Dicyclopentadiene, selective

Reproductive toxicity was observed in rats administered lOOmg/kg by gavage in a continuous breeding protocol experiment fewer Fi pups were born live, and lower Fi pup weights and higher Fi pup mortality were observed. Increased liver and kidney weights were found at necropsy. These effects occurred at levels that also produced systemic toxicity, suggesting that dicyclopentadiene is not selectively a reproductive toxin. 

Because the norbomene double bond of dicyclopentadiene is more strained, its selective hydrofbrmyl-ation can be achieved under mild reaction conditions (entry 9). Under more vigorous reaction conditions both double bonds are hydroformylated. The exo faces of both rings are the least hindered, accounting for the selectivity. 

While norbornene, norbornadiene, 2-triallkylsilylnorbornadiene, and 1,3,5-cycloheptatriene are selectively deprotonated by the LIC-NAOR mixture (butyllithium/sodium /f 7-butoxide), other less acidic substrates such as bicyclo[2.2.2]oct-2-ene, camphene, 3,3-dimethyl-l-butene, and tro/o-dicyclopentadiene require the use of stronger bases constituted by mixtures of pentylsodium/disodium pinacolate (NAC-NAOR) or pentylsodium/ potassium ftrt-butoxide (NAC-KOR). 

Application Increase the value of steam cracker pyrolysis gasoline (py-gas) using conversion, distillation and selective hydrogenation processes. Pygas, the C5-C9 fraction issuing from steam crackers, is a potential source of products such as dicyclopentadiene (DCPD), isoprene, cyclopentane, benzene, toluene and xylenes. 

The skeletal isomerization of tetrabydrodicyclopentadiene into adamantane is an example of a very complex rearrangement diat is commercially carried out over strong Lewis acids with a hydride transfer initiator. The reaction can be catalyzed by rare earth (La, Ce, Y, Nd, Yb) exchanged faujasites (Scheme 1) in a Hj/HCl atmosphere at 25(yX3. Selectivities to adamantane of up to 50% have been reported, when a metal fimction, such as Pt, capable of catalyzing hydrogenation is added [54]. Initially acid catalyzed endo- to exo- isomerization of tetrahydro-dicyclopentadiene takes place and then a series of 1,2 alkyl shifts involving secondary and tertiary carbonium ions leads eventually to adamantane[55]. The possible mechanistic pathways of adamantane formation from tetrahydro-dicyclopentadiene are discussed in detail in ref [56]. 

Dimerization of the latter to a dihydrotetrazine comprises the major reaction pathway, however photolysis of the dihydrotetrazine to benzonitrile and 3,5-diphenyl-1,2,4-triazoIe also occurs. The overall reaction therefore resembles thermolysis but is more selective. Photolysis of 2,5-diphenyltetrazole in the presence of dipolarophiles methyl fumarate and dicyclopentadiene gives 1,3 dipolar addition products supporting the intermediacy of the azomethine imine. 

Since this reaction is a unimolecular example of the selective hydrogenation of an alkene mixture, the successful saturation of the less-substituted double bond should take place most readily over those catalysts that are most effective for the preferential saturation of one olefin in a mixture. Ruthenium has not been used extensively for such hydrogenations, but P-2 Ni(B) has been effective in promoting the selective hydrogenation of one of the double bonds in 46, methylene norbornene (49) (Eqn. 15.30), dicyclopentadiene (50) (Eqn. 15.31), and 2-methyl-1,5-hexadiene (51) (Eqn. 15.32).6 9,80,81... 

Partially reduced vanadium oxide catalysts have been examined in the selective oxidation of pentane and pentene to phthalic and maleic anhydride. The anhydride selectivity has been shown to be a strong function of catalyst pre-reduction and reaction temperatures. Controlled-atmosphere, postreduction and post-reaction surface characterization experiments have shown the most selective catalyst surface to.be comprised of VgO,j, V.,09, and VOg species. In this phase of the research, dicyclopentadiene has been used as a probe molecule to elucidate the reaction network for the formation of phthalic and maleic anhydrides. 

In this study, suboxides of vanadia catalysts were used in pentane, pentene, dicyclopentadiene and cyclopentane oxidation reactions. In the previous phase of the work [12,13], the role of alkali promoters on the catalyst selectivity was examined. The catalysts were reduced in situ at different temperatures and the effect of pre-reduction temperature was investigated. Controlled-atmosphere characterization of pre-reduction, post-reduction, and post-reaction catalysts were performed using X-ray diffraction. X-ray photoelectron spectroscopy, laser Raman spectroscopy and temperature-programmed desorption experiments. The objectives of this study were to determine the activity and selectivity of different suboxides of vanadia in... 

While our studies for identification of the active/selective phase continues, in a parallel effort, we have conducted some experiments to assess the role of dicyclopentadiene, one of the intermediates proposed in the literature [7]. The objective behind this phase of the study was to examine the routes that originate from dicyclopentadiene and result in phthalic anhydride versus maleic anhydride formation. The catalyst used in this set of experiments was vanadium pentoxide that was pre-reduced in situ at 400 °C with hydrogen. 

The two double bonds of dicyclopentadiene are very different in reactivity and, consequently, selective reactions are easy to achieve. 

P-2 Nickel boride shows a remarkable ability to selectively hydrogenate the strained double bond of norbornene. Thus hydrogenation of 5-methylenenor-bornene (1) and of the endo-dicyclopentadiene (3) give essentially quantitative yields of the dihydro derivatives (2) and (4), respectively.8... 

Ni boride (obtained from sodium borohydride reduction of Ni acetate in ethanol) exhibits sensitivity to substitution on the double bond, and to strained double bonds , and hence is useful for selective half-hydrogenation of dienes. Ni boride selectively hydrogenates the strained double bond of norbonene and dicyclopentadiene. Thus, a synthesis of 13-santalene involves the selective saturation of the endocyclic double bond of 7 over Ni boride, to afford 8 in 98% yield ... 

Allylamine is formed and reacts with 1,3-propanediamine to give 2-ethylhexa-hydropyrimidine, 25, which is dehydrogenated to 24 25 is efficient for selective hydrogenation of dienes such as dicyclopentadiene ... 

Over the course of 10 months, this synthesis generated 4.7 kilograms of varenicline (17% yield overall from benzonorbomadiene) from 50 kilograms of fluorobromobenzene 2 and 20 kilograms of dicyclopentadiene. This material fueled a fast-paced development program through the 6-month toxicological evaluation, salt selection, formulation and stability studies, and Phase 2 clinical trials. 

CATALYST ACTIVITY AND SELECTIVITY IN ROMP OF DICYCLOPENTADIENE INDUCED BY SOME TUNGSTEN SYSTEMS... 

Olefins containing isolated double bonds with different reactivity towards thiyl radicals are selectively co-oxidized at the more reactive unsaturation centre . This is the case of co-oxidation of endo and exo dicyclopentadienes with 4-chlorobenzenethiol (equations 102, 103). (The bracket indicates that the stereochemistry is unknown.)... 

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