The chemistry of trimethylsilylcarbene

TetrahedronLetters IVo.23, pp 2061 - 2064,1975.Pergmon R-ems. Printed in Great Britain.

THE CHEWSTSY OF TRIMETHYISILYICAREXE R. Lowell Kreeger and Harold Shechter Departmentof Chemistry,The Chio State University,Columbus,chio 432lO (Reoeivedin USA 30 April1975jreoefved in UK for publioation 6 WY 1975) Trimethylsilylcarbene (&), generatedby alpha-elimination of chloromethyltrimethylsilsne by alkali metals at room temperature,is reported'to insert to l,l-dimsthyl-l-silacyclopropane (c)2 which is then cleavedby the organo-metallic intermediates. l,l-Dichloromethyltrimethylsilaneand sodium-potassium vapor at 2600,= apparently* silane (z), presumablyby rearrangementof &

C% cI&-F--H

CH3 -

gives vinyldirnethyl-

We now summarizethe propertiesof &as derived

C&l

CH2

‘s/l

I -

C!H/

5

'CH 2

;r

'I&-Si-CH=CH2 I H

2.

from trimethylsilyldiazonkhane (k)' by thermolysisin the gas phase and by photolysisin 5 solutia. The results are significantin that they reveal the marked ability of &to undergo methyl migrationto 2-methyl-2-sila-2-butene (u and productsthereof. Decompositionof ftat 440' and 10 nunHg pressurein a Pyrex flow system and collection of the effluent'at -78' yield8 $

(j-4$),vinyltrimethylsilane "e (5 u 3-4%),cis- and

a-1,1,2,3,3,4-hexamethyl-1,J-disilacyclobutanes(3 > 2@ and 5

> l8$), 3,3,4,ketra-

methyl-3,4-disila-l-hexene (91 4%) and involatileproducts. Silacyclopropane cwas not detected. Disilacyclobutanes Lend 5 assigned from their analyses,masses, ir absorptions, e and nuclear magnetic resonances, are apparentlyderivedby dimerizationof 3_in the 10

reactor.

Silabutenezis trappablein the flow systemwith reactantsother than itself in

that (1) ftand 2-propsnolat 440' yields ethyldimethyl-2-propoxysilane (3 (2) kand bensaldehydeat 423O gives cis- and e-l-phenyl-1-propenes

> 6%)"'

(l& 9

and

and 3

12$).r" Disilahexene2 is presumablyformed by addition of 3_to j_and its structurewas establishedupon its synthesisby cross-couplingethyldimethylchlorosilane and vinyldimethyl2061

2062

Ito.25

chlorosilanewiti lithium at 25’ in hexanethylphosphoramlmide.

C&-Si-CH=C&

c&l C% I

I

Cy,-CH_z,-Si-Si-CCH=CQ

cA. ,c=c, /CG

C&i-CH2-CI&

H

CA\ c=c \HH H'

H

Clis

b-Cm&

Major cmcerns of Ws to >

investlgatlonare the mchatdma

of transformationof L to zand

Carbene &might rearrangedirectly to 2 or/and insert to form gwhich then undergoes 11

ring

opening

and hydrogen

of gas derived from $

VinylslIme J-may be producedby isomrizatlon

migrationto z

or by rearrangementof 2

Wthyl migration In conversionof Lt.0 2

is revealedby thermolysiaof cu-deuteriotrimethylsilyldiazomethane (a)= ~-1,3-dideuterio-1,2,2,3,4,4-h~~l-l,3-~~l~~lo~t~e~e

&and

at 4&O to cis- and IJJ > 44).

!Che

stereochemistryand the locationof deuteriumin &and lJare derived from their nuclear 13 &6_and JJdo not conmsgnetlc resonances. The fact that the dideuteriodisilacyclobutanes 11

tain deuteriumIn their methyl groups indicatesthat &undergoes methyl migration to lJ_ which dlmerizeeto $_and xaud

excludes isomrization of &to gas a path to &

Ihe deuteriovinyldimetbylsilane and the deutariotinyitrimethylsilene formed fromQat 4Z" are in ineufflcientquantityto determinethe positionsof their deuterium. There is producedhowever 3,3,4,4-tetramethyl-3,4-disila-l-hexene (ra) which from

it8 mm,

cOntain8

a,14

deuteriumonly at the 2- and

5-pO8itiw.

Cm the baa18

thatgiie

formed from~and

No. 25

2063

C&i C&3 I

-\

'Z-Is-Si-'d-D D

D .si=cII

QJ3’

I

CHs

D Ch

CS

+

‘cH3

‘C%

CR3 14 -

Ch I CHs-Si-CD-N2

Cfb I CHa-Si-CD=CHa

I C%

3

I H

it appears that aisomerises to g

D CH3 CH3 z

t CHs-~-L-$i-~~=~~a II I H CHs CDs

(thus 2-2)

end ldoes not arise from rearrange-

ment of 2. Investigationof the details of formationof Iis in progress. Fhotolysisof kat 25' in various alcoholsand in diethylaminewas then studied. Cationic cleavage of kin the dark by methanol occurs fairly rapidly to form trimethylmethoxy. silane (- lOO$)7 and methyl ether (-101Z$).~ The cationic path for decompositionof &is indicatedfurtherby reactionwith 2-propanolupon additionof hydrochloricacid to give tri7

methylisopropoxysilane,hexamethyldisiloxsne,7 and methyl isopropylether7 in > 9C$ yield. Alteratim of $_does not occur in diethylamine,J-ethyl-5-pentanol, S-methyl-2-propanol, or even 2-propanolfor more than l2 hours and these systems photolyze(450 watt high pressure Hg arc) in < 2-3 hours to ethyldimethyl-N,N-diethylaminosilane (g),' ethyldimethyl(Jethyl-j-pentoxy)silane (&),7 ethyldimethyl-2-propoxysilane (2&), and gin

> 55, 69, 47,

6

and 6@ yields, respectively. Irradiationof &in J-ethyl-j-pentanol-OD, 2-methyl-& 6,15 propsnol-OD,and 2-propanol-OD,respectively,yields L& & and 2J. Formationof these e,1e productsand in particularphotolysisof 32-n 2-propanol-OD to give cy,cu-dideuterioethyldimethyl-2-propmsilane(6) in which the methyl portion of its ethyl group does not contain deuteriumprovide further evidence that Lundergoes methyl migrationto 2

17,19

Ha. 25

CIis

C&l

cH+c*-CHS

cI&-cH&!& I

z

CHe-Si-CDs-CHs

I OCH(CHs)2

OR

a

Further

StUdy

Of

1,

88

deriV&

by alpha-ellndIlat.ioll ~thod8,

i8

in

prO@e88.

REFERENCES

1. J. W. Connolly and G. Urry, J. Amer. Chem. Sot., 86_,619 (1964). 2. Silacyclopropanes have been reportedby R. L. Iambert,Jr., and D. Seyferth,ibid., sft, 9246 (1972),Y. Nakadaira,S. Eanouchi,and H. Sakurai,ibid., s 5623 (1974zd M. Ishikawaand M. Eumada, J. Organcmstal.Chem., 8& C3(1974). 1442 (1964). 3. P. S. Skell and E. J. GOld8tej.qJ. Amer. Chem. Sot., s 4. D. Seyferth,H. Msnsel,A. W. Dow, and T. C. Flood, J. Crganometal.Chem., 44 279 (1972), 5. R. 19.Haszledine,D. L. Scott, and A. E. Tipping,J. Chem. Sot. Perkin I, l&I (1974) report that L inserts into trimethylsilane without rearrangement. 6. All volatile productswere separatedon SE-30 or ~~-60 glc columns and have proper analyses and/or exact ma88e8. Identifiedby comparisonwith authenticstandards. 87: The origin of 6 (possiblyfrom 2 and ft>is not clear. and C-H) and 1.00 (d, 6H, C-CH& 9. Nmr (cDC18): 3 6 O.m, 0.24, 0.37 (s+s+m,14H, Si-Cl@., s 6 0.18 (s, 12, si-r&), 0.45 (m, C-H, 2~), and 1.10 (a, 6~, c-c~). 10. For related reaction8of sila-alkenes,8ee P. Boudjoukand L. H. Sommer, Chem. Commuu., 54 (1973),L. H. Soxaaerand D. N. Roark, m, 167 (1973)and referencestherein. ll. It is uulikely that 5_is formed from & in the gas phase by protonation,rearrangement, and deprotonation. I.2 Preparedfrczn5 by additionof methyllithiumat -15' and then D80. 13: Nmr (CD&): 5 b 0.17 and 0.20 (a+~, l2H) and 1.08 (m, 6H); x, b 0.20 (8, I.& and 1.08 (m, 6~). b 0.07 and 0.17 (8+8, l2H), 0.67 (m, X-I),1.00 (m, JH), 5.65 (m, lH), 14.

15. lhe nmr of a

& 8nd 25 reveal that deuteriumi8 exclusivelyin the o-pOsitiOn8Of their ethyl groups. (96$ o-D) and 2-propanol-OD(8@ D) gives, based on nun, 6 (67-752) 16. ehatior of !&is analogousto photolysisof ethyl trimethyl8ilyldiaZOaCetate in alcohol8 to give ethyl 2-(alkqydimethylsilyl)propionates; W. Ando, T. Hagiwara,and T. Migita, J. Aamr. Chem. Sot., 7518 (1973). 18. Cationicconversirmof 111 to 21- by photolysisof 5_in alcoholscannot as yet be excluded8s a mechan&tic G&il.ity. It is noted, however,that t_butylcarbene, presumablygeneratedin thermolysisof 1-diazo-2,2-dimetbylpropane, is not protonatedby hindered alcohols;J. H. Bayless, L. Friedman,F. B. Cook, and H. Shechter, 531 (1968). 19. T. J. Barton, J. A. Kilgour,R. R. Gallucci,A. J. Rothschild,J. SlUtsky,A. D. Wolf, doe8 and M. Jones, Jr., ibid., $I’J_,657 (1975) report that the phenyltrlmethylsilylcarbene not undergo insertion l,l-dimethyl-2-phenyl-l-silacyclopropane.

17.

ACENOWIEDGMENT: The support of the NationalScience Foundationis gratefullyacknowledged.