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 treatement of the tetranuclear ruthenium hydride complex {[(PCy3)(CO)RuH](4)(mu(4)-O)(mu(3)-OH)(mu(2)-OH)} with HBF4 center dot OEt2, was found to be a highly effective catalyst for the intermolecular coupling reaction of arylketones and 1-alkenes to give substituted indene and ortho-C-H insertion products. The formation of the indene products resulted from the initial alkene isomerization ortho-C-H insertion of 2-alkene and 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. C-C bond formation step for the coupling reaction.