[Br:1][C:2]1[N:6]([C:7]([CH3:10])([CH3:9])[CH3:8])[N:5]=[CH:4][C:3]=1[C:11]([O:13]CC)=[O:12].[OH-].[Na+]>C(O)C.C1COCC1>[Br:1][C:2]1[N:6]([C:7]([CH3:8])([CH3:9])[CH3:10])[N:5]=[CH:4][C:3]=1[C:11]([OH:13])=[O:12]A mixed solution of the compound (13.5 g, 49.07 mmol) obtained in step 2 and 1N aqueous sodium hydroxide solution (65 mL, 65.00 mmol) in ethanol (70 mL) and THF (70 mL) was stirred at 60° C. for 2.5 hr. The organic solvent was evaporated under reduced pressure, and water and 1N hydrochloric acid (70 mL) were added thereto. The precipitate was collected by filtration, and washed with diethyl ether and hexane to give 5-bromo-1-tert-butyl-1H-pyrazole-4-carboxylic acid (10.29 g, 41.6 mmol, 85%) as a white powder.
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