[H-].[Na+].[CH3:3][N:4]([CH:6]=O)[CH3:5].[NH:8]1[C:16]2[CH:15]=[CH:14][CH:13]=[C:12]([C:17]([O:19][CH3:20])=[O:18])[C:11]=2[CH:10]=[N:9]1.CI>O>[CH3:5][N:4]1[C:6]2[CH:15]=[CH:14][CH:13]=[C:12]([C:17]([O:19][CH3:20])=[O:18])[C:11]=2[CH:16]=[N:8]1.[CH3:3][N:9]1[CH:10]=[C:11]2[C:16]([CH:15]=[CH:14][CH:13]=[C:12]2[C:17]([O:19][CH3:20])=[O:18])=[N:8]1
To a mixture of sodium hydride (522 mg) and DMF (30 ml) was added methyl 1H-indazole-4-carboxylate (2.0 g) under ice-cooling, followed by stirring for 20 minutes. To the reaction mixture was added methyl iodide (1.41 ml), followed by stirring under ice-cooling for 30 minutes, and further at room temperature for 1 hour. The reaction mixture was ice-cooled, and water (100 ml) was added thereto, followed by stirring for 15 minutes. The insolubles were removed by filtration and the filtrate was extracted with ethyl acetate (80 ml). The organic layer was washed with a saturated sodium bicarbonate solution and saturated brine in this order and dried over anhydrous magnesium sulfate. The solvent was then removed by evaporation under reduced pressure. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=3:1→1:1) to obtain methyl 1-methyl-1H-indazole-4-carboxylate (900 mg) as a pale yellow solid and methyl 2-methyl-2H-indazole-4-carboxylate (600 mg) as a pale red oil.
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