[N+:1]([C:4]1[CH:5]=[N:6][NH:7][CH:8]=1)([O-:3])=[O:2].C[O:10][C:11](=[O:15])[CH2:12][CH2:13]Br.C(=O)([O-])[O-].[K+].[K+].[OH-].[Li+]>CN(C=O)C.CO>[N+:1]([C:4]1[CH:5]=[N:6][N:7]([CH2:13][CH2:12][C:11]([OH:15])=[O:10])[CH:8]=1)([O-:3])=[O:2]4-Nitro-1H-pyrazole (0.50 g, 4.4 mmol) was dissolved in DMF (5 mL). After addition of methyl-3-bromopropionate (0.72 mL, 1.5 eq) and potassium carbonate (0.92 g, 1.5 eq), the reaction mixture was stirred at 50° C. for 3 h, then partitioned between water and DCM. The aqueous phase was extracted with DCM, the combined organic phases dried over sodium sulfate and evaporated. The residue was hydrolyzed at rt over 30 min with lithium hydroxide (3M, aqueous) (4.4 mL, 3 eq) in methanol (5 mL) and the reaction mixture evaporated to dryness to afford 3-(4-nitro-1H-pyrazol-1-yl)propanoic acid in a quantitative yield.
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