1-Chloroacetyl-2,6-bis(2-chlorophenyl)-3,5-dimethylpiperidin-4-one oxime

In the title compound, C21H21Cl3N2O2, the piperidine ring adopts a distorted boat conformation. One of the chlorophenyl rings is almost perpendicular to the best plane through piperidine ring, making a dihedral angle of 88.7 (1)°, whereas the other ring is twisted by 71.8 (1)°. The crystal packing is stabilized by intermolecular C—H⋯O, C—H⋯Cl and O—H⋯O interactions.

In the title compound, C 21 H 21 Cl 3 N 2 O 2 , the piperidine ring adopts a distorted boat conformation. One of the chlorophenyl rings is almost perpendicular to the best plane through piperidine ring, making a dihedral angle of 88.7 (1) , whereas the other ring is twisted by 71.8 (1) . The crystal packing is stabilized by intermolecular C-HÁ Á ÁO, C-HÁ Á ÁCl and O-HÁ Á ÁO interactions.
The piperidine ring in the molecule (Fig. 1) adopts a distorted boat conformation with the puckering parameters (Cremer & Pople, 1975) and the asymmetry parameters (Nardelli, 1983) are: q 2 = 0.673 (2) Å, q 3 = 0.080 (2) Å, φ 2 = 70.2 (2)° and Δ s (C2 & C5)= 10.5 (2)°. One of the chlorophenyl rings is almost perpendicular to the best plane of piperidine ring with a dihedral angle of 88.7 (1)°, whereas the other ring is twisted by 71.8 (1)°. The sum of the bond angles around the atom N1 (357.4°) of the piperidine ring in the molecule is in accordance with sp2 hybridized state. The chloro-acetyl group adpots a twist conformation which can be seen from the torsion angle of 91.

Experimental
A mixture of N-chloroacetyl-3,5-dimethyl-2,6-bis(o-chlorophenyl piperridin-4-one1 (50 mmol), sodiumacetate trihydrate (150 mmol), hydroxylamine hydrochloride (60 mmol) and 50 ml of ethanol were taken in a RB flask. The reaction mixture was refluxed for about half an hour. The progress of the reaction was monitored by TLC. After the usual workup, the oxime was purified by column chromatography and the single crystals were grwon by slow evaporation using ethanol as solvent (Aridoss et al., 2007).

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

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq