2-[(Z)-1,1-Dioxo-2-(2,4,5-tri­fluoro­benz­yl)-3,4-di­hydro-2H-1,2-benzo­thia­zin-4-yl­idene]acetic acid

In the title compound, C17H12F3NO4S, the heterocyclic thia-zine ring adopts a half-chair conformation and the dihedral angle between the benzene rings is 43.28 (9)°. The α,β-unsaturated C=C group is inclined at an angle of 21.0 (3)° to the benzene ring of the benzo-thia-zine moiety. In the crystal, inversion dimers linked by pairs of carb-oxy-lic acid O-H⋯O hydrogen bonds generate R 2 (2)(8) loops. Each of the F atoms accepts a Ca-H⋯F (a = aromatic) hydrogen bond from an adjacent mol-ecule, resulting in (001) sheets.