An efficient synthesis and biological study of substituted 8-chloro-5-methoxy/8-chloro-4H-1,4-benzothiazines, their sulphones and ribofuranosides

8-Chloro-5-methoxy/8-chloro-4H-1,4-benzothiazines were synthesized by condensation followed by oxidative cyclisation of 2-amino-6-chloro-3-methoxy/2-amino-3-chlorobenzenethiol with β–diketones/β–ketoesters in the presence of dimethyl sulphoxide. By treating 4H-1,4-benzothiazines with 30% hydrogen peroxide in glacial acetic acid, 4H-1,4-benzothiazine-1,1-dioxides (sulphones) were synthesized. The 4H-1,4-benzothiazines have also been used as a base to prepare ribofuranosides by the reaction with β–D-ribofuranose-1-acetate-2,3,5-tribenzoate. All the synthesized compounds have been characterized by spectral and elemental analysis and have been examined for antimicrobial and anthelmintic activity.