Green Molecular Transformation in Dual Catalysis: Photoredox Activation of Vitamin B₁₂ Using Heterogeneous Photocatalyst

This concept focuses on dual-catalysis using metal complexes and heterogeneous photocatalysts. Vitamin B₁₂ derivatives are sophisticated metal complexes that facilitate enzymatic reactions in the biological systems. The B₁₂ enzymes inspired reactions catalytically proceed in dual-catalyst systems of B₁₂ derivatives and heterogeneous photocatalysts, such as titanium oxide (TiO₂) and metal-organic frameworks (MOFs), under light irradiation. The cobalt ions in B₁₂ 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.