CC(C)([O-])C.[K+].[CH3:7][N:8]1[C:12]([N+:13]([O-:15])=[O:14])=[CH:11][CH:10]=[N:9]1.[CH2:16]([Cl:18])[Cl:17]>CN(C=O)C>[Cl:17][CH:16]([Cl:18])[C:11]1[CH:10]=[N:9][N:8]([CH3:7])[C:12]=1[N+:13]([O-:15])=[O:14]To a solution of potassium tert-butoxide (157 ml, 11.0M in THF) and anhydrous DMF (40 ml) at −78° C. was added a mixture of 1-methyl-5-nitro-1H-pyrazole (5.0 g, 39 mmol) in anhydrous methylene chloride (3.5 mL) and anhydrous DMF (25 mL) via dropwise addition. The reaction was stirred at −78° C. for 30 minutes and quenched by the careful addition of acetic acid (20 mL) in methanol (40 mL). The resulting mixture was allowed to warm to room temperature and poured into ice-water and extracted with ethyl acetate. The organic phase was washed with water and brine and dried over by sodium sulfate. Chromatography on silica gel with hexanes and ethyl acetate (3:1→2:1) gave 1.47 g of 4-dichloromethyl-1-methyl-5-nitro-1H-pyrazole (18%): 1H NMR (300 MHz, CDCl3) δ 7.88 (s, 1H), 6.85 (s, 1H), 4.23 (s, 3H); MS (m/e): 210.2 (M+1).
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