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Chiral Phosphorus Ligands (chiral + phosphorus_ligand)

Distribution by Scientific Domains
Chemistry100%
Distribution within Chemistry
Organic Chemistry60%
General & Introductory Chemistry40%

Selected Abstracts

A Modular Approach to a New Class of Monodentate Chiral Phosphorus Ligands and Their Application in Enantioselective Copper-Catalysed Conjugate Additions of Diethylzinc to Cyclohexenone

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2004
Chiara Monti
Abstract A new family of chiral phosphorus ligands (5) for use in enantioselective catalysis have been synthesised. The ligands contain the electron-poor bis(sulfonyl)diazaphospholidine moiety and possess a highly modular structure which is well suited to the synthesis of a library. A small library (23 members) of ligands 5 was prepared and tested in the enantioselective copper-catalysed conjugate addition of diethylzinc to cyclohexenone. Complete conversions were obtained with enantiomeric excesses (ee) of up to 75%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Developing a New Class of Axial Chiral Phosphorus Ligands: Preparation and Characterization of Enantiopure Atropisomeric Phosphinines

CHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2008
Christian Müller Dr.
Abstract Both enantiomers of the first atropisomeric phosphinine (1) have been isolated by using analytical HPLC on a chiral stationary phase. The enrichment of one enantiomer and a subsequent investigation into its racemization kinetics revealed a barrier for internal rotation of ,=(109.5±0.5),kJ,mol,1, which is in excellent agreement with the theoretically predicted value of ,=116,kJ,mol,1. Further analysis with UV and circular dichroism spectroscopies and density functional theory calculations led to the determination and assignment of the absolute configurations of both enantiomers. These results are the basis for future investigations into this new class of axially chiral phosphinine-based ligands and their possible applications in asymmetric homogeneous catalysis. [source]

A Modular Approach to a New Class of Monodentate Chiral Phosphorus Ligands and Their Application in Enantioselective Copper-Catalysed Conjugate Additions of Diethylzinc to Cyclohexenone

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2004
Chiara Monti
Abstract A new family of chiral phosphorus ligands (5) for use in enantioselective catalysis have been synthesised. The ligands contain the electron-poor bis(sulfonyl)diazaphospholidine moiety and possess a highly modular structure which is well suited to the synthesis of a library. A small library (23 members) of ligands 5 was prepared and tested in the enantioselective copper-catalysed conjugate addition of diethylzinc to cyclohexenone. Complete conversions were obtained with enantiomeric excesses (ee) of up to 75%. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Asymmetric Hydrogenations (Nobel Lecture 2001)

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2003
William
Abstract The start of the development of catalysts for asymmetric hydrogenation was the concept of replacing the triphenylphosphane ligand of the Wilkinson catalyst with a chiral ligand. With the new catalysts, it should be possible to hydrogenate prochiral olefins. Knowles and his co-workers were convinced that the phosphorus atom played a central role in this selectivity, as only chiral phosphorus ligands such as (R,R)-DIPAMP, whose stereogenic center lies directly on the phosphorus atom, lead to high enantiomeric excesses when used as catalysts in asymmetric hydrogenation reactions. This hypothesis was disproven by the development of ligands with chiral carbon backbones. Although the exact mechanism of action of the phosphane ligands is not incontrovertibly determined to this day, they provide a simple entry to a large number of chiral compounds. [source]

Synthesis of Enantiomerically Pure 1,2,3,4-Tetrahydro-,-carbolines and N -Acyl-1-aryl Ethylamines by Rhodium-Catalyzed Hydrogenation

CHEMISTRY - AN ASIAN JOURNAL, Issue 7 2008
Stephan Enthaler Dr.
Abstract The rhodium-catalyzed asymmetric hydrogenation of different enamides, in particular, dihydro-,-carboline derivates, was investigated in the presence of chiral phosphorus ligands. Enantioselectivities of up to 99,%,ee were obtained after ligand screening and optimization of the reaction conditions. The scope and limitation of the catalysts were shown in the synthesis of optically active tetrahydro-,-carbolines and other benchmark N -acyl-1-aryl ethylamines. Im Rahmen dieser Arbeit wird die Rhodium-katalysierte asymmetrische Hydrierung von Enamiden vorgestellt, wobei ein besonderes Augenmerk auf der Synthese von Vorstufen für Indolalkaloide (1,2,3,4-Tetrahydro-,-carboline) lag. Nach Untersuchung verschiedenster Ligandensysteme und Optimierung der Reaktionsbedingungen konnten Enantioselektivitäten von bis zu 99,%,ee erzielt werden. Dabei erwiesen sich Phospholan-basierte Diphosphane als besonders geeignet zum Chiralitätstransfer. Die hervorragenden Eigenschaften dieser Ligandklasse konnte weiterhin in der asymmetrischen Hydrierung verschiedenster Enamide erfolgreich gezeigt werden. [source]