Ethyl 2-[(2-hydroxybenzylidene)amino]-6-methyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate

The title compound, C18H20N2O3S, exists as the phenol–imine form in the crystal and there are bifurcated intramolecular O—H⋯(N/O) hydrogen bonds present. The conformation about the C=N bond is anti (1E); the C=N imine bond length is 1.287 (4) Å and the C=N—C angle is 122.5 (3)°. In the tetrahydrothienopyridine moiety, the six-membered ring has a flattened-boat conformation. In the crystal, molecules are stacked nearly parallel to (110) and a weak C—H⋯π interaction is observed. The carbonyl O atom is disordered over two positions and was refined with a fixed occupancy ratio of 0.7:0.3.

The title compound, C 18 H 20 N 2 O 3 S, exists as the phenol-imine form in the crystal and there are bifurcated intramolecular O-HÁ Á Á(N/O) hydrogen bonds present. The conformation about the C N bond is anti (1E); the C N imine bond length is 1.287 (4) Å and the C N-C angle is 122.5 (3) . In the tetrahydrothienopyridine moiety, the six-membered ring has a flattened-boat conformation. In the crystal, molecules are stacked nearly parallel to (110) and a weak C-HÁ Á Á interaction is observed. The carbonyl O atom is disordered over two positions and was refined with a fixed occupancy ratio of 0.7:0.3.

D-HÁ
The molecule of the title compound is in the phenol-imine form ( In the crystal, molecules are stacked nearly parallel to (110) and a weak C-H···π interaction is observed (Table 1 and
The precipitated solid was collected, washed with cold ethanol and recrystallized from ethanol giving orange block-like crystals.

Refinement
Atoms H1 (for OH) and H7 (for methine) were located in a difference Fourier map and refined freely. The C-bound H atoms were positioned geometrically with C-H = 0.93, 0.96 and 0.97 Å for aromatic, methyl and methylene H atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = k × U eq (C), where k = 1.5 for methyl H-atoms and k = 1.2 for other H-atoms. During the refinement process the disordered O2A and O2B atoms were refined with a fixed occupancy ratio of 0.70:0.30.

Figure 1
The molecular structure of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are shown as dashed lines -see Table 1 for details.    where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.16 e Å −3 Δρ min = −0.16 e Å −3 Absolute structure: Flack (1983), 691 Friedel pairs Flack parameter: 0.08 (11) 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.