Oxidative Cross-Coupling of Two Different Phenols: An Efficient Route to Unsymmetrical Biphenols

Abstract

An efficient synthesis of unsymmetrical biphenols via the oxidative cross-coupling of two different phenols in the presence of K2S2O8 and Bu4N+·HSO3– (10 mol %) in CF3COOH at ambient conditions is described. 1:1 Cross-coupling of substituted phenols with naphthols and 1:2 cross-coupling of naphthols with phenol are also disclosed. By using Bu4N+·HSO3–, the homocoupling of phenols or naphthols was controlled. In these reactions, the ortho C–H bond of two different phenols and the ortho and para C–H bond of phenols were coupled together.