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61.
A series of Cu-doped La-Ni intermetallic compounds(LaN5-xCux, x = 0-4) was studied. The bulk structure and surface composition of the samples were detected before and after they were used as catalyst for nitrobenzene hydrogennation. The catalytic properties of the intermetallic compounds depend on the surface region composition, especially on the valence of the metal ions. 相似文献
62.
Norma A. Cortez 《Tetrahedron letters》2007,48(25):4335-4338
Monosulfonamide ligands with heteroatom/heterocyclic systems were derived from trans-(1R,2R)-cyclohexane-1,2-diamine and complexed with [Ru(benzene)Cl2]2, [Cp∗RhCl2]2 in situ and used in the ATH of aromatic ketones with aqueous sodium formate as the hydrogen source. The chiral secondary alcohols were obtained with >93% enantioselectivity and >89% yield. Reduction in water was faster than in isopropanol/KOH. Addition of surfactants showed little or no effects. 相似文献
63.
Fumihiko Hasuni Katsunori Fukuoka Shuichi Adachi Yasumitsu Miyamoto Ichiro Okura 《Applied biochemistry and biotechnology》1996,56(3):341-344
Alanine synthesis by reductive amination of pyruvate was performed by the combination of NADH regeneration system and alanine
dehydrogenase (AlaDH). The conversion of pyruvate to alanine was 99% after 1 h. Leucine synthesis was also carried out by
the combination of NADH regeneration system and leucine dehydrogenase (LeuDH). The conversion of 4-methyl-2-oxovalerate to
leucine was 60% after 1.5 h. 相似文献
64.
Summary. A series of novel tridentate ligands with nitrogen and oxygen donor sites was synthesized starting from enantiomerically
pure (S)- and (R)-1-(pyridin-2-yl)ethylamine, the preparation and resolution of which was developed. The new optically active ligands were
tested as in situ catalysts together with Ru(PPh3)3Cl2 in the enantioselective transfer hydrogenation of acetophenone with isopropanol. The secondary amine ligand (S)-2,4-di-tert-butyl-6-(1-(pyridin-2-yl)ethylamino)methylphenol gave the best results with almost quantitative conversion and 47%ee.
Received August 17, 2001. Accepted August 27, 2001 相似文献
65.
A series of mononuclear organoruthenium complexes of the type [RuX(PPh3)2(L)] (X = Cl or Br; L = 2-(arylazo)phenolate ligand) have been synthesized from the reaction of five 2-(arylazo)phenol ligands with ruthenium(III) precursors, viz. [RuCl3(PPh3)3] and [RuBr3(PPh3)2(CH3OH)] in benzene under reflux. In all these reactions, the 2-(arylazo)phenolate ligand replaces one triphenylphosphine molecule, two chlorides or bromides and one methanol from the precursors leading to five-membered cyclometallated species. The 2-(arylazo)phenol ligands behave as dianionic tridentate C, N, O donors and coordinated to ruthenium by dissociation of the phenolic proton and the phenyl proton at the ortho position of the phenyl ring. The compositions of the complexes have been established by elemental analysis, magnetic susceptibility measurement, FT-IR, UV-Vis and EPR spectral data. These complexes are paramagnetic and shows intense d-d and charge transfer transitions in chloroform. The solution EPR spectrum of the complex 7 in dichloromethane at 77 K shows rhombic distortion around the ruthenium ion. The structural conformation of the complex 1 has been carried out by X-ray crystallography. The redox behavior of the complexes has been investigated by cyclic voltammetry and the potentials are observed with respect to the electronic nature of substituents (R) in the 2-(arylazo) phenolate ligands. These complexes catalyze transfer hydrogenation of benzophenone to benzhydrol with up to 99.5% in the presence of i-prOH/KOH. Further, these complexes have shown great promise in inhibiting the growth of both Gram +ve and Gram −ve bacteria, viz. Staphylococcus aureus NCIM 2079 and Escherichia coli NCIM 2065 and fungus Candida albicans NCIM 3102. 相似文献
66.
The hydrogenation of benzene and toluene was investigated over US-SSY, -Al2O3, and Ha1-MCM-41 supported platinum catalysts. The acidity of catalyst supports was measured by IR spectra of pyridine adsorption. On the Brönsted acid supported catalyst, both the hexacyclic saturation product and the pentacyclic one, the hydroisomerization product, were observed, and these two products were revealed to be primary reaction products. The two products were proposed to be formed competitively on Brönsted acid sites with carbonium ions as the reaction intermediate. By contrast, no hydroisomerization product was found on Lewis acid supported catalysts. It was inferred that the electron-deficient reaction intermediate formed on Lewis acids could not undertake any skeletal isomerization process to give a pentacyclic saturation product. 相似文献
67.
Katerina Liberkov Raymonde Touroude 《Journal of molecular catalysis. A, Chemical》2002,180(1-2):221-230
Selective hydrogenation of crotonaldehyde was performed on 5% Pt/SnO2 catalysts, in gaseous phase, at atmospheric pressure, at 353 K. Two types of catalyst were prepared using H2PtCl6 and Pt(NH3)4(NO3)2 as metallic precursors. Their performances were compared as a function of the reduction temperature and both catalysts were characterised by X-ray diffraction after different reduction treatments. Using the ex-chloride catalyst, the selectivity values to the unsaturated alcohol (UOL) resulted into a maximum of 45% while a selectivity as high as 70–77%, in 0–25% conversion range, was achieved by using ex-nitrate catalyst reduced at 443 K. The formation of Pt–Sn alloy on the metal particles of platinum was thought to be necessary to improve the activity and the selectivity on these catalysts. In the contrast, a presence of PtSn2 formed at a reduction temperature higher than 473 K led to a decrease of activity and selectivity. 相似文献
68.
Ping Yang Wei Zhang Yukou Du Xiaomei Wang 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):4-10
Platinum nanoparticle core-polyaryl ether trisacetic acid ammonium chloride dendrimer shell nanocomposites (Pt@Gn-NACl) were prepared and used as catalysts for hydrogenation of nitrobenzenes to anilines with molecular hydrogen under mild conditions. The as-prepared nanoparticles have mean particle size from 2.0 to 5.5 nm, depending on the molar ratio of the metal and the dendrimer. The Pt nanoparticles demonstrate near-monodisperse when the molar ratio of Pt and G3-NACl is below 30. The interaction among three carboxyl groups terminated at the dendron and the metallic core keeps the Pt nanoparticles from agglomerating. The colloidal solution of Pt nanoparticles stabilized by the dendrimer, in which the molar ratio of Pt/G3-NACl was less than 60, is stable without precipitation for several weeks. The dendrons attach to the metal core radially, and a substantial fraction of the surface of the metal nanoparticle is unpassivated and available for catalytic reactions. Turnover frequencies for the hydrogenation of nitrobenzenes to anilines change from 353 to 49 h−1 depending on the dendrimer generation and substrates. The dendrimer catalysts are stable during the catalytic hydrogenation process and can be recovered by centrifugation and reused. The results suggest the effectiveness of polyaryl ether trisacetic acid ammonium chloride dendrimer as a stabilizer for the preparation of Pt nanoparticle catalysts. 相似文献
69.
Bapurao B. Shingate Vandana S. Pore Rajesh G. Gonnade Mohan M. Bhadbhade 《Tetrahedron》2007,63(25):5622-5635
A stereoselective total synthesis of naturally occurring 20-epi cholanic acid derivatives has been realized, starting from readily available 16-dehydropregnenolone acetate. The key step of these syntheses involves an ionic hydrogenation of a C-20,22-ketene dithioacetal and deoxygenation of steroidal C-20 tert-alcohols, to set up the unnatural C(20R) configuration with 100% stereoselectivity. The unnatural C-22 aldehydes with C(20R) stereocenters thus obtained were elaborated to 20-epi cholanic acid derivatives. Two derivatives of 20-epi cholanic acid were synthesized and their structures have been confirmed by single crystal X-ray analysis. Catalytic hydrogenation of 16-dehydropregnenolone acetate and 16-dehydropregnenolone in ethanol affords C-5,C-16 tetrahydro products. Crystal structure analysis of one of these products revealed C-5α and C-17α configurations of the hydrogen atoms. 相似文献
70.
The partial hydrogenation of benzene to cyclohexene by nanoscale ruthenium catalysts in imidazolium ionic liquids 总被引:3,自引:0,他引:3
Silveira ET Umpierre AP Rossi LM Machado G Morais J Soares GV Baumvol IJ Teixeira SR Fichtner PF Dupont J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(15):3734-3740
The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF(6)), tetrafluoroborate (BMI.BF(4)) or trifluoromethane sulfonate (BMI.CF(3)SO(3)) ionic liquids with H(2) represents a simple and efficient method for the generation of Ru(0) nanoparticles. TEM analysis of these nanoparticles shows the formation of superstructures with diameters of approximately 57 nm that contain dispersed Ru(0) nanoparticles with diameters of 2.6+/-0.4 nm. These nanoparticles dispersed in the ionic liquids are efficient multiphase catalysts for the hydrogenation of alkenes and benzene under mild reaction conditions (4 atm, 75 degrees C). The ternary diagram (benzene/cyclohexene/BMI.PF(6)) indicated a maximum of 1 % cyclohexene concentration in BMI.PF(6), which is attained with 4 % benzene in the ionic phase. This solubility difference in the ionic liquid can be used for the extraction of cyclohexene during benzene hydrogenation by Ru catalysts suspended in BMI.PF(6). Selectivities of up to 39 % in cyclohexene can be attained at very low benzene conversion. Although the maximum yield of 2 % in cyclohexene is too low for technical applications, it represents a rare example of partial hydrogenation of benzene by soluble transition-metal nanoparticles. 相似文献