Lewis acid-catalyzed intramolecular cyclization of N-1-(4-oxo-2,5-cyclohexadien-1-ylidene)-N-2- substituted-2,2,2-trifluoroethanimidamide (p-benzoquinone imine derivatives, 1) prepared by electrooxidation of N-(4-methoxyphenyli-N'-substituted-2,2 2-trifluoroethanimidamides 2 occurred to give 1-substituted-2-(trifluoromethyl)-6-hydroxybenzimidazoles 3. Alternatively, thermal cyclization of 1 gave spiro dienone diazacarbocycles 9 and 10, which were converted into diazepine 12 via a dienone-phenol rearrangement.
Kobayashi Masafumi, Uneyama Kenji, Hamada Noritaka, Kashino Setsuo, Tetrahedron Lett., 35 (1994) N 29, S 5235-5238