Sulfuric Acid → 4-hydroxy-1H-1,2-benzisothiazole-1,1,3(2H)-trione

Participants

Reaction Steps

A solution of 1,2-benzoisothiazol-3(2H)-one-1,1-dioxide-4-diazonium chloride, which was prepared by diazotization of 1.98 gm (10 mmols) of 4-amino-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide with sodium nitrite in dilute hydrochloric acid, was reacted with 150 ml of aqueous 10% sulfuric acid, and the reaction mixture was heated on a water bath until the evolution of nitrogen had ceased. After cooling, the reaction mixture was strongly acidified with concentrated aqueous hydrochloric acid and extracted with ether. The organic phase was evaporated, the residue was dissolved in a little sodium hydrochloride, filtered and again acidified with hydrochloric acid. The crystals formed were recrystallized from water, yielding 0.98 gm (40% of theory) of 4-hydroxy-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide.

Provenance & Evidence