Chapter 4 Four-membered ring systems

92

Chapter 4 Four-membered ring systems Benito Alcaide Departamento de Quimica Organica Org~knica1.I. Facultad de Quimica, Universidad Complutense de Madrid, 28040-Madrid, Spain [email protected] Pedro Almendros Instituto de Quimica Organica Orggmica General, General CSIC, CSIC, Juan de la Cierva 3, 28006-Madrid, Spain lnstituto [email protected]

4.1

INTRODUCTION INTRODUCTION

The importance of four-membered heterocycles in many fields of Science (including Organic Chemistry, Inorganic Chemistry, Medicinal Chemistry, and Material Science) can hardly be overemphasized, and justifies a long lasting effort to work out new synthetic protocols. Condensing the vast amount of published material to less than 20 pages is an extremely demanding task. This, obviously, can only be done by strict selection and by applying a very dense style of writing. Oxygen- and nitrogen-containing heterocycles, in particular ~-lactams, [3-1actams, dominate the field in terms of the number of publications. This chapter covers selected relevant aspects in this area.

4.2

AZETIDINES, 3-AZETIDINONES, AND AZETIDINES, AZETINES, AZETINES, 3-AZETIDINONES, AND DIAZETINES DIAZETINES

2-( I-Adamantyl)-2-methyl-azetidines have been synthesized and tested for their 2-(1-Adamantyl)-2-methyl-azetidines antiviral activity against influenza, being markedly active against influenza A H2N2 virus <06BMC3341>. The biological activities of of an aqueous fraction extracted from Polygonatum of odoratum of L-2-azetidinecarboxylic acid 1, purified from the extract, on the growth of several types of algae have been tested <06MI1>. <06MII>. Electrophilic amination of of ketones and aldehydes in the presence of dibenzyl azodicarboxylate in dichloromethane, using L-2azetidinecarboxylic acid 1 as a catalyst, has been described <06TL 1117>. The structure of of 3fluoroazetidinium hydrochloride 2 has been explored both by X-ray diffraction analysis and DFT calculations, and the conformation of of this molecule was shown to be significantly C-F'" W§ interaction <06CC3190>. Aqueous phosphoric acid influenced by the through space C-F ......N (85 wt%) is an effective, environmentally benign reagent for the deprotection of of tert-butyl l-benzhydrylazetidin-3-ylcarbamate 3 <06JOC9045>. The carbamates, including tert-butyl 1-benzhydrylazetidin-3-ylcarbamate of aminonitrofluorenes such as azetidine derivative 4, structure-property relationship of C-N bond formation between the free amine synthesized by copper-mediated Ullmann-type C-N and the corresponding iodoarene, has been described <06S3425>. tert-Butyl hypoiodite (tBuOI) has been found to be a powerful reagent for the cyclization of of N-alkenylamides leading to a variety of of N-heterocycles, including 2-(iodomethyl)-l-tosylazetidine 2-(iodomethyl)-I-tosylazetidine 5, under extremely mild conditions <06OL3335>. <060L3335>.

93

Four-membered ring ring systems systems

BocHN

L--N

"H

I

1

'H

_

qY y

2 H Cl

33

Ph ,Ph

Ts

Ph Ph

4

5

N,N-Carbonyldiimidazole-mediated N,N'-Carbonyldiimidazole-mediated cyclization of amino alcohols to substituted azetidines has been developed <06JOC4147>. N-Tosyl-3-halo-3-butenylamines underwent CuI/N,N'-dimethylethylenediamine to efficient Ullmann-type coupling with the catalysis of CuIlN,N-dimethylethylenediamine afford 2-alkylideneazetidines 6, which could be readily converted into the corresponding ~­ 13<06OL5365>. 6-Vinyl oxazinanones undergo catalytic, lactams by oxidation with 0O33 <060L5365>. diastereoselective, decarboxylative ring contraction to form vinyl azetidines 7 in good yield <060L3211>. <06OL3211>. N-(Alkylidene or l-arylmethylidene)-2-propenylamines 1-arylmethylidene)-2-propenylamines have been 1-arylmethylidene)-3-bromo-2regiospecifically functionalized to novel N-(alkylidene or l-arylmethylidene)-3-bromo-2fluoropropylamines, which proved to be excellent precursors for 3-fluoroazetidines 8 <06JOC7100>. The one-pot formation of 1,3-disubstituted azetidines via the reaction of amine nucleophiles with in situ prepared bis-triflates of 2-substituted-l ,3-propanediols have 2-substituted-l,3-propanediols been demonstrated <06JOC7885>. X

NHTs NHTs

J..A ~R

0

-- Jt i

R

)l

Ts, N

Tss

6 (86-99%)

R2 H

R1

R3''

"Ts

R2 F F-q

-- R;~-T' ii

0 R3

R1 R4 R1~R4 R22 R

. . / RR11

'-./

8

R44 R 7 (60-93%)

Key: i) CuI, DMEDA, dioxane, 100 DC. ~ ii) 5 mol% tool% Pd(PPh Pd(PPh3)4, CH2C12, 3)4, CH 2Cb, RT. The use of monochloroalane has been shown to be an efficient method for the reduction of 4-aryl-3,3-difluoro- as well as trans-2-aryl-3-chloro-~3-1actams to their trans-2-aryl-3-chloro-~-lactams corresponding azetidines 9 <06SL2039; 06T6882>. The resulting chloroazetidines were excellent building blocks for the synthesis of different 3-substituted azetidines through nucleophilic substitution of the chlorine by different carbon, nitrogen, sulfur and oxygen nucleophiles in good to high yields <06T6882>. Azetidine-2-carboxylic acid 10 has been obtained by treating a trichloromethyl ketone-derived Mannich adduct with aqueous NaOH in 1,2-dimethoxyethane. The reaction is considered to proceed via a gem-dichlorooxirane gem-dichlorooxirane intermediate. Intramolecular ring opening affords the azetidine ring <06AG(E)3146>. Enantio- and diastereomerically pure cis-2,3-disubstituted cis-2,3-disubstituted azetidinic amino acid derivatives have been obtained by intramolecular anionic ring-closure <06SL781>. The electroreduction of an aromatic imino ester prepared from (S)-glutamic acid in the presence of chlorotrimethylsilane and triethylamine afforded the four-membered cyclized product 11, a mixed ketal of of cis-2,4-disubstituted cis-2,4-disubstituted azetidine-3-one, stereospecifically <06OL1323>. <060L1323>. The of N-ferrocenylmethyl azetidin-2-yl(diphenyl)methanol in the asymmetric application of ethylation and arylation of of arylaldehydes has been described <06SL3443>. 0II X R 2 X R 2 Ph21~ NH O~ PH,~__]e,.,~/CO2Me o~N, ' ~N ~, .Ph TMSO, R1

,R1 99 (82-97%) (82-97%)

° Ph;:):~CCI3 ~ HO2C,," )=t:h" PPh2ph Ph CCI3 I

H0 2C

II

o O (72%) 10 (72%)

2

,,"

AlH 2Cl, Et20, Et20, 34 ~DC ((X CI), 0 ~DC (X = F). ii) aq. NaOH, NaOH, DME, DME, RT. Key: i) A1H2C1, X -= C1),

"

11 11

Bz

94

B. Alcaide and P. Almendros

Pyranoid and furanoid spiro-N-mesyl azetidines, a new type of water-soluble spiro-Cnucleoside, have been prepared from easily available sugar spiroacetals <06T915>. The first results concerning thermally induced and silver-salt-catalyzed [2+2] [2+2] cycloadditions of imines to (alkoxymethylene)cyclopropanes to afford spirocyclic azetidines 12 have been published <06AG(E)5176>. A two-step reaction sequence using a one-pot a-aminoallylation reaction of spirocyclic diamines, followed by ring-closing metathesis to make a diverse collection of including azetidines, has been developed <06TL8977>. The dominant secondary fragmentation of a series of of 1,3-di- and 1,2,3-trisubstituted N-arylhexahydropyrimidines under electron impact has been described to involve loss of imines or azetidines BHrSMe2 in THF under <06ARK57>. The treatment of an oxopiperazino-~-Iactam oxopiperazino-13-1actam with BH3"SMe2 <06TL89 I I>. The reflux gave rise to the bicyclic azetidine 13 as the major product <06TL8911>. crystalline cis,cis,cis,cis-[5.5.5.4]-I-azafenestrane cis,cis,cis,cis-[5.5.5.4]-l-azafenestrane borane adduct 14 has been efficiently isolated using a Mitsunobu reaction as the key cyclization step followed by treatment with <06JAI1620>. Triplet-sensitized irradiation of 8-thia-9-azatricyclo[7.2.1.0]dodecaBhEt20 <06JA11620>. BF3"Et20 2,4,6,IO-tetraenes in acetone solution gives rise exclusively to tetracyclic suitams 2,4,6,10-tetraenes sultams bearing a bridgehead azetidine ring <06JOC2456>. The synthesis of of novell',2'-azetidine-fused novel l',2'-azetidine-fused bicyclic pyrimidine nucleosides and their transformations to the corresponding phosphoramidite building blocks for automated solid-phase oligonucleotide synthesis has been reported <06JOC299>. It has been shown that the reaction of azetidines with chloroformates gives highly functionalized y-chloroamines 7-chloroamines in high yields and selectivities under mild reaction conditions <060L5501>. <06OL5501>. The ring opening of activated cyclic amines, including fourmembered, foIIowed followed by an intramolecular expansion of of cyclopropanol to cyclobutanone via a carbocation intermediate has been reported. In the case of a N-tosylazetidine ester, the cyclobutanone 15 was formed by treatment of the crude Kulinkovich product with CaS04 CaSO4 <060L4335>. <06OL4335>. A formal [4+2] cycloaddition of 2-aryl-N-tosylazetidines with nitriles in the presence of Zn(OTf)2 has been described for the synthesis of substituted tetrahydropyrimidines <06TL5393>. N-Activated 2-phenylazetidines have been opened regioselectively at the benzylic carbon with various aIIylsilanes allylsilanes or propargylsilane in the presence ofBF of BF3"Et20, carbonylative polymerization 'EhO, providing amino olefins <06TL2205>. The carbonylative polymerization 3 of azetidines tetrahydrofuran azetidines catalyzed catalyzed by [Co(CH3CO)(CO)3P(O-tOI)3], [Co(CH3CO)(CO)3P(o-tol)3], and the participation participation of the tetrahydrofuran polymerization to give ester units polymer products been described described solvent in the polymerization give ester units in the polymer products has been <06AG(E) I29>. Insights into the regioselective nucleophilic ring-opening of azetidinium <06AG(E)129>. ions has been reported <06EJ03479>. <06EJO3479>. It has been shown that efficient ring expansions, selectively leading either to pyrrolidines or to azepanes through [1,2] [1,2] or [2,3] [2,3] sigmatropic <06EJO4214>. 14>. shifts, respectively, can be performed from 2-alkenylazetidinium salts <06EJ042 OR 1

[~/

+

H R~N,Bn

R2

'X=--N

'R~

R2

"R3

12 (71-97%)

..../ o H L~~",,/aH

A 13

-B,F3

-

H H'"

H '''H

cazEt

Q -N

"Ts Ts 14

/ONHTs (t NHTs

N,F ffi B

~)-J aO

15 (70%)

4 2,5-Dimethoxyphenyi. ii) (a) CITi(O-i-Pr)3, Key: i) 10 l0 mol% tool% Ag(fod), MeCN, 30°C. 30 ~ R R 4 == 2,5-Dimethoxyphenyl. C1Ti(O-i-Pr)3, EtMgBr, THF, RT; (b) CaS04, CaSO4, CH CH2C12, 2Cb, RT. The direct, stereoselective conversion of alkynes to N-sulfonylazetidin-2-imines 16 by the initial reaction of of copper(I) acetylides with sulfonyl azides, followed, in situ, by the formal [2+2] [2+2] cycloaddition of of a postulated N-sulfonylketenimine intermediate with a range of imines has been described <06AG(E)3157>. The synthesis of N-alkylated 2-substituted azetidin-3-ones 17 based on a tandem nucleophilic substitution followed by intramolecular Michael reaction of primary amines with alkyl 5-bromo-4-oxopent-2-enoates has been

95

Four-membered ring systems

achieved <06EJ02440>. <06EJO2440>. I-Benzhydryl-3,3-difluoroazetidin-2-thione 1-Benzhydryl-3,3-difluoroazetidin-2-thione has been prepared and converted into y-aminodithioesters 7-aminodithioesters <06S2327>. The [2+2] [2+2] cycloaddition of an N-acyl-2azetine to dichloroketene has been described as a new entry to azetidines fused to cyclobutanes <06TL6377>. The conversion of 4-vinyl-substituted ~-lactams into 4-vinylsubstituted l-azetines 1-azetines 18 and their subsequent reaction with dipheny1cyclopropenone diphenylcyclopropenone resulted in the formation of a highly functionalized 7-azabicyclo[4.2.1]nonene <06TL425>. The xXray structure of an azetine-containing Ni0I) Ni(n) porphyrin derivative has been elucidated <06OBC4059>. <060BC4059>. The preparation of 1,2-diazetidines 19 from 1-(1-hydroxypropan-2yl)hydrazine-l,2-dicarboxylate under very mild conditions has been accomplished AZ-l,2-diazetines <06TL6835>. The regioselective acylation reactions of f121,2-diazetines 20 as well as their rearrangements into 4H-l,3,4-oxadiazines 4H-1,3,4-oxadiazines or pyridazines have been reported <06S514; 06S2885>. It has been proposed that azetine and f13 -1 ,2-diazetine intermediates may be A3-1,2-diazetine <06OL1983>. A stereoselective synthesis of 4involved in the thermolysis of aza-enediynes <060Ll983>. hydroxyalkyl-I,2-oxazetidines hydroxyalkyl-l,2-oxazetidines 21, based on the addition of a-lithiated aryloxiranes to nitrones and subsequent cyclization of the corresponding intermediates in a 4-exo-tet mode, has been described <060L3923>. <06OL3923>. 4 3 R3,~,NSO2 R4 R )=fNS0 2 R

2

N,

R

R 16

4.3

1

°ifCO'R' -{fSEI CO2R2

Ny 1

17

R

2

R

~_~SEt N

R1 18

HQ R1 ArHN~NHAr R2~ 2 p ~ ....Ar HQ R1

R2

R2

ArHNTI-fNHAr

n

RV

N-N 'R

1

19

N-N\

N-N" 20

R Ph""

""Ar O-N 'R 3

O-N,,R3 21

MONOCYCLIC MONOCYCLIC 2-AZETIDINONES 2-AZETIDINONES (~-LACTAMS) ([~-LACTAMS)

[3-1actams has been reviewed The polymer-supported and combinatorial synthesis of ~-lactams <06MI109>. A review on the synthesis of new classes of heterocyclic C-glycoconjugates <06MIl09>. including C-glycosyl ~-lactams [3-1actams by asymmetric multicomponent reactions has appeared [3<06ACR451>. The asymmetric synthesis of active pharmaceutical ingredients including ~­ lactams such as ezetimibe and SCH 58053 has been reviewed <06CRV2734>. An overview on recent developments in isocyanide based multicomponent reactions in applied chemistry including ~-lactam [3-1actam formation, has appeared <06CRV17>. Ketene chemistry including ketene-imine cycloadditions to form ~-lactams, ~-lactams, has been reviewed <06EJO563>. <06EJ0563>. A review on the biocatalytic preparation of ~-amino ~-amino acids including the ring opening of ~-lactams, ~-lactams, has appeared <06T5831>. A convenient and general method of synthesis of NH-~-lactams NH-p-Iactams via Grubbs' carbene-promoted isomerization of the respective N-allyl ~-lactam followed by RuC13-catalyzed RuCh-catalyzed enamide cleavage has been developed <06CEJ2874>. The [2+2] carbonylative cycloaddition of substituted imines with allyl bromide leading to heteroaryl ~­ 13lactams has been reported <06Tl565> <06T1565> <06Tl2064>. <06T12064>. The reaction of enantiopure 4oxoazetidine-2-carbaldehydes with unmodified ketones catalyzed by L-proline or D-proline has been reported to give the corresponding y-amino-p-hydroxy y-amino-[3-hydroxy ketones 22 <06JOC4818>. (l'R,3S,4~)-3-[l'-(tertThe synthesis of the novel carbapenem precursor (1 'R,3S,4S)-3-[1 '-(tertbutyldimethylsilyloxy)ethyl]-4-(cyclopropy1carbonyloxy)azetidin-2-one has been described butyldimethylsilyloxy)ethyl]-4-(cyclopropylcarbonyloxy)azetidin-2-one <06EJO3755>. <06EJ03755>. Ethyl difluoro(trimethylsilyl)acetate and difluoro(trimethylsilyl)acetamides have been used as precursors of 3,3-difluoroazetidinones <06EJ04147>. <06EJO4147>. The activation of the C-CI C-C1 bond of (E)-a-chloroalkylidene-p-lactams (E)-~-chloroalkylidene-[Mactams via the Suzuki cross-coupling reaction to achieve 2-azetidinones 23 has been reported <06MI2114>. The diruthenium-catalyzed formation of p-Iactams [3-1actams via carbenoid C-H insertion of a-diazoacetamides ~-diazoacetamides has been described [3-1actams by Staudinger cycloaddition has <06MI2203>. The synthesis of novel N-sulfonyl ~-lactams

96

B. Alcaide and P. Almendros

been achieved <06MI49>. Results on chiral induction during photocyclization within achiral (z-oxoamides to ~-lactams <06OBC4533>. A model that p-Iactams have been presented <060BC4533>. zeolites of a-oxoamides explains the relative stereoselectivity in the Staudinger reaction based on a kinetic analysis of the cis/trans ratios of reaction products has been proposed <06JA6060>. The effects of solvents, additives, and pathways of ketene generation on the stereoselectivity of the Staudinger reaction have been investigated <06JOC6983>. Staudinger reaction of ethoxycarbonyl(phenylthio)ketene with various imines and subsequent desulfurization reactions have been employed to synthesize 3-ethoxycarbonyl p-Iactams 13-1actams <06JOC8l5>. <06JOC815>. The y-heteroatom directed stereocontrolled Staudinger cycloaddition reaction of of vinylketenes and imines has been achieved <06TL5993>. The diastereoselective synthesis of trans-p-Iactams trans-~-lactams on soluble polymer support has been described <06Sl829>. <06S1829>. Functionalization of N[(silyl)methyl]-p-Iactam [(silyl)methyl]-~-lactam carbanions with carbon electrophiles to give 2-azetidinones 24 has been reported <06JOC6368>. Experimental and theoretical evaluation of the unexpected four-membered (phosphono-p-Iactams (phosphono-13-1actams 25) over six-membered ring formation during the synthesis of azaheterocyclic phosphonates has been documented <06JA6368>. O

~

R3

X 1

22

R2

O/~'--N~ E 24

23

R1 Ph~ ' ~ P ( O R 2 ) 2 O

Ph

.P(OR )2 "R' 25 (62-90%)

Key: i)Nail, i) NaH, THF,~. THF, A. p-Lactam 13-Lactam analogs of combretastatin A-4 have been synthesized and their cytotoxic L1210 leukemia <06MI544>. The design, effects have been evaluated in vitro against LI210 synthesis, and antibacterial activity of 4-alkylidene-azetidin-2-ones 26 as new antimicrobial agents against multidrug-resistant pathogens have been reported <06JMC2804>. (Benzothiazol-2'-yl)azetidin-2-one derivatives have been prepared and screened for antibacterial and antifungal activities <06IJC(B) 1762>. Several pyrimidine-based 2<06IJC(B)1762>. azetidinones have been synthesized and tested for their antibacterial, antifungal and [3-Lactamantituberculosis activities against different microorganisms <06IJC(B)773>. p-Lactamdihydrofuran hybrids 27 have been prepared by a novel palladium0l)-catalyzed palladium(II)-catalyzed 1>. The synthesis heterocyclizative cross-coupling of of two different a-alIenoIs (z-allenols <06AG(E)450 <06AG(E)4501>. of of 3-(aryl)alkenyl-p-Iactams 3-(aryl)alkenyl-13-1actams by application of olefin cross-metathesis on solid support has been reported <060L4783>. <06OL4783>. The synthesis of 3-phenylthio p-Iactams 13-1actams has been carried out using a-diazocarbonyl (z-diazocarbonyl compounds as precursors of ketenes <06S659>. A Lewis acidmediated method for the C3 epimerization of of 3-halo-3-phenylthio-p-Iactams 3-halo-3-phenylthio-13-1actams has been developed <06H749>. The stereoselective synthesis of cis- and trans-3-alkoxy-3trans-3-alkoxy-3phenyl/benzylthioazetidin-2-ones has been described <06T829l>. <06T8291>. p-Lactams 13-Lactams 28 have been isolated as the major products of the reaction of dimethoxycarbene with isocyanates <060L3121>. <06OL3121 >. oO

MeO~o Meo~o

RO~ RO~"~OMe~""'~C02Bn " ~ O ~ cO2BnR2"-I~ OMe

O

H H-O:/~

J--N,..'H o 26 26

o

Key: i) RN=C=O, chlorobenzene, heat.

"R3

R4

MeOOMe MeO MeO~~/OM OMe OMee '+---loMe N,~O i.~ F-T~OMe O)--N'R

27 27

28 (49-68%) (49-68%)

97

Four-membered ring systems

Azetidin-2,3-diones have been used as synthons for the stereoselective synthesis of cis- and trans-C3-alkyl/aryl azetidin-2-ones <06S <06S115>. 115>. It has been reported that the threecomponent reaction of of N-substituted hydroxylamines, aldehydes, and phenylacetylene catalyzed by Cu(!) p-Iactams 29 Cu(I) under neat conditions afforded the corresponding [3-1actams <06MI203>. The reactions of nitrones with terminal alkynes (Kinugasa reaction), catalyzed iPr-trisoxazoline/Cu(C104)z'6H20 [3-1actams in by a chiral iPr-trisoxazoline/Cu(CI04)z·6H zO complex in air, afforded p-lactams reasonable yields with up to 85% ee <06JOC3576>. The direct, palladium-catalyzed, multicomponent synthesis of 3-amido-substituted p-lactams [3-1actams 30 from imines, acid chlorides, 4-Oxoazetidin-2-yl benzoate has and carbon monoxide has been accomplished <06OL3927>. <060L3927>. 4-0xoazetidin-2-yl been resolved by an inclusion complexation with a chiral host compound, (R,R)-(-)-trans4,5-bis(hydroxydiphenylmethyl)-1 ,4-dioxaspiro[4.5]decane <06TA2216>. The Rh(II)4,5-bis(hydroxydiphenylmethyl)-l,4-dioxaspiro[4.5]decane [3-1actams has catalyzed intramolecular C-H insertion of diazoacetamides in water to afford p-lactams been mentioned <06JOC5489>. The reaction of N-acylimidazoles possessing an electronwithdrawing group in the (J. a position with diarylimines produces p-lactams [3-1actams 31 in high yields <06JOC5804>. Studies on the effects of the distance between the aromatic rings and the (J.a[3-1actams derived from stereogenic reaction center on the memory of chirality of p-lactams phenylalanine have been performed <06TL5883>. The synthesis of C3 unsymmetrically [3-1actams as well disubstituted azetidin-2-ones by Lewis acid mediated functionalization of p-lactams as a mechanistic study have been published <06TL5255>. The generation of acyloxyketenes 1,3-dioxolium-4-olates and their reaction with ketenophiles to give from unstable mesoionic 1,3-dioxolium-4-0Iates [3-1actams has been reported <06JOC5162>. A strategy for the [2+2] cycloadducts, including p-lactams synthesis of differently C3-substituted p-lactams ~-lactams involving the reaction of p-lactam ]3-1actam carbocation equivalents with active substrates in the presence of a Lewis acid has been described <06T5054>. A new route to enantiopure 4-aryl-substituted p-lactams ]3-1actams through [3-1actams has lipase-catalyzed enantioselective ring cleavage of the corresponding racemic p-lactams been developed <06MI917>. The enantioselective synthesis of trans-p-lactams trans-~-lactams using a chiral auxiliary under Reformatsky reaction conditions has been described <06SLl 113>. A new <06SL1113>. class of glycoconjugated p-lactams [3-1actams has been accessed by direct glycosidation of a suitable 4alkylidene-azetidin-2-one acceptor with several perbenzylated (N-phenyl)trifluoroacetimidate <06EJ069>. The synthesis and biological evaluation donors activated by catalytic Yb(OTf)3 <06EJO69>. of azido- and aziridino-hydroxy-p-lactams aziridino-hydroxy-[3-1actams through stereo- and regioselective epoxide ring opening have been reported <06JOC9229>. O

Ph ih + R1CHO ~ i O y

-i

R1 " Me 29 (55-95%) (55-95%) 29

R1

-iiii

2 ~ + RScocI __ R2 N.H

R3LN"R1R 2 Ro2~ N , " R1 30 (27--66%) (27-66%) 30

EWG,,~Ar

EWG'" O ' S ~NAr A orN'Arr 31 31

KHC0 3, NaOAc, neat, 70°C. Key: i) MeNHOH'HCl, MeNHOH.HC1, 5 mol % CuCl, CuC1, 2,2'-bipyridine, KHCO3, 70 ~ ii) 1.4 mol% Pd Pdz(dba)3"CHC13, iPr2EtN, MeCN/THF (1:1), 55°C. 55 ~ z(dbakCHCI3, iPrzEtN, p-Lactams [3-Lactams have been used as a synthon for the preparation of a vast array of compounds. It has been reported that the reduction of 4-(haloalkyl)azetidin-2-ones with LiA1H4 LiAIH4 is a powerful method for the synthesis of stereodefined aziridines and azetidines <060Ll101>. <06OL 1101>. However, reduction of 4-(haloalkyl)azetidin-2-ones with chloroalane afforded 2-(haloalkyl)azetidines, which were rearranged to 3,4-cis-disubstituted pyrrolidines and piperidines 32 <060LlI05>. <06OL1105>. During these rearrangements, bicyclic azetidinium intermediates were formed which were ring opened by halides. The synthesis of of a peptide-

98

B. Alcaide and P. Almendros

inhibitor has been described using as the key transformation the aminolysis of a deformylase inhibitor ~-Iactam <06SL3 179>. Reductive ring opening of 2-azetidinones promoted by sodium 13-1actam <06SL3179>. borohydride gives 3-aminopropane-l,2-diols 3-aminopropane-l,2-diols <06TL2209>. The stereoselective conversion of 2-azabicyclo[2.2.0]hex-5-en-3-one into aminodienes has been described <06S633>. Using a 13-1actam ring opening-allene opening-allene sodium methoxide/methanol system, an unprecedented domino ~-Iactam cyclization reaction gives pyrroles 33 <06CC2616>. An enzymatic method has been developed for the synthesis of enantiomeric benzocispentacin and its six- and sevenmembered homologues through the lipase catalyzed enantioselective (£>200) (E>200) ring opening of bicyclic ~-lactams 13-1actams <06CEJ2587>. The ring opening of ~-lactam-fused 13-1actam-fused pinenes gave y-amino alcohols, alcohols, which have been used as catalysts for the enantioselective addition of diethylzinc to aldehydes <06TA199>. A novel procedure has been developed for the preparation of 2,3disubstituted 4, 4,1-benzothiazepines, 13-1actam<06TL5665>. disubstituted l-benzothiazepines, via the ring transformation of a ~-lactam

x

R20~- ~ n X o L I N,R1

R 2 0 ~X i~ R20~ ii lL',.N.-~)n .N.J)n --" ii R1 32 (44-98%) (44-98%)

3 OP 2 R3Hs p~, R

iii R2~R H: Ph ~ 0

N

'R1

2 ~ R

Ph Ph

R~;:..Q-N\ MeOOC R1 ~1 33 (50-54%) (50-54%)

MeOOe

Key: i) AlHzCI, A1H2C1, EtzO, Et20, RT. ii) MeCN, reflux. reflux, iii) MeONa, MeOH, RT.

4.4

SPIROCYCLIC P-LACTAMS ~-LACTAMS FUSED AND SPIROCYCLIC

A review on antibacterial antibacterial natural products including ~-lactam 13-1actam formation has appeared [~-Lactamase nomenclature has been reviewed <06MIlI23>. <06MIl123>. New <06AG(E)5072>. ~-Lactamase 1022> as well as their use as approaches to the inhibition inhibition of metallo-~-lactamases metallo-13-1actamases <06AG(E) <06AG(E)1022> novel weaponry for antibiotic antibiotic resistance in bacteria have been reviewed <06ACR721>. A review on the application of alicyclic ~-amino 13-amino acids in peptide chemistry including enzyme[3-1actams has been published <06CSR323>. An catalyzed ring opening of cycloalkane fused ~-Iactams overview on free radical chemistry including fused ~-lactams [3-1actams has appeared <06CC4055>. Large-scale oxidations oxidations in the pharmaceutical industry including ~-lactams 13-1actams have been reviewed <06CRV2943>. The synthesis and biological activity of spiro ~-Iactams [3-1actams incorporating quinones have been reported <06PS2483>. The Cu(I)-catalyzed Cu(0-catalyzed coupling of [3-1actams with (E)-2-chlorovinyliodides or (E)-2-bromovinyliodides producing the spiranic ~-lactams e n route r o u t e to chartellines chartellines <060Ll779>. <06OL 1779>. corresponding ~-haloenamides has been accomplished en In work directed toward a total synthesis of chartelline A, a strategy investigated to construct 10-membered ring of this marine alkaloid was an intramolecular aldehyde/spiro-~-Iactam aldehyde/spiro-13-1actam the 10-membered cyclocondensation to form the macrocyclic enamide functionality <06JOC3159>. A biosynthetically inspired and strategically designed lO-step 10-step sequence synthesis of (±)(+)chartelline C has been reported <06JAI4028>. <06JA14028>. The synthesis of spiro-linked ~-Iactam­ [3-1actamchartelline dihydropyridines 34 through the cyclization of lithiated lithiated pyridine carboxamides has been I]-lactam 35 in the preparation of achieved <06OL5325>. <060L5325>. The utility of the spiro ~-lactam peptidomimetics as analogues of melanostatin was demonstrated <06JOC7721>. The chirospecific synthesis synthesis of spirocyclic ~-lactams [3-1actams and their characterization as potent type II ~­ [3turn 06CEJ6315>. tum inducing peptide mimetics have been accomplished <06JOC97; 06CEJ63 15>. Yhermolysis spiro[13-1actam-4,2'-oxadiazolines] in the presence of aryl isocyanates Thermolysis of spiroW-lactam-4,2'-oxadiazolines]

99

Four-membered ring systems

afforded both N-lactam and O-lactam substituted substituted spiro[azetidine-2-one-4,3'-indol-2'-one] spiro[azetidine-2-one-4,3'-indol-2'-one] derivatives <06JOC44 I8>. <06JOC4418>. R

~

0

c,

N

r,

R'

R'

N H

Br

X X

XV",B"

Br

Br

~fi/~" ~I ~ ,~~

E E

R-

0o

N But ii Ph Ph -+ L,,ph i-~ O,/~lN, lph

o

Y

/;

~~P

Y

- PMP

N,Bu Butt

35

34 34 (39-91%) (39-91%)

R == R' R'== Br Br (charteIline (chartelline A) A) R R == R' R'== HH (chartelline (chartelline C) C) R Key: i) LDA,-40 LDA, --40 DC. E-Cl. ~ ii) E-C1.

Spiranic ~-lactams [~-lactams have been prepared by the reaction of N-protected cyclic keteneN,S-acetals with vinyl isocyanates <06SL201>. The synthesis of spiro-~-lactams spiro-~-lactams through halogen-mediated intrasulfenyl cyclization of cis-3-benzylthio-3-(prop-2-ynyloxy/-enyloxy)cis-3-benzylthio-3-(prop-2-ynyloxy/-enyloxy)[3-1actams has been achieved <06EJ04943>. <06EJO4943>. The one-pot three-component reaction for the ~-lactams direct conversion of certain alkylhydroxylamine hydrochlorides (alkyl = benzyl, pmethoxybenzyl, benzhydryl, tert-butyl), formaldehyde or an alkyl glyoxylate and bicyclopropylidene to furnish the 3-spirocyclopropanated 2-azetidinones 36 has been developed by microwave heating <06EJOI251>. <06EJO1251>. The acid-catalyzed fragmentative rearrangement of tricyclic isoxazolidines yields cyclopropane-fused ~-lactams ]3-1actams <06SLl125; <06SL1125; 06EJ05485>. 06EJO5485>. The highly diastereoselective synthesis of fused oxopiperazino-~-lactams oxopiperazino-i3-1actams 37 by Staudinger reaction between functionalized ketenes and 5,6-dihydropyrazin-2(lH)-ones 5,6-dihydropyrazin-2(1H)-ones 11>. has been carried out <06TL89 <06TL8911 >. O

+

R1

+! ~ [R,R~] _

R'RlcHo eHO + R'R2NHOH.HCl NHOHHe, + ~

i__..~ 2-

:)=t:

"--~" R

36 (49-78%)

R~L-N-Bn O/~--N.~ . /OTBDMS R1 37

Key: i) NaOAc, EtOH, MW. The synthesis of a series of macrocyclic bis-[~-lactam bis-~-lactam derivatives via a highly stereoselective [2+2] Di-exo-3-amino-7[2+2] cycloaddition has been described <06TL8855>. Di-exo-3-amino-7oxabicyclo[2.2.l ]hept-5-ene-2-carboxylic acid, five aldehydes and two isocyanides were oxabicyclo[2.2.1]hept-5-ene-2-carboxylic reacted both in methanol and in water to prepare a 10-membered lO-membered ~-lactam J3-1actam library via a Ugi4-centre-3-component reaction <06TL9113>. 4-Formyl-l-(2- and 3-haloalkyl)azetidin-2-ones 3-haloalkyl)azetidin-2-ones have been prepared as valuable starting materials for the synthesis of different optically 1,4-diazepane annulated ~-lactam [3-1actam active bicyclic azetidin-2-ones, such as piperazine and 1,4-diazepane ]3-1actam-fused enediynes involved an derivatives 38 <06JOC7083>. A synthetic route to ~-lactam-fused intramolecular Kinugasa reaction <06CC2992>. A ~-lactam-azasugar [3-1actam-azasugar hybrid (polyhydroxylated carbacephem) has been designed and synthesized as a potent glycosidase inhibitor <06TL7923>. 7-Amino- and 2-ethoxycarbonyl-5-dethia-5-oxa-cephams were prepared from 1,3-alkylidene-l-erythritol <06Tl0928>. <06T10928>. Synthetic approaches towards a new class of strained lactenediynes, compounds where a 10-membered enediyne ring is fused with a ~-lactam J3-1actam have been described <06ARK15; 06ARK261>. The stereoselective synthesis of functionalized tricyclic [3-1actams ~-lactams via intramolecular nitrilimine nitrilimine cycloaddition has been achieved <06TA1319>. Strained tricyclic ~-lactams 39 were prepared via intramolecular

100 1O0

B. Alcalde Alcaide and P. Almendros

[2+2] cycloaddition reactions in 2-azetidinone-tethered enallenols with control of the regioselectivity by choice of alkene substitution <06CEJ1539>. <06CEJ 1539>.

R10

O

-i

R10

"R2

1

OH 2 H H : R

iii

ii

X

--

OH H H R2

"

38 (41-87%) (41-87%)

339 9 (52-57%) (52-57%)

2

NH 2 , MgSO4, MgS0 4 , CH NaBH 4 , MeOH, reflux. Key: i) R R2NH2, CH2C12, reflux, iii) Toluene, 220°C, 220 ~ sealed 2Cb, RT. ii) NaBH4, tube.

New C-3' hydroxamate-substituted and more lipophilic cyclic hydroxamate cephalosporin derivatives were preppared as a potential new generation of selective antimicrobial agents <060BC4178>. <06OBC4178>. The positive effect of natural and negatively charged cyclodextrins on the stabilization of penicillins towards ~-lactamase ~-Iactamase degradation due to inclusion and external guest-host association has been studied <060BC1297>. <06OBC1297>. The first step of the deacylation reaction of benzylpenicillin in the E. coli TEMI TEM1 ~-Iactamase 13-1actamase has been <060BC206>. A strategy for the solid-phase synthesis of penicillin derivatives has modelled <06OBC206>. been reported <06S3297>. Studies on the hydrolysis of of oxacillin have been carried out <06CEJ7597>. A theoretical proposal for the synthesis of carbapenems from 4-(2propynyl)azetidinones promoted by [W(CO)s] [W(CO)5] as an alternative to the Ag+-assisted process has been reported <06CEJ7929>. A stoichiometric molecularly imprinted polymer for the class-selective recognition of ~-Iactam ~-lactam antibiotics in aqueous media has been described <06AG(E)5158>. An amide derived from penicillin V and racemic (R/S)-2-aminobutanol has been prepared and shows significantly higher toxicity than the pure diastereomers <06TLI 737>. The synthesis and siderophoric activity of conjugates of methyl 6<06TL1737>. aminopenicillanate with biscatechol-hydroxamate chelators have been reported <06T7799>. An efficient method for the deprotection of tert-butyldimethylsilyl tert-butyldimethylsilyl ethers was TiCl TiC14-Lewis 4-Lewis base complexes; it was applied in the synthesis of l~-methylcarbapenems l~-methyIcarbapenems<06JOC5380>. The reactivity of cephalosporin sulfones has been studied <06JHC 183>. OXETANES, 4.5 OXETANES, LACTONES) LACTONES)

DIOXETANES, DlOXETANES,

OXETENES OXETENES

AND

2-OXETANONES 2-0XETANONES

([~(~-

Ketene chemistry including ketene-aldehyde cycloaddition to form ~-lactones [3-1actones and ketene-alkene cycloaddition to form oxetanes has been reviewed <06EJ0563>. <06EJO563>. It has been reported that the attachment of the oxetane motif to molecular scaffolds results in remarkable improvements of key physicochemical characteristics and provides valuable opportunities for property-guided drug discovery <06AG(E)7736>. Oxetanes have also been utilized as synthons for the preparation of different compounds. The synthesis of 5-hydroxyfunctionalized 2-trifluoromethyl-l-alkenes was achieved by l-(trifluoromethyl)vinylation 1-(trifluoromethyl)vinylation via oxetane ring-opening <06S <06S128>. 128>. A convenient route to tetrahydropyran-based liquid crystals from oxetane precursors has been described <06EJO3326>. <06EJ03326>. The asymmetric synthesis of of y~,hydroperoxyalkanols involved regiospecific and stereoselective acid-promoted opening of oxetanes with hydrogen peroxide. This was used as the core of the first asymmetric synthesis of 1,2-dioxolane-3-acetic acids 40 <06JOC2283>. An aniline glycosyl carbamate spacer linked to the 2'-OH of paclitaxel has been obtained <06JOC9628>. The synthesis of 7- and 10-spermine conjugates of paclitaxel and IO-deacetyl-paclitaxel 10-deacetyl-paclitaxel were synthesised as potential

101

Four-membered ring systems

prodrugs <06TL2667>. Noncytotoxic taxanes as novel antituberculosis agents have been discovered <06JMC463>. A 4-methyl-5-oxo docetaxel analogue was prepared starting from 10-deacetylbaccatin III <06OL2301>. <060L2301>. Bridging converts the noncytotoxic nor-paclitaxel derivative 41 into the cytotoxic analogue 42 by constraining it to the T-taxol conformation <060L3983>. <06OL3983>.

R, '~O . .... 8stepsR ~ . ] . ~ co .

AcQ OOH OO ~ " o . < _ .0. o6 o

O ACO AcO OOH OOH O ~

P,C H ON,".,,L

o,

~ : ° °

° a"= .

:H: o

PhCH 200

~_

41 41

o

°

42

A C,D-seco-paclitaxel derivative was prepared from taxine and tested for biological A activity <06TL8503>. A 36-step synthesis has been carried out in automated synthesizers to provide a synthetic key intermediate for taxol <06MI370>. The bicyclic oxetane 43 which was obtained by the [2+2] [2+2] photocycloaddition (Patemo-Btichi (Patern6-BiJchi reaction) of a methylthymine derivative with benzaldehyde, showed, in model studies, efficient photosensitized splitting of of thymine oxetane units by covalently linked tryptophan in high polarity solvents <060BC29 I>. The Patern6-BiJchi Patemo-Biichi reaction of 1,3-dimethylthymine or 1,3-dimethyluracil <06OBC291>. with benzophenone benzophenone and its six 4,4'-disubstituted derivatives generated two series of regioisomeric oxetanes, head-to-head head-to-head and head-to-tail isomers <06EJOI790>. <06EJO 1790>. The efficient photosensitized splitting of of the thymine dimer/oxetane unit on its modifying ~-cyclodextrin 13-cyclodextrin by a binding electron donor has been reported <060BC2576>. <06OBC2576>. Thymine oxetanes have been tested as charge traps for chemical monitoring of nucleic acid mediated transfer of excess electrons <06AG(E)5376>. The pathways of excess electron transfer in DNA with flavindonor and oxetane-acceptor modified DNA hairpins 44 has been investigated <06CEJ6469>. Patem6-Biichi reaction of 2,3A temperature effect on the stereoselectivity in the Patern6--Bachi dihydrofuran-3-ol derivatives with benzophenone was noted <06TL2527>. A new terpenoid, the tricyclic oxetane amentotaxone, has been isolated from Amentotaxus formosana <060L753>. <06OL753>. The spirocyclic oxetane lactone 45 has been synthetized <06T7747>. An oxetane-fused benzene was proposed as intermediate in the mass spectrometric fragmentation of of even-electron negative ions from hydroxyphenyl carbaldehydes and ketones <06TL4601>. <06TL4601 >. 0

HNly oANJ

l C02Bn

~

0

HNJ4-0

oAN~Ph I l C0 H CO2Bn 2Bn

43 (21%) 43(21%)

0

0-0LNH Ph¥NAO Ph j

0==\ NH ~H 44 G (~ 44

~ (NH ~

G

=

1 R10 R 0

0

~NAo jJ a2 -bR2

0 45 45

0 O

Key: i) PhCHO, hv, MeCN, RT. An acid-catalyzed ring-closing ynamide-carbonyl metathesis, which would proceed through ring opening of of an amide-substituted oxetene intermediate 46 formed through a stepwise hetero [2+2] cycloaddition pathway, has been described <06OL23 <060L23 l>. I>. The synthesis of tetrasubstituted enol ethers by E-selective olefination of esters with ynolates has been reported to occur via lithiated oxetene species <06JA1062; <06JAI062; 06CEJ524>. A dioxetane-based selective chemiluminescent probe for singlet oxygen has been employed to detect and

102

B. Alcaide and P. Almendros

quantify singlet oxygen in the reactions of superoxide with organic peroxides <06JOC796>. <06JOC796>. The synthesis and fluoride-induced chemiluminescent decomposition of bicyclic dioxetanes substituted with a 2-hydroxynaphthyl group have been described <06T5808>. The synthesis of dioxetane 47 has been achieved during abortive attempts to synthesize ent-premnalane A ent-premnalane A <06T53 13>. Bicyclic dioxetanes bearing a 2-hydroxy-l,I'-binaphthyl-5-yl <06T5313>. 2-hydroxy-l,l'-binaphthyl-5-yl moiety are active towards charge-transfer-induced chemiluminescent decomposition intramolecular modulation intramolecular <06T12424>. Color for charge-transfer-induced chemiluminescence of bicyclic dioxetanes bearing a 3-hydroxy-5-naphthylphenyl moiety in coordination sphere been reported 4-(3-tertthe has <06TL8407>. Butyldimethylsilyloxyphenyl)-4-methoxyspiro[I,2-dioxetane-3,2'-adamantane] Butyldimethylsilyloxyphenyl)-4-methoxyspiro[ 1,2-dioxetane-3,2'-adamantane] was <06S1781>. The dioxetanone intermediate 48 was synthesised by two different approaches <0681781>. isolated in studies on the possible biogenetic precursors of pyrrole-2-aminoimidazole <06OL2421>. alkaloids <060L242 I>. A dioxetanone intermediate has been proposed as supporting the bioluminescence mechanism for the chemiexcitation process to generate the singlet-excited state of of neutral oxyluciferin <06TL6057>. A spirocyclic dioxetanone intermediate was proposed in investigations of the unimolecular reactivities of a range of of perbenzoate anions in the gas phase by electrospray ionization tandem mass spectrometry <06JOC7996>. <06JOC7996>.

R30C

o
o

o

...,

-i

Y

46

47

48 48

Key: i) 02, hv, CH2C12, RT. ]3-1actone-type The structure and absolute configuration of the unusual fused 13-lactone-type metabolite vibralactone 49, which was found to inhibit pancreatic lipase with an IC ICs0 of 0.4 so of gg/mL, from the cultures of the Basidiomycete Boreostereum Ilg/mL, Boreostereum vibrans have been established by spectroscopic and computational methods <06OL5749>. <060L5749>. A detailed mechanistic investigation of epoxide carbonylation by the catalyst [(salph)Al(THFht [(salph)Al(THF)2] + [CO(CO)4r [Co(CO)4]- (salph = N,N'-o-phenylenebis(3,5-di-tert-butylsalicylideneimine), N,N'-o-phenylenebis(3,5-di-tert-butylsalicylideneimine), THF = tetrahydrofuran) to form 13[3<06JAI0125>. A readily prepared Cr-Co lactones has been carried out <06JA10125>. Cr-Co bimetallic catalyst is capable of effecting epoxide carbonylation to produce 13-lactones ]3-1actones at substantially lower CO pressures than previously reported catalyst systems <060L3709>. <06OL3709>. A chiral oxazaborolidinecatalyzed enantioselective synthesis of ~-lactones ]3-1actones from ketene and aldehydes has been developed <06OL4943>. <060L4943>. A catalytic asymmetric synthesis of 3,4-dialkyl-cis-~-lactones, 3,4-dialkyl-cis-~3-1actones, inhibitors of the thioesterase domain of fatty acid synthase, via a sequential ketene dimerization/hydrogenation process has been achieved <06JOC4549>. <06JOC4549>. 3-Alkylidene-oxetan2-ones 50 have been prepared in good to excellent yields, with high Z-selectivity, by olefin 3-methyleneoxetan-2-ones in the presence of Ru-based second cross metathesis with 3-methyleneoxetan-2-ones generation metathesis catalysts <06OL2139>. [3<060L2139>. Molecular recognition of lactones, including including~­ lactones, can be achieved by inclusion complexation with optically active hosts derived from tartaric acid <06TA1678>. <06TAI678>. The Walden cycle which interconverts the stereochemical configurations of chlorosuccinic and malic acids involves a ~-Iactone ~3-1actone intermediate rather than ~-lactone intermediate because the Onue Onuc C CI C1 angle in the transition structure for the an a-lactone (174 ~ is more favorable than that for the latter (139°), (139~ as determined by a former (174°) computational study <06CC1106>. <06CC 11 06>. An efficient chiron approach to the total synthesis of (-)-

103

Four-membered ring systems

tetrahydrolipstatin 51 starts from tri-O-acetyl-D-glucal, tri-O-acetyI-D-gIucal, and uses copper-mediated C-C bond formation, Frater alkylation, and Barton-McCombie deoxygenation <06SL3888>. Stereoselective syntheses of (-)-tetrahydrolipstatin have been achieved via two divergent approaches through Prins cyclizations as the key steps <06TL4995>. The stereoselective synthesis of (-)-tetrahydrolipstatin via a radical cyclization based strategy has also been reported <06TL4393>. An expeditious enantioselective total synthesis of valilactone has been accomplished <06JOC5748>. Concise syntheses of valilactone and a two-carbon transposed aldol-lactonization process as a key step orlistat derivative employed a tandem Mukaiyama aldol-Iactonization <060L4497>. <06OL4497>. An efficient protocol has been developed using D-(2R)-Oppolzer sultam as a chiral auxiliary for generating anti/syn anti/syn diastereomers with high enantiopurity and were utilized in an efficient synthesis of natural product belactosin C 52 and its synthetic congeners <06JOC337>. A concise and straightforward 14-step total synthesis of (±)(+)<060BC2845>. Enantioselective total syntheses of salinosporamide A 53 has been described <06OBC2845>. lactacystin ~-lactone J3-1actone 54 have been achieved <06JA68 <06JA6810; 06JOC1220; 060BCI93>. 06OBC193>. The 10; 06JOCI220; reaction of acryloyl chloride with an amino ketone in the presence of pyridine produces a bicyclic ~-lactone [3-1actone rather than the corresponding acrylamide, which can be the major product <060Ll7I7>. A diastereoselective organonucleophile-promoted bisunder other conditions <06OL1717>. cyclization process provides access to bicyclic- and tricyclic-~-lactones tricyclic-13-1actones bearing tertiary carbinol centers and quaternary carbons and employed keto acid substrates <060L4363>. <06OL4363>. A synthetic strategy for construction of the novel spiro-bicyclic ~-lactone-y-Iactam 13-1actone-3,-lactam system present in oxazoiomycin >. The ~-lactone oxazolomycin has been demonstrated <06TL603I <06TL6031>. [3-1actone nucleus has been used as a synthon for the preparation of different compounds such as (-)deoxyharringtonine <06JA10370>, the CrC <060L7>, and C7-C20 zo fragment of amphidinolide B <06OL7>, (-)-pironetin <06JA7438>. SN2' ~-lactone has provided the requisite SN2' Ring opening of a [3-1actone pyrrole-substituted allene for the enantioselective total synthesis of (-)-rhazinilam ~-lactones yielded a-amino <06JA10352>, while ring opening of amino J3-1actones m-amino acids <06CCI757; <06CC1757; 06TLlOI9; 06TL1019; 06TL370I>. 06TL3701>. Yttrium initiators have been used for the polymerization of racemic ~-butyrolactone 13-butyrolactone <06AG(E)2782>. Different syntheses of functionalized ~-keto [3-keto esters have been carried out starting from 4-methyleneoxetan-2-one <06EJOllI7; <06EJOll17; 06TA2672; 06Tl0497>. 06T10497>. HO

~H

nC6H13~ .....~RC11H23

)=(

RI+

H

o

+

R)jR

1 ~ i__ R22

R',]

o

I

1

-~

OHCHN"~

o 50 50 (55-94%) (55-94%)

49 49

-

51 O

O

CI

..... , ~ _ _ / / ~ , /

~ 52

OH 53

54

O

CH2C12,reflux. Key: i) 5 mol% Ru-based cat., CHzCh, 4.6 4.6

THIETANES, TAMS, AND RELATED RELATED SYSTEMS THIETANES, ~-SUL [3-SULTAMS,

I,2-thiazetidine 1, I-dioxides (~­ A stereoselective one-pot synthesis of substituted 1,2-thiazetidine 1,1-dioxides (13<06OL5513>. sultams) 55 started from heterocyclic pentafluorophenyl (PFP) sulfonates <060L55 13>.

104

B. Alcaide and P. Almendros

Thermolysis of of the pentacoordinate pentacoordinate 1,2-thiazetidine 1,2-thiazetidine 1-oxide I-oxide 56, which was synthesized synthesized for characterized by X-ray crystallographic crystallographic analysis, gave the corresponding corresponding the first time and characterized aziridine 57 and a cyclic sulfinate sulfinate almost quantitatively <06OL4625>. <060L4625>. aziridine

OO:S?'('-NP PFp )-r-

R"

_i

Hl_';'~ '~_;' R It O-t- N ,

c8

FsC F s

o

55 (26-58%)

~

~"~~Fs

S- N -",\'0 'Ph

~

II

56

~h

ii

-

+ N FsC--P'-Ph FsC (94%) 57 (94%)

cd FSC

I

/-/

CF

s

0

~ 0

(quant)

MO(CO)6, MeCN-H20, MeCN-HzO, 90 90°C. 160°C, Key: i) Mo(CO)6, ~ ii) Toluene, 160 ~ sealed tube. spironucleosides, including the spiroannulated spiroannulated thietane 58 were Four-membered spironucleosides, L-thietanose nucleosides which have showed synthesized <06TL3875>. Various D- and L-thietanose moderate anti-HIV activity were synthesized from D- and L-xylose <06JMC1635>. A synthesis of of isothiazolidines isothiazolidines 60 via sulfonium ylides formed by the reaction of of thietanes 59 <06TLl109>. The 2-(diphenylmethylene)thietan-3-one 2-(diphenylmethylene)thietan-3-one 61 and nitrene has been achieved <06TLl109>. reacted with 1,2,4,5-tetrazines 1,2,4,5-tetrazines in KOH/MeOH/THF to give 4H-pyrazolo[5,1-c]thiazines <06TL7893>. A model for the prediction of the homolytic bond dissociation enthalpy and adiabatic ionization ionization potential potential of fused four-membered heterocycles, including benzothiete 62, <060BC846>. has been developed using calculations at B3LYP/LANL2DZ level <06OBC846>. Ph S~O,,,,/,,, O Ar Ar O,,~Ph ~~ ]

q

BnO 58

+ Phl=NTs

59 59

- Q-TS i ,_

"Ts 60 (56-67%) (56-67%) 60

O~Ph ~ SS 61 61

62

62

Key: i) Cu(acac)z, Cu(acac)2, benzene, reflux.

4.7

SILICON AND PHOSPHORUS PHOSPHORUS HETEROCYCLES. HETEROCYCLES. MISCELLANEOUS

The preparation and reactivity of heterocyclic compounds with a silicon atom and another non-adjacent different heteroatom including 1,3-oxasiletane, 1,3-oxasiletane, 1,3-azasiletane, 1,3-azasiletane, 1,31,3thiasiletane, thiasiletane, and 1,3-phosphasiletane 1,3-phosphasiletane have been reviewed <06T7951>. <06T7951 >. An overview on novel silicon-based reagents for organic synthesis including silacyclobutanes and 1,31,3disilacyclobutanes has appeared <06CEJ1576>. 3,4-Dibromo-1 ,2,3,4-tetrakis( di-tert3,4-Dibromo-l,2,3,4-tetrakis(di-tertbutylmethylsilyl)cyclotetrasilene 63 was prepared in 81 % yield by reduction of the 81% corresponding tetrabromocyclotetrasilane with 2.1 equivalents of KCg KCs in THF <06AG(E)3269>. Calculations Calculations on a series of polycyclic silicon molecules confirm that the introduction of a double bond into into four-membered cyclic silanes lowers the ring strain by the cyclic delocalization of 1t-electrons ~-electrons through hyperconjugation with the (J cy bonds <06T4491>. <06T4491 >. The first thermally stable four-membered heterocycle chlorosilylene 64 has been synthesised and characterized <06AG(E)3948; 06AG(E)424 1>. The four-membered heterocycle 65 has 06AG(E)4241>. been prepared and unambiguously identified by multinuclear NMR spectroscopy <06AG(E) 1643>. Nickel-catalyzed ring opening reaction of silacyclobutanes 66 with <06AG(E)1643>. aldehydes afforded the corresponding alkoxyallylsilanes 67, while ring expansion of benzodimethylsilacyclobutene with aldehydes occurred under nickel catalysis to give oxasilacyclohexenes <060L483>. <06OL483>. Oxidation of benzylidene acetals that incorporate a siletane ring at the para position creates a deprotection pathway without affecting other important chemical properties of the benzylidene acetal <06JOC420>.

105

Four-membered ring systems

f-Bu2MeSi, ,SiMef-Bu2 t-Bu2MeSi, ` ,SiMet-Bu 2 Si=Si Si--Si

[

t-Bu,

,CI

Tip,,T ip ,,Tip Si--Si

"t-Bu

Sn--Si +ip "Tip Tip"

N--Si

I

Br-Si-Si-Br

B r - S[i - - S i -[ B r t_Bu2MeS i SiMet.Bu 2 f-Bu2MeSi SiMef-Bu

P

63

64

65

R2

R3 "3 R1 (~) Si-R 1 R1 '

S

66

Tip = 2,4,6-triisopropylphenyl 2,4,6-triisopropylphenyl

" --

~'R 2

67 (47-87%) (47-87%)

Key: i) Ni(cod)2, PPh2Me, PPh2Me, toluene, 100°C. 100 ~ The structure of of a four-membered phosphapalladacycle has been established by a single-crystal X-ray structural analysis <06JA6376>. The thermal conversion of the cyclic 5 carbodiphosphorane 68 into 1,2-A -azaphosphete 69 proceeds almost quantitatively and 1,2-~,5-azaphosphete regioselectively <06AG(E)7447>. The reaction of aryl nitriles with [1,3,2,4]diselenadiphosphetane (Woollins' reagent) 70, followed by water affords a variety of of <060L5251>. A single-crystal X-ray diffraction primary arylselenoamides in 60-100% yield <06OL5251>. study of a bicyclic four-membered phosphorus-containing product showed the bicycle to 5 adopt envelope-type topology <06AG(E)6685>. A 1,3,2-1. -oxazaphosphetidine reaction 1,3,2-~,5-oxazaphosphetidine intermediate, in which the p-o P-O bond order is 0.47, has been found on studying the aza-Wittig reaction between phosphazenes and aldehydes <06JOC2839>. It has been postulated that betaine 71 can be formed upon treatment of the corresponding iminophosphorane with phenyl isocyanate through an abnormal aza-Wittig reaction <06EJ04170>. <06EJO4170>. Various other fourmembered azaphosphaheterocyclic intermediates have also been proposed <06CEJ7178; 06T4128>. The fragmentation of C-amino four-membered phosphorus ylides to carbenes has been proposed <06JA459>. The preparation and characterization of the air-tolerant 1,3diphosphacyclobuten-4-yl radical 72 has been achieved <06AG(E)4341>. A fluorous analogue of Lawesson's reagent for thionation of carbonyl compounds has been developed and its use demonstrated on a series of amides, esters, and ketones <06OL1093>. <060Ll093>. Several structures of cationic P-S-halogen cages containing a four-membered heterocycle have been characterized <06CEJ <06CEJl703>. 1703>. ,R R

(:~~+/NR2

W~ P- NR2 _ I_ N=-( ~ "..NR 2 R Ph

68 68


i

__~

-P-NR 2 N

I

R

Ph/

69 69

Se II Se Se-P-Ph / ~ e ~ [e Ph-P-Se [/

Se 70

Me CO2Et ~C02Et Me N-PPh N-PPh3 )-[ 3 N o N'Ph "Ph 71

t-Bu% f-Bu,

Mes Mes

5=i

Mes' Mes

72

Key: i) Benzene, 80°C, 80 ~ 60h. Mes = 2,4,6-t-Bu3C6H2. N-Sulfonyl aziridines underg oxidative addition to palladium(0) palladium(o) complexes resulting in azapalladacyclobutane complexes 73, which after intramolecular carbopalladation in the presence of copper(I) iodide gave azapalladabicyclo[3.2.l]octanes azapalladabicyclo[3.2.1]octanes <06JAI5415>. <06JA15415>. A titanacyclobutane has been proposed as intermediate in the olefin cyclopropanation with the Ti-Mg-CCI Ti-Mg-CC144 system <06JOC4325>. The existence of oxaarsetanes 74 during an arsa-Wittig 170 <06EJO4934>. The syntheses, H and 17 0 NMR spectroscopy <06EJ04934>. reaction has been proved by I1H structures, and thermolyses of pentacoordinate 1,2-oxastibetanes, which are considered as formal [2+2]-cycloadducts in the reaction of a stibonium ylide and a carbonyl compound, have been described <06JOC659>. A tricyclic intermediate containing a four-membered metallacycle has been proposed for the Rh-catalyzed alkylation-cycloaddition of 3-haloalkyl1,6-enynes <06JA14818>. <06JAI48l8>. A planar metallacycle bearing a relatively short Hf-Sb bond has been study by X-ray diffraction <06CC4030>. Reversible alkene extrusion from platinaoxetanes has been reported <06JA12088>. Synthetic and structural studies of germanacycle 75 have been reported <06CC3978>. Homogeneus, titanocene-catalyzed

106

Alrnendros B. Alcaide and P. Almendros

dehydrocoupling of of amine-borane adducts into four-membered azaboracycles has been accomplished <06JA9582>. Formation of (bistriphenylphosphine)-2-(2,2,4,4<06JA9582>. of (bistriphenylphosphine)-2-(2,2,4,4tetramethylpentan-3-ylidene)-1 ,3-dithiolato-platinum 76 and its X-ray crystaIIographic tetramethylpentan-3-ylidene)-l,3-dithiolato-platinum crystallographic <06CEJ7742>. Synthesis and X-ray analysis of of the 1,2analysis have been carried out <06CEJ7742>. dialuminacyclobutene 77 have been published <06AG(E)2245>. <06AG(E)2245>. The synthesis of of an Nheterocyclic carbene-Pd(lI) carbene-Pd(II) four-membered complex and its application in the Suzuki and Heck-type cross-coupling reaction have been documented <06T6289>. <06T6289>. Intramolecular C-H C-H of molybdenacyclobutanes have been performed <06JA9038>. <06JA9038>. activation reactions of via carbon monoxide and isocyanide insertion has been Formation of of aluminacyclobutenes via accomplished <06CCI763>. N2 to give <06CC1763>. Experimental results have shown that Tb Ti2 reacts with N2 a D2h-symmetric D2h-symmetric TbN Ti2N22 molecule which has a planar, cyclic structure with alternating Ti and N atoms <06AG(E)2799>. <06AG(E)2799>. Studies on ruthenium metallacycles derived from 14-electron complexes as possible olefin metathesis intermediates have been carried out <06JA16048>. <06JAI6048>. The reaction of of phosphaalkenes with electrophiles has provided an effective route to 1,3diphosphetanium salts containing a P2C2 P2C2 ring <06JAI5998>. <06JA15998>.

r

Ph Ph P Pd(phen) VAsPh3 d(phen) ro~SPh3 I

}- N

R22

R

"R11

'R

73

- o ) ph/ Ph

74

phen O-phenanthroline phen = 1,1 1,10-phenanthroline

4,8 4.8

S-Pt(PPh3)2 Ar S-Pt(PPh3 h Me3Si .~--' S ~AI"

t-Bu,, ,Dipp t-BU"--NPiPP N~N Ie I ,

_ . N-Ge' Dipp~ "CI Dipp 'CI

1--8

tu t-Bu--( t-Bu t-Bu

75

Me3Si 76

"Ar 77

Dipp = 2,6-/-Pr2C6H3

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107 | 07

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Org. Chern. Chem. 2006, 71, 5804. C. Palomo, J.M. Aizpurua, A. Benito, L. Cuerdo, R.M. R.M. Fratila, J.1. J.I. Miranda, A. Linden, 1. J. Org. Org. Chern. Chem. 2006, 71,6368. 71, 6368. Y. Wang, Y. Y. Liang, L. L. Jiao, D.-M. Du, 1. J. Xu,J. Xu, J. Org. Org. Chern. Chem. 2006, 71,6983. 71, 6983. Y.

Four-membered ring systems

06JOC7083 06JOC7100 06JOC772I 06JOC7721 06JOC7885 06JOC7996 06JOC9045

06JOC9229 06JOC9628 06MI 1 06MIl 06MI49 06MI 109 06MIl09 06MI203 06M1370 06MI370 06MI544 06MI917 06MI 1123 123 06MIl 06MI2114 06MI2203 06OBC193 060BCI93 06OBC206 060BC206 06OBC291 060BC29I 060BC846 06OBC846 060BCI297 06OBC1297 060BC2576 06OBC2576

06OBC2845 060BC2845 06OBC4059 060BC4059 06OBC4178 060BC4178 060BC4533 06OBC4533 06OL7 060L7 06OL231 060L23I 060L483 06OL483 06OL753 060L753 060LI093 06OL 1093 060LI 101 06OL 1101 060LI 105 06OLl105 06OL1323 060L1323 06OL 1717 060L17l7 060LI779 06OL1779 06OL1983 060LI983 060L2139 06OL2139 060L2301 06OL2301 060L242I 06OL2421

06OL3121 060L3121 06OL3211I 060L32I 060L3709 06OL3709 06OL3335 060L3335 06OL3923 060L3923 06OL3927 060L3927

109

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Florio, R. Luisi, A. Salomone, C. Cuocci, Org. R. Dhawan, R.D. Dghaym, D.J.St. Cyr, B.A. Amdtsen, Arndtsen, Org. Org. Lett. 2006,8,3927. 2006, 8, 3927.

110 060L3983 06OL3983 060L4335 06OL4335 060L4363 06OL4363 06OL4497 060L4497

06OL4625 060L4625 060L4783 06OL4783 060L4943 06OL4943 06OL5251 060L525I 06OL5325 060L5325 060L5365 06OL5365 060L5501 06OL5501 060L5513 06OL5513 060L5749 06OL5749 06PS2483 06S115 06S 128 06S128 06S514 06S633 06S659 06S 1781 06S1781 06S1829 06S2327 06S2885 06S3297 06S3425 06SL201 06SL781 06SL1113 06SLlI13 06SL1125 06SLlI25 06SL2039 06SL3179 06SL3443 06SL3888 06T915 06T1565 06T 1565 06T4128 06T449I 06T4491 06T5054 06T5313 06T5808 06T583I 06T5831 06T6289 06T6882 06T7747 06T7799 06T7951 06T829I 06T8291 06TI0497 06T 10497 06T10928 06T 10928

B. Alcaide and P. Almendros S. Tang, C. Yang, P. Brodie, S. Bane, R. Ravindra, S. Sharma, Y. Jiang, lP. J.P. Snyder, D.G.I. Kingston, Org. Lett. 2006,8,3983. Org. Lett. 2006, 8, 3983. S. Baktharaman, S. Selvakumar, V.K. Singh, Org. Org. Lett. 2006,8,4335. 2006, 8, 4335. Lett. 2006,8,4363. H. Henry-Riyad, Henry-Riyad, C. Lee, V.c. V.C. Purohit, Daniel Romo, Org. Org. Lett. 2006, 8, 4363. G. Ma, M. ZancaneIla, Lett. 2006, 2006,8, Zancanella, Y. Oyola, R.D. Richardson, Richardson, J.W. Smith, D. Romo, Org. Org. Lett. 8, 4497. 2006,8,4625. N. Kano, Y. Daicho, T. Kawashima, Org. Org. Lett. 2006, 8, 4625. S.A. Testero, E.G. Mata, Org. Lett. 2006,8,4783. Org. Lett. 2006, 8, 4783. EJ. Corey, Org. Lett. 2006,8,4943. V. Gnanadesikan, Gnanadesikan, E.J. Org. Lett. 2006, 8, 4943. Org. Lett. 2006,8,5251. 2006, 8, 5251. G. Hua, Y. Li, A.M.Z. A.M.l. Slawin, J.D. Woollins, Org. S.D. Hamilton, Org. Org. Lett. 8, 5325. G. Arnott, J. Clayden, S.D. Lett. 2006, 2006,8,5325. H. Lu, C. Li, Org. Lett. 2006,8,5365. Org. Lett. 2006, 8, 5365. Vargas-Sanchez, S. Lakhdar, F. Couty, G. Evano, Org. Lett. 2006,8,5501. M. Vargas-S~inchez, Org. Lett. 2006, 8, 5501. Lett. 2006,8,5513. A.K. de K. Lewis, BJ. B.J. Mok, D.A. Tocher, J.D. Wilden, S. Caddick, Org. Org. Lett. 2006, 8, 5513. D.-Z. Liu, F. Wang, T.-G. Liao, l-G. J.-G. Tang, W. Steglich, H.-J. Zhu, l-K. J.-K. Liu, Org. Org. Lett. 2006, 8,5749. Phosphorus, Sulfur A.K. KhalafaIlah, Khalafallah, N.A.A. EI-Kanzi, E1-Kanzi, H.A. Soleiman, M. Younis, Phosphorus, Relat.Elem. 2006, 181,2483. 181, 2483. D.K. Tiwari, V.K. Gumaste, A.R.A.S. Deshmukh, Synthesis 2006, 115. 2006,115. R. Nadano, J. Ichikawa, Synthesis 2006, 128. H.-l Flammersheim, H. GorIs, lJ. Fleischhauer, Fleischhauer, R. Beckert, lJ. Weston, M. Schmidt, H.-J. G6rls, Synthesis Synthesis 2006,514. 2006, 514. R. A. Youcef, C. Boucheron, S. Guillarme, S. Legoupy, D. Dubreuil, F. Huet, Synthesis Synthesis 2006, 633. L. Jiao, Y. Liang, Q. Zhang, S. Zhang, lJ. Xu, Synthesis Synthesis 2006, 659. E.L. Bastos, L.F.M.L. Ciscato, D. Weiss, R. Beckert, W.J. WJ. Baader, Synthesis 2006, 1781. Synthesis 2006,1829. 2006, 1829. S.-Z. Jian, Q. Yuan, Y.-G. Wang, Synthesis S. Lacroix, V. Rixhon, J. Marchand-Brynaert, Marchand-Brynaert, Synthesis Synthesis 2006, 2327. lJ. Fleischhauer, Fleischhauer, R. Beckert, W. Gunther, Giinther, H. GorIs, G6rls, Synthesis Synthesis 2006, 2885. D.B. Boggian, Boggi~in, E.G. Mata, Synthesis Synthesis 2006, 3297. M. Sarkar, A. Samanta, Synthesis Synthesis 2006, 3425. A. Zhou, L. Cao, H. Li, Z. Liu, C.U. Pittman Jr, Synlett 2006, 201. M. Sivaprakasam, Sivaprakasam, F. Couty, G. Evano, B. Srinivas, R. Sridhar, K.R. Rao, Synlett 2006, 781. Q. Yuan, S.-Z. Jian, Y.-G. Wang, Synlett 2006, 1113. M. Marradi, A. Brandi, A. de Meijere, Synlett 2006, 1125. W. Van Brabandt, N. De Kimpe, Synlett 2006, 2039. Repic, TJ. X. Jiang, K. Prasad, M. Prashad, lJ. Slade, O. Repi6, T.J. Blacklock, Synlett 2006, 3179. M.-C. Wang, W.-X. Zhao, X.-D. Wang, M.-P. Song, Synlett 2006,3443. 2006, 3443. J.S. Yadav, K.V. Rao, A.R. Prasad, Synlett 2006, 3888. lS. 2006,3888. FJ. F.J. Sayago, M.A. Pradera, C. Gasch, J. Fuentes, Tetrahedron 2006, 62, 915. 62, 1565. L. Troisi, L. Ronzini, C. Granito, L. De Vitis, E. Pindinelli, PindineIli, Tetrahedron 2006, 62,1565. N. Kanomata, S. Yamada, T. Ohhama, A. Fusano, Y. Ochiai, J. Oikawa, M. Yamaguchi, F. Sudo, Tetrahedron 2006,62,4128. 2006, 62, 4128. Y. Naruse, lJ. Ma, K. Takeuchi, T. Nohara, S. 1nagaki, Inagaki, Tetrahedron 2006, 62, 4491. BhaIla, S. Madan, P. Venugopalan, A. Bhalla, Venugopalan, S.S. S.S. Bari, Tetrahedron 2006, 62, 5054. I. Margaros, T. Montagnon, M. Tofi, Vassilikogiannakis, Tetrahedron Toil, E. Pavlakos, G. Vassilikogiannakis, Tetrahedron 2006, 62,5313. 62, 5313. N. Hoshiya, N. Fukuda, H. Maeda, N. Watanabe, M. Matsumoto, Tetrahedron 2006, 62, 5808. A. Liljeblad, L.T. Kanerva, Tetrahedron 2006, 62, 5831. T. Chen, lJ. Gao, M. Shi, Shi, Tetrahedron 2006, 62, 6289. Dejaegher, N. De Kimpe, Tetrahedron B. Van Driessche, W. Van Brabandt, M. D'hooghe, Y. Dejaegher, 2006,62,6882. 2006, 62, 6882. F.A. Macias, V.M.I. Vifiolo, Vinolo, F.R. Fronczek, G.M. Massanet, lM.G. J.M.G. MoliniIlo, Molinillo, Tetrahedron 2006, 62, 7747. 2006,62,7747. R. Schobert, A. Stangl, K. Hannemann, Hannemann, Tetrahedron 2006, 62, 7799. G. Rousseau, L. Blanco, Tetrahedron 2006, 2006,62,7951. 62, 7951. A. Bhalla, BhaIla, P. Venugopalan, Venugopalan, S.S. S.S. Bari, Tetrahedron 2006, 62, 8291. B.L. Ashfeld, S.F. Martin, Tetrahedron 2006, 62,10497. 62, 10497. Chmielewski, Tetrahedron 2006, 62,10928. 62, 10928. T.T. Danh, K. Borsuk, lJ. Solecka, M. Chmielewski,

ring systems Four-membered ring

06T12064 06TI2064 06T12424 06TI2424 06TA199 06TAI99 06TA1319 19 06TA13 06TA1678 06TAI678 06TA2216 06TA2216 06TA2672 06TL425 06TL 1019 06TLIOl9

06TL 1109 06TLII09 06TL 1117 06TLI 117 06TL1737 06TLI737 06TL2205 06TL2209 06TL2527 06TL2667 06TL3701 06TL3875 06TL4393 06TL4601 06TL4995 06TL5255 06TL5257 06TL5393 06TL5665 06TL5883

06TL5993 06TL6031 06TL6057 06TL6377 06TL6835 06TL7893

06TL7923 06TL8407 06TL8503 06TL8855 06TL8911 06TL8977 06TL9113

III 111

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