Synthesis
The general procedure for the synthesis of 1-nitropyrazole from pyrazole was as follows: first, the nitroxide was prepared by slowly mixing acetic anhydride with fuming nitric acid at a volume ratio of 5.5:1 under ice-water bath conditions. Subsequently, the nitroxide and the acetic acid solution of pyrazole were fed into the microchannel reactor at a precisely controlled flow rate (0.1 mL/min for the pyrazole acetic acid solution), respectively, via a high-pressure delivery system. In this process, a constant flow pump was used to ensure that the molar ratio of nitric acid to pyrazole was strictly controlled at 1.1:1. The reaction was carried out in the microchannel reactor at a temperature maintained at 45-70 °C to achieve instantaneous mixing and reaction of the two liquids. Upon completion of the reaction, the reaction liquid was quenched by pouring it into crushed ice and the products were separated by filtration. The product was washed with ice water and dried under vacuum to give the final N-nitropyrazole. The yield and purity data of the products are detailed in Table 1 and Figure 2.
References
[1] Patent: CN108570010, 2018, A. Location in patent: Paragraph 0035; 0036; 0037; 0038; 0041-0070
[2] Archiv der Pharmazie, 1995, vol. 328, # 4, p. 349 - 358
[3] ChemPlusChem, 2018, vol. 83, # 8, p. 804 - 811
[4] Journal of Chemical Research - Part S, 1996, # 5, p. 244 - 245
[5] Beilstein Journal of Organic Chemistry, 2013, vol. 9, p. 1517 - 1525
