Ethyl 1-acetyl-1H-indazole-5-carboxylate was used as a raw material, which was dissolved in a mixed solvent consisting of concentrated hydrochloric acid (15 mL), water (15 mL) and ethanol (30 mL), and the reaction was stirred for 4 hours at room temperature. Upon completion of the reaction, the pH of the reaction mixture was adjusted to slightly basic with 25% ammonia. Subsequently, the alkalized mixture was extracted with chloroform. The organic phases were combined and purified by hexane crystallization. After completion of crystallization, the resulting crystals were collected by filtration and dried to give the final ethyl 5-indazolecarboxylate (6.45 g, 48% yield) as a light brown powder.
