1-Benzyl-3-methylquinoxalin-2 ( 1 H )-one

Laboratoire de Chimie Hétérocyclique, Pole de Compétence PHARCHIM, Université Mohammed V-Agdal, BP 1014, Rabat, Morocco, Laboratoires de Diffraction des Rayons X, Division UATRS, Centre National pour la Recherche Scientifique et Technique, Rabat, Morocco, and Laboratoire de Biochimie, Environnement et Agroalimentaire (URAC 36), Faculté des Sciences et Techniques Mohammedia, Université Hassan II Mohammedia-Casablana, BP 146, 20800 Mohammedia, Morocco Correspondence e-mail: yramli76@yahoo.fr

The asymmetric unit of the title compound, C 16 H 14 N 2 O, contains three independent molecules. The dihedral angles between the quinoxaline and phenyl planes in the three molecules are 82.58 (8), 85.66 (9) and 85.36 (9) . The crystal packing is stabilized by C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds.
The asymmetric unit of the title compound contains three independent molecules (Fig. 1). The dihedral angles between the quinoxaline and phenyl planes in the three molecules are 82.58 (8), 85.66 (9) and 85.36 (9)°. The crystal structure is devoid of classical hydrogen bonds. However, the crystal packing is stabilized by C-H···O and C-H···N hydrogen bonds (Tab. 1 & Fig. 2).

S2. Experimental
To a solution of 3-methylquinoxali-2(1H)-one (1 g) in 20 ml of dimethylformamide were added benzylchloride (0.72 ml), K 2 CO 3 (0.90 g) and catalytic amont of tetrabutylammonium bromide. The mixture was stirred at room temperature for 24 h. The solvent was removed under reduce pressure and the residue was crystallized in ethanol to afford the crystals of the title compound which were suitable for X-ray analysis.

S3. Refinement
All H atoms were fixed geometrically and treated as riding with C-H = 0.96 Å (methyl), 0.98Å methine or 0.93 Å (aromatic) with Uĩso(H) = 1.2Ueq(C) or 1.5Ueq(methyl). The H-atoms of the methyl groups C21 and C31 were disordered over six sites each with 0.5 site occupancy factors. A search for solvent-accessible voids in the crystal structure using PLATON (Spek, 2009) showed solvent accessible voids of 110 Å 3 . However, the refinement showed no electron density in the voids. This indicates that the crystal lost the solvent of crystallization by the time it was used for data collection, without collapse of the crystal lattice.  Molecular structure of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radii.

Figure 2
Crystal packing of the title compound viewed down the c-axis; H-atoms not involved in H-bonds have been omitted for clarity.

1-Benzyl-3-methylquinoxalin-2(1H)-one
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.30 e Å −3 Δρ min = −0.24 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0084 (16) Special details Experimental. The data collection nominally covered a sphere of reciprocal space, by a combination of four sets of exposures; each set had a different φ angle for the crystal and each exposure covered 0.5° in ω and 30 s in time. The crystal-to-detector distance was 37.5 mm. 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.