[CH:1]1[CH:2]=[CH:3][C:4]([CH2:7][C:8]2[NH:12][CH2:11][CH2:10][N:9]=2)=[CH:5][CH:6]=1.F[C:14]1[CH:19]=[C:18]([F:20])[CH:17]=[CH:16][C:15]=1[N+:21]([O-])=[O:22].C(=O)([O-])[O-].[K+].[K+]>C(O)(C)C>[F:20][C:18]1[CH:19]=[C:14]2[C:15]([N+:21]([O-:22])=[C:7]([C:4]3[CH:5]=[CH:6][CH:1]=[CH:2][CH:3]=3)[C:8]3[N:9]2[CH2:10][CH2:11][N:12]=3)=[CH:16][CH:17]=1A mixture of tolazoline (40 g, 0.25 mol), 2,4-difluoronitrobenzene (39.75 g, 0.25 mol) and potassium carbonate (17.26 g, 0.125 mol) in isopropanol (500 ml) was heated to 50° C. for a period of two days. The solvent was removed in vacuo from the mixture and the residue was dissolved in dichloromethane. The resulting solution was filtered and the solvent removed in vacuo to yield a yellow solid which was chromatographed on silica gel using 2% methanol/chloroform as the eluent to yield 1,2-dihydro-8-fluoro-4-phenylimidazo[1,2-a]quinoxaline 5-oxide (38.5 g) as an orange solid, having a m.p. 188°-193° C., (Found: C, 68.07; H 4.23; N 14.82%; C16H12FN3O requires C 68.33; H 4.27; N 14.95%) and represented by the structural formula ##STR14##
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