Bi-Catalyzed Trifluoromethylation of C(sp 2 )-H Bonds under Light.

We disclose a Bi-catalyzed C-H trifluoromethylation of (hetero)arenes using CF 3 SO 2 Cl under light irradiation. The catalytic method permits the direct functionalization of various heterocycles bearing distinct functional groups. The structural and computational studies suggest that the process occurs through an open-shell redox manifold at bismuth, comprising three unusual elementary steps for a main group element. The catalytic cycle starts with rapid oxidative addition of CF 3 SO 2 Cl to a low-valent Bi(I) catalyst, followed by a light-induced homolysis of Bi(III)-O bond to generate a trifluoromethyl radical upon extrusion of SO 2 , and is closed with a hydrogen-atom transfer to a Bi(II) radical intermediate.