Regioorientation in the Addition Reaction of [alpha]-Substituted Cinnamonitrile to Enamines Utilizing Chitosan as a Green Catalyst: Unambiguous Structural Characterization Using 2D-HMBC NMR Spectroscopy

Hexahydroquinolines and their fused derivatives are obtained in good to excellent yields by proceeding through a simple, mild, and efficient procedure including the reaction of enamines with substituted cinnamonitriles using DABCO, piperidine, or chitosan as catalysts. The regioorientation of Michael addition was established with no doubt using the 2D-HMBC spectroscopy.