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

In the title compound, C21H23NO2, the piperidine ring adopts a distorted boat conformation. The two phenyl rings form dihedral angles of 64.6 (1) and 87.8 (1)° with the best plane through the piperidine ring. The crystal packing is governed by intermolecular C—H⋯O interactions.

In the title compound, C 21 H 23 NO 2 , the piperidine ring adopts a distorted boat conformation. The two phenyl rings form dihedral angles of 64.6 (1) and 87.8 (1) with the best plane through the piperidine ring. The crystal packing is governed by intermolecular C-HÁ Á ÁO interactions.

Comment
The design and synthesis of conformationally anchored molecules are important due its potency and selectivity for designing drugs. The piperidin-4-ones are one such class of compounds to be investigated to understand the stereodynamics and other structural features (Ponnuswamy et al., 2002). In view of these importance and to ascertain the molecular conformation, crystallographic study of the title compound has been carried out.
The ORTEP diagram of the title compound is shown in Fig.1. The piperidine ring adopts a distorted boat conformation.
The crystal packing is controlled by C-H···O types of intra and intermolecular interactions in addition to van der Waals forces. Atom C8 at (x, y, z) donates a proton to O2 (1 -x,1/2 + y,-z), which forms a C(8) (Bernstein, et al., 1995) zigzag chain running along b axis shown in Fig. 2.

Refinement
In the absence of anomalous scatterers Friedel pairs were merged and the absolute configuration was arbitrarily set. All H atoms were positioned geometrically (C-H=0.93-0.98 Å) and allowed to ride on their parent atoms, with 1.5U eq (C) for methyl H and 1.2 U eq (C) for other H atoms.  1-Acetyl-c-3,t-3-dimethyl-r-2,c-6-diphenylpiperidin-4-one

Special details
Geometry. All e.s. 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.