The reduction of some o-nitrophenylazo dyes with glucose: a general synthesis of 2-Aryl-2H-benzotriazole 1-oxides

Abstract

The reduction of some representative o-nitrophenylazo dyes in ethanolic alkali with glucose gives the corresponding 2-aryl-2H-benzotriazole 1-oxides in excellent yield. These 1-oxides are rapidly reduced to the parent benzotriazoles at room temperature by means of zinc dust/ethanolic alkali. This method provides a convenient preparation for 5-chlorobenzotriazoles, which are otherwise readily dechlorinated by zinc dust under more vigorous conditions.