3-Amino-4-bromophenol

(3) reduction reaction:The reaction flask was added 13. 1g 3-nitro-4-bromophenol, 66g ethanol, stirring to dissolve.Add 1.3g ferric oxide, 11.3 g of a hydrazine hydrate solution at a concentration of 80 wtpercent.Stir and heat to reflux. Reflux 1.5h, Sampling, no raw materials, cooling and filtering. The filtrate was concentrated, 16 ml of water was added to the concentrate, With stirring, adjust pH = 7 with 10percent hydrochloric acid. Precipitation of the solid, the crude product was filtered, wet weight 15g.The crude product was recrystallized, Ethanol 17g at 60 ° C, the product just dissolved.Add 17g of water. Stir 10min. After 30min at room temperature, transfer to ice bath for 30min, Precipitated crystals, filtered to give 8 Og light pink product, purity 99percentYield 70.9percentGeneral procedure: A solution of BBr3 in dichloromethane (1.0 M, 12 mL, 12 mmol) was added slowly to a solution of 4-bromo-3-methoxyaniline (800 mg, 3.96 mmol) in methylene chloride(15 mL) at 0C. The resulting brown solution was warmed toroom temperature and stirred for 24 h. After saturated aqueousNaHCO3 (30 mL) was added at 0C, the solution was extractedwith EtOAc (20 mL × 3). The combined organic layer wasdried with anhydrous Na2SO4, filtered and concentrated invacuum. The residue was purified by flash chromatographyover silica gel (petroleum-EtOAc = 2 : 1) to give 5-amino-2-bromophenol (665 mg, 88%). To a solution of 5-amino-2-bromophenol (55 mg, 0.29 mmol)and triethylamine (53 muL, 0.38 mmol) in tetrahydrofuran (THF)(3 mL) was added slowly benzoyl chloride (0.32 mmol) at 0C.The reaction mixture was then stirred at room temperature for30 min. After the reaction was quenched with water (10 mL), the solution was extracted with EtOAc (10 mL × 2). The combinedorganic layer was dried over anhydrous Na2SO4, filteredand concentrated in vacuum. The residue was purified bycolumn chromatography to afford the product 3 (74 mg, 87%).General procedure: A solution of BBr3 in dichloromethane (1.0 M, 12 mL, 12 mmol) was added slowly to a solution of 4-bromo-3-methoxyaniline (800 mg, 3.96 mmol) in methylene chloride(15 mL) at 0C. The resulting brown solution was warmed toroom temperature and stirred for 24 h. After saturated aqueousNaHCO3 (30 mL) was added at 0C, the solution was extractedwith EtOAc (20 mL × 3). The combined organic layer wasdried with anhydrous Na2SO4, filtered and concentrated invacuum. The residue was purified by flash chromatographyover silica gel (petroleum-EtOAc = 2 : 1) to give 5-amino-2-bromophenol (665 mg, 88%).To a solution of 5-amino-2-bromophenol (55 mg, 0.29 mmol)and triethylamine (53 muL, 0.38 mmol) in tetrahydrofuran (THF)(3 mL) was added slowly benzoyl chloride (0.32 mmol) at 0C.The reaction mixture was then stirred at room temperature for30 min. After the reaction was quenched with water (10 mL), the solution was extracted with EtOAc (10 mL × 2). The combinedorganic layer was dried over anhydrous Na2SO4, filteredand concentrated in vacuum. The residue was purified bycolumn chromatography to afford the product 3 (74 mg, 87%).(3) reduction reaction:The reaction flask was added 13. 1g 3-nitro-4-bromophenol, 66g ethanol, stirring to dissolve.Add 1.3g ferric oxide, 11.3 g of a hydrazine hydrate solution at a concentration of 80 wtpercent.Stir and heat to reflux. Reflux 1.5h, Sampling, no raw materials, cooling and filtering. The filtrate was concentrated, 16 ml of water was added to the concentrate, With stirring, adjust pH = 7 with 10percent hydrochloric acid. Precipitation of the solid, the crude product was filtered, wet weight 15g.The crude product was recrystallized, Ethanol 17g at 60 ° C, the product just dissolved.Add 17g of water. Stir 10min. After 30min at room temperature, transfer to ice bath for 30min, Precipitated crystals, filtered to give 8 Og light pink product, purity 99percentYield 70.9percent