Example 112A Synthesis of 3-chloro-5-nitro-1H-indazole: Sodium hydroxide (5.00 g, 125 mmol) was dissolved in water (150 mL), 5-nitroindazole (5.00 g, 30.7 mmol) was added, and the mixture was heated until a red solution formed. The reaction mixture was cooled in an ice water bath for 15 minutes, followed by the slow addition of sodium hypochlorite solution (60.0 mL, 5.25%, 45.0 mmol). The reaction mixture was stirred at 0 °C for 5 h. After completion of the reaction, the pH was adjusted with dilute hydrochloric acid to 7. The reaction mixture was extracted with ethyl acetate, the organic layers were combined, washed with water and concentrated under reduced pressure. The residue was purified by fast column chromatography to afford the target compound 3-chloro-5-nitro-1H-indazole (5.5 g, 92% yield). The product was identified by 1H NMR (300 MHz, DMSO-d6): δ 7.78 (m, 1H), 8.28 (m, 1H), 8.61 (m, 1H); mass spectrum (DCI/NH3) showed m/z 197 [M + H]+.
