[7787-87-3]  · C5H13ClSi  · 1-Chloroethyltrimethylsilane  · (MW 136.72)

(nucleophilic addition of a-lithio derivative to aldehydes and ketones affords epoxysilanes, leading to methyl ketones)

Physical Data: bp 115-116 °C; d 0.862 g cm-3.

Analysis of Reagent Purity: 1H NMR.

Preparative Method: a-lithio derivative prepared from 1-chloroethyltrimethylsilane in THF and s-butyllithium (1.5 M in n-hexane or cyclohexane) at -78 °C, followed by warming to -55 °C.1

Form Supplied in: liquid; commercially available.

Handling, Storage, and Precautions: use in a fume hood.

Treatment of aldehydes and ketones with the a-lithio derivative of 1-chloroethyltrimethylsilane, prepared in situ, gives a,b-epoxytrimethylsilanes in moderate to high yields (35-96%) (eqs 1 and 2.1,2

This bulky carbanion also reacts with sterically hindered ketones in moderate yields (eq 3).1 It is speculated that this carbanion adds to hindered ketones via a single electron transfer mechanism.

Acidic hydrolysis of the resulting a,b-epoxytrimethylsilanes yields homologated methyl ketones (eq 4).3 The carbanion thus acts as a nucleophilic acylating species with reduction taking place at the original carbonyl group. This two-step sequence is more convenient than other methods for this type of homologation and proceeds under milder conditions.4 The intermediate a,b-epoxytrimethylsilane can also be converted into an enol ether, enol acetate, alkenyl bromide, or enamide.5

1. Cooke, F.; Roy, G.; Magnus, P. OM 1982, 1, 893.
2. (a) Cooke, F.; Magnus, P. CC 1977, 513. (b) Magnus, P.; Roy, G. CC 1978, 297.
3. Burford, C.; Cooke, F.; Ehlinger, E.; Magnus, P. JACS 1977, 99, 4536.
4. (a) Lever, Jr.; O. W. T 1976, 32, 1943. (b) Grobel, B.-T.; Seebach, D. S 1977, 357. (c) Earnshaw, C; Wallis, C.J.; Warren, S. JCS(P1) 1979, 3099.
5. Hudrlik, P. F.; Hudrlik, A. M.; Rona, R. J.; Misra, R. N.; Withers, G. P. JACS 1977, 99, 1993.

Raymond S. Gross

Marion Merrell Dow Research Institute, Cincinnati, OH, USA

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.