The chemistry of mixed organosulfur-silicon compounds

oo404mo/aa 1~00+.00 0 1988 Papmoo Joumab Lad

Trwoknhm Vol. 44. No. 2. pp. 281-32.4 1988 Primed in Cirut Bnuin.

TETRAHEDRON

REPORT NUMBER

228

THE CHEMJSTRY OF MIXED ORGANOSULFUR-SILICON COMPOUNDS ERIC IbCrc and MOHAMMADASLAM Departmentof Chemistry.SUtcUnivcrsity of New York at m. Afbany. New York 12222, U.S.A. (Rccehud

in USA

12 Alcgw~

1987)

coNTErvTs I. Introduction.

.

.

.

.

.

.

.

.

. ..

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

281

2. Synthesis of Mixed Organosulfur-Sihcoo Compounds . . . . . . . . 2.1. Tmatmcnt ofcarbaniom with chlorosihwa . . . . . . . . . . . . 2.2. Reaction of Womcthylailana and related compounds with sulfur ntdcophilcs 2.3. Reactions involving a-silylcubanions . . . . . . . . . . . . . 2.4. Radical substitution processes. . . . . . . . . . . . . . . . 2.5. Intmnlohcular rcarrangcmmi of compounds with Si-S or s-0 bonds . . . 2.6. Addition to alkcnyl- and alkynyl-rilancs . . . . . . . . . . 2.7. Preparation of silylthioketoocs and silylthiokctcncs. . . . . . . . . . 2.8. Hydrorilylation and miscellaneous methods . . . . . . .

282 282 284 287 288 288 288 291 293

3. Reactions of Mixed OrganosulfurSilicon Compounds . . . . . . . 3. I. Onc-dcctron oxidation of a-silybtdfidcs and a-silyltiols . . . . . . . 3.2. Dcsilylatioa of aromatic silanes . . . . . . . . . . . . . . 3.3. Halodcsilylation . . . . . . . . . . . . . . . . . . 3.4. Generation and reactions of sulfur-silicon stabilized carbaoions and ylidcs . . . . 3.5. Peterson reaction of stdfur~ilicon stabilized carbanions and ylida 3.6. Sila-Pummcrcr rcarrangcmcnt. . . . . . . . . . . . . . . . 3.7. Dcsulfuritatioo . . . . . . . . . . . . . . . . . . . 3.8. Reactions involving sulfur-ailicoanstabilixcd oarbocatiotta . . . . . . 3.9. Ionic and cooartcd additions or cydorcvcrsiona involving multiple bon& sulfur and silicon . . . . . . . . . . . . . . . . . . . . 3.10. Mixed organostdfur-siliam containing metal complexa. . . . . . .

293 293 295 295

4. References.

.

. . . .

. . . . . . . . . . . . .

. . . . . . . . . . . . . . . .

. . . . . . . .

. . . . .

:: 305 310 315

with attached 315 319

. .

.

321

1. INTRODUCI-ION

With the rapid growth during ti past two decades in the study of reactions of organic compounds of S and Si and the great utility of these compounds in organic synthesis, ” it is not surprising that the chemistry of compounds containing both elements has also attracted attention. The unique as well as complementary properties and reactivity of S and Si can be best exploited through their attachment to the same or neighboring carbons. This review will highlight those examples in which the presence of both S and Si offers opportunities, particularly in the area of organic synthesis, not available with one element alone. Illus~tions are chosen from the literature through carfy 1987 as well as from the authors’ research. , Among the properties of S and Si which affect the reactivity of compounds of these elements the following are noteworthy : Sulfur is eJec(ronegative while silicon is electropositive relative to carbon (electronegauvities 2.52. !,64 and 2.35, respectively). Al~ougb C-Si and C-S bond streugths are similar, Si forms much strong bonds to halogens and oxygen than does S (bond dissoc&ion energies (kcal mol-‘): CH$-Cl. 70; (CH,)2S+4-, 87; CH$-CH~, 77; (CHJ&Cl, 113; (CH,),Si-Br, 96; (CH,)$i-OCH,, 127; SiF,-F, 160; (CH&GCHr, 761b). Bonds betweeu S and C, as well as other bonds to Si, can be easily cleaved upon exposure to F-, Cl- or RO-. Cleavage of the Si-C bond by nuckophihc attack at Si is 281

particularly facile when electron-withdrawing groups on carbon make Si electropositive. In these situations the silyl group behaves as a proton. Ic Divalent S shows a great affinity for heavy metals such as Hg, Ag, Pb, Ni and Cu. Sulfur exists ih a diversity of valence and coordination states which can’be interconverted. C-S bonds can be cleaved with dissolving metals such as Li or with Raney-Ni. Divalent S can stabilize adjacent anionic, radical and cationic centers. Si can stabilize adjacent carbanions as well as cationic centers adjacent to“’ or one or two atoms removed from Si (e.g. Si-C-C+ and Si-C-C-C+). The choice of base is critical in’ forming esilyl carbanions by adeprotonation since the C-Si bond polarization favors nucleophilic attack at Si, particularly when the C-containing moiety is a good leaving group. Carbon and nitrogen bases are favored for adeprotonation although both types of bases (e.g., n-butyllithium, sodium amide) occasionally cause desilylation ; oxygen-containing bases are to be avoided because of their afhnity for Si. The stabilization by Si of cationic centers one atom removed, termed the b-effect, is optimum when the developing electrophilic 2p orbital eclipses the C-Si o-bond. Trialkylsilyl groups provide steric hindrance particularly when substituted with one or more rbutyl, isopropyl or phenyl groups. The trimethylsilyl group is thought to be effectively smaller than the f-butyl group due to the longer C-Si bond length compared to the C-C bond length.” This review will emphasize those compounds containing sulfur and silicon attached to the same C atom (a-substitution) ; compounds with a more remote relationship between these elements (B-, y-, S-substitution) will be given limited attention. This subject has not been previously reviewed, apart from brief summaries of a few classes of compounds. ua The broad area of the chemistry of compounds containing directly bonded sulfur and silicon has been treated elsewhere’” and will not be covered here. 2. SYNTHEB

OF MIXED

ORGANCEULJURSILlCON

COMPOUNDS

A variety of procedures have been reported for preparation of simple S-Si compounds. These will be illustrated below. 2.1. Treatment of carbanions with chlorosilanes This procedure, first used almost 40 years ago by Benkeser and Gilman (eqn la2, 23), enjoys the dual advantages of drawing on a diversity of conveniently prepared carbanions as well as a wide range of commercial@ available alkyl and aryl chlorosilanes and polychloro-silanes or disilanes. Examples include silylation of carbanioris from thiophene (eqn 13, saturated and unsaturated

mp 246-246’C

suwdes (eqn 3-8&p, a-toluenethiol (eqn 9’7, thioacetals (eqn lo”, 14’3, sulfoxides (eqn 11’3, sulfur ylides (eqn 12”) and sulfones (eqn 23, 13 “.‘**3. Multiple silylation (eqn 55*‘5, 12”), is promoted by the carbanion stabilizing ability of silicon as well as the basicity of the a-thiocarbanions or ylides. Other examples include generation of an a-lithio-a-alkenylsulfide by reductive lithiation of a ketene thioacetal using lithium naphthalenide (eqn 89 and generation of a /I-silyl sulfone through reaction of an a-sulfonyl carbanion with iodomethyltrimethylsilane (eqn 13”). In some instances silylation is best achieved by addition of the carbanion to excess clilorosilane (inverse addition t eqn 11 12). Heterocyclic a-silyl sulfur systems have been prepared by coupling biscarbanions with dichlorodimethylsilane (see eqn 82 belo~).‘~ In our own research, we sought a methanethiol carbanion synthon (HS$H;) which could be used to prepare bis- and tris-(trialkylsilyl)methanethiols, of interest ais.hiiidered ligands. While direct generation and silylation of the a-toluenethiol dianion has been described by Seebach (eqn

Ph,SiCI

CH,-@SQ$+t,Li

PhSCH,

MesSi Cl

(4P

mSCHLiCHIC%h

We3

66%

CH,S CH,Li

!!d+k!2) Ye$iCI

b3s’c’

.

CH,SCH,SiI*,

(51’

CH$ CH ( SIYe&

em

=

(31’

Ph S FHCH KH,)2

CH,S CH3 m

PhSCH=CHt

FlISCt$SIY% 95%

1w

-

(2)'

~~so2cHLSl~, 31%

PhSCH2Li e

p-9uLi hmne-ether nflux 16h

mscHzcti(ct@,

-

=

PhSCLi=CHn

;;>

CH, 3

PhS(0) Me$i +CH2 90%

(6)’

97%

ArSCH=C=C(CH&

mph

~!;;th.,

~~7”

tMiCt

_ msph

LI

SFI!

SiYe,

(d

91%

PhCHzSH

C”>c,

n-BuLi TYEW,THF a-BuLi

PhCHLiSLi

THF,_m

0 (Ye2{CH14Si

PhS(O)C$Li

s SiYe, cs>c 60%

Li

a

LOA

PW)ICH3

PhCH(SiMe@t 73% Ye$iCI_

_

S

s

$$$oaditla

F’hS(OICtt#y5

(9)”

(IO)”

(IIf

90%

n

,-

yS,SiCI \

Ye2+CHISiYe, P

-Met!

C_HSiMe, RLi

y”,? Y SiCl LicH,~ySi&-M~-gttSW

f,cm;+

9’9, this procedure cawot be applied to methanethiol itself. Beak has published--one approach to a-lith.iom&hanet ~yn_thoppusing dip&-stabilized carbanions from thksters. ‘6 Thus &protonatipq of-my1 2,4&riisopropylthiobenzo8N gave an anion wbM4oukLk sirylakd (eqn 15 ’“, ; pm8uqMly this silyl4tad tim oould.k~~leaved tar2+imet4ylsiIy~p~ol although this is not described. We find that (2-tetrahydropyranyl)(thiomethyl)lithium 1 and (2-t~trahydrofuranyl)(thiomethyl)lithium 2 function as methanethiol carbanion equivalents (eqn 16’3. Treatment of 1 and 2 with dk+lorodim&hyGlane or once or awrltiply with chlor~tri~~ f&owed by by&&i~ with @vat or mqzcury salts aflbrds dithiol3 or thiols 44 (aqn 16, 17’7-).Treatment nfl~m&b

bdtu

&urpAiAlSAII

I7

(13)”

(14)”

ArC(OlSCHY66

-f&@&q

ArC(OISCLiYsL

ArC(OlSC(SiY6~~Yez

-----

-3

31 u6’

I-Bulue2SiCI THF-HMPA,+Wf ii1

m

(15)”

N62(M66Si)CS14

-3

u

I

IIAgNO, 2)HzS

(IS)” *

Ye$i

3

‘M6

(&siT

WV

+-BuYs2SiCH2SH

12

1

(CH2SH)2

4,77%

/

[ 1-BuYe2SiCH2S-]2 0,77x

c),

0

ii -I

S

I) !- BuMe2SiCl 21 I- BuLi,THF-H&h 3) I- Me2 SKI

0 m0

0, 0

91%

Me

Me

‘)bL’;kmI r),

2) Repeat

/\S,Ye5

w

0

(171”

S-C(SI Ye515

83% HgCl2 c;H,a_qO

(Me3S’)3

CSH

6,80X

We also employed the tetrahydropyranyl group to generate the ortho-lithiothiophenol synthon 9, which could be converted into silylakd thiophenols 10 and 11;’ (&p 18 Ia). Dilithiation of thiophenol itself (giving 12) ‘8*‘9followed by silylation and hydrolysis of tht Me&S group also gave thiophcnol 11 .w.hich could be converted itlto 2,6~bis(trimethylsilyl)thiophend 13, of interest as a hindered thiol tigand. A number of other novel siliconcontriming’ thiols can be prepared by these procedures. 2.2. Reaction of haZomethylpilanesand related compounds with st@tr mtcleophiles The reaction of iodomethyhrimethylsilane with a-sulfonylcarbanions to give B_silyl sulfones (eqn 13) has already been not& Halomethvltrialkvlsilanen alnn rcwt with nltrlmnhi+~~ adfilr an;nnc

Me$Xl

1-Bul,i THF-HUPA - 90 OC 9

H$&;H2S I SH SiM%

Iln-8uLi

_

MesSi

SiMe3

21M+iCI 12 Me#iC12 THF, -78’ \

IO

such as sulfide ion (eqn 1920, 202’), alkanethiolates (eqn 21 20), thiocyanate (eqn 2222), hydrosulfide (eqn 2323), and thiophenoxide (eqn 2424) to atford in good yields silylated thiols, sulfides, or thiocyanates. imese can be converted by standard procedures into silylated sulfones (eqn 192”), disulfides (eqn 2323) and sulfonium salts (eqn 26 2’ , 21a”). L Dialkyl sulMes can also be used as nucleophiles ; however displacement of the leaving group on the a-silyl carbon is slow and side reactions ensue unless particularly active leaving groups such as Mate are employed (eqn 252’, 2626).

h$SiCH$l

*

Me3SiCH2SCHISIMe3

zoz

c (Ye3SICt1212

71% Ei3S+CH2CI

i&i!$&

SO2

(l9?

59%

fEl,Sl’OH212S

A

(Et3SICH2)2

+ SMe I

(aof’

76% CHxSNa

ruSSi CH2CI

*

MeSSiCH2SCH3

-

Mel

Me3SICH&MapI-

(2P

67% No SCN EfOH *

Ye3SiCH2CI

Me3SiCH2CI

Me3SiCH2

-

KSH

Ye$iCH2

PhSNa

Br

r22P

k3siCHzSCN 61%

~

SH

IelK NaOH

-

(Me$iiCH2S)2

k3SlCH2SPh

(23)23

(24)24

74% Me3SiCH2

I

Ye2S

MefSiCH2SMe h3SlCHzOSO2

*

Ye3SiCHi

+ Me3S*

CF3 + E-C,&

iMe,

I-

a

ISph s

(25j2’ n-Cl~H~$(Ph)CN2SiMeB Ch 90;

(2wB

Nucleophilic displacement of a-substituted silanes by divalent sulfur anions has been used in the synthesis of organoSSi heterocycles such as trimethylsilyl-substituted thiiranes (eqn 27*‘“, 28”*), 3,3dimethyl-1-thia-3-silacyclobutane (eqn 2928),3,3dimethyl-l-thia-3-silacyclopentane (eqn 3024, 3,3dimethyl-1-thia-3-silacyclohexane (eqn 31 29*30)and 3,3dimethyl-I-thia-3-silacycloheptane (eqn 3230).

70%

50%

65%

ps”yj7 +

&S

CF3COOH,

“3’p

+

@&O

(2*‘m

53%

Mc,Sl(CH2Cl)2

E,;$O,

e

(29P

Me2Slv -S 55%

f’

HOS

MO2Sl

[

M.,J-4, ] - Me2SrJ 60%

/-h

Na$

IYe29

VVB’

we9

EtOH-H20 Rtif lur IQl

(32?

Me

Me 12%

We have used the litkio derivative of chIoromethyltrimethylsilane, discovered by Magnus,3’ to prepare a-(chloroalkyl)trimethylsilanes, which can be used in the synthesis of various thiols, sulfonic acids, sulfonic anhydrides and suIfony1 chlorides (eqn 3332). Commercially available chloromethyltrimethylsilane was also employed by us in direct syntheses of (trimethylsilyl)methanesulfonyl chloride (eqn 3433), (trimethylsilyl)methanesulfinyl chloride (eqn 3534), bis(trimethylsilyl)methyl disultide (eqn 3534) and S-(trimethylsilyl)methyl thioacetate (eqn 3535). Attempts to chlorinate 14 or the thioacetate of 15, using chlorine in acetic anhydride or water, to afford the corresponding sulfonyl or sullinyl chlorides, lead to cleavage of the Si-CHR bondV3’ Ye3 Si CH2 Cl Me3SiCHR

m-

_

Cl

Me3SICHRSH

BuLi

Me3SICHLiCI

INH2)2C= S +

m

R1

Me3SICHRSC I4

(33P

-

( N+)= NH;Cl-

Hoi: 3

L

Ye3SiCHRS03H

I5

Me3SiCH2C’

I) (NH2j2 2) c,,,H,o

C=S

Me3 SlCHzSOp Cl 58%

(34)33

Li&

Me3SiCH2CI

,THF

*

(Ma3SICH,,S), (35)“*

709: KSAc

Me3SICH2CI

_

Ye3SICH2SAc

2.3. Reactions involving u-silylcatbanions a-Silylcarbanions stabilized by silicon, as well as carbanions /3 to silicon can react with various electrophilic S compounds in a synthetically useful manner. Thus, we36*37and others38*39developed an alternative synthetic route from that shown in eqn 17 to t.ris(trimethylsi1yl)methanethio1 (eqn 36) and related compounds based on the reaction of a-silylcarbanions with elemental sulfur. Attempts to employ this reaction iu the preparation of bis(tximethy1si1yl)methanethiol led to a poor yield, with the major product being bis(trimethylsilyl)methyl sulfide (eqn 37”‘). We postulate that bis(trimethy1si1yl)methyllithium reacts with the initial Ss adduct at sulfur as shown.” Brook” used the reaction of (trialkylsilyl)methylmagnesium halides with suEnate esters in the synthesis of unstable silylmethyl sulfoxides (eqn 38). Reaction of /?-(trimethylsilyl)ethanemagnesium chloride with sulfuryl chloride gives 2-(trimethylsilyl)ethanesulfonyl chloride (eqn 39’3. A variety of mixed organoSSi compounds have been obtained through reaction of (trimethylsilyl)methyl-

(Mo~SI)~CH

MeLi THF

-

So ;H+

(Me3Si13CLi

c

1Ye$i)3

B6Y-m

CSH

46%

(Ye3Si)2CHZ

L-&ILI

(MesSi)eCHLi

(Ye$$CHLi_

M

( e3Sih

-k

CH-S-CH

(SiMe&

+ (WJ,SI)~

489:

R,SICH,Yg

II Ar SOMe

X +

CHSH

27k

! RsSICH2SAr

-

sopCl2

MesSi CH2CHz MgCl

(37)‘O

(Me,Si),CH-S-Sj

50%

-

(3814’

(391’2

Me3SiCH2CH2W2CI 50%

(4oI43

Me3SiCH2S02H.

A

2H$

)

Ilk3SiCH2SO~CH2StMcS

(3%)

+ Me,SlCH2SO#

(Me,Si)s

CLi

T

SO2

(MesSI)

C- SiNa3 i-O-Li+

[

Me’Si

SOzCIa Py,hv

-

0”

Iye3 SiCH2SOeCI 53%

1 -x

0-’ (Ma3SI)2

C=S’ +

(411rw

288

E. BLOCK and

M.

ASLAM

magnesium chloride with sulfur dioxide or N-sulfonyl amines (eqn 4t143).For many of the compounds 29Si NMR data are provided.$* A remarkable reaction has been described by Zwanenburg*4 involving the reaction of a-lithiosilanes with sulfur dioxide (eqn 41). M~hanisti~ly this reaction is analogous to the Peterson olefin synthesis which will be discussed below. 2.4. Radical substitution processes Irradiation of a mixture of tetramethylsilane, sulfuryl chloride and pyridine affords (trimethylsilyl)methanesulfonyl chloride in 53% yield, most likely via a radical substitution reaction (eqn 4245). 2.5. htrantolecdar rearrangement of compouncis with Si-S or Si-0 bon& In I972 West reported a novel I,Zanionic rearmngement of silicon from sulfur to carbon (eqn 43’$). The reaction can be reversed under free radical conditions and can be used with silylated derivatives of ~tha~t~ol (eqn 4446) as well as other thiols (eqn 4547, 4640). We have used the reverse reaction in a convenient synthesis of bis(~me~ylsilyl)methanet~ol (eqqn47j6). An example of a reversible l&anionic marrangement of silicon from oxygen to carbon (eqn 484p has been reported by Rucker.

PhCH2SH

=

66%

PhCH 2 SSiMe 1-BuLi 3 -100% I

(43146

Ph~HSSiMe3

I

vt,SiCl

\

P Ph $H SSi Me3

PhCH S SiMe3

PhfH SS&k3

~

I * Al8N

PhCHS*

SiMs3

&_.A

PhCH SH

100 *c

!kYsj

CH3 S SI Me2 tau

$tEt3

bs3

t- BuLi;

H+

-

t-Bu

Ma2SiCH2SH

(44146

LDA;H+

(4514’ Si Me3

Ue3SiCH2S

Sit&$

f Md,SII,

LDA’H+w

CHSH

(4614*

19% (Ms3Si

I3 CSH

23O*C_

(Ms3Si12CHSSiMe3

-

ti+

1471=

( Me3Slh CHSH 65%

a

(46148 03SIMa3 8’ ‘EH SPA

-0”

z=== cf-

+iPh SiMs3

-

k+Ph SiMe,

2.6. Addition to alkenyi- and alkynyl-silanes Since the early studies by Gilman and others on thiol addition to vinyl silanes, diverse procedures have been used to add sulfurcontaining reagents to unsaturated silanes giving mixed organoS_Si compounds. Of the various procedures involving radical intermediates, thioacetic acid addition is reported to give both the terminal as well as internal adduct of vinyl ttimethylsilane (eqn 4944. Alkaline hydrolysis of the thioacetate adducts affords the corresponding thiols. The j&effect of silicon may be responsible for formation of the internal adduct since thioacetic acid rarely adds in

Chemistry of mixed organwulfur-&ic

289

compounds

this manner to other terminal &tins. Vinyl siloxanes also add Ehioacxtic acid and tbiols (eqn 50”‘). On a competitive basis vinyl silanes with oxygen-containing groups on silicon show diminished activity relative to their ~alkylsilyl ~ounte~a~s.4g t49t9 Me3SiCH&H2SH t NoOMa/MaOH MaJSlh

CH2SAc =

Me3SiCH2CHzSAc 90%

Ma;SiCH+CH;! Ma3SiCH@AdC~~

Me$iCHfSAc)CH3

, 10% I ~OMa/Ma~ Ma3SiCHfSH~CHJ (CH2=CHSlMe2)20

AcSH’oH~‘H’..

( HSCH&H@IMe2)2

(5OP

0

56% H&S, hu _

M4,Si ~CH2~4 CH =CH2

~~M42SicH~c~

HscH*c~

(51 P’

MesSi (CH2$,+2 SH n=O,2l%;n=1,74%

-78T

Ma2yiCH = CH2

-

(53153

OC(O)CH$H

60%

Addition of hydrogen sulfide to unsaturated silanes has been rep&ted (eqn 51 ‘I) as has intramolecular cyclization under radical conditions of unsaturated silanes with remote mercapto groups (eqn 52’*, 5353). The reaction shown in eqn 52 is a nice ilI~~ation of the use of sulfur in the synthesis of medium ring organoSi compounds. In this instance sulfur is removed and a double bond is introduced using the Ramber-Biicklund reaction. Thiols also add to alkynes under radical conditions. The ~~~hernist~ of both the initial and subsequent additions depends on the substituents present (eqn 54 54, SS’ 56”). Whilethe n-butylthio group controls the direction of radical addition to l-~-bu~It~o-2-(~~thy~~yl~~~e (eqn 54), steric &wts as well as the silicon @lbct determine the regiochemistry of r-butylthio radical addition to l-t-butylthio-2-(trimethylsilyl)ethene. In the case of radical. addition to ~-(t~~thylsilyl)e~~y~~n~ne (eqn 5555) re~~hemist~ is determined by the phenyl group. Radical or Lewis acid catalyzed addition of sulfonyl halides or pentafluorosulfur bromide to unsaturated silanes is also a synthetically useful procedure as illustrated by eqo 57s6, 5gs6, 5gs7, and 605*. R$iC*Ctt

a

R~S~CH(SR’)~H2SR’

R$iCH=CHSR’

R$iCH$t

(Sl?‘)rl B

R Ma Et

R’ &-Bll !. - 8u

%A 95 0

Et

kleC(O1

melor

%B 5 JO0

1!iP

290

E. BUXK and hf. ASLAM (L-BUSH ht ,6V,3Oh

Me3SiCrCPh

Ye,SiC m CSiMe3

’

_

39%

-BUSH hr. 60’

Me3SiCH = CH2 v

f55P

MesSi ta- BUS 1 C = CHPh

*

KIS)“~

No Reaction

MesSi CHCICH2S02Ph m

(El-Me3SiCH=CHS02Ph (57156

Me3SiC = CSlMe3 p Me,Si CH = CH2

Me3SiCrCS02Ph

SF5 Br 25’, Ih

c

(SOP

We$i C;;;CH 2 SF5

Me2 Sl(CH2CH =CH2)2 v

Me2Si (~H2~Br~H2S02CH28r)2

Me2Si(CH2CH:CHS02CH2Br)2

KOt-

x

Me2Sl (CY~CHCH=CH212

(611gs

38%

The ‘vinylogous Ramberg-BMhmd reaction’ has been used by us (eqn 61”) to convert diallyldimethylsilanc into bis( 1,3-butadienyl)dimethylsilane. We have also devised syntheses of meso1,2-bis(trimethylsilyl)-1,2_ethanedithiol and trans-2,3-bis(trimetylsilyl)thiirane based on reduction of the bis(~i~na~) produced by addition of t~~yanogen to (E)-1,2 bis(~me~ylsilyl)e~ene (eqn 60’0). In our work, it was necessary to conduct the additionof thiocyanogen in the presence of tin to prevent formation of isocyanates. The thiirane is thought to result from displacement of a thiocyanate group by an adjacent thiolate anion. 6o Other examples of addition of thiocyanogen to unsaturated silanes have been published (eqn 636’). Thiocyanogen can add to double bonds by either a radical or ionic mechanism. (62160 Me33 SIM$

(SCN& Sn

SCN

Me3si x NCS

SiMe3

LlAl H4

Me3Sl

-

X

HS

SH SW3

NoBH4, EtOH I

ISCN)

Me3Si (CH2),, CH=CH2 ethar,,sCC1

Me3Si~~H2)n CH(SCN) CHzSCN

(63+’

na0, 1.6% ; n= I, 34%

Electrophilic addition of arenesulfenyl chlorides has been used to make vinyl sulfides from vinyl trimethylsilane (eqn 646z) and silylated enones from trimethylsilyl enol ethers (eqn 6563). The highly electrophilic reagent trimethylsilyl chlorosulfonate reacts with 1,3-bis(trimethylsilyl)-1-propene (eqn 6664) and poly(trimethyisilyl)benzenes (eqn 676’) affording novel products. Sulfur has also been introduced into unsaturated &lanes through [2,3]-sigmatropic processes leading to C-S bond formation, such as the sulfenate-sulfoxide rearrangement (eqn 6866, 6g6’). An unusual example of electrophilic addition to vinyl trimethylsilane involves the iron carbonyl catalyzed addition of elemental sulfur (eqn 70683. This is the only known example of the generation of cyclic ~lys~des from an acyclic olefin. The addition does not occur with 3,fdimethyL

291

Chemistry of mixed organosulfur-silhn compounds

Me3SlCH

=CH2

PbSC’ c

W3SlIPhS)CHCH2CI

93%

DA

PhS Me,SI

k

Sin

Mc;Bn

=M3s,+

3

(641g

PhSCH = CH2

Y

-

)=

CH2

bs,d

(65p

PhS

ClSOfSiWe3 o_ 5%

hk3si-SIMe3

*

/ye3

+

Ys3SICI

b5P

(69)67

hte3SiCH=CH2 +

+

S9

Ye3SI

FO3(CO)l2

M03Siis sb s

F@2(co&S2 i-

(70j999

+ Fs3(CO)9S2

Wlash

+

k3Slh

+

Ls2 ’

!I MssPi

+

*

Ma3Siws

s Y

Me3SI )-\ coC13~~w~Co,,

I-butene under the same reaction conditions nor does it occur in the absence of the iron carbonyl ((OC),Fe--Sr-!3+ is suggested as an intermediate). Silylmethylsulfinate complexes of type CpFe(CO)zSOICHzSiMezR, where R = Me, Ph or SiMe3, have been prepared by insertion of sulfur dioxide into &e F&H2 sigma bond.‘& 2.7. Preparation of siiylthioketones and silyWokztenes Since the syntheses of silylthioketones and silylthioketenes are unique they are treated separately. The first silylthioketone to be reported was prepared by careft$ treatment of phenyl trimethylsilyl ketone with hydrogen chloride and hydrop sulfide (cqo. 7169*7”).Phenyl(trimethylsilyl)thione is an unstable blue liquid which conld not be distilled or recrystalhxed, but could be converted into (trimethylsilyl)triphenylthiirane with diphenyl diazomethane and into phenyl(trimethylsilyl)thione

292

E. BIAXIC and M. &LAM

S-oxide with MCPBA (eqn 71). P~~l(~phenylsilyl)thione S-oxide is a blue solid, (W rn~irn~ 692 nm ; “C NMR for C = S at 6 238.8) which is stable if stored in a refrigerator.

Ph C(OiSiM~

Bis~t~methylsilyl)~one 16wasprepared by the author. 3bOur route to 16 involved pyrolysis of t~os~fina~ 17in the presence of 2,3-d~ethyl-1,3-bu~iene as a trapping’a~ent (eqn 7236). In the absence of the trapping agent the major product was the silyldithioformate 18. The mechanism for formation of 18 will be discussed below. It is claimed that decomposition of tris(trimethylsilyl~methan~lfenyl bromide also generates 15 (eqn 733&3 and that compound 15 is a

If

I) MeLl 21 Er2, -78’C

(Ms3Si)3CSH

(Me3N3C-S6r

- 1

Me3SIC(S) SEt 16 285%

A

(Ms3Si), C=S

-

(73P8

I6

redviolet oil (W maximum 530 mn ; 13CNMR 6 84.0 and 267.0) which dirndls on at~rnp~ purification by distillation or chromatography. 3&rHowever difficulty has been experienced in reproducing the results of eqn 73.’38bNorrish’type p~otofra~~~tion of the phenacyl sulfide of (trimethylsilyl)methanethiol was employed by Vedejs” to generate (trimethylsilyl)methanethial (eqn 74). The thial was trapped with cyclo~~diene giving an adduct with a 5 : 1 endo : exo isomer ratio. Ph +

0

L$s” + +sjM*3+ py SiMef 54%

Me3SiCrCLi

Sa

(7417’

Me3SiCH = S

Me3Si t=C=S

H II% Me3SlCt

- Me$jilp

t

+ Xs,SiC~C-S’

C=C=S IQ

MejSiBr

i

Me3SlCaCSSlMa3

80

r75,‘.2

293

compounds

Chemistry of mixed or~n~~f~~~#n

In contrast ,to 16, b~trimethylsilyl)tke~ne 19 is a distillable yellow oil which remains unchanged even after 8 h at 140°C (UV maximum 413 mu; ‘%Z NMR 6 0.8, 52, 214:4).” Its preparation, given in cqn 72, provides an interesting illustration of the ‘hard-soft acid base (HSAB) principle.’ Sya&e&s af another silyhhioketene appears in eqn 76??. %azaki has recently reported the ~~$.afttisCttimethy~ly~~~ethi~, (Me,Si)&CHS (UV maximum 518 nm, I36 NMR 6 2.6, 59.5,248.2, ‘H >NNMR 6 0.26 (27H), 11.45 (1 H)).73* 2.8. Hya’rosilylation and miwellawous methods Voronkov et al. have developcul a synthesis of 3,3diethyl-2,4dimethyl-3-sila-I-thietane via Ptcatalyzed hydrosilylation of divinyl sulfide (eqn 7’7‘**“) _ A novel mixed S-Si-P heterocycle whose synthesis from carbon disul&Je defies categorization is shown in eqn 78”. Another condensation reaction involving carbon distide and a chlorinated silane has been reported (eqn 79’6). (771”74

ElLSlH (Ph3Pl3RhCI

MeCHkSA

lOOI

*

Et2SI

(Ph,P), RhCl _ 100°C

EtpSibS4

S Y E% e A

Et2Si

US mtnor

4 Me3SiS, 2.C$++

2LlP(

SiMe312

+ 2Ma3

SKI

-78oc

c

E,hsr

rc-pu P, ,C-SiMs3 s + 2LiCl

CS2 +

M83SlCH2CI.+

C6H5

A’C’3

* 2(Me3Si12

*. PAC 61 SCH2 SIMe3

(7e)75

S

f?9T

43% 3. RkXCTiONS

OF Ml?ED Oi?hNO!WLiWR-STIJCON

COMPOUNDS

3.1. Une-ejection oxidation of ~-si~y~~~~s and a-silyZth~o~s The facility with which Si stabilizes cationic centers one atom removed (e.g. S&C-C+ ; the silicon /I-effect) suggests that one-eiectron oxidation of a-silylsuhides should be facile. An ESR stucfy by Sakurai” of the cation radical from methyl (trimethylsilyl)methyl sulfide, Me$iCH,SMe+, generated by 6oCo y-irradiation of the sulfide in frozen fluorotrichloromethane (Freon-l 1) solution reveals that the cation radical adopts a conformation in which the Si-CH2 bond eclipses a sulfur n-type nonbonding singly occupied molecular orbital (analogous to 21, eqn 80).77*780A significant amount of spin density in the cation radical is delocalized onto the Si--CH2 bond.77 The stabilized cation radical prepared from ethyl (trimethylsilyl)methyl sulfide by single electron transfer (SET) from photoexcited 2-phenyl-1-pyrrolinium perchlorate undergoes nucleophile-assisted loss of the trimethylsilyl group giving the ethylthiomethyl radical which is trapped (eqn 8078’3.

=

[EtSCQ) -

22

a= Ph

H C&SEt

23

294

E. BLOCK and M. ASLAM

Two research groups have examined the electrochemical oxidation of 1-phenylthio-l-(trimethylsilyl)alkanes, PhSCH(R)SiMe3. 786*cIn alcohol electrochemical oxidation atfords aoetals, presuinably by desilylation of the radical cation followed by subsequent replacement of the phenylthio group in the hemithiacetal by alkoxyl. 786For the compounds with R=H and n-C8Hi7 the oxidation potentials of the a-silylsulfkk (0.92 and 1.25 V, mspectively) are slightly less anodic than those of the corresponding sulfides, thioanisole and 1-phenylthiooctzine (1.05 and 1.35 V, respectively). 78b4Similarly a-methylthio-a-(trimethylsilyl)toluene has an oxidation potential of 0.99 V compared to 1.23 V for a-methylthiotoluene. ‘LUa-Trimethylsllyl groups have significantly greater activating effect on one-electron oxidation at nitrogen (cu 0.5 V enhancement) and oxygen (ca 1.0 V enhancement) than at sulfur, in accord with MO arguments indicated below. Photoelectron spectroscopy (PES) can be used to obtain precise ionization energies, for example for a-silylsulfkks or a-silylthiols (Table 1).79 We find a sign&ant lowering of the first ionization energy IPi corresponding to the radical-cation with predominant sulfur ‘lone-pair’ character in 2-(trimethylsilyl)thiirane and rrrms-2,3-bis(trimethylsilyl)thiirane compared to thiirane itself (8.44, 8.19 and 9.03 eV, respectively). A smaller decrease in IP, is experienced in methyl (trimethylsilyl)methyl sulfide compared to dimethyl sulfide (8.35 and 8.68 eV, respectively). In the silylated thiiranes the Si-C bonds are more nearly parallel to the sulfur nonbonding p-orbital than in the case of the acyclic silylated sulfur, affording maximum orbital interaction. While the geometrically-dependent lowering of IP, in silylated sulfides can be related to the magnitude of the silicon jk&ct, r-butyl groups show a similar effect as seen by the lowering of IP, in 2-(t-butyl)thiirane and 2,3-bis(r-butyl)thiirane (8.58 and 8.39 eV, respectively) compared to thiirane. Based on a comparison of the PES of a series of silylated ethers and sulfides we conclude that the lowering of IP, by silicon is greater for oxygen compounds than the corresponding sulfur compounds. This is in accord with the argument from second-order perturbation MO theory that the interaction should be stronger between the silicon-carbon 0 orbital and the energetically similar oxygen p-n orbital than with the considerably lower energy sulfur p-x orbital (IP, 10.57, 10.04 and 8.71 in tetramethylsilane, dimethyl ether and dimethyl sulfide, respectively). We also find a systematic lowering of IP, in the series of thiols CH,SH, Me$iCH$H, (Me,Si),CHSH, (MesSi)3CSH (9.44,8.96,8.55 and 8.18 eV, respectively). Replacement of the hydrogen of methanethiol with r-butyl groups also lowers IP, but not as much as with the trimethylsilyl group (e.g. t-Bu,CHSH has IP, of 8.73 eV compared to 8.55 eV for (Me$i)&HSH). The PES spectrum of 2,5-bis(trimethylsilyl)thiopheue, in which the Si-_C bonds are orthogonal to the sulfur x-type nonbonding orbital, is similar to that of thiophene and 2-t-butylthiophene.80 A TABLE I. FIRST IONIZATION POTENTIALS OF CYCLIC AND ACYCLIC SiLYl_ SULFIDES AND THKXS BY ULTRAVIOLETPHOTOELECTRON SpEcTRoscow

8

(Me$i)2CHSH

8.59

9

W%W=

8.1s?

14

15

,c*..&w

8.392

wi%+siu%

8,,92 s

‘Entdes 1-15 PES. f0.05 eV. Zrhiaworlc 3F&femnw 12a ’

%zeferenca 4d.

Chemistry

of mixed or~nos~lfur~Ii#n

295

compounds

PES study of 9,9dimethylphenothioxanthen, 22, and 10, IO-dimethylphenothiasilin, 23, in which silicon is /3 to sulfur, indicates that the sulfur lone pair ionization energy increases on going from 22 to 23. This effect is attributed to the greater degree of nonplanarity of the latter compound.*’ It has been noted that Me$iCH$H is much more reactive than other members of the series ~e~Si(CH*)~S~ in addition to acetylenes** and that (MeO)*MeSi~H~SH is more reactive than nbutanethiol in both radical and nucleophilic addition to olefins. lc These results are presumably related to the /?-effect of Si; further research seems warranted here. 3.2. Desilylution of aromatic silanes Removal of the trimethylsilyi group from silylated thiophenes by treatment with acids (eqn 81 2, is analogous to the process observed with arylsilanes. Cleavage of aromatic C-Si bonds with iodine monochloride has been used by Martin to prepare bis(o-iodophenyl) sulfone (eqn 8215’) while aromatic sulfonic acids can be prepared from aryl silanes and ClSO,SiMe, (eqn 676s).

w2 Ph,SO,

RLi,MepSiCI2 -

q$f$

fcI

$3JfjQ

(82F

59%

While some C-Si bonds can be cleaved by an ad~tion~~mination sequence as described in Section 2.2, aliphatic C-Si bonds bearing electron attracting groups on the a-carbon or leaving groups in the /?-position can be cleaved by direct attack of halide or oxyanions at silicon. This process, which can lead to formation of.carbanions, ylides or carbon-carbon or carbon-hetero double bonds, is termed fluorodesilyation when the nucleophile is fluoride ion. The great strength of the bonds between silicon and the halogens (pa~i~ularly fluorine) or oxygen provides the driving force for these reactions. Intramolecular oxyanion-induced C-Si cleavage processes will be discussed separately. The first examples of the use of halodesilylation to produce sulfonium ylides was reported by Vedejs. 264Thus formation of I-dodecene via an o$‘-elimination of an intermediate ylide is shown in eqn 83’& (see eqn 26 for preparation of starting material). Cesium fluoride is favored over the less expensive potassium fluoride (or the combination of KF-18-crown-e) because the former is more soluble in polar organic solvents such as acetonitrile and gives better yields. Low yields are obtained with tetraalkylammonium fluorides (e.g., tetrabutylammonium fluoride or TBAF, commercially available as a THF solution), presumably because of the presence of traces of water which can be removed only with difficulty.266 In our own experience with cesium fluoride, we find that this salt works best if it is placed under vacuum in a Aask equipped with a septum and heated briefly with a Bunsen burner to remove traces of moisture. Acetonitrile, distilled from P20s, is the preferred solvent. Reaction yields can be substantially reduced by the presence of traces of water, alcohols or other hydroxylic compounds which can hydrogen-bond to fluoride ion or quench reactive intermediates. A-9’2 -n_-

CloH,,CH=CH2 75%

+ PhSCH, 77%

A second example of an ylide formed by fluorodesilylation (eqn 84*&) demonstrates the minor role played by ylide equilibration since reactions involving the kinetic ylide dominate. On the other hand, recent w&c by PaduLa” indicates tU ylide ~~~bration is possibIe in related systems (eqn 85). Both sulfonium salts afford the ortho-substituted benzene formed by [2,3]-sigmatropic rearrangement of the less stable ylide. In the presence of aldehydes both sulfonium salts afford the same epoxide, formed from the more stable yfide. Halodesilylation followed by a [2,3]-sigmatropic rearrangement is invoked by Gassman to explain the products from reaction of methyl (trimethy1silyl)methyl sulfide with benzenesulfenyl chloride (eqn 86*‘).

E. BLOCK and M. ASUM

2%

(641Z PhCH=CHCH2+H2C02Et

=

PhCH=CH-CH2-

kX2C02Et

TsPhCH=CHM$

---

l-b,

CH2SiUe3

CttC02Et

I Me 1

I PhCH CH~SL)

PhyHCH2SCH2C02Et

C02Et

CH = CH2 9%

81%

=

PhCH ;Ue,

Ph&d12

fasf

PhCH2&2

(85f3

PhCH2;CH2SIYe3

_Csf

SiYe3

1 RCHO

’

H

Ph H

R

phscl

He3SICH2SYe

~e[~~~;~~m~$Pt”

Phs-•ye

_

[2,31

PhS-*Sk

9

(t#

I _

Thiocarbonyl ylides have also been prepared by halodesilylation as illustrated by the dihydroand tetrahydrothiophene syntheses shown in eqn 87 *’ and 88s6. The latter reaction represents the first generation of the parent thiocarbonyl ylide, thioformaldehyde S-methylide. In the former reaction a trimethylsilyl group is replaced by hydrogen through the use of cesium fluoride in HMPAH20.

Ma3SiCH2SCH2SIL3

(87F

Y~3SICH~2SCHB~SfY~3

L

98% llOe,DYF

w

-

CH~=$-CH~~YI~

flil

Ph 6

[ b3~Ic~23.~~~I~~3]

0

0

0 c

NFh

S cc Me,;

CsF HYPA-H;?D-S

NPh x

0

O 95%

Ye3SJCH2 SH

+

[bt$=CH2

a

-

k3StCH2SCH2L’

CH2=S*iH2]

-

C,F,CH$M,25'C ~~0 cc~cc02~2

s~C02w* COLM 56%

CertP

Chemistry of mixed or~n~~f~r~i~~n Ne3Si

RLl ; c

\7

SO,Ph

‘*@,Ph

~‘,‘,i

mCH@

Ne3si\

291

compounds _

( 89?’

SOZPh

Q,;

.TBAF

.<-,“ih 2 59%

In appropriate systems hal~e~ylation has been used to initiate /I- and y-elimination of chloride (eqn 6462 and 8987) or benzenesuhinate, e.g. eqn 9014 (eqn 131,915’ (eqn 57), 92s*, 9368 (eqn 70) and 94.89 Application of the sequence of eqn 92 to more complex systems leads to problems due to TBAF,THF,A

Ne3Si +

s~ph

+

m 98%

Si Ye3 TBAF v 56%

Me39i\

so2m

n- BuLi; PhCH21

,.,,,~

(93P

Ph TBAF _

S%Ph

95%

-Ph 95% OH

TBAF a?=

(94P

KH 18-crown-6 S02Ph 94%

83%

EtAICI;

the lability of the tertiary homoallylic j?-silyl su.If’es which ionize giving undesired side products. ** The /?-effect of silicon is thought to be responsible for the facile ionization of the C-S bond.** The sequence in eqn 9542 (eqn 39) represents a novel method for protecting amines as j?-silylsulfonamides.

E. BLOCK ad

298

Ye$i

RR'NH

q/SO$l

*

NoH

TBAF/CH$N/rtflux

ti

01 CsF/DMF/95'

M. ASLAM

Ye3Si/CS02NRR'

RR'NH + SO2 t C2H, t MesSiF

Me3SICHRS02X

X= Cl or 0S02CHRSIMa3 R= H,Me or Et

We reported the first examples of the use of fluorodesilylation to generate carbon-hetero double bonds, e.g. the CL!3 bonds in sulfenes and sulfine. 3533,90Thus, treatment of l-(trimethylsilyl)alkanesulfonyl chlorides or -sulfonic anhydrides with cesium fluoride in the presence of cyclopentadiene gave the cyclopentadiene-sulfene adducts 24 in good yield (eqn 9632,33,90;see eqn 33 and 34 for syntheses of starting materials). Adducts 24 with R = Me and Et were endo/exo mixtures with the endo isomer predominating in each case. Attempts to prepare sulfene adduct 24 using methanesulfonyl chloride-triethylamine as the source of sulfene failed, possibly because the amine intercepts the electrophilic sulfene at a rate faster than capture by cyclopentadiene.33 Treatment of (trimethylsilyl)methanesulfonyl chloride with a mixture of cesium fluoride and bromine gave a mixture of bromomethanesulfonyl chloride and bromides9 (eqn 9733). Control experiments established that

BrCH2S02Br

+

BrCH2S02CI

no reaction takes place in the absence of cesium fluoride. Once again, attempts to conduct this reaction employing methanesulfonyl chloride-triethylamine as the source of sulfene failed due to competitive bromine-amine adduct formation. 33 The above observations underscore the advantage that can be realized with mixed S-Si systems giving results sometimes not possible in the absence of Si. At times, fluoride ion can function as a base so that fluorodesilylation does not always prove advantageous for regiospecific syntheses (e.g. eqn 9833; the same results were achieved albeit in lower yield, with methanesulfonyl chloridetriethylamine). Fluorodesilylation was used by us in the fhst unequivocal generation and trapping of methanethial S-oxide (sulfine) in solution (eqn 9932*9”).Krafft9’ has described the application of fluorodesilylation to the generation and trapping of thioformaldehyde and other thials in solution (eqn 1009’). The cyclopentadiene-thial adducts were endo/exo mixtures with the endo isomer

k3SICH2S02CI

+ YeC=CNEt2

+CH2'S02]-

Et2N v

MI a2

IFEt2H

yIsSiCt$S(0)Cl =

[CH2'SO]0 9:l

90%

I:1 ,u@ mlxtwa

299

Chemistry of mixed organosuWur+ilicon compounds (loo?’ RCHO

ew

YeLi;ArSCl

RCH(SiYe2Ph) SAC

RCH(SIl+Ph)

TtlAF,O'C

SSAr

0

R c’

- [RCH=S]-

s ea

R= H, Ph, or alkyl 58-94%

predominating (cfeqn 96). Key features of this process include use of the dimethylphenylsilyl group, which is more reactive than the trimethylsilyl group toward fluoride’-ion,92 use of 2-nitrophenyl disulfides to provide a good thiolate leaving group and use of tetrabutylammonium fluoride in THF, permitting generation of thioaldehydes rapidly at temperatures from 0 to - 78”C.91 Formation of thione 16 from tris(trimethylsilyl)methanekulfenyl bromide (eqn 7338) may involve bromodesilylation. Other processes involving halodesilylation include the reaction of allylsilanes with acyl or sulfonyl halides (eqn 1019’ and 6664), generation and trapping of various S-containing carbanions (eqn 1029Q9 103946, 1O492and 1059’), a novel sequence involving an adisilylsulfide (eqn 10696), and a (loI)= PrC(O)CI AM3 m2)940 Q-8uLI;

SiYe3

Me$ICI

+$&--

$$CHOHPh 0 83%

C

ErKH&CH(OiMe)2 c

s x SIMS3

SnCI4 _

t103vb

, s (CH4,CH(OYd2 -78% s cx s

SlYe3 (CH24CHO

wI)g2

TEAF

PhSCH2SIMe3 -

NCS

PhSCHCISIMe3

Pb(SCN)c

(105PS PhSCH(NCS)SIMe, 89%

KF-&N*CIPhCHO

0

PhStHNCS

-

PhS Ph x

“,r” -

Ph

%

$=C=S t O-

-

E. BLOCK and M. ASLAM

300

transsilylation reaction (eqn 10797). The transsilylation reaction is thought to involve initial complexation of the nitrogen of 26 with the trichlorosilane together with intramolecular displacement of the trimethylsilyl group by one of the chlorines on silicon.97” w6)m

SPA -‘&Ph

LAS&, 3

Me2CI -

USi

Me2Sl beg

Me30+6F’o

SiMej uSIHe2F

‘it:’

*

PhbsiMej

73%

(10719’

(i06?‘” MejSICH2Cb)OR

MeC(S)OR

_Mf:lMl; 3

MejSI CljSn

>

c=s

MeOMejSlCH2C(slNR2_~sloMe~

-MejSINR2

MeCtS)NR2

PhS

PhS 93%

The trimethylsilyl group of 26 is also easily displaced by the tert-butoxide group even at - 60°C.976Other examples of intermolecular Si-C cleavage by halides and other nucleophiles are given in eqn 10871”and 10998. Reinterpretation of the early observations of Cooper also suggest the occurrence of oxygen-initiated Si-C cleavage (eqn 1104’, 11 I 2oand 11223.

a.*-

r

CH2=S02

=

CHjSO,-

( I 101’5

Mej SICH2S02CI y

Me jSIOH

-

MejSiOSIYe3 60%

MejSiCH2

S02CHj

OH-

_

MejSiOSiMej

(+

Me2S021

(lll)2o

100%

MejSICH2

SCN

OH-

*

MejSiOSIMej

(+ (CH$),,

+CN’)

(lr2)22

93%

3.4. Generation and reactions of sulfur-silicon stabilized carbanions and yli&.s Mono- and dianions or ylides jointly stabilized by S and Si can bc conveniently prepared by deprotonation with alkyllithiums, by Michael or ‘heteroconjugate’ addition to olefins geminally substituted with silyl and sulfonyl groups, or by reductive cleavage of silylthioacetals. The carbanions

so produced can be alkylated, silylated or oxidized and can undergo Michael addition or [2,3]sigmatropic rearram in analogy to other c&anions. Reactions of the earbanions with oxygen-containing partners can occasionally lead to unusual Its_silyl group shifts which can be of synthetic utility. The unique reactions that occur on addition of ~-~yl~r~ons to aldehydes and ketones will be considered separately in Section 2.5. l](j’O’and 117’05. Examples of the above reactions are given in eqn 11399-1’31, 114102,115’0W33, The reaction depicted in eqn 116 is an example of ‘heteroconjugate addition’, (addition of a

Ul41@2 (MsS12 CHLi

‘*3RficI ’

fYsSI*

c-

i MeSl, CLI Silas3

f2

C(SMe)p

I Ma3Si

Ai MS3 SW3

Ck S

Si X83 Li

$Jo4 N

c:+z) Xa3Si

/ 9%

bQh s Nc3Si 66%

~~~leop~iie

to an okfin conjugated with heteroatoms such as S, Si or Seio4) and will be discussed in a later section. In eqn 117, the anion prepared from an allylic s~~e~s~de reacts with electrophiles at the y-rather than a-position. lo5 The sequence in eqn 118 ‘Ok is claimed to represent the first preparation of the ‘en01 ether of a sulfone’. In this author’s opinion, the preferred representation of

302

E. BLOCK and M. ASLAM

the latter structure would be an ylide (eqn 118). When the anion of 2,2,4-tris(trimethylsilyl)-l,3dithietane 1,1,3,3-tetraoxide is treated with bromine (eqn 119”@) rather than a silylating agent

3

MoJSIOSO~C~HS, (%

ye3si

Et3N

( l18fos0 k3$

-_(s>siyd3

C F * 249

02

2

i$$02C4F;

~3~~~$SiMe3 3 O* ‘OSiMe3

+

ii2 ::,“,:xs> SiMe3

3

O* ‘OSiMe3

( l191’06b

complete loss of the trimethylsilyl groups occurs. Formation of a crystalline geminal dilithio compound is shown in eqn 120 lo7. The progress of the lithiation can be followed by 13C NMR spectroscopy. The starting material shows a CHI carbon resonance at 6 48.5 (attached protons appear at 6 2.85), the monolithio compound shows the CHLi carbon at S-33.8 (proton at 6 1.20) while the dilithio compound shows the CLiz carbon at 6 505”‘The observed changes in 13C chemical shift parallel those found in the series methane, lithiomethane, dilithiomethane. lo7 In the reaction depicted in eqn 121 lo’, the intermediate lithium alkoxide undergoes a 1,4-silyl group shift generating a new C-Li intermediate which subsequently cyclizes to a 1,3-substituted cyclobutane. lo8 We have adapted this type of reaction to the synthesis of 3-mercaptocyclobutanol and 3-deuterio-3-mercaptocyclobutyl tosylate. log Fluorodesilylation is used in eqn 120107and 122”’ Ye3SICH2S02Ph

(120)‘07

n- BULI

-

Me3SiCHLIS02Ph

w

Me3SiCLi2S02Ph

Br (CH2)1Br

SO;! Ph

S02Ph SiYe3 81%

PhSC(SiYe312

0 WC1

Li +

98% (121)‘oe

Phm,,

-

Me3Si?Ma3

.,;&;

OSIlde3 Ph -

Li

PRS -# Me3Si 49% wdog

OSIM%

A-.

Cl -

THPS

Q

TBAF: c H&‘12;H_CS

Me$ii

D

OH

HS

TBAF.3D20 B20 00

OTs

THPS 0

cl

Chemistry of mixed organosulfur-silicon

303

compounds

replace a trimethylsilyl function with a proton or a deuterium atom (if traces of H,O in the TBAF are rigorously replaced by D20 prior to use ’ “7. An unusual type of 1,4-silyl group shift is represented in eqn 123.“’ to

023P

65%

SiUg 6%

!&containing S-ylides have attracted attention because of the great utility of ylides in organic synthesis. Dimethyl oxosulfonium (trimethylsilyl)methylide has been described above (eqn 1213). While this ylide does not react with cyclohexenone, the corresponding dimethyl sulfonium (trimethylsilyl)methylide 27 reacts nicely affording reasonable yields of silylcyclopropyl ketones (e.g. eqn 124’ ’ ‘). The only deprotonation conditions that gave satisfactory results in eqn 124, according 0 =BuLi THF,-55’C

Ye3 SICH2 &de2 I-

*

Me3SiCH;Ye2

-

(124fl”

o* /

27

0 SiYe3

0+ 55%

Magnus, were set-butyllithium/THF. Millerz5 has previously prepared ylide 27 using n-butyllithium in ether and characterized 27 as a distillable liquid (bp 51-53”C/l2 mm; ‘H NMR spectrum 2.22 (6H), 0.37 (IH), -0.87 (9H)) which formed a stable boron trifluoride adduct. The complex results observed on attempted generation of ylide 27 using rerr-butoxide as base”’ were attributed by Magnus ’ ’ ’ to tert-butoxide-initiated desilylation of the dimethyl (trimethylsilyl)methyl sulfonium salt giving dimethylsulfonium methylide instead. Certain other examples of reactions involving S Si stabilized carbanions and ylides will be considered below. to

3.5. Peterson reaction of sulfur-silicon stabilized carbanions and ylides In 1968 Peterson reported that a-silyl carbanions underwent a Wittig-type reaction with aldehydes and ketones giving olefins (eqn 125’13). Carbanions cooperatively stabilized by both Si and S have been found to function particularly well in the Peterson reaction as illustrated by eqn 126’ 14, 127’15, 128 ‘16, 129’03*“7, 130”8, 131’19, 13212’, 13312’, 134’22, 135’04,“7c and 13612”. The reaction

Ye3SiCHLiX

+ R$=

0

-k$IOLi

-

R2F-:HX oli SiWe3

(1251” - &C=CHX X=H,Ph,SMe, SPh,PPh2, P(S)Ph2,P(0)OEt2

Yg3SICHLiSPh

Me3SiCHLISb3)Ph

+

c=

KJB)“’

o-

+ Ph2C= 0

CHO

-

PheC = CHS(O)Ph 81%

w7)‘m

304

E. BLOCK and

Me3SiCHLiS02Ph

+

M. ASLAM

o-

CHSOzPh

(128)"6

81%

-

Ck S

Li SiYe3

/s

n-BtrLi;Me$iCI

'S

a-BuLi

0

S

Li

S

Sihlg

0

6 Ph (Me3Si)zCLiSOpPh+

65%

Ph

PhF

8

OMe -

SiMe3

Ph lw

(131)“9

S02Ph 70%

Me$iCLi I\ Me0 SPh

Me3CHCHO

c

Me2CHCH=C(SPh)OMe

I)Me SICI,NoI 21A,~03

(132)‘20

Me2CHCH2C(0)SPh 90%

S

Li

CX SiMes

_E

L

GSi.3

-20°C, O+

'r331'2'

0

J -SH (134l'22

NX Ye3SiCLI(NXlSAr

+

#=

o-

SR 76%

(Me3Si12CLiSPh

PhCHO,

*

pqhe

PhCH8rC02Et

3

Me3Si(PhS!CttCH=CH~

1-8uLi-TI(Oi-Pr),,+ OCHO

73% (136)"3p

h '

SPh

has been used to prepare unusual fulvalene type compounds (eqn 130 ’ ’ ’ ; 131’ ’ 4 and S-thioesters and a-bromoesters by homologation sequences~(eqn 132120and 135’ “1, In addition to aldehydes and ketones, both dimethylformamide (eqn 137’236) and sulfur dioxide (eqn 41) can be used as substrates. Ylide 27 and mixed silyl-stannyl anion 28 also undergo the Peterson reaction with ketones (eqn 138”‘, 139’24). In the case of 28 the silicon rather than tin is lost. Bis(trimethylsily1)

Cbmistry

Me$iCHCiSPh

+

of mixed or~os~fur-Siren

H C(O) NYa2

-

305

cornpounds

(El - PhSCH = CHNMe2

(137$23b

64% (l381”’ Ma3SiC?t&Se.2 + 0-0

-

~~~~

Me3Sio+

27 (Mc3Si)(Bu3Sn)CLiSPh

2 Bu3Sn d” Phg ‘Ph

+ Ph2C= 0 -

20

27%

sulfone 29 (eqn 140’2s) undergoes the Peterson reaction with pnitrobenzaldehyde in the presence of sodium acetate while double aldol condensation is observed in the presence of TBAF, indicating that the second fluorodesilylation occurs more easily than the Peterson reaction under these conditions. ( 1401’25 NaOAc

gqo(Me

3

SM3

LkO

Me0 xx

29

)==,*

+ ArCHO

2

c

2

0

TBAF ,,o@-$

(CH(OH)Ar12 02

Ar-P-02N-@

Three other reactions, involving nitrogen- or alkoxy group-containing silanes, can be inchrded in this section because of their resemblance to the Peterson reaction. In eqn 141”’ benzcmitrile serves as a partner for an a-silyl carbanion. The 1,bsilimn rearrangement seen in eqn 14243 may possibly proceed by dissociation and recombination steps as shown. The decomposition in eqn 14343bmay involve an intramolecular rearrangement-elimination although an intermolecular process involving catalytic amounts of ethoxide ion is also reasonable.

f-3-

-u

CH2 = $02 + M$SiNHPh

1l42l43

t CH3S02 NPhSiMs3 (143143b Ms3SiCH2 S (O)OEt

*

Me3 SiOEt + ( CH2’SO&

3.6. Sib-PWnmer reammgement The sila-Pummerer rearrangement, discovered by Brook,41 is of considerable mechanistic interest as well, aa synthetic utility. In a typical exan@c, phenyl (trimetiylsilyI)methyl s&fox& (see eqn 11’2 or 384’ -for .preparation) rearranged to phenyE (trimethylsiloxy)methyl s&de upon heating at WC, mtrsCh&&y via ylide and alkylidene sulfonium ion intermediates (eqn 1444’). Vedejs” found

E. BLCCK and

306

M. ASLAM

that the diastereomeric silyl sulfoxides prepared by silylation of the anion of benzyl t-butyl sulfoxide (eqn 145 l’) underwent the sila-Pummerer reaction at quite different rates. The major diastereomer

0-

1

Me~SiCH&?Ph

-

Me$iO -

6OoC

[

_CH2iPh

1

-

CH2= ;Ph

Me$iO-

1

(14414’

Me3SIOCH2SPh 79% (145f2 yvn, ~PhCHS!-Bu

Y-

20%

PhCH&&I

OSiMe3 2

PhCHS1-Bu 76%

(major)

rearranged more rapidly than phenyl (trimethylsilyl)methyl sulfoxide. Vedejs concluded that, being an intramolecular rearrangement, the sila-Pummerer process required the proper stereochemistry. A higher temperature is required for reaction of the minor silylation product in eqn 145 since the conformation required for rearrangement is sterically congested. He also concluded that silylated dialkyl stdfoxides are more reactive than silyiated alkyl aryl sulfoxides in the sila-Pummerer rearrangement because the electron density at oxygen ,is greater in the former than the latter sulfoxides. Carey provided additional examples of the stereochemical requirements of the silaPummerer rearrangement. ’ ‘5*126He observed that cl-2-(triorganosilyl)-1,3dithiane l-oxides 30 (146)126

t 1 R$iiG-v S

[

H

1

R=Me,Ph are stable decomp,poducts

(eqn 14612”) are stable, in contrast to the trans isomers which cannot be isolated due to their facile rearrangement. I-Alkenyl silylsulfoxides and silylthiirane S-oxides represent interesting systems for obtaining additional mechanistic information on the sila-Pummerer process. Heating silylsulfoxide 31a in refluxing benzene leads to rapid isomerization affording 31b (eqn 147’27) and slower formation during the course of 30 hr of Pummerer-type products. A reversible 1,3-Si to oxygen migration via sp2-hybridized ylide 31c is postulated.‘27 Another example of sila-Pummerer rearrangement at an sp2 carbon is shown in eqn 14866 (also see eqn 6866). Silylthiirane S-oxide 32 (eqn 14912’), in which the sulfoxide oxygen is anti to the trimethylsilyl group and therefore incapable of undergoing silaPummerer rearrangement, loses sulfur monoxide upon heating or undergoes desilylation with external nucleophiles. However even when the oxygen of a silylated thiirane S-oxide is syn to trimethylsilyl group, silaPummerer rearrangement may be precluded due to the high energy of the thiiran-rbocation intermediate. 79 Thus, rranr-bis(trimethylsilyl)thiirane S-oxide is stable up to nearly 100°C (eqn

Chemistry of mixed organosulfur-silicon

307

compounds

(l47F

H

Sib3

A

R x

Hw

Ye3SiO; H+ / (Me3Si)20+ RCH=CHS(O)Ph 19%

\

RCH=C=gPh+

-H;/ RC=CSPh

\

MesSiO' SPC RCH=C' 'OSiMe3 (32%)

37%

0 R-

S(O)Ph

3lb

3lc

310

1

TsOH,MeOH

RCH$(O)SPh

CH.$Hf c)I 0

91% (l48p

Ph

60°C

--ii7

Ph

Me3Si Ph

m Ph

32 (32%)

I

RC%H -s

m,c=c(m)s(o)sc(m)=c~

1507’q. Above this temperature it decomposes to trans-1,2-bis(trimethylsilyI)ethene. When this thiirane S-oxide is heated with dimethyl acetylenedicarboxylate thiophenes are formed, presumably by the mechanism indicated.

‘. ASi, rlCPBA

Me3Si

3

Mk$i

The sila-Pummcrer reaction is a key step in sequences which transform alkyl halides to their homologated aldehydes. The advantage of using a-silylthiocarbanions as acyl anion equivalents is the mild (oxidative) conditions required to free the latent carbonyl group. This procedure is nicely illustrated by eqn 151 r2’ and 152*W’30, among other exajnples.4~13’ In eqn 151, copper sulfate facilitates C-SPh cleavage under neutral conditions and then traps thiophenol.‘2g The cyclocitral synthesis of eqn 152*W’30 embodies a number of novel features including formation of the non-

308

E. BLOCK and M.

Me$iCHLiSPh

ASLAM

MCPBA _ CH2C12

+

CHO 70%

0&J, (I523130

Cl Me$XH#$

n- BuLi

1

Si Me3 55%

3

-2ooc 65%

I

) SMe

I

a-

CHO

L!b

Mel,

Me1

SiM%

< 25OC We

(CO~H!: ,THF

4

OSiMe3

40-60%

S(O)Me SiYe3

conjugated exocyclic olefin product rather than the thermodynamically more stable conjugated isomer with an endocyclic double bond, [2,3]-sigmatropic rearrangement of silicon-containing sulfur ylides and carbanions, and the use of a 1: 2 mixture of methyl iodide and propylene oxide to Other applihydrolyze a-trimethylsiloxysulfides’32 (propylene oxide traps iodotrimethylsilane). cations of the sila-Pummerer reaction include syntheses of cyclobutenones (eqn 153”8”), thioesters (eqn 154’33), silylketones (eqn 155’34) and carboxylic acids (eqn 156”‘). The last step in eqn 156 is thought to involve oxidation at selenium followed by a sila-selena-Pummerer rearrangement, reoxidation of selenium and hydrolysis of the selenoxy-carbonyl intermediate (eqn 157).‘35 While treatment of a-sulfinyl carbanions with silyl halides is sometimes used to prepare silylsulfoxides for

0SiWe3 Ph PCS

OAc II EtOH,H+ 2) Ac20

Me3 P i 94% Aq NO3 ’ THF-$0

Ph 72%

OAc Ph

Chemistry of mixed organosulfur-silicon

309

compounds

(154P3 PhS(O~CtlLiCI

+

Q-1

_

S(OIPh

(-J-$

LDA; MeSSi Cl

I

( I551134

a- BuLi; n-Elul

Me3SiCH(OMe)SPh

-

Me3SiC(Bu)(OMe)SPh 81%

No104 dioxane_H20~

0 [ Me$iC(Bu)(OMe)SPh]

-

D- Bu-F-SiYe,

!

00% (l56)‘35

SiMeJ CHO % 6

PhS 4

0 z

+

lMe3Si&

CLiSPh

-

0

‘e

‘+OEt

“om

=

t

=

I) MCPBA 2) MeLi ; PhSeCl

H202;

H+

M7)‘35 SiMe, PhSe-k-

0 -

SiMe3

Phte-_-

Phko;!

c 0- We3

-

PhSe-i:-

Phko,

Ph&

0 -

PhSe-k

0 -

0

Ph$&

H+

H02C

-

HO-’ (15d0 “+

YCPBA

_

Ph3Si

--we

Ph z)-slO)a 3

-

Ph sll>

SYe -

PhCHO+Ph$iOH

3

use in the sila-Pummercr rearrangement, silyl haljdes by themselves are known to cause Fummerer rearrange&‘& of sulfoxides. ’ 36 Sila-Fummerer rearrangements have been observed following addition of alkylhtbiums to silylsulfines (eqn 158”‘). The sila-Pummerer reaction of several bis(trimethylsilyl)alkyl sulfoxides have been examined. Thiocarbonyl ylides are formed upon heating bis(trimethylsilyl)methyl sulfoxide (eqn 15913’). We find that oxidation of bis(bis(trimethylsilyf)methyl) sulfide afiords bis(trimethylsilylmethy1 thioformate, probably by the mechanism shown (eqn 160138). The results in eqn 160 seem more in

310

E. BLQCK and M.

Amt.4 0

MCPBA CH2C12 ,-70°C

Ye3SiCH2SCH2SiMe3

-

(159)‘37

Me3SiCH2iCH2SiYe3 HMPA{

I

IOO’C

[Me3SiCH24=

C$

Me3SIO-]

I - (Me3Si 120 EC=

CE

[~H~-Z=CH~]

I

61%

E4,

S (E = CO,Me

or C02Et

?.

p

1

E

80% (1601t3*

0 II

( Me3Si)2CHSCH(SiMe3)2

,SiMe3 -

CH3CO$ii

(Me3Si12CHSCH,

51

,SiMe3 (Me3Si)2CHSCH,0SiYe

0SiMe3

3

?SiMe3

-

(MesSi)*

CHSCHO + (MesSi)? 0 57% OSiMe3 0SiMe3 / Me3Sii-$CH ’ SiMe3 3%

accord with the direct formation of carbocation 33b in the second sila-Pummerer rearrangement rather than ylide 33~ If ylides are involved, ylide 334~should be favored on the grounds of better negative charge delocalization than in ylide 33a. 3.7. Desulfurization The diversity of methods for desilylation have their counterpart in the range of procedures available for removal of sulfur. Hydrolysis of thioacetals, reductive lithiation, silylation, Raney Ni, base- or radical-induced removal of divalent sulfur ; sulfoxide pyrolysis ; pyrolytic extrusion of sulfur dioxide ; and base- or radical-induced elimination of the sulfonyl group are among the desulfurization procedures which find application in the synthesis of organoSi compounds. Syntheses of silylketones via thioacetal anion chemistry are shown in eqn 1614’*‘39,16214’, 16314’ and 164”‘. Silylketones can be converted into carboxylic acids under oxidizing conditions (eqn 163 ’ 4’). Applications of reductive lithiation in the synthesis of a-silyl carbanions are given in eqn 1659*‘43, 166’44and 16714’. In eqn 165 lithium I-(dimethylamino)naphthalenide (LDMAN) is recommended by Cohen as being superior to lithium naphthalenide because it can be removed by washing the reaction product with dilute acid. 9*‘43In the second step, potassium hydride is required to effect the Peterson reaction because the lithium alkoxide is unreactive due to its low ionic character.‘43 In eqn 167 tributylstannyllithium functions as the reductive lithiation reagent. I45 Reductive silylation of a

CX s

Me3SiCI LI

ihle3

HqCl2 / HqO_ MeOH / !420

&We3

Chemistry

(l62)‘4o

..?

_.. _

-Fnpl

+

b4

SiMbt-Bu L-

0

311

of mixed organosulfuwsilicon compounds

rs, ,Li USiM

(3

ss)

-P

N,

0

SiMe3

SiYs2i-Bu

70%

HgC12,Hg0 MeOH

Me3SiCLi

(SMe12

( l63)‘4’

OLi

0

CH3I

+

_

0

0

6

&

Me

yes5;;e3

-

Me SiMe,

+-.r

66%

71%

(l64)‘42

Ye3SiCI

73%

(l66)“4 Me3SICH2 SPh

I)n-BuLI;Ye3SICI

-

2) repeat

(Me3Si13 CLI

(Me3Si13 CSPh

LiNaph THF,-7BOC

)

52%

CH2=0

+

(Ye3Si)p

C=CH2

73% (167)“’ (Ye3W2CWidCH2Ph PhCHO _

+

Bu3SnLi

-tBoc

PhCH2 (Me3Si) 76%

C= CHPh

(Ye3SI)2

CLi CHePh

E. BLOCK and A.

312

ASUM

thioketal is illustrated in eqn 168’46 while radical-induced desulfurization cyclization and sila-Pummerer rearrangement are shown in eqn 16914’. PhCH2CH2CCi

(168)‘”

Me3SiCI

(SPh)2

Na,Me3SiCI

-

followed by radical

c

PhCH2CH+SPh)2

PhCH$H2C(

SiMe313

(169f4?

Etu3SnH AIBN 0

58%

$HO

I) [O];A 21 H+

*

N

Q?

0

(17O)l48

30%

3

Chloramine -T MeOH - H20

PhASiMe3 81%

0

I) LDA

EtLi -78DC_

SiMe3

2) PhS02SPh

OLi SiMe3

Ph

PhS

c-i:

PhS

62% -PhSLi -

1

PhCH2CH = C(OSIYe3)Et 70%

Several different methods of desulfurization are described in procedures developed by Reich (eqn 170’48). Thus, addition of alkyllithiums to silyl ketones (conveniently prepared by chloramineT hydrolysis of their 1,3-dithiane precursors) containing a phenylthio group leads to Brook rearrangement followed by elimination of thiophenoxide. Related procedures involving loss of PhSO- or PhSO; are also reported.‘48 Sulfur can be eliminated from a-silylsulfide 34 (eqn 171 I49

Me3SiCH (SPh)CH=CHOMe

I)fi-BuLi 2) C6H,36r

-

Me3Si~(SPh)CH=CHOMe

(171)14g

+ oPhS’ I’ Ys3Siff&CHOMe

*

CfjHt3 J4,60%

C6Hl3

I

sio2 hexane, A

C6HYYSPh

Me3Si

Me3Si3+-

OMe

92% n- BuLi; THPO (CH&Br I

C6H,3 y+ymHp

Me3Si

C6HI

OMe

0 H

75%

!=%

Mz+THp 3

0 55%

Chemistry

of mixed organosulfur-silicon

313

compounds

either B sihca~gel-promoted [ lJ]-sigmatropic thioallylic rearrangement foNowed by hydrolysis or a [2+3]-sigmatropic rearrangement of the corresponding s&oxide. The [1,3)-sigmatropic process requires brief heating,at cu 70°C while the [2,3]-sigmatropic reaction occurs at room temperature. Upon heating, sulGny1 compounds bearing a b-hydrogen e&nitrate sulfenic acids. This reaction has considerable utility in the synthesis of compounds containing W or CLX groups. In comi>ounds containing both a .siIylgroup and hydrogen atoms /I to the sulfoxide group three modes of elimination are possible: formation of an a,@msaturated silane by C-H cleavage a to silicon (eqn 172, path a), formation of a /.I,y-unsaturated silane by C-H cleavage y to silicon (eqn 172, path b), or elimination of silyl sulfenate by attack of sulfoxide oxygen at silicon (eqn 172, path c).

using

R 36a

36aR=H,bR=Me

R-H

b R=Ms c R=a-Pr d A = Me$i

37a

R=Me, b R=n-Pr

Fleming finds that cycloelimination in /I-silylethyl sulfoxides, e.g. 35 + 3&I (eqn 173 1500b; also see eqn 6563), occurs much more rapidly than in comparable systems in which silicon is replaced by hydrogen, e.g. %a + Ba, presumabIy because the conjugative electron withdrawing effect of silicon promotes cleavage of the /I-silyl C-H bonds. When an a-silyl CH bond is present cycloelimination is always observed to involve this bond rather than the C-Si bond. In the absence of an a-silyl CH bond cycloelimination involving silicon takes place, e.g. 37a + 38b, 3% + 38c. The rate of cycloelimination involving silicon, e.g., 37a + 38b, is ca three times the rate of cycloelimination involving a C-H bond in a comparable system, e.g. 36b + 3% Cycloelimination involving silicon has also been observed in /?-silylvinyl sulfoxides in which silicon and the‘sulfinyl group are syn (eqn 17415@“). A silyl group has been found to be superior to a phenyl group in controlling the direction of elimination (eqn 175 I’“). Other examples have appeared of synthetic procedures employing

0

,200C *

--II Me$i

-0 ‘S+- Ph

Me3Si Y-

Ph

(175)‘50c CC4- ref lux

-

PhCH=CHCH2SiL3 12%

+ PhCH$H=CHSi~ 88%

E. BLOCK and M.

314

ASLAM

pyrolysis of /.I-silykthyl sulfoxides (eqn 176). I5 ’ It has been already noted that siliconumtaining thiost&natesundergo elimination involving a-silyl C-H bonds rather than C-S bonds af&ding silylthiones (eqn 7236). &addition of the sulfenic acid followed by sila-Fummerer reamngement and fragmentation lead’to the (trimethylsilyl)dithioformate (eqn 17736). Examples have been published of the pyrolytic elimination of sulfur dioxide in the synthesis of silylketones feqn 1789” ; also see eqn 1029r, silylated 1,3-dienes’73 and l,ldimethyl4silacycloheptene (eqn 52”) as well as the elimination of the tmzenesulfinate anion or radical (eqn 17915’, 180’53, 181’54). (176)‘5’ Me3SiCH=

CHZ w

Me3SiCH2CH2SPh

Me3SiCH2CHLi cc14 ref Iux

-

II MCPBA _ 2, CH3L,

PhCHO

S(OlPh

S(O) Ph

_

Me3SiCH = CH CH(OH)

Me3SiCHzCH

CCH

(OH)Ph

Ph

79%

1l77)36 EIS/OX ) /aH (Me3Si)eC= S

-

c

16 Et&i Me$i-p

EtsGSiMes

3 SIMe3

Me3Si-F!

-

SH

AH

EtS* MeSSi - E

-

-H+ Me3Si:SEt S

AH

( 17B)g4o SiMe3

4oo”

c

+

Me

SO2 +

Me3SIC(0)Ye 30%

(1791’52 PhSGTJO

I)n-BuLi/HMPA

c

phs02)‘$0

2) Me3 SiCl

_ H+

PhS$,_++O

Ye3si

a

Me$l-0

Me3Si

CSHI?

I)Bu$nLi S%Ph

silica

gel ~

2) Me3SiCI

CaHl7JMe3

25’C 03%

c Bu3Sn

X

SiMe3 S02Ph

( lBO)‘53

Chemistry of mixed organosulfur-silicon

315

compounds

(IINP’ (PtlCO2)2

@YSotArCCI,,A

ArSr&

.‘-+02Ar

SiYeS

SiMeS

ArS02-SiMe3

-

3.8. Reactions involving sulfur-silicon stabilized carbocations Since both divalent sulfur and silicon stabilize a-carbocations it is not surprising that compounds containing both elements and a halogen atom attached to the same carbon atom are potent electrophiles. Such compounds can function as alkylating agents in Friedeldkafts reactions (eqn 182’55) or in reactions with silyl enol ethets (eqn 183’4”b*‘56’

Me3SiCH2

NCS Ccl4

SPh

*

Me$iCHCI

PhOMe, - 20°C TiCl4, CH2Cl2

SPh

( 182 vsa

_

100% Me0 a

CHtSPh) Si Ye,

Raney-Ni

L LO

*CH2SiMe3

90%

88% @OSi

Me$iCH2SPh

*

#3SiCHBrSPh

Me3

ZnBr2

I’Bb, (1831’56 c

32. I&k ad concerted additions or cycloreversions involving multiple bona3 with attached suljiir and silicon Addition of an electrophile to I-phenylthio-l+rimethylsilyl)ethene .could afiord intermediate 39 or 4, The former intermediate is generally favored due to the carbocation-stabilizing ability of an a-S atom (eqn l&tL5’). Intermediates related to 40 produced by electrophilic addition to allylic systems (eqn 185”‘) undergo facile desilylation. When the electrophile is an a,@msaturated acid

Me3Si Ph Y

EG PhS

PhS

Lte,Si

&

PrCOCl A,C, -7d

c

E = MeCO+ (MeCOCIIAICI3) 70%

40

Me;$g-(r

E

U841’57

Ph F

39

Me3Si

PhS

Me3Si

E

+

_

phsg-JI 75%

(185)‘“*

316

E. Buxx

and

M.

AstAM

chloride such as l-cyclopentenoyl chloride, synthetically useful cyclization processes occur with either I-phenylthio-l_ or (E j I -ph~~~~2~~e~y~yl~~~e (eqn 186’ ‘9. Magnus suggests that both reactions involve Nazarov mactions (pentadienyl cation cyclizations) followed by desilylation (eqn 187”q 188’s4. Me3Si AqBF4,

( 186f’59

ArS >=

( 1871’59

0+

&:A, 3

-

dh 3’

At

Nucleophiles, such as ~-bu~~~i~ or rne~ylIi~~, also add readily to 1-phenyIt~o-l-(TVmethylsilyl)ethene (eqn 189160).Michael-type addition to trisubstituted oieiins geminally substituted with sulfur and trimethylsilyl groups) (‘heteroconjugate additi~n”~~) occurs best when &fur is present as a phenylsulfonyl group. In such a system asymmetric induction in the addition of rne~yl~~~ can be achieved if a Ii~i~~heIator, such as an ether group; is present. Isobei6’ has elegantly used chelation-directed heteroconjugate addition together with desilylation and desulfonylation methods in the total synthesis of N-methylmaysenine (eqn 190, 191 “I). Related types of heteroconjugate additions involving sulfonyl-silyf allenes have been described (eqn 19216*). Phenyl2-(t~methylsilyl)e~ynyI sulfone serves as a vinyl cation equivalent under conditions of carbanion addition (eqn 193’63) as well as a dienophile or 1,3dipolarophile in cycloaddition reactions (eqn 9 157, 19416&, 195’646). In eqn 91 and 193 phenyl 2-(trimethylsilyl)ethynyl sulfone functions as an acetylene and (trimethylsilyl)ethyne equivalent, respectively. Both of these latter

( 189fW

Me3Si MeS

)c

t- BuLi -5m--

SMe

PhCHO, Ph&

Chemistry of mixed organosulfur-dicon compounds

CHO + (Me$i),CLiSPh

-

SiMe3

& Ef3N

E/Z

OHC -

95%

mixture >99%

Me3Sq

Ph

_

diastereaselective

Ph!X;@iTMs

R I3

0 C$Et +

I) Me3SiCN 2) AI-HP

Me,SiC=

-

cso2m KF AgF

~

N- methylmaysenine

317

318

E. BLMXand M.

M+SiC*

ASLAM

a

Na/Hq,MeOH . NaH2P04 . I I SiMe, 88%

C S02Ph

I

xa

Si Mea

93%

( 195fWb

Sib3 Me$iC=CS02Ar

+ Me2CN2

hv

-

SO2Ar

Me$i

OpAr

Me0

MO-

-N2

S02Ar Ar

Me$i PLS

PhS-

two alkynes are poor dienophiles. S-Si substituted allenes can be useo m [2+2] cycloaddition reactions as illustrated in the /I-la&am synthesis in eqn 1968.

(l96)*

>=

+,“(“:,

ClSO2NCO

c

TBAF HOAc-

3 87% SAr

Various cycloaddition and cycloreversion reactions have been reported for compounds of the type Si-C=+SO, in which n = 0, 1, 2. Thus, diphenyldiazomethane adds to silyl thioketones giving silylthiiranes (eqn 71 ‘j9),and benzonitrile N-oxide undergoes 1,3-dipolar addition to phenyl trimethylsilyl thioketone (eqn 19769*70 ). Examples of Diels-Alder reactions of silyl thioketones or silyl aldehydes have appeared above (eqn 72 36, 74”) as have examples of 1,3dipolar additions of silicon-substituted thiocarbonyl ylides (eqn 8785). We have encountered an example of a reaction involving a self 1,3-dipolar addition of (trimethylsilyl)methanethial S-oxide (eqn 19816’) giving 3,4-bis(trimethylsilyl)-1,Zdithietane l,l-diox-

(197tg7’0

Ys$i$Ph

+ PhCr&6

-

PhyNb S--f--~

S

SiMq

60% -

PhCN

+ (PhC(0)S)2

Chemistry

Me SIGH S(O)CI 3

2

hv

of mixed organosulfuv-silicon

s

Me 3 SiCH=

t-6

319

compounds ( 196140JS5

-

Me3S i

.

\9SiMe

+

Me3sia Si Me3

3

ide. The latter dompound, a color$ss crystalline solid, undergoes light-induced decomposition giving (E)-1,2-dis(trimeihylsilyl)etheni: along with minbr amounts of tr~-2,3-bis(trimethylsilyl)thiirane.40 Cycloadditions as well as ionic additions involving (trimethylsilyl)methanethial S,S-dioxide have also been reported (eqn 199 “j6). (l99P

Me3SiCH2S02CI

m

[ Me3SiCH = SO2 ]

L

Me3SiCH2S4NHPh

PhNH2

70%

A number of thermally-induced cycloreversion reactions involving mixed S-Si systems have been described such as loss of sulfur mono&de from a silyl thiirane S-oxide (eqn 149”‘) and loss of sulfur dioxide from a 1,3-oxathiolane l,l-dioxide’ (eqn 178’&). PyJolysis of 3,3-dimethyl-3-silathietane is reported to give the dimer of dimethylsilathione, presumably by the pathway shown in eqn 20016’. Heat and light-induced rearrangement of tris(trimethylsilyl)methanethia173b (eqn 201 Ias) has been reported. (2OOVj’ Me2S>

S

3

A

[ MopSi=

[Me2Si=S]

CH~ +

-

CH2 =s]

-

Me2SD

Me2Si -S I I S - SiMee (2011’6g

(Me3Si13

CH

I) MeLi 2) EtOCHS

(MeSSi13Ci=S

a

(Me3Si12 hv

16% -s Y

C=CHSSINe3

66% 33%

(Me3Sij2C=

CHSIMe3

3.10. Mixed organosulfw-silicon containing metal complexes In view of the importance of organoS comp&mds as ligands it is hardly surprising that the metal complexing ability of mixed S-Si compounds has been examined. Mixed S-Si carbene complexes of tungsten have been prepared (eqn 202’*7: Addition of c&bon monoxide to one such complex affords (ethylthio)(triphenylsilyl)ketene (eqn 202164. We have been interested in thiols of type 43 and 44 as examples of ligands with ‘tunable’ steric demand.lK3’ Variation in the ‘R’ groups, as well as the number of silyl groups in 43, should lead to

E. BLMX

320

and M.

ASLAM (202P9

+

-

co

Et2S2

EtSH

*

o”c

Ph3Si Ph3SiCH (SE!

>

(COl3W

I”< SIPhj

96%

At

(CO)3W-s

H20 c

t SE!

Et,N+Ct‘.zo

EtS

c=o

Ph3Si >

CH2C’2

) COOH

a corresponding variation in the steric cone angle of the thiol. The polysilylated thiols are also of interest due to the /?-effect of silicon which should increase the electron density at sulfur compared to simple alkanethiols. 37 ‘Tuning’ should also be possible here by changing the nature of the ‘R

( RR’R’SI 1” CH3_” SH

THF (Me3Si)2CHS

\

,a.

/L’\ ‘Li

THF ’

THF,

THF

,THF

,Li‘; (Me3Si13CS,L,,

SCH (SiMe312

SCWMe313

’ THF’

‘THF

’ (THF)

45

(Ms2PhSi13CS/AO?X(SiPhM&2)3

I 1 Ahs/AQ

(Ws,Si),CS, 4-S

C(SiPhMe2)3

.A9 C(Si Illed

41 [AgSCH(SIYe3)2]6

49

52 ylSiMe,h IYe3Si)jCS

’ ‘Pb’

Pb ‘SC(SiMa313

I i (SiMo312 53

Chemistryof mixed organosulfur-silicon

compounds

321

groups. We have prepared and characterized by X-ray crystallography the lithium thiolates 45 and 46 “O the silver thiolates 47-51’8~37 and the cadmiutn thiolate 52.” While lithium thiolate 45 has fok tetrahydrofuran ligands symmetrically placed abotii the two lithium ions, sterically more congested lithium thiolate 46 has one tetrahydrofuran ligand that is disordered in the solid state and loosely bound to lithium. “’ Depending on the bulk of the thiolate ligand the silver complexes exist in the solid phase as a trimer (47), tetramer (48), octamer or dimer of tetramers (4!), 51) or 53 has also been prepared apolymer (9). 37 The lead complex of tris(trimethylsilyl)methanethiol and characterized. 39 is a pleasure to acknowledge the important contributions of my coworkers whose published and unpublished work is cited in this review. We thank Professors B. Bonini. F. Hauser, G. Larson, G. Maccagnaoi, R. Okazpki, H.-H. Otto, E. Schaumann, D. Seebach and K. Stebu for unpublished results and helpful suggestions, Ellen Fontanelli and Marilyn Peacock for technical assistance in the preparation of the manuscript, and the donors of the Petroleum Research Fund, administered by the American Chemical Society, NATO, NSF, Soci& Nationale Elf Aquitaine, and the John Simon Guggenheim Memorial Foundation for generous support of our research described herein. Acknowlecigemenf-It

4. REFERENCES “General references on orgaoosulfur and/or organosiliwo chemistry : E. Block, Reactions of Organodfm Compounds, Academic Press, New York (1978); E. Colvio, Silicon in Organic Synthesis, Butterworth, London (1981); D. Neville Jones, Editor, Comprehensix Organic Chemistry, Vol. 3, Pergamon Ptess, Oxford (1979) ; ‘W. P. Weber, Silicon Reagents for Organic Syndt.e&, Springer,&w York (1$83) ; ‘T. H. &an and I. Fleming, .?yn&ti 761 (1979); 9. Apeloie and A. Smger, J. Am. C/tem. Sec. 107,2806 (1985) ; ‘B. M. Trost and D. P. Currao, Tetrahedron &II. 22,5023 (1981) ;‘D. J. Ager, Chem. Sot. Rev. 11,493 (1982) ; ‘G. A. Gomowia attd J. L. !3peier, Mech. of React. of Sulfa Cmpds. 3, 53 (1968) ; *S. Pawlenko in Methoden der OrganiwhenCkemie (Ho&n-Weyl), Vol. XIII, Geor& Thieme, Stuttgart, 1980, pp. 212-220; D. Bfandea in Orgmwmer. Chem. Rev., D. Seyferth, Ed., Vol. 7, Elsevier, 1979, pp. 257-397; S. Pawlenko, Organosilicon Chemistry, Walter deGruy&r, New York, 1986, pp. 65-72. %R. A. Beokeser and R. B. Currie, J. Am. Ckem. Sot. 70,178o (1948) ; ‘H. Sakurai, unpublished results. ’ H. Gilman, L. F. Casoo and H. G. Brooks, Jr., J. Am. Chem. Sot. 75,376O (1953). “‘D. J. Agcr and R. C. Cookson, Tetraheabn Lerf. 21, 1677 (1980) ; *D. J. Ager, J. Chm. Sot. Perkin Trans. I. 1131 (1983). ’ T. M. Dolak and T. A. Brysoo, Tetrahedron Len. 1%1 (1977). &D. J. Peterson, J. Org. Chem. 32,1717 (1967); *B. T. Grobel and D. Seebach, Chem. Ber. 110,852 (1977). ’ B. B. Harirchian and P. Magnus, 1. Chem. Sot., Chem. Comrmm. 522 (1977). ’ J. D. Buynak, M. N. Rao, R. Y. Chandrasekaran, E. Haley, P. D. Meester and S. C. Chu, Tefrahedron Lert. 26, 5001 (1985). ’ T. Cohen and R. B. Weisenfeld, J. Org. Chem. 44,360l

(1979). lo K -H. Geiss, D. Seebach and B. Setiog, Chem. Ber. 110,1853 (1977). ” E:J. Corey, D. Seebach and R. Freedman, J. Am. Chem. Sot. 89,434 (1967). l2 E. Vedejs and M. Mullins, Tetrahedron Left. 24,2017 (1975). ‘%H. Schmidbaur and W. Kapp, Chem. Ber. 105, 1203 (1972); bH. Schmidbaur and G. Kammel, Chem. Ber. 104, 3252 (1971). ” K. J. McCullough, Tetrahedron Lerr. 23,2223 (1982). ‘%. Schmidt and E. Weissflog, Chem. Ber. 109, 1239 (1976); bK. Oita and H. Gilman, J. Org. C/tern. 22,336 (1957) ; ‘T. D. Krizao and J. C. Martin, J. Am. Chem. Sot. 105,6155 (1983); d B. L. Soltz and J. Y. Corey, J. Organomet. Chem. 171,291 (1979); ‘C. Riicker, Chem. Ber. 120, 1629 (1987);‘T. Chou, H.-H. Tso, Y.-T. Tao and L. C. Lio, J. Org. Gem. 52, 244 (1987). I6 P. Beak and P. D. Becker, J. Org. Chem. 47, 3855 (1982); for another approach to an a-lithiomethaoethiol synthon see A. R. Katrizky, J. M. Aurrexcechea and L. M. V. deMigue1, J. Chem. Sot., Perkin Trans. I, 769 (1987). ” E. Block and M. Aslam, J. Am. Chem. Sot. 107,6729 (1985). I8 E. Block, V. E-swarakrishnan, M. Gemoo, H. Kang, C. Saha, K. Tang and J. Zubieta, submitted. ” J C Martin and G. D. Figuly, submitted ; G. D. Figuly. Ph.D. Thesis, University of Illinois-Urbana, 1981. lo d. 6 Cooper, J. Am. Chem. Sot. 76,3713 (1954). ” Q. W. Decker and H. W. Post, J. Org. Chem. 25,249 (1960). 2tiG. D. Cooper, J. Am. Chem. Sot. 76, 2499 (1954) ; bA. D. Petrov, V. F. Mirooov and N. A. Pogookina, Proc. Acad. Sci. USSR 100,81 (1955); ‘V. F. Mironov and N. A. Pogookioa, Bull, Acad. Sci. USSR, Div. Gem. Sci. 719 (1956). 23G. D. Cooper, J. Am. Chem. Sot. 76.2500 (1954). 24D C Noller and H. W. Post, J. Org. Chem. 17, 1393 (1952) ; A. 0. Mioklei, Q. W. Decker and H. W. Post, Red. nw. Chd.

Pays-Bas76,

187 (1957).

*’ N. E. Miller, Inorg. Chem. 4, 1458 (1965) ; J. C. McMullen and N. E. Miller, Inorg. Chem. 9,229l (1970). l&E. Vedeis and G . R . Martinez, J. Am. Chem. Sot. 101.6452 (19791: and W. Lawrvnowicz. . ,, bbut see D. P. Cox. J. Teminski . J. Org. ?hem. 49,3216 (1984j. 2”‘A. P. Davis, G. J. Hughes, P. R. Lowndes, C. M. Robbins, E. J. Thomas and G. H. Whitham, J. Chem. Sot., Perkin Trans. I 1934 (1981); ‘G. Barbieri, J. Organomer. Chem. 117, 157 (1976); 0. Barbieri, G. D. Andre&, G. Bocelti and P. Sgambotto, Ibid. 172, 285 (1979). 28M. G. Vorookov, S. V. Kirpichenko, E. N. Suslova and V. V. Keiko, J. Organomet. Chem. ZU4,13 (1981). 29M. G. Voronkov, S. V. Kirpichenko, E. N. Suslova, V. V. Keiko and A. 1. Albanov, J. Organomer. Gem. 243, 271 (1983). ” R. J. F-den and M. D. Coon, J. Org. Chem. 29,1607,2499 (1964). ” F Cooke and P. Magnus, J. Chem. Sot., Chem. Commun. 513 (1977) ; alsoseeT. J. Barton and S. K. Hoekman, J. Am. Chem. Sot. 102, 1584 (1980).

322

E. BLOCKand M. A~LAM

” E. Block and A. Wall, I-..rruhe~o~ Lelt. 26, 1425 (1985). ” E. Block and M. Aslam, Tetrahedron Lart. 23,4203 (1982). ” E. Block and A. A. Bazzi, Tetrahedron Wt. 23,4569 (1982). a’ A. Wd, Ph.D. Thesis, SUNY-Albany, 1985. ” E. Block and M. Ashnn. Tetrahe&on kett. 26.2259 (1985). ” K. Tan8 M. A&m, E. Block, T. Nicholson and J. iubieta, Itwrg. Chem. 26.1488 (1987). ‘&“A.Ricci, A. Degl’lnnccenti, M. Fiorenza, P. Dembech, N. Ramadan, G. Seconi and D. R. M. Walton, TetrabeaYm Let,. 26,109l (1985) ; ‘K. Steliou, personal communication. 39P. B. Hit&cock, H. A. Jasim, R. E. Kelly and.M. F. Lappert, J: Chem. Sot., Chem. Commun. 1776 (1985). ” E. Block and M. A.&m, unpublished results. ” A. G. Brook and D. G. Anderson, Can. 1. Chem. 46,2115 (1968). ‘I S. M. Weinreb, D. M. Demko and T. A. Lessen, Tetrahedron L.&t. 27,2099 (1986). ‘by. I. Bankov, A, G. Shipov, L. V. Gorshkova, I. A. Savastoyanova and A: V. Kisin, Z. Obshch. K&m. 47,1677 (1977) ; bE. Wenschuh, W. Radeck, A. Porzel, A. Kolbe and S. Edehnann, Z. Anorg. A&. Chem. 528, 138 (1985). ” B. Zwanenbrug, Rec. Trot. Chim. Pays-BUY 101, 1 (1982) and references therein. ” G. D. Cooper, J. Org. Chetn. 21, 1214 (1956). ‘&A Wright, D. Long, P. Boudjouk and R. West, J. Am. Chem. Sot. 94,4784 (1972); bA. Wri&t and R. West, J. Am. &em. Sot. 96.3222 (1974). ” E. Block and S. Ahmad, unpublished results. ‘r C. Rucker. Tetrahedron Let,. 25.4349 (1984). 49G. A. Gornowin, J. W. Ryan and J. L: Speikr, J. Org. Cherh. 33,2918 (1968). ” P. V. Bonsignore, C. S. Marvel and S. Banetjee, J. Org. Chem. 25,237 (1960). ” W. Stannn, J. Org. Chem. 28.3264 (1963). ” K. E. Ktig, R. A. Felix and W. P. W&r, J. Org. Chem. 39,1539 (1974). ” N. S. Fedotov, I. G. Rybalka, V. A. Korolev and V. F. Mimnov, Z. Obshch. k7&. 48,612 (1978). ‘&M. G. Voronkov, Y. I. Rakhhn, R. G. Mirskov, S. Kh. Khangpzheev, 0. 0. Yarosh and E. 0. Tsethna, Z. Obdch. Khim. 49, 119 (1979); ‘M. G. Voronkov, R. G. Mirskov, G. V. Kuznetsova, N. K. Yarosh, 0. G. Yaroah, 0. S. Stankevich, A. I. Albanov and V. Yu. Vitkovskii, Z. Obshch. Khim. 52, 1820 (1982). ” M. G. Voronkov, R G. Minkov and V. I. Rakhhn, fzu. Akad. Nuuk SSSR Ser. Khim. 610 (1975). s6 J. P. Pillot, J. Dunogues and R. Calas, Synthesis469 (1977). ” R. V. C. Carr, R. V. Williams and L. A, Paquette, J. Org. Chem. 48,4976 (1983). ‘* A. D. Berry and W. B. Fox, J. Fluorine Chem. 6, 175 (1975). ‘9 E. Block, M. Aslam, V. Eswarakrishnan, K. Gebreyes, J. Hutchinson, R Iyer, J.-A. LatBtte and A. Wall, J. Am. Chem. tic. lO& 4568 (1986). 6oE. Block, M. Aslam, V. Eswarakrishnan and J. Luo, unpublished results. ” G. R. Glowacki and H. W. Post, J. Org. Chem. 27,634 (1962). 61F. Cooke, R. Moetck, J. Schwindeman and P. Magnus, J. Org. Chem. 45, 1046 (1980). 63I. Fleming, Chem. Sot. Beu. lo,83 (1981). 64M. Grignon-Dubois, J.-P. Piliot, J. Donogues. N. Dulfaut and R. Calas, J. Orgunomet. Chem. 124,135 (1977). 65P. Bourgeois and R. Calas, J. Orgunomet. Chem. 84, 165 (1975). 66I Cutting and P. J. Parsons, Tetrahedron L&t. 22.2021 (1981). 24,4463 (1983). ” d. N. Hsiao and H. Shechter, Tetruhedron Let,. 25.1219 (1984). ‘&E. A. Chernyshev, 0. V. Kuzmin, A. V. Lebedev, A. I. Gusev, N. I. Kirillova, N. S. Nametkin. V. D. Tyurin, A. M. Krapivin and N. A. Kubasova, J. Orgunomet. Chem. 252, 133 (1983) ; I!. A. Chernyshev, 0. V. Kuzmin, A. V. Lebedev, A. I. Gusev, M. G. Los, N. V. Alekseev, N. S. Nametkin, V. D. Tyurin, A. M. Krapivin, N. A. Kubasova and V. G. Zaiin, Ibid U2, 143 (1983) ; ‘K. H. Panneli and J. R. Rice, J. Orgunomet. Chem. 78, C35 (1974) ; K. H. Pannell, Transition Met. Chem. 1, 36 (1975). 69 B F Bonini, G. Mazzanti, S. Sarti and P. Zanirato, J. Chem. Sot., Chem. Commun. 822 (1981); B. F. Bonini, G. Ma&&, P. Zani, G. Maccagnani, G. Barbara, A. Battaglia and P. Giorgianni, J. Chem. Sot., Chem. Commun. 964 ‘Og98gbaro A Battaglia, P Giogianni, G. Maccagnani, D. Macciantelh, B. F. Bonini, G. Mazzanti and P. Zani, J. &em. Soc.,‘Peikin Trans. Ii81 (1986). 7’ E Vedejs T H. Eberlein, D. J. Mazur, C. K. McClure, D. A. Perry, R. Ruggeri, E. Schwartz, J. S. Stubs, D. L. Varie, R. G. Wiide’and S. Wittenberger, J. Org. Chem. 51, 1556 (1986). ‘?I J Harris and D. R. M. Walton, J. Chem. Sot., Chem. Commun. 1008 (1976) ; bS. J. Harrris and D. R. M. Walton, J. &giomet. Chem. 127, Cl (1977); CR. G. Mirskov, S. P. Sitnikova and M. G. Voronkov, Z. Obshch. Khim. 48,2137 7’$.9%umann and E.-F. Grabley, Chem. Ber. 113, 3024 (1980); bR. Okazaki, A. I&ii and N. Inarnoto, J. Am. Chem. Sot. 109,279 (1987). ” M G Voronkov, T. J. Barton, S. V. Kirpichenko, V. V. Keiko and V. A. Pestunovich, Izv. Akad. Nauk SSSR, Ser. Khim.‘611 (1976). ” R. Appel and R. Moors, Angew. Chem., Ind Edn. Engl. 25,567 (1986). 76P. D. George, J., Org. Chem. 26,4235 (1961). ” M. Kira, H. Nakazawa and H. Sakurai, Chem. Lctr. 497 (1986). ‘&M A Bruntfield, S. L, Quillen, U. C. Yoon and P. S. Mariano, J. Am. Chem. Sot. 186, 6855 (1984); bJ. Yoshida and S. ‘Hoe, Chem. L.etr. 631 (1987) ; unpublished results personally connnuni~ated; ‘T. Koizumi. T. Fuchigami and T. Nonaka, Chem. Let,. 1095 (1987) ; unpublished results personally communicated. ‘“E. Block, A. J. Yencha, M. Aslam, V. Eswarakrishnan, J. Luo and A. Sano, submitted; bbut note that the sila-Pummerer reaction of I-phenylsuhinyl-I-(trimethylsilyl)cyclopropane is known. I”’ *OT Veszpremi, Y. Ha&a, K. Obno and H. Mutoh, J. Orgunomet. Chem. 252, 121 (1983): H. Bock and B. Roth, Phosphorus Surfur 14,21 I (1983). 81A ~icci D. Pietropaolo, G. Distefano, D. Macciantelti and F. P. Colonna, J. Chem. Sot., Perkin Truns. II 689 (1977). “i. P. J&ie, Orgunomef. Chem. Rev. A 153 (1970). a3 A. Padwa and J. R. Gasdaska, J. Org. Chem. 51.2857 (1986).

324

E. BLOCK and M. ASLAM

“’ T. Mandai, M. Yamaguchi, Y. Nakayama, J. Otera and M. Kawada, Tetrahe&on L&r. 26,2675 (1985). ‘3J M. Isobe, Y. Ichikawa and T. Goto, Tetrahedrar ht. Z&4287 (1981). ‘j6 R. D. Miller and D. R. McKean, Tetrahedron Len. 24, 2619 (1983); S. Lane, S. J. Quick and,R. J. K. Taylor, Ibfd. 25, 1039 (1984); R. D. Miller and R. Hassin, Ibid. U, 5351 (1984). “‘M. Aono, C. Hyodo, Y. Terao and K. Achiwa, Tetruhedron L&t. 27,4039 (1986). 13*E. Block and D. M. Borek, unpublished results. 13’E. J. Corey, a Seebach and R. Freedman, J. Am. Chem. Sac. 89,434 (1%7); A. G. Brook, J. M. DufI’, P. F. Jones and N. R. Davis, Ibid. 89,431 (1967). “OT. N. Salzmann, R. W. Ratcliffe, B. G. Christensen and F. A. Bouffard, 1. Am. Chem. Sot. I@&6161 (1980). ““D. Secbach and R. Burstinghaus, Angew. Chem., ht. Ed. Engl. 14,57 (1975) ; “R. Burstinghaus and D. Seebach, Chem. Bfr. 110,841 (1977). “‘M. J. Reuter and R. Damrauer, J. Orgunomer. Gem. 82,201 (1974). “3rT. Cohen and J. R. Matz, Synthetic Commun. IO.31 I (1980) ; *T. Cohen, J. P. Sherbine, J. R Matz, R. R. Hutchins, B. M. McHenry and P. R. Wiley, J. Am. Chem. Sue. 106.3245 (1984); rM. Bhupathy and T. Cohen, Tetrahedrun L&r. 28, 4793 (1987). ““D. J. Ager, J. Org. chum. 49, 168 (1984); *D. J. Ager, Tetrahedron I&. 22,2923 (1981). “‘T. Takeda, K. Ando, A. Mamada and T. Fujiwara, Chem. ht. 1149 (1985). “q. Kuwajima, T. Abe and K. Ataumi, Chem. Letr. 383 (1978); *K. Atsumi and I. Kuwajima, Ibid. 387 (1978). “’ D. J. Hart and Y. M. Tsai, J. Am. Chem. Sot. 106.8209 (1984). “OH. J. Reich, J. J. Rusek, R. Olsoro, J. Am. Chem. Sot. 101,2225 (1979) ; I-i. 1. Reich, R. C. Holtan and S. L. Borkowsky, J. Org. Chem. 52, 312 (1987). 149J. Man&i, H. Arase, J. Otera and M. Kawada, Tetruhedron L&t. 26.2677 (1985). ‘V. Fleming, J. Goldhill and D. A. Perry, J. Gem. Sot., Perkin Truns. I. 1563 (1982); ‘1. Fleming and D. A. Perry, Terruhedron37,4027 (1981); ‘M. Ckhiai, S. J. Tada, K. Sumi and E. Fujita, J. Chem. Sot., Gem. Commun. 281(1982). “I C. N. Hsiao and H. Shechter, Ten&&on L&t. 24,237l (1983). Is2J. Otera, T. Mandai, M. Shiba, T. Saito, K. Shimohata, K. Takemori and Y. Kawasaki, Orgunomer. 2,332 f1983). 15’M. Ochiai, T. Ukita and E. Fujita, Chem. Lerr. 1957 (1983). “‘P. Lin and G. H. Whitham, J. Chem. Sot., Chem. Commua. 1102 (1983). “‘H Ishibashi, H. Nakatani, Y. Umei and M. Ikeda. Telrahedron L&t. 26.4373 (1985) ; H. Ishibashi, H. Nakatani, Y. LJmei, W. Yamamoto and M. Ikeda, J. Gem. Sot., Perkin Truns. I, 589 (1987); H. Ishibashi, H. Nakatani, H. Sakashita and M. Ikeda, J. Chem. Sot., Chem. Co-. 338 (1978). 15&D.J. Aver. Tetrahedron ht. 24.419 (1983): *I. Flemine and S. K. Patel. Tetrahe&on Len. 22.2321 11981). . , I” D. J. A&r: Tehzhedron Lea. 23; 1945‘(198ij. I’* K. Hiroi and L.-M. Chen, J. Chem. Sot., Chem. Comma 377 (1981). ls9P. Magnus and D. Q-to, J. Org. Chem. SO, 1621 (1985). ‘6(bD Seebach, R. Burstinghaus, B.-T. Grobel and M. Kolb, &e&s Ann. Gem. 830 (1977) ; *D. J. Ager, Telruhedron Lett. 22; 587 (1981). 16”M. Kitamura, M. Isobe, Y. Ichikawa and T. Goto. J. Org. Chem. 49, 3517 (1984); “M. Isobc, M. Kitamura and T. Goto, Terruhedron L&t. 3465 (1979) ; ‘M. Isobe, Y. Ichikawa, D.-I. Bai and T. Goto, Tehzhedron Len. 26,5203 (1985) ; %I. Isobe, Y. Ichikawa, H. Masaki and T. Goto, Tetrahedron Lert. 25,607 (1984). 16’M. Ohmori, Y. Takano, S. Yamada and H. Takayama, Te&tedron Lerr. 27,71 (1986). 16’T. Ohnuma, N. Hata, H. Fujiwara and Y. Ban, J. Org. Chem. 47,4713 (1982). 16&A P. Davis and G. H. Whitham, J. Chem. Sot., Chem. Commwt. 639 (1980); *A. Padwa and M. W. Wannamaker, Tt&hedron Lert. 27.2555(1986); A. Padwa, M. W. Wannamaker and A. D. Dyszkwski, J. Org. Chem. 52.4760 (1987). “‘E. Block and A. A. Bazzi, unpublished results; A. A. Bazzi, Ph.D. Thesis, University of Missouri-St. Louis, 1981. 16&A G. Shipov, A. V. Kisin and Y. I. Baukov, J. Org. Gem. U.S.S.R. 1022 (1979) ; *A. G. Shipov and Y. I. Ihkov, J. Oig. Gem. U.S.S.R. 1112 (1979). 16’OL.E. Gusel’nikov, V. M. Sokolova, E. A. Volnina, V. G. Zaikin and N. S. Nametkin, J. Organomet. Chem. 214, 145 (1981); *L. E. Gusel’nikov, V. V. Volkova, V. 0. Z&in, M. G. Voronkov, S. V. Kirpichenko, V. V. Keiko, N. A. Tarasenko, A. A. Tishenkov,N. S. Name&in, M. G. Vontkov and S. V. Kirpichenko, J. Organomet. Chem. 215,9 (1981). also see N. A. Tarasenko, V. V. Volkova, V. G. Zaikin, A. J. Mikaya, A. A. Tisehnkov, V. G. Avakyan, L. E. Gusel’nikov. M. G. Voronkov, S. V. Kirpichenko and E. N. Suslova, J. Organomet. Chem. 288.27 (1985) ; and E. A. Cherynyshev, 0. V. Kuz’min, A. V. Lebedev, V. G. Zaikin and A. I. Mikaya, J. Orgutwmet. Chem. 289,231 (1985). “‘R. Okazaki, A. Ishii and N. Inamoto, J. Am. Gem. Sot. 109,279 (1987). ‘69H. Homig, E. WaJther and U. Shubert. Orgarwme~aflics 4, 1905 (1985); J. Kron, H. Hornig and V. Schubert, Chem. Ber. 119,290O (1986). “‘M Aslam, R. A. Bartlett, E. Block, M. M. Olmstead, P. P. Power and G. E. Sigel, J. Chem. Sot., Chem. Comma 1674 (1985). “’ R. L. Merker and M. J. Scott, J. Organomel. Chem. 4,98 (1965).