Diethyl 2,6-dimethyl-4-phenyl-1,4-dihydropyridine-3,5-dicarboxylate

The title molecule, C19H23NO4, was synthesized by the reaction of benzaldehyde, ethyl acetoacetate and NH4HCO3. The dihydropyridine ring adopts a flattened boat conformation and the plane of the base of the boat forms a dihedral angle of 88.78 (9)° with the phenyl ring. The packing is stabilized by strong intermolecular N—H⋯O and weak intermolecular C—H⋯O hydrogen bonds.

The title molecule, C 19 H 23 NO 4 , was synthesized by the reaction of benzaldehyde, ethyl acetoacetate and NH 4 HCO 3 . The dihydropyridine ring adopts a flattened boat conformation and the plane of the base of the boat forms a dihedral angle of 88.78 (9) with the phenyl ring. The packing is stabilized by strong intermolecular N-HÁ Á ÁO and weak intermolecular C-HÁ Á ÁO hydrogen bonds.

Comment
The development of new methods for the synthesis of substituted pyridines is a motive for the current study. Substituted pyridines attract the interest because of their presence in numerous natural products along with a wide spectrum of their physiological activities (Cutshall et al., 2002). Pyridine derivatives and their complexes have been studied for their fungicidal and antibacterial effects, as well as antiviral drugs (Henry, 2004).
In the crystal structure, the dihydropyridine ring adopts a flattened boat conformation and the plane of the base of the boat (C1/C2/C4/C5) contains 88.78 (9)° with the phenyl ring. There are present strong (Desiraju & Steiner, 1999) intermolecular N-H···O hydrogen bonds (Tab. 1) that link the molecules into chains propagated in the direction [010].

Experimental
Fresh benzaldehyde (6 mmol), ethyl acetoacetate (6 mmol) and NH 4 HCO 3 (6 mmol) were mixed in a 50 ml flask. After the mixture had been stirred for 3 h at 293 K, the crude product was obtained. The title crystals were obtained by recrystallization from ethanol, affording the title compound as a yellow block crystalline solid. Elemental analysis: calculated for C 19 H 23 NO 4 : C 69.28, H 7.04, N 4.25 weight%; found: C 69.29, H 7.85, N 4.29 weight%.

Refinement
All the hydrogens were discernible in the difference electron density map. Except for the secondary-amine H atom whose coordinates were refined freely the remaining hydrogens were situated into the idealized positions and were refined within a riding model approximation: C methyl -H = 0.96, C methylene -H 0.97, C methine = 0.98 Å. U iso (H) = 1.2 U eq C methylene / C methine /N secondary-amine ; U iso (H) = 1.5 U eq (C methyl ). The methyl groups were allowed to rotate during the refinement.

Special details
Experimental. The sample was cut out from a larger slab crystal.
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.