(E,E)-1-Methyl-2,6-distyrylpyridinium iodide

In the title compound, C22H20N+·I−, the dihedral angles between the central pyridine ring and two outer benzene rings are 15.30 (10) and 11.82 (11)°. There are intermolecular π–π stacking interactions between the nearest phenyl ring over an inversion-related pyridyl ring, the shortest centroid–centroid distance being 3.672 (3) Å. The crystal structure of the compound indicates the 2,6-distyryl substituents have an E configuration.

In the title compound, C 22 H 20 N + ÁI À , the dihedral angles between the central pyridine ring and two outer benzene rings are 15.30 (10) and 11.82 (11) . There are intermolecularstacking interactions between the nearest phenyl ring over an inversion-related pyridyl ring, the shortest centroid-centroid distance being 3.672 (3) Å . The crystal structure of the compound indicates the 2,6-distyryl substituents have an E configuration.

Comment
In continuation of our work on the lobeline analogues, and structure-affinity relationships of novel ligands for the vesicular monoamine transporter (Zheng et al., 2005), we have undertaken the design, synthesis and structural analysis of a series of phenyl substituted N-alkyl distyrylpyridine analogs. The primary reasons for the X-ray analysis of the title compound was to confirm the geometry of 2,6-distyryl groups and to obtain detailed information on the molecular structure. This information will be useful in structure-activity relationship (SAR) studies. The title compound was prepared by the reaction of N-methyl, 2,6-lutidine iodide with benzaldehyde in the presence of pyrrolidine in ethanol under microwave irradiation at 25-29 W power level and at 130 °C for 3 minutes (Biotage microwave initiator). The compound was recrystallized from ethanol. The molecular structure and the atom-numbering scheme are shown in Fig.1. The X-ray studies revealed that the 2,6-distyryl substituents in the title compound both have E geometry. The central pyridine ring makes a dihedral angle of 15.30 (10)°a nd 11.82 (11)° with the adjacent phenyl rings.

Experimental
A mixture of N-methyl, 2,6-lutidine iodide (0.249 g, 1.0 mmol), benzaldehyde (0.300 g, 2.5 mmol) and pyrrolidine (6 µl) in ethanol (2 ml) was placed in a microwave-ready pressure vial equipped with a stirbar and irradiated in a Biotage microwave initiator for 3 minutes with the temperature set at 130 °C, at a power range of 25-29 W at 5 bar pressure. The cooled reaction mixture was taken out of the initiator, diluted with ethyl acetate, and filtered to afford a crude yellow solid.

Refinement
H atoms were found in difference Fourier maps and subsequently placed in idealized positions with constrained distances of 0.98 Å (RCH 3 ), 0.95 Å (C Ar H), and with U iso (H) values set to either 1.2U eq or 1.5U eq (RCH 3 ) of the attached atom.

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.
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.