A. N. Suslov

One-electron oxidation and triphenylmethylation of benzimidazolines by the triphenylmethyl cation

With triphenylmethyl perchlorate (tetrafluoroborate) 1, 2, 2, 3-tetrasubstituted benzimidazolines undergo electrophilic triphenylmethylation at position 5. In further reaction with the electrophilic agent the obtained 5-triphenylntethylbenzimidazolines are converted into radical-canons. They undergo a similar transformation during the action of silver perchlorate and molecular oxygen. The results from investigation of the radicalcations by ESR and PMR are given.

Investigation of the reaction of 1,2,3-trimethyl-2-phenylbenzimidazoline with dehydrogenating reagents by EPR spectroscopy

The reaction of 1,2,3-trimethyl-2-phenylbenzimidazoline with a number of reagents that manifest dehydrogenating properties with respect to benziraidazolines was studied by EPR spectroscopy. These reagents convert 1,2,3-trimethyl-2-phenylbenzimidazoline to a relatively stable cation radical. The mechanism of the dehydrogenation of benzimidazolines is discussed taking into account the established facts.

Electron transfer as the initiating stage of dehydrogenation of benzimidazolines by the triphenylmethyl cation

We consider a radical-ion mechanism for dehydroaromatization of benzimidazolines by triarylmethyl cations, including as the initial step electron transfer from the hydroheteroaromatic compound to the electrophilic reagent. We draw the conclusion that there is significant weakening of the C(2)-H bond in the benzimidazoline radical cation formed in this stage.

Heterocyclic analogs of pleiadiene 61. 2-cyano- and 2-carbamoylperimidines

Treatment of 1-R-2 chloroperimidines with potassium or sodium cyanides in DMSO solution leads to facile substitution of the chlorine atom by the CN group and formation of previously unknown 1-R-2-cyanoperimidines. The latter upon heating in polyphosphoric acid are converted to 1-R-2-carbomoylperimidines in good yield.

PMR study of the degenerate electron transfer between 1,2,3-trimethyl-2-phenylbenzimidazoline and its cation radical

The degenerate electron transfer (electron exchange) between 1,2,3-trimethyl-2-phenylbenzimidazoline and the perchlorate of its radical cation has been studied by PMR in deuteriated aceonitrile. We have determined rate constants and activation parameters for this process, and also some hyperfine interaction (HFI) constants for the cation radical, inaccessible by ESR measurements.

Stable biradical in the benzimidazoline series, containing two cation-radical fragments with strong exchange interactions

A large number of uncharged stable biradicals are known [i]; there have been practically no reports, however, of biradicals containing two cation-radical fragments [bi(cationradicals)]. The only reported examples of radicals of this type have been polymeric viologens containing two or more unpaired electrons, in which the cation-radical functional groups are composed of nonaromatic y,y-dipyridylidene units [2]~ The exchange interaction between the unpaired electrons in this class of radicals is negligible; thus, their EPR spectra do not differ from the spectra of the corresponding viologen monoradicals. Viologenic biand poly(cation-radicals) are formed upon reduction of polypyridinium salts [2]. It is assumed that two-electron oxidation of compounds of the type R-X-R, in which the R groups are more readily ionized than the bridging group X, should provide a more general method for the preparation of hi(cation-radicals). We succeeded in carrying out this type of reaction in the case of 1,4-di(l,2,3-trimethylbenzimidazolinyl-2)benzene (I), * which contains two benzimidazoline functional groups linked by a nonconjugating p-phenylene bridge.