[Cl:1][C:2]1[C:10]([N+:11]([O-:13])=[O:12])=[C:9]2[C:5]([C:6](=[O:15])[C:7](=O)[NH:8]2)=[CH:4][CH:3]=1.[Cl:16][CH2:17][CH2:18]CI.C(=O)([O-])[O-:22].[Cs+].[Cs+].[OH-].[Na+].OO.Cl>CN(C)C(=O)C>[Cl:1][C:2]1[CH:3]=[CH:4][C:5]([C:6]([OH:15])=[O:22])=[C:9]([NH:8][CH2:7][CH2:18][CH2:17][Cl:16])[C:10]=1[N+:11]([O-:13])=[O:12]A mixture of 6-chloro-7-nitro-1H-indole-2,3-dione (1.50 g, 6.80 mmol), 1-chloro-3-iodopropane (2.92 mL, 27.2 mmol) and cesium carbonate (8.86 g, 27.2 mmol) in N,N-dimethylacetamide (30 mL) was stirred at room temperature for 6 h. 1N Aqueous sodium hydroxide (30 mL) was added dropwise to the reaction mixture at 0° C., and the resultant mixture was stirred at room temperature for 15 min. 30% Aqueous hydrogen peroxide (1.16 mL) was added dropwise to the reaction mixture at 0° C., and the resultant mixture was stirred at room temperature for 15 min and acidified with 1N aqueous hydrochloric acid at 0° C. The resultant mixture was extracted with ethyl acetate. The extract was washed with water and brine, dried over sodium sulfate, filtered and concentrated in vacuo. The residue was purified by column chromatography on silica gel eluting with a 3% methanol/ethyl acetate mixture to give a crude solid, which was washed with diisopropyl ether/hexane to afford the title compound as an orange solid (1.39 g, 4.74 mmol, 70%).
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