Transformation of N, N-Dimethylaniline N-Oxides into Diverse Tetrahydroquinoline Scaffolds via Formal Povarov Reactions.

A one-pot protocol for the assembly of diversely functionalized tetrahydro-, hexahydrofuro-, hexahydropyrano-, and tetrahydrobenzofuroquinolines from N, N-dimethylaniline N-oxides and various electron-rich olefins in a tandem Polonovski-Povarov sequence is reported. Following activation of the N-O bond with Boc2O, an exocyclic iminium ion is unveiled upon exposure to tin(IV) chloride. A formal inverse-electron-demand aza-Diels-Alder cyclization generates the tetrahydroquinoline core of 29 examples in up to 92% yield.