Homogeneous asymmetric hydrogenation of o-substituted acetophenones catalyzed by NH2Et2{Ru2Cl5[(S)-tol-BINAP]2}

✍ Scribed by Rui-Xiang Li; Pu-Ming Cheng; Dong-Wen Li; Hua Chen; Xian-Jun Li; Carl Wessman; Ning-Bew Wong; Kam-Chung Tin

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 107 KB
• Volume: 159
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(00)00188-6

✦ Synopsis

Acetophenones o-substituted by halogen and methoxyl groups were hydrogenated in the presence of Ž . Ä wŽ .

x 4 2 NH Et Ru Cl S -tol-BINAP at 358C and 85 kgrcm hydrogen pressure. The results showed that o-bromoace-

tophenone was a very active substrate and its asymmetric hydrogenation gave an o-bromo-a-phenylethanol with very high Ž . enantioselectivity 97% ee . o-Chloroacetophenone was moderately active and its hydrogenation product o-chloro-a-phenyl-Ž . ethanol had a good enantioselectivity 82% ee . o-Fluoroacetophenone exhibited a low reactivity but its hydrogenation Ž . product o-fluoro-a-phenylethanol showed the highest enantioselectivity 99% ee among all products. o-Methoxyacetophenone showed a low reactivity, and its hydrogenation product o-methoxyl-a-phenylethanol gave a low enantioselectivity Ž . 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.