Wallach Rearrangement

Abstract

The Wallach rearrangement is a strong acid promoted conversion of azoxybenzene and its derivatives into 4‐hydroxyazobenzene and the corresponding substituted hydroxyazobenzenes. The conversion under photo illumination is referred to as the photo‐Wallach rearrangement. The introduction of the hydroxyl group in the azoxybenzene series and naphthyl azoxy series has been discussed and compared it with the photo‐Wallach rearrangement conditions. This reaction has general application in the preparation of hydroxyazobenzenes and hydroxyazonaphthalenes.