C([O:3][C:4]([C:6]1[CH:7]=[N:8][N:9]([CH:12]2[CH2:16][CH2:15][CH2:14][CH2:13]2)[C:10]=1[Cl:11])=[O:5])C.O.[OH-].[Li+]>CO>[Cl:11][C:10]1[N:9]([CH:12]2[CH2:16][CH2:15][CH2:14][CH2:13]2)[N:8]=[CH:7][C:6]=1[C:4]([OH:5])=[O:3]5-Chloro-1-cyclopentyl-1H-pyrazole-4-carboxylic acid ethyl ester (0.710 g, 2.93 mmol) was dissolved in methanol (4.3 mL). Water (4.3 mL) and lithium hydroxide (0.097 g, 4.05 mmol) were added and the mixture was heated at 80° C. for 2 hours. After cooling to room temperature, methanol was removed in vacuo. Tetrahydrofuran was added to the residue and then removed in vacuo to ensure complete removal of the methanol. The residue was diluted with water and treated with 6N HCl to pH 2-3, resulting in precipitation of a milky solid. The solid was collected, washed with water and dried under house vacuum at 45° C., yielding 5-chloro-1-cyclopentyl-1H-pyrazole-4-carboxylic acid (0.580 g, 91%). This material was used as is without any further purification.
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