Tris(trimethylsilyl)methane and tris(dimethylphenylsilyl)methane: Preparation and comparison of some alkene and cyclopropane derivatives

It is known that metalation of (RMe₂Si)₃CH (R: a = Me, b = Ph) with MeLi in THF yields (RMe₂Si)₃CLi, which when reacted with allyl bromide, (RMe₂Si)₃C-CH₂-CH=CH₂ (1a, 1b) are produced. In this study, although (PhMe₂Si)₃CLi does not react with benzyl bromide, under the same conditions (Me₃Si)₃CLi does, giving the expected product. We found that the bromination of 1b was unsuccessful and the reaction of 1a occurs in low yield due to severe steric hindrance. This idea is supported by our results, which show that, when treated with dichlorocarbene and dibromocarbene, 1a and 1b yield the related dihalocyclopropanes. Furthermore, reduction of the obtained products gives the dehalogenated compounds.