Electrostatic catalysis by ionic aggregates:: scope and limitations of Mg(ClO4)2 as acylation catalyst

Alkali and alkaline earth metal perchlorates exhibit electrostatic catalysis in the activation of anhydrides for the acylation reaction. Perchlorates with higher values of the charge-size function of the metal ion exhibit better catalytic activity following the order Mg(ClO4)(2)>Ba(ClO4)(2)>LiClO4. Acylation of structurally diverse phenols, thiols, alcohols, and amines have been carried out with stoichiometric amounts of anhydride at room temperature under solvent free conditions in the presence of catalytic amount of Mg(ClO4)(2). Sterically hindered and electron deficient phenols are efficiently acylated. Acylation with sterically hindered anhydrides such as iso-butyric, pivalic, and benzoic anhydrides are carried out with phenols and alcohols in excellent yields. Acid-sensitive alcohols are acylated in excellent yields without any competitive side reactions. (C) 2003 Elsevier Ltd. All rights reserved.