Uncommon condensations of 1,2,3-triketone 2-oximes with o-phenylenediamine

A condensation of 2-hydroxyimino-5,5-dimethylcyclohexane-1,3-dione, ninhydrin oxime and 3-hydroxyiminopentane-2,4-dione with o-phenylenediamine in the presence of CF₃COOH provided 6,6-dimethyl-6,7-dihydroquinoxalino-[2,3-a]phenazine, benzimidazo[2′,1′:1,2]isoquino[3,4-b]quinoxaline, and 2-acetyl-3-methylquinoxaline oxime, respectively. An ability to form stacking dimers was found for the second product.