Preparation and some reactions of compounds of the type (Me3Si)2C(SiMe2OMe)(SiMe2X). Anchimeric assistance by the methoxy group

Abstract

Because of anchimeric assistance by the γ-OMe group the compound R₂C(SiMe₂OMe)(SiMe₂Cl)(1)(R = SiMe₃ throughout), in contrast to the closely related R₃CSiMe₂Cl, reacts readily with silver salts; thus reactions with AgY or AgBF₄ give the compounds R₂C(SiMe₂OMe)(SiMe₂X) with X = ONO₂, NCO, OCOCF₃ OCOMe, OCOPh, OSO₂C₆H₄Me-p, or F. The anchimeric assistance is so great that even the hydride R₂C(SiMe₂OMe)(SiMe₂H) reacts with silver salts; thus AgOCOCF₃ gives R₂C(SiMe₂OMe)(SiMe₂OCOCF₃). The azide R₂C(SiMe₂OMe)(SiMe₂N₃) was made by treatment of (1) with NaN₃ in (MeOCH₂)₂. Treatment of (1) with water in dioxane gives R₂C(SiMe₂OMe)(SiMe₂OH) in the presence of Et₃N and R₂C(SiMe₂OH)₂ in its absence. Likewise reaction with CF₃CH₂OH gives R₂C(SiMe₂OMe)(SiMe₂OCH₂CF₃) in the presence of Et₃N and R₂C(SiMe₂OCH₂CF₃)₂ in its absence. The bis(trifluoroacetate) R₂C(SiMe₂OCOCF₃)₂ reacts with MeOH more slowly than R₂C(SiMe₂OMe)(SiMe₂OCOCF₃), indicating that the γ-OCOCF₃ provides less anchimeric assistance than the γ-OMe group.