[CH2:1]([N:3]1[CH:7]=[C:6]([CH3:8])[C:5]([C:9]([O:11]CC)=[O:10])=[N:4]1)[CH3:2].[OH-].[Na+].C(O)C.Cl>O>[CH2:1]([N:3]1[CH:7]=[C:6]([CH3:8])[C:5]([C:9]([OH:11])=[O:10])=[N:4]1)[CH3:2]A mixture of ethyl 1-ethyl-4-methyl-1H-pyrazole-3-carboxylate (8.60 g, 47.2 mmol), 8N aqueous sodium hydroxide solution (11.8 mL) and ethanol (30 mL) was stirred at room temperature for 15 hr. The reaction mixture was neutralized with 1N hydrochloric acid, diluted with water, and extracted with ethyl acetate. The organic layer was washed with water and saturated brine, dried over anhydrous magnesium sulfate and filtrated. The filtrate was concentrated under reduced pressure, and the residue was collected by filtration and washed with ethyl acetate-hexane to give the title compound (5.19 g, 71%) as a white solid.
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