Regioselective formation of alpha-vinylpyrroles from the ruthenium-catalyzed coupling reaction of pyrroles and terminal alkynes involving C-H bond activation.

The cationic ruthenium catalyst Ru(3)(CO)(12)/NH(4)PF(6) was found to be highly effective for the intermolecular coupling reaction of pyrroles and terminal alkynes to give gem-selective alpha-vinylpyrroles. The carbon isotope effect on the alpha-pyrrole carbon and the Hammett correlation from a series of para-substituted N-arylpyrroles (rho = -0.90) indicate a rate-limiting C-C bond formation step of the coupling reaction.