Ethyl 1-(2-hydroxyethyl)-2-p-tolyl-1H-benzimidazole-5-carboxylate

The asymmetric unit of the title compound, C19H20N2O3, contains two molecules (A and B) with slightly different orientations of the ethyl groups with respect to the attached carboxylate groups. Intramolecular C—H⋯O hydrogen bonds generate S(8) ring motifs in both molecules A and B. In each molecule, the benzimidazole ring system is essentially planar, with maximum deviations of 0.023 (1) and 0.020 (1) Å, respectively, for molecules A and B. The dihedral angle between the benzimidazole ring system and the phenyl ring is 37.34 (5)° for molecule A and 42.42 (5)° for molecule B. In the crystal, O—H⋯N and C—H⋯O hydrogen bonds link the molecules into [100] columns with a cross-section of two-molecule by two-molecule wide, and further stabilization is provided by weak C—H⋯π and π–π interactions [centroid separations = 3.5207 (7) and 3.6314 (8) Å].

The asymmetric unit of the title compound, C 19 H 20 N 2 O 3 , contains two molecules (A and B) with slightly different orientations of the ethyl groups with respect to the attached carboxylate groups. Intramolecular C-HÁ Á ÁO hydrogen bonds generate S(8) ring motifs in both molecules A and B. In each molecule, the benzimidazole ring system is essentially planar, with maximum deviations of 0.023 (1) and 0.020 (1) Å , respectively, for molecules A and B. The dihedral angle between the benzimidazole ring system and the phenyl ring is 37.34 (5) for molecule A and 42.42 (5) for molecule B. In the crystal, O-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds link the molecules into [100] columns with a cross-section of twomolecule by two-molecule wide, and further stabilization is provided by weak C-HÁ Á Á andinteractions [centroid separations = 3.5207 (7) and 3.6314 (8) Å ]. For graph-set descriptions of hydrogen-bond ring motifs, see: Bernstein et al. (1995). For closely related benzimidazole structures, see: Arumugam et al. (2010a,b,c). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 Table 1 Hydrogen-bond geometry (Å , ).
In molecule A, the benzimidazole ring system is inclined at dihedral angle of 37.34 (5)° with the C1A-C6A phenyl ring; the respective angle for molecule B is 42.42 (5)°. The geometric parameters are comparable to those reported in closely related benzimidazole structures (Arumugam et al., 2010a,b,c).

Experimental
A solution of ethyl-3-amino-4-(2-hydroxyethylamino) benzoate (0.5 g, 2.22 mmol) and sodium bisulfite adduct of p-methyl benzaldehyde (1.0 g, 4.46 mmol) in DMF was treated under microwave conditions at 403 K. The reaction mixture was then diluted in EtOAc (30 ml) and washed with H 2 O (30 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.
supplementary materials sup-2 Refinement Hydroxy H-atoms were located from the difference Fourier map and allowed to refine freely. The remaining H atoms were place in their calculated positions, with C-H = 0.93-0.97 Å and U iso (H) = 1.2 or 1.5 U eq (C). The rotating group model was applied for the methyl groups. The highest residual electron density peak is 0.49 Å from N2B and the deepest hole is 0.85 Å from C8B. Fig. 1. The molecular structure of (I) with 50% probability displacement ellipsoids for non-H atoms. Intramolecular hydrogen bonds are shown as dashed lines.  Ethyl 1-(2-hydroxyethyl)-2-p-tolyl-1H-benzimidazole-5-carboxylate  Glazer, 1986) operating at 100.0 (1)K.

Figures
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.