Homogeneous asymmetric hydrogenation of o-substituted acetophenones catalyzed by NH 2Et 2{Ru 2Cl 5[( S)- tol-BINAP] 2}

• Published in: Journal of molecular catalysis. A, Chemical Vol. 159; no. 2; pp. 179 - 184
• Main Authors: Li, Rui-Xiang, Cheng, Pu-Ming, Li, Dong-Wen, Chen, Hua, Li, Xian-Jun, Wessman, Carl, Wong, Ning-Bew, Tin, Kam-Chung
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2000
• Subjects: ( S)- tol-BINAP; o-substituted acetophenone; Ruthenium; Ruthenium; o-substituted acetophenone; ( S)- tol-BINAP
• ISSN: 1381-1169; 1873-314X
• DOI: 10.1016/S1381-1169(00)00188-6

Acetophenones o-substituted by halogen and methoxyl groups were hydrogenated in the presence of (NH 2Et 2){Ru 2Cl 5[( S)- tol-BINAP] 2} at 35°C and 85 kg/cm 2 hydrogen pressure. The results showed that o-bromoacetophenone was a very active substrate and its asymmetric hydrogenation gave an o-bromo-α-phenylethanol with very high enantioselectivity (97% ee). o-Chloroacetophenone was moderately active and its hydrogenation product o-chloro-α-phenylethanol had a good enantioselectivity (82% ee). o-Fluoroacetophenone exhibited a low reactivity but its hydrogenation product o-fluoro-α-phenylethanol showed the highest enantioselectivity (99% ee) among all products. o-Methoxyacetophenone showed a low reactivity, and its hydrogenation product o-methoxyl-α-phenylethanol gave a low enantioselectivity (27% ee). The effects of various reaction conditions, such as hydrogen pressure, reaction temperature, solvents, reaction time, ligand concentration and addition of acid and base, were investigated.