Copper-Catalyzed Oxidative Alkyne Homocoupling Without Palladium, Ligands and Bases.

Copper-catalyzed green oxidative homocoupling of terminal alkynes can be run to produce symmetrical 1,4-disubstituted 1,3-diynes in good to excellent yields, using air as environmentally friendly oxidant and the occurrence of water as exclusive byproduct in the whole process. This eliminates the need for ligands, bases, oxidants and expensive palladium catalysts.