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

The piperidone ring in the title compound, C23H26ClNO4, adopts a boat conformation with its two out-of-plane C atoms deviating by 0.597 (2) and 0.630 (2) Å from the least-squares plane of the rest of atoms in the ring. The two aromatic rings are roughly perpendicular to each other, making a dihedral angle of 75.1 (1)°, and a C—H⋯π intramolecular interaction is observed. The crystal packing is stabilized by a C—H⋯O intermolecular interaction, generating a chain with a C(9) motif along the a axis.

The piperidone ring in the title compound, C 23 H 26 ClNO 4 , adopts a boat conformation with its two out-of-plane C atoms deviating by 0.597 (2) and 0.630 (2) Å from the least-squares plane of the rest of atoms in the ring. The two aromatic rings are roughly perpendicular to each other, making a dihedral angle of 75.1 (1) , and a C-HÁ Á Á intramolecular interaction is observed. The crystal packing is stabilized by a C-HÁ Á ÁO intermolecular interaction, generating a chain with a C(9) motif along the a axis.
The molecule of (I) is stabilized by weak C-H···O and C-H···π intramolecular interactions. In C-H···π intramolecular interaction, atom C9 acts as donor to the centroid (Cg) of the phenyl ring C17-C22 with H···Cg distance of 2.69 Å. The crystal packing is stabilized by C-H···O intermolecular interaction, wherein atom C23 acts as donor to O1 (1 + x, y, z) generating a chain C(9) along the a axis.

S2. Experimental
The title compound was obtained by adopting our earlier method (Aridoss, Balasubramanian, Parthiban & Kabilan, 2007). To a solution of 2,6-bis(2-methoxyphenyl)-3,5-dimethylpiperidin-4-one (1 equiv.) and NEt 3 (1.5 equiv.) in freshly distilled benzene, chloroacetyl chloride (1 equiv.) in benzene was added in drop wise. Stirring was continued until the completion of reaction. Later, it was poured into water and extracted with ethyl acetate. The combined organic extracts was then washed well with 3% sodium bicarbonate solution, brine and dried over anhydrous sodium sulfate. This upon evaporation and subsequent recrystallization of title compound in distilled ethanol afforded fine white crystals suitable for X-ray diffraction study.

S3. Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.98 Å, and with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C).

Figure 1
The molecular structure of title compound, (I), showing 30% probability displacement ellipsoids.  The molecular packing of (I), showing intramolecular C-H···π and intermolecular C-H···O interactions. For clarity, hydrogen atoms which are not involved in hydrogen bonding are omitted.

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.