[H-].[Na+].[NH2:3][C:4]1[C:8]([C:9]([O:11][CH2:12][CH3:13])=[O:10])=[CH:7][NH:6][N:5]=1.Br[CH2:15][C:16](=[O:20])[CH2:17][CH2:18][CH3:19]>CN(C=O)C>[NH2:3][C:4]1[N:5]([CH2:15][C:16](=[O:20])[CH2:17][CH2:18][CH3:19])[N:6]=[CH:7][C:8]=1[C:9]([O:11][CH2:12][CH3:13])=[O:10]To a mixture of sodium hydride (60% dispersion in mineral oil, 0.8 g) in DMF (50 ml) was added ethyl 3-amino-pyrazol-4-carboxylate (2.0 g) and the reaction mixture was stirred at room temperature for 15 minutes. After addition of 1-bromo-2-pentanone (4.0 g), the mixture was stirred at room temperature for 13 hours. The reaction mixture was concentrated to dryness, and the residue was dissolved in ethyl acetate-water. The organic layer was washed with water, dried and concentrated to dryness. The resulting yellow syrup was purified by column chromatography on silica gel to give pale yellow prisms (1.4 g, 45%).
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