129171-92-2Relevant articles and documents
A boron analog of DIOP: Synthesis and properties
Borner,Ward,Kortus,Kagan
, p. 2219 - 2228 (1993)
A rhodium complex of a boron analog of DIOP, which is a model for a tailored bimetallic catalyst possessing dual functions, is an active catalyst for hydrogenation and hydrosilylation.
Poly(3-hydroxybutyrate)-depolymerase from Pseudomonas lemoignei: Catalysis of esterifications in organic media
Kumar,Gross,Jendrossek
, p. 7800 - 7806 (2000)
Lipase catalysis in nonaqueous media is recognized as a powerful tool in organic and more recently polymer synthesis. Even though none of the currently known polyhydroxyalkanoate (PHA) depolymerases have lipase activity, they do have a catalytic center that resembles that of lipases. Motivated by the above, the potential of using the poly(3-hydroxybutyrate), PHB, depolymerase from Psuedomonas lemoignei in organic media to catalyze ester-forming reactions was investigated. The effect of different organic solvents (benzene-d6, cyclohexane-d12, and acetonitrile-d3) on the activity of the PHB-depolymerase toward propylation of L-lactide was studied. A significant difference in the catalytic rate was observed as a function of solvent polarity. The selectivity of the PHB-depolymerase (P. lemoignei) to catalyze the propylation of a series of different lactones including ε-caprolactone, δ-butyrolactone, γ-butyrolactone, and D, L, meso, and racemic lactides has been studied with the PHB-depolymerase (P. lemoignei) in organic solvents. Important differences in the reactivity of these lactones, as well as selective hydrolysis of stereochemically different linear lactic acid dimers, were observed. Moreover, the ability of the PHB-depolymerase to catalyze the solventless polymerization of ε-caprolactone and trimethylene carbonate was investigated.
Enantioselective hydrogenation of pyruvates over polymer-stabilized and supported platinum nanoclusters
Zuo, Xiaobin,Liu, Hanfan,Guo, Dawei,Yang, Xiaozhen
, p. 7787 - 7804 (1999)
The cinchonidine-modified enantioselective hydrogenation of pyruvates has been studied over polyvinylpyrrolidone-stabilized platinum (PVP-Pt) and the corresponding alumina-supported platinum (Al2O3-Pt) clusters. It is shown that the catalysts with particle size less than 2.0 nm demonstrate >90% enantioselectivity in favor of (R)-lactates. The solvent effect is similar to that over the conventional supported platinum catalyst except for tetrahydrofuran. These colloidal and supported clusters are stable with no obvious loss of activity and enantioselectivity even after 18 months standing in air at room temperature. Molecular mechanics calculations of the modifier- reactant interaction on the platinum surface suggest that it is possible to obtain good enantioselectivity on the small clusters.
Synthesis and characterization of chiral mono N-heterocyclic carbene-substituted rhodium complexes and their catalytic properties in hydrosilylation reactions
Steinbeck, Martin,Frey, Guido D.,Schoeller, Wolfgang W.,Herrmann, Wolfgang A.
scheme or table, p. 3945 - 3954 (2011/12/22)
Different chiral mono-substituted N-heterocyclic carbene complexes of rhodium were prepared, starting from [Rh(COD)Cl]2 (COD = cyclooctadiene) by addition of free N-heterocyclic carbenes (NHC), or an in-situ deprotonation of the corresponding iminium salt. All new complexes were characterized by spectroscopy methods. In addition, the structures of chloro(η4-1,5-cyclooctadiene)(1,3-di-[(1R,2R,3R,5S)-2,6, 6-trimethylbicyclo[3.1.1]hept-3-yl] imidazolin-2-ylidene)rhodium(I) (5a), chloro(η4-1,5-cyclooctadiene)(1,3-di-[(1R,2S,5R) -2-isopropyl-5-menthylcyclohex-1-yl]imidazol-2-ylidene)rhodium(I) (5b) and chloro(η4-1,5-cyclooctadiene)(1,3-di-[(2R,4S,5S) -2-methyl-4-phenyl-1,3-dioxacyclohex-5-yl]imidazolin-2-ylidene)rhodium(I) (5i) were analyzed by DFT-calculations. The enantioselective hydrosilylation of acetophenone, ethylpyruvate and n-propylpyruvate with diphenylsilane and hydrolysis was carried out with chiral C2-symmetrical mono-substituted N-heterocyclic carbene rhodium complexes giving for the first time an enantioselective excess of up to 74% ee in the case of the n-propylpyruvate.
