Crystal structures of methyl 3-phenyl-4,5-dihydro-1H,3H-benzo[4,5]imidazo[2,1-c][1,4]oxazepine-4-carboxylate and methyl 1-methyl-3-phenyl-4,5-dihydro-1H,3H-benzo[4,5]imidazo[2,1-c][1,4]oxazepine-4-carboxylate

In two benzo[4,5]imidazo[2,1-c][1,4]oxazepine-4-carboxylates, the seven-membered oxazepane rings both have a twist-chair conformation. The dihedral angle between the phenyl ring and the benzimidazole ring system is significantly smaller in one of the compounds, viz. 73.42 (10) compared to 83.07 (17)°.


Chemical context
Fused oxazepinone derivatives have attracted considerable attention owing to their promising biological activities, such as anticancer, anti-HIV, antidepressant and antitumor activities (Liu et al., 2011). Tumor growth requires the support of an associated blood supply, making tumor vasculature a potential target for anticancer therapy. This principle has inspired decades of research into the pathways of angiogenesis (the formation of new blood vessels), leading to the identification of a family of vascular endothelial growth factors (VEGFs) that stimulate this process (Edwards et al., 2011). Sevenmembered oxygen heterocycles are ubiquitous in natural products and show a wide spectrum of biological activity (Bera et al., 2014).

Supramolecular features
In the crystal of (I), molecules stack in a herringbone fashion and are linked by C-HÁ Á ÁO hydrogen bonds, forming chains along the a-axis direction (Table 1 and Fig. 3).
In the crystal of (II), there are no significant intermolecular interactions present.

Database survey
In the Cambridge Structural Database (Version 5.35, last update May 2014;Groom & Allen, 2014) there are a large number of compounds containing an oxazepine-type ring, but only one entry was found for such a ring fused to a benzimidazole unit. This compound, 1H,3H-[1,4][4,3-a]benzimidazole (UQILOW;Zhang et al., 2011), has an oxazepino ring with a C C bond in the seven-membered ring.

Synthesis and crystallization
A mixture of Z-methyl-2-(bromomethyl)-3-phenylacrylate (1.0 mol) and (1H-benzo[d]imidazole-2-yl)methanol (1.1 mol) for (I), but (1H-benzo[d]imidazole-2-yl)ethanol (1.1 mol) for (II), together with CS 2 CO 3 (1 mol) in CH 3 CN (10 ml) was stirred for 8 h. After completion of the reactions, monitored by TLC, the solvents were evaporated under reduced pressure. The residues were diluted with ethyl acetate then washed with brine and water. The organic layers were separated and the residues were subjected to column chromatography using ethyl acetate and hexane (2:8) as eluent. The products were dissolved in chloroform and heated for 2 min. The resulting solutions were subjected to crystallization by slow evaporation of the solvent for 48 h resulting in the formation of colourless block-like crystals of compounds (I) and (II).  The molecular structure of compound (I), with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 3
A view along the b axis of the crystal packing of compound (I). The hydrogen bonds are shown as dashed lines (see Table 1 for details).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. In both compunds, the C-bound H atoms were positioned geometrically and allowed to ride on their parent atoms: C-H = 0.93-0.98 Å with U iso (H) = .2U eq (C) or 1.5U eq (Cmethyl).    Hydrogen site location: inferred from neighbouring sites H-atom parameters constrained

(I) Methyl 3-phenyl-1,3,4,5-tetrahydro-2-benzoxepine-4-carboxylate
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.13 e Å −3 Δρ min = −0.13 e Å −3 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.