A,co-Diolefins

Because the criss-cross cycloaddition reaction is a sequence of two [3+2] cycloaddition steps, the reaction with a,co-diolefins offers a new entry into macro-molecular chemistry New types of polymers with interesting structures and prop erties can be synthesized [213, 214, 215] (equation 48)... 

In view of the observed inactivity of a, a-disubstituted olefins towards polymerisation with Ziegler-Natta catalysts, it is interesting to note that a, co-diolefins substituted at unsaturated carbon atoms, such as e.g. 2,5-dimethyl-l,5-hexa-diene, also undergo cyclopolymerisation, analogously to unsubstituted parent monomers [2,446], This can be interpreted in terms of a reaction pathway analogous to that shown in scheme (89). The insertions in the cyclopolymerisation appear to be facilitated by the nature of such a process. 

It has been reported [497] for cyclopolymerisations with metallocene-based catalysts that the enantioface selectivity of the insertion of the first olefinic bond in the a, co-diolefin determines the relative stereochemistry between the rings (the occurrence of m or r diads), i.e. the tacticity of the cyclopolymer the diastereoselectivity of the subsequent cyclisation involving the remaining olefinic bond determines, on the other hand, the relative stereochemistry in the rings (the occurrence of M or R diads), i.e. the cis-trans geometrical isomerism of the rings. 

The cyclopolymerisation of unsymmetrical a, co-diolefins such as 2-methyl-1,5-hexadiene in the presence of catalysts such as Cp2 ZrMc2 M(Me)0 x, [Cp2 , ZrMe]+ [B(C6F5)4] or [Cp2 ZrMe]4 [McB(C6 F5)2] yields highly regiore-gular cyclopolymers [501]. The perfectly head-to-tail linked monomeric units in the formed poly[methylene-l,3-(l-methylcyclopentane)] arises from the chemo-selective insertion of the less hindered terminus of 2-methyl-1,5-hexadiene into the active Mt—P bond, followed by cyclisation involving the insertion of the disubstituted olefinic bond (Figure 3.50) [497]. The insertion of the disubsti-tuted olefinic bond is made easier by its intramolecular nature. 

Figure 3.51 Enantiomorphic site control versus conformational control in the cyclisation step during cyclopolymerisation of a, co-diolefins 1,5-hexadiene (x=l), 1,6-heptadiene (x—2) and 1,7-octadiene (x=3) in the presence of a metallocene-based catalyst of C2 symmetry...

Whereas poly(a-olefins) have only two microstructures of maximum order (isotactic, syndiotactic). cyclopolymers ° have /bur microstructures due to the rings present in their main chain which can be either cis or trans in configuration (Scheme 17). While the key issues concerning selectivity in the polymerization of a-olefins are regioselectivity (head-to-tail monomer incorporation) and enantioface selectivity (tacticity). cyclopolymerization of a.co-diolefins has added concerns. First, since the monomer has two olefins, either cyclization or cross-linking of the... 

Intramolecular methathesis of a,co-diolefins containing a heteroatom in the chain 97AG(E)2036. 

This process allows the synthesis of a,co-diolefins by cross-metathesis of cycloolefins with ethylene. The reaction was first studied by Phillips who produced multi-tons of... 

One of the butadiene dimerization products, COD, is commercially manufactured and used as an intermediate in a process called FEAST to produce linear a,CO-dienes (153). COD or cyclooctene [931-87-5], obtained from partial hydrogenation, is metathesized with ethylene to produce 1,5-hexadiene [592-42-7] or 1,9-decadiene [1647-16-1], respectively. Many variations to make other diolefins have been demonstrated. Huls AG also metathesized cyclooctene with itself to produce an elastomer useful in rubber blending (154). The cyclic cis,trans,trans-tnene described above can be hydrogenated and oxidized to manufacture dodecanedioic acid [693-23-2]. The product was used in the past for the production of the specialty nylon-6,12, Qiana (155,156). 

Coordination polymerisation via re complexes comprises polymerisation and copolymerisation processes with transition metal-based catalysts of unsaturated hydrocarbon monomers such as olefins [11-19], vinylaromatic monomers such as styrene [13, 20, 21], conjugated dienes [22-29], cycloolefins [30-39] and alkynes [39-45]. The coordination polymerisation of olefins concerns mostly ethylene, propylene and higher a-olefins [46], although polymerisation of cumulated diolefins (allenes) [47, 48], isomerisation 2, co-polymerisation of a-olefins [49], isomerisation 1,2-polymerisation of /i-olcfins [50, 51] and cyclopolymerisation of non-conjugated a, eo-diolefins [52, 53] are also included among coordination polymerisations involving re complex formation. 

In 1928-1929, Fischer, Tropsch, and Koch (8, 9, 10) published the results of an analysis of the oil product from an Fe-Cu catalyst operated at atmospheric pressure and 250° C. The fraction boiling in the range 60-185° C. was 70% olefinic. The 30% saturates contained octane, nonane, and isonane no diolefins or naphthenes were found. Minute amounts (0.1-0.4%) of benzol and toluol were present. The isononane was probably 3-methyloctane and was present in very small amount. A very small amount of 3,3-dimethylpcntene-l also was present. In 1928, an analysis was published by Smith, Hawk, and Reynolds (11) of the product from a Co-Cu-MnO catalyst. This product, although more saturated, was similar to that obtained by Fischer and his coworkers from an Fe-Cu catalyst. In 1930-1932, Kodama and other Japanese experimenters (12, 13, 14, 15) published data on the efficiency of different promoters such as Cu, ThOj, WOt, M0O3, MgO for the cobalt catalyst. 

The first method that has been mainly used since the 1960s was based on polycondensation of a, -dihydroxysiloxanes, while the second method which has been developing during the last three decades is based on polyhy-drosilylation of a, -diolefines with a, co-dihydro terminated siloxanes. 

Degradation of pol5usobutylene or poly(isobutylene-co-isopropylene) at low temperature in the presence of a Lewis acid yields a,ft>-diolefin telechelics (461). 

The polymerization sequence of B-R-9-BBN prepared from 1,7-octadiene is employed [6] for intermolecular cross-coupling with 1,4-dibromobenzene or 1,4-diiodobenzene in the presence of dichloro[l,l -bis(diphenylphosphino) ferrocene] palladium (II) [PdCl2(dppf)j. Similarly, hydroboration of diolefin with 9-BBN, followed by the intermolecular cross-coupling of the resulting a,co-bis(B-alkanediyl-9-BBN) with dihaloarenes are performed in the presence of PdCl2(dppf), a base, and phase-transfer catalyst [7]. Both the steps are performed in the same flask. 

The diolefin 1064 gives rise to the isoxazoline 1065, which cannot eliminate tri-methylsilanol 4 [122]. Cychzation of the co-nitroolefin 1066 with trimethylchloro-silane (TCS) 14/triethylamine at -35 °C then HCl-induced removal of trimethyl-silanol 4 leads, in 85% yield, to the dimer 1067, which is converted in two more steps into racemic pyrenophorin 1068 [112] (Scheme 7.39). Further cyclizations of co-nitroolefins [109] to monomeric or dimeric isoxazolines have been described. Conjugated dienes such as butadiene afford a mixture of the mono or bis adducts [115-117]. 

H-stacking interactions have also been exploited to orientate olefinic moieties in a geometry suitable for photochemical cycloaddition reactions, and have been invoked by Coates et al. to explain the photodimerization and photopolymerization of mono- and diolefins carrying phenyl and perfiuorophenyl groups [43]. Matsumoto et al. reported the photodimerization of 2-pyridone in co-crystals with naphthalene-substituted monocarboxyhc acids, where the stacking of the naphthalene rings provides carbon-carbon distances appropriate for [4+4] cycloaddition [44]. 

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