Photoredox/rhodium catalysis in C–H activation for the synthesis of nitrogen containing heterocycles

The cyclization of acetanilides with alkyne derivatives has been accomplished via a direct C–H functionalization/cyclization pathway in the presence of a photoredox catalyst. The combination of a readily available Rh(III) and photoredox catalyst under irradiation with 11 W CFL afforded not only indoles but also pyrrole derivatives in good yields. Mechanistic studies provide evidence for the independent role of each catalyst. In addition, a similar efficiency of the cyclization reaction was achieved with a heterogeneous photoredox catalyst.