r-2,c-6-Bis(3-methoxyphenyl)-t-3,t-5-dimethylpiperidin-4-one

In the title compound, C21H25NO3, the piperidinone ring adopts a chair conformation with an equatorial orientation of all substituents; the 3-methoxyphenyl groups make a dihedral angle of 60.26 (15)°. The carbonyl group O atom is disordered over two positions in a 0.643 (3):0.357 (3) ratio. The crystal structure is stabilized by N—H⋯O and C—H⋯O hydrogen bonding.

In the title compound, C 21 H 25 NO 3 , the piperidinone ring adopts a chair conformation with an equatorial orientation of all substituents; the 3-methoxyphenyl groups make a dihedral angle of 60.26 (15) . The carbonyl group O atom is disordered over two positions in a 0.643 (3):0.357 (3) ratio. The crystal structure is stabilized by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonding. H atoms treated by a mixture of independent and constrained refinement Á max = 0.12 e Å À3 Á min = À0.14 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). r-2,c-6-Bis(3-methoxyphenyl)-t-3,t-5-dimethylpiperidin-4-one P. Parthiban, V. Ramkumar, N. A. Kumar, J. S. Kim and Y. T. Jeong Comment Substituted piperidin-4-ones are very important class of compounds due to their presence in a wide variety of naturally occurring alkaloids, active pharmaceutical ingredients and intermediates and as building blocks of many drugs. (Angle & Breitenbucher, 1995;Katritzky & Fan, 1990). The piperidone heterocycle predominantly adopts the chair conformation (Ramachandran et al., 2007;Balamurugan et al., 2008) whereas depending upon the substitution, the configuration and conformation can be different (Thiruvalluvar et al., 2007;Gayathri et al., 2008). Hence, the present single-crystal XRD studies on the title compound have been carried out to find out the impact on the configuration and conformation of the piperidone ring due to the presence of methyl group on both sides of the carbonyl and methoxy group on the meta position of the phenyl rings.

Related literature
In the title compound C 21 H 25 NO 3 , as shown in figure, the piperidone heterocycle adopts a chair conformation with equatorial disposition of all the substituents. The equatorial orientations of the methyl and phenyl groups are confirmed by their torsion angles. The aryl groups attached to to the piperidone ring on both sides of the secondary amino group make a dihedral angle of 60.26 (15)°.

Experimental
The title compound was synthesized by the one pot condensation of 2-pentanone, meta methoxybenzaldehyde and ammonium acetate in 1:2:1 ratio, using ethanol as a solvent by adopting the literature procedure of modified Mannich reaction, reported by Noller & Baliah (1948) for similar type compounds. The mixture was warmed and kept aside overnight. The formed 2,6-bis(3-methoxyphenyl)-3, 5-dimethylpiperidin-4-one was filtered off and washed with 1:5 ethanol, ether mixture. Thus, the obtained crude product was purified by recrystallization with ethanol to afford the colorless crystals with diffraction quality.

Refinement
The structure was solved in the space group C2/c. The oxygen atom attached to the piperidine ring is disordered over two orientation in a 0.643 (3):0.357 (3) ratio. Nitrogen H atom was located in a difference Fourier map and refined isotropically.

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 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 Rfactors based on ALL data will be even larger.