Methyl cyclopentadiene

Check your predictions by calculating activation energies for Diels-Alder additions. Data for transition states 1-methylcyclopentadiene+acrylonitrile and 1-methyl-cyclopentadiene+acrylonitrile BF3 are available. 

Enantioselective total syntheses of (-)-6-epitrehazolin and (+)-trehazolin were achieved by the synthesis of 275, which began with an asymmetric heterocycloaddition between [(benzyloxy)methyl]cyclopentadiene (263),108 prepared from thallous cyclopentadienide, and the acylnitroso compound arising from in situ oxidation of (,S )-mandelohydroxamic acid (264) with tetrabutylammonium periodate. Cycloaddition led to a mixture of 265 and its diastereomer (Scheme 35).109 The inseparable mixture was reduced to afford cyclopentenes 266 and 268 in 40% and 11 % overall yields, respectively, from thallous cyclopentadienide. Catalytic osmylation of 266 favored syn addition, while the osmylation of diacetate 267 was more selective and nearly quantitative, affording, after acetylation, compounds 270 and 269 in >5 1 ratio. 

Actually a mixture of positional isomers is obtained (V,a) l-methyl-3-MNB-cyclopentadiene (V,b) l-MNB-3-methyl-cyclopentadiene (V,c) 2-me-thyl-5-MNB-cyclopfentadiene (V,d) = l-methyl 4-MNB-cyclopentadiene (V,e) = 5-methyl-5-MNB-cyclopentadiene, where MNB = 5-endo-methylene-2-nor-bornene. Their relative abundance is (V,a) r (V,b) > (V,c) - (V,d) > (V,e). The last isomer is usually present as 10-15%, depending on the preparation conditions. ... 

On the other hand, a similar reaction of 5-acetyl-4-methyl- or 5-acetyl-2,4-dimethyloxazole leads to 2-acetyl-5-amino-l, 1,4-tricyano-3-methyl-cyclopentadiene (232), a yellow crystalline compound, in 60% yield. A mechanism of the formation of 232 has been proposed.883... 

Dicyclopentadiene, dipentene, styrene, CTLA polymer, and methyl-cyclopentadiene dimer were used as modifiers. These modifiers are all available in commercial quantities at 5-12 cents/lb. All contain unsaturated double bonds suitable for direct reaction with sulfur. The materials used in this investigation were from the following sources ... 

Reaction of (chloromethyl)diphenylphosphane (1) with sodium cyclopentadienide (NaCp) afforded [(diphenylphosphanyl)methyl]cyclopentadiene (2) in 50% yield after aqueous workup (Scheme 1). 2 is... 

In order to obtain [(trimethylsilyl)methyl]cyclopentadiene, a mixture of (chloromethyl)trimethylsilane (Aldrich) and sodium cyclopentadienide in anhydrous tetrahydrofuran (Aldrich) was stirred for two days at room temperature under a nitrogen atmosphere. The dark red Hquid obtained was filtered and distilled at room temperature (0.15 torr). The final product was employed during further kinetic studies. 

A control experiment entailed immersion of the cyclic imide functionalized plasma polymer surface into THF at 25 °C for 1 h. No changes in the infrared spectrum were observed (not shown). The intermediate amide functionalized plasma polymer surface was also exposed to a solution of cyclopentadiene in THF at 25 °C for 1 h. Infrared analysis showed spectral features similar to those described above for the imide surface, the main difference being the peak between 1800 and 1600 cm indicating the presence of amide rather than imide linkages at the surface. Finally, the plasma polymer surface functionalized with cyclic imide groups was exposed to [(trimethylsilyl)methyl]cyclopentadiene solution in cyclohexane at 25 °C for 1 h. Two new bands appeared at 2975 and 2890 cm characteristic of the asymmetric CH3 stretching and the symmetric CH3 stretching (Fig. 19.3, spectrum c). 

Fig. 19.3 I nfrared spectrum in the 3200 cm -2800 cm region of (a) the cyclic imide functionalized plasma polymer (b) the same polymer as for (a), after Diels-Alder reaction with cyclopentadiene (c) the same polymer as for (a) after Diels-Alder reaction with [(trimethylsilyl)methyl]-cyclopentadiene.

A comparative study of the temperature dependence of the Diels-Alder reaction between [(trimethylsilyl)methyl]cyclopentadiene and dienophile groups confined in selfassembled monolayers or in pulsed plasma polymer layers has been done. The reactivity of dienophile groups confined in pulsed plasma polymer thin films is compared with the behavior of dienophile groups in monolayers, because of their well-known arrangement properties. 

In Fig. 19.5 the inverse of the corresponding coverage is plotted versus the time of reaction. For all temperatures studied, we observed a linear dependence. This linear behavior indicates that the Diels-Alder reaction proceeds homogeneously and can be described by standard pseudo-second-order kinetics. The rate of the reaction V is described by Eq. (2), where [CpdSi] and Xc-c denote the concentration of [(trimethylsilyl)methyl]cyclopentadiene and the density of alkene groups at the surface respectively, p and q represent the partial orders of the reaction and koA the Diels-Alder rate constant... 

The mixture of double bond isomers of l,2,3,4-tetramethyl-5-(trifluoro-methyl)cyclopentadiene (Cp H) is a clear, colorless liquid with a sweet ole-finic odor similar to that of pentamethylcyclopentadiene. Cp H is an air-stable compound but it should be stored in the refrigerator. Although gas chromatographic analysis shows two peaks, the presence of all three of the possible cyclopentadiene isomers is indicated by H NMR spectroscopy as three quartets for the ring protons are observed at 3.26 (Jhf = 10.0 Hz), 2.99 (Jhh = 6.7 Hz), and 2.66 ppm (Jhh = 6.8 Hz) with a relative ratio of approximately 1 16 2.4 for isomers I, II, and III, respectively. Resonances between 4.8 and 5.0 ppm are attributed to products that result from an elimination mechanism rather than cyclization in the last step of the synthesis. These impurities boil very close to that of Cp H, but they are removed by careful fractional vacuum distillation as part of the forerun. The IR spectrum (neat liquid) exhibits significant bands at 2977(vs), 2937(vs), 2884(s), 2864(s), 2751(w), 1658(m), 1599(s), 1446(s), 1384(vs), 1357(vs), 1280(s), 1258(vs), 1164(vs), 1099(vs), 1012(vs), and 686(m) cm . The syntheses of organotransi-tion metal complexes are usually carried out with the 91% purity Cp H product. Because alkali metal and thallium salts of Cp are unstable, organo-transition metal complexes are prepared from Cp H itself, as are many complexes of pentamethylcyclopentadiene and cyclopentadiene."... 

Of the dienes, butadiene appears to have been the earliest to have been evaluated. Although it allowed accelerated sulphur vulcanization this was to the detriment of heat and oil resistance. More recently, non-conjugated dienes such as those used with EPDM rubbers have been quoted in the patent literature. These include dicyclopentadiene and methyl cyclopentadiene. A French patent (Tellier and Grimaud, 1968) quotes the use of tetrahydrobenzyl acrylate (VIII). 

Cyclic conjugated dienes such as cyclopentadiene and the isomeric methyl-cyclopentadienes undergo uncatalyzed dimerization to yield bicyclic adducts containing unconjugated diolefinic unsaturation [170]. It has been found that a copolymer can be obtained by reacting MA and the dimers of cyclic conjugated dienes in the presence of free radical precursors. The products of the copolymer-... 

Thickener, paper sizing Methyl cyclopentadiene United States 4,012,575 1977 Borg-Warner... 

Methylbicyclo[2,l,0]pent-2-ene (300) rearranges thermally to 1-methyl-cyclopentadiene (301), showing the process as one ascribable to a [ 2g + concerted cycloreaction involving C-1—C-2 and C-4—C-5 bonds and not a biradical two-step process. The cyclopentadiene (301) was trapped as it was formed (43 °C) as its iV-phenylmaleimide adduct (302), a process which completes favourably with the 1,5-hydrogen shift in the diene itself. It is pointed out that this result undermines the usual either/or concerted/non-concerted question of mechanism in that an unusual or suppressed concerted mechanism may be brought to the fore when the more obvious concerted mechanism is prohibited. ... 

Lithium methylcyclo-pentadienide + methyl -cyclopentadiene Tetrahydrofuran d iethy lenegly col dimethyl ether = 1 4 0.005-0.05... 

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