Asymmetric transfer hydrogenation of aromatic ketones with the ruthenium(II) catalyst derived from C2 symmetric N,N′-bis[(1S)-1-benzyl-2-O-(diphenylphosphinite)ethyl]ethanediamide

Asymmetric transfer hydrogenation of ketones with chiral molecular catalysts is realized to be one of the most magnificent tools to access chiral alcohols in organic synthesis. A new chiral phosphinite compound N,N′-bis[(1S)-1-benzyl-2-O-(diphenylphosphinite)ethyl]ethanediamide (1), has been synthesized by the reaction of chlorodiphenylphosphine with N,N′-bis[(1S)-1-benzyl-2-hydroxyethyl]ethanediamide under argon atmosphere. The oxidation of 1 with aqueous hydrogen peroxide, elemental sulfur or grey selenium in toluene gave the corresponding oxide 1a, sulfide 1b and selenide 1c, respectively. Pd, Pt and Ru complexes were obtained by the reaction of 1 with [MCl2(cod)] (M: Pd 1d, Pt 1e) and [Ru(p-cymene)Cl2]21f, respectively. All these new complexes were characterized by using NMR, FT-IR spectroscopies and microanalysis. Additionally, as a demonstration of their catalytic reactivity, the ruthenium complex 1f was tested as catalyst in the asymmetric transfer hydrogenation reactions of acetophenone derivatives with iPrOH was also investigated.

Herein, we report synthesis and characterization of a new chiral phosphinite compound N,N′-bis[(1S)-1-benzyl-2-O-(diphenylphosphinite)-ethyl]ethanediamide 1 and its corresponding oxidized derivatives and Pd(II), Pt(II) and Ru(II) complexes. The use of chiral Ru(II) complex 1f as a catalyst in the transfer hydrogenation of aromatic ketones gives secondary alcohols with high yields and TOF values under moderate conditions.Figure optionsDownload as PowerPoint slide