Metal/Amine Cooperative Catalysis. Heteroannulation Route to Quinolines

Significance

Reported is the application of the concept of cooperative catalysis to the synthesis of substituted quinolines from the reaction of 2-aminobenzaldehydes and terminal alkynes. Several combinations of secondary amines and (mostly) copper sources were screened resulting in establishment of the optimum copper pyrrolidine pair. Morpholine and piperidine conjoined with CuI afforded almost equal yields. Silver and gold salts function as well, albeit in lower yields. Substrate scope was well studied, yields are moderate to good, and noteworthy is the fact that aromatic halides survive the reaction conditions. Ketones (2-aminoacetophenone and 2-amino­benzophenone) fail in the reaction. Not all of the 2-aminobenzaldehydes are commercially available.