Catalytic properties of synthetic linear oligomer–copper complexes in autoxidation of phenols

Abstract

A new type of copper complex composed of intermediate sized ligands was employed as catalyst in the autoxidation of phenols. Among a series of copper catalysts containing urea and thiourea ligands, intermediate sized oligomer ligand [(3), (5), and (8)]–CuCl₂ complexes showed effective catalytic activities in the oxidative coupling of 2,6-xylenol. Reaction rates were high and there was excellent coupling selectivity. The catalytic properties were much different both from those of smaller ligand–copper complexes and from those of polymeric ligand–copper complexes, and seemed to be characteristic of the present type of catalysts.