3-Oxo-2,3-dihydro-1hydro-indazole-5-carboxylic acid (1.5 g, 8.4 mmol) was suspended in methanol (17 mL). Concentrated hydrochloric acid (3.11 mL, 101 mmol) was added slowly and the reaction mixture was heated to 100 °C and refluxed for 6 hours. After completion of the reaction, the reaction solution was concentrated under reduced pressure to afford the white solid product methyl 3-hydroxy-1H-indazole-5-carboxylate (1.60 g, 99% yield). The product was detected by mass spectrometry (ESI) showing [M + H]+ peak of 193.1; 1H NMR (400 MHz, DMSO-d6, δ) data were as follows: 12.00 (br.s, 1H), 8.35 (s, 1H), 7.83 (dd, J = 8.9,1.7 Hz, 1H), 7.33 (dd, J = 8.9,7.7 Hz, 1H). 3.82 (s, 3H).
