Construction of Caryl–Calkynyl Bond from Copper-Mediated Arene–Alkyne and Aryl Iodide–Alkyne Cross-Coupling Reactions: A Common Aryl-CuIII Intermediate in Arene C–H Activation and Castro–Stephens Reaction

Both copper(II)-mediated oxidative C–H bond activation and oxidative addition of copper(I) into a C–I bond produced an identical and structurally well-defined aryl-Cu(III) intermediate. The cross-coupling reaction of an aryl-Cu(III) intermediate with both terminal alkynes at an elevated temperature and alkynyllithium reagents under mild conditions led effectively to the formation of a Caryl–Calkynyl bond. An alternative mechanism has been proposed for the Castro–Stephens reaction.