[2-Chloro-3-nitro-5-(tri-fluoro-meth-yl)phen-yl](piperidin-1-yl)methanone: structural characterization of a side product in benzo-thia-zinone synthesis

Abstract

1,3-Benzo-thia-zin-4-ones (BTZs) are a promising new class of anti-tuberculosis drug candidates, some of which have reached clinical trials. The title compound, the benzamide derivative [2-chloro-3-nitro-5-(tri-fluoro-meth-yl)phen-yl](piper-id-in-1-yl)methanone, C₁₃H₁₂ClF₃N₂O₃, occurs as a side product as a result of competitive reaction pathways in the nucleophilic attack during the synthesis of the BTZ 8-nitro-2-(piperidin-1-yl)-6-(tri-fluoro-meth-yl)-1,3-benzo-thia-zin-4-one, following the original synthetic route, whereby the corresponding benzoyl iso-thio-cyanate is reacted with piperidine as secondary amine. In the title compound, the nitro group and the nearly planar amide group are significantly twisted out of the plane of the benzene ring. The piperidine ring adopts a chair conformation. The tri-fluoro-methyl group exhibits slight rotational disorder with a refined ratio of occupancies of 0.972 (2):0.028 (2). There is structural evidence for inter-molecular weak C-H⋯O hydrogen bonds.

Keywords: anti-tuberculosis drugs; benzo­thia­zinones; crystal structure; nitro­benzamides; reaction mechanism.