1- methyl-norbomene

Andererseits konnte Kropp 41) bei der Bestrahlung von 2-Methyl-norbomen in Toluol oder Xylol als Sensibilisatoren keine dimeren Pro-dukte erhalten und nahm deshalb an. da6 die Methylgruppe deren Bil-dung verhindert. 

FIGURE 5. 62.8 MHz 13C NMR spectrum (olefinic region) of a 48% cis polymer of 1-methyl-norbomene. Catalyst Mo2(OAc)4/EtAlCl2. (HT + TH)/(HH + TT) = 2.8. The fine structure arises from double-bond triads, e.g. ccl, ccc, tct, tcc302. Reproduced by permission of the Society of Chemical Industry... 

Although very few catalysts are effective with molecules containing functional groups as well as double bonds, (diphenylcarbene)penta-carbonyltungsten and (phenylmethoxycarbene)pentacarbonyltungsten do initiate metatheses of ester derivatives of norbornene, such as the methyl norbomene-5-carboxylates (62a). 

The alkylation of the bis(aryloxide) [W(OC6H3Ph2-2,6)2CU] with LiCH2CMe3 leads to cyclometallated alkylidene compounds [W(OC6H3Ph- -C6H4)(OC6H3Ph2-2,6)(=CHCMe3)(OR2)]. These compounds will catalyse the metathesis of 2-pentene with high stereoselectivity, polymerize 1-methyl-norbomene to 100% cis, 100% head-to-tail, syndiotactic polymer, and cyclize a variety of functionalized dienes. 

Interestingly, while in general incorporation of 2-(acetoxy-methyl)norbomene is much more difficult than that of 2-(methoxycarbonyl)norbomene, Sujith et observed... 

The preference for endo attack in 7,7-dimethylnorbomene is certainly steric in origin, with the 7-methyl substituent shielding the exo direction of approach. The origin of the preferred exo-attack in norbomene is more subject to discussion. A purely steric explanation views the endo hydrogens at C—5 and C—6 as sterically shieldihg the endo approach. There probably is also a major torsional effect Comparison of the exo and endo modes of reproach shows that greater torsional strain develops in the endo mode of... 

Abbreviations aapy, 2-acetamidopyridine Aik, alkyl AN, acetoniuile Ar, aryl Bu, butyl cod, 1,5-cyclooctadiene COE, cyclooctene COT, cyclooctatetraene Cp, cyclopentadienyl Cp , penta-methylcyclopentadienyl Cy, cyclohexyl DME, 1,2-dimethoxyethane DME, dimethylformamide DMSO, dimethyl sulfoxide dmpe, dimethylphosphinoethane dppe, diphenylphosphinoethane dppm, diphenylphosphinomethane dppp, diphenylphosphinopropane Et, ethyl Ec, feirocenyl ind, inda-zolyl Me, methyl Mes, mesitylene nb, norbomene orbicyclo[2.2.1]heptene nbd, 2,5-norbomadiene OTf, uiflate Ph, phenyl PPN, bis(triphenylphosphoranylidene)ammonium Pi , propyl py, pyridine pz, pyrazolate pz, substituted pyi azolate pz , 3,5-dimethylpyrazolate quin, quinolin-8-olate solv, solvent tfb, teti afluorobenzobaiTelene THE, tetrahydrofuran THT, tetrahydrothiophene tmeda, teti amethylethylenediamine Tol, tolyl Tp, HB(C3H3N2)3 Tp , HB(3,5-Me2C3HN2)3 Tp, substituted hydrotiis(pyrazol-l-yl)borate Ts, tosyl tz, 1,2,4-triazolate Vin, vinyl. 

The catalytic arylation of SEM-protected azoles (SEM = [2-(trimethylsilyl) ethoxy]methyl) with monocarbene-Pd(ll) complexes [72], and the reductive Heck or hydroarylation of norbomenes with NHC-phosphine chelating ligands... 

Figure 38 (a) The ADMET polymerization (using Mo and Ru catalysts) of symmetrical a.oj-dienes that yield main-chain boronate polymers (59). (b) The ROMP of several norbomene monomers containing methyl- and phenyl-substituted boronates into unsaturated polymers (60). (Adapted from ref. 84.)... 

Acrylonitrile or methyl acrylate readily inserts into allylnickel bonds (example 34, Table HI). A trans double bond is formed by loss of a proton. Insertion of acetylene followed by oxidative elimination with allyl halides gives cis double bonds (example 32, Table III). Insertion of methyl propiolate, followed by proton uptake, leads to a trans double bond (example 33, Table III). Norbomene has been shown to insert stereoselectively cis.exo into an allylnickel bond (example 35, Table III). 

The results of the olefin oxidation catalyzed by 19, 57, and 59-62 are summarized in Tables VI-VIII. Table VI shows that linear terminal olefins are selectively oxidized to 2-ketones, whereas cyclic olefins (cyclohexene and norbomene) are selectively oxidized to epoxides. Cyclopentene shows exceptional behavior, it is oxidized exclusively to cyclopentanone without any production of epoxypentane. This exception would be brought about by the more restrained and planar pen-tene ring, compared with other larger cyclic nonplanar olefins in Table VI, but the exact reason is not yet known. Linear inner olefin, 2-octene, is oxidized to both 2- and 3-octanones. 2-Methyl-2-butene is oxidized to 3-methyl-2-butanone, while ethyl vinyl ether is oxidized to acetaldehyde and ethyl alcohol. These products were identified by NMR, but could not be quantitatively determined because of the existence of overlapping small peaks in the GC chart. The last reaction corresponds to oxidative hydrolysis of ethyl vinyl ether. Those olefins having bulky (a-methylstyrene, j8-methylstyrene, and allylbenzene) or electon-withdrawing substituents (1-bromo-l-propene, 1-chloro-l-pro-pene, fumalonitrile, acrylonitrile, and methylacrylate) are not oxidized. 

It has been reported by R.Scheiner that phenylazide forms triazoline compounds by 1,3-cyclic addition to unsaturated olefines such as n-butylethylene and norbornen(9 ). These triazolines are decomposed photochemically or thermally to give imine compounds and aziridine as is shown in scheme 1. These facts suggest that phenylazide may react with 3-methyl-1-butene to give triazoline in a similar reaction to that with norbomen. 

The meso-ionic l,3-dithiol-4-ones (134) participate - in 1,3-dipolar cycloaddition reactions giving adducts of the general type 136. They show a remarkable degree of reactivity toward simple alkenes including tetramethylethylene, cyclopentene, norbomene, and norbor-nadiene as well as toward the more reactive 1,3-dipolarophilic olefins dimethyl maleate, dimethyl fumarate, methyl cinnamate, diben-zoylethylene, A -phenylmaleimide, and acenaphthylene. Alkynes such as dimethyl acetylenedicarboxylate also add to meso-ionic 1,3-dithiol-4-ones (134), but the intermediate cycloadducts are not isolable they eliminate carbonyl sulfide and yield thiophenes (137) directly. - ... 

Hydroformylation of norbomene proceeds slowly in spite of the expected reactivity of the strained double bond. Racemization of the product aldehyde does not occur under the reaction conditions. The hydroformylation of methyl methacrylate gives only one isomer, which is a useful chiral synthon. Dimethyl itaconate also can be hydroformylated using (12) as the chiral ligand to give aldehyde product in 82% ee accompanied by hydrogenated ester.64... 

Dimethylcarbene The usual methods for generation of carbenoids lead to poor results in the case of dimethylcarbene. The most satisfactory method involves generation in the presence of an alkene by a-elimination with n-butyllithium from 2,2-dibromopropane (which must be completely free from acetone or 2-bromoacetone), used after a detailed study of cyclopropanation of tetramethylethylene (equation I). n-Butyllithium is superior to methyl- or isopropyllithium. Addition of TMEDA or KOC(CH3)3 completely supresses cyclopropanation. Yields are improved by a lower reaction temperature. In all experiments, 35-45% of the alkene is recovered. Yields decrease with a decrease of alkyl substituents on the double bond thus the yield is only 9% in the case of l-dodecene. No cyclopropane was obtained from 2-norbomene. 

Figure 5.50 shows three related molecules, the 7-methyl substituted (the visual orbital progression explained here is not quite as smooth for the unsubstituted molecules) derivatives of the 7-norbomyl cation (a), the neutral alkene norbomene (b), and the 7-norbomenyl cation (c). For each species an orbital is shown as a 3D region of space, rather than mapping it onto a surface as was done in Fig. 5.49. In (a) we see the LUMO, which is as expected essentially an empty p atomic orbital on C7, and in (b) the HOMO, which is, as expected, largely the n molecular orbital of the double bond. The interesting conclusion from (c) is that in this ion the HOMO of the double bond has donated electron density into the vacant orbital on C7 forming a three-center, two-electron bond. Two n electrons may be cyclically delocalized, making the cation a bishomo (meaning expansion by two carbons) analogue of the aromatic cyclopropenyl cation [326], This delocalized bishomocyclopropenyl structure for 7-norbomenyl cations has been controversial, but is supported by NMR studies [327].

Amino acid-based norbomene random and block copolymers have been synthesized by Sanda, Masuda et al. [178]. The blocks were constructed with monomers containing either the ester or carboxyl amino acid forms, and C4 was used. While the random copolymers were partially soluble in acetone, the block copolymers were soluble through formation of reverse micelles (Scheme 24). Moreover, the diameter of these aggregates was around 100 nm as measured by DLS and AFM. Amino acid-based ROMP monomers with a different cyclic core, i.e., cyclobutenecarbonyl glycine methyl esters, were polymerized by Sampson et al., leading to head-to-tail-ordered polymers without stereocenters [179]. C6 was used and polydispersities between 1.2 and 1.6 were obtained. 

Figure 3.5 Variation of retention (net retention volume per unit surface area of stationary phase) with the temperature in GSC. Stationary phase GTCB (carbon). Solutes o/p-xylene (1), m-xylene (2), n-octane (3), ethylbenzene (4), toluene (5), n-heptane (6), methylcyclohexane (7), exo-5-methyl-norbornene (8), endo-5-methylnorbornene (9), norbornane (10) and norbomene (11). Figure taken from ref. [309], Reprinted with permission. 

PiccineUi [5] used (tricyclopentylphosphine)dichloro(3-methyl-butenylidene), (VI), or related cyclic derivatives, (VII), to prepared anti-fog agents, (Vlll), by coupling 2-norbomene and aUyl-terminated ohgomeric ethylene oxide using ring opening metathesis polymerization as illustrated in (VIII) below. 

TABLE 2. Effect on the polymerization of norbomene methyl ester by varying the catalyst composition ratios of hexaflnoroisopropanol and palladinm acetate while keeping di-t-bntylcyclohexylphosphine and diethyl zinc levels constant. 

Note The monomer ratio of norbomene methyl ester-to-di-t-butylcyclohexylphosphine was 10,000 1.25, respectively. 

A 300-ml flask was charged with 4-(di-trifluoromethyl-hydroxymethyl)-l-((di-tri-fluoromethyl) methyl)cyclohexyl] vinylsulfonate (7.00 g), 5-(2,2-trifluoromethyl-2-hydroxy)ethyl-norbomene (7.58 g), and t-butyl trifluoromethylacrylate (5.42 g) dissolved in 1,4-dioxane (5.0 g). This mixture was then treated with 2,2 -azobisiso-butyronitrile (0.34 g) and polymerized at 60°C for 24 hours. The reaction mixture was poured into 1 liter of hexane, and the precipitated was isolated. The polymer was purified by dissolving in THF and re-precipitating in hexane, this process being repeated twice, and 12.5 g of a white polymer product were isolated. 

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