2-(2,4,5-Trimethoxyphenyl)-2,3-dihydroquinolin-4(1H)-one

In the title aza-flavanone, C18H19NO4, an intramolecular cyclization product of chalcone, the central heterocyclic ring is in an envelope conformation and the dihedral angle between the benzene rings is 51.03 (10)°. The methoxy groups at the ortho and para positions are slightly twisted from the benzene ring to which they are bound [C—O—C—C = 21.9 (3) and −171.93 (18)°, respectively], whereas the methoxy group at the meta position is almost coplanar [C—O—C—C = 3.5 (3)°]. In the crystal, molecules are linked by N—H⋯O hydrogen bonds and weak C—H⋯O interactions into chains along the [001] direction. Weak C—H⋯π interactions also occur.

In the title aza-flavanone, C 18 H 19 NO 4 , an intramolecular cyclization product of chalcone, the central heterocyclic ring is in an envelope conformation and the dihedral angle between the benzene rings is 51.03 (10) . The methoxy groups at the ortho and para positions are slightly twisted from the benzene ring to which they are bound [C-O-C-C = 21.9 (3) and À171.93 (18) , respectively], whereas the methoxy group at the meta position is almost coplanar [C-O-C-C = 3.5 (3) ]. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds and weak C-HÁ Á ÁO interactions into chains along the [001] direction. Weak C-HÁ Á Á interactions also occur.

Hoong-Kun Fun Comment
Aza-flavanone or 2-aryl-2,3-dihydroquinolin-4(1H)-one, a synthesized analogue of flavanone, can be achieved by intramolecular cyclization of a chalcone derivative in basic medium (Xia et al., 1998). They are also found to exhibit antibacterial, antifungal (Göker et al., 2005) and anticancer activities (Xia et al., 1998). In the course of our research on medicinal chemistry, we have synthesized the title aza-flavanone (I) in order to study its biological activity.
The total molecule of (I) is twisted (Fig. 1). The dihedral angle between two benzene rings is 51.03 (10) The three methoxy groups of the 2,4,5-trimethoxyphenyl unit have two different orientations: the two methoxy groups at ortho (at atom C11) and para (at atom C13) positions are slightly twisted from the attached benzene ring with torsion angles C16-O2-C11-C12 = 21.9 (3)° and C17-O3-C13-C14 = -171.93 (18)°, whereas the third one at meta (at atom C14) position is co-planar with the torsion angle of C18-O4-C14-C15 = 3.5 (3)°. These angle values also indicated that the methyl group at para position points towards the ortho-methoxy but points away from the meta-methoxy due to the steric effect.
In the crystal (Fig. 2), the molecules are linked by N-H···O hydrogen bonds and weak C-H···O interactions (Table 1) into chains along the c axis. C-H···π interactions (Table 1) also occur.

Experimental
To a 50 ml round-bottom flask filled with 2,4,5-trimethoxybenzaldehyde (0.50 g, 2.55 mmol), EtOH (20 ml) and 2aminoacetophenone (0.31 ml, 2.55 mmol) were sequentially added at room temperature. After stirring for a while, 5 ml of 30% NaOH (aq) was added slowly and was then further stirred for 2 h. A pale yellow precipitate was formed and collected by filtration yielding the title compound (I) (1.26 g, 75% yield), which was further recrystallized in EtOH to obtain yellow needles of (I) after several days, m.p. 419-420 K.

Refinement
Amide H atom was located in a Fourier difference map and refined isotropically. The remaining H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H = 0.95 Å for aromatic, 1.00 for CH, 0.99 Å for CH 2 and 0.98 Å for CH 3 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. program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids.