[I:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][CH:6]=[C:5]2[C:11]([O:13][CH3:14])=[O:12].[Br:15]Br.S(=O)(=O)(O)O>C(O)(=O)C.CO.CO.ClCCl>[Br:15][C:10]1[CH:9]=[C:8]2[C:4]([C:5]([C:11]([O:13][CH3:14])=[O:12])=[CH:6][NH:7]2)=[CH:3][C:2]=1[I:1]
To a suspension of methyl 5-iodo-1H-indole-3-carboxylate (1.20 g, 3.09 mmol) in acetic acid (30 ml) was added a solution of bromine (0.15 ml, 2.9 mmol) in acetic acid (5 ml). Reaction was heated to reflux and stirred for 3 hours. The reaction was then cooled and poured onto ice water, then partitioned between water and dichloromethane. The aqueous layer was extracted with 10% MeOH/DCM (2×100 mL). The organics were combined, washed with brine, and dried over sodium sulfate, filtered and concentrated to give a dark red semi solid. The residue was taken up in methanol (30 ml). Concentrated sulfuric acid (0.5 ml) was added and mixture was heated to 70° C. for 2 days. The reaction was cooled then concentrated in vacuo and the residue partitioned between ethyl acetate and aqueous sodium bicarbonate solution. The layers were separated and organic washed with brine, dried over sodium sulfate, filtered and concentrated to give a reddish solid. The residue was dissolved in methanol/dichloromethane and adsorbed onto silica gel and purified by silica gel chromatography (50 g, 20-100% ethyl acetate/heptane). The major peak was isolated to afford a mixture of the title compound and methyl 5-iodo-1H-indole-3-carboxylate confirmed as a brown solid (260 mg) that was taken forward without further purification.
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