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Transition-Metal Catalysts (transition-metal + catalyst)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

A Highly Efficient Carbon,Sulfur Bond Formation Reaction via Microwave-Assisted Nucleophilic Substitution of Thiols to Polychloroalkanes Without a Transition-Metal Catalyst.

CHEMINFORM, Issue 23 2007
Yi-Ju Cao
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, please click on HTML or PDF. [source]

Rapid and Efficient Microwave-Assisted Amination of Electron-Rich Aryl Halides Without a Transition-Metal Catalyst.

CHEMINFORM, Issue 4 2004
Lei Shi
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Titelbild: Cooperative Catalytic Reactions Using Organocatalysts and Transition-Metal Catalysts: Enantioselective Propargylic Alkylation of Propargylic Alcohols with Aldehydes (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 40 2010
40/2010)
Ein Übergangsmetallkatalysator und ein Organokatalysator kooperieren, um eine enantioselektive propargylische Alkylierung zu erreichen. Y. Nishibayashi et,al. stellen in der Zuschrift auf S.,7447,ff. das Verfahren vor, und sie vergleichen die kooperative Aktion der Katalysatoren mit dem Einsatz von Essstäbchen. [source]

Cooperative Catalytic Reactions Using Organocatalysts and Transition-Metal Catalysts: Enantioselective Propargylic Alkylation of Propargylic Alcohols with Aldehydes,

ANGEWANDTE CHEMIE, Issue 40 2010
Masahiro Ikeda
Ein gutes Gespann: Die Titelreaktion liefert in Gegenwart eines thiolatverbrückten Dirutheniumkomplexes (2) und eines sekundären Amins (1) die alkylierten Propargylderivate in ausgezeichneten Ausbeuten als Mischung zweier jeweils hoch enantioselektiv gebildeter Diastereomere. Die beiden Katalysatoren aktivieren den Propargylalkohol bzw. den Aldehyd und fördern gemeinsam die enantioselektive Reaktion. [source]

Microwave-Assisted Cross-Coupling and Hydrogenation Chemistry by Using Heterogeneous Transition-Metal Catalysts: An Evaluation of the Role of Selective Catalyst Heating

CHEMISTRY - A EUROPEAN JOURNAL, Issue 43 2009
Muhammed Irfan
Abstract The concept of specific microwave effects in solid/liquid catalytic processes resulting from the selective heating of a microwave-absorbing heterogeneous transition-metal catalyst by using 2.45,GHz microwave irradiation was evaluated. As model transformations Ni/C-, Cu/C-, Pd/C-, and Pd/Al2O3 -catalyzed carbon,carbon/carbon,heteroatom cross-couplings and hydrogenation reactions were investigated. To probe the existence of specific microwave effects by means of selective catalyst heating in these transformations, control experiments comparing microwave dielectric heating and conventional thermal heating at the same reaction temperature were performed. Although the supported metal catalysts were experimentally found to be strongly microwave absorbing, for all chemistry examples investigated herein no differences in reaction rate or selectivity between microwave and conventional heating experiments under carefully controlled conditions were observed. This was true also for reactions that use low-absorbing or microwave transparent solvents, and was independent of the microwave absorbtivity of the catalyst support material. In the case of hydrogenation reactions, the stirring speed was found to be a critical factor on the mass transfer between gas and liquid phase, influencing the rate of the hydrogenation in both microwave and conventionally heated experiments. [source]

A Robust Protein Host for Anchoring Chelating Ligands and Organocatalysts

CHEMBIOCHEM, Issue 4 2008
Manfred T. Reetz Prof. Dr.
Abstract In order to put the previously proposed concept of directed evolution of hybrid catalysts (proteins that harbor synthetic transition-metal catalysts or organocatalysts) into practice, several prerequisites must be met. The availability of a robust host protein that can be expressed in sufficiently large amounts, and that can be purified in a simple manner is crucial. The thermostable enzyme tHisF from Thermotoga maritima, which constitutes the synthase subunit of a bi-enzyme complex that is instrumental in the biosynthesis of histidine, fulfills these requirements. In the present study, fermentation has been miniaturized and parallelized, as has purification of the protein by simple heat treatment. Several mutants with strategically placed cysteines for subsequent bioconjugation have been produced. One of the tHisF mutants, Cys9Ala/Asp11Cys, was subjected to bioconjugation by the introduction of a variety of ligands for potential metal ligation, of a ligand/metal moiety, and of several organocatalytic entities that comprise a flavin or thiazolium salts. Characterization by mass spectrometry and tryptic digestion was achieved. As a result of this study, a platform for performing future directed evolution of these hybrid catalysts is now available. [source]