A different approach to esterification involved the use of alkyl halides or chloroformates as reagents instead of alcohols. Aromatic, aliphatic, and heteroaromatic carboxylic acids were converted into the corresponding esters by reaction with allyl and benzyl bromides or alkyl iodides over Celite/CsF as a solid base in refluxing acetonitrile (Table 18, entry 10).159
Esterification of chiral R-substituted carboxylic acids proceeded in excellent yields with retention of con-