[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([N:8]2[C:12]([CH:13]([CH3:15])[CH3:14])=[C:11]([C:16]([O:18]C)=[O:17])[CH:10]=[N:9]2)=[CH:4][CH:3]=1.O.[OH-].[Li+].O.Cl>CO.C1COCC1>[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([N:8]2[C:12]([CH:13]([CH3:15])[CH3:14])=[C:11]([C:16]([OH:18])=[O:17])[CH:10]=[N:9]2)=[CH:6][CH:7]=1A mixture of methyl 1-(4-chlorophenyl)-5-isopropyl-pyrazole-4-carboxylate (26.0 g, 96.7 mmol) and lithium hydroxide monohydrate (10.0 g, 238 mml) in MeOH (60 mL), THF (60 mL), and H2O (30 mL) was heated at 80° C. for 3 h. The reaction mixture was cooled to room temperature, acidified with 1 N aqueous HCl, and extracted with EtOAc (600 ml). The organic layer was separated, dried over anhydrous sodium sulfate, and concentrated in vacuo to yield 1-(4-chlorophenyl)-5-isopropylpyrazole-4-carboxylic acid (24.0 g, 97%).
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