Collins 7 Olefin Metathesis Polymerization 269 Astrid-Caroline Knall and Christian Slugovc Section III APPLICATIONS OF OLEFIN METATHESIS REACTIONS285 8 Applications in the Synthesis of Natural and BiologicallyActive Molecules 287 Janine Cossy 9 Multifold Ring-Closing Olefin Metatheses in Syntheses ofOrganometallic Molecules with Unusual Connectivities 311 Tobias Fiedler and John A.
Griffiths 5 Domino and Other Olefin Metathesis Reaction Sequences187 Bernd Schmidt and Stefan Krehl 6 Enantioselective Olefin Metathesis 233 Brice Stenne and Shawn K.
The Swedish academy's choice "confirms what is generally agreed upon in the synthetic chemistry community—that olefin metathesis is a very useful catalytic reaction that has a broad scope," comments Harvard University chemistry professor and Nobel Laureate .
In olefin metathesis, two carbon-carbon double bonds react to form two new carbon-carbon double bonds. In the process, substituents attached to the carbon atoms involved are exchanged. This exchange can result in various outcomes, including straight swapping of substituents, closure of large rings, formation of dienes, and polymerization. The reaction, which is catalytic, takes place under mild conditions and is so general that it is widely applicable.
With improvements in metal-carbene initiators, the reaction became more widely used. Schrock and Grubbs led efforts to develop the catalysts that now allow olefin metathesis to flourish. Schrock's catalysts are based on molybdenum; Grubbs's are based on ruthenium and are widely credited with having put olefin metathesis in the hands of synthetic chemists because the catalysts are easy to use. "Chemists now routinely use the catalysts to prepare pharmaceutical candidates and new materials in an efficient and environmentally friendly way," says Jeremy M. Berg, director of the , which has supported the research of the American winners.
Exploration of Ring Rearrangement Metathesis (RRM) reaction: A general and flexible approach for the rapid construction [5,n] fused bicyclic systems en-route to linear triquinanesRanjan Kumar Acharyya, Rohan Kalyan Rej and Samik Nanda*J Org Chem …
Olefin metathesis is a chemical reaction in which two carbon-carbon double bonds (olefins) come together and exchange with one another, forming new olefinic products in the process.
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.
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.
Ring-opening metathesis polymerization (ROMP) uses metathesis catalysts to generate polymers from cyclic olefins. ROMP is most effective on strained cyclic olefins, because the relief of ring strain is a major driving force for the reaction – cyclooctene and norbornenes are excellent monomers for ROMP, but cyclohexene is very reluctant to form any significant amount of polymer. Norbornenes are favorite monomers for ROMP, as a wide range of monomer functionalities are easily available through Diels-Alder reactions.
* Provides basic information for non-specialists, while also explaining the latest trends and advancements in the field to experts * Discusses the various types of metathesis reactions, including CM, RCM, enyne metathesis, ROMP, and tandem processes, as well as their common applications * Outlines the tools of the trade--from the important classes of active metal complexes to optimal reaction conditions--and suggests practical solutions for common reaction problems * Includes tables with structures of commercial catalysts, and recommendations for commercial catalyst suppliers.
Lipshutz and Subir Ghorai 22 Olefin Metathesis in Green Organic Solvents and WithoutSolvent 523 Christian Bruneau and Cedric Fischmeister 23 Olefin Metathesis in Fluorous Phases and in FluorinatedAromatic Solvents 537 Cezary Samoj³--owicz, Anna Kajetanowicz, and KarolGrela 24 Olefin Metathesis in Ionic Liquids 547 Pierre Queval, Mathieu Rouen, Annie-Claude Gaumont, IsabelleDez, Olivier Basle, and Marc Mauduit 25 Purification Strategies in Olefin Metathesis 559 Krzysztof Skowerski and GBPukasz Gu³--ajski PART III TABLES AND CHARTS 573 Section VI OLEFIN METATHESIS CATALYSTS A TABULAR REVIEW575 GBPukasz Wo'zniak, Grzegorz Zieli'nski, andKarol Grela Outlook and Perspectives 587 INDEX 589.
Schrock alkylidenes for olefin metathesis of the type Mo(NAr)(CHMe2R)(OC(CH3)(CF3)2) were commercialized starting in 1990 .