An efficient approach to construct 2-arylbenzo[b]furans from 2-methoxychalcone epoxides

An efficient and practical method for construction of 2-arylbenzo[b]furans from 2-methoxychalcone epoxides has been reported. Catalyzed by 2 mol % of BF3·Et2O, 2-methoxychalcone epoxides went through the Meerwein rearrangement, followed by deformylation in one-pot to successfully afforded 2-methoxydeoxybenzoins. Afterward, 2-arylbenzo[b]furans were obtained in high yields (87%–100%) via intermolecular cyclodehydration of 2-methoxydeoxybenzoins with 48% HBr. By utilization of this approach, the natural product stemofuran A and the key intermediate of eupomatenoid 6 have been synthesized conveniently.