(2E)-2-(2,4-Dichlorophenylsulfonyl)-3-(3-methoxyanilino)-3-(methylsulfanyl)acrylonitrile

The title compound, C17H14Cl2N2O3S2, and the 4-methylanilino analogue reported in the following paper have been used as starting materials to develop benzothiazine derivatives with antimalarial activity. The molecule 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 molecule has a six-membered ring involving an intramolecular N—H⋯O(sulfonyl) bond, which is an example of resonance-assisted hydrogen bonding. There is also an intramolecular N—H⋯Cl hydrogen bond. In the crystal structure, bonds of the C—H⋯O(sulfonyl) type form chains that run along [101], while N—H⋯O(sulfonyl) bonds connect centrosymmetrically related molecules in pairs of these chains, forming ribbons. Comparison of the N⋯O distances in the intra- and intermolecular N—H⋯O(sulfonyl) bonds reveals that the π-bond co-operativity results in a strengthening of the intramolecular hydrogen bond. There are also π–π interactions between benzene rings of pairs of centrosymmetrically related molecules [centroid–centroid distance = 3.8612 (13) Å], as well as C—H⋯π interactions.

The X-ray structure determination showed that there is one molecule per asymmetric unit ( Fig. 1 (Allen, 2002) produced no structures with the same central fragment (i.e. excluding the phenyl rings) of (I) for proper comparison, but a search for the more restricted fragment X-C(CN)═C(SMe)-N(H)-Y gave three comparable structures, viz. TAKDOZ (Krivokolysko et al., 2002), AJULUM (Kennard et al., 2003) and DALVES (Song et al., 2005).
The title compound displays a six-membered ring involving an intramolecular N-H···O(sulfonyl) bond (Table 1), which is an example of resonance-assisted hydrogen bonding (RAHB) (Gilli et al., 1989), as suggested by the ring bond lengths.
In the crystal structure ( Fig. 2) bonds of the C-H···O(sulfonyl) type form chains that run along [1 0 1], while N-H···O(sulfonyl) bonds connect centrosymmetrycally related atoms of pairs of these chains, to form ribbons. Comparison of the N···O distances of the intra-and intermolecular N-H···O(sulfonyl) bonds reveals that the π-bond cooperativity results in a strengthening of the intramolecular hydrogen bond, as indicated by the significant shortening of the corresponding N···O distance. There are also π-π interactions between phenyl rings of pairs of centrosymmetrically related molecules, with Cg1···Cg2(2 -x, 1 -y, -z), 3.8612 (13) Å (Cgm: centroid of ring Cm1-Cm6, m = 1, 2).

supplementary materials sup-2 Experimental
To a solution of 2,4-dichlorobenzenosulfonylacetonitrile (1.50 g, 6.1 mmol) and KOH (0.46 g, 8.1 mmol) in anhydrous dioxane (10 ml) at 0 °C, was added dropwise 3-methoxyphenylisothiocianate (1.00 g, 6.1 mmol) dissolved in anhydrous dioxane (3 ml). The resulting solution was stirred for 4 h at room temperature and then was added iodomethane (0.87 g, 6.1 mmol) and the mixture was stirred by 5 h at room temperature. The solvent was removed under reduced pressure and the residue was dissolved in dichloromethane (20 ml), washed with water, brine, dried over anhydrous sodium sulfate, filtered and concentrated to dryness. The solid was purified by recrystallization from ethanol. Yield: 1.91 g (74%). Crystals suitable for X-ray analysis were obtained during the recrystallization.

Refinement
Hydrogen atoms were placed in calculated positions using a riding atom model with fixed C-H distances [0.86 Å for N, 0.93 Å for C(sp 2 ), 0.96 Å for C(sp 3 )] and U iso = p U eq (parent atom) [p = 1.2 for N and C(sp 2 ), 1.5 for C(sp 3 )].   as those based on F, and R-factors based on ALL data will be even larger.