Porphyrin-Catalyzed Photochemical C-H Arylation of Heteroarenes

Organic dyes are a promising class of photoredox catalysts and offer a meaningful alternative to broadly applied Ru and Ir complexes. We found that porphyrins with tuned physicochemical properties, by tailoring various substituents at the periphery of the macrocycle, are effective in catalyzing the light-induced direct arylation of heteroarenes and coumarins with diazonium salts. Mechanistic studies confirmed that the reaction operates by an oxidative quenching pathway of the porphyrin.