Asymmetric reduction of ketones by homogeneous catalytic hydrogenation

Chiral monodentate phosphorus ligands for rhodium-catalyzed asymmetric hydrogenation

“…11 The first asymmetric homogeneous hydrogenation of ketones (acetophenone and butan-2-one) was carried out at room temperature under 1 bar of hydrogen in ethanol in the presence of catalytic amounts of [Rh(nbd)(benzylmethylphenylphosphine 2) 2 ][ClO 4 ] (nbd ¼ norbornadiene) as catalyst and provided very low enantioselectivities. 12 4 ]. 14 Rhodium complexes with two coordinated diastereomeric P-chiral phosphine 5 involving a menthyl or neomenthyl group as an additional chiral fragment were used to chemo-and enantioselectively hydrogenate the acrylic double bond of (E)-3,7-dimethylocta-2,6-dienoic acid (geranic acid) with 79% ee under mild conditions.…”

“…17 Phosphetane 9 appeared to be difficult to coordinate to rhodium, while the iridium complex proved to be able to hydrogenate N-acetyldehydrophenylalanine methyl ester but with low enantioselectivity. 18 C 2 -Symmetrical chiral monophosphines, where the phosphorus atom is included in a four, five, six and seven-membered ring, have been investigated in the asymmetric hydrogenation of a-acetamidocinnamic acid derivatives under typical conditions (Table 1, ligands [10][11][12][13][14].…”

Synthesis and application of chiral monodentate phosphines in asymmetric hydrogenation

“…Some P-stereogenic phosphines were initially tested in the hydrogenation of acetophenone and butan-2-one; the enantioselectivities were very poor, albeit comparable to those achieved in the reduction of olefins at that time. Rh complex of 1c reacted very slowly at room temperature under 1 atm hydrogen pressure with acetophenone (8% ee) and butan-2-one (2% ee) [75]. Negligible ee's (<1%) were scored using ligand 1f in the same hydrogenation [76].…”

Catalytic Asymmetric Hydrogenation Using Hydridorhodium(I) Diop Complexes [Diop = 2,3‐0‐Isopropylidene‐2,3‐Dihydroxy‐1,4‐Bis (Diphenylphosphino)Butane]

“…A second mechanism, which obviates the problem of the rhodium dependence, is the one outlined by Eqs. (6), (5) and (7): (6) k-, HRh(diop) + diop~HRh(dioPh (7) In this scheme, the diop dissociates during the process of olefin coordination. A steady state treatment for Rh(diop)(alkyI) yields the rate expression d[H2) _ k,k2(H2)(IA][Rhh (8) dt…”