Facile construction of densely functionalized thiopyrano[2,3-b]quinolines via three-component reactions catalyzed by l-proline

Abstract

L-Proline catalyzed, three-component reactions of 2-mercaptoquinoline-3-carbaldehyde, malononitrile and thiol-based nucleophiles were developed for the first time, for the synthesis of various 4H-substituted thiopyrano[2,3-b]quinolines derivatives via a Knoevenagel condensation followed by inter-intramolecular double Michael addition reaction. This transformation leads to the generation of a 4-substituted thiopyran ring, together with one C–C and two C–S bonds in a single operation.