6-(4-Bromophenyl)-2-ethoxy-4-(2,4,5-trimethoxyphenyl)nicotinonitrile

There are two molecules in the asymmetric unit of the title compound, C23H21BrN2O4, which differ in the conformation of their ethoxy residues, i.e. almost co-planar with the pyridine ring in one molecule [C—O—C—C = −174.0 (2)°] but almost perpendicular in the other [C—O—C—C = 92.8 (3)°]. The dihedral angles between the central pyridine ring and the 4-bromophenyl and 2,4,5-trimethoxyphenyl rings are 11.05 (12) and 63.78 (12)°, respectively, in one molecule; the corresponding angles in the other molecule are 30.38 (13) and 65.38 (13)°, respectively. In the crystal structure, pairs of molecules are arranged in a face-to-face sandwich structure which further stacks along the b axis. The crystal packing features C—H⋯π interactions and Br⋯O [3.5417 (17) Å], Br⋯C [3.748 (3) Å], C⋯N [3.376 (4) Å] and C⋯O [3.351 (3)–3.409 (3) Å] contacts. Finally, π⋯π interactions [centroid⋯centroid distances = 3.6346 (19) and 3.6882 (19) Å] are observed.

There are two molecules in the asymmetric unit of the title compound, C 23 H 21 BrN 2 O 4 , which differ in the conformation of their ethoxy residues, i.e. almost co-planar with the pyridine ring in one molecule [C-O-C-C = À174.0 (2) ] but almost perpendicular in the other [C-O-C-C = 92.8 (3) ]. The dihedral angles between the central pyridine ring and the 4-bromophenyl and 2,4,5-trimethoxyphenyl rings are 11.05 (12) and 63.78 (12) , respectively, in one molecule; the corresponding angles in the other molecule are 30.38 (13) and 65.38 (13) , respectively. In the crystal structure, pairs of molecules are arranged in a face-to-face sandwich structure which further stacks along the b axis. The crystal packing features C-HÁ Á Á interactions and BrÁ Á ÁO [3.5417 (17)

Experimental
(E)-1-(4-Bromophenyl)-3-(2,4,5-trimethoxyphenyl)prop-2-en-1-one (0.57 g, 0.0015 mol) was added with continuous stirring to a freshly prepared sodium alkoxide solution (0.0014 mol of sodium in 100 ml of ethanol). Malononitrile (1.3 g, 0.02 mol) was then added with continuous stirring at room temperature until the precipitate separated out. The resulting solid was filtered (yield 68 %). Colorless needle-shaped single crystals of the title compound were obtained by recrystallization from ethanol by the slow evaporation of the solvent at room temperature after several days, Mp. 460-461 K.
supplementary materials sup-2 Refinement All H atoms were positioned geometrically and allowed to ride on their parent atoms, with d(C-H) = 0.93 Å for aromatic-H, 0.97 for CH 2 and 0.96 Å for methyl-H atoms. The U iso values were constrained to be 1.5U eq of the carrier atom for methyl-H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups.

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 100.0 (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 > σ(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.