反应详情

温度

-7.5 °C

An aqueous solution of sodium nitrite (3.64 g dissolved in 4 mL of water, 52 mmol) was added drop wise to the concentrated hydrochloric acid (15 mL) cooled to −10 to −5° C. 3-Amino-4-bromo-2,6-dichlorobenzoic acid (5 g, 17 mmol, Step c) was added to the above solution portion-wise while maintaining the temperature around −5° C. The reaction mixture was stirred at this temperature for about 2 hours. Then hypophosphorous acid (9 mL, 170 moles) was added very slowly over a period of 1 hour at the same temperature. The reaction mixture was stirred at the same temperature for about 3 hours and then kept in refrigerator overnight. A precipitate was observed at this stage. The reaction mixture was allowed to warm to room temperature and kept for another 2 hours at room temperature. The reaction mixture was filtered, the residue was washed with cold water and dried to obtain 4-bromo-2,6-dichloro benzoic acid as a yellowish solid (2 g, 42%).

1. temperaturewhile maintaining the temperature around −5° C
2. stirringThe reaction mixture was stirred at the same temperature for about 3 hours
3. customkept in refrigerator overnight
4. temperatureto warm to room temperature
5. waitkept for another 2 hours at room temperature
6. filtrationThe reaction mixture was filtered
7. washthe residue was washed with cold water
8. customdried