Synthesis of novel 8-nitro-substituted 1,3-benzothiazin-4-ones

New 2,5-bis(azacyclohex-1-yl)-8-nitro-1,3-benzothiazin-4-ones were synthesized from 2,6-difluorobenzoic acid in two preparative stages. The ethoxycarbonylpiperazino derivative surpasses in tuberculostatic activity (MIC 4μgml⁻¹) its 5-fluoro-8-H-counterpart. The first representative of 5-fluoro-8-nitro-1,3-benzothiazin-4-ones was obtained through the condensation of 2,6-difluoro-3-nitrobenzoyl isothiocyanate and N-methylindole.