Stereodifferentiation in heterogeneous catalytic hydrogenation. Kinetic resolution and asymmetric hydrogenation in the presence of (S)-proline: Catalyst-dependent processes

Recent Progress in Heterogeneous Asymmetric Hydrogenation of C═O and C═C Bonds on Supported Noble Metal Catalysts

“…The ( S )-Pr-mediated asymmetric hydrogenation of IP has been the focus of several mechanistic studies. ,,,,, The understanding of the reaction mechanism has recently been reviewed. , Nevertheless, the origin of enantioselection of this catalytic system has been the subject of a controversial debate, and even the classification as heterogeneous asymmetric hydrogenation had been in dispute. In contrast to the small amount of chiral modifier generally employed for chirally modified metals (molar ratios of chiral modifier-to-Pd < 1 are used; see section ), early catalytic results indicated that equivalent amounts of ( S )-Pr with respect to the prochiral substrate are required to obtain good enantioselection, which can reach up to 99% ee of ( S )-TMCH.…”

Heterogeneous asymmetric hydrogenation over chiral molecule-modified metal particles

“…8) 48 . Asymmetric hydrogenation of isophorone on proline-modified Pd catalysts stands for another interesting system 63,[97][98][99][100][101][102] . It is generally agreed that kinetic resolution contributed to the enantiomeric excess 63,[97][98][99]105 , but whether it is a real asymmetric 10 catalysis or a solely kinetic resolution process is still a matter of debate.…”

“…12,88 For the hydrogenation of α-ketone esters over CD-Pt catalysts, the CD molecule adsorbed onto Pt surface through the quinoline ring and formed a 1 : 1 substrate/modifier complex through H bonding. [25][26][27][89][90][91] For the asymmetric hydrogenation of CC bonds over Pd catalysts, the recent results for α,β-unsaturated acids, 51,92-96 2-pyrone, [45][46][47][48]54 and isophorone 63,[97][98][99][100][101][102] have advanced the understanding of the reaction mechanism and kinetics.…”

“…48 Asymmetric hydrogenation of isophorone over prolinemodified Pd catalysts represents another interesting system. 63,[97][98][99][100][101][102] It is generally agreed that kinetic resolution contributed to the enantiomeric excess, 63,[97][98][99]105 but whether it is a real asymmetric catalysis or a solely kinetic resolution process is still a matter of debate. It was previously proposed that condensation of isophorone with (S)-proline in a stoichiometric ratio formed an oxazolidinone-type intermediate, followed by diastereoselective hydrogenation of the CC bond; further decomposition of the adduct gave the enantiomer in excess (Fig.…”

Chiral metal nanoparticle-catalyzed asymmetric C–C bond formation reactions

“…62 Very recently, Maeda, Baiker and co-workers proposed a possible intermediate and complex between a substrate and a modifier formed by multiple hydrogen bonds. 64 Based on this chiral NP system, other types of chiral NP catalysts for asymmetric hydrogenation reactions, for example nickel-boride NPs, 68 Pd NPs, [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85] Ru NPs, [86][87][88][89][90] Rh NPs, 88,[91][92][93][94][95][96] Ir NPs, 88,[97][98][99] and Fe NPs, 100 have been widely investigated. Several reviews illustrate examples of heterogeneous asymmetric hydrogenation reactions.…”