ZrOCl2•8H2O as an efficient, environmentally friendly and reusable catalyst for synthesis of benzoxazoles, benzothiazoles, benzimidazoles and oxazolo[4,5-b]pyridines under solvent-free conditions

A new and efficient method for the preparation of benzoxazoles, benzothiazoles, benzimidazoles and oxazolo[4,5-b]pyridines from reactions of orthoesters with o-substituted aminoaromatics and 2-amino-3-hydroxypyridine in the presence of catalytic amounts of the moisture stable, inexpensive ZrOCl2.8H(2)O under solvent-free conditions is presented. This new protocol has the advantages of easy availability, easy handling, stability, reusability and eco-friendly of the catalyst, high yields, very short reaction times, solvent-free reaction conditions, simple experimental and work-up procedure. (c) 2007 Elsevier B.V. All rights reserved.