Electrophilic subsitution in 2,1-benzisothiazoles

Abstract

Bromination of 2,1-benzisothiazole (I) under conditions in which Br⁺ is the electrophilic species gives a mixture of 5- and 7-bromo-2,1-benzisothiazole, together with a smaller quantity of 4,7-dibromo-2,1-benzisothiazole. Nitration of 2,1-benzisothiazole affords mainly 5-nitro-2,1-benzisothiazole with smaller quantities of the 7-nitro- and 4-nitro-isomers. Nitration of monosubstituted 2,1-benzisothiazoles gives products which indicate that the substituent group already present in the benzenoid ring is the decisive directing influence.