Regioselective Intermolecular Coupling Reaction of Arylketones and Alkenes Involving C-H Bond Activation Catalyzed by an In-Situ Formed Cationic Ruthenium-Hydride Complex.

The cationic ruthenium-hydride complex, formed in-situ from the treatment of the tetranuclear ruthenium-hydride complex {[(PCy(3))(CO)RuH](4)(mu(4)-O)(mu(3)-OH)(mu(2)-OH)} with HBF(4).OEt(2), was found to be a highly effective catalyst for the intermolecular coupling reaction of arylketones and 1-alkenes to give the substituted indene and ortho-C-H insertion products. The formation of the indene products was resulted from the initial alkene isomerization followed by regioselective ortho-C-H insertion of 2-alkene and the dehydrative cyclization. The preliminary mechanistic studies revealed a rapid and reversible ortho-C-H bond activation followed by the rate-limiting C-C bond formation step for the coupling reaction.