Efficient Method for the Esterification of Carboxylic Acids with Alcohols Using Di-2-thienyl Carbonate Promoted by Catalytic Amounts of DMAP and Hf(OTf)4

Esterification of carboxylic acids with alcohols including bulky secondary ones by using an equimolar amount of di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) followed by addition of a catalytic amount of hafnium(IV) trifluoromethanesulfonate (Hf(OTf)4) afforded the corresponding esters in good to high yields.