Metal-free C-H sulfonamidation of pyrroles by visible light photoredox catalysis.

We report a one-step procedure for the preparation of N-(2-pyrrole)-sulfonamides from sulfonamides and pyrroles. The reaction uses visible light, an acridinium dye as photocatalyst and oxygen as the terminal oxidant for the oxidative C-N bond formation; structures of several reaction products were confirmed by X-ray structure analysis. The reaction is selective for pyrroles, due to the available oxidation power of the photocatalyst and the required stability of the carbocation intermediate under the reaction conditions.