Crystal structure and Hirshfeld surface analysis of 3-octyl-4-oxo-2,6-bis(3,4,5-trimethoxyphenyl)piperidinium chloride

The title compound was synthesized by a one-pot Mannich condensation reaction. In the crystal, centrosymmetric dimers are linked into layers parallel to (011) by N—H⋯Cl and C—H⋯Cl hydrogen bonds. A Hirshfeld surface analysis indicates that O—H (20.5%) interactions make the largest contribution to the crystal packing.


Chemical context
Piperidine is a naturally occurring bioactive alkaloid (Hu et al., 2002;Finke et al., 2001;Taniguchi & Ogasawara, 2000) and the heterocyclic six-membered nitrogen-containing piperidine ring is an essential structural part of many important drugs including paroxetine, raloxifene, haloperidol, droperidol and minoxidiln (Wagstaff et al., 2002). 2,6-Diphenyl-substituted piperdine-4-one derivatives are important because of their potential biological activities such as antitumor, antimicrobial, analgesic, local anesthetic, antidepressant and anti-inflammatory (Ká lai et al., 2011;Leonova et al., 2010;El-Subbagh et al., 2000;Jerom & Spencer, 1988). This wide range of biological activities prompted us to synthesize novel 2,6-diphenyl piperdine-4-one derivatives with enhanced biological activities. In a continuation of this work, the title compound was synthesized using a one-pot Mannich condensation reaction as reported by Noller & Baliah (1948). The adopted one-pot reaction is convenient, simple, easy way for separation of the product with possible high yield. A Hirshfield surface analysis of the title compound was carried out in order to study how different functionalities can affect the crystal packing. ISSN 2056-9890

Supramolecular features
In the crystal, centrosymmetrically-related molecules are linked into dimers through pairs of N-HÁ Á ÁO hydrogen bonds (Table 1) forming rings with an R 2 2 (16) graph-set motif.

Hirshfeld surface analysis
A quantitative analysis of all type of interactions in the title compound was performed using Hirshfeld surface analysis. The Hirshfeld surface mapped over d norm (Spackman & Jayatilaka, 2009) is shown in Fig. 3 where the red areas on the surface indicate short contacts (as compared to the sum of the van der Waals radii), while the blue areas indicate longer contacts and white areas indicate contacts with distances equal to the sum of the van der Waals radii. Two-dimensional fingerprint plots are shown in Fig. 4  Symmetry codes: (i) Àx þ 1; Ày þ 1; Àz þ 1; (ii) x; Ày þ 1 2 ; z þ 1 2 ; (iii) x þ 1; Ày þ 1 2 ; z þ 1 2 .

Figure 2
Packing diagram of the title compound viewed approximately along the c axis. Turquoise lines indicate hydrogen bonds.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.

Synthesis and crystallization
The title compound was synthesized according to the procedure given in literature (Noller & Baliah, 1948). A mixture of 2-undecanone, (0.206 ml, 1 mmol), 3,4,5-trimethoxybenzaldehyde (0.39 g, 2 mmol) and ammonium acetate (0.077 g, 1 mmol) in ethanol (50 ml) was allowed to reflux for three hours. The progress of reaction was monitored by TLC. After completion of the reaction, the mixture was acidified with dilute hydrochloric acid (5 mL) and the resulting precipitate was collected, washed with an ethanol-ether mixture (1:4 v/v), dried and redissolved in ethanol. Crystals suitable for single-crystal X-ray diffraction analysis were obtained on slow evaporation of the solvent at room temperature.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms on methyl, methylene and benzene were positioned geometrically with C-H = 0.95-1.00 Å and constrained to ride on their parent atoms with U iso (H) = 1.2U eq (C) or 1.5U eq (C) for methyl H atoms. A rotating model was used for the methyl groups. The N-bound hydrogen atoms were located in a difference-Fourier map and freely refined.

3-Octyl-4-oxo-2,6-bis(3,4,5-trimethoxyphenyl)piperidinium chloride
Crystal data 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq