Synthesis
Step 1: To a mixed solution of 5.0 g (32.65 mmol) of 4-nitrophenylhydrazine and 9.10 mL (65.3 mmol) of N,N-diethylethylamine in 90 mL of ethanol was added 3.987 g (32.65 mmol) of ethoxymethylene malononitrile. The reaction mixture was stirred under reflux conditions overnight and subsequently cooled to room temperature. The reaction solution was concentrated and the residue was dissolved in dichloromethane, washed sequentially with water and brine, dried over anhydrous sodium sulfate and concentrated. The resulting solid was treated with hexane, filtered and dried under vacuum to afford 7.024 g (91% yield) of the target product 5-amino-1-(4-nitrophenyl)-1H-pyrazole-4-carbonitrile, which could be used in the next reaction without further purification.
References
[1] Patent: WO2013/182612, 2013, A1. Location in patent: Page/Page column 146
[2] European Journal of Medicinal Chemistry, 2008, vol. 43, # 4, p. 771 - 780
[3] Journal of Medicinal Chemistry, 1991, vol. 34, # 9, p. 2892 - 2898
[4] Organic and Biomolecular Chemistry, 2007, vol. 5, # 17, p. 2758 - 2761
[5] RSC Advances, 2015, vol. 5, # 68, p. 55179 - 55185
