Crystal structure of 2-(adamantan-1-yl)-5-(4-bromophenyl)-1,3,4-oxadiazole

In the title molecule, C18H19BrN2O, the benzene ring is inclined to the oxadiazole ring by 10.44 (8)°. In the crystal, C—H⋯π interactions link the molecules in a head-to-tail fashion, forming chains extending along the c-axis direction. The chains are further connected by π–π stacking interactions, with centroid–centroid distances of 3.6385 (7) Å, forming layers parallel to the bc plane.

In the title compound ( Fig. 1), the benzene (C1-C6) ring is inclined relative to the oxadiazole (O1/N1/N2/C7/C8) ring by a dihedral angle of 10.44 (8)%. Bond lengths (Allen et al., 1987) and angles in the title compound are within normal ranges and are comparable with those reported earlier for the structure of related compounds (Cordes et al., 2011;Franco et al., 2003). In the crystal structure, the molecules are connected into head-to-tail fashion to form chains extending along the c axis via C-H···π interactions (Table 1, Fig. 2) involving the centroid of the C1-C6 benzene ring (Cg1). In addition, π-π interactions (Cg1··· Cg1 i = 3.6385 (7) Å; symmetry code: (i) -x, -y, 1-z) link the chains into layers parallel to the bc plane.

S2. Experimental
The title compound was prepared following our previously described method (Kadi et al., 2007). A mixture of the 4bromobenzoic acid hydrazide (2.15 g, 0.01 mol), 1-adamantane carboxylic acid (1.8 g, 0.01 mol) and phosphorus oxychloride (8 ml) was heated under reflux for 1 h. On cooling, crushed ice (50 g) was added cautiously and the mixture was stirred for 30 min. The separated crude product was filtered, washed with water, then with a saturated sodium hydrogen carbonate solution and finally with water, dried and crystallized from EtOH/ (Ar-C), 163.56 (Oxadiazole C-5), 172.85 (Oxadiazole C-2).

S3. Refinement
All the H atoms were positioned geometrically (C=H 0.93-0.98 Å) and refined using a riding model with U iso (H) = 1.2 U eq (C).

Figure 1
The molecular structure of the title compound with 50% probability displacement ellipsoids.

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. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Br1 0.032308 (13