反应详情

2,4-Difluorobenzoic acid (50 g, 316 mmol) was dissolved in concentrated sulfuric acid (200 ml), and N-iodosuccinimide (68 g, 300 mmol) was added by portions at not more than 5° C. After the completion of the addition, the mixture was stirred at the same temperature for 4.5 hr. The reaction mixture was poured into ice water (ca. 600 ml), then 10% aqueous sodium sulfite solution was added, and the mixture was stirred. The precipitated solid was collected by filtration, washed with water, and vacuum dried to give crude crystals (85 g). The crude crystals obtained in the same manner were combined (total amount 205 g), and recrystallized from 50% aqueous ethanol (820 ml) to give 2,4-difluoro-5-iodobenzoic acid (148 g, yield 73%) as a white solid.

1. additionAfter the completion of the addition
2. stirringthe mixture was stirred
3. filtrationThe precipitated solid was collected by filtration
4. washwashed with water, and vacuum
5. customdried
6. customto give crude crystals (85 g)
7. customThe crude crystals obtained in the same manner
8. customrecrystallized from 50% aqueous ethanol (820 ml)