Diethyl 4-(4-ethoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C21H27NO5, the dihydropyridine ring adopts a boat conformation. The ethoxyphenyl ring is oriented approximately perpendicular to the planar part of the dihydropyridine ring, making a dihedral angle of 89.45 (6)°. An intramolecular C—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal structure, neighbouring molecules are linked into chains along the a axis by N—H⋯O hydrogen bonds and the chains are interconnected into two-dimensional networks parallel to the ab plane by C—H⋯O hydrogen bonds. The structure is further stabilized by weak C—H⋯π interactions.


Experimental
The title compound was prepared according to Hantzsch pyridine synthesis. A mixture of 4-ethoxybenzaldehyde (10 mmol), ethylacetoacetate (20 mmol) and ammonium acetate (10 mmol) were heated at 353 K for 3 h (monitored by TLC). After completion of the reaction, the mixture was cooled to room temperature and kept for 2 days to get the solid product. The solid formed was washed using diethyl ether. After washing, the solid and the liquid was collected separately and the liquid was kept for solidification. The purity of the crude product was checked through TLC and recrystallized using acetone and ether (m.p. 377-379 K).

Refinement
Atom H1N1 was located from a difference Fourier map and allowed to refine freely. The other H-atoms were placed in calculated positions, with C-H = 0.93 Å, and U iso = 1.2U eq (C) for aromatic, and C-H = 0.96 Å and U iso = 1.5U eq (C) for methyl group. A rotating group model was used for the methyl group. Diethyl 4-(4-ethoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
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.