4-Chloro-N-[3-methyl-1-(5-thioxo-4,5-dihydro-1,3,4-oxadiazol-2-yl)butyl]benzamide

In the title compound, C14H16ClN3O2S, the dihedral angle between the 4-chlorophenyl and 1,3,4-oxadiazole rings is 67.1 (1)° and the orientation of the amide N—H and C=O bonds is anti. In the crystal, molecules are linked by N—H⋯O and N—H⋯S hydrogen bonds.

In the title compound, C 14 H 16 ClN 3 O 2 S, the dihedral angle between the 4-chlorophenyl and 1,3,4-oxadiazole rings is 67.1 (1) and the orientation of the amide N-H and C O bonds is anti. In the crystal, molecules are linked by N-HÁ Á ÁO and N-HÁ Á ÁS hydrogen bonds.

Comment
The present oxadiazole derivate is in continuation to our previous work of the thiadiazole scaffold compounds and their biological activity (Tu et al., 2008). The title compound (Figure 1) was synthesized according to literature procedures (Ginzel et al., 1989;Boland et al., 2006;Havaldar & Patil 2009). Here, we report the structure of the title compound.
The oxadiazole ring is essentially planar and is inclined at 67.1 (1)° with respect to the p-cholobenzene ring. The N2=C2 and S1=C1 double bonds agree with the corresponding distances in three structures containing similar systems (Du et al., 2004;Ziyaev et al., 1992;Zareef et al., 2006). The conformations of the N-H and C=O bonds are anti with respect to each other. The structure is stabilized by a network of intermolecular hydrogen bonds of the type N-H···S (Table 1, Figure 2).

Experimental
To a stirred solution of DL-leucine methyl ester hydrochloride (0.03 mol) in CH 2 Cl 2 (20 ml) was added triethylamine (0.06 mol) at 273 K. After 0.5 h, a solution of p-chlorobenzoic acid chloride (0.03 mol) in CH 2 Cl 2 (10 ml) was added. The mixture was stirred for 2 h at 273 K, then allowed to warm to r.t. for 24 h. Washed with 10% HCl, 1 N NaOH and water. The organic layer was evaporated in vacuo and the residue was recrystallized from methanol to give corresponding amides as a white solid.
A mixture of the amides (0.02 mol) and 80% hydrazine monohydrate (0.04 mol) in absolute methanol (20 ml) was heated under reflux over night. After cooling, a white solid was separated and recrystallized from methanol to give corresponding hydrazide.
A mixture of the hydrazide (0.01 mol), KOH (0.01 mol), CS 2 (0.05 mol), and ethanol (70 ml) was heated under reflux with stirring for 12 h. Ethanol was distilled off under reduced pressure and the residue was dissolved in water and then acidified with 10% HCl. The resulting precipitate was filtered, washed with water, and recrystallized from ethanol. Colourless blocks of (I) precipitated after several days.

Refinement
H atoms were positioned geometrically and refined using a riding model using SHELXL97 default values (Uiso(H) = 1.2 Ueq(C) for CH and CH 2 groups and Uiso(H) = 1.5 Ueq(C) for CH 3 ).
supplementary materials sup-2 Figures Fig. 1. Molecular structure of (I) with displacement ellipsoids drawn at the 50% probability level. Fig. 2. The crystal packing of (I), viewed along the a axis with hydrogen bonds drawn as dashed lines.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Cl1