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General procedure for the synthesis of 1-benzyl-4-cyanopyrazole from 1-phenyl-1H-pyrazole-4-carboxaldehyde: 1-benzyl-1H-pyrazole-4-carboxaldehyde (18.6 g, 0.1 mol), sodium bromate (7.5 g, 0.05 mol), and 200 g of acetic acid were mixed at room temperature, followed by the slow addition of 50 g of 25% aqueous ammonia solution. To the reaction mixture was added 300 mL of water, heated to 90 °C, exothermic during the reaction, the reaction temperature was maintained at 100 °C, and the reaction was refluxed for 1 h until 1-benzyl-1H-pyrazole-4-carbaldehyde was fully reacted. After completion of the reaction, it was cooled to room temperature and the reaction solution was poured into ice water for quenching and dilution. Subsequently, the reaction solution was neutralized with a suitable base, the organic phase was extracted with dichloromethane, dried over anhydrous sodium sulfate and concentrated under reduced pressure. Finally, the target product 1-benzyl-4-cyanopyrazole 16.6 g was obtained in 91% yield and ≥98% purity by decompression distillation and recrystallization purification.

[1] Patent: CN108707113, 2018, A. Location in patent: Paragraph 0032
[2] Heterocycles, 1988, vol. 27, # 10, p. 2443 - 2458
[3] Heterocycles, 1988, vol. 27, # 10, p. 2443 - 2458