(RS)-3-Acetyl-2-methyl-4-(3-nitrophenyl)-1,4,5,6,7,8-hexahydroquinolin-5-one

In the title compound, C18H18N2O4, the nitro group, a methyl group, the acetyl group and some atoms of the dihydroquinolinone group are disordered over two sites with the ratio of occupancies fixed at 0.57:0.43. The relationship between the major and minor components of disorder is that of diastereomers. In the crystal structure, intermolecular N—H⋯O, weak C—H⋯O and C—H⋯π interactions link the molecules into two-dimensional layers running parallel to the (010) plane.

In the title compound, C 18 H 18 N 2 O 4 , the nitro group, a methyl group, the acetyl group and some atoms of the dihydroquinolinone group are disordered over two sites with the ratio of occupancies fixed at 0.57:0.43. The relationship between the major and minor components of disorder is that of diastereomers. In the crystal structure, intermolecular N-HÁ Á ÁO, weak C-HÁ Á ÁO and C-HÁ Á Á interactions link the molecules into two-dimensional layers running parallel to the (010) plane.

Experimental
The title compound was synthesized according to a literature procedure (Ko & Yao, 2006). The product was recrystallized from ethyl acetate at room temperature to give block red crystals suitable for single-crystal X-ray diffraction.

Refinement
In the refinement, the nitro group, C18 methyl group, acetyl group and some atoms of the dihydroquinolinone group (C9-C12/C16-C18/O3/O4) were modelled as disordered over two sites with the final site occupancies fixed at 0.57:0.43. Commands SADI and DFIX were used in the refinement to restrain some bond lengths. The relationship between the major and minor components of disorder is that of diastereomers.

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.
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 > 2sigma(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.