Synthesis Of Chiral Diamine Ru Catalysts And Application In The Asymmetric Transfer Hydrogenation Of Benzils

In this article, we use (1R,2R)-1,2-diphenyl diamine (1R,2R-DPEN) as chiral ligands to get (Ru-DPEN-Ts) through selective sulfonadation and coordination with ruthenium. The synthesized catalyst(Ru-DPEN-Ts) was applied to asymmetric transfer hydrogenation of the asymmetric1,2-diketones. Using the asymmetric transfer hydrogenation of1-(3-methoxyphenyl)-2-phenylethane-1,2-dione as model reaction, the effects of solvent, the mole ratio of HCO2H/NEt3, temperature and S/C catalytic performance had been screened in details. Under the optimum reaction conditions:1-a, S/C=100, molar ratio of HCOOH/N(C2H5)3=2:1, none solvent,40℃,24h, alcohols with yield of94.2%, ee of98.8%and dr of29:1were formed in the asymmetric transfer hydrogenation of1-(3-methoxyphenyl)-2-phenylethane-1,2-dione. And the effects of different substituents and the substituents’ position (o, m, p-position) on catalytic reaction were also discussed. alcohols with yield of15-97%, ee of87.3-99%and dr of1.31:1-47.7:1were formed in the asymmetric transfer hydrogenation of eighteen different asymmetric1,2-diketones under the optimum reaction conditions. We found that the substituents’ position have a greater influence on the asymmetric transfer hydrogenation of1,2-dione.The mechanism of this reaction was also discussed in this article. We got the initial reaction mechanism by the kinetics of the asymmetric transfer hydrogenation of1-(3-methoxyphenyl)-2-phenylethane-1,2-dione.