Solvent-free esterification of alcohols, silyl and tetrahydropyranyl ethers with carboxylic anhydrides using hexachloroacetone as an catalyst

Esterification reaction is one of the most important strategies in organic synthesis due to its various applications in different fields such as drug synthesis (e.g. aspirin) and agricultural chemistry. Some important compounds such as oils, flavoring agents and fragrances and synthetic polymers contain the carboxylic ester moiety in their structures [1]. In addition, this reaction can be used for protection of hydroxyl group in some multi-step synthesis. In order to increase the efficiency of this reaction and access to better results, carboxylic esters have been obtained from the reaction of alcohols with activated carboxylic acid derivatives such as carboxylic anhydrides instead of carboxylic acids [2].Now in the present abstract, in continuation of our previous work on the esterification of aromatic aldehydes with alcohols (1:1) using air as the simplest available oxidant and KCN [3], we report an efficient method for the conversion of alcohols, silyl and tetrahydropyranyl ethers to carboxylic esters using carboxylic anhydrides (0.5-0.8 equiv.) in the presence of hexachloroacetone (1 mol%) as a catalyst under solvent-free conditions with gentle heating. Different types of starting materials such as benzylic and phenolic containing electron withdrawing or donating groups in various positions of phenyl ring, cyclic, allylic and primary, secondary and tertiary aliphatic can be easily esterified in excellent yields via the present method (Scheme 1).