Bromine → 2,3,5-Tribromo-4-methoxy-aniline

Beteiligte Stoffe

Reaktionsschritte

3,5-Dibromo-4-methoxy-aniline (13.04 g, 46.42 mmol) was dissolved in DCM (500 mL) and a solution of bromine (2.38 mL, 46.42 mmol) in DCM (80 mL) was added dropwise. A thick, beige precipitate formed. After 45 minutes, the mixture was quenched with NaHCO3 solution (saturated, aq) to pH 9, the layers separated and the aqueous layer extracted into DCM (3×50 mL). The combined organic phase was washed with brine, dried over Na2SO4 and concentrated to dryness under reduced pressure to give a brown solid. The mixture was purified by chromatography, Biotage SP4, 2×120 g Si cartridges in series, 10-50% EtOAc in cyclohexane. The relevant fractions were combined to give 2,3,5-tribromo-4-methoxy-aniline which was contaminated with some 2,3,5,6-tetrabromo-4-methoxy-aniline (12.64 g). The column was eluted further to give recovered starting material 3,5-dibromo-4-methoxy-aniline (2.84 g). The recovered starting material, 3,5-dibromo-4-methoxy-aniline (2.84 g, 10.11 mmol) was dissolved in DCM (100 mL) and a solution of bromine (0.52 mL, 10.11 mmol) in DCM (5 mL) was added dropwise. The mixture was stirred at rt for 2.5 h. The mixture was quenched with NaHCO3 solution (saturated, aq) to pH 9, the layers separated and the aqueous layer extracted into DCM (3×50 mL). The combined organic phase was dried over Na2SO4 and concentrated to dryness under reduced pressure. This material was combined with the impure 2,3,5-tribromo-4-methoxy-aniline and purified by chromatography, Biotage SP4, 330 g Si cartridge, 10% EtOAc in cyclohexane. The relevant fractions were combined to give the desired compound as an orange oil, 9.95 g (60%). m/z: 357.93/359.89/361.90/363.84 [M+H]+.

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