Example 1: General procedure for the synthesis of 5-chloro-1-methyl-4-nitro-1H-pyrazole from 1-methyl-4-nitropyrazole
(a) Synthesis of 5-chloro-1-methyl-4-nitro-1H-pyrazole
A THF solution of lithium bis(trimethylsilyl)amide (1.0 M, 65 mL, 65 mmol) was slowly added dropwise to a solution of dichloromethane (120 mL) containing 1-methyl-4-nitro-1H-pyrazole (5.50 g, 43.3 mmol) and hexachloroethane (10.54 g, 44.5 mmol) at 25 °C. The reaction mixture was stirred continuously at 25 °C for 60 min, followed by quenching the reaction with 1 mL of water. The mixture was concentrated to dryness and the residue was washed sequentially with 50 mL of water, saturated NaHCO3 solution (2 x 30 mL) and 30 mL of brine, and finally dried under vacuum to give 6.50 g of the target product in 93% yield.
MS(ESI) m/z: 162.0 [M+H]+.
1H NMR (500MHz, CDCl3) δ: 8.15 (s, 1H), 3.92 (s, 3H).
