Green Molecular Transformation in Dual Catalysis: Photoredox Activation of Vitamin B 12 Using Heterogeneous Photocatalyst.

This concept focuses on dual-catalysis using metal complexes and heterogeneous photocatalysts. Vitamin B 12 derivatives are sophisticated metal complexes that facilitate enzymatic reactions in the biological systems. The B 12 enzymes inspired reactions catalytically proceed in dual-catalyst systems of B 12 derivatives and heterogeneous photocatalysts, such as titanium oxide (TiO 2 ) and metal-organic frameworks (MOFs), under light irradiation. The cobalt ions in B 12 derivatives are effectively reduced by photoexcited photocatalysts, producing low-valent Co(I) species. The photoinduced nucleophilic Co(I) species react with an alkyl halide to form an organometallic complex with a Co-C bond. The Co-C bond dissociates during photolysis to generate alkyl radicals. Based on this mechanism, dual-catalysis effectively promotes various light-driven organic syntheses and light-driven dehalogenation reactions of toxic alkyl halides. The trends of the dual-catalyst system and recent progress in this field are discussed in this concept.