ruthenium-based olefin metathesis catalyst, ..

N2 - The mechanism of the transition metal catalyzed olefin metathesis reaction with the Schrock catalyst is investigated with pure (BP86) and hybrid (B3LYP) density functional theory. On the free-energy surface there is no adduct between ethylene and model catalyst (MeO)

Schrock’s Catalyst | Olefin Metathesis

Olefin Metathesis - Chemistry LibreTexts

Olefin Metathesis, Grubbs Reaction - Organic chemistry

Secondary metathesis reactions (controlled by catalyst choice and reaction conditions) also affect the product distribution. Recoordination of an alkene on the growing polymer chain with the catalyst can lead to cyclic oligomers through a ring-closing metathesis reaction (“backbiting”). Chain transfer (cross metathesis) between a growing polymer unit and an adjacent polymer alkene also leads to broadened molecular weights. Chain transfer can also be used to improve processability of the resulting polymer – addition of an acyclic olefin (chain-transfer agent) can limit chain molecular weights and introduce terminal functional groups.

Olefin Metathesis Grubbs Reaction

Careful balance of catalyst, monomer, and other factors can offer excellent control of the polymer structure. In terms of homogeneous catalysts, most tungsten and molybdenum catalysts (Schrock catalysts) have rapid initiation rates and can produce “living” polymerizations with excellent control of polydispersity and chain tacticity, but the low functional group tolerance limits the monomers available. Ruthenium metathesis catalysts (Grubbs catalysts) tend to have slower initiation rates, often leading to higher polydispersities, but their air stability and greater tolerance for functional groups makes them “user friendly” and enables use of a wide range of functional monomers and additives.

C&EN: COVER STORY - OLEFIN METATHESIS: BIG DEAL REACTION

Kinetically controlled E-selective catalytic olefin metathesis

Employing the standard cross-metathesis assay previously described, the chelated-adamantyl catalyst provides the heterocoupled product in 87% Z-selectivity at 64% reaction conversion. Interestingly, allylbenzene also undergoes self-metathesis during the above cross-metathesis assay, providing the homocoupled product in >95% Z-selectivity. Also noteworthy is the fact that the best experimental conditions involve performing the reaction in a 1:1 mixture of THF:H2O, thus, dry solvents are not a requirement. However, it is noted that strict exclusion of oxygen is required.

28/09/1995 · Because of the relative simplicity of olefin metathesis, ..

This reaction is closely related to olefin metathesis

Materia Inc. was founded in partnership with Prof. Grubbs and Caltech to expand the use of metathesis. Users can now purchase metathesis (pre)catalysts from Materia to make commercial APIs without negotiating a license. Materia also offers process guidance and other technical services [14]. Materia’s business model should facilitate pharma’s use of metathesis for preparing APIs.

Grubbs synthesizes the world’s first well-defined ruthenium olefin metathesis catalyst

But none of the complexes catalysed olefin metathesis

Now, Koji Endo and Bob Grubbs have described the first report of a Ru-based catalyst that favors the formation of cis olefins, employing a novel chelated NHC catalyst architecture in conjunction with a pivalate ligand. The catalyst synthesis involves treatment of a standard 2nd generation Grubbs-Hoveyda type catalyst with silver pivalate, which leads to a subsequent intramolecular C-H activation of the ortho-CH3 group of the symmetrical mesityl NHC ligand, or of the CH2 group of the 1-adamantyl substituent in the unsymmetrical adamantyl/mesityl NHC ligand. This marks the first report of such C-H activated chelates providing metathesis active complexes. Generally, this type of NHC ligand derived C-H activation occurs from coordinatively unsaturated species during a metathesis reaction, leading to catalyst decomposition.

Ring Closing Metathesis - Organic Chemistry Portal

Ring Closing Metathesis (RCM) ..

“However, despite the recent success of ruthenium and Group VI systems, new catalysts, which undergo more turnovers and function under practical experimental conditions, are clearly needed to tackle more advanced olefin substrates and metathesis reactions.”