5-Bromo-2-iodobenzoic acid

5794-88-7

21740-00-1

General procedure for the synthesis of 5-bromo-2-iodobenzoic acid from 2-amino-5-bromobenzoic acid: a solution of 2-amino-5-bromobenzoic acid (3.9 g, 0.018 mol), sodium nitrite (NaNO2, 1.5 g, 0.022 mol) and sodium hydroxide (NaOH, 0.90 g, 0.023 mmol) in water (55 mL) was added dropwise to a stirred of a concentrated hydrochloric acid solution. The hydrochloric acid (HCl, 6.4 mL) in water (9 mL) solution was cooled at 0°C for 1.5 hours. After dropwise addition, stirring was continued for 30 minutes at 0°C. The formed diazonium salt suspension was added to a stirred solution of potassium iodide (KI, 4.5 g, 0.027 mol) and concentrated hydrochloric acid. A solution of sulfuric acid (H2SO4, 1.1 mL) in water (7.4 mL) was slowly added over 20 minutes at 35 to 40°C. The mixture was then heated to 90 °C and stirred for 30 min. Unreacted iodine was removed by steam distillation. The mixture was stirred and cooled. The crude product was filtered and washed with cold water, then dissolved in 40% aqueous sodium hydroxide. The polymer fraction was separated by decantation and the clarified solution was acidified with concentrated hydrochloric acid. The product was extracted with ether (Et2O). The extract was dried with anhydrous magnesium sulfate (MgSO4) and concentrated in vacuum. The residue was crystallized from a solvent mixture of methanol (MeOH) and water (H2O) (1:1, v/v) to give 5-bromo-2-iodobenzoic acid (3.56 g, 0.0109 mol, 60% yield) as a light yellow solid.