A new silicon-mediated elimination-rearrangement

Treatment of trimethylsilylethanes bearing α-phenyl groups and β-phenylthio, phenylsulfonyl or cyano groups with LDA causes elimination–rearrangement mediated by the β-carbanionic species. Mechanistic conclusions are based on isotopic labelling experiments, the effects of substituents and approximate kinetics. These suggest that trimethylsilyl is the migrating group, that cleavage of the bond to the leaving group is little advanced in the transition structure and that placing of a substituent to encourage Si–C bond cleavage is mandatory.