Cation Radical Aza-Diels-Alder Reaction between N-Arylimines and N-Vinyllactams: A Facile Synthesis of 4-Lactam-N-yl Tetrahydroquinolines

Cycloaddition of N-arylimines with N-vinylpyrrolidin-2-one or N-vinylazepan-2-one was efficiently induced by tris(4-bromophenyl)aminium hexachloroantimonate producing stereoselectively the corresponding cis-2-aryl-4-(2-oxopyrrolidin-1-yl)- or cis-2-aryl-4-(2-oxoazepan-l-yl)tetrahydroquinoline derivative in good yields.