N-(2,5-Dimethoxyphenyl)-6-nitroquinazolin-4-amine

In the title molecule, C16H14N4O4, the quinazoline ring is substantially planar (r.m.s. deviation = 0.0129 Å) and forms a dihedral angle of 2.73 (8)° with the benzene ring. The conformation of the molecule is stabilized by an intramolecular C—H⋯N hydrogen bond. In the crystal, molecules are linked into chains running parallel to the b axis by C—H⋯O hydrogen bonds. In addition, π–π stacking is observed between dimethoxy-substituted and nitro-substituted benzene rings, with centroid–centroid distances in the range 3.6438 (10)–3.7148 (10) Å.

In the title molecule, C 16 H 14 N 4 O 4 , the quinazoline ring is substantially planar (r.m.s. deviation = 0.0129 Å ) and forms a dihedral angle of 2.73 (8) with the benzene ring. The conformation of the molecule is stabilized by an intramolecular C-HÁ Á ÁN hydrogen bond. In the crystal, molecules are linked into chains running parallel to the b axis by C-HÁ Á ÁO hydrogen bonds. In addition,stacking is observed between dimethoxy-substituted and nitro-substituted benzene rings, with centroid-centroid distances in the range 3.6438 (10)-3.7148 (10) Å .

Experimental
A mixture of (E)-N′-(2-cyano-4-nitrophenyl)-N,N-dimethylformimidamide (0.436 g, 2 mmol) and 2,5-dimethoxyaniline (0.35 g, 2 mmol) was refluxed in acetic acid (12 ml) at 75 °C for 2 h. Progress of the reaction was monitored by thin layer chromatography. After completion of the reaction, the mixture was cooled to room temperature and neutralized by adding a saturated aqueous solution of sodium bicarbonate until the evolution of CO 2 gas ceased. The reaction mixture yielded brown crystals on standing at room temperature, which were filtered and washed with water. The crystals were re-grown using ethanol and collected in 50.2% yield (0.3273 g). All chemicals were purchased by sigma Aldrich Germany.

Refinement
H atoms on aromatic rings and methyl carbons were positioned geomatrically with 0.93-0.96 Å and constrained to ride on their parent atoms with U iso (H) = 1.2 U eq (C) or 1.5 U eq (C) for methyl H atoms. The H atoms of the nitrogen atom (N-H = 0.868 (19) Å) was located in a difference Fourier map and refined isotropically. A rotating group model was applied to the methyl groups.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level. An intramolecular hydrogen bond is shown as a dashed line.  The crystal packing of the title compound. Only hydrogen atoms involved in hydrogen bonding (dashed lines) are shown.

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.