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The general procedure for the synthesis of methyl 5-amino-1H-pyrazole-3-carboxylate from methyl 5-nitro-1H-pyrazole-3-carboxylate was as follows: methyl 5-nitro-1H-pyrazole-3-carboxylate (22.35 g, 130.61 mmol) was dissolved in a solvent mixture of 160 mL tetrahydrofuran (THF) and 160 mL glacial acetic acid. Subsequently, 10% palladium-carbon catalyst (Pd-C, 4.36 g) was added and the reaction was stirred at room temperature in a hydrogen atmosphere for 6 days. Upon completion of the reaction, the catalyst was removed by diatomaceous earth filtration and the solvent was evaporated under reduced pressure. The crude product was dissolved in 800 mL of dichloromethane, 200 g of sodium bicarbonate was added, filtered and the solvent was again evaporated under reduced pressure. This operation was repeated until there was no acetic acid odor. Methyl 5-amino-1H-pyrazole-3-carboxylate was finally obtained in high yield (16.91 g, 91.7% yield).

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