Example 13 Synthesis of 4-bromo-7-methoxyindole (LII): to a tetrahydrofuran (THF) solution (300 ml) of 4-bromo-2-nitroanisole (7.89 g, 33.3 mmol) was slowly added vinylmagnesium bromide (1 M in THF) at -60 °C. The reaction temperature was kept below -40 °C while the reaction mixture was stirred so that the temperature was gradually raised to -40 °C within 2 hours. After completion of the reaction, the reaction was quenched with saturated ammonium chloride (NH4Cl) solution (100 ml, 0.1 mol). The aqueous phase was extracted with ether (Et2O, 200 ml), the organic layers were combined, washed with brine, dried over anhydrous magnesium sulfate (MgSO4), filtered and concentrated. Finally, the target product 4-bromo-7-methoxyindole (LII, 594 mg, 8% yield) was purified by fast chromatography.
