Ethyl 2-(4-nitrophenyl)-1-[3-(2-oxopyrrolidin-1-yl)propyl]-1H-benzimidazole-5-carboxylate

In the title compound, C23H24N4O5, the essentially planar benzimidazole ring system [maximum deviation = 0.008 (2) Å] forms a dihedral angle of 39.22 (7)° with the attached nitrobenzene ring. The pyrrolidin-2-one ring adopts an envelope conformation with a C atom as the flap. In the crystal, molecules are connected by C—H⋯O interactions, forming sheets propagating in (011). The crystal packing also features weak π–π stacking interactions [centroid–centroid = 3.6746 (12) Å].

In the title compound, C 23 H 24 N 4 O 5 , the essentially planar benzimidazole ring system [maximum deviation = 0.008 (2) Å ] forms a dihedral angle of 39.22 (7) with the attached nitrobenzene ring. The pyrrolidin-2-one ring adopts an envelope conformation with a C atom as the flap. In the crystal, molecules are connected by C-HÁ Á ÁO interactions, forming sheets propagating in (011). The crystal packing also features weakstacking interactions [centroid-centroid = 3.6746 (12) Å ].

Experimental
Ethyl 3-amino-4-(3(2-oxopyrrolidin-1yl)propylamino)benzoate (0.84 mmol) and sodium metabisulfite adduct of 4-nitrobenzaldehyde (1.68 mmol) were dissolved in DMF. The reaction mixture was reflux at 130 °C for 2 hrs. After completion, the reaction mixture was diluted in ethyl acetate (20 ml) and washed with water (20 ml). The organic layer was collected, dried over Na 2 SO 4 and the evaporated in vacuo to yield the product. The product was recrystallised from ethyl acetate as orange blocks.

Refinement
All the H atoms were positioned geometrically and refined using a riding model with with C-H = 0.95-0.99 Å. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms.   (011). Hydrogen atoms that not involved in hydrogen bonding (dashed lines) are omitted for clarity.

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 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.