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Selective hydrogenation of ethyl-benzoylacetate to 3-hydroxy-3-phenyl-propionate catalyzed by Pd/C in EtOH as a solvent in the presence of KOH: The role of the enolate ion on the reaction mechanism

“…The literature relating this item is large and several review and articles are available on the argument, in particular Ni, Pt and Pd supported and unsupported metal catalysts promoted by chiral modifiers and salts are studied [19][20][21][22][23][24][25][26]. In particular, these authors studied the influences of modifiers and operative variables on reaction rates and enantiomeric excess.…”

“…They observed that, together with a high enantiomeric excess obtained in the hydrogenation of prochiral ketones, in some cases the chiral modifier enhances also the catalytic activity [19,20]. In these papers, surface complex between the ketones and the modifiers are claimed and the chiral nature of the modifier is responsible for the enantioselective hydrogenation [18][19][20][21][22][23][24][25][26]. However, the role of the enolate ion on the reaction mechanism is not investigated and only in the old paper is mentioned [4,5].…”

Asymmetric heterogeneous catalytic hydrogenation; is it a useful tool for the synthetic organic chemist?

“…67,68 These modified catalysts are very specific with respect to the substrate, this means, that the combination of the catalytically active metal and the modifier ensures the enantioselectivity only at a small group of substrates. The most effective heterogeneous catalytic hydrogenating systems are the Ni-tartaric acid, [69][70][71][72][73][74] Pt-cinchona alkaloids, Pd-cinchona alkaloids and vinca alkaloids. [75][76][77] (Scheme 1) In these catalysts the source of chirality is an organic compound, which adsorbs strongly on the surface of the catalyst and creates a chiral environment for the hydrogenation.…”

Study of the properties of nickel oxide and nickel as precursors for the tartaric acid-NaBr-modified nickel catalyst

“…for the enantio-differentiating hydrogenation of b-ketoesters [1][2][3][4]. Many types of activated nickel catalysts are used for preparing the modified catalyst, that is, Raney nickel, a supported nickel, nickel obtained by the reduction of nickel oxide (reduced nickel), and fine nickel powder.…”