Synthesis And Application In The Asymmetric Hydrogenation Of Carbonyl Compounds Of Chiral Diamine

The asymmetric hydrogenation of prochiral ketones is one of the most efficient methods to product enantiomerically enriched secondary alcohols. Recently, asymmetric hydrogenation catalysed by organometallic complex has become one of the most attractive field in the asymmetric catalytic synthesis. In contrast to the fruitful results of the asymmetric hydrogenation of functionalized ketones catalyzed by organometallic complexes, only limited examples have been reported for simple ketones because such substrates lack heteroatoms that enable the substrate to anchor strongly to the metal center. The chiral aromatic alcohol, product of the asymmetric hydrogenation of the corresponding ketones, is of great importance to the synthesis of medicines and fine chemicals. The develepment of the catalyst with high catalytic activity and great enantioselectivity plays an important role in the asymmetric catalysis. Noroyi reported the Ru-BINAP-chiral diamine-KOH catalytic symtem, which showed excellent catalytic activity and high enantioselectivity under mild reaction condition(room temperature and low pressure) and high moral ratio of substrate to catalyst. This attracted the great attention of the chemists. Professor Albert S. C. Chan and co-workers have developed a chiral dipyridylphosphine ligand 2,2',6,6'-tetramethoxy-bis(dephenylphosphino)-3,3'-bipyridine(P-Phos). It is of high interest to note that the Ru(C6H6)(P-Phos)Cl2 catalyst is air-stable even in solution. The P-Phos is the only one that is air-stable in the structurally analogous diphosphine ligand and exists potential of the practical application in reactions of industrial interest, In this paper, we devote to synthesize new catalysts for the hydrogenation of aromtic ketones. The main work includes:1: [RuC12{(S)-P-Phos}(S)-DAIPEN] was synthesized and characterized by 31PNMR.The catalytic activity of [RuC12{(S)-P-Phos} (S)-DAIPEN] was studied for the hydrogenation of aromatic ketones in the presence of KOH and 2-Propanol. The results indicated that [RuC12{(S)-P-Phos}(S)-DAIPEN] was a good catalyst for the hydrogenation of simple aromatic ketones and the ortho-sustituted acetophenones had much lower activity. Up to 94.0% e.e. was obtained in the hydrogenation of simple aromatic ketones catalyzed by [RuC12{(S)-P- Phos}(S)-DAIPEN] under the mild conditions.2: The enantioselective hydrogenation of benzalacetone catalyzed by chiral diamine-modified Ru-TPP/γ-Al2O3 (TPP: triphenylphosphine) was studied. The effect of chiral diamine, such as (S,S)-DPEN [(1S,2S)- 1,2-diphenyl- 1,2-ethylenediamine],(S)-DAIPEN[(2S)-1,1–di(4-anisyl)-2-isopropyl-1,2-ethylenediamine],(8S,9S)-9-amino(9-deoxy)dihydrocinchonidine and (1S,2S)-1,2-diamino- cyclohexane on the hydrogenation was investigated. The results showed that (S,S)-DPEN could efficiently improved the activity and selectivity of benzalacetone hydrogenation. Under the optimum reaction conditions, 40°C, 4.0 MPa in K2CO3/i-PrOH+H2O solution, (S,S)-DPEN as the chiral modifier, the conversion and the selectivity toward the unsaturated alcohol was reached 99% and 98%,respectively, and the ee value of unsaturated alcohol wasup to 47%.3:According to literature, we prepared the chiral amino alcohols and chiral diamine successfully from proline and valine through five steps including esterification, Grignard addition ,protection of amino group, nitrine reaction and Pd/C catlyzed hydrogenolysis .