Preparation and reactions of difunctional sterically hindered organosilicon compounds of the type (Me3Si)2C(SiMe2X)(SiMe2Y)

Abstract

Reaction of TsiSiMelCl [Tsi =(Me₃Si)₃C] with AgY or AgBF₄ gave the rearranged species R₂C(SiMe₂Cl)(SiMe₂Y)(Y = OSO₂CF₃, OCIO₃, OCOCF₃, OSO₂C₆H₄Me-p, or F)(R = Me₃Si throughout). Correspondingly, TsiSiMelF reacted with AgSO₃CF₃ to give R₂C(SiMe₂F)(SiMe₂OSO₂CF₃) and with ICI to give R₂C(SiMe₂F)(SiMe₂Cl); TsiSiMelBr likewise gave R₂C(SiMe₂Br)(SiMe₂OSO₂CF₃) on treatment with AgSO₃CF₃ but the di-iodide TsiSiMel₂ reacted even with 1 molar equiv. of various silver salts to give R₂C(SiMe₂Y)₂(Y = F, OCIO₃, OSO₂CF₃ or OSO₂C₂H₄Me-p) along with unchanged TsiSiMel₂. The iodo-hydride TsiSiMeHl gave only unrearranged TsiSiMeHF when treated with AgBF₄ in Et₂O, but a mixture of R₂C(SiMe₂H)(SiMe₂F), TsiSiMeHF, and R₂C(SiMe₂F)₂ when CH₂Cl₂ was used as solvent. Other R₂C(SiMe₂X)(SiMe₂Y) species were made as follows; (i) with X = H; Y = Cl, Br, or I, along with R₂C(SiMe₂X)₂, from R₂C(SiMe₂H)₂ with 1 molar equiv. of X₂; (ii) R₂C(SiMe₂X)₂(X = Br or I) from R2C(SiMe₂H)₂ and 2 molar equiv. of X₂; (iii) with X = F, Y = I, from R₂C(SiMe₂F)(SiMe₂H) and I₂; (iv) with X = OMe, Y = Cl, from R₂C(Cl)(SiMe₂OMe)[via R₂C(Li)(SiMe₂OMe)] and Me₂SiCl₂.

The methanolyses of several R₂C(SiMe₂X)(SiMe₂Y) species were examined, and the results are discussed in terms of anchimeric assistance by the X or Y groups.