Triple zirconocene/brønsted acid/CuO cooperative and relay catalysis system for tandem Mannich addition/C-C formative cyclization/oxidation

Abstract

A new triple cooperative and relay catalysis system featuring the Mannich addition followed by C-C construction and oxydehydrogenation is described. The zirconocene dichloride and trimellitic acid synergic catalysis triggered the Mannich addition and C-C bond construction reactions, while CuO allowed relay catalysis for oxydehydrogenation. This novel strategy demonstrated superior activity for the synthesis of substituted quinolines from commercially available anilines, aldehydes and ketones. The corresponding substituted quinolines were synthesized with 32 examples in 90-96% yields under mild reaction conditions. A novel zirconocene-Brønsted acid complex, generated in situ and acting as an active catalyst, was validated from the mechanistic studies.