Synthesis of Optically Active 2H-Thiopyrano[2,3-b]quinolines with Three Contiguous Stereocenters via an Organocatalytic Asymmetric Tandem Michael-Henry Reaction

Optically active 2H-thiopyrano[2,3-b]quinolines with three contiguous stereocenters have been synthesized via a chiral bifunctional squaramide-catalyzed tandem MichaelHenry reaction between 2-mercaptoquinoline-3-carbaldehydes and nitroolefins. The reactions proceed with excellent diastereo- and enantioselectivity to give the title compounds in high yields with high levels of diastereo- and enantioselectivity (up to >99/1 dr and >99% ee, respectively).