General procedure for the synthesis of 3-chloro-1-methyl-4-nitro-1H-pyrazole from 3-chloro-1-methyl-1H-pyrazole: 3-chloro-1-methyl-1H-pyrazole (4.0 g, 34 mmol) was dissolved in concentrated hydrochloric acid and stirred. Fuming nitric acid (3.6 g, 120.0 mmol) was slowly added dropwise to sulfuric acid (4.0 mL) at 0 °C, followed by continuous stirring of the reaction mixture for 6 h at room temperature. Upon completion of the reaction, the reaction was quenched slowly with ice water, at which time a white solid precipitated. The solid product was collected by filtration and dried under vacuum to give 3-chloro-1-methyl-4-nitro-1H-pyrazole (3.0 g, 54% yield) as a final white solid. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 8.16 (s, 1H), 3.94 (s, 3H).
