Chiral C2-symmetric η6-p-cymene-Ru(II)-phosphinite complexes: Synthesis and catalytic activity in asymmetric reduction of aromatic, methyl alkyl and alkyl/aryl ketones
Abstract Chiral C2-symmetric bis(phosphinite) ligands and their binuclearruthenium(II) complexes have been synthesized and used as catalysts in the ruthenium-catalyzed asymmetrictransferhydrogenation of aromatic, methyl alkyl and alkyl/aryl ketones using 2-propanol as both the hydrogen source and solvent in the presence of KOH. Under optimized conditions, all complexes showed high catalytic activity
Coordination with RuCl2(PPh3)dppb gave ruthenium(II) N-heterocyclic complexes 4b–d. The structure of complex 4b was fully illuminated by X-ray crystallography. The steric environment of these chiral ruthenium complexes 4b–d was evaluated in asymmetric transfer hydrogenation (ATH) of prochiral ketones in the presence of NaOiPr by using 2-propanol as the hydrogen source and solvent. The resultant catalytic
从光学纯的氨基酸开始合成了一组新的基于喹唑啉的手性配体。与RuCl 2(PPh 3)dppb配位得到钌(II)N-杂环配合物4b–d。配合物4b的结构通过X射线晶体学被完全照亮。通过使用2-丙醇作为氢源和溶剂,在NaO i Pr存在的情况下,在手性酮的不对称转移氢化(ATH)中评估了这些手性钌配合物4b-d的空间环境。所得的催化体系可以实现非常好的对映选择性(高达91%)和高产率(高达99%)。
A new class of well-defined ruthenium catalysts for enantioselective transfer hydrogenation of various ketones
ruthenium complexes were described in detail. The ruthenium complexes proved to be highlyefficientcatalysts for the enantioselectivehydrogenation of ketones, affording products up to 99% ee. The results showed that the corresponding chiral alcohols could be obtained with high activity and excellent enantioselectivities at the desired temperature. (2S)-1-benzyl[(1S)-1-(naphthalen-1-yl)ethyl]amino}
Catalysts for the asymmetric transfer hydrogenation of various ketones from [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] and [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2
-imidazol-3-ium chloride] with [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2, in the presence of KOH/isoPrOH, has been found to generate catalysts that are capable of enantioselectively reducing alkyl, aryl ketones to the corresponding (R)-alcohols. Under optimized conditions, when the catalysts were applied to the asymmetric transfer hydrogenation, we obtained the secondary alcohol
4-formylphenylboronic acid with chiral amines. The boron containing structures have been found as stable compounds due to the presence of covalent B–O bonds and thus could be handled in laboratory environment. They were characterized by 1H NMR and FT-IR spectroscopy and elemental analysis and they were used as catalyst in the transfer hydrogenation of ketones to the related alcohol derivatives with high conversions