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Enyne metathesis reaction mechanism by Ella Melton - …

“Chemoselective Olefin Metathesis Transformations Mediated by Ruthenium Complexes.” 39 (8): 3305–3316.

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Topic: Ring Closing Metathesis Review – 893819 | …

In the Hoye study, the authors found that increased enyne concentration (to 0.1M) gave an efficient ring-closing metathesis.[] This is counterintuitive since high dilution is employed in bifunctional substrates to limit oligomerization. This is the first example showing that solution concentration of the enyne affects the rate of metathesis. Subsequently, Diver and coworkers used a high concentration of ethylene to assist the rate of enol ether-alkyne cross metathesis ().[] In this case, certain alkynes did not react efficiently without ethylene.

Chemoselective olefin metathesis transformations mediated by ruthenium complexes.
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Shortly after the seminal report of catalytic ring closing enyne metathesis, chromium Fischer carbenes were employed by Mori and coworkers to form nitrogen heterocycles.[-] Though these reactions were substoichiometric or even stoichiometric in the chromium complexes, this paper elevated an interesting organometallic reaction to one that might prove useful in organic synthesis, where the presence of functional groups places great demands on chemoselection. Mori's papers stimulated interest in the reaction since heterofunctionality could be handled. Though this work was limited to ring-closing applications and lacked the functional group range now expected in metathesis chemistry, it offered a rapid method for heterocycle synthesis.

» Topic: Grubbs Olefin Metathesis Review – 439880

Many metathesis catalysts react with aldehydes in a [2 + 2] fashion just as they do with olefins.
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Alkene metathesis is predicted to proceed fast and reversible, while the insertion of the alkyne substrate is slower, irreversible, and kinetically regioselectivity determining.

The alkyne insertion step and the cycloreversion of 2-vinyl ruthenacyclobutanes feature comparable predicted overall barriers in intermolecular enyne metathesis.

Grubbs Olefin Metathesis Review

Recent reviews describe the synthetic utility of enyne metathesis in good detail [1–3] .
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If the catalyst is too active, it can metathesize the olefinic bonds in the growing polymer chain (a process called "back-biting"), thereby reducing the molecular weight and increasing the molecular weight distribution (polydispersity).

AB - A concise synthesis of the potent nAChR agonist (+)-anatoxin-a (1) has been completed by a series of nine chemical operations and in 27% overall yield from commercially available D-methyl pyroglutamate (12). The strategy featured the application of a new protocol for the diastereoselective synthesis of cis-2,5-disubstituted pyrrolidines bearing unsaturated side chains and an intramolecular enyne metathesis to provide the bridged bicyclic framework of 1. Thus, D-methyl pyroglutamate (12) was converted in five steps to 32, which underwent facile enyne metathesis to deliver the bicyclic diene 33. Selective oxidative cleavage of the less substituted carbon-carbon double bond in 33 followed by deprotection furnished (+)-anatoxin-a (1).

This short review primarily describes my group's effort towards understanding reactivity of the metal carbenes in the enyne metathesis.
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  • METATHESIS | Alkene | Catalysis

    “Chemoselective Olefin Metathesis Transformations Mediated by Ruthenium Complexes.” 39.8 (2010): 3305–3316.

  • Enyne metathesis reaction mechanism - …

    KW - Ring closing metathesis

  • Kinetics and Mechanism of Intermolecular Enyne Metathesis

    T1 - A Simple and Effective Co-Catalyst for Ring-Closing Enyne Metathesis Using Grubbs I type Catalysts

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Ring Closing Metathesis Review | ISMSi

The η3-complexes 68A,B are not metathesis-active. The mechanistic origin of the η3-complexes is unclear. Their genesis presumably lies on the metathesis pathway but they are formed by a shunt from normal alkyne polymerization (for alkyne only) or from normal enyne metathesis (when both alkyne and alkene are present).

Supported Catalysts Useful in Ring-Closing Metathesis, ..

The vinyl carbene complexes were all metathesis-active. The carbene complexes were evaluated in a benchmark ring-closing alkene metathesis of dimethyl diallylmalonate. The distorted second generation complex 64 was found to be the most active followed by 67A, 60A and 66. The metathesis activity found for these chelates, as well as the general knowledge that the Hoveyda carbene complex is an active initiator for metathesis, suggests that chelation is not sufficient to extinguish metathesis activity. Further studies on chelation effects with different functional groups are still needed.

Application of intramolecular enyne metathesis to the ..

Anthony J. Giessert was born in Buffalo, NY, in 1978. He received his B.S. in chemistry from Canisius College in 2000. He is currently a fourth year graduate student at the University at Buffalo−The State University of New York exploring enyne metathesis under the direction of Dr. Steven Diver.

Olefin Metathesis ebook by Karol Grela - Rakuten Kobo

The vinyl carbene complexes described above are not reported to have metathesis activity. As cationic complexes bearing a CO ligand, it is unlikely that phosphine would be readily dissociated. This would preclude a dissociative mechanism needed for metathesis activity. It would be intriguing to learn whether the CO could be removed from the neutral hexacoordinate complex 80 above to produce a metathesis-active carbene.

Enyne Metathesis (Enyne Bond Reorganization) - …

Steven T. Diver grew up in Salt Lake City and attended the University of Utah where he studied with Professor F. G. West as an undergraduate researcher. Diver went on to do his doctoral work with Professor Ed Vedejs at the University of WisconsinMadison, studying nucleophilic catalysis promoted by phosphines. Diver conducted postdoctoral studies with Professor Stuart Schreiber at Harvard where he used alkene metathesis to make chemical dimerizers. Presumably this is where he got bitten by the metathesis bug. Diver began his independent work at the University at Buffalo−The State University of New York (SUNY−Buffalo) in 1997. Diver's research group is interested in the application of enyne metathesis to challenging synthetic problems, mechanistic aspects of the enyne metathesis, and catalyst design employing unusual heterocyclic carbene ligands.

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