Synthesis of Cyclic N‐Tosyliminocarbonates by Lewis Acid Catalyzed Allylic Substitution of Trichloroacetimidates

Abstract

AbstractAllylic trichloroacetimidates bearing a δ‐N‐tosylcarbamoyloxy group were prepared in two steps from the corresponding diols, and their Brønsted and Lewis acid catalyzed cyclization reactions were investigated. It was found that N‐tosylcarbamates derived from secondary and tertiary alcohols bearing alkyl substituents undergo a chemoselective allylic alkylation to give N‐tosyliminocarbonates in good isolated yields. In turn, aryl‐substituted substrates tend to give oxazolines by abstraction of the carbamate functionality. The cyclization of N‐tosylcarbamates derived from secondary alcohols preferentially give trans‐iminocarbonates. However, the trans selectivity varied and depended on the substitution pattern, configuration of the substrate, and the catalyst. A high trans selectivity could be achieved from (E) substrates by using TMSOTf as the catalyst. The synthetic utility of iminocarbonates was demonstrated by transforming them into 1,2‐diols and cyclic carbonates as well as into N‐tosyloxazolidinones by a halide ion‐induced rearrangement.