(2E)-1-(Pyridin-2-yl)-3-(2,4,6-trimethoxyphenyl)prop-2-en-1-one

The title heteroaryl chalcone derivative, C17H17NO4, is a condensation product of 2-acetylpyridine and 2,4,6-trimethoxybenzaldehyde. The molecule is roughly planar, the dihedral angle between the pyridine and benzene rings being 5.51 (10)°. All the three methoxy groups are almost co-planar with the bound benzene ring [r.m.s. deviation of 0.0306 (2) Å]. A weak C—H⋯O intramolecular interaction involving one of the ortho-methoxy groups generates an S(6) ring motif. In the crystal, the molecules are linked by weak C—H⋯O interactions into anti-parallel face-to-face pairs. Adjacent pairs are further connected into sheets parallel to the ab plane.


Comment
Chalcones and heteroaryl chalcones have drawn a lot of interests due to their wide range of biological properties including antioxidant (Gacche et al., 2008), antibacterial (Go et al., 2005;Isomoto et al., 2005), anti-inflammatory and anticancer (Bandgar et al., 2010) as well as HIV-1 protease inhibitory (Tewtrakul et al., 2003) activities. Furthermore they also exhibit fluorescent property (Jung et al., 2008;Suwunwong et al., 2011). In our on-going research on the biological and fluorescent properties of chalcones and heteroaryl chalcones (Chantrapromma et al., 2009;Fun et al., 2010Fun et al., , 2011Suwunwong et al., 2011), the title heteroaryl chalcone derivative (I) was synthesized in order to study the effects of substituted postions on the fluorescent property in comparision with the closely related compounds Suwunwong et al., 2011). In addition (I) was also tested for analgesic and antibacterial activities. Our results showed that (I) exhibits a moderate analgesic activity but is inactive for antibacterial activity. Herein we report the crystal structure of (I).
The molecule of the title heteroaryl chalcone derivative (  (Table 1) generates an S(6) ring motif (Bernstein et al., 1995). The bond distances are of normal values (Allen et al., 1987) and comparable with related structures (Chantrapromma et al., 2009;Fun et al., 2010;. In the crystal packing ( Fig. 2), only the two ortho-methoxy groups are involved in weak C-H···O interactions ( Table  1). The adjacent molecules are linked by weak C17-H17B···O4 interaction (Table 1) into anti-parallel face-to-face pairs.
The adjacent pairs were further connected by weak C3-H3A···O2 interactions (Table 1) into sheets parallel to the ab plane which are stacked down the c axis. The crystal may be further stabilized by C···O [3.203 (2) Å] short contacts.

Experimental
The title compound was synthesized by the condensation reaction of 2,4,6-trimethoxybenzaldehyde (0.40 g, 2 mmol) with 2-acetylpyridine (0.20 g, 2 mmol) in ethanol (30 ml) in the presence of 30% NaOH(aq) (5 ml). After stirring in ice bath at 278 K for 4 h, the resulting pale yellow solid appeared and was then collected by filtration, washed with distilled water, dried and purified by repeated recrystallization from acetone. Pale yellow plate-shaped single crystals of the title compound suitable for X-ray structure determination were recrystalized from acetone/ethanol (1:1 v/v) by the evaporation of the solvent at room temperature after several days, M.p. 392-393 K.
supplementary materials sup-2 Refinement All H atoms were located in difference maps and refined isotropically. A total of 1754 Friedel pairs were merged before final refinement as there is no large anomalous dispersion for the determination of the absolute structure. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids. A weak intramolecular C-H···O interaction is shown as a dashed line. 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 > 2sigma(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.