(2E)-2-(2,4-Dichloro-phenyl-sulfon-yl)-3-(3-methoxy-anilino)-3-(methyl-sulfan-yl)acrylonitrile.

The title compound, C(17)H(14)Cl(2)N(2)O(3)S(2), and the 4-methyl-anilino analogue reported in the following paper have been used as starting materials to develop benzothia-zine derivatives with anti-malarial activity. The mol-ecule displays an E (trans) configuration about the central double bond. Due to conjugation in the C=C-C N group, the putative single bond shows a significant shortening [1.421 (3) Å]. The mol-ecule has a six-membered ring involving an intra-molecular N-H⋯O(sulfon-yl) bond, which is an example of resonance-assisted hydrogen bonding. There is also an intra-molecular N-H⋯Cl hydrogen bond. In the crystal structure, bonds of the C-H⋯O(sulfon-yl) type form chains that run along [101], while N-H⋯O(sulfon-yl) bonds connect centrosymmetrically related molecules in pairs of these chains, forming ribbons. Comparison of the N⋯O distances in the intra- and inter-molecular N-H⋯O(sulfon-yl) bonds reveals that the π-bond co-operativity results in a strengthening of the intra-molecular hydrogen bond. There are also π-π inter-actions between benzene rings of pairs of centrosymmetrically related mol-ecules [centroid-centroid distance = 3.8612 (13) Å], as well as C-H⋯π interactions.