3,3-Dimethyl-cis-2,6-di-p-tolylpiperidin-4-one

In the title molecule, C21H25NO, the piperidine ring adopts a chair conformation. The benzene rings and one of the methyl groups attached to the piperidine ring have equatorial orientations. The dihedral angle between the two benzene rings is 72.53 (9)°. In the crystal, molecules are linked by N—H⋯O hydrogen bonds. Weak C—H⋯π interactions involving the benzene rings are also present in the crystal structure.

In the title molecule, C 21 H 25 NO, the piperidine ring adopts a chair conformation. The benzene rings and one of the methyl groups attached to the piperidine ring have equatorial orientations. The dihedral angle between the two benzene rings is 72.53 (9) . In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds. Weak C-HÁ Á Á interactions involving the benzene rings are also present in the crystal structure.

Experimental
The procedure adopted by Noller & Baliah (1948) was followed for the preparation of the title compound. To the solution of ammonium acetate (3.85 g, 0.05 mol) in dry ethanol, p-tolualdehyde (12.0 g, 0.1 mol) and isopropyl methyl ketone (5.35 ml, 0.05 mol) were added and allowed to reflux on a water bath for 1 h. The resulting solution was kept at room temperature for overnight and the precipitated solid was filtered. The solid was crystallized using benzene -petroleum ether mixture.
The yield of the product obtained was 7.36 g (48%).

Refinement
In the absence of any anamalous scatterers in the molecule, the Friedel pairs were merged. The absolute structure in the present model has been chosen arbitrarily. Atom H1 on N1 was located in a difference Fourier map and refined isotropically.
Remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.95, 0.98, 0.99 and 1.00 Å for Csp 2 , methyl, methylene and methine C, respectively; U iso (H) = kU eq (C), where k = 1.5 for methyl and

Special details
Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles 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 > 2σ(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.