[(4E)-3-Ethyl-1-methyl-2,6-diphenylpiperidin-4-ylidene]amino 3-methylbenzoate

In the title compound, C28H30N2O2, the piperidine ring exists in a chair conformation with an equatorial orientation of the phenyl rings and methyl group substituted on the heterocycle. In the crystal, C—H⋯π interactions result in chains of molecules running parallel to the a-axis direction.

In the title compound, C 28 H 30 N 2 O 2 , the piperidine ring exists in a chair conformation with an equatorial orientation of the phenyl rings and methyl group substituted on the heterocycle. In the crystal, C-HÁ Á Á interactions result in chains of molecules running parallel to the a-axis direction.
Cg1 is the centroid of the C15-C20 ring.

Comment
Piperdin-4-one nucleus is an important pharmacophore due to its broad spectrum of biological actions ranging from antibacterial to anticancer (Parthiban et al., 2009;2011). Hence, the synthesis and steriochemical analysis of piperdin-4one nucleus based pharmacophores has gained much interest in the field of medicinal chemistry.
In the crystal, the molecules are stabilized by intermolecular C11-H11···Cg1 i and C23-H23···Cg1 ii hydrogen bond interactions, where Cg1 is the center of gravity of ring atoms involving C15-C20 of the interacting molecules, respectively ( Table 1). The packing of the molecules within the crystal is shown in Fig. 2.

Experimental
3-Ethyl-2,6-diphenylpiperidin-4-one was synthesized by Mannich condensation using benzaldehyde (2 mol), ammonium acetate (1 mol) and ethyl methyl ketone (1 mol) in absolute ethanol and warmed for 30 min and stirred overnight at room temperature. The product was treated with methyl iodide (1.5 mol) in the presence of potassium carbonate (2 mol) in acetone (10 ml) and refluxed to give 1-methyl-3-ethyl-2,6-diphenylpiperidin-4-one. The oximation was done by hydroxylamine hydrochloride (2 mol) in presence of sodium acetate (2 mol) in ethanol (10 ml) and refluxed. The resulting oxime (0.5 g, 1.55 mmol) was stirred with dry pyridine (5 ml), added 3-methylbenzoic acid (0.23 g, 1.7 mmol) followed by phosphorus oxychloride (0.21 ml, 2.3 mmol) in dropwise addition and stirred at ambient temperature for 15 min; the progress of the reaction was monitored by thin layer chromatography. Upon completion of the reaction, saturated sodium bicarbonate solution (8 ml) was added to the reaction mixture, solid was formed and it was filtered and dried to get a white solid (0.58 g, 87.8%) which was recrystallized from ethanol to yield crystals suitable for X-ray crystallographic studies.

Refinement
H atoms were positioned geometrically (C-H = 0.93-0.98 Å) and allowed to ride on their parent atoms, with U iso (H) = 1.5U eq (C) for methyl H and 1.2U eq (C) for other H atoms.

Figure 1
The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as small spheres of arbitrary radius.  The crystal packing arrangement of the title compound viewed down the b axis showing intermolecular C-H···π hydrogen bond interactions (dashed lines). symmetry codes: where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.15 e Å −3 Δρ min = −0.17 e Å −3

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.