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

The asymmetric unit of the title compound, C13H10F3NO3, contains two independent molecules with similar conformations. In the crystal, N—H⋯O hydrogen bonds link alternating independent molecules into chains in [-110]. In the chain, the quinoline planes of the independent molecules are almost perpendicular to each other, forming a dihedral angle of 89.8 (1)°. π–π interactions between the aromatic rings of quinoline bicycles related by inversion centres [for two independent centrosymmetric dimers, the shortest centroid–centroid distances are 3.495 (1) and 3.603 (1) Å] link the hydrogen-bonded chains into layers parallel to (110). Weak C—H⋯F and C—H⋯O interactions further consolidate the crystal packing.

The title compound is a derivative of 1,4-dihydroquinoline and does not adopt its aromatic tautomeric form as a quinoline derivative. There are two independent molecules in the asymmetric unit ( Fig. 1).
In the crystal, classical N-H···O hydrogen bonds (Table 1) link the alternating independent molecules into chains in [-110] (Fig. 2). In the chain, the quinoline planes of independent molecules are almost perpendicular to each other forming a dihedral angle of 89.8 (1)°. The π-π interactions between the aromatic rings of the quinoline bicycles related by inversion centres [for two independent centrosymmetric dimers the shortest intercentroid distances are 3.495 (1) and 3.603 (1) Å, respectively] link hydrogen-bonded chains into layers parallel to the (110) plane. Weak intermolecular C-H···F contacts are observed next to intermolecular C-H···O contacts (Table 1). In every case, the range of these contacts falls by more than 0.1 Å below the sum of van-der-Waals radii of the atoms participating in them. While the C-H···O contacts stem from one of the hydrogen atoms on the phenyl moiety bearing the trifluoromethyl substituent and apply the ethereal oxygen atom as acceptor, the classical hydrogen bonds invariably have double bonded oxygen atoms as acceptors. These hydrogen bonds intermittently connect the two different molecules present in the asymmetric unit into chains along [-110] and show bifurcation between the two double bonded oxygen atoms in one case. In total, these contacts connect the molecules to planes parallel to ab. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for the classical hydrogen bonds is DDD on the unary level (taking into account the bifurcation).
The descriptor for the C-H···O contacts is D while a C 1 1 (11) descriptor is found for the C-H···F contacts on the same level.

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Acta Cryst. (2012). E68, o3304-o3305 Refinement C-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic and vinylic carbon atoms and C-H 0.99 Å for methylene groups) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C). The H atoms of the methyl groups were allowed to rotate with a fixed angle around the C-C bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite (Sheldrick, 2008)), with U(H) set to 1.5U eq (C).
Both nitrogen-bound H atoms were located on a difference Fourier map and refined freely.