Studies on Asymmetric Hydrogenations of Acetophenone and Its Derivatives Catalyzed by Ru-Rh/γ-Al2O3 Catalyst and Selective Hydrogenation of α, β-unsaturated Carbonyl Compounds over Ru/γ-Al2O3
|Keywords||Ruthenium Rhodium Catalytic Aromatic ketones Benzalacetone Cinnamic aldehyde Asymmetric hydrogenation Selective hydrogenation|
Homogeneous catalysis with its high catalytic activity and high selectivity, mild reaction conditions for the features, but the separation of the catalyst and the product of a long-term problem plagued the people. Heterogeneous catalysis while having easily separated from the product, the advantages of simple operation, but the catalytic activity and selectivity is low. Asymmetric hydrogenation of prochiral ketones to chiral alcohols generated and unsaturated aldehydes, ketones hydrogenation of unsaturated alcohols are synthetic drugs, important intermediates of fine chemicals, developed to combine the advantages of homogeneous and heterogeneous catalysis the catalyst - catalytic performance is good, it is also easily separated from the product and recycled catalyst, to open up a environmentally friendly green chemical synthesis of chiral compounds for new ways to more and more people's attention. This reduction in the temperature in the aqueous formaldehyde solution was prepared using triphenylphosphine as a stabilizer bimetallic ruthenium - rhodium and single component rhodium, ruthenium catalyst, (1S, 2S) -1,2 - diphenyl-ethylenediamine ( DPEN) as a modifier of acetophenone and its derivatives and its homologues for heterogeneous asymmetric catalytic hydrogenation, ruthenium - rhodium bimetallic catalyst showed higher than rhodium or ruthenium catalytic activity, showing a synergistic catalysis. In the catalytic reaction, the chiral modifier DPEN chiral induction only, and can significantly speed up the reaction rate. Under the optimum reaction conditions, acetophenone, ethyl - phenyl ketone and isopropyl ketone conversion rate of 92%, to generate (R) - configuration of the product e. e. Values ??were 79.6%, 81.2% and 81.4% We further studied using phosphine ligand as a stabilizer supported on an inorganic carrier a different ruthenium catalyst, racemic 1,2 - diphenyl-ethylenediamine (DPEN) and some aliphatic, alicyclic and aromatic diamines as promoter, were examined for their base in isopropanol solution of benzyl acetone and catalytic selective reduction of cinnamic aldehyde C = O generating reaction of the unsaturated alcohol. The results showed that DPEN as additives, with triphenylphosphine (TPP) as a stabilizer prepared ruthenium catalyst Ru/2TPP-γ-Al 2 O 3 , Whether to generate catalytic activity or selectivity of the unsaturated alcohol are highest, at a temperature of 35 ℃, P H2 = 4 MPa, c (KOH) = 0.04 mol / L, the reaction 3h, benzylidene acetone conversion rate close to 100%, the selectivity of the hydrogenation of carbonyl gt; 99%. In the selective hydrogenation of cinnamaldehyde, in the 100 ℃, P H2 = 5 MPa, c (KOH) = 0.04 mol / L, the reaction time 6h, cinnamic aldehyde conversion was 96.0 %, the selectivity of the hydrogenation of carbonyl has reached 94.3%. Additives found diamine synergy KOH and greatly improved catalytic activity and the C = O selective hydrogenation.