Cyclooctene, metathesis

Cyclooctadiene, metathesis of, 135 stereoselectivity, 159, 160 Cyclooctene, metathesis of, catalysts for, 140... 

What is the result of cyclooctene metathesis Give the mechanism of product formation. 

Another example is the metathesis of cyclooctene, which produces poly-octenylene, an elastomor known as trans-polyoctenamer ... 

Catalysts with an unsymmetrical NHC ligand featuring a vinylic side chain have the unique ability to metathesise their own ligand to form a metaUacycle as shown in Scheme 3.7 [119], Ring opening metathesis will then incorporate the monomers, e.g. cyclooctene, into that cycle until a cyclic polymer is cleaved by another intramolecular metathesis step. The catalyst is recovered and can restart this endless route to cyclic polymers [121]. 

Fig. 3.31 Steric control in alternating ROMP Tendencies of norbomene and cyclooctene to give productive olefin metathesis upon coordination are illustrated by a thick arrow (preferred monomer) or a thin arrow (less favoured monomer) (a) only minor steric hindrance SlMes greatly favours the polymerisation of the strained norbomene (b) the rotating phenylethyl-group induces a steiically more congested active site, leading to preferred incorporation of the smaller cyclooctene (c) the flexible and small cyclooctene derived polymer fragment permits the incorporation of the bulky norbomene...

Conversions of about 80% were obtained within a few minutes at 90°C. The polymer could also be cleaved by cross-metathesis with an excess of 4-octene which gave, as the main product, 9-tridecenyl-7-undecenoate, thus confirming the structure assignment as indicated in Eq. (62). The unsaturated lactone was also copolymerized with cyclooctene, 1,5-cy-clooctadiene, and cyclopentene under the previously stated conditions to afford linear copolymers which were high molecular weight, unsaturated, rubbery polyesters (110). 

Further important industrial applications of olefin metathesis include the synthesis of 3,3-dimethyl-l-butene ( neohexene , intermediate for the production of musk perfume) from ethene and 2,4,4-trimethyl-2-pentene, the manufacture of a,co-dienes from ethene and cycloalkenes (reversed RCM), and the ROMP of cyclooctene and norbomene to Vestenamer and Norsorex , respectively. 

This complex XV was proved to be an active alkene metathesis catalyst even at 0 °C or room temperature. The in situ generated catalyst XV catalyzed the ROMP of cyclooctene at room temperature at high cydooctene/Ru ratio (Table 8.2 entries 4,5) reaching TOF of more than 17000min. ... 

Ring-opening metathesis polymerization was conducted by Verpoort et al. (4) using cyclooctene with a ruthenium Schiff base complex, (V), and proceeded with a monomer-to-catalyst ratio of 150,000 1, respectively. 

The ROMP of alcohol, ketone, halogen, and acetate substituted cyclooctenes with a ruthenium olefin metathesis catalyst has been reported (31). 

M.A. Hillmyer, W.R. Laredo, and R.H. Grubbs, Ring-opening metathesis polymerization of functionalized cyclooctenes by a ruthenium-based metathesis catalyst, Macromolecules, 28(18) 6311-16,1995. 

The synthesis of polyoctenamer has been commercialized by Huels.150 In contrast with the transformation of cyclooctene to 1,9-decadiene [Eq. (12.31)], homogeneous catalyst compositions, such as WClg + EtAlCl2, are used to promote ring-opening metathesis polymerization of cyclooctene. A polymer of narrow molecular-weight distribution with high trans content (55-85%) called Vestenamer is produced and used as blend component in different rubbers and thermoplastics. 

Polymers of monocyclic olefins (cyclopentene, cyclooctene) produced by ring-opening metathesis are linear elastomers. Their properties are somewhat similar to those of poly eri-1,4-hn i.idiene). Polymers of dicy-clopentadiene produced with the same catalysts are heavily cross-linked resins displaying high toughness and tensile strength as well as excellent impact strength at low temperatures. 

Cis- and fraws-cyclooctene, 100 and 102 respectively, and their derivatives 103-107, all undergo ROMP295 also 10862,362,109 and 11062, 111-113362, 114363,115364,116365, 118362, 119 and 120366,367. Only 101295 and 117362 fail to polymerize, perhaps due to unfavourable choice of catalyst and conditions. The trans monomer 102 gives a 43% cis polymer very rapidly in the presence of MoCl2(PPh3)2(NO)2/EtAlCl2368 and is polymerizable by 18110. With a catalyst of type 10 secondary metathesis reactions of the double bonds in the polymer of 100 cause the cis content to fall from 75% to 25% as the reaction proceeds271. 

The ROMP of [2.2]paracyclophane-l,9-diene (128) yields poly(p-phenylenevinylene) (129) as an insoluble yellow fluorescent powder. Soluble copolymers can be made by the ROMP of 128 in the presence of an excess of cyclopentene387, cycloocta-1,5-diene388 or cyclooctene389. The UV/vis absorption spectra of the copolymers with cyclooctene show separate peaks for sequences of one, two and three p-phenylene-vinylene units at 290, 345 and about 390 nm respectively, with a Bernoullian distribution. The formation of the odd members of this series must involve dissection of the two halves of the original monomer units by secondary metathesis reactions. 

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