N-(2-Fluorobenzyloxy)-1,3,5-trimethyl-2,6-diphenylpiperidin-4-imine

In the title compound, C27H29FN2O, the piperidine ring has a twisted boat conformation and all ring substituents occupy equatorial positions. The dihedral angle formed between the phenyl rings is 66.71 (12)°, and the phenyl rings form dihedral angles of 46.60 (13) and 43.75 (13)° with the fluorobenzene ring, which occupies a position coplanar to the methoxy(methylidene)amine residue [N—O—C—C torsion angle = −179.5 (2)°]. In the crystal, a complex network of C—H⋯π interactions connects the molecules into a three-dimensional architecture.


Comment
In a program aimed towards synthesizing efficient biological agents, the title compound, (I), was generated (Ramalingan et al., 2006) as molecules with a 2,6-diarylpiperidine core are known to exhibit potent biological activities (Ramachandran et al., 2011;Ramalingan et al., 2004). Herein, the crystal and molecular structure of the title compound is described.
In the title molecule ( Fig. 1), the piperidine ring adopts a twist-boat conformation and all ring-substituents occupy equatorial positions. In the chloro (Ramalingan et al., 2012b) and bromo (Ramalingan et al., 2012b) analogues of the title compound, which lack a C-bound methyl substituent and where the piperidine ring adopts a chair conformation, all Cbound substituents are found in equatorial positions and the N-bound methyl group is in a bisectional position (Ramalingan et al., 2012a(Ramalingan et al., , 2012b. The dihedral angle formed between the C15-C20 and C21-C26 benzene rings in the title compound is 66.71 (12)°, and each forms a dihedral angle of 46.60 (13) and 43.75 (13)°, respectively, with the fluorobenzene ring, which occupies a position co-planar to the methoxy(methylidene)amine residue, as seen in the N1-O1-C7-C6 torsion angle of -179.5 (2)°. In the aforementioned chloro and bromo derivatives, orthogonal and co-planar orientations were observed in this region of the respective molecule, respectively. The conformation about the imine A complex network of C-H···π interactions connects the molecules into a three-dimensional architecture (Table 1 and

Experimental
For full details of the synthesis, refer to Ramalingan et al. (2006). Re-crystallization was performed by slow evaporation of an ethanolic solution of (I) which afforded colourless crystals. M.pt: 378-379 K.

Refinement
Carbon-bound H-atoms were placed in calculated positions [C-H = 0.95-1.00 Å, U iso (H) = 1.2-1.5U eq (C)] and were included in the refinement in the riding model approximation. In the absence of significant anomalous scattering effects, 2345 Friedel pairs were averaged in the final refinement.   A view in projection down the a axis of the unit-cell contents for the title compound, the C-H···π interactions are shown as purple dashed lines.

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.