2-Chloro-3-nitro-5-(tri-fluoro-meth-yl)benzoic acid and -benzamide: structural characterization of two precursors for anti-tubercular benzo-thia-zinones.

8-Nitro-1,3-benzo-thia-zin-4-ones are a promising class of new anti-tubercular agents, two candidates of which, namely BTZ043 and PBTZ169 (INN: macozinone), have reached clinical trials. The crystal and mol-ecular structures of two synthetic precursors, 2-chloro-3-nitro-5-(tri-fluoro-meth-yl)benzoic acid, CHClFNO (), and 2-chloro-3-nitro-5-(tri-fluoro-meth-yl)benzamide, CHClFNO (), are reported. In and , the respective carb-oxy, carboxamide and the nitro groups are significantly twisted out of the plane of the benzene ring. In , the nitro group is oriented almost perpendicular to the benzene ring plane. In the crystal, and form O-H⋯O and N-H⋯O hydrogen-bonded dimers, respectively, which in extend into primary amide tapes along the [101] direction. The tri-fluoro-methyl group in exhibits rotational disorder with an occupancy ratio of 0.876 (3):0.124 (3).