Enantioselective Synthesis of (S)-γ-Amino Alcohols by Ru/Rh/Ir Catalyzed Asymmetric Transfer Hydrogenation (ATH) with Tunable Chiral Tetraaza Ligands in Water
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(R/S)-γ-Amino alcohols are the key intermediates for the preparation of Fluoxetine, Atomoxetine, Nisoxetine and Duloxetine. In this paper, we describe an effective method to obtain (S)-γ-amino alcohols by Ru/Rh/Ir catalyzed asymmetric transfer hydrogenation with tunable chiral tetraaza ligands (L1–L5) in HCOONa/H2O system. The asymmetric reduction of acetophenone with [Ru(p-cymene)Cl2]2/L1 was utilized as the model ATH reaction to achieve the optimum reaction conditions. The best results were obtained by [RhCp∗Cl2]2/L5 affording the corresponding (S)-γ-amino alcohol with a good 97% conversion and an excellent > 99% ee in the reduction of 3-(N-methyl, N-carbethoxy)-1-phenylpropan-1-one. The influence of electronic and steric effects of the substituents in the ligands on the catalytic activities was also discussed.
(S)-γ-Amino alcohols were prepared via asymmetric transfer hydrogenation of β-amino ketones catalyzed by Ru/Rh/Ir complexes in situ with tunable chiral tetraaza ligands in HCOONa/H2O system. A moderate to excellent conversion (~ 99%) and enantioselectivity (~ 99%) were obtained with varied electronic and steric effects of the substituents on ligands and substrates.
KeywordsTetraaza ligand Asymmetric transfer hydrogenation β-Amino ketones γ-Amino alcohols HCOONa
We are grateful to the Zhejiang Provincial Natural Science Foundation of China (LY16B010003) and the Education Office of Zhejiang Province (Y200907718) for financial Support.
Compliance with Ethical Standards
Conflict of interest
The authors declare no conflict of interest.
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