1-(2-Bromoacetyl)-3-methyl-2,6-diphenylpiperidin-4-one

In the title compound, C20H20BrNO2, the piperidone ring adopts a boat conformation. The phenyl rings are oriented at dihedral angles of 97.8 (2) and 96.0 (1)° with respect to the best plane through the piperidine ring. The dihedral angle between the two phenyl rings is 49.7 (1)°. In the crystal, bifurcated C—H⋯O hydrogen bonds form a R 2 1(7) ring motif, linking the molecules into centrosymmetric dimers.

In the title compound, C 20 H 20 BrNO 2 , the piperidone ring adopts a boat conformation. The phenyl rings are oriented at dihedral angles of 97.8 (2) and 96.0 (1) with respect to the best plane through the piperidine ring. The dihedral angle between the two phenyl rings is 49.7 (1) . In the crystal, bifurcated C-HÁ Á ÁO hydrogen bonds form a R 2 1 (7) ring motif, linking the molecules into centrosymmetric dimers.

Related literature
For the biological activity of functionalized piperidines, see: Richardo et al. (1979);Schneider (1996); Mukhtar & Wright (2005); Aridoss et al. (2007); Winkler & Holan (1989). For related structures see: Aridoss et al. (2009a,b). For ring conformational analysis, see: Cremer & Pople (1975);Nardelli (1983 Table 1 Hydrogen-bond geometry (Å , ). GA and YTJ are grateful for the support provided by the second stage of the BK21 program, Republic of Korea. SS and DV thank the TBI X-ray Facility, CAS in Crystallography and Biophysics, University of Madras, India, for the data collection and the University Grants Commission (UGC&SAP) for financial support.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5275).
interestingly, in many biologically active compounds such as anopterine, pergoline, scopolamine and morphine (Richardo et al., 1979, Schneider, 1996, Mukhtar & Wright, 2005. Piperidones also have high impact in medicinal field owing to their role as key chiral intermediates for the preparation of a variety of natural, synthetic and semi-synthetic pharmacophores with marked anticancer and anti-HIV activities (Winkler & Holan, 1989). It has been established by our earlier studies (Aridoss et al. 2009a, Aridoss et al. 2009b) that unlike the substitution of either alky or aryl system in the carbon skeleton of piperidone, incorporation of either chloroacetyl or bromoacetyl functionality at the nitrogen of piperidone remarkably changes the rigid chair confirmation of heterocyclic ring into non-chair conformation of its preference. Thus to find out the change in conformation of 2,6-diphenyl-3-methylpiperidin-4-one upon bromoacetylation, the title compound was synthesized and discussed here with its X-ray crystallographic data.
In the present structure, the piperidone ring adopts a boat conformation with atoms C1 and C4 deviating by 0.395 (1) and 0.334 (1) Å, respectively, from the least-sqaures plane defined by the remaining atoms (N1/C2/C3/C5) in the ring. When compared with the reported structures of piperidone derivatives (Aridoss et al., 2009b), it is clear that the conformation of the piperidone ring is highly influenced by the substitutions at various positions.The sum of the bond angles around the atom N1(357.6 (6)°) of the piperidone ring in the molecule is in accordance with sp 2 hybridization.

Experimental
The title compound was obtained by adopting our earlier method (Aridoss et al. 2007). To a solution of 2,6-diphenyl-3methylpiperidin -4-one (1 equiv.) and NEt3 (1.5 equiv.) in freshly distilled benzene, bromoacetyl chloride (1 equiv.) in benzene was added in drop wise. After the completion of reaction, the crude compound was obtained by evaporation of its ethyl acetate extract. This upon recrystallization in distilled ethanol afforded fine white crystals suitable for X-ray diffraction study.

Refinement
H atoms were positioned geometrically (C-H=0.93-0.98Å) 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.

Data collection
Bruker SMART APEXII area-detector diffractometer 4398 independent reflections

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.