A) Synthesis of methyl 1H-pyrazole-4-carboxylate: 1H-pyrazole-4-carboxylic acid (4.00 g) was dissolved in 4M HCl/methanol solution (150 mL) and the reaction was stirred overnight at room temperature. After completion of the reaction, the solvent was removed by rotary evaporation at room temperature. The product was dried under reduced pressure to give the title compound 1H-pyrazole-4-carboxylic acid methyl ester (5.0 g, white solid). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 3.72 (3H, s, -OCH3), 8.09 (2H, s, pyrazole ring-H), 11.62 (1H, s, -NH).
