Crystal structure of 1-methyl-2-[(E)-2-(4-methylphenyl)ethenyl]-4-nitro-1H-imidazole

In the title molecule, C13H13N3O2, the planes of the benzene and imidazole rings form a dihedral angle of 7.72 (5)°. In the crystal, molecules are linked by weak C—H⋯N and C—H⋯O hydrogen bonds, forming layers parallel to (100). A weak C—H⋯π interaction connects these layers into a three-dimensional network. A π–π stacking interaction, with a centroid–centroid distance of 3.5373 (9) Å, is also observed.


S1. Comment
The imidazole nucleus is an important pharmacophore found in a large number of natural products and synthetic compounds with a wide range of applications which make imidazole derivatives a subject of extensive investigations (Mamedov, et al., 2011;De Luca, 2006;Tanigawara, et al., 1999;Hunkeler, et al., 1981). For example, many synthetic imidazole derivatives are present in a number of bioactive compounds such as fungicides, herbicides, bactericides, antiinflammators, analgesics and anticancers (Teimouri, et al., 2011;Achar, et al., 2010;Özkay, et al., 2010;Shingalapur, et al., 2009). Nitroimidazoles are a particular class of imidazoles principally composed of bioactive substances where their spectrum of action is closely associated with the position of the nitro group on the imidazole ring. Due to their significant biological activity, 5-nitroimidazoles are widely used in medicine as bactericide and parasiticide agents, some of them possess an original activity spectrum especially towards protozoa and strict anaerobic bacteria (Trivedi, et al., 2011;Bhatia, et al., 1984;Hoffer et al., 1974), and others exhibit cytotoxic and radiosensitization activities in vitro and in vivo (Leitsch, et al., 2011;Luo, et al., 2010). However, only few biological properties of 4-nitroimidazoles have been reported in the literature (Saadeh, et al., 2009;Thompson, et al., 2009;Carvalho, et al., 2006). The transposition of a nitro group in 5-nitroimidazoles is a known reaction and constitutes an efficient synthetic procedure of 4-nitroisomers. However, only few examples of this reaction are described using methyl iodide as catalyst (Alliouche, et al. 2014). We report in this paper, the synthesis and structure determination of (E)-1-methyl-2-[(4-methylphenyl)-1-ethenyl]-5-nitroimidazole (I).
The later was easily prepared from its 5-nitro isomer via an intramolecular transposition of the nitro group. The reaction was carried out in nitrobenzene at 433K using catalytic amount of methyl iodide.
The molecular structure of (I) is shown in Fig. 1. The benzene and imidazole ring form a dihedral angle of 7.72 (5)°.

S2. Experimental
The title compound (I) was obtained as yellow solid in 94% yield by heating the corresponding 5-nitroisomer at 433K in nitrobenzene in presence of methyl iodide as catalyst, during 24 h. Suitable crystals were obtained by slow evaporation of a solution of the title compound in water/methanol solution at room temperature.

S3. Refinement
All non-H atoms were refined with anisotropic atomic displacement parameters. All H atoms were located in difference Fourier maps but were introduced in calculated positions and treated as riding on their parent atom (with C-H = 0.93 and 0.96 Å and U iso (H) = 1.5 or 1.2U eq (C).

Figure 1
The molecular structure structure of the title compound with displacement ellipsoids drawn at the 50% probability level.

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.