Bicyclo 2.2.2 octa

Abbreviations acac, acetylacetonate Aik, alkyl AN, acetonitrile bpy, 2,2 -bipyridine Bu, butyl cod, 1,5- or 1,4-cyclooctadiene coe, cyclooctene cot, cyclooctatetraene Cp, cyclopentadienyl Cp, pentamethylcyclopenladienyl Cy, cyclohexyl dme, 1,2-dimethoxyethane dpe, bis(diphenyl-phosphino)ethane dppen, cis-l,2-bis(di[Atenylphosphino)ethylene dppm, bis(diphenylphosphino) methane dppp, l,3-bis(diphenylphosphino)propane eda,ethylenediamine Et,ethyl Hal,halide Hpz, pyrazole HPz, variously substituted pyrazoles Hpz, 3,5-dimethylpyrazole Me, methyl Mes, mesityl nbd, notboma-2,5-diene OBor, (lS)-endo-(-)-bomoxy Ph, phenyl phen, LlO-phenanthroline Pr, f opyl py, pyridine pz, pyrazolate Pz, variously substituted pyrazolates pz, 3,5-dimethylpyrazolate solv, solvent tfb, tetrafluorobenzo(5,6]bicyclo(2.2.2]octa-2,5,7-triene (tetrafluorobenzobanelene) THE, tetrahydrofuran tht, tetrahydrothicphene Tol, tolyl. 

Another application of catalyst 8 is to the reaction of acetylenic aldehydes [10c] (Scheme 1.18, Table 1.6). Two acetylenic dienophiles have been reacted with cyclo-pentadiene or cyclohexadiene to give bicyclo[2.2.1]heptadiene or bicyclo[2.2.2]octa-diene derivatives in high optical purity. A theoretical study suggests that this reaction proceeds via an exo transition state. 

Table 1. Preparation and Anionic Polymerization of Masked Disilene, 1-Phenyl-7,8-disila-bicyclo[2.2.2]octa-2,5-diene...

As shown in Table 6 and Figure 1, the oxidation potentials of 2-substituted norbornadienes (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... 

These results have been interpreted in terms of trans addition of mercuric ion and nucleophile where the attack of the mercuric ion takes place from the more hindered side of the diene molecule. A transition state 197, involving an endo attack of mercuric ion with some stabilization by coordination to the 8,9-ethylenic bond to the mercury atom, has been proposed to support the suggested mechanism. Analogously, and in sharp contrast to the results obtained167 in the mercuration of norbomadiene which reacts with mercury salts via the usual scheme of exo-syn addition, the principal pathway in the mercuration of bicyclo[2.2.2]octa-2,5-diene is the formation of endo-syn products (equation 165). 

Norbornadiene adds typical dienophiles in a homo-Diels-Alder reaction whereby, for example, the adduct 86 is obtained with tetra-cyanoethylene. Dimethyl acetylenedicarboxylate and dicyanoacetyl-ene add to barrelene (bicyclo[2.2.2]octa-2,5,7-triene) in a similar way. °... 

Dimethylamino-2.3,4,5-tetrafluo-ro- EI0b2, 267 (l-NR2-2,3,4,5-F4 - [Pg.863]

Cycloaddition of alkenes to the benzene ring does not occur when both molecules are in their ground electronic states. The reaction can only be brought about by photoexcitation of either of the two addends. Three types of photochemical cycloaddition of alkenes to benzene and its derivatives are presently known. Ortho photocycloaddition, also referred to as 1,2-photocycloaddition or [2 + 2] photocycloaddition, leads to bicyclo[4.2.0]octa-2,4-dienes. Meta photocycloaddition, also referred to as 1,3-photocycloaddition or [2 + 3] photocycloaddition, gives triyclo[3.3.0.02 8]oct-3-enes, also named l,2,2a,2b,4a,4b-hexahydrocyclo-propa[crf]pcn(alcnes. Para photocycloaddition, also referred to as 1,4-photocy-cloaddition or [2 + 4] photocycloaddition, results in bicyclo[2.2.2]octa-2,5-... 

Chang, S.-Y., Huang, S.-L., Villarante, N.R., and Liao, C.-C. (2006) Photochemical reactions of 1,3,3-trimethyl-bicyclo[2.2.2]octa-5,7-dien-2-ones. 

Complex 105 cydizes with DMAD to give the diastereomeric bound bicyclo[2.2.2]octa-trienes 109A and 109B in a 1 1 ratio (Scheme 14). Oxidation of these complexes liberates the corresponding triene 110 as well as the disubstituted anisole 111, presumably generated with acetylene from the cycloreversion of 110. 

A [2 + 2 + 2]-cycloaddition reaction is also known, facilitated by Ni(cod)2 or a cobalt catalyst. " " [2 + 2 + 1]-Cycloaddition is known.A cobalt catalyst is used for a [4- -2- -2]-cycloaddition of 1,3-butadiene and bicyclo[2.2.2]octa-2,5-diene. " " " Eight-membered rings are products by a rhodium catalyzed [4- -2- -2]-cycloaddition. " " Chromium catalysts are available for [6-1-4]-cycloadditions... 

If two vicinal carboxyl groups are present, the Kolbe electrolysis may result in the introduction of a double bond this has been used in the transformation of 2-aza-3-oxo-bicyclo[2.2.2]oct-7-en-5,5-dicarboxylic acid to 2-aza-bicyclo[2.2.2]octa-5,7-dien-3-one [456]. 

To a solution of tetracyanoethene (0.35 g, 2.7 mmol) in benzene (3 mL) was added bicyclo[2.2.2]octa-2,5-diene (0.50 g, 4.7 mmol). The resulting orange-amber colored solution was refluxed with stirring for 30 h (after 6 h, the solution had become noticeably darker and a precipitate had formed) and then cooled in an ice bath. The crystals were suction filtered to give 0.48 g (75%) of a grayish-brown solid, which gave white needles on recrystallization from benzene, mp 244-245 C. The overall yield of adduct was about 85% based on workup of material from the mother liquors. 

Reaction of 4-phenyI-4/f-l,2,4-triazole-3,5-dione with bicyclo[2.2.2]octa-2,5-diene and bi-cyclo[3.2.2]nona-6,8-diene, carried out in acetone or dioxane, gave the expected homo-Diels-Alder adducts, which were used as starting materials for further syntheses. ... 

Bicyclo[2.2.2]octa-2,5-diene and tricyclo[3.2 2.0 " ]nona-6,9-diene derivatives react with palla-dium(II) acetate in the presence of sodium acetate in anhydrous benzene to give the formal homo-Diels-Alder cycloadducts 16 and 17 of dehydrobenzene. ... 

One of the first examples of the di-7t-methane rearrangement was found in the photochemical conversion of bicyclo[2.2.2]octa-2,5,7-triene (barrelene, 1) to tricyclo[5.1.0.0 ]octa-2,5-diene (semibullvalene, 2). ... 

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