyst-free thermal hydrosilylation of

978

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

cycloalkenes has been reported, employing trichlorosilane with cyclopentene, cyclohexene, cycloheptene, or cyclooctene to give cycloalkyltrichlorosilanes.157

8.25.2.4

Hydrosilylation of Conjugated and Related Systems

Le Gendre has prepared an open-bent titanocene complex [Me2C(C5H4)2TiMe2] which was demonstrated to be efficient for the hydrosilylation of a variety of substrates such as disubstituted dienes, including 2,3-dimethylbutadiene, activated alkenes, and acetylenes.158 The silaboration of 1,3-enynes catalyzed by group 10 metal complexes affords 1,3-dienes with vinylborane and vinylsilane functions, or 1,2-dienes with allylborane and vinylsilane functions, the exact nature of the product formed being determined by the size of the alkyne substituent (Scheme 26).159 R

PhMe2Si

Large R group

Small R group

B(nip)

Pt (0) or Pd (0)

R

SiMe2Ph

+ R

B(pin)

Pt (0) PhMe2Si B(pin)

Scheme 26

Rh(acac)(CO)2 efficiently catalyzes the hydrosilylative carbocyclization of various allenynes and trialkoxysilanes under an atmosphere of CO to give cyclic hydrosilylated products. Silylrhodation of the internal olefin of the allene proceeded exclusively, followed by carbometalation to the alkyne to give the cyclic 1,4-diene.160 The reactivity of the Rh(I) complex Rh(CF3COO)(NHC) (COD) (where NHC¼ 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) in the hydrosilylation of 1-alkenes, alkynes, and α,β-unsaturated compounds has been reported.144 A poly(styrene-codivinylbenzene) supported version of the catalyst is also reported. A series of monometallic and bimetallic catalysts, based on noncalcined and calcined platinum on titania, have been utilized in the hydrosilylation of 1,3-diynes. Symmetric diaryl- and dialkyl-substituted 1,3-diynes were successfully employed and in all cases, the reactions were highly regio- and stereoselective, affording monosilyl enynes and disilyl dienes with exclusively (E)-stereochemistry and the silicon attached to the internal carbon of the conjugated system.161

8.25.2.5 8.25.2.5.1

Synthetic Transformations and Applications Applications of hydrosilylation reactions

The triethylborane-initiated radical hydrosilylation reactions of phenyldimethylsilane and trichlorosilane with various alkenes proceed efficiently; on subsequent oxidation, the alcohol products show the net result of anti-Markovnikov hydrations of the original alkene.162 There have been a number of examples of the anchoring of molecules to Si surfaces via alkene hydrosilylation. For example, the hydrosilylation of styrene on water-saturated Si(001)-2×1 surface at room temperature has been reported by Bournel and Pietzsch.163 Lee has investigated the initiation mechanisms for surface hydrosilylation with 1-alkenes at 200 °C initiated by visible light or more slowly at room temperature in the dark.164 Hydrosilylation has also be utilized to tag α,ω-alkenynes on to a Si(111) surface, via alkene hydrosilylation, and with the alkyne-terminus protected with a TMG group. After degermylation, the alkynes readily underwent click reactions with various azides to tag various biological molecules (e.g., mannose, biotin) on to the surface.165 The mannose-tagged material was used to capture living targets (E. coli) on to the surface. The same ‘click’ approach has been used to immobilize antimicrobial peptides to surfaces.166 Zuilhof has utilized the reactions of silyl radical cations with nucleophiles to mimic the reactivity at silicon surfaces.167 They demonstrated that a delocalized Si radical cation (a surface localized hole) can initiate the hydrosilylation chain reaction at the Si surface. There have been a number of studies concerning the reaction of silicon nanoparticles. Terminal alkenes of varying chain length has been added to silicon nanoparticles between 2.5–30 nm in diameter by photoassisted hydrosilylation reactions in the aerosol phase.168 It was found that smaller particles functionalized with shorter chains at the interior (β) alkenyl carbon atom, whereas particles 410 nm in diameter attached via the exterior (α) alkenyl carbon atom irrespective of chain length. A similar study has been conducted into the influence of nanocrystal size on the reactivity of silicon nanocrystals (Si-NCs) near-UV photochemical hydrosilylation with 1-dodecene and phenylacetylene.169 The in situ gas-phase hydrosilylation of plasma-synthesized silicon nanocrystals using 1-alkenes and 1-alkynes has been reported.170 The method has considerable potential in the surface passivation of semiconductor nanocrystals, for use in novel optoelectronic devices, solar cells, and chemical sensors.

8.25.2.5.2

Applications of hydrosilylation reactions in total synthesis

Numerous total syntheses have been reported which include a hydrosilylation reaction at some stage during a multistep sequence. Furstner has described a concise, practical, and stereoselective route to macrocyclic (E)-alkenes via ring closing alkyne metathesis,

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

979

trans-selective hydrosilylation of the resulting cycloalkyne catalyzed by [Cp⁎Ru(MeCN)3]PF6 and finally protodesilylation of the resulting vinylsilane with AgF in THF/MeOH.171 Furstner employed a similar strategy, namely ring-closing alkyne metathesis followed immediately by trans-hydrosilylation of the resultant alkyne and protodesilylation as the key steps in the synthesis of the potent translation and cell migration inhibitor lactimidomycin (Scheme 27).172 The same group employed similar strategies in the total synthesis of the macrolide tulearin C173 and myxovirescin A1.174 Cossy has developed a one-pot hydrosilylation-ring closing metathesis-protodesilylation strategy for the synthesis of ω-alkenyl α,β-unsaturated lactones.175 Floreancig achieved an overall alkyne hydration reaction in the synthesis of the Carribean sponge cytotoxin neopeltolide by combining an intramolecular hydrosilylation reaction, using a Pt(DVDS) catalyst (DVDS ¼ divinyl dimethyldisoloxane) to form a siloxane, followed by a Tamao oxidation.93

Si(Bn)Me2 BnMe2SiH, [Cp*Ru(MeCN)3]PF6 (10 mol%) CH2Cl2, 0 °C

OTES O

OTES

O

O

O

TBAF, THF, 0 °C 64% (over 2 steps)

O HN

OH

O

O

Steps O

O

OTES O

O

Scheme 27

The ruthenium-catalyzed alkyne hydrosilylation reaction developed by Trost35,34 was utilized by Feringa in the asymmetric total synthesis of the virulence factor of Mycobacterium tuberculosis, known as phthiocerol dimycocerosate A or PDIM A.176 A suite of silylation reactions were employed by Denmark in the total syntheses of isodomoic Acids G and H.177 Rh(I) catalysts immobilized on polyamide supports are still able to catalyze the hydrosilylation of alkenes, dienes, and alkynes.113 The presence of 2,5- and 2,6-pyridines in the polymer also influenced the cis/trans selectivity of the hydrosilylation.

8.25.3

Hydrostannylation

8.25.3.1

Introduction

Lautens has published an excellent and comprehensive review of metal-catalyzed hydrostannations up to 2000.178 This gives an excellent introduction to the synthesis of organostannanes, presents mechanistic considerations, and comprehensively reviews the literature on hydrostannation reactions of alkynes, alkenes, allenes, and conjugated systems.

8.25.3.1.1

Hydrostannanes available

A few hydrostannanes are now commercially available, and include nBu3SnH, Ph2SnH2, and the fluorous stannane [CF3(CF2)4CF2]3SnH.

8.25.3.2 8.25.3.2.1

Hydrostannylation of Carbon–Carbon Triple Bonds Hydrostannylation of ethyne

Reaction of (Me2Sn)2CuCNLi2 with ethyne gives a bis(trimethylstannylvinyl)cuprate reagent which readily undergoes 1,4-conjugate addition with cyclic α,β-unsaturated ketones.179

8.25.3.2.2

Hydrostannylation of monosubstituted alkynes

Tributyltin hydride has been generated in situ from tributylchlorostannane and triethylsilane in the presence of catalytic amounts of a Lewis acid (ZrCl4 or B(C6F5)3) and utilized for the hydrostannation of carbon–carbon multiple bonds, including (internal and terminal) alkynes, alkenes, and allenes.180

980

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

Although hydrostannylation reactions, followed either directly or after isolation/purification by a Stille coupling, are well known, they have always suffered the drawback of requiring stoichiometric amounts of tin. Maleczka has reported a one-pot tandem palladium-catalyzed hydrostannylation/Stille coupling for the stereoselective generation of vinyltins and their subsequent coupling that is for the first time catalytic in tin. Using Me3SnCl as the tin source, it was possible to recycle the tin halide Stille byproducts back to the tin hydride using the mild hydride donor polymeththylhydrosiloxane (PMHS).181 The regioselective palladium-catalyzed hydrostannylation of terminal arylalkynes has been achieved using Bu3SnH and PdCl2(PPh3)2, in the presence of an ortho-substituent on the aromatic ring to direct the regioselectivity of the Sn–H bond addition. Irrespective of the nature of the substituent, the α-branched vinylstannane was always obtained. The products were utilized in Stille cross-couplings to give 1,1-diraylethylenes.182 The addition reaction of tin tetrachloride to PhC≡CH, tBuC≡CH, nBuC≡CH, or HOCH2C≡CH in dichloromethane has been reported to give the stannylated products with exclusively α-regioselectivity, with the steric bulk of the substituent being attributed with this outcome (Scheme 28).183 Reaction of norbornene or norbornadiene under the same conditions gave the exo stannylation product.183 In contrast, nickel, cobalt, or molybdenum-catalyzed hydrostannylation reactions, using tributyltin chloride, polymethylhydrosiloxane, potassium fluoride, and 18-crown-6 (as an in situ method of preparing the tin hydride) generally gave a mixture of α- and β-stannylated products, except when using MoBI3, which gave the proximal vinyltins as the major product.184

R

+

SnCl4

R

DCM, r.t.

H

Cl

SnCl3

Scheme 28

The hydrotelluration of alkynes occurs in a highly selective antimanner to give cis-vinyltellurides that do not undergo isomerization. The under-utilized lithium/tellurium exchange reaction has been employed by Williams as part of a two-step highly efficient method for the synthesis of cis-vinyltrimethylstannanes and cis-vinylpinacolboronates; this comprised hydrotelluration followed by lithium/tellurium exchange and quenching with either trimethyltin chloride or 2-isopropoxy-4,4,5,5-tetramethyl1,3,2-dioxaborolane.185 The same authors have prepared cis-vinylstannanes from alkynes bearing oxygen-containing substituents elsewhere in the molecule, also using the Li/Te exchange pathway; this is something that is impossible using ZrCl4, which is incompatible with oxygenated substrates.186 Roesky has published extensively on the reactions of tin(II) hydride species with unsaturated molecules, including alkynes.187,188 Stable β-diketiminate tin(II) hydride LSnH (L ¼ HC(CMeNAr)2, Ar ¼ 2,6-iPr2C6H3) reacts with activated terminal alkynes to give the tin(II)-substituted terminal alkene (and not dihydrogen elimination).188 It also reacted with disubstituted alkynes RO2C≡CCO2R to form the stannylene-substituted internal alkene. LSnH also reacted with ketones to give tin(II) alkoxides. The radical addition of trineophyltin hydride to ethynylcyclohexene gives exclusively (Z,E)-1-(2-trineophylstannylvinyl) cyclohexene, a conjugated dienylstannane, which could, in one pot, undergo Diels–Alder reaction with activated dienophiles, with the stannyl group in the resultant allylic position.189 Cai has reported the one-pot synthesis of 2-ethoxycarbonyl-substituted 1,3dienes and 1,3-enynes by the palladium catalyzed hydrostannylation of alkynyl esters, followed by a Stille coupling with alkenyl or alkynyl halides.190 Bu2Sn(OTf)H has been found to be an excellent reagent for the regio- and stereoselective hydrostannylation of propargylic alcohols (and longer chain alkynols) to give (Z)-stannylated allyl alcohols.191 The tin reagent was prepared in situ from Bu2SnH2 and TfOH. Coordination of the hydroxyl group to the Lewis acidic tin center was found to be crucial for the observed high regioand stereoselectivity (Scheme 29). OH R

Hexane, 3 h, r.t. Bu2Sn(OTf)H

( )n

Followed by BuLi

R ( )n

OH SnBu3

77−93%, >91% Z

Scheme 29

Kazmaier has reported distannylations and silastannylations of allenes generated in situ from propargylic ethers.192 Only Bu3SnH and Pd(PPh3)4 were required to convert propargylic ethers and esters directly into distannylated alkenes, the reaction postulated to occur via a stannylated allyl alcohol derivate, which subsequently underwent elimination and dimetallation. The two processes could be decoupled by utilizing a molybdenum catalyst in the hydrostannylation step. This permitted the selective reaction of the stannylated intermediate with other dimetallic compounds, for example to introduce silicon. Kwon has studied the palladium-catalyzed hydrostannylation of ethyl ethynyl ether, using 0.001 equivalent of Pd(PPh3)4 and 1 equivalent of tributyltin hydride.193 The hydrostannylation occurred in 95% yield, as a 1:0.69 β:α mixture. However, only the β-regioisomer underwent subsequent Stille coupling reactions, providing a facile method for the separation of the two products.

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

981

Although the majority of transition metal-catalyzed hydrometalations and carbometalations proceed in a cis manner, the Lewis acid promoted reactions tend to proceed in a trans manner, as reported by Yamamoto: hydrosilylation, hydrostannylation, carbosilylation, and carbostannylation or unactivated alkynes with organosilanes or organostannanes all gave the trans-vinylsilyl or vinylstannyl compounds.40

8.25.3.2.3

Hydrostannylation of disubstituted alkynes

The palladium-catalyzed hydrostannylation of substituted propargyl alcohols with the bulky trineophyltin hydride reagent has been reported by Podesta, giving exclusively the products of syn-addition but in variable ratios of syn-α and syn-β products.194 The hydrostannylation of carbonyl-activated alkynes proceeds in good yields when catalyzed by CuCl in the presence of KOtBu, triphenylphosphine, and tributylstannane. The reaction generates copper hydride in situ, adding to the alkyne before transmetallation. Addition of the tin always occurred at the alkyne carbon attached to the adjacent C ¼ O.195 Tanner has reported that (E)β-trialkylstannyl-α,β-unsaturated ketones can also be prepared from secondary propargylic alcohols via a two-step sequence of Pd (0)-catalyzed hydrostannylation followed by tetrapropylammonium perruthenate oxidation. This was used in an approach toward the marine natural product Zoanthamine.196 The palladium-catalyzed hydrostannylation of α-heteroalkynes and alkynyl esters has been performed in the ionic liquid 1-butyl-3-methyl-imidazolium hexafluorophosphate. The reaction tolerated both S- (sulfides and sulfones) and Se-substituents on the alkyne.197 1,4-Dienyl selenides have been stereoselectively prepared by the palladium-catalyzed hydrostannylation of acetylenic selenides, followed directly by Stille coupling with allylic bromides.198 Roesky has reported that stable β-diketiminate tin(II) hydride LSnH (L¼ HC(CMeNAr)2, Ar ¼ 2,6-iPr2C6H3) reacts with disubstituted alkynes RO2C≡CCO2R to form the stannylene-substituted internal alkene.188 Moses has reported the first regioselective hydrostannation (using tributyl- or triphenyltin hydride) of an aryne, generated in situ from o-trimethylsilylphenyl triflates or anthranilic acid, without the use of additives or catalysts.199

8.25.3.3 8.25.3.3.1

Hydrostannylation of Carbon–Carbon Double Bonds Hydrostannylation of monosubstituted alkenes

Tributyltin hydride has been generated in situ from tributylchlorostannane and triethylsilane in the presence of catalytic amounts of a Lewis acid (ZrCl4 or B(C6F5)3) and utilized for the hydrostannation of carbon–carbon multiple bonds, including (internal and terminal) alkynes, alkenes, and allenes.180 This is reported to be the first example of a Lewis acid-catalyzed hydrostannation of an alkene. The regio- and stereoselective hydrostannylation of monosubstituted allenes has been performed using di-n-butyliodotin hydride, to give α,β-disubstituted vinyltins (Scheme 30).200 Without isolation, these products could subsequently be employed in palladium-catalyzed cross-couplings with aromatic halides to give multisubstituted alkenes in a one-pot overall procedure. The regioselectivity of the initial hydrostannylation was highly dependent on the nature of the allene substituent. Sn

alkyl

R

•

Bu2SnIH THF, r.t.

H 65−88% upto 93:7 R′O

H Sn

Ph

alkyl PhI

H

Pd (cat) R′O

H Ph

R′ = alkyl 57−59% >95:5 Scheme 30

8.25.3.3.2

Hydrostannylation of disubstituted alkenes

The free radical hydrostannylation of unactivated alkenes using chiral trialkylstannanes has been reported by Schiesser (Scheme 31).201

OTBDMS

MenPh2SnH Et3B, O2, −78 °C 99%, dr 1.3:1

Scheme 31

TBDMSO Ph Ph Sn

982

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

Lautens has reported a palladium-catalyzed hydrostannylation of unsymmetrical oxabicyclic alkenes (oxabicyclo-heptenes and -octenes).202 The products of the Pd-catalyzed hydrostannylation underwent elimination to the cyclohexenol (Scheme 32).

HO Bu3SnH (1.5 equivalents), 2 mol% [Pd2(dba)3]

O

10 mol% PPh3, toluene, r.t. 80%

OH

n-BuLi (3−5 equivalents)

O

OH

OH

Bu3Sn

Scheme 32

Yamamoto has described differing outcomes for the hydrostannation of allenes depending on the reaction conditions employed: the use of tributyltin hydride with a Lewis acid B(C6F5)3 produced vinylstannanes regioselectively, whereas tributylstannyl- and triphenylstannyl hydrides in the presence of Pd(PPh3)4 gave allylstannanes regioselectively (Scheme 33).203

Bu3SnH B(C6F5)3

Bu3Sn

H

R

H

• R

Pd(PPh3)4 Bu3SnH

H R

SnBu3 H

H R

H SnBu3

Scheme 33

8.25.3.3.3

Synthetic transformations and applications

One acyclic, two heterocyclic, and two bicyclic alkenyl stannanes were prepared by de Meijere, including one by [RhClCOD]2 catalyzed hydrostannylation of (tert-butyldimethylsilyl)acetylene with tri-n-butyltin hydride and the products used in the synthesis of 1,3,5-hexatrienes, which were subsequently utilized in studying thermally induced 6π-electrocyclizations.204 The stereoselective synthesis of (Z)-α-arylsulfanyl-α,β-unsaturated ketones via a Stille coupling reaction has been reported, starting from arylsulfanylvinylstannanes, acyl halides, and a Pd(PPh3)4/CuI catalyst.205 Quintard has performed a study on the synthesis, characterization, and reactions of supported vinyltins and allyltins grafted on to an insoluble cross-linked polystyrene matrix.206 The starting materials were prepared by alkyne hydrostannylation (or other methods, such as transmetallation or SN2′ substitution of β-stannylacrolein by cyanocopper reagents). The grafted organotin reagents were analyzed by HRMAS NMR, which permitted unambiguous assignment of their isomeric distribution and also identification of side products. The supported reagents demonstrated similar reactivity and stereoselectivity to their tributyltin analogs when involved in Stille cross-coupling reactions or addition reactions to aldehydes, but without any tin contamination of the products.

8.25.3.4

Applications of Hydrostannylation Reactions in Total Synthesis

The hydrostannylation of alkynes has played a key role in the total syntheses of many molecules, including the C1-C9 and C10C21 segments of the lycoperdinosides (Bu3SnH, Pd(Ph3P)2Cl2, THF, r.t.);207 in two different approaches to combretastatin A4 and related compounds;208,209 in a protecting group free synthesis of (+)-Crocacin C, including an enzymatic enantioselective desymmetrization of a meso-diol and a one-pot alkyne hydrostannylation, subsequent Stille coupling (PdCl2(PPh3)2 (5 mol%), Bu3SnH, THF, 0 °C; and followed by substituted vinyl iodide, 100 °C, microwave irradiation, 15 min).210

8.25.4 8.25.4.1

Hydrogermylation Introduction

In this section, the addition reactions of hydrogermanes to alkenes and alkynes and their synthetic transformations and applications are considered. There have been a number of syntheses of hydrogermanes from a variety of precursors and the methods reported in the previous edition are still relevant.211 Organosilanes and organogermanes have developed as popular alternatives to the Stille and Suzuki reactions for Pd-catalyzed cross-coupling reactions; their use has been reviewed.2

Hydrometallation Group 4 (Si, Sn, Ge, and Pb) 8.25.4.1.1

983

Available germanes

A few germanes are now commercially available and include GeH4, Et3GeH, (TMS)3GeH, nBu3GeH, nHex3GeH, and Ph3GeH.

8.25.4.1.2

Synthesis of organohydrogermanes

A common route for the preparation of organohydrogermanes is by the direct reduction of organogermanium halides using the reducing agents LiAlH4 or NaBH4.212 The preparation of the germole 6 (Scheme 34) and the optically active species 7 and 8 (Schemes 35 and 36) are some examples.

Ph

Cl Cl Ge Ph

+

LiAlH4

THF, 25 °C

Ph

H H Ge Ph

Ph

51%

Ph

Ph

Ph 6

Scheme 34

Br Br

1. n-BuLi, Et2O, −20 °C

Me Ge

2. MeGeCl3, Et2O −20 °C to 0 °C

Cl

LiAlH4, Et2O

Me Ge

0 °C

H

7 Scheme 35

Br

GeCl2Br

GeCl2.dioxane

O O

1. NaBH4 (3 equivalents) THF, 25 °C, 5 h

O O

1,2-dichlorobenzene 110 °C, 12 h

GeH3 O O

2. H2O 8

Scheme 36

Dimethylgermylene Me2Ge inserts rapidly and easily into the O–H, S–H and N–H bonds of water/deuterium oxide, alcohols, carboxylic acids, oximes, and phthalimide to yield substituted organogermanium hydrides Me2Ge-H. PhSMe2GeH was found to bring about spontaneous hydrogermylation of alkenes. Further complexes were found to add to alkenes and alkynes.213 The synthesis of the germanium(II) hydride 9 has been reported. This reacts with alkynes at room temperature to form germanium(II)substituted alkenes (Scheme 37). The catalyst was also capable of reaction with carbon dioxide and elemental sulfur.214,215 Another structurally similar N-heterocyclic germanium(II) hydride, namely [(MeMesNacnacn)GeH], has been prepared from the β-diketiminato germanium(II) chloride complex [(MeMesNacnacn)GeCl], and undergoes reversible hydrogermylation with a phosphaalkyne P≡CtBu.216 Ar N Ge N H Ar

R

CO2R1

Ar N R Ge N H Ar CO2R1

9 Scheme 37

The hydrogen donation or transferability of a range of substituted germanium hydrides toward primary alkyl radicals has been investigated by kinetic studies and reviewed.217 The procedures reported in Comprehensive Organometallic Chemistry I and II for the halogenation of Ge–H bonds are still extensively utilized. Recently, their preparation by the reaction of hydrosilanes with alkyl or allyl halides catalyzed by PdCl2 or NiCl2 (Scheme 38) was reported.218

984

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

R2X R14−nGeHn

1−3 mol% PdCl2 58−98%

n = 1 to 3

R14−nGeXn

R1 = Et, Hex, Ph R2 = allyl, PhCH2 Scheme 38

Two methods have been reported for the alkylation of the Ge–H bond, based around radical and palladium-catalyzed methodologies. First, radical-promoted desulfonylation of vinyl sulfones for the alkylation of organohydrogermanes are still relevant (Scheme 39).219,220 The bulky germanium hydride tris(trimethylsilyl)germane has been used to react with alkynes to give selectively (Z)-alkenes (Scheme 40).219,220 The products from both schemes have been utilized in Pd-catalyzed couplings.219 Second, alkylation of the Ge–H bond may be achieved by the palladium catalyzed coupling with aryl iodides (Scheme 41).

(Me3Si)3GeH, AIBN

O S

(Me3Si)3Ge

R

O

R

PhH or PhMe, 80 °C

R = Ph, PhCH2CH2, 51−80% Scheme 39

R

+

(Me3Si)3GeH

AIBN, PhH 25 °C or above

R

Ge(SiMe3)3

R = Ph, p-CH3OC6H4, o-CF3C6H4, p-CF3C6H4, C6H13 80−98% Scheme 40

O GeH

+ R−X

Pd(OAc)2, DPPF, Cs2CO3

3

DMF, 25 °C

O GeR 3

R = Ph, MeOC6H4I, MeC6H4I, CH=CH(Me) X = I or Br Yield = 54−88% Scheme 41

Carbene complexes of the type M ¼ E (E¼ Si or Ge) have been reported with hydrogen atoms on both the metal center and the E atom. These have been shown to undergo hydrosilylation and hydrogermylation reactions readily, as well as reaction with nitriles, ketones, and heterocumulenes.5

8.25.4.2

Hydrogermylation of Carbon–Carbon Triple Bonds

Examples of Lewis acid-catalyzed hydrogermylation of alkynes have been reported by Schwier and Gevorgyan221 cf. the related hydrostannation of allenes discussed previously.203 This mild method displays relatively higher functional group tolerance, compared with hydrometalation reactions promoted by Lewis acids which are only compatible with a narrow range of functional groups, for example, bulky TBS- or TIPS-protected alcohols. The method has been found to undergo selectively trans-addition when simple alkynes were employed (Scheme 42) and cis-addition when propiolates were used as starting materials (Scheme 43). Under these conditions, treatment of the alkyne 10 with triethylsilane gave the quantitative product of O–Me cleavage and no hydrosilylation products were observed (Scheme 44). In contrast, it was found that by changing the silicon to germanium, the reaction proceeded with complete hydrogermylation, conserving the methoxy moiety in the processs.221

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

R2

B(C6F5)3-cat

NIS

R1

Ge

HGe

R2

R1

H

R1

R2

H

R1 = Ph, R2 = Me, 99%

89−99%

R1, R2 = H, alkyl, Ar

I

985

Scheme 42

R2O2C

HGe R2

R1

B(C6F5)3-cat 85−99%

R1

NIS

R2O2C

H

Ge

I

R1 = H, Me, n-C5H11, Ph R2 = CO2Me, CO2Et

R1 H

R1 = C5H11, R2 = Me, 88% R1 = Ph, R2 = Et, 85%

Scheme 43

HSiEt3 B(C6F5)3

Bu

Bu

5 mol%

+

HGeEt3

99%

B(C6F5)3 5 mol%

Bu MeO

93%

GeEt3

MeO

Et3SiO

10

Scheme 44

Using a range of hydrogermanes, the formation of various (Z)-vinylgermanes, have been reported, including bifunctional vinylgermanes, in all cases with complete regio- and stereoselectivity in excellent yields (Scheme 45).221 Vinylgermanes are important intermediates and their utility for the transformation into vinyl halides have also been demonstrated in the same publication (Scheme 46).221

R

1

R2

+

B(C6F5)3-cat 5 mol%

3

HGeR

3

CH2Cl2, r.t.

R33Ge R2

R1 H

85−99%

R1 =

H, alkyl, Ar R2 = CO2R

R3 = Me, Et, Bu, Ph Scheme 45

RO2C

R1

NIS, AlCl3

Et3Ge

H

CH2Cl2, 0 °C

Et3Ge Me

RO2C

R1

I

H

Ph

Ph

NIS or NBS

X

H

CH2Cl2, r.t.

Me

R1 = C5H11, R2 = Me, 88% R1 = Ph, R2 = Et, 85%

X = Br, 92% X = I, 99%

H

Scheme 46

These bifunctional vinylgermanes containing both electrophilic and nucleophilic components can be used in cross-coupling reactions, either at the aryl halide handle or in a Suzuki reaction before halogermylation to attain the vinyl halide moiety (Scheme 47).221

986

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

Bu Bu

GeEt3

Bu I GeEt3

GeEt3

O B O

Br

Scheme 47

Triethylborane induces the intramolecular hydrogermylation of homoallylic and homopropargylic alcohols. It was found that the platinum-catalyzed hydrogermylation of 3-hexenoxydipropylgermane gave the five-membered ring product 5-propyl-1-germa-2oxacyclopentane as a main product, but the triethylborane-induced radical cyclization gave the six-membered ring product 6-ethyl-1germa-2-oxacyclohexane selectively.222 The hydrosilylation and hydrogermylation of alkyl esters of propiolic acids gave mixtures of alkyl esters of 2-triethylsilyl(germyl)- and (E)-3-triethylsilyl(germyl)acrylic acids. Alkyl esters of organosilicon(germanium) β-amino (hydrazino)propionic acids were obtained by amination of the alkyl esters of 2-triethylsilyl(germyl)acrylic acids.223 PhSMe2GeH, prepared by the insertion of Me2Ge into the PhS–H bond, was found to bring about spontaneous hydrogermylation of alkenes.213 The catalytic trans-selective hydrogermylation of both terminal and internal alkynes has been reported by Nakazawa, employing CpFe(CO)2(Me) and a bis(germyl)hydridoirom(IV) complex as a catalyst precursor (Scheme 48).224 The crystalline structures of the proposed catalytic intermediates are reported.

R13GeH

+

R2

R3

CpFe(CO)2Me 7 mol% 80 °C

H

R3

R2

GeR13

R1 = Et, Ph, n-Bu, R2 = Ph, 4-F-C6H4, 4-Me-C6H4, 4-OMe-C6H4, 4-NH2-C6H4, Hex, c-Hex, Pr, CO2Me R3 = H, Me, Ph, Pr, CO2Me Time = 6 − 18 h Yield = 43 to >99% Scheme 48

The reaction of alkynols or alkynes with Et3GeH catalyzed by rhodium complexes affords the corresponding alkenes in quantitative yields (Scheme 49).225,226 Some of the reaction intermediates have been isolated in reasonable yields and the mechanism has been proposed (Scheme 50).226

R

+

Et3GeH

Rh cat. C6D6

R +

By-product

GeEt3

R = CO2Me, Ph Scheme 49

Alkenyl complexes can also be prepared by the reaction of similar rhodium species with alkynes.225 Various hydrogermylation catalysts using other transition metal complexes, including a 1:1 mixture of palladium phenanthroline complex (Phen)Pd(Me)Cl and NaBAr4 (Ar ¼ 3,5-C6H3(CF3)2) have also been reported.227 Duchene has reported a highly regio- and stereoselective Lewis acid-free synthesis of vinylgermanes via the hydrogermylation of alkynes. Using ultrasound or microwave heating, hydrogermylation occurred without a transition metal catalyst or AIBN initiator; the (Z)-alkenylgermane was the major product.228 A tandem hydrogermyl-carbonylation functionalization of alkynes in the presence of CO has also been achieved (Scheme 51).229 The hydrogermylation polymerization of diphenylgermane with aliphatic and aromatic diynes proceeded smoothly in the presence of Pd–PCy3 to give new germylene–divinylene polymers in high yields.230

8.25.4.3

Hydrogermylation of Carbon–Carbon Double Bonds

Dibutylchlorogermane (Bu2GeClH) is another hydrogermylating agent used on alkenes that has appeared in recent literature. Following the preparation of this agent from germanium tetrachloride, high yields of a range of alkyl germanes were isolated

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

O O

OH R R

H

+

Rh PCy3

R HO O

Pentane, −78 °C

−

R

H

Rh

O

987

PCy3

R = Me, 84% R = Ph ,71% OH −

R

H R

OH

+ H

R R O

GeEt3

O

GeEt3

Rh

R = Me or Ph, ∼100%

Et3GeH PhMe

PCy3

R = Me, 65% R = Ph, 60% Scheme 50

O

CO (1 atm)

O GeH

n-C6H13

+

3

PhMe, 25 °C 5.5 h 58%

n-C6H13

Ge O

3

cat. = 2.5 mol% [PdCl(3-C3H5)]2 t-Bu

Phosphine: 10 mol% O

t-Bu

P 3

Scheme 51

under homolytic conditions in an Et3B-dry air atmosphere at room temperature.231 Curran has reported two members of a new class of dithiogermanium hydride that have been prepared in both racemic and enantiopure forms. Reaction of 2,2′-dithiobinap and 3,3′-bis-trimethylsilyl-2,2′-dithiobinap with tBuGeCl3 followed by reduction gave the corresponding germanium hydrides. These were utilized in the hydrogermylation of methyl methacrylate, with the latter giving the best selectivity.232 It has been found that alkenes, dienes, alkynes, and carbonyl compounds will all undergo hydrogermylation using tri(2-furyl) germane.229,233,234 The hydrogermylation process proceeds selectively on the soft center for α,β-unsaturated carbonyl derivatives (Scheme 52). A mini-review of the use of tri(2-furyl)germane, triphenylgermane and their derivatives in synthesis has been published and the reader is directed to this for comprehensive discussion and results.235

O O

R

GeH 3

O

R

cat. Cs2CO3 1,3-dimethyl-2-imidazolidinone

Ge O 3

R = CH3, 84%; R = chex, 83%; R = OBun, 95%; R = NH2, 87% Scheme 52

Nakamura has reported the use of triethylborane-promoted hydrogermylation of alkynes and terminal as well as internal alkenes employing tri-2-furylgermane (Scheme 53).236 The nucleophilic mechanism of hydrogermylation utilizing trichlorogermane has been suggested by Lakhtin in the preparation of silyl-substituted ethylenes (Scheme 54).237

988

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

R1 H

R3 R1

O GeH

R4 3

R2

Et3B, O2

R2

O Ge

Neat

R3

R4

R1 = n-C3H7, n-C5H11, Et, Me, C6H9Me, H R2 = H, Me, Et R3 = H, n-C5H11, Me R4 = H, Me, n-C3H7, CH2OR, (CH2)2COMe, (CH2)2CH(Me)CH2CHO, CH2OCH2CHCH2 Yields = 70−100% Scheme 53

+

Si

HGe(CH3)3

Si

+

HGe(CH3)3

Cl Si Cl

+

HGe(CH3)3

Cl

Cl Si Cl Cl

+

HGe(CH3)3

72% (H3C)3Ge 78% (H3C)3Ge

68% (H3C)3Ge

Si

Si

Cl Cl Si

Cl

73% (H3C)3Ge

Cl

Si

Cl Cl

Scheme 54

Functional vinylgermanes have the important synthetic utility as organometallic reagents. Their preparation via germylation of nonisomerising olefins using vinyl-trisubstituted germanes in a novel ruthenium-catalyzed coupling reaction has been reported (Scheme 55).238 This new catalytic method evades their alternative synthesis by olefin cross-metathesis, which has been found to be limited to vinylsilanes and vinylboronates only.

[RuH(Cl)(CO)(PPh3)3]

+

Ge(CH3)3

−PPh3, ethene

[RuH(CI)Ge(CH3)3(CO)(PPh3)2]

80 °C, 24 h, inert

Scheme 55

The radical addition of Ph3GeH to the ethylenic starting material 11 afforded the near quantitative yields the hydrogermylation products as shown (Scheme 56). The hydrogermylation of the same starting material (11) with Ph2ClGeH was also effective, giving the product in 97% yield (Scheme 56). Ph2ClGeH has been found to be more reactive than Ph3GeH, as the Ge radical formed has greater molecular electronegativity and molecular hardnesse owing to the presence of the halogen on the starting material.239 Regioselectivity appears to be influenced by the availability of the HOMO electrons on the exocyclic double bond. Based on DFT calculations, it was found that the structure of the intermediate radical also has an impact on its addition to the substrate and subsequent abstraction of hydrogen. Hydrogermylation of the C ¼ C double bond was also observed when the conditions were applied to nonconjugated systems, with near quantitative yields (Scheme 57).

8.25.4.4

Synthetic Transformations and Applications

The reaction of triethylgermane with alkynes in the presence of a ruthenium catalyst, [Cp⁎Ru(MeCN)3]PF6, occurs in a trans manner. The trans-hydrogermylation of 1,3-diynes with dihydrogermanes such as Ph2GeH2, affords 2,5-disubstituted germoles and in a double addition process was applied to the synthesis of 2,2′-bigermole (Scheme 58).240 Catalytic copolymerization has been employed to introduce germanium into extended polymeric systems. Examples include the incorporation of the germylene Ge[N(SiMe3)2]2 into acetylene monomers using rhodium catalysis (Scheme 59) and copolymerization with different sized cyclic ketones have also been reported (Scheme 59). These novel functional germanium polymers bearing a germanium enolate

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

989

Me X Y + Me X

H GePh3

GePh3 Me X = H; Y = AIBN, PhCO2Ot-Bu, t-Bu2O2, 20 °C to 130 °C, 24 h, quantitative X = OH; Y = AIBN, 100 °C, 24 h, 95%

Me

Me

AIBN 11

+

X

H GePh2Cl 100 °C, 24 h

97% Me

GePh2Cl

Scheme 56

Me

Me O H GeR3

+

O

AIBN 100 °C, 24 h Me

Me

GeR3

R3 = Ph3 or Ph2Cl, 100% Scheme 57

structure in the main chain have been prepared for the first time. These unusual germanium enolate units make the polymers structurally interesting particularly in the context of material science.241 Ph

Ph + Ph2GeH2

cat. [Cp*Ru(MeCN)3]PF6 r.t.

Ph

Ge Ph2

Ph2 Ge Ph

Scheme 58

The products of hydrogermylation have a number of multidisciplinary applications. In the field of electronics, germanium nanowires can be incorporated into field effect transistors (FETs). Following their in situ preparation, alkylation provides a coating that is resistant to oxidation (Scheme 60).242 Karpenko and Kolesnikov have investigated the synthesis and biological activity of germylated steroid analogs for their potential antitumor and antiviral properties. Hydrogermylation was carried out on the conjugated steroid 16-en-20-ones by the addition of trichlorogermane to the double bond in position 16 (Scheme 61).243 The isomeric ratio was influenced by reaction temperature, with increasing the temperature favoring the formation of isomer b. The synthesis and diastereomeric resolution of 2,6-diethyl-4,8-dimethyl-1,5-dioxo-s-hydrindacene has been described and the properties of this compound discussed with respect to radical, anionic, and cationic germylation reactions; in particular it acts as an efficient spin trap in the radical hydrogermylation of alkenes.244 Substituted vinylgermanes and divinylgermanes have been prepared by the reaction of olefin and dienes catalyzed by [RuHCl (CO)(PCy3)2] that is, germylative coupling and also by dehydrogenative germylation with hydrogermanes.245 The reaction of styrene with nBu3GeH employing ruthenium and rhodium complexes (of which Ru3(CO)12 was the most efficient) gave the corresponding vinylgermanes (α, β-(Z)- and β-(E)-) as the dehydrogenative germylation products.246 The Lewis acid-mediated hydrogermylation of alkenes and alkynes on hydride-terminated Ge(100) surfaces has been described by Buriak.247 The resultant monolayers were characterized by IR spectroscopy, stability studies, and contact angle measurements. The surface oxidation and chemical passivation of single-crystal Ge nanowires has been studied by Korgel, using wires of diameter 7–25 nm. The behavior was found to be quite different from monolithic atomically single-crystal substrates. Among many reactions studied, thermally initiated hydrogermylation reactions with alkenes produced chemically stable covalently bonded monolayer coatings and this enabled ohmic electrical contacts to be made to the nanowires.248 The preparation and

990

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

N(TMS)2 Ge[N(SiMe3)2]2

+

Catalyst

R

Ge

C C H R N(TMS)2

m n

N(TMS)2 Ge[N(SiMe3)2]2

Catalyst = EtOLi, 99%, Mw/Mn = 2.56; Catalyst = LiI, 99%, Mw/Mn = 1.69

Catalyst

O

+

Ge

O

THF, 0 °C, 3 h N(TMS)2 O

N(TMS)2 But-OLi

+

Ge[N(SiMe3)2]2

Ge

THF, 0 °C, 3 h 93%

O

N(TMS)2

O Ge[N(SiMe3)2]2

n

n

N(TMS)2 LiN(TMS)2

+

Ge THF, 0 °C, 3 h 91%

O

Mw/Mn = 1.73

N(TMS)2

n

Scheme 59

R Ge GeH GeH GeH

R

220 °C

+

−Ge Ge

R R

Thermal hydrogermylation Scheme 60

O HGeCl3

H H AcO

H

O H

H

H AcO

H Isomer a

GeCl3

O H

+

H

H AcO

GeCl3 H

H Isomer b

Scheme 61

functionalization of porous germanium (PG) has been achieved using a novel bipolar electrochemical etching technique, and scanning electron microscopy has shown the formation of a porous layer a few microns thick and which is Ge–H terminated, as determined by FTIR spectroscopy. Although the material is resistant to thermal oxidation, it does undergo hydrogermylation reactions with alkenes and alkynes.249

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

8.25.5

991

Hydroplumbation

8.25.5.1

Introduction

In this section, the addition reactions of hydroplumbates to alkenes and alkynes and their synthetic transformations and applications are considered. The reader is referred to Finet's chapter for a general review on well-defined organolead reagents.250 The authors are aware that there are only limited recent examples of hydroplumbation and therefore related examples will also be presented. The synthesis and chemistry of tin and lead compounds was reviewed in 1992.251

8.25.5.1.1

Available plumbanes

A few plumbanes are now commercially available, and include tricyclohexylplumbane c-hex3PbH, tris(4-methylphenyl)plumbane, tris(1-naphthyl)plumbane, tris(2-methylphenyl)plumbane, tris(2-ethoxyphenyl)plumbane, tris(4-ethoxyphenyl)plumbane, and trimesitylplumbane.

8.25.5.2

Hydroplumbation of Carbon–Carbon Triple Bonds

The synthesis of butadienyl- and butenyl-plumbanes and stannanes by hydroplumbylation and hydrostannylation of vinylacetylene and 1-butyne has been reported.252 The majority of the examples of hydroplumbylation, alkoxyplumbylation, and amino-plumbylation of alkynes (Scheme 62) date back in the literature to periods outside the scope of this chapter.252–254

Et3PbCl

+

LiAlH4

Et3Pb

Et3PbCl

+

LiAlH4

Et3Pb

Me3PbX

+ F3C

CF3

Me3Pb CF3

F3C

X

X: OMe or NMe2 Scheme 62

The conjugate addition of Et3PbM (M ¼ Na, Li) to HC≡CSR (R ¼ methyl or ethyl) has been found to be both stereoselective and regioselective to give cis-Et3PbCH ¼ CHSR. The reaction also proceeded with HC≡COEt to give CH2 ¼ C(OEt)PbEt3.255 A few related reactions will now also be mentioned. Metathesis reactions coupling an alkynyllithium, an alkynylsodium or a Grignard reagent with the corresponding organolead chloride have been employed to give triorgano(alkynyl)lead and diorganobis (alkynyl)lead compounds (Scheme 63).256–259

Me3PbCl

+

Li

Cl

Me3Pb

R3PbCl

+

Li

PPh2

R3Pb

Cl

+

LiCl

PPh2 +

LiCl

R: Me or Ph Ph 2 Me3PbCl

+

Li

Ph

P

Me3Pb

Li

P

+ 2 LiCl

PbMe3

Scheme 63

The protonolysis of triorgano(alkynyl)lead alkoxides, hydroxides, and amines can also afford triorgano(alkynyl)lead derivatives (Scheme 64).260,261 Bis(metallo)-substituted alkynes may also be prepared using this method (Scheme 65). Metathesis between alkali metal hexachloroplumbate (IV) salts and alkynyllithium reagents successfully afforded tetrakis (alkynyl)lead compounds (Scheme 66).262

992

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

R3PbOH

+

H

R′

R3Pb

R′

+

H2O

Et3PbOMe

+

H

R

Et3Pb

R′

+

MeOH

Ph3PbNEt2

+

H

Na

Ph3Pb

+

Et2NH

Na

Scheme 64

+

R3PbCl

Na

R′

PbR3 +

R3Pb

NaCl

Scheme 65

R M2PbCl2

+

4 Li

R

R

+ 2 MCl + 4 LiCl

Pb

M: K or Rb

R

R

Scheme 66

Traditional transmetallation involving tin-lead exchange or mercury-lead exchange have both been used to generate alkynyllead triacetates.263,264 However, these approaches involve the isolation of unstable alkynylmetal derivatives and in situ transmetallation methods employing lithium or zinc have since been developed. Lithium acetylide in THF can be added to lead tetracetate in CH2Cl2 at low temperatures to generate the alkynylmetal reagent in situ (Scheme 67). The addition of benzyl β-ketoesters to this reaction mixture yields the corresponding benzyl α-alkynyl-β-ketoesters.265 n-C5H11

1. BuLi, THF

n-C5H11

H

(AcO)3Pb OSiMe2t-Bu 2. Pb(OAc) , CHCI 4 3

OSiMe2t-Bu

Scheme 67

The use of the optically active (S)-alkynyllead triacetate is an example of the alkynylation of enolates, prepared by lithium-lead tetracetate metal–metal exchange (Scheme 68).266

Pb(OAc)3

O +

O

CH2Cl2-THF (5:1)

O

O

OSiMe2tBu

r.t., 10 min, 74%

OSiMe2tBu

CO2Allyl O

O

CO2Allyl

Scheme 68

It was observed that the alcohol functional group of the β-ketoester is essential to the success of the alkynylation reactions shown, similar to what has been observed for the alkenylation reactions,267 with good yields obtained when methyl or benzyl esters are used.268 However, when the alkynyllead reagent prepared by Li-Pb exchange failed to react with ethyl 2-oxocyclopentanecarboxylate to give the desired alkynylated product and a dimer was isolated instead. (Scheme 69). The addition of ZnCl2 in the generation of a zinc-lead reagent discourages the oxidation of the lead tetraacetate and as a result the dimer has been isolated only as a minor product (Scheme 70). The zinc-lead metal–metal exchange has been utilized in the alkynylation of a range of soft nucleophiles and several examples are shown in Schemes 71 and 72.268 Interestingly, in the final example involving mesitol as a starting material, no alkynylated product was isolated and no dimer resulting from the tin-lead exchange was observed (Scheme 72). Instead, 2-acetoxydienone (12) was afforded along with a new

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

993

O O +

O

Li

Bu

+

O

O

−20 °C

Pb(OAc)4

O O

O O

Scheme 69

1. BuLi, THF, −78 °C 2. ZnCl2, −78 to 10 °C 3. Pb(OAc)4, CHCl3, −10 °C

O O + H

R

O

R O

O

O

O

O O

+

O O

O

R = Ph; 79% R = Hex; 52%

8%

Scheme 70

O

O +

H

R

1. BuLi, THF, −78 °C 2. ZnCl2, −78 to 10 °C 3. Pb(OAc)4, CHCl3, −10 °C

O

O

R = Ph; 59% R = Hex; 52%

Na O

O N

+

H

R

R

1. BuLi, THF, −78 °C 2. ZnCl2, −78 to 10 °C 3. Pb(OAc)4, CHCl3, −10 °C

NO2 R

R = Ph; 59% R = Hex; 52%

Scheme 71

Ph

OH +

H

R

1. BuLi, THF, −78 °C 2. ZnCl2, −78 to 10 °C 3. Pb(OAc)4, CHCl3, −10 °C

O

OAc +

R = Ph; 59% R = Hex; 52% 12 11%

O −AcOH

13 41%

Scheme 72

dimer 13, which could be derived from a Diels–Alder reaction between 6-phenylethynyldienone with the aforementioned acetoxylation byproduct (12). Fedorov et al. reported back in 2005 the use of functionalized organolead arylation reagents in the reductive coupling of benzopyran derivatives. Aryllead triacetates were prepared from a boron-lead transmetallation, thereby inverting the reactivities at the electrophilic centere (Scheme 73).269 These 2-(halomethyl)aryl functionalized organolead reagents were established as efficient tools for the cascade synthesis of benzopyran derivatives in a series of one-pot reactions.

994

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

B(OH)2

Pb(OAc)3 Transmetallation

XH2C

XH2C

Denotes site of electrophilic reactivity

Scheme 73

Both vinylmercury and vinylstannane compounds, which may be generated by hydrostannylation reactions or other methods, undergo rapid metal–metal exchange with lead tetraacetate to generate vinyl-lead triacetates; these proved to be unstable, undergoing thermodynamically favorable reductive elimination of lead(II) acetate to give an alkyne or an enol acetate, depending on the original alkene-substitution pattern.270

8.25.5.3

Hydroplumbation of Carbon–Carbon Double Bonds

There are no new examples to be considered.

8.25.5.4

Synthetic Transformations and Applications

Triphenyl(allenyl)lead is a good example of an organolead compound having an important synthetic application in organic chemistry. This reagent is prepared from reacting triphenylplumbylmagnesium bromide with the commercially available propargyl bromide (Scheme 74). H

H Br

PhMgBr

Ph3Pb

Ph3PbMgBr

PbCl2

C

3 equivalents

H

H

Scheme 74

This is then utilized as a versatile propargylating reagent when subsequently exposed to selected aldehydes under Lewis acidic conditions to yield the corresponding homopropargylic alcohols (Scheme 75).

H C

O Ph3Pb

C

H

H

HO

+ R

R

H Scheme 75

It is noted that in order for benzophenone to react under the aforementioned conditions, an extra step of transmetallation between triphenyl(allenyl)lead and phenyllithium was required to generate the reactive organolithium compound (Scheme 76). Treating this with benzophenone gave the desired homopropargylic alcohol 1,1-diphenyl-3-butyn-1-ol in 69% yield (Scheme 76).

H Ph3Pb

C

H H

+

Ph4Pb

PhLi

C

Li

H

H H

Li

C H

H

H

+

O

Ph

H

Ph Ph HO

C

Ph

Scheme 76

Kang has published extensively on the palladium-catalyzed coupling reactions of organolead compounds with olefins,271 alkynes,272 organostannanes,273 organoboranes,274 and aryl- and alkenyliodonium salts.275

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

995

Plumboles have recently been prepared by the reaction of 1,4-dilithio-1,2,3,4-tetraphenyl-1,3-butadiene with dichlorodiphenylplumbane to give hexaphenylplumbole and spirobiplumbole; these were the first examples to be characterized as fluorescent organolead compounds.276

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64.

Jung, I. N.; Yoo, B. R. Advances in Organometallic Chemistry 2005, 53, 41–59. Spivey, A. C.; Gripton, C. J. G.; Hannah, J. P. Curr. Org. Synth. 2004, 1, 211–226. Yoo, B. R.; Han, J. S. Curr. Org. Chem. 2011, 15, 2743−2757. Braunstein, P.; Knorr, M. J. Organomet. Chem. 1995, 500, 21–38. Hashimoto, H.; Tobita, H. J. Synth. Org. Chem. Jpn. 2012, 70, 131–141. Lewis, L. N.; Sy, K. G.; Donahue, P. E. J. Organomet. Chem. 1992, 427, 165–172. Esteruelas, M. A.; Olivan, M.; Oro, L. A.; Tolosa, J. I. J. Organomet. Chem. 1995, 487, 143–149. Jun, C. H.; Crabtree, R. H. J. Organomet. Chem. 1993, 447, 177–187. Wang, F.; Neckers, D. C. J. Organomet. Chem. 2003, 665, 1–6. Katayama, H.; Taniguchi, K.; Kobayashi, M.; et al. J. Organomet. Chem. 2002, 645, 192–200. Hamze, A.; Provot, O.; Alami, M.; Brion, J. D. Org. Lett. 2005, 7, 5625–5628. Lewis, L. N.; Lewis, N.; Uriarte, R. J. Adv. Chem. Ser. D 1992, 541–549. Gordillo, A.; Forigua, J.; Lopez-Mardomingo, C.; de Jesus, E. Organometallics 2011, 30, 352–355. Lyubov, D. M.; Shavyrin, A. S.; Kurskii, Y. A.; Trifonov, A. A. Russ. Chem. B. 2010, 59, 1765−1770. Pavlov, V. A. Usp. Khim. 2002, 71, 39–56. Roy, A. K. Adv. Organomet. Chem. 2008, 55, 1–59. Varchi, G.; Ojima, I. Curr. Org. Chem. 2006, 10, 1341–1362. Zhang, M.; Zhang, A. Appl. Organomet. Chem. 2010, 24, 751–757. Lim, D. S. W.; Anderson, E. A. Synthesis 2012, 44, 983−1010. Trost, B. M.; Ball, Z. T. Synthesis 2005, 853–887. Yi, C. S. J. Organomet. Chem. 2011, 696, 76–80. Bai, Y.; Peng, J.; Li, J.; Lai, G.; Li, X. Prog. Chem. 2011, 23, 2466–2477. Tertykh, V. A.; Belyakova, L. A. Stud. Surf. Sci. Catal. 1996, 99, 147–189. Kato, N.; Tamura, Y.; Kashiwabara, T.; Sanji, T.; Tanaka, M. Organometallics 2010, 29, 5274–5282. Liu, Y.; Yamazaki, S.; Yamabe, S. J. Org. Chem. 2005, 70, 556–561. Itoh, M.; Kobayashi, M.; Ishikawa, J. Organometallics 1997, 16, 3068–3070. Dunsford, J. J.; Cavell, K. J.; Kariuki, B. J. Organomet. Chem. 2011, 696, 188–194. Bart, S. C.; Lobkovsky, E.; Chirik, P. J. J. Am. Chem. Soc. 2004, 126, 13794–13807. Jimenez, M. V.; Perez-Torrente, J. J.; Bartolome, M. I.; et al. Organometallics 2008, 27, 224–234. Poyatos, M.; Maisse-Francois, A.; Bellemin-Laponnaz, S.; Gade, L. H. Organometallics 2006, 25, 2634–2641. Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2001, 123, 12726–12727. Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2003, 125, 30–31. Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2004, 126, 13942–13944. Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2005, 127, 17644–17655. Trost, B. M.; Ball, Z. T.; Laemmerhold, K. M. J. Am. Chem. Soc. 2005, 127, 10028–10038. Hayashi, A.; Yoshitomi, T.; Umeda, K.; Okazaki, M.; Ozawa, F. Organometallics 2008, 27, 2321–2327. Aronica, L. A.; Schiavi, E.; Evangelisti, C.; et al. J. Catal. 2009, 266, 250–257. Caporusso, A. M.; Aronica, L. A.; Schiavi, E.; et al. J. Organomet. Chem. 2005, 690, 1063–1066. Molander, G. A.; Retsch, W. H. Organometallics 1995, 14, 4570–4575. Asao, N.; Yamamoto, Y. Bull. Chem. Soc. Jpn. 2000, 73, 1071–1087. Field, L. D.; Ward, A. J. J. Organomet. Chem. 2003, 681, 91–97. Goldberg, Y.; Alper, H. Tetrahedron Lett. 1995, 36, 369–372. Dash, A. K.; Gourevich, I.; Wang, J. Q.; et al. Organometallics 2001, 20, 5084–5104. Dash, A. K.; Wang, J. Q.; Eisen, M. S. Organometallics 1999, 18, 4724–4741. Dash, A. K.; Wang, J. X.; Berthet, J. C.; Ephritikhine, M.; Eisen, M. S. J. Organomet. Chem. 2000, 604, 83–98. Okamoto, M.; Kiya, H.; Yamashita, H.; Suzuki, E. Chem. Commun. 2002, 1634–1635. Maddock, S. M.; Rickard, C. E. F.; Roper, W. R.; Wright, L. J. Organometallics 1996, 15, 1793–1803. DelponLacaze, G.; deBattisti, C.; Couret, C. J. Organomet. Chem. 1996, 514, 59–66. Chung, L. W.; Wu, Y. D.; Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2003, 125, 11578–11582. Trost, B. M.; Bartlett, M. J. Org. Lett. 2012, 14, 1322−1325. Arico, C. S.; Cox, L. R. Org. Biomol. Chem. 2004, 2, 2558–2562. Faller, J. W.; D'Alliessi, D. G. Organometallics 2002, 21, 1743–1746. Kamegawa, T.; Saito, M.; Watanabe, T.; et al. J. Mater. Chem. 2011, 21, 12228−12231. Menozzi, C.; Dalko, P. I.; Cossy, J. J. Org. Chem. 2005, 70, 10717–10719. Martin, M.; Sola, E.; Lahoz, F. J.; Oro, L. A. Organometallics 2002, 21, 4027–4029. Baruah, J. B.; Osakada, K.; Yamamoto, T. J. Mol. Catal. A Chem. 1995, 101, 17–24. Takeuchi, R.; Tanouchi, N. J. Chem. Soc. Perkin Trans. 1 1994, 2909–2913. Takeuchi, R.; Nitta, S.; Watanabe, D. J. Org. Chem. 1995, 60, 3045–3051. Sato, A.; Kinoshita, H.; Shinokubo, H.; Oshima, K. Org. Lett. 2004, 6, 2217–2220. Zeng, J. Y.; Hsieh, M. H.; Lee, H. M. J. Organomet. Chem. 2005, 690, 5662–5671. Busetto, L.; Cassani, M. C.; Femoni, C.; et al. Organometallics 2011, 30, 5258–5272. Krueger, A.; Albrecht, M. Chem. Eur. J. 2012, 18, 652–658. Rivera, G.; Elizalde, O.; Roa, G.; Montiel, I.; Bernes, S. J. Organomet. Chem. 2012, 699, 82–86. Ojima, I.; Li, Z. Y.; Donovan, R. J.; Ingallina, P. Inorg. Chim. Acta 1998, 270, 279–284.

996

65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137.

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

Yoshikai, N.; Yamanaka, M.; Ojima, I.; Morokuma, K.; Nakamura, E. Organometallics 2006, 25, 3867–3875. Aronica, L. A.; Terreni, S.; Caporusso, A. M.; Salvadori, P. Eur. J. Org. Chem. 2001, 4321–4329. Biffis, A.; Conte, L.; Tubaro, C.; et al. J. Organomet. Chem. 2010, 695, 792–798. Matsuda, I.; Ogiso, A.; Sato, S.; Izumi, Y. J. Am. Chem. Soc. 1989, 111, 2332–2333. Matsuda, I.; Fukuta, Y.; Tsuchihashi, T.; Nagashima, H.; Itoh, K. Organometallics 1997, 16, 4327–4345. Alonso, F.; Buitrago, R.; Moglie, Y.; et al. J. Organomet. Chem. 2011, 696, 368–372. Lu, C.; Gu, S.; Chen, W.; Qiu, H. Dalton Trans. 2010, 39, 4198–4204. McLaughlin, M. G.; Cook, M. J. Chem. Commun. 2011, 47, 11104–11106. Caporusso, A. M.; Barontini, S.; Pertici, P.; Vitulli, G.; Salvadori, P. J. Organomet. Chem. 1998, 564, 57–59. Schwieger, S.; Herzog, R.; Wagner, C.; Steinborn, D. J. Organomet. Chem. 2009, 694, 3548–3558. Lewis, L. N.; Sy, K. G.; Bryant, G. L.; Donahue, P. E. Organometallics 1991, 10, 3750–3759. Hu, J. J.; Li, F.; Hor, T. S. A. Organometallics 2009, 28, 1212–1220. RiveraClaudio, M.; Rozell, J.; RamirezOliva, E.; Cervantes, J.; Pannell, K. H. J. Organomet. Chem. 1996, 521, 267–270. Chauhan, M.; Hauck, B. J.; Keller, L. P.; Boudjouk, P. J. Organomet. Chem. 2002, 645, 1–13. Blug, M.; Le Goff, X.-F.; Mezailles, N.; Le Floch, P. Organometallics 2009, 28, 2360–2362. Berthon-Gelloz, G.; Schumers, J.-M.; De Bo, G.; Marko, I. E. J. Org. Chem. 2008, 73, 4190–4197. De Bo, G.; Berthon-Gelloz, G.; Tinant, B.; Marko, I. E. Organometallics 2006, 25, 1881–1890. Kim, D. H.; Park, Y. A. W. Bull. Korean Chem. Soc. 2006, 27, 27–28. Sumida, Y.; Kato, T.; Yoshida, S.; Hosoya, T. Org. Lett. 2012, 14, 1552−1555. Motoda, D.; Shinokubo, H.; Oshima, K. Synlett 2002, 1529–1531. Kawanami, Y.; Yamamoto, K. Synlett 1995, 1232–1234. Kawasaki, Y.; Ishikawa, Y.; Igawa, K.; Tomooka, K. J. Am. Chem. Soc. 2011, 133, 20712−20715. Ojima, I.; Clos, N.; Donovan, R. J.; Ingallina, P. Organometallics 1990, 9, 3127–3133. Adams, R. D.; Bunz, U.; Captain, B.; Fu, W.; Steffen, W. J. Organomet. Chem. 2000, 614, 75–82. Sore, H. F.; Blackwell, D. T.; MacDonald, S. J. F.; Spring, D. R. Org. Lett. 2010, 12, 2806−2809. Sore, H. F.; Boehner, C. M.; Laraia, L.; et al. Org. Biomol. Chem. 2011, 9, 504–515. Zipoli, F.; Bernasconi, M. J. Phys. Chem. B 2006, 110, 23403–23409. Stewart, M. P.; Buriak, J. M. J. Am. Chem. Soc. 2001, 123, 7821–7830. Cui, Y.; Tu, W.; Floreancig, P. E. Tetrahedron 2010, 66, 4867−4873. Rooke, D. A.; Ferreira, E. M. J. Am. Chem. Soc. 2010, 132, 11926–11928. Rooke, D. A.; Ferreira, E. M. Angew. Chem. Int. Ed. 2012, 51, 3225−3230. Molander, G. A.; Retsch, W. H. J. Am. Chem. Soc. 1997, 119, 8817–8825. Molander, G. A.; Retsch, W. H. J. Org. Chem. 1998, 63, 5507–5516. Molander, G. A.; Corrette, C. P. J. Org. Chem. 1999, 64, 9697–9703. Rastaetter, M.; Zulys, A.; Roesky, P. W. Chem. Eur. J. 2007, 13, 3606–3616. Chaulagain, M. R.; Mahandru, G. M.; Montgomery, J. Tetrahedron 2006, 62, 7560–7566. Berding, J.; van Paridon, J. A.; van Rixel, V. H. S.; Bouwman, E. Eur. J. Inorg. Chem. 2011, 2450–2458. Stoelzel, M.; Praesang, C.; Inoue, S.; Enthaler, S.; Driess, M. Angew. Chem. Int. Ed. 2012, 51, 399–403. Tokunaga, Y.; Ohiwa, N.; Ohta, G.; et al. Heterocycles 2009, 77, 1045–1056. Furstner, A.; Radkowski, K. Chem. Commun. 2002, 2182–2183. Diez-Gonzalez, S.; Blanco, L. J. Organomet. Chem. 2008, 693, 2033–2040. Pidaparthi, R. R.; Welker, M. E. Tetrahedron Lett. 2007, 48, 7853–7856. Denmark, S. E.; Wang, Z. G. Org. Lett. 2001, 3, 1073–1076. Shimamoto, T.; Chimori, M.; Sogawa, H.; et al. Bull. Chem. Soc. Jpn. 2007, 80, 1814–1823. Wang, X.; Chakrapani, H.; Madine, J. W.; Keyerleber, M. A.; Widenhoefer, R. A. J. Org. Chem. 2002, 67, 2778–2788. Shimamoto, T.; Hirano, T.; Nishimoto, H.; Yamamoto, K. Chem. Lett. 2006, 35, 846–847. Mori, A.; Takahisa, E.; Yamamura, Y.; et al. Organometallics 2004, 23, 1755–1765. Ueda, T.; Shiotsuki, M.; Sanda, F. Polymer 2011, 52, 3570–3579. Michalska, Z. M.; Strzelec, K. J. Mol. Catal. Chem. 2001, 177, 89–104. Ochiai, B.; Tomita, I.; Endo, T. Polym. Bull. 2004, 51, 263–269. Phan, S. T.; Lim, W. C.; Han, J. S.; Jung, I. N.; Yoo, B. R. J. Organomet. Chem. 2006, 691, 604–610. Katayama, H.; Nagao, M.; Moriguchi, R.; Ozawa, F. J. Organomet. Chem. 2003, 676, 49–54. Sasabe, H.; Kihara, N.; Mizuno, K.; Ogawa, A.; Takata, T. Tetrahedron Lett. 2005, 46, 3851–3853. Baxter, R. D.; Montgomery, J. J. Am. Chem. Soc. 2008, 130, 9662–9663. Ng, A.; Ciampi, S.; James, M.; Harper, J. B.; Gooding, J. J. Langmuir 2009, 25, 13934–13941. Choi, H. C.; Buriak, J. M. Chem. Mater. 2000, 12, 2151–2156. Hurley, P. T.; Ribbe, A. E.; Buriak, J. M. J. Am. Chem. Soc. 2003, 125, 11334–11339. Ciampi, S.; Boecking, T.; Kilian, K. A.; et al. Langmuir 2007, 23, 9320–9329. Ciampi, S.; Le Saux, G.; Harper, J. B.; Gooding, J. J. Electroanalysis 2008, 20, 1513–1519. Ng, C. C. A.; Ciampi, S.; Harper, J. B.; Gooding, J. J. Surface Sci. 2010, 604, 1388–1394. Guan, B.; Ciampi, S.; Le Saux, G.; et al. Langmuir 2011, 27, 328–334. Nievas, A.; Gonzalez, J. J.; Hernandez, E.; et al. Organometallics 2011, 30, 1920−1929. Huang, K.; Duclairoir, F.; Pro, T.; et al. Chemphyschem 2009, 10, 963–971. Liu, H.; Duclairoir, F.; Fleury, B.; et al. Dalton Trans. 2009, 3793–3799. Marciniec, B. Coord. Chem. Rev. 2005, 249, 2374–2390. Lim, D. S. W.; Anderson, E. A. Org. Lett. 2011, 13, 4806−4809. Troegel, D.; Stohrer, J. Coord. Chem. Rev. 2011, 255, 1440–1459. Wawrzynczak, A.; Dutkiewicz, M.; Gulinski, J.; et al. Catal. Today 2011, 169, 69–74. Bai, Y.; Peng, J.; Li, J.; Lai, G. Appl. Organomet. Chem. 2010, 25, 400–405. Bandari, R.; Buchmeiser, M. R. Catal. Sci. Technol. 2012, 2, 220–226. Brunner, H. Angew. Chem. Int. Ed. Eng. 1983, 22, 897–907. Gibson, S. E.; Rudd, M. Adv. Synth. Catal. 2007, 349, 781–795. Atienza, C. C. H.; Tondreau, A. M.; Weller, K. J.; et al. ACS Catal. 2012, 2, 2169−2172.

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

997

138. Chirik, P. J.; Tondreau, A. M.; Delis, J. G. P.; et al. (Momentive Performance Materials Inc.). University of Cornell. US2012130106-A1; WO2012071358-A2; WO2012071358-A3, 2012. 139. Delis, J. G. P.; Chirik, P. J.; Tondreau, A. M. (Momentive Performance Materials Inc.). University of Cornell. WO2011006049-A1; US2011009565-A1; TW201111041-A; KR2012023148-A; EP2451818-A1; IN201200033-P3; CN102471354-A; JP2012532885-W, 2012. Delis J. G. P.; Chirik P. J.; Tondreau A. M. (General Electric Co.). Patent number WO2011006049-A1, 2011. 140. Tondreau, A. M.; Atienza, C. C. H.; Darmon, J. M.; et al. Organometallics 2012, 31, 4886–4893. 141. Tondreau, A. M.; Atienza, C. C. H.; Weller, K. J.; et al. Science 2012, 335, 567−570. 142. Tondreau, A. M.; Chirik, P. J.; Delis, J. G. P.; et al. (Momentive Performance Materials Inc.). University of Cornell. US2012130021-A1; WO2012071359-A1; WO2012071360-A1; TW201235103-A; TW201235355-A, 2012. 143. Zhao, Q.; Curran, D. P.; Malacria, M.; et al. Chem. Eur. J. 2011, 17, 9911−9914. 144. Imlinger, N.; Wurst, K.; Buchmeiser, M. R. Monatsh. Chem. 2005, 136, 47–57. 145. Kisanga, P.; Goj, L. A.; Widenhoefer, R. A. J. Org. Chem. 2001, 66, 635–637. 146. Pei, T.; Widenhoefer, R. A. Tetrahedron Lett. 2000, 41, 7597–7600. 147. Perch, N. S.; Pei, T.; Widenhoefer, R. A. J. Org. Chem. 2000, 65, 3836–3845. 148. Perch, N. S.; Widenhoefer, R. A. J. Am. Chem. Soc. 1999, 121, 6960–6961. 149. Stengone, C. N.; Widenhoefer, R. A. Tetrahedron Lett. 1999, 40, 1451–1454. 150. Widenhoefer, R. A.; DeCarli, M. A. J. Am. Chem. Soc. 1998, 120, 3805–3806. 151. Widenhoefer, R. A.; Vadehra, A. Tetrahedron Lett. 1999, 40, 8499–8502. 152. Lu, B.; Falck, J. R. J. Org. Chem. 2010, 75, 1701–1705. 153. Li, J.; Peng, J.; Bai, Y.; Lai, G.; Li, X. J. Organomet. Chem. 2011, 696, 2116−2121. 154. Taige, M. A.; Ahrens, S.; Strassner, T. J. Organomet. Chem. 2011, 696, 2918−2927. 155. Zhao, J.; Sun, X.; Xie, B.; et al. Res. Chem. Intermediat. 2009, 35, 625–631. 156. Gribkov, D. V.; Hampel, F.; Hultzsch, K. C. Eur. J. Inorg. Chem. 2004, 4091–4101. 157. Jung, D. E.; Han, J. S.; Yoo, B. R. J. Organomet. Chem. 2011, 696, 3687–3692. 158. Pop, R.; Cui, J. L.; Adriaenssens, L.; Comte, V.; Le Gendre, P. Synlett 2011, 679−683. 159. Luken, C.; Moberg, C. Org. Lett. 2008, 10, 2505–2508. 160. Shibata, T.; Kadowaki, S.; Takagi, K. Organometallics 2004, 23, 4116–4120. 161. Alonso, F.; Buitrago, R.; Moglie, Y.; Sepulveda-Escribano, A.; Yus, M. Organometallics 2012, 31, 2336−2342. 162. Palframan, M. J.; Parsons, A. F.; Johnson, P. Synlett 2011, 2811–2814. 163. Bournel, F.; Gallet, J. J.; Pierucci, D.; et al. J. Phys. Chem. C 2011, 115, 14827−14833. 164. Lee, M. V.; Scipioni, R.; Boero, M.; Silvestrelli, P. L.; Ariga, K. Phys. Chem. Chem. Phys. 2011, 13, 4862–4867. 165. Qin, G.; Santos, C.; Zhang, W.; et al. J. Am. Chem. Soc. 2010, 132, 16432–16441. 166. Li, Y.; Santos, C. M.; Kumar, A.; et al. Chem. Eur. J. 2011, 17, 2656–2665. 167. Rijksen, B.; van Lagen, B.; Zuilhof, H. J. Am. Chem. Soc. 2011, 133, 4998–5008. 168. Calder, S.; Boies, A.; Lei, P.; Girshick, S.; Roberts, J. Chem. Mater. 2011, 23, 2917–2921. 169. Kelly, J. A.; Shukaliak, A. M.; Fleischauer, M. D.; Veinot, J. G. C. J. Am. Chem. Soc. 2011, 133, 9564–9571. 170. Jariwala, B. N.; Dewey, O. S.; Stradins, P.; Ciobanu, C. V.; Agarwal, S. ACS Appl. Mater. Inter. 2011, 3, 3033–3041. 171. Lacombe, F.; Radkowski, K.; Seidel, G.; Furstner, A. Tetrahedron 2004, 60, 7315–7324. 172. Micoine, K.; Fuerstner, A. J. Am. Chem. Soc. 2010, 132, 14064−14066. 173. Lehr, K.; Mariz, R.; Leseurre, L.; Gabor, B.; Fuerstner, A. Angew. Chem. Int. Ed. 2011, 50, 11373−11377. 174. Fuerstner, A.; Bonnekessel, M.; Blank, J. T.; et al. Chem. Eur. J. 2007, 13, 8762–8783. 175. Bressy, C.; Bargiggia, F.; Guyonnet, M.; Arseniyadis, S.; Cossy, J. Synlett 2009, 565–568. 176. Casas-Arce, E.; ter Horst, B.; Feringa, B. L.; Minnaard, A. J. Chem. Eur. J. 2008, 14, 4157–4159. 177. Denmark, S. E.; Liu, J. H. C.; Muhuhi, J. M. J. Org. Chem. 2011, 76, 201−215. 178. Smith, N. D.; Mancuso, J.; Lautens, M. Chem. Rev. 2000, 100, 3257–3282. 179. Pereira, O. Z.; Chan, T. H. Tetrahedron Lett. 1995, 36, 8749–8752. 180. Gevorgyan, V.; Liu, J. X.; Yamamoto, Y. Chem. Commun. 1998, 37–38. 181. Gallagher, W. P.; Terstiege, I.; Maleczka, R. E. J. Am. Chem. Soc. 2001, 123, 3194–3204. 182. Hamze, A.; Veau, D.; Provot, O.; Brion, J.-D.; Alami, M. J. Org. Chem. 2009, 74, 1337–1340. 183. Czelusniak, I.; Jachimowska, M.; Szymanska-Buzar, T. J. Organomet. Chem. 2011, 696, 3023−3028. 184. Ghosh, B.; Maleczka, R. E., Jr. Tetrahedron Lett. 2011, 52, 5285–5287. 185. Mirzayans, P. M.; Pouwer, R. H.; Williams, C. M.; Bernhardt, P. V. Tetrahedron 2009, 65, 8297–8305. 186. Mirzayans, P. M.; Pouwer, R. H.; Williams, C. M. Org. Lett. 2008, 10, 3861–3863. 187. Jana, A.; Roesky, H. W.; Schulzke, C.; Doering, A. Angew. Chem. Int. Ed. 2009, 48, 1106–1109. 188. Jana, A.; Roesky, H. W.; Schulzke, C. Inorg. Chem. 2009, 48, 9543–9548. 189. Ocampo, R. A.; Mandolesi, S. D.; Koll, L. C. ARKIVOC 2011, 195–209. 190. Cai, M.; Fang, X.; Dai, R.; Zha, L. Appl. Organomet. Chem. 2009, 23, 229–234. 191. Miura, K.; Wang, D.; Matsumoto, Y.; Hosomi, A. Org. Lett. 2005, 7, 503–505. 192. Wesquet, A. O.; Kazmaier, U. Angew. Chem. Int. Ed. 2008, 47, 3050–3053. 193. Andrews, I. P.; Kwon, O. Tetrahedron Lett. 2008, 49, 7097–7099. 194. Faraoni, M. A. B.; Gerbino, D. C.; Podesta, J. C. J. Organomet. Chem. 2008, 693, 1877–1885. 195. Miao, R.; Li, S.; Chiu, P. Tetrahedron 2007, 63, 6737–6740. 196. Nielsen, T. E.; Tanner, D. J. Org. Chem. 2002, 67, 6366–6371. 197. Cai, M.; Wang, Y.; Hao, W. Eur. J. Org. Chem. 2008, 2983–2988. 198. Yu, L. M.; Hao, W. Y.; Cai, M. Z. Chin. Chem. Lett. 2008, 19, 1047–1050. 199. Spiteri, C.; Burnley, J.; Moses, J. E. Synlett 2011, 2533–2536. 200. Hayashi, N.; Kusano, K.; Sekizawa, S.; et al. Chem. Commun. 2007, 4913–4915. 201. Kavanagh, Y.; Ford, L.; Schiesser, C. H. Organometallics 2011, 30, 4387–4392. 202. Lautens, M.; Klute, W. Angew. Chem. Int. Ed. 1996, 35, 442–445. 203. Gevorgyan, V.; Liu, J. X.; Yamamoto, Y. J. Org. Chem. 1997, 62, 2963–2967. 204. Suennemann, H. W.; Banwell, M. G.; de Meijere, A. Eur. J. Org. Chem. 2007, 3879–3893. 205. Yao, F.; You, S.; Cai, M. Heteroatom Chem. 2009, 20, 218–223. 206. Kerric, G.; Le Grognec, E.; Fargeas, V.; et al. J. Organomet. Chem. 2010, 695, 1414−1424.

998

207. 208. 209. 210. 211. 212. 213. 214. 215. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234. 235. 236. 237. 238. 239. 240. 241. 242. 243. 244. 245. 246. 247. 248. 249. 250. 251. 252. 253. 254. 255. 256. 257. 258. 259. 260. 261. 262. 263. 264. 265. 266. 267. 268. 269. 270. 271. 272. 273. 274. 275. 276.

Hydrometallation Group 4 (Si, Sn, Ge, and Pb)

Chakraborty, T. K.; Goswami, R. K.; Sreekanth, M. Tetrahedron Lett. 2007, 48, 4075–4078. Kerr, D. J.; Hamel, E.; Jung, M. K.; Flynn, B. L. Bioorg. Med. Chem. 2007, 15, 3290–3298. Rasolofonjatovo, E.; Provot, O.; Hamze, A.; et al. Eur. J. Med. Chem. 2010, 45, 3617–3626. Candy, M.; Audran, G.; Bienayme, H.; Bressy, C.; Pons, J.-M. Org. Lett. 2009, 11, 4950–4953. Weinert, C. S. Germanium Organometallics. In: Comprehensive Organometallic Chemistry III; Crabtree, R. H., Mingos, D. M. P., Editors-in-Chief; Elsevier: Oxford, 2007, Chapter 3.13; pp 699−808. Toal, S. J.; Sohn, H.; Zakarov, L. N.; et al. Organometallics 2005, 24, 3081–3087. Klein, B.; Neumann, W. P.; Weisbeck, M. P.; Wienken, S. J. Organomet. Chem. 1993, 446, 149–159. Jana, A.; Ghoshal, D.; Roesky, H. W.; et al. J. Am. Chem. Soc. 2009, 131, 1288–1293. Jana, A.; Roesky, H. W.; Schulzke, C. Dalton Trans. 2010, 39, 132–138. Choong, S. L.; Woodul, W. D.; Schenk, C.; et al. Organometallics 2011, 30, 5543–5550. Chatgilialoglu, C.; Ballestri, M.; Escudie, J.; Pailhous, I. Organometallics 1999, 18, 2395–2397. Iwata, A.; Toyoshima, Y.; Hayashida, T.; et al. J. Organomet. Chem. 2003, 667, 90–95. Wang, Z. H.; Wnuk, S. F. J. Org. Chem. 2005, 70, 3281–3284. Wnuk, S. F.; Garcia, P. I.; Wang, Z. Z. Org. Lett. 2004, 6, 2047–2049. Schwier, T.; Gevorgyan, V. Org. Lett. 2005, 7, 5191–5194. Taniguchi, M.; Oshima, K.; Utimoto, K. Chem. Lett. 1993, 1751–1754. Dirnens, V.; Barabanov, D. I.; Liepins, E.; Ignatovich, L. M.; Lukevics, E. J. Organomet. Chem. 1992, 435, 257–263. Itazaki, M.; Kamitani, M.; Nakazawa, H. Chem. Commun. 2011, 47, 7854−7856. Esteruelas, M. A.; Lahoz, F. J.; Onate, E.; Oro, L. A.; Rodriguez, L. Organometallics 1996, 15, 3670–3678. Esteruelas, M. A.; Martin, M.; Oro, L. A. Organometallics 1999, 18, 2267–2270. Widenhoefer, R. A.; Vadehra, A.; Cheruvu, P. K. Organometallics 1999, 18, 4614–4618. David-Quillot, F.; Thiery, V.; Abarbri, M.; et al. Main Group Met. Chem. 2007, 30, 235–244. Kinoshita, H.; Shinokubo, H.; Oshima, K. J. Am. Chem. Soc. 2002, 124, 4220–4221. Yamashita, H.; Channasanon, S.; Uchimaru, Y. Chem. Lett. 2006, 35, 398–399. Miura, K.; Ootsuka, K.; Hosomi, A. J. Organomet. Chem. 2007, 692, 514–519. Curran, D. P.; Gualtieri, G. Synlett 2001, 1038–1041. Kinoshita, H.; Nakamura, T.; Kakiya, H.; et al. Org. Lett. 2001, 3, 2521–2524. Tanaka, S.; Nakamura, T.; Yorimitsu, H.; Shinokubo, H.; Oshima, K. Org. Lett. 2000, 2, 1911–1914. Yorimitsu, H.; Oshima, K. Inorg. Chem. Commun. 2005, 8, 131–142. Nakamura, T.; Tanaka, S.; Yorimitsu, H.; Shinokubo, H.; Oshima, K. CR Acad. Sci. Chim. 2001, 4, 461–470. Lakhtin, V. G.; Knyazev, S. P.; Pavlov, K. V.; et al. Russ. J. Gen. Chem. 2008, 78, 898–902. Marciniec, B.; Lawicka, H.; Majchrzak, M.; Kubicki, M.; Kownacki, I. Chem. Eur. J. 2006, 12, 244–250. El Kadib, A.; Feddouli, A.; Riviere, P.; et al. Organometallics 2005, 24, 446–454. Matsuda, T.; Kadowaki, S.; Yamaguchi, Y.; Murakami, M. Organic Lett. 2010, 12, 1056–1058. Shoda, S.; Iwata, S.; Yajima, K.; et al. Tetrahedron 1997, 53, 15281–15295. Holmberg, V. C.; Korgel, B. A. Chem. Mater. 2010, 22, 3698–3703. Karpenko, R. G.; Kolesnikov, S. P. Russ. Chem. Bull. 1998, 47, 180–182. El Kadib, A.; Castel, A.; Delpech, F.; et al. Inorg. Chim. Acta 2004, 357, 1256–1264. Marciniec, B.; Lawicka, H. Appl. Organomet. Chem. 2008, 22, 510–515. Furukawa, N.; Kourogi, N.; Seki, Y.; Kakiuchi, F.; Murai, S. Organometallics 1999, 18, 3764–3767. Choi, K.; Buriak, J. M. Langmuir 2000, 16, 7737–7741. Hanrath, T.; Korgel, B. A. J. Am. Chem. Soc. 2004, 126, 15466–15472. Choi, H. C.; Buriak, J. M. Chem. Commun. 2000, 1669–1670. Finet, J.-P. Lead in Comprehensive Organometallic Chemistry III From Fundamentals to Applications. In Applications I: Main Group Compounds in Organic Synthesis; Crabtree, R. H.; Mingos, D. M. P., Eds.; Elsevier, 2007, Vol. 9, Chapter 9.09; pp 381−424. Jousseaume, B. Mikrochim. Acta 1992, 109, 5–12. Juenge, E. C.; Hawkes, S. J.; Snider, T. E. J. Organomet. Chem. 1973, 51, 189–195. Puddephatt, R. J.; Thistlethwaite, G. H. J. Organomet. Chem. 1972, 40, 135–138. Puddephatt, R. J.; Thistlethwaite, G. H. J. Chem. Soc., Dalton Trans. 1972, 570–572. Zavgorodnii, V. S.; Grigoreva, N. D.; Petrov, A. A. Zh. Obsh. Khim. 1981, 51, 2155–2156. Siebert, W.; Davidsohn, W. E.; Henry, M. C. J. Organomet. Chem. 1968, 15, 69–75. Siebert, W.; Davidsohn, W. E.; Henry, M. C. J. Organomet. Chem. 1969, 17, 65–70. Pant, B. C.; Davidsohn, W. E.; Henry, M. C. J. Organomet. Chem. 1969, 16, 413–417. Steingross, W.; Zeil, W. J. Organomet. Chem. 1966, 6, 109–116. Findeiss, W.; Davidsohn, W.; Henry, M. C. J. Organomet. Chem. 1967, 9, 435–441. Davies, A. G.; Puddephatt, R. J. J. Chem. Soc., C 1968, 317. Pant, B. C.; Reiff, H. F. J. Organomet. Chem. 1968, 15, 65–68. Moloney, M. G.; Pinhey, J. T.; Roche, E. G. Tetrahedron Lett. 1986, 27, 5025–5028. Moloney, M. G.; Pinhey, J. T.; Roche, E. G. J. Chem. Soc. Perkin Trans. 1 1989, 333–341. Hashimoto, S. I.; Miyazaki, Y.; Shinoda, T.; Ikegami, S. J. Chem. Soc. Chem. Commun. 1990, 1100–1102. Hashimoto, S.; Miyazaki, Y.; Ikegami, S. Synlett 1996, 324–326. Hashimoto, S.; Shinoda, T.; Ikegami, S. J. Chem. Soc. Chem. Commun. 1988, 1137–1139. Parkinson, C. J.; Hambley, T. W.; Pinhey, J. T. J. Chem. Soc. Perkin Trans. 1 1997, 1465–1468. Fedorov, A. Y.; Finet, J. P.; Ganina, O. G.; Naumov, M. I.; Shavyrin, A. S. Russ. Chem. Bull. 2005, 54, 2602–2611. Moloney, M. G.; Pinhey, J. T.; Stoermer, M. J. J. Chem. Soc. Perkin Trans. 1 1990, 2645–2655. Kang, S. K.; Choi, S. C.; Ryu, H. C.; Yamaguchi, T. J. Org. Chem. 1998, 63, 5748–5749. Kang, S. K.; Ryu, H. C.; Lee, S. H. Synth. Commun. 2001, 31, 1059–1064. Kang, S. K.; Ryu, H. C.; Choi, S. C. Chem. Commun. 1998, 1317–1318. Kang, S. K.; Ryu, H. C.; Son, H. J. Synlett 1998, 771–773. Kang, S. K.; Yamaguchi, T.; Ho, P. S.; Kim, W. Y.; Ryu, H. C. J. Chem. Soc. Perkin Trans. 1 1998, 841–842. Saito, M.; Sakaguchi, M.; Tajima, T.; Ishimura, K.; Nagase, S. Phosphorus Sulfur Silicon Relat. Elem. 2010, 185, 1068−1076.