反应详情

50 g of 4-methoxy-1,2-benzisothiazole are suspended in 700 ml of acetic acid containing 10% by weight of hydrogen bromide and 5 g of red phosphorus, and the suspension is heated for 30 hours at 100° C. in a tantalum autoclave. After cooling, the material discharged from the autoclave is concentrated under reduced pressure and the residue is partitioned between methylene chloride and 2 N sodium hydroxide solution. The water phase is filtered to remove insoluble matter, washed with methylene chloride, acidified with hydrochloric acid and then repeatedly extracted with methylene chloride. The combined extracts are dried over magnesium sulfate and then concentrated under reduced pressure. 32 g (65% of theory) of 4-hydroxy-1,2-benzisothiazole of melting point 133°-134° C. are obtained. C7H5ONS (151)

1. temperatureAfter cooling
2. concentrationis concentrated under reduced pressure
3. customthe residue is partitioned between methylene chloride and 2 N sodium hydroxide solution
4. filtrationThe water phase is filtered
5. customto remove insoluble matter
6. washwashed with methylene chloride
7. extractionrepeatedly extracted with methylene chloride
8. dry with materialThe combined extracts are dried over magnesium sulfate
9. concentrationconcentrated under reduced pressure