Cascade reaction synthesis of multisubstituted bicyclic pyridone derivatives

An efficient synthesis of novel bicyclic pyridone derivatives via cascade reaction of heterocyclic ketene aminals (HKAs) and 4-arylmethylene-2-phenyloxazol-5(4H)-ones in the presence of acetic acid has been established. Significantly, the protocol affords a straightforward approach to the construction of multisubstituted bicyclic pyridones in which one C–O bond was cleaved and new C–C and C–N bonds were formed in one pot under mild conditions.