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

In the title compound, C20H21ClN2O2, the ethyl 1H-benzimidazole-5-carboxylate ring system, excluding the methylene and methyl H atoms, is almost planar, with a maximum deviation of 0.055 (1) Å, and makes a dihedral angle of 40.63 (4)° with the benzene ring. The sec-butyl group is disordered over two positions, with refined site occupancies of 0.855 (4) and 0.145 (4). In the crystal, molecules are linked into chains along [010] via intermolecular C—H⋯O hydrogen bonds and are further interconnected by C—H⋯Cl interactions into two-dimensional networks parallel to (001). The crystal structure is further consolidated by C—H⋯π interactions.

In the title compound, C 20 H 21 ClN 2 O 2 , the ethyl 1H-benzimidazole-5-carboxylate ring system, excluding the methylene and methyl H atoms, is almost planar, with a maximum deviation of 0.055 (1) Å , and makes a dihedral angle of 40.63 (4) with the benzene ring. The sec-butyl group is disordered over two positions, with refined site occupancies of 0.855 (4) and 0.145 (4). In the crystal, molecules are linked into chains along [010] via intermolecular C-HÁ Á ÁO hydrogen bonds and are further interconnected by C-HÁ Á ÁCl interactions into two-dimensional networks parallel to (001). The crystal structure is further consolidated by C-HÁ Á Á interactions.

Related literature
For the synthesis of the title compound, see: Arumugam et al. (2010a,b,c). For general background to and the therapeutic properties of benzimidazole derivatives, see: Bonfanti et al. (2008); Evans et al. (1997); Hori et al. (2002); Snow (2007). For a related structure, see: Eltayeb et al. (2009). For reference bond lengths, see: Allen et al. (1987). For the stability of the temperature controller used in the data collection, see : Cosier & Glazer (1986 Table 1 Hydrogen-bond geometry (Å , ).

Comment
Benzimidazole is an important pharmacophore in drug discovery and its derivatives have shown various therapeutic properties such as antiviral (Bonfanti et al., 2008) and anti-HIV-1 (Evans et al., 1997) activities. Benzimidazoles are used as biomimetics of guanine residues and selectively inhibit endothelial cell growth and suppress angiogenesis in vitro and in vivo (Hori et al., 2002). In particular, substituted benzimidazole derivatives are also inhibitors of tyrosine kinase and are useful for inhibiting cell proliferation for the treatment of cancer (Snow et al., 2007). In view of their importance, the crystal structure determination of the title compound was carried out and the results are presented here.
The molecular structure of the title compound is shown in Fig. 1. The ethyl 1H-benzimidazole-5-carboxylate ring system (O1/O2/N1/N2/C7-C16), excluding methylene and methyl H atoms, is almost planar, with a maximum deviation of 0.055 (1) Å for atom O2, and makes a dihedral angle of 40.63 (4)° with the benzene (C1-C6) ring. The sec-butyl group is disordered over two positions with refined site-occupancies of 0.855 (4) and 0.145 (4). The bond lengths (Allen et al., 1987) and angles in the title compound are within normal ranges and comparable to those in a related crystal structure (Eltayeb et al., 2009).

Experimental
The title compound was synthesized using previously reported procedures (Arumugam et al., 2010a,b,c). The crude product was recrystallized from ethyl acetate to yield the title compound as colourless crystals.

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.98 Å and 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 for the methyl groups.