Ethyl 1-(2-hydroxyethyl)-2-phenyl-1H-benzimidazole-5-carboxylate

There are two molecules in the asymmetric unit of the title compound, C18H18N2O3. In each one, the benzimidazole ring system is essentially planar, with maximum deviations of 0.027 (1) and 0.032 (1)Å, and makes dihedral angles of 38.64 (6) and 41.48 (6)°, respectively, with the attached benzene rings. An intramolecular C—H⋯O hydrogen bond is observed in each molecule. The two independent molecules are connected into a dimer by two intermolecular O—H⋯N hydrogen bonds. In the crystal, molecules form a two-dimensional layers parallel to (012) via weak intermolecular C—H⋯O hydrogen bonds. In addition, weak π-π stacking interactions are observed with centroid–centroid distances of 3.5244 (12) and 3.6189 (12) Å.

There are two molecules in the asymmetric unit of the title compound, C 18 H 18 N 2 O 3 . In each one, the benzimidazole ring system is essentially planar, with maximum deviations of 0.027 (1) and 0.032 (1)Å , and makes dihedral angles of 38.64 (6) and 41.48 (6) , respectively, with the attached benzene rings. An intramolecular C-HÁ Á ÁO hydrogen bond is observed in each molecule. The two independent molecules are connected into a dimer by two intermolecular O-HÁ Á ÁN hydrogen bonds. In the crystal, molecules form a twodimensional layers parallel to (012) via weak intermolecular C-HÁ Á ÁO hydrogen bonds. In addition, weakstacking interactions are observed with centroid-centroid distances of 3.5244 (12) and 3.6189 (12) Å .

Comment
Benzimidazole and its derivatives are compounds which are well known in the pharmaceutical and biological fields (Horton et al., 2003). These heterocycles can serve as molecular scaffolds with versatile binding properties via modifications of their functional groups (DeSimone et al., 2004). Suitably substituted benzimidazole derivatives have been reported to show anti-tumor (Gowda et al., 2009), antimicrobial (Tunçbilek et al., 2009) and anti-inflammatory (Achar et al., 2010) activities. On this basis, we report the structure of the title compound.
The two independent molecules are connected into a dimer by two intermolecular O-H···N hydrogen bonds (Table 1).

Experimental
The title compound was synthesised by the addition of sodium sulfite adduct of benzaldehyde (562 mg, 2.67 mmol) to a mixture of ethyl 3-amino-4-(2-hydroxylethylamino) benzoate (300 mg, 1.33 mmol) in 0.5 mL of DMF. Subsequently, the mixture was irradiated at 403K in a microwave reactor for 2 min. After the reaction, the mixture was diluted with 30 mL of EtOAc and washed with 20 mL of H 2 O. The organic layer was collected, dried over Na 2 SO 4 and the solvent was evaporated under pressure to afford the crude product. The product was recrystallised with hot EtOAc which was slowly evaporated to give a single block of clear crystal.

Refinement
The H atoms attached to O1A and O1B were located in a difference map and refined isotropically. The remaining H atoms Hall symbol: -P 1 Mo Kα radiation, λ = 0.71073 Å a = 8.997 (2)

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 > 2sigma(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 )