S(=O)(=O)(O)[OH:2].N(=[CH:8][C:9]([NH:11][C:12]1[CH:19]=[CH:18][C:15]([O:16][CH3:17])=[CH:14][CH:13]=1)=[O:10])O>O>[CH3:17][O:16][C:15]1[CH:14]=[C:13]2[C:12](=[CH:19][CH:18]=1)[NH:11][C:9](=[O:10])[C:8]2=[O:2]Concentrated sulfuric acid (45 ml) containing water (5 ml) was warmed to 60° C. and 8.6 g of N-(2-hydroximinoacetyl)-anisidine was added in one portion. The mixture was stirred at 93° C. for 10 minutes and then allowed to cool to room temperature. The mixture was poured into 500 g of ice and extracted 3 times with ethyl acetate. The combined extracts were dried over anhydrous sodium sulfate and concentrated to give 5.1 g (65% yield) of 5-methoxyisatin as a dark red solid.
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