1-Dichloroacetyl-t-3,t-5-dimethyl-r-2,c-6-diphenylpiperidin-4-one

In the title compound, C21H21Cl2NO2, the piperidine ring adopts a distorted boat conformation. The phenyl rings substituted at the 2- and 6-positions of the piperidine ring subtend angles of 87.9 (7) and 70.8 (9)°, respectively, with the best plane through the piperidine ring. In the crystal, molecules are connected by C—H⋯O and C—H⋯Cl interactions into layers in the ab plane.

In the title compound, C 21 H 21 Cl 2 NO 2 , the piperidine ring adopts a distorted boat conformation. The phenyl rings substituted at the 2-and 6-positions of the piperidine ring subtend angles of 87.9 (7) and 70.8 (9) , respectively, with the best plane through the piperidine ring. In the crystal, molecules are connected by C-HÁ Á ÁO and C-HÁ Á ÁCl interactions into layers in the ab plane.

D-HÁ
The ORTEP plot of the molecule is shown in Fig. 1. The title compound crystallizes in the monoclinic space group P2 1 .
The piperidine ring adopts a distorted boat conformation. The puckering parameters (Cremer & Pople, 1975)  The crystal packing reveals that the molecules are linked through a network of C-H···O and C-H···Cl intermolecular interactions. Atoms C2 and C20 of the molecule at (x, y, z) donate a proton to bifurcated acceptor atom O1 of the molecule at (1 -x,-1/2 + y,-z), which form two different C(5) and C(8) chains (Bernstein et al., 1995) forming layers in the ab plane as shown in Fig. 2.

Experimental
t-3,t-5-Dimethyl-r-2,c-6-diphenylpiperidin-4-one (5 mmol) was dissolved in 60 ml of anhydrous benzene. To this solution, dichloroacetylchloride (20 mmol) and triethylamine (20 mmol) were added and the reaction mixture was allowed to stirr for 8 h. The course of the reaction was monitored by TLC. The organic layer was dried over anhydrous Na 2 SO 4 and the resulting pasty mass was purified by recrystallization from ethyl acetate. Yield: 70%, Melting point: 190-

Refinement
All H atom were found in a difference map but they 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 atoms and 1.2U eq (C) for all other H atoms.

Figure 1
The molecular structure of the title compound, showing the atomic numbering and displacement ellipsoids drawn at 50% probability level.  The crystal packing of the molecules. H atoms not involved in hydrogen bonding (dashed lines) have been omitted for clarity. 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.