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Synthesis and Reactivity inInorganic and Metal-OrganicChemistryPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/lsrt19

Direct Metalation of α-Trimethylsilylallyl ChlorideAlkylation SilylationRaúl Ariz a , Elena Araya a , Alfonso Oliva a & AuroraMolinari aa Institute of Chemistry , Catholic University ofValparaíso , Casilla 4059, Valparaíso, ChilePublished online: 22 Aug 2006.

To cite this article: Raúl Ariz , Elena Araya , Alfonso Oliva & Aurora Molinari (1994)Direct Metalation of α-Trimethylsilylallyl Chloride Alkylation Silylation, Synthesisand Reactivity in Inorganic and Metal-Organic Chemistry, 24:7, 1227-1234, DOI:10.1080/00945719408001396

To link to this article: http://dx.doi.org/10.1080/00945719408001396

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SYNTH. REACT. INORG. MET.-ORG. CHEM., 24(7), 1227-1234 (1994)

DIRECT METALATION OF a-TRIMETHYLSILYLALLYL

CHLORIDE. ALKYLATION AND SILYLATION

Radl Ariz, Elena Araya, Alfonso Oliva

and Aurora Molinari'

Institute of Chemistry,

Catholic University of Valparaiso

Casilla 4059, Valparaiso, Chile

ABSTRACT

a-Trimethylsilylallyl chloride (1) was directly

deprotonated with lithium diisopropylamide (LDA) at -78OC

in the presence of alkyl halides (Barbier technique), to

afford a mixture of a-alkyl-a-trimethylsilylallyl

chloride andy-alkyl-a-trimethylsilylallylchloride. With

trialkylchlorosilanes, only y-trialkylsilyl-a-trimethyl-

silylallyl chloride was formed.

INTRODUCTION

Carbanions derived from ally1 chloride and related

compounds are ambident nucleophiles which can form a new

carbon bond either at the a or y position. The

1227

Copyright 0 1994 by Marcel Dekker, Inc.

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1228 ARIZ ET AL.

regioselectivity of these reactions is governed by steric

and electronic effects.’** The a-chloroallyl anion has

been generated from a-trimethylsilylallyl chloride (1) with silica gel supported tetrabutylammonium fluoride,’

by n-butyllithium deprotonation of 3-chloroallyl-

tributyltin at - 7 E 0 C I 4 by direct deprotonation of ally1

chloride with LDA at -78OC under Barbier technique

(deprotonation in the presence of the electrophile), or

at -9OOC under Grignard conditions (deprotonation

followed by addition of the electrophile).’ Further

condensation of the anion with various electrophiles

affords the a, y or a mixture of both isomers.

On the other hand, a-trimethylsilylchloroallyl anion

(2) is obtained by a transmetalation reaction of 3-

chloro-3-trimethylsilylallyltriphenyllead with n-butyl-

lithium at -9OOC. The reactions of this anion with

methyl iodide and carbonyl compounds also produce a

mixture of both isomers [eq (l)]. Again, withtrimethyl-

chlorosilane only the y isomer is isolated.6

SiMe3 I . n -BuLi , THF, - 9 o O c

2. E+, -9OOC Ph3Pb c1

SiMe3 SiMe3

C1 E E c1

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CY-TRIMETHYLSILYLALLYL CHLORIDE 1229

The mild conditions of the Barbier technique applied

in the metalation of ally1 chloride‘ prompted us to

investigate the application of this procedure in the

direct generation of (2) from a-trimethylsilylallyl- chloride (L) at -78OC, instead of 3-chloro-3-trimethyl-

silylallyltriphenyl lead at -9OOC. In this communication

we report the results of the direct metalation of (1) with LDA at -78OC, and the reactivity of the formed

lithium derivative with alkyl halides andtrialkylchloro-

silanes.

RESULTS AND DISCUSSION

a-Trimethylsilylallyl chloride (1) reacts wi h LD at -78OC in the presence of an alkyl halide or a tri-

alkylchlorosilane to generate quantitatively a species

whose reactions indicate it to be a-trimethylsilyl-

chloroallyl lithium (2). This lithium derivative (2) is trapped “in situ” by trialkylchlorosilanes in a regio-

specific way to produce only y-trialkylsilyl-a-tri-

methylsilylallyl chloride (y-isomer). These results can

be rationalized in terms of steric effects.

With alkyl halides, a-alkyl-a-trimethylsilylallyl

chloride (a-isomer) and y-alkyl-a-trimethylsilylallyl

chloride (y-isomer) are formed. Both steric and

electronic effects must be taken in account to explain6

these results. (Table 1).

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Tabl

e 1.

Alk

ylat

ion

and

Sily

latio

n of

a-T

rim

ethy

lsily

laU

yl C

hlor

ide (

1).

7

- S

!e3

4 e

Si

W3

+

SiW

3

E C1

E

CI

SiW

3 LD

A/T

HF

- 78%

c1

Cl

hle3

SiC

I

t-BuM

e2Si

CI

i-PrB

r C

A2=

CE

-C(i-

Pr)(

CI)

Si.n

c3

i-PrC

E2C

E-C

(CI)

SiM

e3

(Z)

(37)

(6

3).

3.

N

w

0 E N

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a-TRIMETHYLSILYLALLYL CHLORIDE 1231

Based on the weight and lH NMR analysis of the

final crude product, the combined yield of the overall

reaction is almost 100%. With alkylhalides two products

were detected by glc analysis, identified as the a and y

isomers by carefully ‘H NMR spectral data and the ratio

of both isomers was calculated by integration of the

trimethylsilyl signals.

When only the y-isomer is formed, the vinyl proton

displays a triplet in the 5.90 ppm region. When both

isomers are present , this signal is observed at 5.83-5.89 ppm, together with a multiplet of the vinyl group from

the a-isomer at 4.83-6.06 ppm (Table 1). The y-isomer can

exist in a Z or E configuration. Calculations indicate

a value of 5.94 ppm for the Z isomer and 6.23 ppm for the

E isomer.6 In all the y isomers formed, the vinyl

resonance is observed at 5.83-5.90 ppm, in agreement with

the Z configuration.

In conclusion, the results observed show that the

a-trimethylsilylchloroallyl lithium (2) can be generated by direct deprotonation of a-trimethylsilylally1chloride

(1) and condensed with alkyl halides or trialkylchloro-

silanes. This study represents a contribution to the

knowledge of stabilized carbanions by both chlorine and

trimethylsilyl groups, which have been proved to be

useful intermediates in organic synthesis.’-’

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1232 ARIZ ET AL.

EXPERIMENTAL

All reactions were carried out in a flame-dried

system under a nitrogen atmosphere. The standard

apparatus consisted of a three-neckedI round-bottomed

flask equipped with magnetic spin bar, condenser,

dropping funnel and septum inlet. Tetrahydrofuran was

distilled from sodium-benzophenone prior to use. In

all reactions, freshly distilled liquid reagents were

used. a-Trimethylsilylallyl chloride ( A ) was prepared

according to a previously described procedure.5 The gas

chromatographic analysis of the reaction products was

performed using a Varian 2100 instrument equipped with a

capillary column packed with 10% SE-30 (injector 25OoC,

detector 25OoC, column SOOC). 'H NMR spectra were

recorded on a Varian EM 360A spectrometer (60 MHz) I using

TMS as an internal standard.

LDA Demotonation of (11. General Procedure.

A solution of LDA, prepared by reaction of 0.76 g

(7.5 mmol) of diisopropylamine in 7.0 mL of THF with 4.7

mL of 1.6 M ( 7 . 5 mmol) of n-butyllithium in hexane, was

added dropwise to a mixture of 1.04 g (7.0 mmol) of (1)

plus 7.0 mmol of the alkyl halide or trialkylchlorosilane

in 7.0 mL of THF cooled to -78OC. The temperature of the

reaction mixture was allowed to rise to room temperature.

After stirring overnight and dilution with hexane ( 2 0 . 0

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a-TRIMETHY LSILYLALLY L CHLORIDE 1233

mL), 50 mL 10% aq. NHJ1 solution were added. The

aqueous layer was extracted with hexane and the combined

organic layers were dried over anhydrous Na,SO,. After

evaporation of solvents , the oily mixture of the reaction products was analyzed by 'H NMR and GLC.

ACKNOWLEDGEMENTS

We thank to the Direccidn General de Investigacidn

y Postgrado de la Universidad Catdlica de Valparaiso

(Project 125.779/91) for financial support.

REFERENCES

1.

2.

3.

4.

5.

6.

7.

8.

E. Stowell, "Carbanions in Organic Synthesis" , Wiley, New York, 1979.

R. Bates , "Carbanion Chemistry", Springer Verlag , New York, 1983.

J.H. Clark, J. Chem. SOC. Chem. Commun., 789 (1978).

M.T. Reetz and B. Wenderoth Tet. Lett. , 23, 5259 (1982).

M. Julia, J. N. Verpeaux and T. Zahneisen, Synlett,

769 (1990).

D. Seyferth and R. Mammarella, J. Organomet. Chem.,

- 156, 279 (1978).

P. Burford, F. Cooke, G. Roy and P. Magnus,

Tetrahedron, 39, 867 (1981).

P. Magnus and G. Roy, J. Chem. SOC. Chem. Commun.,

297 (1978).

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1234 ARIZ ET AL.

9. a) A. Oliva and A. Molinari, Synth. React. Inorg.

Met. Org. Chem., 14, 253 (1984). b) A. Oliva and A. Molinari, Synth. Comun., 15,

707, (1985).

c) A. Oliva and A. Molinari, Synth. Comun., 17, 837, (1987).

Received: 1 February 1994 Referee I: M. Denk Accepted: 3 May 1994 Referee 11: J . R. Bowser

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