Superacid-promoted synthesis of quinoline derivatives.

A series of vinylogous imines have been prepared from anilines and cinnamaldehydes. These substrates react in superacidic media to provide quinolines and related compounds. A mechanism for the conversion is proposed which involves the cyclization of dicationic superelectrophilic intermediates. Aromatization of the quinoline ring is thought to occur by superacid-promoted elimination of benzene.