[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
Raymond S. Gross
Marion Merrell Dow Research Institute, Cincinnati, OH, USA