Phosphine-free rhodium-catalyzed hydroarylation of diaryl acetylenes with boronic acids

Rh(CO)2(acac) was found to be an efficient and simple catalyst in hydroarylation of diaryl acetylenes with boronic acids in the absence of phosphine ligand. Thus, triaryl-substituted olefins were prepared in good to excellent yields. No 1,4-rhodium shift was observed in the catalytic cycle.