[OH-].[Na+].C([N:6]1[C:14]2[C:9](=[CH:10][C:11]([C:16]([O:18]C)=[O:17])=[C:12]([CH3:15])[CH:13]=2)[CH:8]=[N:7]1)(=O)C.[OH-].[Li+]>O1CCCC1.O>[CH3:15][C:12]1[CH:13]=[C:14]2[C:9]([CH:8]=[N:7][NH:6]2)=[CH:10][C:11]=1[C:16]([OH:18])=[O:17]A 2N-aqueous sodium hydroxide solution (0.63 ml, 1.3 mmol) was added to a solution of methyl 1-acetyl-6-methyl-1H-indazole-5-carboxylate (0.0731 g, 0.315 mmol) in tetrahydrofuran (1 ml), and the resulting mixture was stirred for 3 hours with heating under reflux. Then, a 2N-aqueous lithium hydroxide solution (0.63 ml, 1.3 mmol) was added thereto and stirred for another 3 hours. The resulting solution was diluted with water and washed with diethyl ether, and the aqueous layer was adjusted to pH 1 to 2 with 1N-hydrochloric acid to precipitate a solid. The solid precipitated was collected by filtration and the precipitate on a filter was washed with water and dried under reduced pressure to obtain 6-methyl-1H-indazole-5-carboxylic acid (0.0514 g, 93%).
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