Selective Dimerization of Arylalkynes to (E)-1,4-Diaryl Enynes Catalyzed by the [Ru(p-cymene)Cl2]2/Acetic Acid System under Phosphine-Free Conditions

The commercially available di-chlorobis[(p-cymene)chlororuthenium(II)] complex catalyzes the dimerization of aromatic alkynes in acetic acid at room temperature, to form the corresponding (E)-1,4-diarylbut-1-ene-3-yne derivatives, with high stereoselectivity. The procedure does not require the use of additives and can be carried in the presence of water or aprotic co-solvents, under homogeneous conditions.