(A) new convenient method for the esterification of carboxylic acids

Abstract

Reaction of carboxylic acids with equimolar amounts of alkyl chloroformates and triethylamine in the presence of a catalytic amount of 4-N, N-dimethylaminopyridine (DMAP) affords the corresponding esters in high yields without the formation of the symmetrical anhydride in most carboxylic acids. The reaction proceeds rapidly and smoothly in methylene chloride at $0\,^\circ\!C$. However, the formation of the symmetrical acid anhydride as a minor product is observed in the esterification of aromatic carboxylic acids. Also, it is found that increment of the amount of DMAP drastically decreases the formation of symmetrical acid anhydride. Furthermore, this method reaches a limit with sterically hindered carboxylic acids.