Cu-catalyzed [2 + 2 + 1] cascade annulation of vinyl iodonium salts with elemental sulfur/selenium for the modular synthesis of thiophenes and selenophenes

Abstract

A [2 + 2 + 1] annulation protocol has been established for the modular synthesis of 2,4-disubstituted thiophenes/selenophenes, with excellent regioselectivity. The reactions have been catalyzed by copper salt with elemental sulfur and selenium serving as the chalcogen source. The mechanistic study has revealed that this process was initiated by a trisulfur radical anion using EPR.