C([O:3][C:4]([C:6]1[CH:7]=[N:8][N:9]([CH2:12][CH2:13][CH2:14][O:15][CH3:16])[C:10]=1[Cl:11])=[O:5])C.[OH-].[Li+]>CO.O>[Cl:11][C:10]1[N:9]([CH2:12][CH2:13][CH2:14][O:15][CH3:16])[N:8]=[CH:7][C:6]=1[C:4]([OH:5])=[O:3]To a solution of 5-chloro-1-(3-methoxypropyl)-1H-pyrazole-4-carboxylic acid ethyl ester (1.71 g, 7.0 mmol) in methanol (7 mL) and water (7 mL) was added lithium hydroxide (235 mg, 9.8 mmol). The reaction mixture was stirred at reflux for 3 h, and then the solution was concentrated under reduced pressure to remove the methanol. The residue was then acidified carefully with 6.0 N aqueous HCl. The resulting mixture was extracted with methylene chloride (2×50 mL). The combined organic extracts were dried over anhydrous Na2SO4, filtered and concentrated in vacuo to provide 5-chloro-1-(3-methoxypropyl)-1H-pyrazole-4-carboxylic acid as an orange solid (1.35 g, 88%). Mass spectrum: m/z: 219.3 (M+1).
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