1,2-Dimethylimidazole (DMI) and microwaves in the alkylation of carboxylic acids and phenols with dimethyl and diethyl carbonates

Abstract

A selective alkylation of carboxylic acids and phenols was optimized with 1,2-dimethylimidazole (DMI) using dimethyl carbonate (DMC) and diethyl carbonate (DEC). The reaction mechanism was determined by the formation of the diethoxy(1,2-dimethyl-1H-imidazolidium-1-yl)methoxy (DEIM) intermediate. The dependence of the amount of DMI on the rate of the ethylation reaction was established, concluding that DMI is a novel and active nucleophilic catalyst. The rate of ethyl benzoate formation is shown. The reactions with DEC require more drastic conditions, while those with DMC are achieved with better efficiency under mild conditions. Solvent free microwave reactions with DMI and DMC or DEC proceed at high temperatures. In the absence of DMI these reactions do not proceed. © ARKAT USA, Inc.