Reactions of dithiane derived alcohols: promotion of the Thorpe-Ingold effect by trimethylsilyl and t-butyl substituents

Abstract

A range of 2-(2-hydroxyethyl)-1,3-dithianes has been prepared and treated with halogenating agents. 2-Monosubstituted dithiane alcohols gave the expected halides whereas 2,2-disubstituted dithiane alcohols underwent elimination to give styrenes (if the substituent was 2-hydroxy-2-phenylethyl) or ring expansion to give 1,5-dithiacyclo-oct-2-enes (if the substituent was 2-hydroxyethyl). Elimination and ring expansion were observed with Me, Bu^t, and Me₃Si as the ‘anchoring’ substituents at C-2, these processes being facile with the larger groups. A rationalization of these results is presented which indicates that the Bu^t and Me₃Si groups are particularly effective at promoting the Thorpe-Ingold effect.