Photocatalytic Aerobic Dehydrogenation of N-Heterocycles with Ir(III) Photosensitizers Bearing the 2(2?-Pyridyl)benzimidazole Scaffold

Photoredox catalysis constitutes a very powerful tool inorganic synthesis, due to its versatility, efficiency, and the mild conditionsrequired by photoinduced transformations. In this paper, we present anefficient and selective photocatalytic procedure for the aerobic oxidativedehydrogenation of partially saturated N-heterocycles to afford the respectiveN-heteroarenes (indoles, quinolines, acridines, and quinoxalines). Theprotocol involves the use of new Ir(III) biscyclometalated photocatalystsof the general formula [Ir(C<^>N)2(N<^>N ')]Cl, where the C<^>N ligand is 2-(2,4-difluorophenyl)pyridinate, and N<^>N ' are different ligands based on the2-(2 '-pyridyl)benzimidazole scaffold. In-depth electrochemical and photo-physical studies as well as DFT calculations have allowed us to establishstructure-activity relationships, which provide insights for the rational designof efficient metal-based dyes in photocatalytic oxidation reactions. Inaddition, we have formulated a dual mechanism, mediated by the radicalanion superoxide, for the above-mentioned transformations

Automated summary

Photoredox catalysis is a powerful tool in inorganic synthesis, and this paper presents an efficient and selective photocatalytic procedure for the oxidative dehydrogenation of partially saturated N-heterocycles to produce N-heteroarenes. The researchers established structure-activity relationships and proposed a dual mechanism for the reactions based on in-depth experimental and theoretical studies.