One-pot three-component synthesis of 2H-thiopyrano[2,3-b]quinoline-2,3-dicarboxylates from 2-mercaptoquinoline-3-carbaldehydes, dialkyl acetylenedicarboxylates and Ph3P

The presence of heterocyclic scaffolds in many natural and synthetic products endowed with biological properties is responsible for extensive research in recent years on the synthesis of useful polycyclic structures, that include one or more heteroatoms. The quinolines and quinoline-fused heterocycles are privileged structural units presented in numerous natural products and pharmacologically active compound.1 Considering the importance of the above-mentioned applications and activities, methods for the synthesis of quinoline fused thiopyran structures are of great interest. In this study, our goal was to develop an improved procedure, including enhancing the reaction yield, of the biologically important thiopyran fused quinoline moiety. Following our research interest on the synthesis of quinoline-fused heterocyclic compounds[11,12] we herein used the same strategy reported in the literature for the synthesis of 2H-thiopyrano[2,3-b]quinoline-2,3-dicarboxylates using a one-pot three component coupling of 3-formyl-2-mercaptoquinolines, triphenylphosphine, and dialkyl acetylenedicarboxylate. The reaction was performed at room temperature within 15-30 minutes using DCM as solvent and afforded the products with excellent yields (80-90%).

Keywords:

2-Mercaptoquinoline-3-carbaldehyde , Intramolecular Wittig reaction , Tricyclic framework.