Norbomadiene oxide

Remote double bonds often participate in epoxide openings, sometimes with extensive skeletal changes. ejco-Norbomadiene oxide (15 equation 6) provides an interesting example. Meinwald et alP found that this very acid-sensitive material rearranged simply on standing to give the endo-aldehyde (17), presumably via the intermediate nortricyclanol ion (16). 

The oxidation of norhomadiene by i-butyl perbenzoate and Cu(I) leads to 1-t-butoxynorbomadiene. Similarly, oxidation with dibenzoyl peroxide and CuBr leads to 7-benzyloxynorbomadiene. In both cases, when a 2-monodeuterated sample of norbomadiene is used, the deuterium is found distributed at all seven carbons in the product. Provide a mechanism which could account for this result. In what w s does this mechanism differ from the general mechanism discussed on pp. 724-725 ... 

Nitric oxide, 80 Nitrogen, 79 correlation with CO, 39 Nitromethane, 219 Nitrosome thane, 149 Nonbondmg orbitals, 5, 9, 28 Norbomadiene, 282... 

Besides the use of porphyrins as azomethinic ylide derivatives, the porphyrin macrocycle can also be used to generate porphyrinic nitrile oxides 55 (Scheme 17) <04RCB(E)2192>. Thus, the treatment of oxime 54 with /V-bromosuccinimide in the presence of triethylamine, led to the formation of nitrile oxide 55, which was trapped in 1,3-DC reactions with dimethyl maleate and 2,5-norbomadiene to afford 56 and 57, respectively. In the reaction with 2,5-norbomadiene, if an excess of 55 was used, then the corresponding bis-adduct was obtained in good yield. 

Polymeric isoxazolines were prepared by cycloaddition of nitrile oxides to norbomadiene followed by ring-opening metathesis polymerization (ROMP) <06PLM3292 06MM3147>. 

Bimolecular surface reactions reactants adsorption, 29 111-112 with single reactant, 29 108-109 1,1 -Binaphthyl, dehydrocyclization, 28 318 Binary oxides, 32 119 Binding energy, 32 160-162 chemisorbed sulfur, 37 281 hydrogen, sulfur effect, 37 295-296 shift, Pd, 37 62-64 ZnO/SiOj, 37 21-22 Binor-S, see Norbomadiene Biological systems, hydrogen in, activation of, 11 301... 

In a study of the addition of nitrosyl chloride or nitrosyl bromide to norbor-nene and norbomadiene, it was observed that (a) there was no structural rearrangement during the reaction, (b) a cis addition had taken place, (c) nucleophilic solvents such as ethanol or acetic acid were not incorporated in the products. These facts seem to speak against an ionic addition mechanism, while a free radical initiated by NO radicals was considered unlikely since nitric oxide is inactive toward norbomadiene. Therefore a four-center mechanism has been suggested [70], However, when a relatively simple, unstrained olefin such as A9-octalin was subjected to the reaction, only blue, crystalline, monomeric 9-nitroso-10-chlorodecalin was produced. This product had a trans configuration. Thus it is evident that the structure of the olefin has a significant bearing on the steric course of the addition [71]. 

In the Norsorex process, norbomadiene is polymerized by a ROMP type process. Polymers synthesized by ROMP have poor thermal stability and oxidative stability due to unsaturation of the main chain. They are used as thermoplastic resins or thermosetting resins. 

The process is induced photochemically and involves the single-electron transfer oxidation of cubane then completed with a backward electron transfer to the transient radical cations. A Li+ salt with a weakly coordinating anion is able to induce pericyclic transformations, including the rearrangement of cubane to cuneane, quadricyclane to norbomadiene, and basketene to Nenitzescu s hydrocarbon 392... 

The final example of the intramolecular 1,3-dipolar cycloadditions of nitrile oxides is the formation of the norbomadiene-derived tetracyclic adducts 146, described by Tam and co-workers (240,241). The nitrile oxide 145, formed from 144 by dehydration, can in principle give rise to four different cycloaddition products (three [2,3]-cycloaddition products). In practice, only diastereomer 146 was obtained. The reaction was used on substrates with a variety of different substituents (R=H, Me, hexyl, Cl, Br, C02Me, CH2OMe), and in these cases, yields ranging between 66-89% were obtained (Scheme 12.48). 

A Diels-Alder approach to varenicline was recently published by Dr. Reddy s Laboratories. Entry to a key bicyclic intermediate is achieved by an iodide-catalyzed Diels-Alder reaction of tetrabromo dimethyl pyrazine (47) with excess norbomadiene. Dihydroxylation of 48, oxidative cleavage, and reductive amination prepares N-p-methoxybenzyl varenicline (50), which is deprotected under transfer hydrogenation conditions to give varenicline (1) in 10% yield for the sequence.47 This approach continues the theme of building the piperidine of 1 through olefin oxidative cleavage and reductive amination, but by doing so late in the sequence however, the approach... 

The ubiquitous and reversible formation of radical cations in photoelectrochemical transformations allows pericyclic reactions to take place upon photocatalytic activation since the barriers for pericyclic reactions are often lower in the singly oxidized product than in the neutral precursor. For example, ring openings on irradiated CdS suspensions are known in strained saturated hydrocarbons [176], and formal [2 -I- 2] cycloadditions have been described for phenyl vinyl ether [ 177] and A-vinyl carbazole [178]. The cyclization of nonconjugated dienes, such as norbomadiene, have also been reported [179]. A recent example involves a 1,3-sigmatropic shift [180]. 

As shown in Table 6 and Figure 1, the oxidation potentials of 2-substituted norbomadienes (1), 2-substituted bicyclo[2.2.2]octa-2,5-dienes (2) and 4-substituted [2.2]paracyclophanes (3) clearly indicate that the transannular interaction between two double bonds contributes already at the stage of the first electron transfer. Namely, in compounds 1-3, the electron is transferred from the unsaturated bond which is not substituted by the electron-withdrawing group, Figure 1 shows the... 

Osmium tetraoxide has also been used in the oxidation of bicyclic and polycyclic dienes. Thus, oxidation of norbomadiene (26) in a stoichiometric reaction was found to yield the exo-cis diol exclusively. On the other hand, in the NMO catalytic system a mixture of the exo-cis and endo-cis products was reported. However, by use of the NMO catalytic procedure for the substituted norbomadiene 27, the exc-diol was formed exclusively at the sterically crowded unsubstituted double bond and this product was utilized in the synthesis of pentalenolactone. Somewhat surprisingly, oxidation of hexamethyl Dewar benzene (28) exclusively gave the endo-cis diol as sole product. The tricyclic compound 29 gave the usual c/s-diol oxidation product of one of the double bonds. ... 

A stepwise sequence of nucleophilic addition to the complexed norbomadiene followed by intramolecular alkene insertion was first observed with dichloro(norbornadiene)palla-dium(II) which, upon addition of methanol, only forms the normal adduct 11. Subsequent conversion with l,2-bis(triphenylphosphanyl)ethane (dppe), however, gave the nortricyclene complex 12. Reductive displacement of the alkyl ligand with lithium aluminum hydride or oxidative cleavage with halogens gave noncomplexed nortricyclene derivatives. ... 

Partial reduction of dichloro(norbomadiene)palladium with sodium borohydride at — 40 C gave an intermediate 25 which could not be isolated but was assumed to be a homoallyl complex which upon reductive cleavage gave norbornene, norbomane and nortricyclene in a ratio of 9 7 1, while oxidative decomplexation gave norbornenone and nortricyclenone in a 1 1 ratio. ... 

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