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

In the title molecule, C21H24N2O3, the imidazole ring is essentially planar, with a maxium deviation of 0.015 (1) Å. The dihedral angle between the benzene and imidazole rings is 65.47 (6)°. The crystal packing is stabilized by weak intermolecular C—H⋯O and C—H⋯N hydrogen bonds, forming zigzag chains along the c axis. The crystal structure is further stabilized by C—H⋯π interactions.

In the title molecule, C 21 H 24 N 2 O 3 , the imidazole ring is essentially planar, with a maxium deviation of 0.015 (1) Å . The dihedral angle between the benzene and imidazole rings is 65.47 (6) . The crystal packing is stabilized by weak intermolecular C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds, forming zigzag chains along the c axis. The crystal structure is further stabilized by C-HÁ Á Á interactions.

Comment
Benzimidazole derivatives are reported to be physiologically and pharmacologically active and find applications in the treatment of several diseases, such as epilepsy, diabetes and infertility (Orjales et al., 1997). In addition, they also show clinical benefit toward breast cancer (Andrzejewska et al., 2002), leukemia (Garuti et al., 2000), tumor cells (Lukevics et al., 2001) and possess potent antiviral activities (Komazin et al., 2003). We present here the crystal structure of the title compound.
The organic layer was collected, dried over Na 2 SO 4 and then evaporated in vacuo to yield the crude product. The product was recrystallised from EtOAc as colourless crystals.

Refinement
All hydrogen atoms were positioned geometrically [C-H = 0.93 -0.97 Å] and were refined using a riding model, with U iso (H) = xU eq (C), where x = 1.5 for methyl H and 1.2 for all other H atoms. A rotating group model was applied to the methyl groups. In the absence of significant anomalous scattering effects, 3066 Friedel pairs were merged. Fig. 1. The asymmetric unit of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Hydrogen atoms are shown as spheres of arbitrary radius.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
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 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 > 2σ(F 2 ) is used only for calculating Rfactors(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 O1 0.12374 (8