Enantioselective hydrogenation of levulinic acid esters in the presence of the RuII-BINAP-HCl catalytic system
- Cite this article as:
- Starodubtseva, E.V., Turova, O.V., Vinogradov, M.G. et al. Russ Chem Bull (2005) 54: 2374. doi:10.1007/s11172-006-0125-2
- 238 Downloads
The rate of hydrogenation of γ-ketoesters MeCOCH2CH2COOR (R = Et, Pri, But) in the presence of the chiral RuII—BINAP catalyst (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5–10 equivalents of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially formed would cyclize by ∼95% to give γ-valerolactone with optical purity of 98–99% ee. When the Ru(COD)(MA)2—BINAP—HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester (R = Et) in EtOH is attained in 5 h at 60 °C under an H2 pressure of 60–70 atm.