1,1′-[4-(4-Methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-diyl]diethanone

In the title compound, C18H21NO3, which belongs to the family of calcium channel blockers, the dihydropyridine ring assumes a flattened boat conformation. The two carbonyl units adopt a synperiplanar conformation with respect to the double bonds in the dihydropyridine ring. The methoxyphenyl ring is almost perpendicular to the prydine ring [dihedral angle = 89.01 (7)°]. In the crystal, the molecules are connected by intermolecular N—H⋯O hydrogen bonds.

In the title compound, C 18 H 21 NO 3 , which belongs to the family of calcium channel blockers, the dihydropyridine ring assumes a flattened boat conformation. The two carbonyl units adopt a synperiplanar conformation with respect to the double bonds in the dihydropyridine ring. The methoxyphenyl ring is almost perpendicular to the prydine ring [dihedral angle = 89.01 (7) ]. In the crystal, the molecules are connected by intermolecular N-HÁ Á ÁO hydrogen bonds.

Experimental
Dimethyl-4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate was prepared by heating the mixture of 4-methoxybenzaldehyde (10 mmol), methylacetoacetate (20 mmol) and ammonium acetate (10 mmol) at 80 o C for 2 hours and 45 min (monitored by TLC). After completion of the reaction, the mixture was cooled to room temperature and kept for 3 days to get the solid product. The obtained solid was washed with diethyl ether and collected separately. The purity of the crude product was checked through TLC and recrystallized using acetone and ether.

Refinement
H atoms were positioned geometrically (C-H = 0.93-0.98Å) and allowed to ride on their parent atoms, with Uiso(H) = 1.5Ueq(C) for methyl H and 1.2Ueq(C) for other H atoms.The components of the anisotropic displacement parameters of C5 and C6 in the direction of the bond between them were restrained to be equal within an effective standard deviation of 0.001.

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.