反应详情

A suspension of 3-oxo-2,3-dihydro-4H-1,2,4-benzothiadiazine-7-carboxylic acid 1,1-dioxide monohydrate (10 g) in a mixture of concentrated sulfuric acid (150 mL) and water (150 mL) was refluxed until complete dissolution of the starting material (1-2 h). The resulting solution was placed on an ice bath and supplemented dropwise with a 20% aqueous solution of NaOH under stirring and cooling until pH 1-2. The precipitate was collected by filtration, washed with water and dried (yield: 6.6 g); m.p.: 214-219° C.

1. temperaturewas refluxed until complete dissolution of the starting material (1-2 h)
2. customThe resulting solution was placed on an ice bath
3. temperaturecooling until pH 1-2
4. filtrationThe precipitate was collected by filtration
5. washwashed with water
6. customdried (yield: 6.6 g)