Lewis acid promoted synthesis of methylene-bridged α-and γ-bis-benzopyrones

Abstract

The Lewis acid promoted Fries rearrangement of O-methoxyacetyl derivatives of hydroxy-chromanones, coumarins and chromones under solvent-free condition gives isomeric methylene-bridged bischromanones, biscoumarins and bischromones, respectively, in good yields. The benzopyrone precursors undergo intermolecular rearrangement wherein two benzopyrone moieties are joined through their benzene rings via an un-substituted methylene bridge.