Year 2005, Month 10 (Section Full Articles, Page 2374)
Enantioselective hydrogenation of levulinic acid esters
in the presence of the RuII—BINAP—HCl catalytic system
E. V. Starodubtseva, O. V. Turova, M. G. Vinogradov, L. S. Gorshkova, and
V. A. Ferapontov
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.
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