Crystal structure of 3,5-dimethylphenyl 2-nitrobenzenesulfonate

In the title compound, there are intermolecular S=O⋯N(nitro) interactions, with an O⋯N distance of 2.9840 (18) Å, between inversion-related molecules. The aromatic rings attached to the SO3 group are oriented in a gauche fashion around the ester S—O bond, with a C—S—O—C torsion angle of 84.68 (11)°.

The title compound, C 14 H 13 NO 5 S, was synthesized via a nucleophilic substitution reaction between 3,5-dimethylphenol and 2-nitrobenzenesulfonyl chloride. The aromatic rings attached to the SO 3 group are oriented in a gauche fashion around the ester S-O bond, with a C-S-O-C torsion angle of 84.68 (11) . The molecules form centrosymmetric dimers viastacking interactions between 3,5-dimethylphenyl groups (centroid-centroid distance = 3.709 Å ). An intermolecular S OÁ Á ÁN interaction between the sulfonyl and nitro groups, with an OÁ Á ÁN distance of 2.9840 (18) Å , organizes the dimers into columns extending along [011]. These columns are further assembled into (111) layers through C-HÁ Á ÁO interactions.

Chemical context
Microtubules form a major component of the cytoskeleton and have been implicated in a wide variety of cellular functions, such as cell division (Jordan & Wilson, 2004). Microtubules therefore have been targeted in the design of drugs for the treatment of various forms of cancer (Spencer & Faulds, 1994;Teicher, 2008;Trivedi et al., 2008). For example, Combretastatin A-4 (CA-4) has been shown to target tumor vasculature (Griggs et al., 2001). Most known antimicrotubules have poor biopharmaceutical properties, uch as chemoresistance and toxicity (Islam et al., 2003;Fortin et al., 2011).
Research in the field for the synthesis of new antimicrotubule compounds has been geared towards compounds with improved biopharmaceutical properties (Fortin et al., 2011). To this end, Fortin and co-workers have designed and synthesized various sulfonate derivatives, which have been The structures of CA-4 and sulfonate analogues, where R 1 and R 2 are substituents on the sulfonyl and phenoxy benzene rings, respectively. tested as new tubulin inhibitors mimicking Combretastatin A-4 ( Fig. 1).
A series of sulfonate derivatives have shown promise as anticancer drugs, with some having lower toxicity than CA-4 (Fortin et al., 2011). We embarked on the synthesis of sulfonate derivatives with the long-term goal of investigating the effect of the benzene-ring substituents on the cytotoxicity of the sulfonate derivatives. To the best of our knowledge, despite the simplicity of the sulfonate derivatives, there has been no relevant previous crystallographic studies. Therefore, we report here the synthesis and crystal structure of 3,5-dimethylphenyl 2-nitrobenzenesulfonate.

Structural commentary
In the title molecule ( Fig. 2), the O1 S1 O2 and C1-S1-O3 bond angles of 119.41 (7) and 104.16 (6) are typical for phenyl benzenesulfonates with a gauche conformation around the ester S-O bond. The torsion angle C1-S1-O3-C7 around the ester bond is À84.68 (11) . Owing to steric hindrance between the ortho substituents of the benzene ring, the nitro group is twisted relative to the benzene best plane by 39.91 (2) , so that the shortest contact of 2.7941 (16) Å between the O atoms of these groups is close to the sum of the van der Waals radii.

Supramolecular features
The molecules of the title compound form centrosymmetric dimers via intermolecularstacking interactions between the relatively electron-rich C7-C12 benzene rings (Fig. 3), with a plane-to-plane distance of 3.4147 (15) Å . The aromatic rings are stacked with an offset, and the distance between the centroids of these rings is 3.709 (12) Å . Another centrosymmetric dimer is formed by an S OÁ Á ÁN interaction, with an N1Á Á ÁO2 interatomic distance of 2.9840 (18) Å . OÁ Á ÁN(nitro) interactions between nitro groups have been discussed in the literature (Daszkiewicz, 2013;Caracelli et al., 2014) and we report here the case of sulfonyl and nitro group interactions. Both types of dimers are assembled into a column-type structure extending along [011] (Fig. 4).
There are no classical hydrogen bonds in the crystal structure; however, nonclassical C-HÁ Á ÁO interactions between aromatic-ring H atoms and sulfonyl and nitro group O atoms organize the [011] columns into (111) layers. The geometry of these interactions is given in Table 1.

Database survey
The Cambridge Structural Database (CSD, Version 5.36 with two updates; Groom & Allen, 2014) contains three structures with an o-nitroarylsulfonyl moiety bonded to an aromatic ring through an ester linkage. These are CSD refcodes FEMQUK (Ichikawa et al., 2004), MIBZUT (Pelly et al., 2007), and FEMRIZ (Ichikawa et al., 2004). Like in the title compound, the aromatic substituents of the SO 3 group are oriented gauche around the ester S-O bond and the absolute value of the C-S-O-C torsion angle is in the range 85.9 (3)-103.43 (13) . In each of these structures there are either intraor intermolecular S OÁ Á ÁN interactions between the sulfonate and o-nitro groups.

Figure 2
The molecular structure of the title compound, with displacement ellipsoids shown at the 50% probability level. All H atoms have been omitted for clarity. Color codes: black C, blue N, red O and yellow S.
The product was redissolved in dichloromethane, and the solvent was allowed to evaporate slowly to give large blockshaped crystals that were suitable for analysis by X-ray diffraction (m.p. 374-378 K).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.