Mild and Simple Access to Diverse 4-Amino-substituted 2-Phenyl-1,2,3,4-tetrahydroquinolines and 2-Phenylquinolines Based on a Multicomponent Imino Diels-Alder Reaction

A straightforward synthesis of new 1-(2-phenyl-1,2,3,4-tetrahydroquinolin-4-yl) pyrrolidin-2-ones/azepan-2-one from N-vinyl caprolactam/N-vinylpyrrolidin-2-one and N-benzylideneaniline via the imino Diels-Alder reaction has been reported for the first time. Antimony(III) chloride has been shown to effectively catalyze imino-Diels-Alder reaction to afford both 2-phenylquinoline and 2-phenyl-1,2,3,4-tetrahydroquinolin derivatives in excellent yields at ambient temperature. The cis diastereoselectivity to give cis 2-phenyl-1,2,3,4-tetrahydroquinolines is also highlighted in this reaction.