The Preparation Of Immobilizable Binaphthyl Derivatives-Ruthenium Complex Catalysts And Research On Its Catalytic Asymmetric Hydrogenation

Optically pure 2,2'-dihydroxy-1,1'-binaphthyl(BINOL) and its derivatives are classical axially chiral ligand which used extensively in homogeneous asymmetric catalytic hydrogenation. Although homogeneous asymmetric catalysts have some advantages such as high activity and enantioselectivity, they are not widely used in industry, because of difficulties of separating and recycling. To overcome these drawbacks, immobilization of BINOL's derives has been attracted attention very much in recent years.In this work, firstly, BINOL had been prepared by the oxidative coupling of 2-naphthol with FeCl₃/Al₂O₃ as catalyst and aerial oxygen as oxidant. The optimum yield condition were obtained by single factor experiments. At the same time, the separation and determination of crude BINOL had been studied by reversed-phase HPLC for the first time. Under the selected conditions of the chromatographic operation, BINOL, 2-naphthol and other impurities were excellently separated each other.Secondly, L-proline was used as chiral separation agent to resolve racemic BINOL into its optically pure (R)-and (S)-enantiomers. The effect of the resolution solvent, solvent dosage, crystallization temperature and crystallization time had been firstly systemically investigated. Under the optimized process conditions, highly optical pure BIAOL could be plentifully got, in order to prepare BINOL's derivatives as chiral ligands for asymmetric hydrogenation.Finally, Using optically pure BINOL as raw material, immobilized catalyst(BINAPO-Ru/HPA/Al₂O₃) was prepared by anchoring BINAPO-Ru on the heteropolyacid(HPA) for the first time. Based on sigle factor experiments, the optimized process conditions of synthesis of (S)-(+)-ethyl-3-hydroxybutyrate was obtained. The results show that the activity and enantioselectivity of immobilized catalyst were better than those of homogeneous catalyst in the asymmetric hydrogenation ofβ-keto esters; and that the immobilized catalyst still kept good activity after fifth recycling under the optimum conditions.