1-Octene metathesis

Cl3(dme)W=C Bu (A) as catalyst in the ROMP of cyclopentene and in 1-octene metathesis [3]. We found that this carbyne complex is very active in both metathesis reactions. 

In 1998, Ookoshi and Onaka reported remarkable increase in activity of M0O3 when this was supported on hexagonal mesoporous silica instead of conventional one. With this catalyst (7 wt % Mo) they achieved high conversion of 1-octene into 7-tetradecene at 50°C. Similarly in 2002, Onaka and Oikawa found rhenium oxide dispersed on mesoporous alumina with uniform pore size (7 wt % Re) to be more active in 1-octene metathesis than rhenium oxide on conventional y-alumina. Although both works lacked detailed characterization of supports and prepared catalysts, they clearly showed the positive effect of organized mesoporous siqrport on catalyst activity in alkene metathesis. 

The mechanism of norbornene polymerisation has been investigated using complex (44) as catalyst. Cis-coordination of the olefin is necessary for catalytic activity. The performance is improved by irradiation, by the solvent and especially by Lewis acids. A WCCOlg/CCli, mixture becomes a slow catalyst for 1-octene metathesis under photolytic conditions. ... 

SCHEME 12.3 Dissociation (A to B ) and activation (Bn to Fn) steps in the mechanism of productive 1-octene metathesis using RuCl2(PCy3)L(0 N)(=CHPh) [L = PCyj or H IMes, O N = l-(2-pyridinyl)cyclohexan-l-olate]. 

FIGURE 12.2 Electronic energy profiles of the activation steps in the productive 1-octene metathesis using III (only the C 4 to Fjj4 structures are shown) (Cp mode). 

The possibility of phosphine or NHC ligand dissociation from the respective flrst-and second-generation hemilabile carbenes should not be excluded, because it is generally assumed that ruthenium-catalyzed metathesis reactions proceed through 14-electron intermediates. Conseqnently, we have postulated a mechanism for the first- and second-generation hemilabile-catalyzed 1-octene metathesis reaction (Scheme 12.3) whereby the 0,N-ligand remains attached to the Ru-center. 

It also explains the /Z selectivity of products at low conversions (kinetic ratio. Scheme 19). In the case of propene, a terminal olefin, E 2-butene is usually favoured (E/Z - 2.5 Scheme 19), while Z 3-heptene is transformed into 3-hexene and 4-octene with EjZ ratios of 0.75 and 0.6, respectively, which shows that in this case Z-olefins are favoured (Scheme 20). At full conversion, the thermodynamic equilibriums are reached to give the -olefins as the major isomers in both cases. For terminal olefins, the E olefin is the kinetic product because the favoured pathway involved intermediates in which the [ 1,2]-interactions are minimized, that is when both substituents (methyls) are least interacting. In the metathesis of Z-olefins, the metallacyclobutanes are trisubstituted, and Z-olefins are the kinetic products because they invoke reaction intermediates in which [1,2] and especially [1,3] interactions are minimized. 

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). 

Metathesis of 1-octene leads cleanly to ethene and 7-tetradecene, but as the reaction proceeds also 2-octene is formed and metathesis products derived from the isomerisation reaction. It was found that after prolonged reaction times decomposition of the ruthenium alkylidene catalyst occurs. At least eight different products were formed and several of them have been identified [37], Figure 16.22 shows the identified compounds derived from Grubbs 1st generation catalyst (the 2nd generation gives basically the same result [38]). 

Experimental Procedure 3.2.9. Cross Metathesis with a Molybdenum Catalyst in Homogeneous Phase (E)- -Phenyl-1-octene [929]... 

Table 14.2 Comparison between silica-supported, silsesquioxane, and molecular Mo(VI) precursor as catalysts for octene and ethyl oleate self-metathesis.

A number of new processes exploiting metathesis have been developed by Phillips. A novel way to manufacture lubricating oils has been demonstrated.145 The basic reaction is self-metathesis of 1-octene or 1-decene to produce Ci4-C28 internal alkenes. The branched hydrocarbons formed after dimerization and hydrogenation may be utilized as lubricating oils. Metathetical cleavage of isobutylene with propylene or 2-butenes to isoamylenes has a potential in isoprene manufacture.136,146 High isoamylene yields can be achieved by further metathesis of C6+ byproducts with ethylene and propylene. Dehydrogenation to isoprene is already practiced in the transformation of isoamylenes of FCC C5 olefin cuts. 

The Mo-catalysed cross-metathesis of acrylonitrile (59) [17,18] and allylsilane (60) [19] with alkenes 61 and 62 produced cross-products 63 and 64 with high selectivity. Reaction of 1-octene with 2 equivalents of styrene (65) afforded 66 in 89% yield. Only small amounts of stilbene (68) and 67 as the homoproducts were formed [23]. 

W(OAr)2Cl4 [C4Ciim]Cl-AlCl3- Cross-metathesis of linear olefins, e.g. conversion of 1-pentene to form ethylene and Et AlCl . . , , 4-octene no reaction details given system active tor several runs [22]... 

To date, low volumes of materials have been produced commercially from norbomene and cyclo-octene. Numerous products are expected to result from the materitd produced by the ROMP of dicyclopentadiene in a RIM (reaction injection molding) process. In a RIM process, two streams of a monomer are mixed in the mold where it is polymerized to the final part. In this case, one of the monomer streams contains a tungsten complex while the second contains an alkyl aluminum activator. When the two streams of dicyclopentadiene are mixed, the metathesis catalyst is formed and the monomer is ROMP polymerized (equation 12). 

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