Amino Alcohol Coordination in Ruthenium(II)-Catalysed Asymmetric Transfer Hydrogenation of Ketones

Abstract

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A Facile Synthesis of a Wide Variety of Cationic Ruthenium Hydrido-Arene Complexes of binap (=1,1′-Binaphthalene-2,2′-diylbis(diphenylphosphane)) and MeObiphep (=6,6′-Dimethoxybiphenyl-2,2′-diylbis(diphenylphosphane))

“…In many cases the Ru-catalyst precursor contains an h 6 -arene ligand [4] [7] [11] [14 ± 16], together with nitrogen or phosphorus ligands. These complexes can be prepared by allowing commercially available Cl-bridged h 6 -arene (e.g., p-cymene) Ruthenium complexes to react with monodentate or bidentate N-or P-donors to afford catalyst precursors in good yield [17a] (see Scheme 1).…”

Solid-Phase Synthesis of Homogeneous Ruthenium Catalysts on Silica for the Continuous Asymmetric Transfer Hydrogenation Reaction

“…Monitoring the reaction showed that the reaction rate is initially almost independent of the substrate concentration (Figure 1). At higher conversions, the rate becomes dependent of the substrate concentration, which was also observed for the homogeneously catalyzed analogue 5…”

“…All ruthenium amino alcohol complexes showed good activity and significant enantioselectivity in the transfer‐hydrogenation of acetophenone, whereas diamine 8 induced hardly any ee (Table 3). Surprisingly, catalyst Ru( 5 ), with 58 % ee , was far more selective than the homogeneous analogue for which an ee of 20 % had been reported 5, 28. We suggest that higher catalyst stability due to immobilization can give rise to improved catalyst selectivity, especially for complexes that are intrinsically less stable due to steric restrictions.…”

Catalytic Asymmetric Transfer Hydrogenation of Ketones Using [Ru(p-cymene)Cl2]2 with Chiral Amino Alcohol Ligands

“…Wills et al [26][27][28][29] have investigated transfer hydrogenation of various ketones using (1R,2S)-cis-1-aminoindan-2-ol as a ligand (Scheme 1, B) with high asymmetric induction (70-98%). Van Leeuwen et al [30,31] have investigated various substituted amino ethanol and norephedrine based ligands and tetradentate ligands for transfer hydrogenation of ketones. Best results (88% conversion of acetophenone with 95% ee) were obtained using (1R,2S)-N-benzyl-norephedrine as a ligand (Scheme 1, C).…”