A green synthesis of unsymmetrical 9-arylxanthenes in a one-pot cascade benzylation/annulation/dehydration strategy

Abstract

A green synthesis of unsymmetrical 9-arylxanthenones is described using Ca(OTf)2 in one-pot cascade benzylation, annulation and dehydration strategy starting from readily accessible π-activated carbinols. 4-Hydroxycoumarin/cyclohexane-1,3-dione required to be refluxed in water with 2-(hydroxy(phenyl)methyl)phenol derivatives in the presence of 5 mol % of Ca(OTf)2 to yield the unsymmetrical 9H-xanthenes, whereas α/β-naphthols reacted under solvent free-microwave irradiation conditions. Use of ecofriendly alkaline earth catalyst, water as the solvent, mw-irradiation, substrate scope and high yields make this methodology more amenable.