SYNTHESIS OF (E)-N-SUBSTITUTED 1,2-BENZOTHIAZOL-3(2H)-IMINE 1,1-DIOXIDE DERIVATIVES FROM SECONDARY BENZENESULFONAMIDES AND ISOTHIOCYANATES

摘要

A new and simple method for the preparation of (E)-N-substituted 1,2-benzothiazol-3(2H)-imine 1,1-dioxide derivatives has been developed. 2,N-Dilithiobenzenesulfonamides, generated by the treatment of secondary benzenesulfonamides with two equivalents of butyllithium, react with isothiocyanates to afford the corresponding 2-(aminosulfonyl)benzothioamides, which undergo ring closure with a formal elimination of hydrogen sulfide on treatment with thionyl chloride in the presence of two equivalents of pyridine to provide the desired products. Acid hydrolysis of some of these products leads to the formation of N-substituted saccharins.