[CH3:1][O:2][C:3]1[CH:11]=[CH:10][C:9]([O:12][CH3:13])=[C:8]2[C:4]=1[C:5](=[O:15])[C:6](=[O:14])[NH:7]2.C(=O)([O-])[O-].[Cs+].[Cs+].Br[CH2:23][CH2:24][O:25][CH2:26][CH2:27][O:28][CH3:29]>CN(C)C=O.O1CCCC1>[CH3:1][O:2][C:3]1[CH:11]=[CH:10][C:9]([O:12][CH3:13])=[C:8]2[C:4]=1[C:5](=[O:15])[C:6](=[O:14])[N:7]2[CH2:23][CH2:24][O:25][CH2:26][CH2:27][O:28][CH3:29]To a solution of 4,7-dimethoxy-1H-indole-2,3-dione (1.8 g, 8.7 mmol) in anhydroud N,N-dimethylformamide (20 mL) and anhydrous tetrahydrofuran (120 mL) at ambient temperature was added cesium carbonate (11.4 g, 35.0 mmol), The mixture was stirred at ambient temperature for 30 min and 1-bromo-2-(2-methoxyethoxy)ethane (2.35 mL, 17.4 mmol) was added in one portion. The mixture was stirred at ambient temperature for 16 h, concentrated in vacuo to a small volume and poured into ice water (300 mL). The mixture was extracted with ethyl acetate and the combined organic extracts were filtered through a pad of diatomaceous earth. The filtrate was dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. Trituration of the residue in hexanes afforded 4,7-dimethoxy-1-[2-(2-methoxyethoxy)ethyl]-1H-indole-2,3-dione (2.2 g, 82%).
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