2-(4-Chlorophenyl)-2,3-dihydroquinolin-4(1H)-one

The title molecule, C15H12ClNO, features a dihydroquinolin-4(1H)-one moiety attached to a chlorobenzene ring. The heterocyclic ring has a half-chair conformation with the methine C atom lying 0.574 (3) Å above the plane of the five remaining atoms (r.m.s. deviation = 0.0240 Å). The dihedral angles between the terminal benzene rings is 77.53 (9)°, indicating a significant twist in the molecule. In the crystal, supramolecular zigzag chains along the c-axis direction are sustained by N—H⋯O hydrogen bonds. These are connected into double chains by C—H⋯π interactions.

The title molecule, C 15 H 12 ClNO, features a dihydroquinolin-4(1H)-one moiety attached to a chlorobenzene ring. The heterocyclic ring has a half-chair conformation with the methine C atom lying 0.574 (3) Å above the plane of the five remaining atoms (r.m.s. deviation = 0.0240 Å ). The dihedral angles between the terminal benzene rings is 77.53 (9) , indicating a significant twist in the molecule. In the crystal, supramolecular zigzag chains along the c-axis direction are sustained by N-HÁ Á ÁO hydrogen bonds. These are connected into double chains by C-HÁ Á Á interactions.
Thanks are due to MESRS (Ministé re de l'Enseignement Supé rieur et de la Recherche Scientifique -Algeria) for financial support. We are grateful to Dr Roisnel Thierry from the Centre de difractomé trie de Rennes, Université de Rennes 1, France, for his technical assistance with the data collection.
Supporting information for this paper is available from the IUCr electronic archives (Reference: TK5289).

Synthesis and crystallization
The corresponding 2′-aminochalcone (0.5 mmol) and [bmim]BF 4 (1 g) were heating at 150 °C for 2.5 h; bmim is butylmethylimidazolium. The crude product was isolated by repeated extraction with diethyl ether (7×10 ml). Filtration of the residue through a silica plug gave the 2-(4-chlorophenyl)-2,3-dihydroquinolin-4(1H)-one (I). Single crystals suitable for the X-ray diffraction analysis were obtained by dissolving the pure compound in an Et 2 O/CHCl 3 mixture and allowing the solution to slowly evaporate at room temperature.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.93-0.98 Å) and refined as riding with U iso (H) = 1.2U eq (C).
The H1N atom was refined with U iso (H) = 1.2U eq (N). Owing to poor agreement, the (1 1 0) reflection was omitted from the final cycles of refinement.

Results and discussion
2-Arylquinolo-4-ones are nitrogen-containing analogues flavanones and flavones, and are characterized by a benzo ring fused to six-membered nitrogen containing heterocyclic ring with an aryl substituent at position 2. The quinolone heterocyclic ring has many reactive sites for possible transformation and can also result in different degree of unsaturation (Diesbach & Kramer, 1945;Prakash et al., 1994;Singh & Kapil, 1993;Kalinin et al., 1992). To date, numerous accounts have been reported in the literature for the synthesis of quinolone, due to their frequent occurrence in biologically interesting molecules. RTILs have proven to be viable reaction media for numerous types of reaction, including, for example, Friedel-Crafts alkylations, Diels-Alder, Knoevenagel, 1,3-dipolar cycloadditions, and in three component coupling reactions (Chauvin & Olivier, 1996). As a part of our program directed toward the synthesis of new suitably functionalized heterocyclic compounds of potential biological activity (Bouraiou et al., 2008Benzerka et al., 2011) and following our successes in the area of ionic liquid catalyzed 2-aminochalones isomerization into the corresponding 2-phenyl-2,3-dihydroquinolin-4(1H)-one (Chelghoum et al., 2012), we envisioned to get some information on the spatial arrangements of this type of compounds. We report herein the synthesis and single-crystal X-ray structure of 2-(4-chlorophenyl)-2,3-dihydroquinolin-4(1H)-one (I). The molecular geometry and the atom-numbering scheme of (I) are shown in Fig. 1 and features a dihydroquinolin-4(1H)-one moiety attached to a chlorobenzene group. The crystal packing can be described as alternating double layers parallel to the (100) along the a axis (Fig. 2). It is stabilized by N-H···O hydrogen bonding and C-H···π interactions ( Fig. 3; Table 1).  The molecular geometry of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radius.

Figure 2
Alternating double layers parallel to (100) in (I), viewed down the c axis.

Figure 3
A diagram of the layered crystal packing of (I), viewed down the b axis showing hydrogen bonds as dashed lines. 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.