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

Allylic 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.