Copper-Catalyzed Synthesis of Quinoline-4-thiols from Diaryliodonium Salts, Alkynyl Sulfides, and Nitriles.

A three-component cascade cyclization catalyzed by copper was employed to synthesize quinoline-4-thiols using easily available diaryliodonium salts, alkynyl sulfides, and nitriles as starting materials. Sulfur atoms play an important role in controlling the regioselectivity, by stabilizing the high-valent vinyl copper intermediate. Meanwhile, the sulfide group at position 4 of quinoline could be further utilized as a transformable group for ipso-transformation and as a directing group for C-H functionalization, affording various multifunctional quinoline derivatives.