Regioselective direct ortho C-acylation of phenol and naphthol derivatives catalyzed by modified ZnCl2 on Al2O3 as catalyst under solvent-free and microwave conditions

Abstract

In this study, we present a new and practical method for the synthesis of some ortho C-acylated mono- and di-hydroxyaromatic moieties. A Friedel–Crafts reaction of phenolic substrates was carried out in the presence of zinc chloride supported on alumina as catalyst and carboxylic acids as acylating agents and leads to regioselectively ortho C-acylated compounds with respect to the phenolic hydroxyl group. The reaction proceeds smoothly under microwave irradiation with a wide range of starting materials. This reaction gives access to a variety of acylated compounds in high yield and in the absence of solvent by the use of the more active and stable solid catalyst. In addition, this reaction occurs with high regioselectivity at the ortho position and is compatible with other reported methods. The obtained hydroxyaryl ketones were characterized and confirmed by physical and spectroscopic data.