General procedure for the synthesis of 6-iodo-1H-indole from 6-bromo-1H-indole: To a dioxane solution (30 mL) of 6-bromo-1H-indole (3.00 g, 15.3 mmol) under nitrogen protection were sequentially added NaI (4.59 g, 30.6 mmol), CuI (290 mg, 1.53 mmol) and N,N'-dimethyl ethylenediamine (0.35 mL). The reaction mixture was purged with nitrogen for 5 min to remove oxygen. Subsequently, the reaction mixture was stirred overnight in an oil bath at 110 °C under nitrogen atmosphere. After completion of the reaction, it was cooled to room temperature and concentrated under reduced pressure to remove the organic solvent. EtOAc and water were added to the residue to separate the organic and aqueous phases. The organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, concentrated and purified by column chromatography (eluent: pure petroleum ether) to afford the target compound 6-iodo-1H-indole (2.1 g, 57% yield). Mass spectrum (ESI) m/z: 244.0 [M + H]+.
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