Ethyl 1-sec-butyl-2-(4-methoxyphenyl)-1H-benzimidazole-5-carboxylate

In the title molecule, C21H24N2O3, the dihedral angle between the benzene and imidazole rings is 66.33 (13)°. The imidazole ring is essentially planar, with a maximum deviation of 0.004 (2) Å. In the crystal structure, molecules are connected by weak C—H⋯O hydrogen bonds, forming chains along the b axis

In the title molecule, C 21 H 24 N 2 O 3 , the dihedral angle between the benzene and imidazole rings is 66.33 (13) . The imidazole ring is essentially planar, with a maximum deviation of 0.004 (2) Å . In the crystal structure, molecules are connected by weak C-HÁ Á ÁO hydrogen bonds, forming chains along the b axis

Comment
The benzimidazole nucleus is the key building block for a variety of compounds that play crucial roles in the function of a number of biologically important molecules (Tanious et al., 2004). Benzimidazole derivatives have shown different therapeutic properties such as antihypertensive (Kohara et al., 1996) andanti-inflammatory (Mader et al., 2008) activities.
2-(substitutedphenyl)benzimidazoles with various types of biological activities, such as antibacterial (Coburn et al., 1987) and antiviral (Roth et al., 1997), have been reported. Due to their importance, the crystal structure determination of the title compound was carried out and the results are presented here.

Experimental
Ethyl-3-amino-4-(sec-butylamino)benzoate (200 mg, 0.84 mmol) and the sodium metabisulfite adduct of 4-methoxy benzaldehyde (406 mg, 1.68 mmol) were dissolved in DMF. The reaction mixture was irradiated under microwave conditions at 403 K for 2 minutes. After completion of the reaction, the reaction mixture was diluted in EtOAc (20 ml) and washed with H 2 O (20 ml). The organic layer was collected, dried over Na 2 SO 4 and then evaporated in vacuo to yield the crude product.
The product was recrystallized from hot EtOAc to afford the title compound as colorless crystals.

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 > 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.