Crystal structure of N-(2-benzoyl-5-ethynylphenyl)quinoline-2-carboxamide

In the title compound, the quinoline ring system forms a dihedral angle of 20.9 (1)° with ethynyl-substituted benzene ring. The unsubstituted phenyl ring forms a dihedral angles of 52.7 (1)° with the quinoline ring system and 54.1 (1)° with the ethynyl-substituted benzene ring. An intramolecular bifurcated N—H⋯(O,N) hydrogen bond forms S(5) and S(6) rings. In the crystal, weak C—H⋯O hydrogen bonds link the molecules into a three-dimensional network.


Chemical context
Benzophenones are intermediates for the synthesis of pharmaceutical and bioactive materials and are used extensively in the field of medicinal chemistry. The biological activity of these ligands can be attributed to distinct chemical and biochemical advantages: they are chemically more stable than diazo esters, aryl azides and diazirines, and can be manipulated in ambient light and can be activated at 350-360 nm, avoiding protein-damaging wavelengths. These properties produce highly efficient covalent modifications of macromolecules, frequently with remarkable specificity (Dormá n & Prestwich, 1994). Several benzophenones are used in industry, cosmetics, medicine and agriculture (Sweetman et al., 2007), and their role as potential anticancer agents and antibiotics has also been examined. In addition, research has been performed on the use of benzophenones as modulators of GABAA receptors (Kopanitsa et al., 2002), COX-1/COX-2 inhibitors (Dannhardt et al., 2002) and EGFR/erbB2 dual inhibitors (Zhang et al., 2004).

Structural commentary
The molecular structure of the title compound is shown in Fig. 1. The quinoline ring system (C1-C9/N1) is essentially planar, with a maximum deviation of 0.030 (1) for C8 and forms a dihedral angle of 20.9 (1) with ethynyl-substituted benzene ring (C11-C16). The benzoyl ring (C20-C25) forms dihedral angles of 52.7 (1) with the quinoline ring system and 54.1 (1) with the ethynyl-substituted benzene ring. The molecule contains an intramolecular bifurcated N-HÁ Á Á(N,O) hydrogen bond (see Table 1), forming S(5) and S(6) rings, which may influence the conformation of the molecule.

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. Hydrogen bonds are shown as dotted lines.

Figure 2
A partial packing diagram of the title compound, viewed approximately along the b axis, with intermolecular hydrogen bonds shown as black dotted lines and intramolecular hydrogen bonds shown as green dotted lines.
was separated and concentrated (petroleum ether:ethyl acetate 7:1, 0.70) and the fraction containing the product (75%) was collected and used for the next step. A solution of compound 3 (0.4 mol, 1 eq) in tetrahydrofurane was stirred and cooled in an ice bath, tetra-n-butylammonium fluoride (1.5 eq) was added and the reaction was stirred for two hours. The organic layer was separated and dried over magnesium sulfate to obtain compound 4 (petroleum ether:ethyl acetate 7:1, 0.60). The title compound (I) (Fig. 3) was prepared by refluxing a mixture of quinaldic acid, triethylamine, ptoluenesulfonyl chloride and compound 4 for 24 h in dichloromethane. After evaporation of the CH 2 Cl 2 , the compound was purified by silica column chromatography (petroleum ether:ethyl acetate 7:1, 0.36). Single colourless block-shaped crystals of (I) were obtained by slow evaporation in dichloromethane in a closed flask with petroleum ether.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All non-hydrogen atoms were refined anisotropically. Hydrogen-atom positions were calculated geometrically and refined using the riding model: N-H = 0.86 Å and C-H = 0.93 Å with U iso (H) = 1.2U eq (C,N).  The reaction scheme for the synthesis of the title compound.   OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

N-(2-Benzoyl-5-ethynylphenyl)quinoline-2-carboxamide
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.