N[C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][C:10]=1[Cl:11])[C:7](=[O:12])[NH:6][C:5]2=[O:13].S(=O)(=O)(O)O.N([O-])=O.[Na+].[I-:23].[K+]>O.O1CCCC1.C(OCC)(=O)C>[Cl:11][C:10]1[CH:9]=[C:8]2[C:4](=[CH:3][C:2]=1[I:23])[C:5](=[O:13])[NH:6][C:7]2=[O:12]
To a stirred suspension of 96.1 mmol 5-amino-6-chloroisoindoline-1,3-dione (commercial, CAS: 5566-48-3) in 170 ml water was added dropwise at 10° C. a solution of 11 ml concentrated sulfuric acid in 50 ml water. After cooling the mixture to 5° C., a solution of 120 mmol sodium nitrite in 40 ml water was added dropwise and stirring continued at 0° C. for 90 min. A solution of 327 mmol potassium iodide in 80 ml water was then added dropwise over 40 min while maintaining the reaction temperature between 0 and 5° C. The reaction mixture was then warmed to room temperature and subsequently heated at 35° C. for 45 min and then 60° C. for 30 min before being recooled to room temperature and diluted with tetrahydrofuran/ethyl acetate (1/2). The phases were separated and the organic phase washed sequentially with aqueous sodium thiosulphite and brine and then dried over sodium sulfate and concentrated in vacuo. The residue was resuspended in 300 ml dichloromethane, stirred for 10 min at room temperature, and the resulting crystals collected by filtration to yield the title compound as a light brown solid. MS (m/e): 308.9 ({37Cl}M+, 35%), 306.9 ({35Cl}M+, 100%).
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