2-Amino-6-(piperidin-1-yl)-4-p-tolylpyridine-3,5-dicarbonitrile

In the title compound, C19H19N5, the piperidine ring adopts a chair conformation. The pyridine ring is essentially planar, with a maximum deviation of 0.039 (2) Å for a C atom substituted with a carbonitrile group. The mean plane of the central pyridine ring makes the dihedral angles of 37.90 (14) and 56.10 (12)° with the piperidine and benzene rings, respectively. In the crystal, molecules are linked via N—H⋯N and C—H⋯N hydrogen bonds, forming chains along [101], and enclosing R 2 2(17) ring motifs. The chains are linked by further C—H⋯N hydrogen bonds, forming two-dimensional networks lying parallel to (10-1), and enclosing inversion dimers with R 2 2(20) ring motifs.

In the title compound, C 19 H 19 N 5 , the piperidine ring adopts a chair conformation. The pyridine ring is essentially planar, with a maximum deviation of 0.039 (2) Å for a C atom substituted with a carbonitrile group. The mean plane of the central pyridine ring makes the dihedral angles of 37.90 (14) and 56.10 (12) with the piperidine and benzene rings, respectively. In the crystal, molecules are linked via N-HÁ Á ÁN and C-HÁ Á ÁN hydrogen bonds, forming chains along [101], and enclosing R 2 2 (17) ring motifs. The chains are linked by further C-HÁ Á ÁN hydrogen bonds, forming two-dimensional networks lying parallel to (101), and enclosing inversion dimers with R 2 2 (20) ring motifs.
In the crystal, molecules are connected through the intermolecular C-H···N and N-H···N hydrogen bonds, generating a R 2 2 (17) (Bernstein et al., 1995) motif and also chain along a axis. In addition, another pair of intermolecular, C-H···N hydrogen bond link neighbouring molecules, forming an inversion dimer and generate a R 2 2 (20) ring motif (Table 1).

Experimental
Initially a mixture of 4-methylbenzaldehyde (2 mmol, 0.24 g), malononitrile (3 mmol, 0.198 g), piperidine (1.5 mmol, 0.128 g) and was stirred without any solvent at room temperature. A solid appeared immediately which was dissolved in a minimum amount (3 ml) of ethanol and the solution was refluxed until completion of the reaction (monitered by TLC).
The reaction mixture was cooled. Ethanol was evaporated under reduced pressure and the residue was extracted with dichloromethane (3×10ml). Evaporation of solvent left the crude solid which was subjected to silica gel column chromatography [25 : 75 / ethyl acetate : hexane] and the product was recrystallized from dichloromethane.

Refinement
H atoms were placed in idealized positions and allowed to ride on the parent atoms,with C-H bond lengths fixed to 0.93Å (aromatic H), 0.96Å (methyl H),0.97Å (methylene H), 0.86Å (N-H) and U iso (H) = 1.2-1.5U eq (C,N).

Computing details
Data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009    The packing structure of the title compound shows another pair of intermolecular C-H···N hydrogen bonds to form inversion dimer. H atoms have been omited for clarity. Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 > 2σ(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.