Controlled Synthesis of Asymmetric Dialkyl and Cyclic Carbonates Using the Highly Selective Reactions of Imidazole Carboxylic Esters

A new highly selective synthesis of dialkyl carbonates is described. The procedures rely on the previously unknown selectivity of imidazole carboxylic esters synthesized by the reaction of 1,1'-carbonyldiimidazole with alcohols. The imidazole carboxylic esters of secondary or tertiary alcohols form carbonates through the exclusive reaction with primary alcohols in polyols containing mixtures of primary, secondary, and tertiary hydroxyl groups without the need for protection. Controlled cyclic carbonate formation is also described.