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Diphosphine Ligands (diphosphine + ligand)

Distribution by Scientific Domains
Chemistry100%

Kinds of Diphosphine Ligands

  • chiral diphosphine ligand
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    Selected Abstracts

    Ferrocenyl-Aryl Based trans -Chelating Diphosphine Ligands: Synthesis, Molecular Structure and Application in Enantioselective Hydrogenation

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010
    Raffael Schuecker
    Abstract Potentially trans -chelating diphosphine ligands based on a ferrocenyl-aryl backbone were synthesised in a four-step sequence and the molecular structures in the solid state of two representatives were determined by X-ray diffraction. High throughput screening of these ligands in rhodium-, ruthenium- and iridium-mediated hydrogenations of a variety of alkenes and ketones revealed that these ligands can deliver high enantioselectivity for alkenes (up to 98% ee) but are less selective when ketones are used as the substrates. The coordination behaviour of one ligand in its square planar palladium and platinum dichloride complexes was studied by 31P,NMR and only trans -chelated complexes, together with oligomeric by-products, were observed. Reaction with the (p -cymene)ruthenium dichloride dimer, [RuCl2(p -cymene)]2, resulted in a mixture of diastereomeric complexes. [source]

    Axial Chirality Control by 2,4-Pentanediol for the Alternative Synthesis of C3*-TunePhos Chiral Diphosphine Ligands and Their Applications in Highly Enantioselective Ruthenium-Catalyzed Hydrogenation of ,-Keto Esters

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009
    Xianfeng Sun
    Abstract A highly efficient strategy for the synthesis of a series of C3*-TunePhos chiral diphosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for the ruthenium-catalyzed asymmetric hydrogenation of ,-keto esters. Up to 99% ee values were achieved for the enantioselective synthesis of ,-hydroxy acid derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules. [source]

    ChemInform Abstract: Axial Chirality Control by 2,4-Pentanediol for the Alternative Synthesis of C3*-TunePhos Chiral Diphosphine Ligands and Their Applications in Highly Enantioselective Ruthenium-Catalyzed Hydrogenation of ,-Keto Esters.

    CHEMINFORM, Issue 10 2010
    Xianfeng Sun
    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: Synthesis of Bisquinolone-Based Mono- and Diphosphine Ligands of the Aza-BINAP Type.

    CHEMINFORM, Issue 43 2008
    Nuzhat Arshad
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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: Preparation and Use of MeO-PEG-Supported Chiral Diphosphine Ligands.

    CHEMINFORM, Issue 43 2001
    Soluble Polymer-Supported Catalysts for Asymmetric Hydrogenation.
    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]

    Free radical polymerization of methyl methacrylate initiated by the diphosphine Mo(0) complexes

    APPLIED ORGANOMETALLIC CHEMISTRY, Issue 11 2006
    Ayfer Mente
    Abstract The polymerization of methyl methacrylate MMA catalyzed by [Mo(CO)4L2] [L2 = diphenylphosphinomethane (dppm), diphenylphosphinoethane (dppe) or diphenylphosphinopropane (dppp)] has been studied. The activity of these single-component catalysts depends on the length of the (CH2)n bridge of diphosphine ligand. Thus, the dppm derivative displays higher activity than dppe or dppp ligands. These complexes, as free radical initiators, afforded the methyl methacrylate polymerization in chlorinated solvents. The mechanism of the polymerization was discussed and a radical mechanism was proposed. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Ferrocenyl-Aryl Based trans -Chelating Diphosphine Ligands: Synthesis, Molecular Structure and Application in Enantioselective Hydrogenation

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010
    Raffael Schuecker
    Abstract Potentially trans -chelating diphosphine ligands based on a ferrocenyl-aryl backbone were synthesised in a four-step sequence and the molecular structures in the solid state of two representatives were determined by X-ray diffraction. High throughput screening of these ligands in rhodium-, ruthenium- and iridium-mediated hydrogenations of a variety of alkenes and ketones revealed that these ligands can deliver high enantioselectivity for alkenes (up to 98% ee) but are less selective when ketones are used as the substrates. The coordination behaviour of one ligand in its square planar palladium and platinum dichloride complexes was studied by 31P,NMR and only trans -chelated complexes, together with oligomeric by-products, were observed. Reaction with the (p -cymene)ruthenium dichloride dimer, [RuCl2(p -cymene)]2, resulted in a mixture of diastereomeric complexes. [source]

    Axial Chirality Control by 2,4-Pentanediol for the Alternative Synthesis of C3*-TunePhos Chiral Diphosphine Ligands and Their Applications in Highly Enantioselective Ruthenium-Catalyzed Hydrogenation of ,-Keto Esters

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009
    Xianfeng Sun
    Abstract A highly efficient strategy for the synthesis of a series of C3*-TunePhos chiral diphosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for the ruthenium-catalyzed asymmetric hydrogenation of ,-keto esters. Up to 99% ee values were achieved for the enantioselective synthesis of ,-hydroxy acid derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules. [source]

    A Practical Transition Metal-Free Aryl-Aryl Coupling Method: Arynes as Key Intermediates

    ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17-18 2007
    Frédéric
    Abstract Upon treatment of various aryllithium intermediates with 1,2-dibromobenzene or 1-bromo-2-iodobenzene, dissymmetrical ortho,ortho, -di-, tri- and even tetrasubstituted bromo- or iodobiaryls become readily available. The crucial steps in all these reactions were the nucleophilic addition of the organolithium precursor to a transient aryne species released from it by ,-elimination of a lithium halide and, stabilization of the resulting 2-biaryllithium intermediate by in situ transfer of bromine or iodine from the starting material. This straightforward transition metal-free access to biaryls allows the preparation of highly valuable halobiaryls on a gram scale in excellent yields. These precursors can be subsequently functionalized by highly regioselective halogen/metal permutations into a vast variety of target molecules. This was demonstrated in the synthesis of several mono- and diphosphine ligands. [source]

    Phosphine Ligands in the Palladium-Catalysed Methoxycarbonylation of Ethene: Insights into the Catalytic Cycle through an HP,NMR Spectroscopic Study

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2010
    Verónica de, la Fuente Dipl.-Chem.
    Abstract Novel cis -1,2-bis(di- tert -butyl-phosphinomethyl) carbocyclic ligands 6,9 have been prepared and the corresponding palladium complexes [Pd(O3SCH3)(L-L)][O3SCH3] (L- L=diphosphine) 32,35 synthesised and characterised by NMR spectroscopy and X-ray diffraction. These diphosphine ligands give very active catalysts for the palladium-catalysed methoxycarbonylation of ethene. The activity varies with the size of the carbocyclic backbone, ligands 7 and 9, containing four- and six-membered ring backbones giving more active systems. The acid used as co-catalyst has a strong influence on the activity, with excess trifluoroacetic acid affording the highest conversion, whereas excess methyl sulfonic acid inhibits the catalytic system. An in operando NMR spectroscopic mechanistic study has established the catalytic cycle and resting state of the catalyst under operating reaction conditions. Although the catalysis follows the hydride pathway, the resting state is shown to be the hydride precursor complex [Pd(O3SCH3)(L- L)][O3SCH3], which demonstrates that an isolable/detectable hydride complex is not a prerequisite for this mechanism. [source]