Synthesis, reactions, and biological activity of 1,4-benzothiazine derivatives

6,7-Dimethoxy-2H-1,4-benzothiazin-3(4H)-one reacts with dimethylformamide dimethylacetal (DMF-DMA) to give the novel enaminone 2-(dimethylaminomethylene)-6,7-dimethoxy-2H-1,4-benzothiazin-3(4H)-one. The reaction of the latter with various active methylene compounds afforded pyrido[3,2-b][1,4]benzothiazines. Also, coupling of the enaminone with diazotized aniline derivatives gave 2-(arylhydrazono)-6,7-dimethoxy-2H-1,4-benzothiazin-3(4H)-ones. Spectral data indicated that the latter compounds exist predominantly in the hydrazone tautomeric form. In addition, coupling of the enaminone with diazotized heterocyclic amines afforded tetra-and pentaheterocyclic ring systems. The antitumor and antimicrobial activity of some of the synthesized compounds was screened.