Substitution of acyclic sugar acetals. Perchloric acid catalyzed acetolysis of poly-O-acetyl acyclic oxygen and sulfur acetals and epimerization of monothioacetals

Abstract

The rate constants are reported for the substitution of acyclic sugar poly-0-acetyl diethyl dithioacetals, poly-0-acetyl diethyl acetals, and poly-0-acetyl dimethyl acetals and for the epimerization of poly-0-acetyl S-ethyl monothioacetals when catalyzed by perchloric acid in acetic acid. All the reactions are pseudo first order. Monothioacetals substitute faster than oxygen acetals, and oxygen acetals substitute faster than sulfur acetals. A group bonded to C1 of these acyclic sugar derivatives is substituted faster than when the group is bonded to C1 of poly-0-acetyl pyranose derivatives.