General procedure for the synthesis of indazole-5-carbonitrile from 4-fluoro-3-formylbenzonitrile: 4-fluoro-3-formylbenzonitrile (25 g, 16.78 mmol) was dissolved in 100 mL of 85% hydrazine hydrate. The reaction mixture was stirred at room temperature for 24 hours. After completion of the reaction, the product was purified by column chromatography to afford 1H-indazole-5-carbonitrile (2.1 g, 87% yield). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6) and mass spectrometry (ESI): 1H NMR δ 13.60 (s, 1H), 8.42 (s, 1H), 8.27 (s, 1H), 7.73 (d, J = 8.6 Hz, 1H), 7.67 (d, J = 8.6 Hz, 1H); MS m/z (ESI): 144 [M + H]+.
