Ethyl 1,6-dimethyl-2-oxo-4-(quinolin-4-yl)-1,2,3,4-tetrahydropyrimidine-5-carboxylate

In the title compound, C18H19N3O3, the tetrahydropyrimidone ring adopts a distorted boat conformation. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link the molecules into centrosymmetric dimers, which are further linked via intermolecular C—H⋯π interactions. In addition, an intramolecular C—H⋯O hydrogen bond occurs.

In the title compound, C 18 H 19 N 3 O 3 , the tetrahydropyrimidone ring adopts a distorted boat conformation. In the crystal structure, intermolecular N-HÁ Á ÁO hydrogen bonds link the molecules into centrosymmetric dimers, which are further linked via intermolecular C-HÁ Á Á interactions. In addition, an intramolecular C-HÁ Á ÁO hydrogen bond occurs.

Experimental
The title compound was synthesized by refluxing condition of monomethylurea (0.237 g, 3.20 mmol), 4-quinoline aldehyde (0.502 g, 3.20 mmol), acetoacetic ester (0.520 g, 4.00 mmol) with catalytic amount of HCl in 15 ml EtOH. The residue was purified by column chromatography (silica gel, hexane-acetone, 90:5 v/v) to afforded the title compound as a colorless solid (yield 48%, m.p. 472 K). The single crystals suitable for X-ray diffraction were obtained by evaporation of a solution of the title compound in acetone.
supplementary materials sup-2 Refinement All H-atoms were positioned geometrically and refined using a riding model with d (N-H) = 0.86 Å, d (C-H) = 0.93-0.98 Å and U iso (H) = 1.2-1.5 U eq (parent atom). Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids drawn at the 50% probability level. H atoms are presented as a small spheres of arbitrary radius.

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 > σ(F 2 ) is used only for calculating Rfactors(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.