Merging Heterogeneous Graphitic Carbon Nitride Photocatalysis with Cobaloxime Catalysis in Uphill Dehydrogenative Synthesis of Anilines

Synthesis of substituted anilines upon nucleophilic addition of secondary amines to cyclohexanone derivatives followed by aromatization of the enamine by employing a combination of Ir-polypyridine complex as a photoredox catalyst and cobaloxime as H2-evolution catalyst was developed recently by Leonori et al. In this work, we replace homogeneous photoredox catalyst by heterogeneous mesoporous graphitic carbon nitride (mpg-CN) that is free of rare elements. Substituted aromatic amine and H2 are formed simultaneously. Combination of X-Ray spectroscopies revealed charge transfer from cobaloxime to mpg-CN in the dark. Illumination of the catalytic system with visible light induces electron transfer from mpg-CN to cobaloxime and formation of persistent Co(II) species. The results of DFT modelling suggest that the studied reaction is strongly endothermic and endergonic. Thus, energy of photons is stored in the reaction products – H2 and the aromatic amine.