tert-Butyl 2-(1H-benzimidazol-1-yl)acetate

In the title compound, C13H16N2O2, the planes of the benzimidazole ring system and the acetate O—C=O fragment make a dihedral angle of 84.5 (3)°. In the crystal, molecules are connected through C—H⋯N hydrogen bonds to form infinite chains in the [-110] direction.

In the title compound, C 13 H 16 N 2 O 2 , the planes of the benzimidazole ring system and the acetate O-C O fragment make a dihedral angle of 84.5 (3) . In the crystal, molecules are connected through C-HÁ Á ÁN hydrogen bonds to form infinite chains in the [110] direction.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
The title compound is the condensation product of the reaction of benzimidazole with tert-butyl chloroacetate. The benzimidazole ring make a dihedral angle of 84.5 (3)° with the plane passing through the acetate group, C9/O1/O2. This value is comparable to those calculated for some similar structures (Al-Mohammed et al., 2012;Fu et al., 2009;Xu et al., 2008). The crystal packing structure contains chains in [-1 1 0] direction formed by C3-H3···N2 hydrogen bonds between the adjacent molecules. Intramolecular C-H···O hydrogen bonding also occurs.

Experimental
Sodium hydroxide (0.5 g, 125 mmol) was added to a solution of benzimidazole (1.48 g, 125 mmol) in DMF (20 ml), followed by addition of tert-butyl chloroacetate (1.82 ml, 127 mmol). The mixture was refluxed for 1 h. The reaction mass was quenched with cold water (50 ml) and extracted by dichloromethane (3 x 25 ml). The combined organic layers was washed with cold water and brine and dried over anhydrous sodium sulfate. The solvent was evaporated under vacuum and the formed amorphous solid was stirred in n-hexane (30 ml) at room temperature. The solid was filtered, washed with hexane (2 x 20 ml), and recrystallized from ethyl acetate to afford colorless crystals of the title compound (melting point = 367-369 K).

Refinement
Hydrogen atoms were placed at calculated positions and refined in riding mode with C-H distances of 0.95 (aromatic), 0.98 (methyl) and 0.99 (methylene) Å, and U iso (H) set to 1.2 (1.5 for methyl) U eq (carrier atoms). In the absence of significant anomalous scattering effects, Friedel pairs have been merged.  The molecular structure of the title compound showing displacement ellipsoids at the 50% probability level. Hydrogen atoms are drawn as spheres of arbitrary radius.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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.