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Complex Catalyst (complex + catalyst)
Selected AbstractsChemInform Abstract: Nitrous Oxide Oxidation of Secondary and Benzylic Alcohols Using Ruthenium Complex Catalyst.CHEMINFORM, Issue 6 2002Kentaro Hashimoto Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Enantioselective Epoxidation of Non-Functionalized Alkenes Using an Urea,Hydrogen Peroxide Oxidant and a Dimeric Homochiral Mn(III)-Schiff Base Complex Catalyst.CHEMINFORM, Issue 30 2001Rukhsana I. Kureshy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Alkyne Hydroarylations with Chelating Dicarbene Palladium(II) Complex Catalysts: Improved and Unexpected Reactivity Patterns Disclosed Upon Additive Screening,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009Andrea Biffis Abstract Palladium(II) complexes with a ligand set made from a chelating N-heterocyclic dicarbene ligand and two weakly coordinating anions (generally introduced in situ upon addition of 2 equiv. of a suitable silver salt) were found to be very active and selective catalysts for the room-temperature hydroarylation of alkynes at low catalyst loading (0.1 mol-%). Moreover, the screening of various strong acids as reaction promoters revealed that both the strength of the acid and the coordinating ability of its conjugated base influence the catalytic performance. Most remarkably, the use of HBF4 together with a dicarbene Pd complex catalyst provides a dramatic change in the selectivity of the reaction, with the prevalent formation of a product stemming from the insertion of two molecules of alkyne into the aromatic C,H bond. The results presented herein highlight the fact that the dicarbene ligand, apart from stabilising the catalyst, is also able to enhance catalytic activity and, most notably, to steer the reaction selectivity towards novel products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] ChemInform Abstract: Reactivity of Chelating Dicarbene Metal Complex Catalysts.CHEMINFORM, Issue 35 2010H Bond Functionalization of Aromatic Heterocycles with Chelating Dicarbene Palladium(II), Part V. C, Platinum(II) Complexes. Abstract A combination of chelating dicarbene,Pd(II) complex [PdBr2(BBIM)] with AgBF4 catalyzes the addition of various hetarenes towards phenylpropiolate (II). [source] ChemInform Abstract: Modified Cinchona Alkaloid,Zinc Complex Catalysts: Enantioselective Monoacetylation of Glycerol Derivatives with Acetic Anhydride.CHEMINFORM, Issue 21 2010Shigeki Sano Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Alkyne Hydroarylations with Chelating Dicarbene Palladium(II) Complex Catalysts: Improved and Unexpected Reactivity Patterns Disclosed Upon Additive Screening,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2009Andrea Biffis Abstract Palladium(II) complexes with a ligand set made from a chelating N-heterocyclic dicarbene ligand and two weakly coordinating anions (generally introduced in situ upon addition of 2 equiv. of a suitable silver salt) were found to be very active and selective catalysts for the room-temperature hydroarylation of alkynes at low catalyst loading (0.1 mol-%). Moreover, the screening of various strong acids as reaction promoters revealed that both the strength of the acid and the coordinating ability of its conjugated base influence the catalytic performance. Most remarkably, the use of HBF4 together with a dicarbene Pd complex catalyst provides a dramatic change in the selectivity of the reaction, with the prevalent formation of a product stemming from the insertion of two molecules of alkyne into the aromatic C,H bond. The results presented herein highlight the fact that the dicarbene ligand, apart from stabilising the catalyst, is also able to enhance catalytic activity and, most notably, to steer the reaction selectivity towards novel products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Enantioselective Silylcyanation of Aldehydes and Ketones by a Titanium Catalyst Prepared from a Partially Hydrolyzed Titanium Alkoxide and a Schiff Base LigandADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Kazuhiko Yoshinaga Abstract In the presence of small amount (0.2,1.0 mol%) of a titanium complex catalyst prepared from a partially hydrolyzed titanium alkoxide and an optically active tridentate Schiff base ligand, the enantioselective silylcyanation of aldehydes and ketones proceeded in a short reaction time at room temperature to afford the corresponding optically active cyanohydrin derivatives in excellent chemical yield with high enantiomeric excess (86,97% ee). The results indicate that partially hydrolyzed titanium alkoxides are a promising titanium source for the preparation of efficient catalysts for asymmetric synthesis. [source] A new practical tritium labelling procedure using sodium borotritide and tetrakis(triphenylphosphine)palladium(0)JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2001Tohru Nagasaki Abstract A simple, mild and versatile new tritium (3H) labelling method on a micro scale using sodium borotritide (NaB3H4) and a transition,metal complex catalyst is described. 3H-labelled compounds were prepared effectively by 3H hydrogenolysis of appendant functional groups in target compounds. The appendant functional group such as bromo, iodo or sulfonate in various target compounds can be replaced by tritium (3H) in moderate yields. The new method was established by optimization of the reaction conditions and examination of its applicability using four types of model substrates in tracer runs. Then, various drug candidates and ligands for drug discovery were labelled with tritium on a micro scale. The specific radioactivity of the 3H-labelled compounds used for the studies on receptor binding ranged from 12 to 20 Ci/mmol. Copyright © 2001 John Wiley & Sons, Ltd. [source] Continuous process for production of hydrogenated nitrile butadiene rubber using a Kenics® KMX static mixer reactorAICHE JOURNAL, Issue 11 2009Chandra Mouli R. Madhuranthakam Abstract A continuous process for hydrogenating nitrile butadiene rubber (NBR) was developed and its performance was experimentally investigated. A Kenics® KMX static mixer (SM) is used in the process as a gas,liquid reactor in which gaseous hydrogen reacts with NBR in an organic solution catalyzed by an organometallic complex such as an osmium complex catalyst. The Kenics® KMX SM was designed with 24 mixing elements with 3.81 cm diameter and arranged such that the angle between two neighboring elements is 90°. The internal structure of each element is open blade with the blades being convexly curved. The dimensions of the SM reactor are: 3.81 cm ID 80 S and 123 cm length and was operated cocurrently with vertical upflow. The NBR solutions of different concentrations (0.418 and 0.837 mol/L with respect to [CC]) were hydrogenated by using different concentrations of the osmium catalyst solution at various residence times. The reactions were conducted at a constant temperature of 138°C and at a constant pressure of 3.5 MPa. From the experimental results, it is observed that a conversion and/or degree of hydrogenation above 95% was achieved in a single pass from the designed continuous process. This is the first continuous process for HNBR production that gives conversions above 95% till date. Optimum catalyst concentration for a given mean residence time to achieve conversions above 95% were obtained. Finally, a mechanistic model for the SM reactor performance with respect to hydrogenation of NBR was proposed and validated with the obtained experimental results. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Catalytic behavior of wool,Rh complex in asymmetric hydrogenation of 2-methyl furan,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 3-5 2003Man He Abstract A Wool,Rh complex was prepared by the reaction of wool with RhCl3·3H2O in ethanol solution, and was found to be useful as a chiral catalyst for the asymmetric hydrogenation of 2-methyl furan to (S)-(+)-2-methyl tetrahydrofuran at 28,°C and under atmospheric hydrogen pressure. When an appropriate Rh content in the Wool,Rh complex was selected, the yield and optical yield amounted to 53.7 and 76.9%, respectively, and the Wool,Rh complex catalyst could be reused several times without any noticeable loss in its optical catalytic activity. Wool is a very cheap natural biopolymer ligand, and Wool,Rh complex is very easy to prepare, and it is a very active, enantioselective and stable chiral catalyst for asymmetric hydrogenation of 2-methyl furan. Copyright © 2003 John Wiley & Sons, Ltd. [source] Preparation and use of polymer-supported chiral ruthenium complex catalystPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2001Jing-Xing Gao Abstract The chiral diiminodiphosphine ligand, [(R,R)-P2N2],has been prepared by the condensation of o -(diphenylphosphino)benzaldehyde and 1,2-diaminocyclohexane. [(R,R)-P2N2] was reduced with excess NaBH4 in refluxing ethanol to afford the corresponding diaminodiphosphine ligand [(R,R)-P2(NH)2]. The interaction of [(R,R)-P2(NH)2] with trans -RuCl2(DMSO)4 gave the chiral ruthenium complex [(R,R)-RuP2(NH)2] in 84% yield. The reaction of [(R,R)-RuP2(NH)2] with poly-(acrylic acid) using dicyclohexylcarbodiimine as the coupling agent, gave water soluble poly(acrylic acid salt)-supported chiral ruthenium complex [PAA-(R,R)-RuP2(NH)2]. These chiral ligands and ruthenium complexes have been fully characterized by microanalysis and IR, NMR spectroscopic methods. The polymer-bound ruthenium complex [PAA-(R,R)-RuP2(NH)2] as catalyst was used in asymmetric transfer hydrogenation of acetophenone in 2-propanol, producing the 1-phenylethanol in 95% yield and 96% ee. The catalyst was reused twice with some loss of activity and enantioselectivity. Copyright © 2001 John Wiley & Sons, Ltd. [source] The influence of halogen anions and N-ligands in CuXn/N-ligands on the catalytic performance in oxidative carbonylation of methanolAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2010Wanling Mo Abstract The catalytic properties of CuXn/N-ligands (X = Cl, Br and I; n = 1 or 2) in oxidative carbonylation of methanol were investigated. It was found that the interaction of halogen anions, N-ligands and Cu (I) affected the catalytic performance of copper complex catalyst in the reaction, especially iodide anion and 1,10-phenanthroline (Phen). When CuI/Phen was used as a catalyst, the conversion of methanol was 42.6%, the selectivity to dimethyl carbonate was 99.2% and the TOF was 13.1 h,1 at an optimized conditions: CuI/Phen 0.2 mol l,1, 120 °C, 2 h, 2.4 MPa, PCO/PO2 = 2:1. Compared with the plain CuI catalyst, the catalytic activity of CuI/Phen increased about 36 times. When CuI/Phen catalyst was immobilized on polystyrene (PS), the heterogenized catalyst, CuI/Phen,NH,PS, also exhibited very high catalytic activity in oxidative carbonylation. The CuI/Phen,NH,PS catalyst remained its high catalytic activity even after seven recycles. The average weight loss of CuI/Phen,NH,PS after reaction was less than 1.0%, and the leaching of copper was only about 0.15% in each recycling test. Copyright © 2010 John Wiley & Sons, Ltd. [source] Direct Allylation of Aldimines Catalyzed by C2 -Symmetric N,N, -Dioxide,ScIII Complexes: Highly Enantioselective Synthesis of Homoallylic AminesCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2008Xing Li The first catalytic asymmetric three-component allylation of aldimines has been developed. In the presence of L -ramipril acid-oriented N,N, -dioxide,ScIII complex catalyst, a range of homoallylic amines were formed in excellent enantioselectivities (up to 97,% ee) with good yields from corresponding aldehydes, 2-aminophenol and allyltributyltin (see scheme). [source] Ruthenium (II) complexes immobilized on swellable polyacrylate matrices: Synthesis and catalytic applicationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Z. S. Liu Abstract RuH2(PPh3)4 has been immobilized on swellable polyacrylate matrices to provide heterogenized carboxylate-derivatives. These swellable polymer supported ruthenium (II) complex catalysts have been used in the transfer hydrogenation of aldehydes. Hydrogen donors are formate salt, cyclohexanol, and benzyl alcohol. The catalysts exhibit good activity for hydrogen transfer reduction of aldehydes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Polymerization of ,-pinene with Schiff-base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(,-pinene) at high temperature with high productivityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007Peng Yu Abstract A series of easily accessible and stable Schiff-base nickel complexes (complex 1,4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight ,-pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of ,-pinene (Mn , 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 107 g poly,-pinene/mol of Ni. 1H NMR analyses showed that the obtained ,-pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff-base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739,3746, 2007 [source] | |||||||||||||