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Spectrometric elucidation of intermediates in asymmetric transfer hydrogenation of ketones catalyzed by complex of ruthenium (II) and isosorbide-based ligand

The recorded high resolution mass spectra when following the typical protocol for the asymmetric transfer hydrogenation of acetophenone confirmed an involvement of the active complex mono-hydride ruthenium in the catalytic circle. As a result, high resolution mass spectra in research on catalytic mechanism can be therefore employed as an alternative tool for studying catalytic mechanism. | Vietnam Journal of Chemistry, International Edition, 54(4): 471-476, 2016 DOI: 10.15625/0866-7144.2016-00349 Spectrometric elucidation of intermediates in asymmetric transfer hydrogenation of ketones catalyzed by complex of ruthenium (II) and isosorbide-based ligand Huynh Khanh Duy Faculty of Chemical Engineering, Ho Chi Minh City University of Technology Received 7 June 2016; Accepted for publication 12 August 2016 Abstract The use of electrospray ionization mass spectrometry for the detection of the intermediate species involved in the ruthenium(II)/β-amino-alcohol derived from isosorbide reduction of ketones to alcohols is described. The formation of active complex of ruthenium (II) for catalyzing the asymmetric transfer hydrogenation of ketones was observed from 1 H-NMR spectra. From high resolution mass spectra, peaks of group of isotopes allow to conform the existence of active species of ruthenium (II) in the presence of isosorbide-based ligand. The recorded high resolution mass spectra when following the typical protocol for the asymmetric transfer hydrogenation of acetophenone confirmed an involvement of the active complex mono-hydride ruthenium in the catalytic circle. As a result, high resolution mass spectra in research on catalytic mechanism can be therefore employed as an alternative tool for studying catalytic mechanism. Keywords. Asymmetric catalysis, isosorbide, asymmetric transfer hydrogenation. 1. INTRODUCTION Isosorbide 1, also known as (3R,3aR,6S,6aR)hexahydrofuro[ 3,2-b]furan-3,6-diol, is a renewable, and commercially available chiral carbohydrate. Isosorbide is basically two fused tetrahydrofuran rings having the cis-arrangement at the ring junction, giving a wedge-shaped molecule [1]. The compound bears two hydroxyl groups, one at C6 having the exoorientation with respect to the wedge-shaped molecule, and the other at C3 having the endoorientation, which makes possible the intramolecular hydrogen bonding with the oxygen atom of .