3-Chloro-1-methyl-4-[2-(3-phenylallylidene)hydrazinylidene]-3, 4-dihydro-1H-2λ⁶,1-benzothiazine-2,2-dione

In the title compound, C₁₈H₁₆ClN3O₂S, the dihedral angle between the aromatic rings is 4.81 (2)° and the alkyl chain takes on an extended conformation [N - C - C - C = 179.2 (4)°]. The conformation of the thiazine ring is an envelope, with the S atom displaced by -0.805 (3) Å from the mean plane of the other five atoms (r.m.s. deviation = 0.046 Å). The Cl atom is an axial conformation and is displaced by 1.761 (4) Å from the thiazine ring plane. In the crystal, inversion dimers linked by pairs of C - H⋯O interactions generate R 2 ²(20) loops and further C - H⋯O hydrogen bonds link the dimers into (001) sheets. Weak aromatic π-π stacking interactions [centroid-centroid separations = 3.870 (3) and 3.883 (3) Å] are also observed.