General procedure for the synthesis of 5-(pyridin-3-yl)-1H-pyrazole-3-carboxylic acid from ethyl 5-(pyridin-3-yl)-1H-pyrazole-3-carboxylate: sodium hydroxide (0.06 g, 15 mmol), ethyl 5-(pyridin-3-yl)-1H-pyrazole-3-carboxylate (1.763 g, 8 mmol), tetrahydrofuran (16 mL), methanol (15 mL) and water (8 mL) was stirred at 65 °C for 4 hours. After completion of the reaction, the solvent was removed under reduced pressure. The obtained residue was diluted with water and the solution was neutralized with cold aqueous hydrochloric acid (6 mol/L) to pH 5. The white precipitate was collected and washed with water to afford the crude product 5-(pyridin-3-yl)-1H-pyrazole-3-carboxylic acid (1.361 g, 90% yield). The crude product was purified by silica gel column chromatography.5-(Pyridin-3-yl)-1H-pyrazole-3-carboxylic acid was characterized as follows:IR (KBr, γ, cm^-1): 3423 (s, O-H stretching vibration), 1724 (s, C=O stretching vibration), 1573 (w), 1438 (w), 1389 (w), 1337 (m), 1292 ( m), 1243 (m), 762 (s), 703 (s), 636 (w).MS (ESI): m/z (%) = 233.8 [M+HCOOH-H]^-, 223.9 [M+Cl]^-, 188.1 [M-H]^-.
