Formation of carboxamides by direct condensation of carboxylic acids and amines in alcohols using a new alcohol- and water-soluble condensing agent:: DMT-MM

Selective formation of carboxamides in an alcohol or water by an exceptionally convenient one-step procedure in which a condensing agent is simply added to a mixture of acids and amines has been achieved successfully by using a new condensing agent, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). Activation of carboxylic acids by DMT-MM in the presence of amines and subsequent aminolysis of the resulting acyloxytriazine in alcoholic solvents occurred selectively and led to the formation of carboxamides in excellent yields. The rate of aminolysis of the acyloxytriazine intermediate can be estimated to be about 2x10(4) times greater than that of methanolysis. The amide/ester selectivity observed using DMT-MM was much larger than that obtained with DCC or EDC. Condensation of polar substrates, such as amino acid esters and their hydrochlorides, glucosamine hydrochloride, sodium acetate and dicarboxylic acids, proceeded successfully in MeOH, water or aqueous MeOH in good yields. The present reaction is technically quite simple and easy to achieve. It proceeds by simple mixing of acids, amines and DMT-MM without any additives, and the MeOH is readily removable by a rotary evaporator after completion of the reaction. (C) 2001 Elsevier Science Ltd. All rights reserved.