[(4E)-1-Methyl-2,6-diphenyl-3-(propan-2-yl)piperidin-4-ylidene]amino 3-methylbenzoate

In the title compound, C29H32N2O2, the piperidine ring exists in a chair conformation (the bond-angle sum at the sp 2-hybridized C atom is 359.79°). The phenyl rings and the methyl group substituted on the heterocyclic ring are in equatorial orientations. In the crystal, pairs of C—H⋯π interactions result in the formation of inversion dimers.

In the title compound, C 29 H 32 N 2 O 2 , the piperidine ring exists in a chair conformation (the bond-angle sum at the sp 2hybridized C atom is 359.79 ). The phenyl rings and the methyl group substituted on the heterocyclic ring are in equatorial orientations. In the crystal, pairs of C-HÁ Á Á interactions result in the formation of inversion dimers.
Cg1 is the centroid of the C16-C21 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.
The molecule exists in its E-isomeric form.
The packing of the molecules within the crystal is shown in Fig. 2. The crystal structure is stabilized by intermolecular C11-H11···Cg1 i hydrogen bonding interactions resulting in centrosymmetric dimers about inversion centers, where Cg1 is the center of gravity of the ring atoms (C16-C21) ( Table 1).

Experimental
3-Isopropyl-2,6-diphenylpiperidin-4-one was synthesized by Mannich condensation using benzaldehyde (2 mol), ammonium acetate (1 mol) and isobutyl methyl ketone (1 mol) in absolute ethanol, 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 for two hours yielding (4E)-1-methyl-3-isopropyl-2,6-diphenylpiperidin -4-one. The oximation was done by hydroxylamine hydrochloride (2 mol) in the presence of sodium acetate (2 mol) in ethanol (10 ml) and refluxed for two hours. 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 the dropwise addition of phosphorus oxychloride (0.21 mL, 2.3 mmol) 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. The product was filtered and dried to get a white solid (0.62 g, 91%) 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···Cg hydrogen bond interaction (dashed line). 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.