Addition of pyrroles onto terminal alkynes catalyzed by a dinuclear ruthenium (II) complex

The addition of pyrroles onto alkynes has been catalyzed by a dinuclear ruthenium complex, Ru2(CO)4(PPh3)2Br4, resulting in the formation of geminal 2-vinylpyrroles in high yields under mild conditions. Further functionalization with pyrroles or alkynes to afford dipyrrolmethanes or 2,5-bis(vinyl)pyrroles via the vinyl functional group can readily be achieved. A mechanism involving cationic ruthenium complexes was proposed based on the product regioselectivity, deuteration and infrared spectroscopic studies carried out on the catalytic process.