Selective Construction of 2,4-Bisthioquinolines via Copper-Catalyzed Tandem Cyclization from o-Alkynylphenyl Isothiocyanates

The selective synthesis of polysubstituted quinoline has been recognized as an important but highly challenging transformation. In this study, a highly efficient method for the synthesis of 2,4-bisthioquinolines has been developed through a copper(II)-promoted tandem cycloaddition of o-alkynylphenyl isothiocyanates, utilizing inexpensive and readily available sodium sulfide (Na₂S) as the sulfur source. This transformation enables the direct synthesis of 2,4-bis(thioquinoline) heterocycles via the formation of C-C and C-S bonds in a one-pot reaction, demonstrating excellent tolerance for various functional groups.