Construction of C(aryl)-C(alkynyl) bond from copper-mediated arene-alkyne and aryl iodide-alkyne cross-coupling reactions: a common aryl-Cu(III) 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 C(aryl)-C(alkynyl) bond. An alternative mechanism has been proposed for the Castro-Stephens reaction.