C(OC(=O)C)(=O)C.[Br-].C([NH3+:13])CCC.C([O-])(=O)C.[K+].[C:19]([NH:22][C:23]1[C:32]([CH3:33])=[CH:31][C:26]([C:27]([O:29][CH3:30])=[O:28])=[C:25]([CH3:34])[CH:24]=1)(=[O:21])[CH3:20].N(OCCC(C)C)=O>C(OCC)(=O)C.CCCCCC.O>[C:19]([N:22]1[C:23]2[C:32](=[CH:31][C:26]([C:27]([O:29][CH3:30])=[O:28])=[C:25]([CH3:34])[CH:24]=2)[CH:33]=[N:13]1)(=[O:21])[CH3:20]Acetic anhydride (0.85 ml, 9.01 mmol), n-butylammonium bromide (0.0502 g, 0.156 mmol) and potassium acetate (0.587 g, 5.98 mmol) were added to a solution of methyl 4-(acetylamino)-2,5-dimethylbenzoate (0.661 g, 2.99 mmol) in ethyl acetate (5 ml), followed by adding thereto a solution of isoamyl nitrite (0.0458 g, 3.91 mmol) in ethyl acetate (2 ml), and the resulting mixture was stirred for 8 hours with heating under reflux. Water was added thereto, followed by extraction with ethyl acetate (three times), and the extract solution was dried over anhydrous magnesium sulfate. The solvent was distilled off under reduced pressure and the resulting residue was purified by a silica gel column chromatography (hexane/ethyl acetate=5/1 to 1/1). The solid thus obtained was suspended in hexane and stirred to be washed, and then it was collected by filtration and dried under reduced pressure to obtain methyl 1-acetyl-6-methyl-1H-indazole-5-carboxylate (0.0731 g, 11%).
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