Triphenylene radical cation

The trimethylsilyloxy (TMSO) group is stable under the coupling conditions in acetonitrile (Table 12, number 6). After oxidative dimerization the TMS-ether can be mildly hydrolyzed (H+ and H2O) to the phenol or converted to a dibenzofuran. 1,2-Dialkoxybenzenes have been trimerized to triphenylenes (Table 5, numbers 7, 8). The reaction product is the triphenylene radical cation, which is reduced to the final product either by zinc powder or in a flow cell consisting of a porous anode and cathode [188]. Anodic trimerization of catechol ketals yields triphenylene ketals, which can function as a platform for receptors, for example, in an artificial caffeine receptor [190]. 

The novel arenium ion 95 was synthesized266 by one-electron oxidation of the triphenylene-based starting compound to form a radical cation which abstracted a chlorine atom with a concomitant rearrangement to yield the hexachloroantimonate salt. The arenium ion character is apparent from the 13C spectrum (three signals at 813C 212.9, 187.6, and 173.6) and from the bond distances, which are very close to those shown for ion 91. Cation 95 can be stored at room temperature for months. This exceptional stability was attributed to the annelation to the two bicyclo[2.2.2]octane units and the spiroconjugation effect of the fluorenyl moiety.267... 

Later the same authors61 published a study on the reactivities of a number of electrogenerated radical cations toward St and isobutyl vinyl ether (IBVE). The reactivity comparison was made among 9-phenylanthracene (9PA), 9,10-dimethyl-anthracene (DMA), 9,10-diphenylanthracene (DPA), 1,3,6,8-tetraphenylpyrene (TPP), rubrene (RU), triphenylene (TP), perylene (p). The stability of the ion radicals, in the absence of the monomers, is in the order ... 

DCB". Secondary electron transfer then occurs from the allylsilane D to ArH or the Jt-complexation of ArH wifli D, [ArH D]. The radical cation species D or [ArH D] reacts to produce the allyl radical, which reacts wifli /i-DCB to give the substitution product shown in Scheme 2. Aromatic hydrocarbons such as phenanthrene, naphthalene, triphenylene, and />-terphenyl (Table 3) are effective in the redox photosensitization in the photosubstitution of E)CB by allyltrimethylsilane. ... 

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). 

According to calculations (Dewar et al. 1956), triphenylene itself has position 2 as the most reactive one for classical reactions. For its cation-radical, the most reactive position is at C-1, along with the same position 2 (Perrin 1977). These predictions and experiments are in line with triphenylene cation-radical participation in nitration (Baker et al. 1955). 

Polymers 340-343 have a deep red or brown color probably related to the presence of conjugated polynuclear units. A similar color was noted in the polymers derived from cation-radical polymerization of 1,1 -binaphthyl and o-terphenyl. In these cases the color was attributed to the presence of cation-radicals of perylene and triphenylene structural units [193,201,203]. Perylene units are possible in polymers 340-343 (Fig. 46). 

The coelectrolysis of veratrole with anisole derivatives afforded in TFA-CH2CI2 good yields of aryl-substituted triphenylene derivatives (Table 4, number 9). Product formation probably occurs by initial coupling of the veratrole cation radical with anisole to an unsymmetrical dimer. This is followed by coupling of the dimer and intramolecular cyclization to the product. 

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