(S)-N-{1-[5-(4-Chlorobenzylsulfanyl)-1,3,4-oxadiazol-2-yl]ethyl}-4-methylbenzenesulfonamide

The title compound, C18H18ClN3O3S2, adopts by folding the form of a distorted disc. Interplanar angles are 29.51 (7) and 63.43 (7)° from the five-membered ring to the aromatic systems and 34.80 (6)° between these two latter rings. The absolute configuration was confirmed by determination of the Flack parameter. In the crystal, the molecules are linked by four hydrogen bonds, one classical (N—H⋯N) and three ‘weak’ (C—H⋯O), forming layers parallel to the ac plane; these are in turn linked in the third dimension by Cl⋯N [3.1689 (16) Å] and Cl⋯O [3.3148 (13) Å] contacts to the heterocyclic ring.

The molecule of the enantiomerically pure title compound is shown in Fig. 1. Bond lengths and angles may be regarded as normal. The molecule has considerable potential for flexibility; the shape actually adopted is that of a short cylinder or disc, albeit distorted, in which the rings form part of the circumference. The smallest dimension of the molecular "box" is calculated by the program RPLUTO (CCDC, 2007) as 6.8 Å, which is close to the calculated distance between the para H atoms of a phenyl group (including van der Waals' radii). All three rings are planar within r.m.s. deviations of < 0.01 Å; interplanar angles are 29.51 (7)° and 63.43 (7)° from the five-membered ring to the aromatic systems C8-13 and C16-21 respectively, and 34.80 (6)° between these two latter rings. To close the circumference of the cylinder, the methyl hydrogen H14C approaches the centroid of the ring C16-21 at a distance of 3.08 Å.
The molecular packing is determined by four hydrogen bonds, one classical and three "weak" (including a three-centre system based on H15B), which link the molecules to form layers parallel to the ac plane (Fig. 2). It can be seen that the Cl atoms project out of this plane (the angle between the bond C19-Cl and the plane is 72°) and the Cl atoms thereby form short contacts Cl···N3 3.1689 (16) Å, operator -x, y -1/2, -z + 1/2, and Cl···O1 3.3148 (13) Å, operator -x + 1, y -1/2, -z + 1/2, to the oxadiazole ring, thus linking the layers (Fig. 3). The approximately linear angle C19-Cl···N3 166.31 (8)° is consistent with the description of Cl···N3 as a halogen bond.

Experimental
The title compound was prepared according to a reported procedure (Syed et al., 2011) and recrystallized from acetone/water.

Refinement
The hydrogen at N5 was refined freely. Methyl H atoms were identified in difference syntheses, idealized and refined using rigid groups allowed to rotate but not tip, with C-H 0.98 Å, H-C-H 109.5°. Other H atoms were introduced at the calculated positions and refined using a riding model, with aromatic C-H 0.95, methylene C-H 0.99, methine C-H 1.00 Å. The U iso (H) values were set equal to mU eq (C) of the parent carbons, with m = 1.5 for methyls and 1.2 for all other H.
The absolute configuration (S at C6) was established by the Flack parameter of -0.001 (11). Fig. 1. The molecule of the title compound. Ellipsoids represent 50% probability levels.  Table. H atoms not involved in H bonds are omitted.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Cl 0.05592 (10)