Asymmetric Hydrogenation of Acetonaphthone Catalyzed by RuCl2[P(C6H5)3]2-(R, R)-DPEN

A novel ruthenium complex RuCl2[P(C6H5)3]2-(R, R)-DPEN (DPEN = 1,2-diphenylethylenediamine) was synthesized, characterized by 1H and 31P NMR, and applied to the asymmetric hydrogenation of acetonaphthone. The effects of reaction temperature, hydrogen pressure, and molar ratio of base to catalyst on the activity and enantioselectivity were investigated in an isopropanol solution of (CH3)3COK. The results showed that the increase in the temperature and pressure accelerated the reaction but slightly decreased the enantioselectivity for (S)-α-naphthylethanol. Under the conditions of acetonaphthone:(CH3)3COK:Ru = 50000:450:1 (molar ratio), 4 MPa, 25°C, and 16 h, 83% ee and 100% yield of α-naphthylethanol were achieved.