1-Methyl-1-(trimethylsilyl)allene

bp 111 °C; bp 54–56 °C/90 mmHg

It is widely used as propargylic anion equivalents; three-carbon synthons for [3 + 2] annulations leading to five-membered compounds including cyclopentenes,4 dihydrofurans, pyrrolines, isoxazoles, furans, and azulenes.

3-(Trimethylsilyl)-1,2-butadiene may be used for the synthesis of γ-(trimethylsilyl)allylborane.

1-methyl-1-(trialkylsilyl)allenes can be conveniently prepared by the method of Vermeer. Silylsubstituted propargyl mesylates thus undergo SN2 displacement by the organocopper reagent generated from methylmagnesium chloride, copper(I) bromide, and lithium bromide 1-Methyl-1-(trimethylsilyl)allene is produced in 52% yield from commercially available (trimethylsilyl)propargyl alcohol in this fashion (eq 1). The t-butyldimethylsilyl and triisopropylsilyl analogs are synthesized by the same method in 90% and 58% yield, respectively. Propargyl alcohols bearing these and other trialkylsilyl groups can be prepared by treatment of propargyl alcohol with n-butyllithium and the appropriate trialkylsilyl chloride. Allenylsilanes bearing other C-1 substituents can be prepared in an analogous manner by using the appropriate Grignard reagents.