Synthesis
General procedure for the synthesis of 3-amino-1H-indazole-6-carboxylic acid from 4-cyano-3-fluorobenzoic acid: 4-cyano-3-fluorobenzoic acid (500 mg, 3.0 mmol) was dissolved in n-butanol (9 mL), followed by the addition of hydrazine monohydrate (0.5 mL, 10 mmol). The reaction mixture was heated to 110 °C and the reaction was stirred at this temperature overnight. Upon completion of the reaction, the mixture was cooled to room temperature and the precipitate precipitated was collected by filtration. The resulting solid was dissolved in 1 N aqueous sodium hydroxide (2 mL) and extracted with ethyl acetate (2 x 2 mL) to remove organic impurities. Subsequently, the aqueous phase was acidified with 1 N aqueous hydrochloric acid to pH=4, at which point the target product began to precipitate. The precipitate was collected by filtration and dried under vacuum to yield 3-amino-1H-indazole-6-carboxylic acid (140 mg, 26% yield) as a red solid. The product was confirmed by ESI mass spectrum (M+H+ m/z 178.2) and further characterized by 1H NMR (400 MHz, CD3OD): δ 7.99-8.01 (m, 1H), 7.73 (dd, J = 8.4, 0.8 Hz, 1H), 7.61 (dd, J = 8.5, 1.3 Hz, 1H).
