Chemo-Selectivity of Group-VIII Metal Catalysts in Hydrogenation of Nonconjugated Enones

Article abstract of DOI:10.1246/bcsj.60.1721

The chemo-selectivity of group-VIII metal catalysts has been examined in the hydrogenation of nonconjugated enones at ambient temperature under an atmospheric pressure of hydrogen.A cobalt catalyst gave high yields of unsaturated alcohols from trialkylated olefinic ketones.Osmium showed the highest selectivity among platinum metal catalysts for the reduction of the carbonyl bond in the hydrogenation of trialkylated olefinic ketones.The hydrogenation of mono- and dialkylated olefinic ketone ordinarily proceeded with a preferential saturation of the olefinic function, regardless of the catalysts.The hydrogenation of 4-methylene- and 4-ethylidenecyclohexanone was accompanied by the formation of diethyl acetals over ruthenium, rhodium, and palladium black catalysts in an ethanol solvent.The acetals were not detected in the hydrogenation of the other enones and over the other catalysts.In addition, the chemoselectivity on the hydrogenation of acyclic enones was examined over nickel and cobalt catalysts treated with small amounts of alkali and carbon monoxide.The amount of unsaturated alcohols increased when the catalyst was treated with alkali in the case of di- and trialkylated olefinic ketones, whereas the characteristics of cobalt, which selectively reduces the ketonic function in trialkylated olefinic ketoones, were completely missing when cobalt was treated with carbon monoxide.