Ethyl 2-oxo-3-(3-phthalimidopropyl)-2,3-dihydro-1H-1,3-benzimidazole-1-carboxylate

In the title compound, C21H19N3O5, the phthalimide and benzamidazole ring systems are linked by a propyl chain. The benzamidazole unit also carries an ethoxycarbonyl substituent. The phthalimido and benzimidazole ring systems are essentially planar, the maximum deviations from their mean planes being 0.008 (2) and 0.020 (2) Å, respectively. The two ring systems are almost orthogonal to one another, making a dihedral angle of 82.37 (8)°. In the crystal, C—H⋯O hydrogen bonds and C—H⋯π contacts stack the molecules along the b axis.

In the title compound, C 21 H 19 N 3 O 5 , the phthalimide and benzamidazole ring systems are linked by a propyl chain. The benzamidazole unit also carries an ethoxycarbonyl substituent. The phthalimido and benzimidazole ring systems are essentially planar, the maximum deviations from their mean planes being 0.008 (2) and 0.020 (2) Å , respectively. The two ring systems are almost orthogonal to one another, making a dihedral angle of 82.37 (8) . In the crystal, C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á contacts stack the molecules along the b axis.
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009) and publCIF (Westrip, 2010). The benzimidazole nucleus is of significant importance in medicinal chemistry. Several publications report benzimidazole-containing compounds showing biological activities (Zarrinmayeh et al., 1998). Substituted benzimidazole derivatives have found commercial applications in veterinary medicine as anthelmintic agents (Spasov et al., 1999). Functionalized benzimidazoles represent an important class of N-containing heterocyclic compounds and have received considerable attention in recent times because of their applications as antiulcer, antihypertensive, antiviral, antifungal, anticancer and antihistamine agents, among others (Gravatt et al., 1994;Horton et al., 2003;Kim et al., 1996;Roth et al., 1997). They are important intermediates in many organic reactions (Bai et al., 2001;Hasegawa et al., 1999) and act as ligands to transition metals for modelling biological systems (Bouwman et al., 1990). Owing to the potential biological and other technical interest of the benzimidazole family of compounds, a number of synthetic strategies have been developed for the preparation of substituted benzimidazoles.
As a continuation of our research into the development of substituted benzimidazol-2-one derivatives (Belaziz et al., 2013) we report here the synthesis of a new benzimidazol-2-one derivative by the reaction of N-(3-bromopropyl)phthalimide with 1-ethoxycarbonyl-benzo[d]imidazol-2(3H)-one using the same conditions to produce the title compound (Scheme 1).
The crystal structure of the title compound is built up from two fused five and six-membered rings (N1C1 to C8) and (N2N3C12 to C18) linked to a (C9 to C11) chain and one of them is linked to an ethoxycarbonyl group (Fig.1). The fused-ring systems are essentially planar, with the maximum deviation of 0.008 (2) Å for C2 atom and 0.020 (2) Å for C14. The dihedral angle between the phthalimido and the benzo[d]imidazol cycles is 82.37 (8)°.

Refinement
All H atoms could be located in a difference Fourier map and were treated as riding with C-H = 0.93 Å (aromatic), C-H = 0.97 Å (methylene) and C-H = 0.96 Å methyl. U iso (H) = 1.2 U eq (aromatic, methylene) and U iso (H) = 1.5 U eq (methyl).

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.