3-(4-Methylphenyl)-4H-chromen-4-one

In the title compound, the dihedral angle formed between the plane of the chromenone ring system (r.m.s. deviation = 0.031 Å) and the pendant benzene ring is 31.09 (5)°. In the crystal, weak C—H⋯O hydrogen bonds link the molecules into C(6) chains propagating along the a-axis direction.


Structure description
Isoflavones are flavonoid polyphenols with a general C6-C3-C6 carbon-atom skeleton. Since isoflavones have a substituent at the 2-position of the flavonoid skeleton, they exhibit structural differences from other compounds belonging to flavonoids having a substituent at the 3-position. Isoflavones are sometimes classified as phytoestrogens, and they also exhibit different physiological functions from other flavonoids (Tikkanen et al., 2000). Recent research has shown that isoflavones have broad biological activities with resspect to osteoporosis (Ye et al., 2006), anticancer activity (Messina et al., 2009), cardiovascular diseases (Zhan et al., 2005) and the inhibition of thyroid peroxidase (Chang et al., 2000). As part of our ongoing studies of isoflavones , the title compound was synthesized and its crystal structure was determined.
The molecular structure of the title compound, C 16 H 12 O 2 , is shown in Fig. 1. The chromenone ring system (C1-C9/O2) is slightly twisted from planarity, with a maximum deviation of 0.059 Å at C2 (root-mean-square deviation = 0.031 Å ). The dihedral angle formed between the mean plane of the chromenone ring system and the pendant benzene (C10-C15) ring is 31.09 (5) . In the crystal, weak C-HÁ Á ÁO hydrogen bonds link the molecules into C(6) chains propagating along the a-axis direction (Table 1, Fig. 2).

Synthesis and crystallization
The title compound was synthesized in three steps from the commercially available starting materials 2-hydoxyacetophenone and 4-methylbenzaldehyde according to the data reports reaction scheme shown in Fig. 3. To a solution of 2-hydoxyacetophenone (408 mg, 3 mmol) in 40 ml of ethanol was added 4-methylbenzaldehyde (360 mg, 3 mmol) and the temperature was adjusted to around 277 K in an ice-bath. To the cooled reaction mixture were added 4 ml of 30% aqueous KOH solution and the reaction mixture was stirred at room temperature for 3 h. This mixture was poured into iced water (100 ml) and was acidified (pH = 2) with 2 M HCl solution to give a precipitate. Filtration and washing with water afforded crude solid of chalcone compound (I). To a solution of I (1.5 mmol, 357 mg) in 20 ml aqueous ethanol (H 2 O:ethanol = 1:2) was added excess sodium acetate and the solution was refluxed at 362 K for 2 h. The reaction mixture was cooled to room temperature and was poured into iced water (50 ml) to give a precipitate of the flavanone compound II. Compound II (163 mg, 0.5 mmol) was dissolved in 15 ml of methanol and the temperature was adjusted to around 327 K. To the clear solution were added catalytic amount of p-toluene sulfonic acid and 1.2eq of thallium(III) nitrate trihydrate and the mixture was refluxed for 5 h. The reaction mixture was cooled to room temperature and the resulting precipitate was filtered and washed with water. This solid was recrystallized from an ethanol solution to obtain single crystals of the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

Figure 2
Part of the crystal structure of the title compound with C-HÁ Á ÁO hydrogen bonds shown as dashed lines.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.

data-1
IUCrData ( Special details 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.