Rapid access of 2,3,4-trisubstituted-2,3,4,9-tetrahydrothiopyrano[2,3-b]indole derivatives via one-pot three component reaction using organocatalysis

A simple, green, and efficient one-pot three component strategy for the synthesis of 2-aryl-3-nitro-4-hydroxy-2,3,4,9-tetrahydrothiopyrano[2,3-b]indole derivatives has been achieved by the combination of N-protected-2-chloro-3-formylindoles, sodium hydrosulfide with β-nitrostyrenes at room temperature in ethanol using DABCO as a catalyst. Furthermore, high enantio- and diastereoselectives' syntheses of title compounds have been achieved for the first time using cupreidine (5 mol %) as catalyst, providing good to excellent yields.