The effects of the vinyl groups in reactions of the highly sterically hindered compound [tris(trimethylsilyl)methyl]divinylsilyl chloride

Abstract

The compound TsiSi(CHCH₂)₂Cl, (1)[Tsi =(Me₃Si)₃C] has been found to react with CsF, NaN₃, KSCN, and KOCN in MeOH or MeCN to give TsiSi(CHCH₂)₂X compounds with X = F, N₃, NCS, and NCO, respectively; in the reaction with KSCN in MeCN and CsF in MeOH, (1) is a little more reactive than TsiSiMe₂Cl, (2). Reaction of (1) with AgO₃CCF₃ in CF₃CO₂H gave a ca. 1 : 1 mixture of TsiSi(CHCH₂)₂O₂CCF₃ and its isomer (Me₃Si)₂C[Si(CHCH₂)₂Me](SiMe₂O₂CCF₃), in a process thought to involve an intermediate methyl-bridged silico-cation; in this reaction, (1) is ca. 5 times less reactive than (2), and the significance of this is discussed. Reaction of (1) with 2M NaOMe–MeOH gives the fragmentation product (Me₃Si)₂CHSi(CHCH₂)₂OMe, probably via a sila-olefin intermediate. In the reaction of (1) with LiAlH₄ in Et₂O there is unexpected reduction of vinyl groups, to give a mixture of TsiSi(CHCH)₂H, TsiSiEt(CHCH₂)H, and TsiSiEt₂H.