Dienes linear

Other general references in this section are presented as titles, as follows The behavior of 3-ferrocenyl-1-methyl-1,2-pentamethyleneallyl and 1,5-diferrocenyl-3-methyl-2,4-tetramethylene-l,4-dienyl carbocations in the cationic dimerisa-tion of 1,3-dienes Linear and nonlinear optical properties of diiron p-vinylcar-byne acceptor and stilbenyl donor based chromophores Organometallic iron(II) hydrazines and hydrazones - syntheses, characterisations and the X-ray crystal structures of [Fe(ri -Cp)(r -C6H5NHNH2)] PF6 and [Fe(ri -Cp)(ri -p-MeQH4NHN = CMez)] +PF6-. ... 

Pd-cataly2ed reactions of butadiene are different from those catalyzed by other transition metal complexes. Unlike Ni(0) catalysts, neither the well known cyclodimerization nor cyclotrimerization to form COD or CDT[1,2] takes place with Pd(0) catalysts. Pd(0) complexes catalyze two important reactions of conjugated dienes[3,4]. The first type is linear dimerization. The most characteristic and useful reaction of butadiene catalyzed by Pd(0) is dimerization with incorporation of nucleophiles. The bis-rr-allylpalladium complex 3 is believed to be an intermediate of 1,3,7-octatriene (7j and telomers 5 and 6[5,6]. The complex 3 is the resonance form of 2,5-divinylpalladacyclopentane (1) and pallada-3,7-cyclononadiene (2) formed by the oxidative cyclization of butadiene. The second reaction characteristic of Pd is the co-cyclization of butadiene with C = 0 bonds of aldehydes[7-9] and CO jlO] and C = N bonds of Schiff bases[ll] and isocyanate[12] to form the six-membered heterocyclic compounds 9 with two vinyl groups. The cyclization is explained by the insertion of these unsaturated bonds into the complex 1 to generate 8 and its reductive elimination to give 9. 

The linear dimerization of substituted conjugated dienes is difficult, but the Pd-catalyzed intramolecular dimerization reaction of the 1,3,9,11-tetraene 13 gives the 3-propenylidene-4-allylpiperidine derivative 14, which has the 1,3,7-octatriene system. The corresponding 1,3,8,10-tetraene also affords the 3-pro-penylindene-4-allylcyclopentane derivative[18]. 

Another interesting transformation is the intramolecular metathesis reaction of 1,6-enynes. Depending on the substrates and catalytic species, very different products are formed by the intramolecular enyne metathesis reaction of l,6-enynes[41]. The cyclic 1,3-diene 71 is formed from a linear 1,6-enyne. The bridged tricyclic compound 73 with a bridgehead alkene can be prepared by the enyne metathesis of the cyclic enyne 72. The first step of... 

Because of the linear geometry required of cumulated dienes cyclic allenes like cycloalkynes are strained unless the rings are fairly large 1 2 Cyclononadiene is the smallest cyclic allene that is sufficiently stable to be isolated and stored conveniently... 

AlkyUithium compounds are primarily used as initiators for polymerizations of styrenes and dienes (52). These initiators are too reactive for alkyl methacrylates and vinylpyridines. / -ButyUithium [109-72-8] is used commercially to initiate anionic homopolymerization and copolymerization of butadiene, isoprene, and styrene with linear and branched stmctures. Because of the high degree of association (hexameric), -butyIUthium-initiated polymerizations are often effected at elevated temperatures (>50° C) to increase the rate of initiation relative to propagation and thus to obtain polymers with narrower molecular weight distributions (53). Hydrocarbon solutions of this initiator are quite stable at room temperature for extended periods of time the rate of decomposition per month is 0.06% at 20°C (39). 

The thiophthalimide (CTP) and sulfenamide classes of retarders differ from the organic acid types by thek abiUty to retard scorch (onset of vulcanization) without significantly affecting cure rate or performance properties. Much has been pubUshed on the mechanism of CTP retardation. It functions particularly well with sulfenamide-accelerated diene polymers, typically those used in the the industry. During the initial stages of vulcanization, sulfenamides decompose to form mercaptobenzothiazole (MBT) and an amine. The MBT formed reacts with additional sulfenamide to complete the vulcanization process. If the MBT initially formed is removed as soon as it forms, vulcanization does not occur. It is the role of CTP to remove MBT as it forms. The retardation effect is linear with CTP concentration and allows for excellent control of scorch behavior. 

One of the butadiene dimeri2ation products, COD, is commercially manufactured and used as an intermediate in a process called FEAST to produce linear a,C0-dienes (153). COD or cyclooctene [931-87-3], obtained from partial hydrogenation, is metathesi2ed 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 metathesi2ed cyclooctene with itself to produce an elastomer useful in mbber blending (154). The cycHc cis,trans,trans-tn.en.e described above can be hydrogenated and oxidi2ed 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). 

Polymerisation of conjugated dienes can frequently lead to the formation of linear polymers containing main chain double bonds. Examples of such diene... 

Reduction of linearly conjugated 4,6-dien-3-ones with lithium-ammonia yields either 5-en-3-ones or 4-en-3-ones depending upon the work-up procedure. Protonation of the dienyl carbanion intermediate (58) occurs at C-7 to give ultimately the enolate ion (59) kinetic protonation of (59) occurs largely at C-4 to give the 5-en-3-one (60). ... 

Most dienones that have been reduced have structures such that they cannot give epimeric products. However, reduction of 17 -hydroxy-7,17a-dimethyl-androsta-4,6-dien-3-one (63) affords 17 -hydroxy-7j9,17a-dimethylandrost-4-en-3-one (64), the thermodynamically most stable product, albeit in only 16% yield. The remainder of the reduction product was not identified. Presumably the same stereoelectronic factors that control protonation of the / -carbon of the allyl carbanion formed from an enone control the stereochemistry of the protonation of the (5-carbon of the dienyl carbanion formed from a linear dienone. The formation of the 7 -methyl compound from compound (63) would be expected on this basis. 

The characteristic property distinguishing macrocyclic polyamines from their linear counterparts is seen in successive protonation. One is the higher N basicity to the first proton and another is a sudden drop of N basicities in the later stages of protonation. Table 1 lists the protonation constants (Eq. 1) for the macrocyclic polyamines in comparison with the corresponding values for their linear homologues. When a linear triamine (e.g. dien) 36,37) is cyclized to, say, (9)aneN3, the basicity of the first amine increases (log Kt = 10.59 us 9.70), but the basicity of the second and especially the third amine diminish (log K2 = 6.88 vs 8.95, log K3 < 1 vs 4.25)36)... 

The polymerization of nonconjugated diene monomers might be expected to afford polymer chains with pendant unsaturation and ultimately, on further reaction of these groups, crosslinked insoluble polymer networks. Thus, the finding by Butler et a .,, 03, n5 that polymerizations of diallylammonium salts, of general structure 8 [e.g. diallyldimethylammonium chloride (9)] gave linear saturated polymers, was initially considered surprising. 

The process may be used to form linear polymers. Nuyken and Volkel224 225 described a method for tclcchclic production, based on the radical initiated reaction of difunctional transfer agents with dienes (e.g. divinyl benzene (13), dimethacrylate esters). However, currently the most common use of thiol-ene... 

The cycloadditions of the C-2 vinyl glicals with maleic anhydride are an interesting example of facial stereocontrol. The allylic methoxy group in dienes 55a and 55b exerts an nnh -stereodirecting effect as shown by the stereochemistry of the endo-cycloadducts 56 and 57 obtained as the sole products from 55a and 55b, respectively, and by the fact that 55c produces [51] a mixture of the diastereoisomers 56c and 57c (Scheme 2.22). When linear acetylenic dienophiles were used, the degree of facial diastereoselectivity decreased, which indicates its dependence on steric effects. 

However, the products can then react with additional monomers and with each other, so that polymers are generally produced, and the cyclic dienes are obtained only in low yield. The reaction between a cyclic and a linear alkene can give an ring-opened diene... 

Diene-based polymers such as polybutadiene have other structural distinctions. The linear versions of these polymers have one residual double bond for each mer. When the double bonds are in the polymer chain, the cis and trans stereoisomers are possible. The double bonds can appear as pendant vinyl groups, which can then exhibit tacticity. 

X-ray structure analysis showed that macrocycle 57 was essentially planar, with the twist angle of the benzene rings from the plane of the macrocycle being less than 2°. Most of the strain was seemingly contained in the triple bonds, as these were bent from linearity by 10.1° to 12.3°. Despite its strained nature, the macrocycle showed remarkable stability. Decomposition occurred above 300°C on attempted melting. No reaction was observed between 57 and cyclopenta-diene at room temperature. 

In 2009, Ritter and coworkers reported a selective Fe-catalyzed hydroboration of 1,3-dienes to produce linear ( )-y-disubstituted allylboranes under mild conditions when a combination of Ll-FeCl2 and magnesium metal as a catalyst was used. Tbe branched ( )-allylboranes were obtained by using L2-FeCl2 instead of Ll-FeCl2 (Scheme 26) [88]. For the synthesis of 2-borylallylsilanes, this method was superior to the previously reported silaboration of allenes [89]. 

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