Diethyl 2,6-dimethyl-4-[5-(4-methylphenyl)-1H-pyrazol-4-yl]-1,4-dihydropyridine-3,5-dicarboxylate

In the title compound, C23H27N3O4, the dihydropyridine ring adopts a 1,4 B conformation. Intramolecular C—H⋯O contacts occur. In the crystal, N—H⋯O and N—H⋯N hydrogen bonds and C—H⋯N contacts connect the molecules into strands along the a-axis direction.

In the title compound, C 23 H 27 N 3 O 4 , the dihydropyridine ring adopts a 1,4 B conformation. Intramolecular C-HÁ Á ÁO contacts occur. In the crystal, N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds and C-HÁ Á ÁN contacts connect the molecules into strands along the a-axis direction.
Motivated by the promising pharmaceutical activities of 1,4-dihydropyridines, the title compound was synthesized to study its crystal structure.
The molecule is a pyrazole derivative featuring a phenyl as well as a dihydropyridine-derived substituent. While the small puckering amplitude precludes a conformational analysis of the five-membered heterocycle, the dihyropyridine ring adopts a 1,4 B ( N11,C11 B) conformation (Cremer & Pople, 1975;Boeyens, 1978). The least-squares planes defined by the intracyclic atoms of the phenyl group as well as the five-membered heterocycle, respectively, enclose an angle of 33.03 (7) °. The plane defined by the atoms of the dihydropyridine core is almost planar (r.m.s. of all fitted atoms = 0.1726 Å), with the flap carbon atom and the nitrogen atom deviating most from the plane by 0.270 (1) Å and 0.199 (1) Å, respectively ( Fig. 1).
In the crystal, classical intermolecular hydrogen bonds of the N-H···N as well as the N-H···O type are present.
Furthermore, C-H···N contacts and C-H···O contacts whose range falls by more than 0.1 Å below the sum of van-der-Waals radii of the corresponding atoms are observed. The C-H···N contacts are supported by one of the hydrogen atoms of a methyl group directly bonded to the dihydropyridine ring and one of the nitrogen atoms of the pyrazole moiety. The intramolecular C-H···O contact is apparent between one of the hydrogen atoms of the phenyl group in ortho position to the pyrazole ring and one of the sp 2 hybridized oxygen atoms. Metrical parameters as well as information about the symmetry of these contacts are summarized in Table 1. In total, the C-H···N contacts as well as the N-H···O-type hydrogen bonds form antidromic chains of molecules that are extended to strands along the crystallographic a axis by the N-H···N-type hydrogen bonds. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for the classical hydrogen bonds is C 1 1 (8)R 2 2 (16) on the unary level. The C-H supported contacts necessitate a S(9)C 1 1 (8) descriptor on the same level. The shortest intercentroid distance between two aromatic systems was measured at 4.7738 (8) Å (Fig. 2).
The packing of the title compound in the crystal structure is shown in Figure 3.

Refinement
Carbon-bound H atoms were placed in calculated positions (C-H 0.95 Å for aromatic carbon atoms, C-H 0.99 Å for methylene groups and C-H 1.00 Å for the methine group) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C). The H atoms of the methyl groups were allowed to rotate with a fixed angle around the C-C bond to best fit the experimental electron density (HFIX 137 in the SHELX program suite (Sheldrick, 2008), with U(H) set to 1.5U eq (C). Both nitrogen-bound H atoms were located on a difference Fourier map and refined freely.