Lewis acid catalyzed acylation reactions: scope and limitations

Acylation of alcohols, thiols, and sugars were studied with a variety of Lewis acids, and it was found that Cu- and Sn(OTf)(2) are very efficient in catalyzing the reaction under mild conditions. Among these two catalysts, Cu(OTf)(2) was preferred because of its lower cost and relatively higher yield of the acylated product. The reaction was studied in several solvents, but CH2Cl2 was preferred. It was also observed that the present method is suitable for acylation of tertiary alcohols. Sugars were also acylated without any epimerization at the anomeric center. It is further shown here that this method is also suitable for selective acylation of primary or secondary alcohols over tertiary ones. (C) 2002 Elsevier Science Ltd. All rights reserved.