Dye-sensitized hematite compososite photocatalyst and its photocatalytic performance of aerobic annulation

A visible light initiated catalyst (DP-pfa@Fe 2 O 3 ) is synthesized and used as a photocatalyst for the synthesis of pyrazoles under mild reaction conditions. Holes (h + ) and   OH are the essential for the light-induced the pyrazole annulation reaction using water as oxygen source. Results demonstrate that photocatalyzed reaction of methyl hydrazine and 2-benzylidenemalononitrile produced 2-((2-methylhydrazinyl)(phenyl)methylene)malononitile, which can transfer into pyrazoles in the presence of ∙ OH. Our results provide a new catalyst and an economic synthetic method for the synthesis of pyrazoles through aerobic annulation.