The acetolysis and benzolysis of some carbohydrate oxirans

Abstract

A cyclic acyloxonium ion is formed as an intermediate when a carbohydrate oxiran bearing a vicinal trans-acyloxy-group is heated in acetic acid. In the presence of water the cyclic ion yields a cis-monoester. Under anhydrous conditions, using acetic acid or molten benzoic acid as solvent, three products are generally formed, corresponding to nucleophilic attack at each of the three carbon atoms of the cyclic ion. Possible mechanisms are discussed in the light of other published work on the properties of acyloxonium ions derived from polyols.