(E)-1-(Pyridin-2-yl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one

In the title heteroaryl chalcone derivative, C17H17NO4, the dihedral angle between the pyridine and benzene rings is 10.82 (5)°. The two methoxy groups at the meta positions are essentially coplanar with the attached benzene rings [C—O—C—C torsion angles = −0.97 (14) and 179.47 (9)°], whereas the methoxy group at the para position is twisted from the attached ring with a C—O—C—C torsion angle of −104.48 (11)°. A C—H⋯O close contact involving two of the methoxy groups generates an S(6) ring motif. In the crystal, molecules are linked by weak C—H⋯O interactions into columns along the b axis.

In the title heteroaryl chalcone derivative, C 17 H 17 NO 4 , the dihedral angle between the pyridine and benzene rings is 10.82 (5) . The two methoxy groups at the meta positions are essentially coplanar with the attached benzene rings [C-O-C-C torsion angles = À0.97 (14) and 179.47 (9) ], whereas the methoxy group at the para position is twisted from the attached ring with a C-O-C-C torsion angle of À104.48 (11) . A C-HÁ Á ÁO close contact involving two of the methoxy groups generates an S(6) ring motif. In the crystal, molecules are linked by weak C-HÁ Á ÁO interactions into columns along the b axis.
In the crystal (Fig. 2), the molecules are linked by weak intemolecular C16-H16B···O3 i interactions (Table 1) into columns along the b axis.

Experimental
The title compound was synthesized by the condensation of 3,4,5-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 3 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 block-shaped single crystals of the title compound suitable for x-ray structure determination were recrystalized from acetone/ethanol (1:1 v/v) by the slow evaporation of the solvent at room temperature after four days, Mp. 434-435 K.

Refinement
All H atoms were placed in calculated positions, with C-H = 0.93 Å, U iso = 1.2U eq (C) for aromatic and CH and C-H = 0.96 Å, U iso = 1.5U eq (C) for CH 3 atoms. A rotating group model was used for the methyl groups. The highest residual electron density peak is located at 0.12 Å from C4 and the deepest hole is located at 0.28 Å from N1. A total of 2730 supplementary materials sup-2 Friedel pairs were merged before final refinement as there is no significant anomalous dispersion for the determination of the absolute structure.
Figures Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. The dashed line indicates a weak intramolecular hydrogen bond.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 120.0 (1) K.
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 > 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.