Zn(ClO4)2•6H2O as a powerful catalyst for a practical acylation of alcohols with acid anhydrides

A new protocol for the acylation of alcohols with anhydrides in the presence of Zn(ClO4)(2).6H(2)O as the catalyst is reported. The activity of Zn(ClO4)(2).6H(2)O has been proven to be superior to that exerted by dry Mg(ClO4)(2) and by metal triflates. Its efficiency allows reactions between poorly reactive substrates, such as sterically hindered tertiary alcohols and aromatic anhydrides. All of the reactions were carried out at a 1:1.05 alcohol/anhydride ratio. These conditions are extremely convenient from a practical and economic point of view, since they avoid wasting reagents and allow a simple workup procedure. The catalytic action of Zn(ClO4)(2).6H(2)O is so specific for the activation of the anhydrides, that acid-sensitive functionalities and the stereochemical configuration of the starting materials remain unaltered in the esterification process. In all cases, the acylated products are quantitatively obtained in pure form. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).