4-methoxy-1,1-dioxo-1,2-benzothiazol-3-one

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 2.5 gm (11.8 mmols) of 3-amino-4-methoxy-1,2-benzoisothiazole-1,1-dioxide were reacted with sodium hydroxide analogous to Example 5, and by subsequent acidification the reaction product was converted into 4-methoxy-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide. The obtained compound, together with 650 mg (10 mmols) of potassium cyanide in dimethyl-sulfoxide, was heated at 180° C. for 3 hours. After addition of petroleum ether the potassium salt of the product was precipitated, and the precipitate was dissolved in water. After acidifying with aqueous hydrochloric acid, filtering and recrystallizing, 1.46 gm (62% of theory) of 4-hydroxy-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide were obtained. was precipitated the precipitate was dissolved in water filtering recrystallizing

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 2.5 gm (11.8 mmols) of 3-amino-4-methoxy-1,2-benzoisothiazole-1,1-dioxide were reacted with sodium hydroxide analogous to Example 4. The reaction mixture was acidified, whereby 4-methoxy-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide was obtained, which was subsequently heated at 200°-205° C. with 20 gm of pyridine hydrochloride. After cooling, the reaction mixture was extracted several times with boiling benzene, the residue was dissolved in water, and the aqueous solution was again extracted with boiling benzene. The combined benzene phases were dried and evaporated in vacuo. The residue was recrystallized from water, yielding 1.35 gm (57.5% of theory) of 4-hydroxy-1,2-benzoisothiazol-3(2H)-one-1,1-dioxide.

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 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. The reaction mixture was filtered while still hot and The resulting precipitate was filtered off dried recrystallized from benzene/ethyl acetate