The general procedure for the synthesis of 3-pyridinecarbohydrazide from methyl nicotinate was as follows: accurately weigh methyl 3-pyridinecarboxylate (2.74 g, 20 mmol) in a 50 mL round-bottomed flask, add anhydrous ethanol (15 mL), and stir at room temperature until the solid was completely dissolved. Subsequently, 80% hydrazine hydrate (30 mmol) was slowly added dropwise and immediately a large amount of needle-like white solid was observed to precipitate. The reaction mixture was continued to be stirred at room temperature for 3 h. Upon completion of the reaction, diafiltration was carried out and the solid was washed with a small amount of ethanol, resulting in 2.56 g of white needle-like crystals in 93.2% yield.
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