(<i>E</i>,<i>E</i>)-4-{4-[3-(4-Chloroanilino)-1-hydroxybut-2-enylidene]-3-methyl-5-oxo-4,5-dihydro-1<i>H</i>-pyrazol-1-yl}benzenesulfonamide

The mol-ecule of the title compound, C(20)H(19)ClN(4)O(4)S, features a central pyrazole ring that possesses a benzene substituent, as well as a conjugated =C-C=C-C(meth-yl) substituent. The benzene ring is slightly twisted [dihedral angle = 7.7 (2)°] with respect to the five-membered ring; the mean plane of the zigzag =C-C=C-C fragment [torsion angle = 178.0 (4)°] is also slightly twisted [dihedral angle = 10.6 (4)°]. The amine and hy-droxy groups form intra-molecular hydrogen bonds. The amide group uses one of its H atoms to form a hydrogen bond to the sulfamyl O atom of an inversion-related mol-ecule. Adjacent dimers are further linked by an N-H(amido)⋯N(pyrazole) hydrogen bond to generate a linear chain. The crystal studied is a nonmerohedral twin with a minor twin component of 25.6 (2)%.