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

In the asymmetric unit of the title nicotinonitrile derivative, C23H21BrN2O4, there are two non-planar independent molecules. The central pyridine ring makes dihedral angles of 9.05 (7) and 77.06 (7)°, respectively, with the 4-bromophenyl and 2,4,6-trimethoxyphenyl rings in one molecule, whereas the corresponding values are 5.96 (7) and 82.37 (7)° in the other. All the three methoxy groups are essentially in the plane of the attached benzene ring [C—O—C—C angles = 2.99 (19), 4.8 (2) and −6.2 (2)° in one molecule, and 2.69 (18), 176.73 (15) and 1.3 (2)° in the other]. The ethoxy group is slightly twisted in one molecule [C—C—O—C = 173.84 (12)°], whereas it is coplanar with the pyridine ring in the other [C—C—O—C = −177.23 (13)°]. Weak intramolecular C—H⋯N interactions generate S(5) ring motifs. In the crystal structure, the molecules are linked by weak intermolecular C—H⋯N and C—H⋯O interactions into a supramolecular three-dimensional network in such a way that the nicotinonitrile units of neighboring molecules are stacked in an antiparallel manner along the c axis. The crystal is further stabilized by C—H⋯π interactions.

In the asymmetric unit of the title nicotinonitrile derivative, C 23 H 21 BrN 2 O 4 , there are two non-planar independent molecules. The central pyridine ring makes dihedral angles of 9.05 (7) and 77.06 (7) , respectively, with the 4-bromophenyl and 2,4,6-trimethoxyphenyl rings in one molecule, whereas the corresponding values are 5.96 (7) and 82.37 (7) in the other. All the three methoxy groups are essentially in the plane of the attached benzene ring [C-O-C-C angles = 2.99 (19), 4.8 (2) and À6.2 (2) in one molecule, and 2.69 (18), 176.73 (15) and 1.3 (2) in the other]. The ethoxy group is slightly twisted in one molecule [C-C-O-C = 173.84 (12) ], whereas it is coplanar with the pyridine ring in the other [C-C-O-C = À177.23 (13) ]. Weak intramolecular C-HÁ Á ÁN interactions generate S(5) ring motifs. In the crystal structure, the molecules are linked by weak intermolecular C-HÁ Á ÁN and C-HÁ Á ÁO interactions into a supramolecular threedimensional network in such a way that the nicotinonitrile units of neighboring molecules are stacked in an antiparallel manner along the c axis. The crystal is further stabilized by C-HÁ Á Á interactions.

Comment
The pyridine ring is among the most common heterocyclic compound found in the naturally occurring heterocycles and in various therapeutic agents. The substituted pyridine derivatives have been claimed to have several biological activities (Borgna et al., 1993;Goda et al., 2004) and non-linear optical properties (Raghukumar et al., 2003). The title nicotinonitrile derivative is a compound containing a pyridine ring which was synthesized by cyclization of chalcone derivative (Chantrapromma et al., 2009)  and Shigella sonnei. Our results showed that the title compound has no antibacterial action against these pathogens, having the same results as its starting chalcone derivative (Chantrapromma et al., 2009). Herein we report the crystal structure of the title compound (I).
There are two crystallographic independent molecules A and B in the asymmetric unit of (I) ( Fig. 1) with slight differences in bond angles and in the conformation of the middle methoxy group in 2,4,6-trimethoxyphenyl unit between the two molecules. The molecular structure of (I), C 23 H 21 BrN 2 O 4 is not planar. The central pyridine ring is nearly planar with the 4-bromophenyl ring with the dihedral angles of 9.05 (7)° [5.96 (7)° in molecule B] whereas is inclined to the 2,4,6-trimethoxyphenyl unit with the torsion angle of 77.06 (7)° [82.37 (7)° in molecule B] due to the steric effect between the methoxy and cyano groups. All the three methoxy groups are nearly co-planar to the attached benzene ring with the torsion angles C20-O2-C13-C14 = 2.99 (19)°, C21-O3-C15-C16 = 4.8 (2)° and C22-O4-C17-C16 = -6.2 (2)° in molecule A and the corresponding values are 2.69 (18), 176.73 (15) and 1.3 (2)° in molecule B. However these values show that the middle methoxy group is in different orientation in which it tilts to the methoxy group at C17 in molecule A but tilts to the methoxy group at C13 in molecule B. The ethoxy group in molecule A is slightly twisted with respect to the pyridine ring as indicated by the torsion angles C11-O1-C18-C19 of 173.84 (12)° and N1-C11-O1-C18 = 7.48 (19)° whereas it is co-planar in molecule B as shown by the corresponding values of -177.23 (13) and 0.12 (19)°. Intramolecular C1A-H1AA···N1A and C1B-H1BA-N1B interactions generate S(5) ring motifs (Bernstein et al., 1995). The bond distances agree with the literature values (Allen et al., 1987).
In the crystal structure ( Fig. 2), the molecules are linked by intermolecular C-H···N and C-H···O weak interactions (Table 1) into a supramolecular three-dimensional network in such a way that the nicotinonitrile moiety of the neighbouring molecules are stacked in an antiparallel manner along the c axis. The crystal is further stabilized by C-H···π interactions (Table 1); Cg 1 , Cg 2 and Cg 3 are the centroids of C7A-C11A/N1A, C12A-C17A and C12B-C17B rings, respectively.
Experimental E-1-(4-Bromophenyl)-3-(2,4,6-trimethoxyphenyl)prop-2-en-1-one which was synthesized according to the previous procedure (Chantrapromma et al., 2009) (0.57 g, 0.0015 mol) were added with continuous stirring to a freshly prepared sodium alkoxide (0.0014 mol of sodium in 100 ml of ethanol). Malononitrile (1.30 g, 0.02 mol) was then added with continuous supplementary materials sup-2 stirring at room temperature until the precipitate was separated out. The resulting solid was filtered (yield 72%). Colorless block-shaped single crystals of the title compound suitable for X-ray structure determination were recrystalized from ethanol by the slow evaporation of the solvent at room temperature after several days (m.p. 423-424 K).