Rh−DuPHOS-Catalyzed Enantioselective Hydrogenation of Enol Esters. Application to the Synthesis of Highly Enantioenriched α-Hydroxy Esters and 1,2-Diols
Citations Over TimeTop 10% of 1998 papers
Abstract
The asymmetric hydrogenation of α-(acetyloxy)- and α-(benzoyloxy)acrylates 4 catalyzed by cationic rhodium−DuPHOS complexes has been examined. A wide range of substrates (4) were prepared via a convenient Horner−Emmons condensation protocol, and subsequently hydrogenated under mild conditions (60 psi of H2) at substrate-to-catalyst ratios (S/C) of 500. Overall, enol ester substrates 4 were reduced by the cationic Et−DuPHOS−Rh catalysts with very high levels of enantioselectivity (93−99% ee). Importantly, substrates 4 bearing β-substituents could be employed as E/Z isomeric mixtures with no detrimental effect on the selectivity. Labeling studies indicated that no significant E/Z isomerization of the substrates occurs during the course of these reactions. Details concerning optimization of the reaction, interesting solvent effects, and deprotection procedures for the synthesis of highly enantioenriched α-hydroxy esters and 1,2-diols also are provided.
Related Papers
- → Atomically dispersed rhodium on a support: the influence of a metal precursor and a support(2014)14 cited
- → Factors determining rhodium solubilization efficiency in molten K2CO3–K2O–B2O3–Al2O3 medium(2023)2 cited
- → The effect of rhodium precursor on Rh/Al2O3 catalysts(1982)54 cited
- → ChemInform Abstract: BASIC METALS. XI. CATIONIC (CYCLOPENTADIENYL)RHODIUM COMPLEXES CONTAINING RHODIUM‐HYDROGEN, RHODIUM‐CARBON, RHODIUM‐GERMANIUM, RHODIUM‐TIN, AND RHODIUM‐HALOGEN BONDS(1979)
- Progress in Rhodium Determination Method for Rhodium-containing Materials(2014)