Diethyl 4-[4-(dimethylamino)phenyl]-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C21H28N2O4, the dihydropyridine ring adopts a flattened boat conformation. The mean plane of the dihydropyridine ring and the attached benzene ring form a dihedral angle of 85.1 (1) Å. One of two ethyl fragments is disordered between two conformations in a 0.67 (4):0.33 (4) ratio. In the crystal structure, molecules related by translation along the a axis are linked into chains via intermolecular N—H⋯O hydrogen bonds.

In the title compound, C 21 H 28 N 2 O 4 , the dihydropyridine ring adopts a flattened boat conformation. The mean plane of the dihydropyridine ring and the attached benzene ring form a dihedral angle of 85.1 (1) Å . One of two ethyl fragments is disordered between two conformations in a 0.67 (4):0.33 (4) ratio. In the crystal structure, molecules related by translation along the a axis are linked into chains via intermolecular N-HÁ Á ÁO hydrogen bonds.

Related literature
For the pharmacological activity of compounds containing substituted 1,4-dihydropyridine ring systems, see: Triggle et al.(1980);Henry (2004). For a related structure, see Sun et al. (2006).  Table 1 Hydrogen-bond geometry (Å , ).  (Triggle et al., 1980). In addition, several of these compounds were discovered to be highly selective ligands for adenosine receptors, which were recently recognized as potential targets for the development of new drugs for the treatment of Parkinson's disease, hypoxia/ischemia, asthma, kidney disease, epilepsy, and cancer (Henry et al., 2004). In continuation of our ongoing program directed to the development of pyridine chemistry, we present here the crystal structure of the title compound, (I).

Refinement
All H atoms were placed in geometrically idealized positions ( C-H of methyl distances is 0.96 Å , C-H of methylene distances is 0.97 Å , C-H of methine distances is 0.98 Å and aromatic C-H distances is 0.93 Å, N-H distances is 0.86 Å) and treated as riding on their parent atoms, with U iso (H) = 1.2 U-1.5 eq (C, N) . Atoms C 8 , C 9 were treated as disordered between two positions, with refined occupancies of 0.33 (4) and 0.67 (4). Fig. 1. A view of (I) showing the atomic numbering scheme and 30% probability displacement ellipsoids. Only major parts of disordered atoms are shown. H atoms omitted for clarity.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (