[N+:1]([C:4]1[NH:8][N:7]=[C:6]([C:9]([O:11][CH3:12])=[O:10])[CH:5]=1)([O-:3])=[O:2].C(=O)([O-])[O-].[K+].[K+].[Br:19][CH2:20][CH2:21]Br>CC(C)=O>[Br:19][CH2:20][CH2:21][N:7]1[C:6]([C:9]([O:11][CH3:12])=[O:10])=[CH:5][C:4]([N+:1]([O-:3])=[O:2])=[N:8]1To a solution of methyl 5-nitro-1H-pyrazole-3-carboxylate (1 g, 5.84 mmol) in acetone (30 mL) was added potassium carbonate (4.04 g, 29.2 mmol) and 1,2-dibromoethane (3.29 g, 1.51 mL, 17.5 mmol) and the resulting solution heated to reflux for 2 h. The resulting mixture was cooled to 0° C. filtered and concentrated and the residue purified by flash chromatography (silica gel, 60 g, 20% to 40% ethyl acetate in hexanes) to give methyl 1-(2-bromoethyl)-3-nitro-1H-pyrazole-5-carboxylate (1.03 g, 63%) as a white solid.
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