Sodium Hydroxide → 4-Methoxy-1H-1lambda~6~,2-benzothiazole-1,1,3(2H)-trione

Participants

Reaction Steps

2.5 gm (11.8 mmols) of 3-amino-4-methoxy-1,2-benzoisothiazole-1,1-dioxide were refluxed for 3 hours in a solution of 0.47 gm (11.8 mmols) of sodium hydroxide in 300 ml of water. The reaction mixture was filtered while still hot and acidified with hydrochloric acid. The resulting precipitate was filtered off, dried and recrystallized from benzene/ethyl acetate. 2.0 gm (9.4 mmols) of 4-methoxy-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide (m.p.: 224° C.) were obtained, which were dissolved in 500 ml of ethylene chloride, and the solution was admixed with 10 gm (40 mmols) of boron tribromide. The reaction mixture was slowly heated and refluxed for 1 hour. The reaction mixture was evaporated in vacuo and then repeatedly evaporated in vacuo after addition of ethanol. The obtained product was recrystallized from water, yielding 1.6 gm (68% of theory) of 4-hydroxy-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide.

Provenance & Evidence