Radical cation salt induced tandem cyclization between anilines and N-vinyl amides: synthesis of 2-methyl-4-anilino-1,2,3,4-tetrahydroquinoline derivatives

Tandem cyclization of imines and N-vinyllactams induced by TBPA+ was investigated and a series of 2-methyl-4-anilino-1,2,3,4-tetrahydroquinolines were synthesized based on a domino process in which N-vinyllactams serve as an acetaldehyde equivalent. A single electron transfer mechanism was proposed and radical cation salt acts as both a Lewis acid and one electron oxidant to induce such transformation.