[NH:1]1[C:9]2[C:4](=[CH:5][C:6]([C:10]([OH:12])=[O:11])=[CH:7][CH:8]=2)C=N1.[C:13]([O-])([O-])=O.[Cs+].[Cs+].I[CH2:20][CH3:21].O.C[N:24]([CH:26]=O)[CH3:25]>>[CH2:26]([N:24]1[CH:25]=[C:4]2[C:9]([CH:8]=[CH:7][C:6]([C:10]([O:12][CH2:20][CH3:21])=[O:11])=[CH:5]2)=[N:1]1)[CH3:13].[CH2:26]([N:24]1[C:25]2[C:8](=[CH:7][C:6]([C:10]([O:12][CH2:20][CH3:21])=[O:11])=[CH:5][CH:4]=2)[CH:9]=[N:1]1)[CH3:13]To a suspension of 1H-indazole-5-carboxylic acid (500 mg, 3.08 mmol) and Cs2CO3 (2.01 g, 6.17 mmol) in DMF (10 mL) was added iodoethane (1.92 g, 12.33 mmol) at room temperature. The mixture was stirred at room temperature for 1 day. The mixture was poured into H2O, extracted with EtOAc, dried over Na2SO4, filtered and concentrated. The residual oil was purified by silica gel column chromatography (0-60% EtOAc in hexane) to give ethyl 2-ethyl-2H-indazole-5-carboxylate (208 mg, 31%) as a white solid and ethyl 1-ethyl-1H-indazole-5-carboxylate (435 mg, 65%) as a white solid.
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