2-Chloro-1-(3,3-dimethyl-2,6-diphenylpiperidin-1-yl)ethanone

In the title compound, C21H24ClNO, the piperidine ring adopts a chair conformation. The two phenyl rings are inclined to one another by 20.7 (1)°, and are inclined to the mean plane of the four planar atoms of the piperidine ring by 87.64 (10) and 70.8 (1)°. The molecular structure features short intramolecular C—H⋯Cl and C—H⋯O contacts. In the crystal, there are no significant intermolecular interactions present.

In the title compound, C 21 H 24 ClNO, the piperidine ring adopts a chair conformation. The two phenyl rings are inclined to one another by 20.7 (1) , and are inclined to the mean plane of the four planar atoms of the piperidine ring by 87.64 (10) and 70.8 (1) . The molecular structure features short intramolecular C-HÁ Á ÁCl and C-HÁ Á ÁO contacts. In the crystal, there are no significant intermolecular interactions present.

Comment
The piperidine sub-structure is a ubiquitous structural feature of many alkaloids, natural products and drug candidates (Weintraub et al., 2003). The motivation for biological trials arises as piperidine derivatives are an important class of heterocyclic compounds with potent pharmacological and biological activities (Ramalingan et al., 2004;Ramachandran et al., 2011). We report herein on the synthesis and crystal structure of a new piperidine derivative.
In the title molecule, Fig The molecule is stabilized by short intramolecular C-H···Cl and C-H···O contacts (Table 1).
In the crystal, the molecules stack along the c axis direction without any specific interactions (Fig. 2).

Experimental
The title compound was synthesized according to the published procedure (Venkatraj et al., 2008). A mixture of piperidine (5 mmol), chloroacetylchloride (20 mmol) and triethylamine (20 mmol) in anhydrous benzene (20 ml) was stirred at rt for 7 h. The precipitated ammonium salt was washed with water (4 × 10 ml) and the benzene solution was dried and concentrated. The pasty mass was purified by crystallization from ethanol giving colourless block-like crystals [M.p. 377-379 K].

Refinement
H atoms were positioned geometrically and treated as riding atoms: C-H = 0.93 -0.98 Å with U iso (H) = 1.5U eq (Cmethyl) and = 1.2U eq (N,C) for other H atoms.  The molecular structure of the title molecule, with displacement ellipsoids drawn at the 30% probability level.  The crystal packing of the title compound, viewed along the b axis. The dashed lines indicate the short intramolecular C-H···O and C-H···Cl contacts (see Table 1 for details). 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.