Benzobicyclo octadienes

Electrostatic interactions become prominent in reactions with rigid alkenes, for example 7-isopropylidenebenzonorbornene106 or benzobicyclo[2.2.2]octadiene.107... 

A cyano group as substituent at C2 of benzonorbornadienes or benzobicyclo[2.2.2]octadienes 65 (X = CH2, CH2CH2) induces full regiospecificity, such that bridging occurs exclusively at the nonsubstituted olefinic carbon atom. 

Dehydrogenation. The most convenient route to benzobicyclo[2.2.2]octadiene (3) involves dimerization of cyclohexa-1,3-diene (1) to dicyclohexadiene (2). The reaction is best carried out by heating the monomer at 178-186° in a stainless steel autoclave for 24 hours. The dimer is then dehydrogenated to the desired product (3) with chioranil in xylene at 130-140°. Lower yields are obtained with DDQ in... 

Benzaldehyde, 100, 105, 154, 175, 336 Benzamide, 320 Benzene, 134, 154, 198, 286 Benzenesulfenyl chloride, 182 Benzenesulfinic acid sodium salt, 18 Benzenesulfonamide, 18 Benzenesulfonyl azide, 17—18 Benzenesulfonyl bromide, 18 Benzenesulfonyl chloride, 17 N-Benzenesulfonylformimidic acid ethyl ester, 18-19 Benzenethiol, 182 Benzhydrol, 238 Benzil, 312 Benzimidazole, 126 2,1-Benzisothiazole, 290 Benzobicyclo[2.2.2]octadiene, 46 Benzocyclobutadiene, 227 Benzohydroquinones, 60 Benzoic acid, 175... 

In the derivatives of benzobicyclo[2,2,2]octadiene the exo side is spatially more accessible for the attack on the sp -hybridized bridge carbon atom than the endo side In compound 296 the exo side is also sterically more accessible, as found from the results of cis-synchronous reactions Yet the electrophilic attack... 

One of the important advantages of using benzobjcyclooctene models in comparison with bicycloheptene ones is the relative ease of establishing the intermediate formation of a classical or nonclassical carbocation by the stereochemistry of the products formed. It is clearly seen from the chlorination of benzobicyclo[3,2,l]-octadienes. If the chlorination of derivatives of 6,7-tetrafluorobenzobicyclo[3,2,l]-octadiene first yields an exo-halogenonium ion, then the participation of the aromatic ring and of the o-bond 1-7 turns out to be effective enough to direct the... 

These results show the advantages of the benzobicyclo[2,2,2]octadiene and the -octene series in studying solvolysis reactions over the norbomane derivatives. When these models are used the exo and endo isomers yield different reaction mixtures which precludes the intermediate formation of a classical cation with the same skeleton. If this is formed at the stage of reaction proceeding along the k, route it results in products with a skeleton other than that of the compounds formed in the k processes. 

Solvolyses of 8-X-3,4-tetrafluorobenzobicyclo[3,2,l]-octadienes and -octenes (X = leaving group) have been reported the syn-epimers react with retention of the skeleton and stereochemistry at C-8 by way of the non-classical carbonium ion intermediate, whereas the anti-compounds yield products with the benzobicyclo-[3,3,0]octane structure, presumably by a classical ion pathway. Although the epimeric tosylates (124) and (125) are solvolysed at different states and show different sensitivities to solvent variation, they produce the same product mixture, comprising... 

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