Z. S. Morkovnik

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.

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.

Perchlorate of the phenoxazine cation radical

We were able to develop a convenient method for the oxidation of phenoxazine (I) that makes it possible to isolate the perchlorate salt (II) of the phenoxazine cation radical, the existence of which in solutions has been demonstrated by EPR spectroscopy. For this, we carefully ground an equimolar mixture of phenoxazine with ferric perchlorate nonhydrate in a small amount of 57% perchloric acid. The dark-red precipitate of II was removed by filtration and washed with the minimum amounts of acetone and ether to give the product in 53% yield. The results of elementary analysis of the salt are in agreement with the empirical formula. Treatment of a solution of perchlorate II in acetonitrile with zinc dust gives phenoxazine. The EPR spectrum of a solution of II in acetonitrile (i0 -4 mole/liter) consists of a quartet of lines (aHNH ~ a N ~ 7.6 Oe). The absorption spectrum in the visible region contains a band with %max 383, 409, and 530 nm.