Direct Synthesis of Esters and Amides from Unprotected Hydroxyaromatic and -aliphatic Carboxylic Acids

A facile method for the activation of hydroxy-substituted carboxylic acids using benzotriazole chemistry without prior protection of the hydroxy substituents is presented. The N-acylbenzotriazole intermediates 2a−g, 6a−d, and 9a−c have been used for high-yielding synthesis of both aliphatic (3a−l) and aromatic (7a−h, 10a−f) hydroxy carboxamides. High yields of aromatic hydroxy esters 12a−h and 13a−i were obtained using either neat alcohols in neutral microwave conditions or nucleophilic alkoxides and the intermediate N-(arylacyl)benzotriazoles. Moderate yields were obtained in the case of aliphatic hydroxy esters 11a,b and thiolesters 11e−g from the intermediates 2a−c.