Organocatalytic asymmetric synthesis of pyrrolo[3,2-c]quinolines via a formal [3+2] cycloaddition-lactamization cascade reaction using a bifunctional squaramide catalyst

A simple organocatalytic strategy for the asymmetric synthesis of pyrrolo[3,2-c]quinolines has been developed using N -protected o -amino aromatic aldimines and α , β -unsaturated azlactones in the presence of a cinchona-based H-bonding bifunctional squaramide catalyst via a formal [3 + 2] cycloaddition-lactamization cascade reaction. The chiral pyrrolo[3,2-c]quinoline derivatives are obtained in good yields, moderate enantioselectivities and excellent diastereoselectivities. An asymmetric synthesis of pyrrolo[3,2-c]quinolones employing H-bonding bifunctional organocatalysis is reported for the first time.