Biphenylene cation

Biphenylene cation radicals and dications have also been observed on electrochemical reduction of substituted biphenylenes. The e.s.r. spectrum of benzocyclo-butadienequinone radical anion has been reinterpreted and the observed coupling constants agree well with Hiickel and McLaddon MO calculations. ... 

We then focused our attention to the cationic species generated from a series of condensed aromatics fully annelated with BCO units. Newly synthesized naphthalene 12 (17), anthracene 13 (18), biphenylene 14 (19), and fluorene 15 (20) all underwent smooth one-electron oxidation by the use of 1.5... 

For instance, nitration of naphthalene, azulene, biphenylene, and triphenylene proceeds preferentially in positions with the greatest constant of hyperfine splitting at the hydrogen atom in ESR spectra of corresponding cation-radicals. The constant is known to be proportional to the spin density on the carbon atom bearing the mentioned hydrogen. It is important, however, that the same orientation is also observed at classical mechanism of nitration in cases of naphthalene, azulene, and biphenylene, but not triphenylene (see Todres 1985). 

Loss of ethylene and subsequent formation of the stable 3//-pyrrolinine cation dominates the mass spectrum of 2,3,4,5-tetrahydro-l//-l-benzazepine <75OMS(10)992). Biphenylene (m/e 152), acridinium cation (m/e 179) and fluorene cation (m/e 165) are the major fragments in the mass spectra of dibenz[T>,/]azepines (74CJRV101). 

Many aromatic compounds have considerable resonance stabilization but do not possess a benzene nucleus, or in the case of a fused polycyclic system, the molecular skeleton contains at least one ring that is not a benzene ring. The cyclopentadienyl anion C5HJ, the cycloheptatrienyl cation C7H+, the aromatic annulenes (except for [6]annulene, which is benzene), azulene, biphenylene and acenaphthylene (see Fig. 14.2.2(b)) are common examples of non-benzenoid aromatic hydrocarbons. The cyclic oxocarbon dianions C Of (n = 3,4,5,6) constitute a class of non-benzenoid aromatic compounds stabilized by two delocalized n electrons. Further details are given in Section 20.4.4. 

To date the mercurated arene radical cation is known for biphenylene [87], ace-naphthene, pyracene, hexahydropyrene, triptycene, p-terphenyl, tetramethylnaph-thopyran, anthracene, dibenzodioxin [89], and 4-tert-butylanisole [88]. In certain cases multiple mercuration is observed, for example in case of diphenylene [87] and dibenzodioxin [89]. Mercuration causes a decrease in -value and always occurs at the site where the local coefficient of the Huckel HOMO of the hydrocarbon is greatest, and there is a constant ratio of about 20.6 between the hyperfine couplings by the Hg [l, abundance 16.84 %) which has been introduced, and by the proton which has been displaced [89]. EPR spectroscopic evidence is reported for 8, 9, 10, 11, 12, 13, 14, 15 and 16 as new examples of recently recognized alternative mechanism of arene mercuration in which collapse of ArH +Hg(TFA)2 radical ion pair leads to arylmercury trifluoroacetate ArHg(TFA) + [90]. 

Biphenylene, homo, cation, 231 Biphenylene, nor, anion, 231 Biphenylenequinones, 229 Bicyclononatetraenide salts, 269 Bis (cyclooctatctraeno)benzene, dianion, 408... 

The norbiphenylene anion (XXXIII) and homobiphenylene cation (XXXIV) are isoelectronic with biphenylene. 

The enantioselective completely intramolecular [2 + 2 + 2] cycloaddition also furnishes Cz-symmetric axially chiral biaryls. Shibata et al. reported the cationic rhodium(I)/tol-BINAP complex-catalyzed enantioselective [2 + 2 + 2] cycloaddition of symmetric hexaynes 58 to give Cz-symmetric axially chiral biaryls 59 with good yields and ee values (Scheme 9.21) [21]. This is the first example of an axially chiral bis(biphenylene) skeleton. 

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