Ethyl 8-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylate

In the title compound, C13H13NO4, the asymmetric unit contains four independent molecules, each exhibiting an intramolecular N—H⋯O hydrogen bond. The ethyl group in one of the four molecules is disordered, with a refined occupancy ratio of 0.295 (16):0.705 (16). A face-to-face stacking interaction is found between the benzene rings of the quinoline units of two of the molecules [centroid–centroid distance = 3.541 (2) Å], which are sandwiched by the other two molecules through N—H⋯O hydrogen bonding. In the crystal, the sandwiched molecules are assembled via stacking interactions along the b-axis direction with their translation-symmetry equivalents [centroid–centroid distance = 3.529 (2) Å], and are further linked through N—H⋯O hydrogen bonding. The other two molecules are linked via stacking interactions with their inversion-symmetry equivalents [centroid–centroid distances = 3.512 (3) and 3.716 (4) Å] and via N—H⋯O hydrogen bonding.

In the title compound, C 13 H 13 NO 4 , the asymmetric unit contains four independent molecules, each exhibiting an intramolecular N-HÁ Á ÁO hydrogen bond. The ethyl group in one of the four molecules is disordered, with a refined occupancy ratio of 0.295 (16):0.705 (16). A face-to-face stacking interaction is found between the benzene rings of the quinoline units of two of the molecules [centroid-centroid distance = 3.541 (2) Å ], which are sandwiched by the other two molecules through N-HÁ Á ÁO hydrogen bonding. In the crystal, the sandwiched molecules are assembled via stacking interactions along the b-axis direction with their translationsymmetry equivalents [centroid-centroid distance = 3.529 (2) Å ], and are further linked through N-HÁ Á ÁO hydrogen bonding. The other two molecules are linked via stacking interactions with their inversion-symmetry equivalents [centroid-centroid distances = 3.512 (3) and 3.716 (4) Å ] and via N-HÁ Á ÁO hydrogen bonding.

Related literature
For the background of this study, see: Ishikawa & Fujii (2011). For the synthesis of the title compound, see: Ozeki et al.  Table 1 Hydrogen-bond geometry (Å , ). In the crystal, the sandwiched molecules are assembled via stacking interaction along the b-axis direction with the translation-symmetry equivalents i,ii [centroid-centroid distances between the benzene rings of the quinoline units = 3.529 (2) Å, i: x, y + 1, z, ii: x, y-1, z], and are further linked with the glide-reflection-symmetry equivalents through N-H···O hydrogen bonding. The other two molecules are also linked with the inversion-symmetry equivalents iii,iv via stacking interactions [centroid-centroid distances between the benzene rings of the quinoline units = 3.512 (3) and 3.716 (4) Å, iii: -x + 1, -y + 1, -z, iv: -x + 2, -y-1, -z + 1], and with the glide-reflection-symmetry equivalents via N-H···O hydrogen bonding, as shown in Fig.2. A l l 1,3-diketones and secondary amines of the molecules are involved in the intermolecular hydrogen bonding, which leads to a higher order network.

Experimental
The title compound was synthesized according to the literature (Ozeki et al. 1987). Single crystals suitable for X-ray diffraction were obtained by slow evaporation of an acetonitrile solution of the compound at room temperature.

Refinement
The  The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level.
Special details Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F 2 . R-factor (gt) are based on F. The threshold expression of F 2 > 2.0 σ(F 2 ) is used only for calculating R-factor (gt).