Ruthenium-Catalyzed Reactions of Acyclic α,β-Enones with Olefins and Their Reaction Mechanisms

The reaction of 4,4-dimethyl-5-phenyl-4-peneten-3-one with styrene (2) using Ru(H)2(CO)(PPh3)3 as the catalyst gave the stereochemically retained product. In the case of 2,2-dimethyl-4-hexen-3-one, the stereochemically inverted branched product was obtained. These results are consistent with two different reaction pathways operating, i.e. one involving a direct C-H bond cleavage and the other, a pathway involving hydrometallation.