Ethyl 1-sec-butyl-2-phenyl-1H-benzimidazole-5-carboxylate

In the title molecule, C20H22N2O2, the benzimidazole ring system is essentially planar, with a maximum deviation of 0.024 (1) Å. The dihedral angle between the phenyl and benzimidazole ring system is 43.71 (5)°. The atoms of the butyl group are disordered over two sets of sites with occupancies of 0.900 (4) and 0.100 (4). In the crystal structure, molecules are connected by weak intermolecular C—H⋯O hydrogen bonds, forming chains along the b axis. The crystal structure is further stabilized by C—H⋯π interactions.

In the title molecule, C 20 H 22 N 2 O 2 , the benzimidazole ring system is essentially planar, with a maximum deviation of 0.024 (1) Å . The dihedral angle between the phenyl and benzimidazole ring system is 43.71 (5) . The atoms of the butyl group are disordered over two sets of sites with occupancies of 0.900 (4) and 0.100 (4). In the crystal structure, molecules are connected by weak intermolecular C-HÁ Á ÁO hydrogen bonds, forming chains along the b axis. The crystal structure is further stabilized by C-HÁ Á Á interactions.  (1997). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 Table 1 Hydrogen-bond geometry (Å , ).

Comment
The benzimidazole motif is an important pharmacophore in drug discovery (Spasov et al., 1999). Substituted benzimidazole derivatives have diverse therapeutic applications as they exhibit antihistamine (Grassmann et al., 2002), anti-HIV-1 (Evans et al., 1997), antitumour (White et al., 2004 and potential anticancer activities (Demirayak et al., 2002). In view of their importance in the field of drug discovery, the crystal structure determination of the title compound was carried out and the results are presented here.
In the asymmetric unit of the title compound ( Fig. 1), the benzimidazole ring system is essentially planar with a maximum deviation of 0.024 (1)Å for atom N2. The butyl group is disordered over two sites with occupancies of 0.900 (4) and 0.100 (4).

Experimental
A solution of ethyl-3-amino-4-(sec-butylamino) benzoate (200 mg, 0.84 mmol) and sodium bisulfite adduct of benzaldehyde (353 mg, 1.68 mmol) in DMF was treated under microwave conditions at 130°C for 2 minutes. The reaction mixture was then diluted in EtOAc (20 mL) and washed with H 2 O (20 mL). The organic layer was collected and dried over Na 2 SO 4 .
The solvent was removed under reduced pressure to afford the crude product, which upon recrystallisation from EtOAc, revealed the title compound as colourless crystals.
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 )
x y z U iso */U eq Occ. (