Metathesis olefin isomerization

Fustero, S. Sanchez-Rosello, M. Jimenez, D. Sanz-Cervera,J.F. DelPozo,C. Acena,J. L. Role of the gem-difluoro moiety in the tandem ring-closing metathesis-olefin isomerization regioselective preparation ofunsaturated lactams. 7. Org. Chem. 2006, 77(7), 2706-2714. 

Olefin-CO coploymers Olefin p-complexes Olefin Fibers Olefin hydroformylation Olefin hydrogenation Olefimc alcohols Olefin isomerization Olefin metathesis Olefin oligomers Olefin oxides... 

Conventionally, organometallic chemistry and transition-metal catalysis are carried out under an inert gas atmosphere and the exclusion of moisture has been essential. In contrast, the catalytic actions of transition metals under ambient conditions of air and water have played a key role in various enzymatic reactions, which is in sharp contrast to most transition-metal-catalyzed reactions commonly used in the laboratory. Quasi-nature catalysis has now been developed using late transition metals in air and water, for instance copper-, palladium- and rhodium-catalyzed C-C bond formation, and ruthenium-catalyzed olefin isomerization, metathesis and C-H activation. Even a Grignard-type reaction could be realized in water using a bimetallic ruthenium-indium catalytic system [67]. 

Several olefin complexes of the Ru(II) aqua-ion [42-44] and of the other Ru complexes [45, 46] have been synthesized and characterized in the ring opening metathesis polymerization (ROMP) or olefin isomerization reactions. The simplest olefin complexes of Ru were also observed, isolated and characterized under ethy-... 

Olefin isomerization, with Claisen rearrangement, 1, 365 Olefin metathesis with alkyllead, 9, 415 in aqueous media, 1, 834 ESI—MS studies, 1, 812 in high-throughput catalyst discovery, 1, 365 in ionic liquids, 1, 869 for polymerization characteristics, 1, 149 Grubbs catalysts, 1, 151 Schrock catalysis, 1, 150... 

The 10-undecenoic acid motif has also been attached to isosorbide in the preparation of a fatty acid-/carbohydrate-based monomer [131]. ADMET polymerization in the presence of C3 and C4 produced fully renewable unsaturated polyesters (Scheme 18). Most importantly, the transesterification of these polyesters with MeOH, and subsequent analysis by GC-MS of the products, allowed for the quantification of double-bond isomerization during ADMET in a very simple manner. This strategy was then extended to fatty acid-based ADMET polyesters synthesized in the presence of indenylidene metathesis catalysts [132]. With these studies, the knowledge on the olefin isomerization in ADMET reactions was widened, and it is now possible to almost completely suppress this undesired side reaction. 

A tandem RCM-alkene isomerization sequence to form 5-, 6-, and 7-membered enol ethers was reported by Snapper and co-workers <02JA13390> (Scheme 36). In this process the RCM reaction is run under an atmosphere of 95 5 N2.TI2 to convert the intermediate ruthenium alkylidene into an olefin-isomerization catalyst. Note that alkene migration can convert isomeric metathesis products into the same 2,3-enol ether. A single example of the formation of a 6-membered tosyl enamide was reported in this manuscript. 

ADMET offers a synthetic route to strictly linear, fimctionalized polyethyl-enes through the polymerization of a,co-dienes followed by exhaustive hydrogenation. Researchers have been able to use metathesis catalysts in conjimction with the functionalized monomers to produce statistical or sequenced copolymers of ethylene with various polar monomers. With the improved tolerance and reactivity of [ Ru], the broadening of ADMET methodology will allow the syntheses of numerous functionalized systems [4]. However, due to the well known olefin isomerization that occurs during the metathesis polymerization with [Ru], monomer sequence control is lost and the methylene run length between functional groups varies widely. 

As vinyl ethers were known to be poor substrates in Ru-catalyzed olefin metath-eses, it has been difficult to obtain cydic enol ethers by RCM of the vinyl ethers. Recently, a novel method to obtain cyclic enol ethers has been reported, which afforded cydic enol ethers directly from easily prepared dienes containing an allyl ether moiety [46]. Treatment of 70 with diene 99 in CH2CI2 in the presence of small amount of H2 resulted in a formation of dihydropyran 101 (Eq. 12.40). Treatment of 70 with H2 has been thought to produce an active catalyst for the olefin isomerization, and only metathesis products are formed until a small amount of H2 is introduced in the reaction. These results implied that this reaction most likely proceeded by way of a formation of the cyclic olefin 100, which was subsequently converted to dihydropyran 101 by the newly formed isomerization catalyst. In addition to the tandem reaction shown in Eq. 12.40, another method for obtaining cydic enol ethers from allyl ethers has also been demonstrated [46b]. This method induded addition of the hydride donor, such as NaBH4, to the reaction solution after the metathesis reaction had been completed. Although attempts to observe an active species for olefin isomerization in the presence H2 failed, these results suggested participation of hydride species in the olefin isomerization. 

It has been reported that treatment of 70 with silyl enol ether generates active species only toward olefin isomerization (Eq. 12.41) [47]. When vinyl acetate was added to the reaction instead of silyl enol ether, neither metathesis nor isomerization took place. Although details of the active species remain unclear, Fischer-type carbene complexes would be formed in the reaction of 70 with silyl enol ether. It has also been recognized that hydride-carbonyl complexes were formed by the thermolysis of... 

Olefin metathesis is a useful reaction for the production of propylene from ethylene and butenes using certain transition-metal compound catalysts. The two main equilibrium reactions that take place simultaneously are metathesis and isomerization. Metathesis transforms the carbon-carbon double bond, a functional group that is unreactive toward many reagents that react with many other functional groups. New carbon-carbon double bonds are formed at or near room temperature even in aqueous media from starting materials. Because olefin metathesis is a reversible reaction, propylene can be produced from ethylene and butene-2. Metathesis can be added to steam crackers to enhance the production of propylene by the transformation of ethylene and the cracking of mixed butenes. Fig. 3 shows a schematic flow diagram of a typical metathesis process. Examples of metathesis... 

The other process based on Manassen/Joo s ideas of liquid supports [19, 20] goes back to Keim s developments of organic-organic biphase systems for the Ni-catalyzed conversion of olefins to medium- and long-chain alpha- and internal olefins [38] by a combination of various process steps, among them oligomerization, metathesis, and isomerization. This is described in Chapter 3. 

This method allows the quantification of the olefin isomerization that may occur in the course of ADMET polymerization using second generation ruthenium metathesis catalysts. 

Further, it was demonstrated that the addition of benzoquinone to the polymerization mixture prevents the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts can be used for the preparation of well defined polymers via an ADMET technique causing little isomerization (32). 

Olefin metathesis (Olefin Conversion Technology, OCT) of ethylene and 2-butene (manufaaured by isomerization of 1 -butene) yielding propylene. ... 

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