Oxidation of 2′-hydroxy-α-phenylchalcones: substituent effects on the course of the Algar–Flynn–Oyamada (AFO) reaction

Abstract

In alkaline hydrogen peroxide, 2′-hydroxy-α-phenylchalcones with and without a 6′-methoxy-substituent cyclised preferentially at the β-carbon atom to give chromanones. Fusion of a benzene ring at the 5′- and 6′-positions in the chalcone affected the directive influence of the α-phenyl group, and AFO oxidation afforded a 1 : 1 mixture of α- and β-cyclisation products. Products of aerial oxidation of the chalcones were also studied.