Ethyl 2-(1,3-benzodioxol-5-yl)-1-[3-(1H-imidazol-1-yl)propyl]-1H-benzimidazole-5-carboxylate

In the title compound, C23H22N4O4, the essentially planar [maximum deviation = 0.022 (1) Å] benzimidazole ring system forms dihedral angles of 86.16 (7) and 37.38 (6)°, respectively, with the imidazole and benzene rings. The dioxolane ring adopts an envelope conformation with the methylene C atom at the flap. In the crystal, C—H⋯O and C—H⋯N interactions link the molecules into a ribbon along the a axis. The crystal packing is further stabilized by weak π–π stacking interactions [centroid–centroid distances = 3.5954 (8) and 3.7134 (8) Å] and C—H⋯π interactions.

In the title compound, C 23 H 22 N 4 O 4 , the essentially planar [maximum deviation = 0.022 (1) Å ] benzimidazole ring system forms dihedral angles of 86.16 (7) and 37.38 (6) , respectively, with the imidazole and benzene rings. The dioxolane ring adopts an envelope conformation with the methylene C atom at the flap. In the crystal, C-HÁ Á ÁO and C-HÁ Á ÁN interactions link the molecules into a ribbon along the a axis. The crystal packing is further stabilized by weakstacking interactions [centroid-centroid distances = 3.5954 (8) and 3.7134 (8) Å ] and C-HÁ Á Á interactions.

Experimental
Ethyl-4-[3-(1H-imidazol-1-yl)propylamino]-3-aminobenzoate (0.84 mmol) and sodium metabisulfite adduct of piperonal (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.

Refinement
All the H atoms positioned geometrically and refined using a riding model with C-H = 0.95-0.99 Å. The U iso values were constrained to be 1.5U eq (methyl-H atom) and 1.2U eq (other H atoms). The rotating model group was applied for the methyl group.    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.