Synthesis of perfluoroalkyl-substituted 4,5-dihydro-3H-pyrazolo[4,3-a]phenazines and tetrahydroimidazo[4,5-e]indazoles

Oxidation of 1-aryl-3-perfluoroalkyl-6,7-dihydro-1H-indazol-4(5H)-ones with selenium dioxide in the presence of sulfuric acid in glacial acetic acid, followed by treatment of 6,7-dihydro-1H-indazole-4,5-diones thus obtained with an equimolar amount of o-phenylenediamine in ethanol or with a mixture of 4-fluorobenzaldehyde and ammonium acetate in acetic acid, gave 3-aryl-1-perfluoroalkyl-4,5-dihydro-3H-pyrazolo-[4,3-a]phenazines and 6-aryl-2-(4-fluorophenyl)-8-perfluoroalkyl-1(3),4,5,6-tetrahydroimidazo[4,5-e]indazoles, respectively.