1-[5-Acetyl-2,6-dimethyl-4-(5-phenyl-1H-pyrazol-3-yl)-1,4-dihydropyridin-3-yl]ethanone monohydrate

In the title compound, C20H21N3O2·H2O, the aza-substitued six-membered ring adopts a L4 B conformation. In the crystal, classical N—H⋯O, N—H⋯N and O—H⋯O hydrogen bonds connect the entities into a three-dimensional network. Intramolecular C—H⋯O contacts are also observed.

The molecule features a pyrazole core bearing a phenyl as well as a 1,4-dihydropyridine-derived substituent. The sixmembered ring of the latter adopts a L4 B conformation according to a puckering analysis (Cremer & Pople, 1975). The least-squares planes defined by the respective intracyclic atoms of the phenyl group as well as the 1,4-dihydropyridine core enclose angles of 52.79 (8) ° and 88.10 (7) ° with the least-squares plane defined by the non-hydrogen atoms of the central pyrazole core (Fig. 1).
In the crystal, classical hydrogen bonds of the O-H···O, N-H···O and N-H···N type are apparent involving both ketonic oxygen atoms and the non-protonated nitrogen atom as acceptors. In addition, two intramolecular C-H···O contacts can be observed whose range falls by more than 0.2 Å below the sum of van-der-Waals radii of the atoms participating. The latter stem from a hydrogen atom on the phenyl group as well as the methine group and have the same ketonic oxygen atom as acceptor. In total, the entities of the title compound are connected to a three-dimensional network in the crystal structure. In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor for these contacts is S(5)S(9)DDDC 1 1 (8) on the unary level. Metrical parameters as well as information about the symmetry of these contacts are summarized in Table 1. The shortest intercentroid distance between two aromatic systems was measured at 4.7199 (10) Å and is apparent between the pyrazol and the phenyl moiety in neighbouring molecules (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 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).
All nitrogen-and oxygen-bound H atoms were located on a difference Fourier map and refined freely.