[N+:1]([C:4]1[CH:5]=[C:6]2[NH:12][N:11]=[CH:10][C:7]2=[N:8][CH:9]=1)([O-])=O.N([O-])=O.[Na+].[CH3:17][C:18]1[C:23](N)=[CH:22][C:21]([N+]([O-])=O)=CN=1.[OH-:28].[Na+]>O.C(O)(=O)C.C(OCC)(=O)C>[O:28]1[CH2:21][CH2:22][CH2:23][CH2:18][CH:17]1[N:12]1[C:6]2[C:7](=[N:8][CH:9]=[C:4]([NH2:1])[CH:5]=2)[CH:10]=[N:11]16-Nitro-1H-pyrazolo[4,3-b]pyridine. A solution of sodium nitrite (2.163 g, 31.3 mmol) in water (20 mL) was added to a stirred solution of 2-methyl-5-nitropyridin-3-amine (4 g, 26.1 mmol) in acetic acid (70 mL). The resulting orange solution was stirred at room temperature for 16 h. The reaction was cooled to 0° C. and the reaction mixture was brought to pH=7 via addition of aqueous sodium hydroxide (6 M). Water and ethyl acetate were added. The resulting mixture was shaken in a reparatory funnel and the layers were separated. The organics were washed with water and brine, dried over magnesium sulfate, filtered, and concentrated on a rotary evaporator. The residue was triturated with diethyl ether. Solids were collected by vacuum filtration, washed with diethyl ether, and dried under high vacuum to give the desired product, as a dark orange solid (2.3 g, 14.01 mmol, 53.7% yield). 1H NMR (400 MHz, DMSO-d6) δ (ppm) 9.29 (d, J=2.34 Hz, 1H), 8.91 (br s, 1H), 8.59 (br s, 1H). MS (ESI) m/z 165.2 [M+1]+.
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