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

In the title molecule, C19H19Cl2NO, the piperidine ring adopts a chair conformation and the dihedral angle between the two benzene rings is 77.23 (7)°. In the crystal structure, molecules are linked by N—H⋯O and C—H⋯O hydrogen bonds, and a weak C—H⋯π interaction is also observed.

In the title molecule, C 19 H 19 Cl 2 NO, the piperidine ring adopts a chair conformation and the dihedral angle between the two benzene rings is 77.23 (7) . In the crystal structure, molecules are linked by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, and a weak C-HÁ Á Á interaction is also observed.

Comment
Piperidones are an important group of heterocyclic compounds in the field of medicinal chemistry due to their biological activities, including cytotoxic and anticancer properties (Dimmock et al., 2001). Piperidones were also reported to possess analgesic, anti-inflammatory, central nervous system (CNS), local anaesthetic, anticancer and antimicrobial activity (Perumal et al., 2001). The design and synthesis of conformationally anchored molecules is an important approach towards improving potency and selectivity. One such class of compounds constitutes piperidin-4-ones and their derivatives, whose synthesis and stereodynamics are well investigated (Ponnuswamy et al., 2002). The crystal structure of r-2,c-6-Bis(4-chlorophenyl)-t-3-isopropyl-1-nitrosopiperidin-4-one has been reported, wherein the piperidine ring adopts a chair conformation (Gayathri et al., 2008).

Experimental
The procedure adopted for the preparation of the title heterocyclic compound is similar to that of Noller & Baliah (1948).
Ammonium acetate (7.7 g, 0.1 mol), 4-chlorobenzaldehyde (28.1 g, 0.2 mol) and 3-methyl-2-butanone (10.7 ml, 0.1 mol) were dissolved in 70 ml of rectified spirit. The resulting solution was heated to boiling and set aside for a day. The oily base obtained was converted into its hydrochloride by the addition of concentrated hydrochloric acid and the separated solid was filtered. Then the hydrochloride was neutralized with liquid ammonia. The resulting solid was filtered and purified by recrystallization from ethanol to yield colourless plates of (I). The yield of the product obtained was 28.65 g (82%).

Refinement
Atom H1 attached to N1 was located in a difference fourier map and refined isotropically. The 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 1.2 for all other H atoms.  r-2,c-6-Bis(4-chlorophenyl)-c-3,t-3-dimethylpiperidin-4-one