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 in a tantalum autoclave at 100° C. for 30 hours. When it has cooled, the product is concentrated under reduced pressure and the residue is partitioned between methylene chloride and 2 N sodium hydroxide solution. The aqueous phase is freed from insoluble matter by filtration, and is washed with methylene chloride, acidified with hydrochloric acid and finally extracted repeatedly with methylene chloride. The combined extracts are dried over magnesium sulfate and concentrated under reduced pressure. 32 g (65% of theory) of 4-hydroxy-1,2-benzisothiazole of melting point 133°-134° C. are obtained.

1. temperatureWhen it has cooled
2. concentrationthe product is concentrated under reduced pressure
3. customthe residue is partitioned between methylene chloride and 2 N sodium hydroxide solution
4. filtrationThe aqueous phase is freed from insoluble matter by filtration
5. washis washed with methylene chloride
6. extractionfinally extracted repeatedly with methylene chloride
7. dry with materialThe combined extracts are dried over magnesium sulfate
8. concentrationconcentrated under reduced pressure