Methyl ({[(4E)-1,3-dimethyl-2,6-diphenylpiperidin-4-ylidene]amino}oxy)acetate

In the title compound, C22H26N2O3, the piperidine ring exhibits a chair conformation. The phenyl rings attached to the piperidine at the 2- and 6-positions have axial orientations. These rings make a dihedral angle of 49.75 (11)°. The aminooxy acetate group attached at the 4-position has an equatorial orientation. In the crystal, inversion dimers linked by pairs of C—H⋯π interactions occur.

Oxime ether derivatives of 2,6-diphenyl-piperidine-4-one with N-methyl substituent enhanced the efficacy of the in vitro antiproliferative activity against human cervical carcinoma cell lines (Parthiban et al., 2011). Recently oxime ether derivatives of aminooxy acetic acid were synthesized and studied for their effects on the senescence of cut carnation flowers (Zeng et al., 2012). Due to the above importance, the crystal data for the title compound was carried out by Xray diffraction.
The bond distances and bond angles in the title compound agree very well with the corresponding values reported in closely related compound (Park et al., 2012a;2012b).
The main plane of piperidine ring makes the dihedral angle of 81.82° and 86.73° with the phenyl rings at the 2 and 6 positions respectively. The dihedral angle between the two phenyl rings is 49.75°. The crystal is stabilized by C-H···O interactions. The packing is further stabilized by C-H···π and C22-H22B···Cg2 i interactions, where Cg2 is the centroid of (C1-C6) ring. Symmetry code: (i) 1-x, 1-y, 1-z.

Experimental
To a stirred mixture of 1,3-dimethyl-2,6-diphenylpiperidin-4-one oxime (0.88 g, 3 mmol) and K 2 CO 3 (0.42 g, 1 eq.) in acetonitrile (15 ml) at 353 K, methyl chloroacetate (0.25 ml, 1 eq) was added dropwise over a period of 5 min and stirring continued for 7.5 hrs at the same condition. The progress of the reaction was monitored by TLC. After completion of the reaction K 2 CO 3 was removed by filtration and the solvent was evaporated to getcrude product. Pure product was obtained by coloumn chromotography using petroleum ether/ethyl acetate (9.5/0.5) mixture as the eluent. Yield: 0.77 g (70%).

Refinement
All the hydrogen atoms were geometrically fixed and allowed to ride on their parent atoms with C-H = 0.93-0.98 Å and U iso (H) = 1.5U eq (C) for methyl H atoms and U iso (H) = 1.2U eq (C) for other H.  The molecular structure and labelling scheme for title compound. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as a small spheres of arbitrary radius.  A packing diagram for title compound.  (7) Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All s.u.'s are estimated from the variances of the (full) variance-covariance matrix. The cell s.u.'s are taken into account in the estimation of distances, angles and torsion angles. 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.