2-Methyl-3-(2-methylphenyl)-7-nitroquinazolin-4(3H)-one

In the title methaqualone analogue, C16H13N3O3, the 2-tolyl group is almost orthogonal [dihedral angle = 85.20 (5)°] to the fused ring system (r.m.s. deviation of fitted non-H atoms = 0.029 Å). In the crystal, twofold symmetry generates two-molecule aggregates linked by C—H⋯O and π–π interactions [ring centroid–centroid distance = 3.4967 (6) Å].


Experimental
The main feature of the crystal packing is the formation of two molecule aggregates sustained by C-H···O, Table 1, and π-π interactions, Fig. 2. The π-π interactions occur between (C1-C6) rings, i.e. the C 6 group within the fused ring system, with a ring centroid-to-centroid distance of 3.4967 (6) Å [symmetry operation: 1 -x, y, 1/2 -z]. There are no specific intermolecular interactions between the two-molecule aggregates [generated by 2-fold symmetry]. They assemble into layers in the bc plane, Fig. 3, and these stack along the a axis, Fig. 4.

Experimental
4-Nitroanthranilic acid (1.82 g, 10 mmol) was refluxed with acetic anhydride (20 ml) for 3 h. The reaction mixture was cooled, filtered, washed with petroleum ether, and dried to yield 2-methyl-7-nitro-4H-3,1-benzoxazin-4-one as an a solid compound. This was refluxed with o-toludine (1.18 g, 11 mmol) in pyridine (30 ml) for 8 h. The reaction mixture was cooled, the solvent was removed under reduced pressure and the residue was triturated with water and filtered. The solid obtained was dried, chromatographed with CHCl 3 and recrystallized from its EtOH solution as colourless cubes.

Refinement
Carbon-bound H-atoms were placed in calculated positions [C-H = 0.95 to 0.98 Å, U iso (H) = 1.2 to 1.5U eq (C)] and were included in the refinement in the riding model approximation.  The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.

Figure 2
A view of the two-molecular aggregate in (I) sustained by C-H···O and π-π interactions shown as orange and purple dashed lines, respectively.  A view of the assembly of two-molecule aggregates in the bc plane in (I). The C-H···O and π-π interactions are shown as orange and purple dashed lines, respectively.

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.