1-[2-(4-Chlorophenyl)-5-phenyl-2,3-dihydro-1,3,4-oxadiazol-3-yl]ethanone

In the title compound, C16H14ClN3O2, the 2,3-dihydro-1,3,4-oxadiazole ring [maximum deviation = 0.030 (1) Å] and the pyridine ring [maximum deviation = 0.012 (1) Å] are inclined slightly to one another, making a dihedral angle of 11.91 (5)°. The chloro-substituted phenyl ring is almost perpendicular to the 2,3-dihydro-1,3,4-oxadiazole and pyridine rings at dihedral angles of 86.86 (5) and 75.26 (5)°, respectively. In the crystal, π–π [centroid–centroid distance = 3.7311 (6) Å] and C—H⋯π interactions are observed.

Cg3 is the centroid of the C8-C13 benzene ring.

Comment
Oxadiazole, a five-membered heterocyclic nucleus, has attracted a wide attention of the chemists in search for the new therapeutic molecules. A number of therapeutic agents such as HIV-integrase inhibitor Raltegravir, a nitrofuran antibacterial Furamizole, antihypertensive agents like Tiodazosin and Nesapidil are based on the 1,3,4-oxadiazole moiety.
Keeping in view of the therapeutic importance of 1,3,4-oxadiazoles and pyridines, we synthesized the title compound to study its crystal structure.

Experimental
Schiff base, N′-[(1E)-(4-chlorophenyl)methylene]-4-methylbenzohydrazide (0.5 g, 0.0018 mol) was refluxed with acetic anhydride (3 ml) for 1 h. After the completion of reaction, the excess acetic anhydride was distilled out at reduced pressure and the residue obtained was poured into ice cold water. The solid that was separated out was filtered, washed with water and dried. The crude product was recrystallized from hot ethanol in the form of yellow blocks (0.38 g, 76%).

Refinement
All H atoms were positioned geometrically [C-H = 0.95 or 1.00 Å] and refined using a riding model with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was applied to the methyl groups. The same U ij parameter was used for atoms pair N1/C3. Three outliers (-2 0 2, -2 0 1 and -2 1 1) were omitted in the final refinement.

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids.  (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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. 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 R-factors(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.