Norbomene cyclopentene

The tendency of cyclic olefins to undergo cis dicarbonylation rather than trans methoxycarbonylation was attributed to their steric strain, which is in the order norbomene > cyclopentene > cycloheptene > cyclooctene > cyclohexene. Steric strain relief would allow a stronger complexation and dicarbonylation. Stille interpreted the... 

Alternating copolymers of ethylene with olefins containing double bonds in the cis configuration, like ds-2-butene, cyclopentene, cycloheptene,115 and norbomene,116 have been described. Recently also copolymers of carbon monoxide with styrene and styrene derivatives, having syndiotactic117 and isotactic118 configurations, have been synthesized and characterized. 

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. 

As a last example we mention polydicyclopentadiene (DCPD). Dicyclopentadiene is the Diels-Alder adduct of cyclopentadiene, an abundant product from the cracker in the refinery. It contains a strained norbomene ring and a less strained cyclopentene ring. ROMP leads to opening of the norbomene ring, but some reaction of the cyclopentene ring also takes place, which leads to cross-linking (Figure 16.26). 

Co2(CO)6 fragments at the C=C triple bonds further from the Pt center. The Pauson-Khand reaction between tra 5-Pt C=CC2H[Co2(CO)6] (PR3)2 (R = Et, Bu) (197) and norbomene or cyclopentene gives the corresponding cyclopen-tenones 198 (Scheme 44). ... 

Since it is known that the cyclopentene ring of norbomene can be easily opened by methylidene carbene complex Ih, bicyclic compound 66 has been synthesized from norbomene derivative 65 having an alkene part in a sidechain in the presence... 

It appears that oxiranes known to give predominantly a-deprotonation in basic media (cyclopentene, cyclooctene and exo-norbomene oxide) are also the more strained (Table 1 entries 3, 6, 7). On the other hand, oxiranes that give mainly -deprotonation (butene, cyclohexene oxide) have lower strain energies and higher a-anion stabilities (Table 1 ... 

Counterion effects similar to those in ionic chain copolymerizations of alkenes (Secs. 6-4a-2, 6-4b-2) are present. Thus, copolymerizations of cyclopentene and norbomene with rhenium- and ruthenium-based initiators yield copolymers very rich in norbomene, while a more reactive (less discriminating) tungsten-based initiator yields a copolymer with comparable amounts of the two comonomers [Ivin, 1987]. Monomer reactivity ratios are also sensitive to solvent and temperature. Polymer conformational effects on reactivity have been observed in NCA copolymerizations where the particular polymer chain conformation, which is usually solvent-dependent, results in different interactions with each monomer [Imanishi, 1984]. 

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. - ... 

Ethynylcyclopropanes, like normal acetylenes, react with dicobalt octacarbonyl in ether to form stable dinuclear cluster-like hexacarbonyl complexes (equation 170)236. The complex with l-chIoro-2,2,3,3-tetramethylethynylcyclopropane reacts stereo- and regioselec-tively with norbomene in a typical Pauson-Khand reaction to give the exn-2-cyclopropyl substituted cyclopentenone (equation 171). Similarly, the reaction of 2-ethoxycyclo-propylacetylene with cyclopentene in the presence of Co2(CO)8 under CO gave 3-(2-ethoxycyclopropyl)-cw-bicyclo[3.3.0]oct-3-en-2-one (equation 172)242. 

The reaction of norbomene yields the cis exo diester (equation 66).93 This exo isomer is not obtained directly by Diels-Alder chemistry. Other cyclic alkenes such as cyclopentene yield cis diesters, but isomers are obtained as a result of (3-hydride elimination-readdition from intermediates such as (23) prior to CO insertion (equation 67). Thus the palladium walks around the ring to some extent, but always stays on the same face. The extent of rearrangement can be minimized by higher CO pressures since CO insertion becomes more competitive with (3-elimination. This rearrangement becomes a critical problem in the dicarboxylation of 1-alkenes, since a variety of diesters are formed and the reaction is not particularly useful. These reactions were carried out with catalytic amounts of palladium and stoichiometric amounts of copper chloride. 

For 5- or 5,6-substituted norbomenes the exo-isomer is usually rather more reactive than the ewrfo-isomer. An extreme case is provided by the exo- and mfo-isomers of 190 where the exo-isomer polymerizes first, followed much more slowly by the endo-isomer see Section Vm.C.12. In other cases the endo-isomer will not polymerize but will copolymerize to some extent with its exo-isomer, as with the isomers of 197531. Other examples of this kind, where M2 will not homopolymerize using a particular catalyst, are the copolymerization of norbomene (Mi), (i) with cyclopentene (M2), catalysed by Ru(OTs)2(OH2)6597, (ii) with 192, catalysed by WClg/Me4Sn526 and (iii) with cyclohexene (M2), catalysed by WCl6/Me4Sn358,359. 

Einen direkten Weg zu Derivaten des cis-verknupften Bicyclo [3,2,0]-heptans stellt die analoge photochemische Addition von Maleinsaureester an Cyclopenten dar (195). Produkte mit trans-Verkniipfung der 4- und 5-Ringe werden nicht gebildet. Die unsensibilisierte Photoaddition von Maleinsauredimethylester an Norbomen fiihrt ausschlieBlich zum exo-Tricyclo[4,2,l,02.5]nonan-Derivat (143). 

The 60-MHz NMR spectra of norbomene, endo-DCP, and exo-DCP in CS2 using tetramethyl silane as the internal standard are shown in Figures 2, 3, and 4, respectively. The norbomene unsaturations in endo-and exo-DCP are more downfield than the respective cyclopentene unsaturations (9). Furthermore, the cyclopentene unsaturation in endo-DCP gives a singlet and in exo-DCP a multiplet, thus rendering it possible to distinguish easily between the two isomers (9). In norbomane, V, the C-2-exo and C-2-endo protons have chemical shifts of 1.49 8 and 1.18 8, respectively (10), and thus can be distinguished. 

Compound 1 did not react with unstimned internal olefins such as tetramethylethylene, /ra s-3-hexene, tram-stilbene, cyclooctene, cyclohexene, or cyclopentene. But imposing strain to the olefinic moiety resulted in a clean silylene transfer to the double bond Norbomene formed with 1 the tricyclic silacyclopropane 6. Whereas 2 did not add to the double bond of 7, methylene cyclopropane 8 could be transformed into spiro[2.2]pentane 9 by reaction with 1. Addition of 2 to bicyclopropylidene allowed the convenient synthesis of dispiro[2.0.2.1]heptane 10 in a quantitative manner. 

In cyclopentene systems with fixed envelope conformation, the torsional interactions induce a high preference for the epoxide with boat conformation of the peripheral six-mem-bered ring (including the transferred oxygen, see Table 1), as, for example, epoxidation of norbomene (1) to give exo-2. This is shown mechanistically from the projection along the C-C bound adjacent to the reacting C-C double bond. 

In a novel combination of Pauson-Khand cycloaddition with vinylcyclopropane chemistry, de Meijere has described an entry to linearly fused triquinanes beginning with cyclopropylalkynes. Cyclopentenone formation has been carried out with a variety of substitution patterns on the cyclopropane, and moderate yields achieved with both norbomene and cyclopentene as substrates. Thermal vinylcyclopropane-cy-clopentene rearrangement of the cycloaddition products leads to the final tricyclic system (Scheme... 

The equilibrium constants for a series of cycloalkenes decrease in the order norbomene > c -cyclooc-tene > cyclopentene > cycloheptene > cyclohexene, which correlates with the calculated strain energies as well as the kinetically determined relative adsorption constants on Pt (Table 2). Tolman states that electron donation from a filled metal rf-orbital to an empty alkene Tr -orbital is extremely important in determining the stability of these complexes. Steric effects of substituents are relatively unimportant compared to electronic effects, and resonance is more important than inductive interactions. The ability of the metal to back bond is lowered progressively in the series Ni° > Pt° > Rh > Pt" > Ag which reduces the importance of resonance and decreases the selectivity of the metal for different substituted alkenes. 

The course of the decomposition reaction is much dependent on the relative stereochemistry of the substituents on the C—C bond of the triazoline At intermediate temperatures (40-90°) the stereochemistry is conserved and usually only one product is detected. Cyclopentene, cycloheptene and cu-cyclooctene reacted with phenyl azide to give the corresponding iV-phenylimino derivatives in excellent yields, while cyclohexene and (mnj-cyclooctene did not yield imines at all, iziridines being the sole products . When higher temperatures are used, the stereochemical selectivity is apparently lost and a mixture of products is generally observed. In the reaction of norbomene... 

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