3-Benzyl-1-{[3-(4-chlorophenyl)isoxazol-5-yl]methyl}-1H-benzimidazol-2(3H)-one

In the title compound, C24H18ClN3O2, the benzimidazole plane is nearly perpendicular to the phenyl ring and to the isoxazole ring, making dihedral angles of 75.95 (7) and 73.04 (8)°, respectively, but the two residues point in opposite directions with respect to the benzimidazole plane. The dihedral angle between the chlorophenyl and isoxazole rings is 7.95 (8)°. In the crystal, molecules are linked by pairs of C—H⋯O hydrogen bonds into inversion dimers.

In the title compound, C 24 H 18 ClN 3 O 2 , the benzimidazole plane is nearly perpendicular to the phenyl ring and to the isoxazole ring, making dihedral angles of 75.95 (7) and 73.04 (8) , respectively, but the two residues point in opposite directions with respect to the benzimidazole plane. The dihedral angle between the chlorophenyl and isoxazole rings is 7.95 (8) . In the crystal, molecules are linked by pairs of C-HÁ Á ÁO hydrogen bonds into inversion dimers.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Isoxazoline derivatives have attracted considerable attention and are found in many important bioactive heterocycles.
These pharmacophores play an important role in medicinal (Sakuma et al., 2011, Wang et al., 2010 and agrochemical industry (Hu et al., 2010). The integration of isoxazoline moiety in benzimidazole scaffolds may lead to new hybrid molecules containing two pharmacophores in the same molecule with broad biological activity profiles.
As a continuation of our research work devoted to the development of substituted benzimidazol-2-one derivatives (Belaziz et al., 2012), we report in this paper the synthesis of a new isoxazolinylmethyl benzimidazole derivatives. The title compound was obtained by using p-chlorobenzaldoxime to react with the 1-allyl-3-benzyl-benzimidazole in 1,3dipolar cycloaddition.
The title compound is build up from a fused five-and six-membered rings linked, on opposite sides, to a benzyl residue and to a chlorobenzyl-dihydroisoxazole residue (Fig. 1). The benzimidazole plane makes dihedral angles of 75.95 (7) ° and 73.04 (8) ° with the phenyl ring and the isoxazole ring, respectively. The dihedral angle between the chlorophenyl ring and the isoxazole ring is of 7.95 (8) ° while that between the two aromatic six-membered rings is 68.48 (8)°.
In the crystal, the molecules are linked by C-H···O hydrogen bonds to centrosymmetric dimers ( Fig. 2 and Table 2).

Experimental
To 1-allylbenzimidozol-2-one (0.40 g, 2.3 mmol), potassium carbonate (0.63 g, 4,55 mmol) and tetra-n-butylammonium bromide (0.07 g, 0.22 mmol) in DMF (15 ml) was added benzyl chloride (0.32 g, 2.53 mmol). Stirring was continued at room temperature for 6 h. The salt was removed by filtration and the filtrate concentrated under reduced pressure. The residue was separated by chromatography on a column of silica gel with ethyl acetate/ hexane (1/2) as eluent. The compound was recrystallized from hexane/acetate to give colorless crystals. To the obtained compound (1-allyl-3-benzylbenzimidazol-2-one) (0.20 g, 0.76 mmol) was added p-chlorobenzaldoxime (0.15 g, 1 mmol) in chloroform (10 ml) and 4% solution of sodium hypochlorite solution (commercial bleach) (4 ml) at 0°C. Stirring was continued for 6 h. The organic layer was dried and the solvent evaporated under reduced pressure. The residue was then purified by column chromatography on silica gel by using a mixture of hexane and ethyl acetate (1/1) as eluent. Colourless crystals were isolated when the solvent was allowed to evaporate (Yield: 68%; mp: 467 K).

Refinement
All H atoms could be located in a difference Fourier map. Nevertheless, they were placed in calculated positions with C -H = 0.93 Å (aromatic), and C-H = 0.97 Å (methylene) and refined as riding on their parent atoms with U iso (H) = 1.2 U eq (C).   Intermolecular interactions in the title compound building a dimers. Hydrogen bonds are shown as dashed lines. Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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.