Crystal structure of ethyl 2-(3,5-difluorophenyl)quinoline-4-carboxylate

In the title compound, C18H13F2NO2, the two rings of the quinoline system are fused almost coaxially, with a dihedral angle between their planes of 2.28 (8)°. The plane of the attached benzene ring is inclined to the plane of the quinoline system by 7.65 (7)°. The carboxylate group attached to the quinoline system is in an antiperiplanar conformation. There is a short intramolecular C—H⋯O contact involving the carbonyl group. In the crystal, molecules are linked via C—H⋯O hydrogen bonds, forming chains lying in the (1-10) plane.


S1. Comment
Quinoline derivatives are well known for their wide range of biological and pharmaceutical activities and are prevalent in pharmacologically active natural and synthetic compounds. Quinoline-4-carboxylates are potential 5HT 3 antagonizer and also they possess anti-emetic activity. In view of their broad spectrum of medicinal properties and in continuation of our work on new quinoline-based therapeutic agents (Pradeep et al., 2014, Shrungesh Kumar et al., 2015, we have synthesized the title compound and report herein on its crystal structure. The structure of the compound is shown in Fig. 1. The dihedral angle between the benzene ring and the quinoline ring system is 7.65 (7)  In the crystal, molecules are linked via C-H···O hydrogen bonds forming chains lying in the (110) plane. (Fig. 2 and Table 1).

S2. Synthesis and crystallization
To a solution of 2-(3,5-difluorophenyl)quinoline-4-carboxylic acid (0.5 g) in 20 ml of EtOH, 1 ml of H 2 SO 4 (conc.) was added. The resulting reaction mixture was refluxed for 15 h. Solvent was removed under reduced pressure and the residue was partitioned between EtOAc and saturated NaHCO 3 solution. The organic layer was washed with water and brine, dried over anhydrous Na 2 SO 4 , filtered, and condensed to give the title compound as a white solid (yield: 93%). The compound was dissolved in dimethylformamide and the solution was gently heated and left undisturbed. Brown, rectangular crystals grew after 12 days by slow evaporation of the solvent.

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All the H atoms were fixed geometrically (C-H= 0.93-0.96 Å) and allowed to ride on their parent atoms with U iso (H) = 1.5U eq (C) for methyl H atoms and 1.2U eq (C) for other H atoms.
supporting information

Figure 1
View of the molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A view along the a axis of the crystal packing of the title compound. Hydrogen bonds are shown as dashed lines (see Table 1 for details).

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.