Photoinduced Regioselective Sulfonylation/Cyclization of N-Cinnamylenamides toward Sulfonylated Tetrahydropyridines via Catalytic Electron Donor-Acceptor Complexes.

N-Cinnamylenamide was designed as a new skeleton for the construction of tetrahydropyridine. Photoinduced regioselective cascade sulfonylation/cyclization of N-cinnamylenamides with sulfonyl chlorides was achieved by catalytic electron donor-acceptor (EDA) complex with PTZ as the catalyst, affording sulfonylated tetrahydropyridines in 41-88% yields. In this EDA complex-driven approach, the newly introduced sulfonyl group was directly installed in the tetrahydropyridine core rather than the side chain. The reaction proceeded under mild conditions with good functional group compatibility and avoided the requirement of a transition metal catalyst.