Carbene Catalysts (carbene + catalyst)

Distribution by Scientific Domains


Selected Abstracts


Hydroaminomethylation of Olefins Using a Rhodium Carbene Catalyst.

CHEMINFORM, Issue 20 2003
Abdul Majeed Seayad
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Ligand Influence on Metathesis Activity of Ruthenium Carbene Catalysts: A DFT Study

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2007
Bernd
Abstract A survey of the concept of active and inactive ligand conformations in ruthenium alkene carbene complexes of the Grubbs catalyst type is presented. This concept is extended to a variety of anionic ligand atoms. Density functional theory calculations at the B3LYP/LACV3P**+//B3LYP/LACVP* level of theory were performed on the precatalyst, 14 valence-electron intermediate, alkene carbene conformers and ruthena(IV)cyclobutane model intermediates for several ligands, such as methoxide, methanethiolate, fluoride, mesylate, water, and ammonia. The rule of the superiority of metathesis catalysts with small and electron-withdrawing halogens does not apply to fluoride ligands. Alkoxides and thiolates also destabilize active carbene conformations, while mesylate ligands lead to a balanced energetic relation of active and inactive carbene orientations. Cationic ruthenium carbene species with aqua or ammine ligands are limited by unfavored ligand dissociation to 14 valence-electron intermediates. A guideline for the design of novel ligand systems for ruthenium carbene complexes as metathesis catalysts is proposed. [source]


New Soluble-Polymer Bound Ruthenium Carbene Catalysts: Synthesis, Characterization, and Application to Ring-Closing Metathesis.

CHEMINFORM, Issue 41 2003
Stephane Varray
Abstract For Abstract see ChemInform Abstract in Full Text. [source]


Development of Palladium,Carbene Catalysts for Telomerization and Dimerization of 1,3-Dienes: From Basic Research to Industrial Applications

CHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2008
Nicolas
Abstract The following account summarises recent developments in the area of palladium-catalysed telomerisation and dimerisation reactions of 1,3-dienes. The most active types of catalyst, palladium,carbene complexes, were tested in pilot plant and proved to be industrially viable. [source]


Organocatalytic Activity of N-Heterocyclic Carbenes in the Michael Addition of 1,3-Dicarbonyl Compounds: Application to a Stereoselective Spirocyclization Sequence

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009
Thomas Boddaert
Abstract An eco-compatible diversity-oriented synthesis of ,-spirolactones and ,-spirolactams is described. The overall transformation involves an olefin cross-metathesis followed by an intramolecular organocatalytic Michael-induced spirocyclization. Under microwave irradiation, the Hoveyda,Grubbs precatalyst can be iteratively used as the source of both the metathesis ruthenium-based catalyst, and the spirocyclization N-heterocyclic carbene catalyst. [source]


Enantioseparation of doubly functionalized polar norbornenes by HPLC and their ruthenium-catalyzed ring-opening metathesis polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2010
Yasushi Nishihara
Abstract Doubly fuctionalized polar norbornenes bearing the cyano and ester groups in 2,3-positions are synthesized and enantiomers are separated by high performance liquid chromatography (HPLC) with a chiral stationary phase. These optically active monomers are polymerized by ruthenium carbene catalysts, and high yields of the polymers were obtained. The chiral monomer bearing ethyl ester gave an optically active polymer of lower, but opposite sign of optical rotation (monomer [,]D = +61.0, polymer [,]D = ,3.1). The circular dichroism (CD) of the obtained chiral polymers gave a Cotton effect. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 485,491, 2010 [source]