Silica gel catalysed generation of episulfonium ions: a mild method for the synthesis of heterocycles

Abstract

β-Carbonyloxy sulfides fragment when heated with silica or alumina to produce reactive episulfonium ion intermediates. Intramolecular activation of the leaving group and concurrent protection of a nitrogen or oxygen nucleophile via a cyclic carbamate or carbonate leads to the formation of pyrrolidines or cyclic ethers.