Synthesis Of New Ruthenium-Phosphine Complexes And Studies On Their Catalytic Properties In The Hydrogenation Of Simple Aromatic Ketones

Recently, homogeneous asymmetric hydrogenation with organometallic complex has become one of the most attractive field in the asymmetric catalytic synthesis. 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 development of the catalyst with high catalytic activity and great enantioselectivity plays an important role in the asymmetric catalysis. In 1995, R. Noroyi reported the [RuCl2(phosphine)3]-chiral diamine-KOH catalytic symtem, which showed excellent catalytic activity and high enantioselectivity under mild reaction conditions(room temperature and low pressure) and high moral ratio of substrate to catalyst. This attracted the great attention of the chemists. In this paper, we devote to synthesize new catalysts for the hydrogenation of aromtic ketones, The main work includes:1. The monophosphine ligand Dmpp ((Dmpp =4(2,6-Dimethoxy-pyridyl)diph enylphosphine) , chiral biphosphine ligand (R)-P-Phos(2,2',6,6'-tetramethoxy-4,4'-bis(diphenylphosphino)-3,3'-bipy-ridine) and the corresponding complexes, such as [RuCl2(Dmpp)2en](en=NH2CH2CH2NH2),[RuCl2(Dmpp)2(S,S)-DPEN]((S,S)-DP EN=(S,S)-1,2-diphenylethylenediamine), [RuCl2{(R)-P-Phos}(R,R)-DPEN], [RuCl2{(R)-P-Phos}en], [RuCl2{(R)-P-Phos}(S,S)-DPEN], were synthesized and characterized by 1H NMR and 1P{H}NMR.2. The catalytic activity of [RuCl2(Dmpp)2en] was studied for the hydrogenat-ion of aromatic ketones in the presence of KOH and 2-Propanol. The results indicated that [RuCl2(Dmpp)2en] was a good catalyst for the hydrogenation of simple aromatic ketones and the ortho-sustituted acetophenones had much lower activity.3. The catalytic properties of chiral diamine monophosphine-ruthenium complex [RuCl2(Dmpp)2(S,S)-DPEN] have been investigated in the hydrogenation of acetophenone and up to 55.5% e.e. was attained.4. Up to 86.6% e.e. was obtained in the hydrogenation of simple aromatic ketones catalyzed by [RuCl2{(R)-P-Phos}(R,R)-DPEN] under the mild conditions and the high molar ratio of substrate to catalyst. For the complexes containing different diamine, the order of catalytic activity was as following: [RuCl2{(R)-P-Phos}(R,R-DPEN)] > [RuCl2{(R)-P-Phos}(S,S)-DPEN]>[RuCl2{(R)-P-Phos}en].The configuration and e.e. value of hydrogenated products were controlled by the chirality of both diamine and diphosphine.5. On studying the effect of solvent, we, for the first time, found that the n-butyl alcohol is the best solvent for the hydrogenation of simple aromatic ketones catalyzed by [RuCl2{(R)-P-Phos}(R,R)-DPEN]. In the detail, the reaction activity increased from ethanol to n-propanol to n-butyl alcohol. Howere, the reaction activity decreased when n-hexanol and n-octanol were used as solvent, alcohol containing the same carbon atoms, the order of the catalytic activity was: primary alcohol>second alcohol>third alcohol.