Synthesis of 2,3-disubstituted quinolines from in situ generated imines and its enamine tautomer under radical cation induced conditions

A tandem cyclization/aromatization of anilines and aldehydes was achieved under catalytic radical cation salt induced conditions, producing a series of 2,3-disubstituted quinolines in good yields. In this reaction, the in situ generated imine tautomerizes to enamine, which acts as a dienophile to participate in the tandem cyclization, and further elimination of the anilino group triggers the aromatization of tetrahydroquinolines, avoiding harsh conditions.