Synthesis of some N-substituted 6,7-dimethoxy-1,2-benzothiazin(4H)-3-one 1,1-dioxides

Substituted 1,2-benzothiazin-3-ones have been prepared by cyclization of 4,5-dimethoxy-2-carboethoxymethybenzenesulfonamides. The latter were obtained by the action of ammonia and primary and secondary amines on 4,5-dimethoxy-2-carboethoxymethylbenzenesulfonyl chloride which in turn was obtained from ethyl 3,4-dimethoxyphenylacetate and chlorosulfonic acid.