The algar–flynn–oyamada oxidation of α-substituted chalcones

Abstract

2-(α-Hydroxybenzyl)-2-methoxycoumaran-3-ones are major products in the alkaline hydrogen peroxide oxidation (AFO reaction) of 2′-hydroxy-α-methoxychalcones containing a phloroglucinol type A-ring, while flavonols predominate in the oxidation products of chalcones without a 6′-substituent. Under similar oxidation conditions, α-methyl substituted chalcones give corresponding results. Stereochemistry is assigned to the 3-methylflavan-3-ols on the basis of chemical and n.m.r. evidence.