Synthesis
Under nitrogen protection, 2-bromo-1,3-dimethyl-4-nitrobenzene (3.0 g, 13.04 mmol), pyrrolidine (926 mg, 13.04 mmol), and N,N-dimethylformamide dimethyl acetal (7.76 g, 65.22 mmol) were dissolved in 1,4-dioxane (20 mL) and the reaction was carried out for 18 hr at 100 °C. After completion of the reaction, the mixture was concentrated to dryness under reduced pressure. To the residue was added iron powder (3.65 g, 65.22 mmol) and acetic acid (40 mL) and heated at 110°C for 4 hours. The reaction solution was cooled to room temperature and filtered, and the filtrate was concentrated under reduced pressure. The crude product was purified by silica gel column chromatography using petroleum ether/ethyl acetate (10:1) as eluent to afford 4-bromo-5-methyl-1H-indole (150 mg, 5.5% yield) as a yellow solid. Mass spectrum (ESI) m/z = 210.1 ([M+H]+).
