Acetic Anhydride → 7-chloro-1H-indazole-5-carbonitrile

To a solution of 4-amino-3-chloro-5-methylbenzonitrile (3.00 g, 18.0 mmol) in CHCl3 (50 mL) was added acetic anhydride (3.9 mL, 41.4 mmol). The mixture was stirred at room temperature overnight and then heated at reflux for 5 hours. The reaction mixture was cooled to room temperature and potassium acetate (530 mg, 5.40 mmol) and isoamyl nitrite (5.28 mL, 39.6 mmol) were added. The mixture was heated at reflux for 3 days. The reaction mixture was washed with saturated aqueous NaHCO3, dried over Na2SO4 and concentrated. To this was added methanol followed by water (25 mL) and 38% HCl (25 mL). The mixture was stirred at room temperature overnight. The reaction mixture was concentrated and the pH was adjusted to about 7. The solids were isolated by filtration and then washed with water (2×30 mL) and heptane (2×30 mL). Purify by Biotage chromatography (CH2Cl2-heptane (1:1)/MeOH gradient to afford 7-chloro-1H-indazole-5-carbonitrile was isolated as a white solid (585 mg, 18%).