Research on potentially bioactive aza and thiaza polycyclic compounds containing a bridgehead nitrogen atom. III. Synthesis and antimicrobial activity of some 1,4-benzothiazines and pyrrolobenzothiazines

Cyclization reactions of N-(2,2-dialkoxyethyl)-1,4-benzothiazine lactams 2 and 1,4-benzothiazine-sulfones 10 lead to the corresponding pyrrolo[1,2,3-de]-1,4-benzothiazines 4 and 12, respectively, by using the dioxane/p-tolucnesulfonic acid or polyphosphoric acid/chloroform systems. In contrast, in the same reaction conditions, 1,1-benzothiazines 5a-h do not provide the expected pyrrolobenzothiazines 7, and as for 5c-h considerable amount of the 2-amino-phenyl-sulfide 8 was obtained. The results of microbiological assays are reported.