Reactions of heteroarylhydrosilanes with dichlorocarbene under phase-transfer conditions

Abstract

The reactions of dimethyl(2-thienyl)-, methyl[di(2-thienyl)]-, tri(2-thienyl)- and dimethyl(2-furyl)silanes (I–IV, respectively) with dichlorocarbene generated from sodium trichloroacetate under solid-liquid phase-transfer conditions afford the corresponding dichloromethylsilanes in 38–66% yield. The reactivity of the thienylsilanes decreases with the number of electron-accepting thienyl substituents at the silicon atom. Using the competition reactions, the relative rate constants for the reaction of dichlorocarbene insertion into the SiH bond of thienyl- and furyl-silanes (I and IV) were measured. The reactivity of these silanes was found to be greater than had been expected taking as a basis the Taft σ * constants for the substituent at the silicon atom. This is apparently due to the existence of a p π— d π interaction between the heterocyclic π-system and the d-orbitals of silicon.