Crystal structure of N-{4-[(6-chloropyridin-3-yl)methoxy]phenyl}-2,6-difluorobenzamide

The molecular and crystal structure of N-{4-[(6-chloropyridin-3-yl)methoxy]phenyl}-2,6-difluorobenzamide is reported. The crystal packing is stabilized by N—H⋯N, C—H⋯O, C—H⋯F and C—H⋯π hydrogen bonds supplemented by offset π–π stacking interactions.


Chemical context
Amide derivatives show diverse biological properties, acting as insecticides (Liu et al., 2004a), fungicides (Liu et al., 2004b) and acaricides (Shiga et al., 2003). Amides in regular commercial use include benzamide (flutolanil, fluopicolide), nicotinamide (boscalid) and thiazole carboxamide (thifluzamide, ethaboxam). As a part of our work on the synthesis of novel fluorine-containing compounds with good biological activities, we report herein on the crystal structure of the title compound,(I), Fig. 1.

Structural commentary
The conformation of the N-H and the C O bonds in the amide segment are anti to one another, similar to the conformation observed in another amide compound . The dihedral angle between the two benzene rings is 73.35 (6) while that between the central benzene ring and the chloro-substituted pyridine ring is 81.26 (6). The amide residue C1/N1/C7/O1 lies close to the plane of the central benzene ring, making a dihedral angle of 8.73 (6) . A weak intramolecular C9-H9Á Á ÁO1 hydrogen bond (Table 1) contributes to the planarity of this part of the molecule.

Synthesis and crystallization
Triethylamine (6mmol) was added dropwise to a stirred solution of 4-(6-chloropyridin-3-yl) methoxy aniline (5mmol) and 2,6-difluorobenzoyl chloride (5mmol) in dry dichloromethane (20ml) at 275-277 K. The mixture was stirred at 283-288 K for 2 h, then washed with 0.5% hydrochloric acid solution, and a saturated aqueous solution of sodium hydrogen carbonate, dried and evaporated. The residue was recrystallized from dichloromethane, giving colourless blocks of the title compound after three weeks.

Figure 2
A pair of dimers with hydrogen bonds drawn as blue dashed lines.

Figure 3
Chains of inversion dimers along the c-axis direction. Hydrogen bonds are drawn as dashed lines withand C-HÁ Á Á contacts shown as green dotted lines.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The NH H atom was located in a difference Fourier map and freely refined. The C-bound H atoms were positioned geometrically and refined using a riding model with d(C-H) = 0.93-0.97 Å and U iso (H) = 1.2U eq (C).

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.