Synthetic studies with carbonates. Part 6. Syntheses of 2-hydroxyethyl derivatives by reactions of ethylene carbonate with carboxylic acids or heterocycles in the presence of tetraethylammonium halides or under autocatalytic conditions

Abstract

Reactions of ethylene carbonate (1a) with a variety of carboxylic acids catalysed by tetraethylammonium halides gave the corresponding 2-hydroxyethyl esters along with the diesters arising from disproportionation of the former products induced by the quaternary ammonium halides. Formation of the disproportionation products could be minimized by use of a short reaction time. The autocatalytic reactions of (1a) with strongly acidic carboxylic acids at elevated temperature gave ethylene glycol diesters selectively. Reaction mechanisms are discussed. Reactions of cyclic carbonates such as (1a) and propylene carbonate(1b) with acid anhydrides or active acyl compounds such as p-nitrophenyl acetate in the presence of tetraethylammonium iodide gave alkylene glycol diesters or 2-acyloxyalkyl aryl ethers in high yields. An attempt to extend this reaction to cyclohexane-1,2-diyl carbonate was unsuccessful, but a reaction with 1,2-epoxycyclohexane succeeded; this enabled us to examine the stereochemistry of the reaction. Finally, N-2-hydroxyethylation of a series of heterocyclic compounds having acidic imino hydrogen atoms was performed, both with tetraethylammonium iodide as catalyst and without a catalyst.