[N+:1]([C:4]1[CH:9]=[CH:8][C:7]([N:10]2[C:22](=[O:23])[C:13]3[N:14]=[N:15][C:16]4[CH:17]=[CH:18][CH:19]=[CH:20][C:21]=4[C:12]=3[NH:11]2)=[CH:6][CH:5]=1)([O-])=O.[Cl-].[NH4+].C(=O)([O-])[O-].[K+].[K+]>C(O)C.O.[Fe]>[NH2:1][C:4]1[CH:5]=[CH:6][C:7]([N:10]2[C:22](=[O:23])[C:13]3[N:14]=[N:15][C:16]4[CH:17]=[CH:18][CH:19]=[CH:20][C:21]=4[C:12]=3[NH:11]2)=[CH:8][CH:9]=1
2-(4-nitrophenyl)-1,2-dihydro-3H-pyrazolo[4,3-c]cinnolin-3-one (11.4 g, 37.2 mmol) was suspended in a mixture of ethanol (100 ml) and water (100 ml). Iron powder (11.1 g, 200 mmol) and ammonium chloride (5.34 g, 100 mmol) were added. The mixture was heated to 80° C. overnight, cooled to room temperature and basified with potassium carbonate to pH 9-10. The solids were removed by filtration through a pad of Celite®. The filtrate was extracted with n-butanol (2×200 ml). The combined organic phases were concentrated under vacuum to give a dark red solid. The solid was triturated with methanol (100 ml), filtered and dried under vacuum. The title compound was isolated as a dark red powder (5.58 g, 20.1 mmol, 57%). LCMS: m/z 278 [M+H]+.
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