A Simple and Mild Acylation of Alcohols, Phenols, Amines, and Thiols with a Reusable Heteropoly Acid Catalyst (H6P2W18O62·24 H2O)

Gustavo P Romanelli,Daniel O Bennardi,Graciela T Baronetti,Juan C Autino,Horacio J Thomas

doi:10.1155/2008/945898

Abstract

The acylation of alcohols, phenols, thiols, and amines with varied substitution using acid anhydrides is efficiently catalyzed by Wells-Dawson heteropoly acid (H6P2W18O62·24 H2O). Reactions proceed with very good to excellent yield in air at room temperature, using toluene as solvent (40 examples). The bulk catalyst was easily reused without appreciable loss of its activity.

Highlights

Hydroxyl and amino groups are widely occurring functional groups in molecules in nature, and they can be found in a number of compounds of biological and synthetic significance[1] including flavonoids, steroids, carbohydrates, amino acids, nucleosides, etc.Protection of alcoholic and phenolic hydroxyl groups is currently required, acetylation being one of the most general reactions
Amines and thiols are acylated using Lewis acids as catalysts, for example LiCl,7d Mg(ClO4)27e, or InCl37g. In spite of their efficiency, the above mentioned soluble catalysts have some disadvantages: industrial use of mineral acids leads to serious environmental problems due to highly acidic waste streams; Lewis acids are efficient as catalysts but most of them are wasteful because they are usually hydrolyzed during the isolation, and triflates are generally expensive
In the present letter we report a catalytic procedure for acylating a variety of primary and secondary alcohols, phenols, amines, and thiols with Ac2O at room temperature in toluene

Summary

Introduction

Hydroxyl and amino groups are widely occurring functional groups in molecules in nature, and they can be found in a number of compounds of biological and synthetic significance[1] including flavonoids, steroids, carbohydrates, amino acids, nucleosides, etc. Protection of alcoholic and phenolic hydroxyl groups is currently required, acetylation being one of the most general reactions. Amines and thiols are acylated using Lewis acids as catalysts, for example LiCl,7d Mg(ClO4)27e, or InCl37g. In the present letter we report a catalytic procedure for acylating a variety of primary and secondary alcohols, phenols, amines, and thiols with Ac2O at room temperature in toluene. This procedure can be used for preparing phenyl and alkyl esters from other acid anhydrides, under heterogeneous catalysis by bulk WD acid

General Procedures

Results and Discussion

Conclusions