Benz isothiazol-3-one

Another application of the well-known cyclization of ortV o-substituted benzenesulfonamides consists in the treatment of 415 (R =NR2, R = Me) with Et30Bp4 followed by aqueous H2SO4 affording good yields of benz-isothiazol-3-one 1,1-dioxides 416. Their alkaline hydrolysis afforded 415 (R = OH, R = R = H), which is stable at neutral pH but recyclizes to 416 under even mild acidic conditions (pH <4) <1999T237>. 

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