2-[2-(Trifluoromethyl)phenyl]-2H-1-benzopyran-4(3H)-one

In the title compound, C16H11F3O2, the γ-pyranone ring adopts an envelope conformation with the chiral C atom standing out of the ring plane. In the crystal, molecules are linked by C—H⋯O and C—H⋯F interactions.

In the title compound, C 16 H 11 F 3 O 2 , the -pyranone ring adopts an envelope conformation with the chiral C atom standing out of the ring plane. In the crystal, molecules are linked by C-HÁ Á ÁO and C-HÁ Á ÁF interactions.  Table 1 Hydrogen-bond geometry (Å , ). The title compound belongs to the group of flavanones which occur predominantly in citrus fruits. Citrus flavonoids were reported (Benavente-García & Castillo, 2008) as having antimicrobial, antifungal, antiviral, anti-allergenic, antiinflammatory (Harborne & Williams, 2000 and antioxidant (Rodeiro et al., 2006) properties. Case control studies suggest that flavonoids may reduce the risk of cardiovascular disease and stroke. Considering the wide spectrum of activities of natural flavonoids further structure modification of these molecules is aimed to enhance their interaction with the target sites in cells.

Related literature
The title compound adopts a typical conformation of flavanones with the γ-pyranone ring adopting the envelope conformation. In this conformation the carbon atoms C1, C6, C7, C8 and oxygen O1 are nearly coplanar with a root mean square deviation from the mean plane of 0.035 Å, while the C9 carbon atom is standing out from this plane with an atom-to-plane distance of 0.652 (6) Å. All bond lengths and angles in the title compound show usual values for this type of compounds (Wera et al., 2012;Białońska et al., 2007;Krishnaiah et al., 2005;Wu et al., 2005). In this crystal packing of the title compound there are 4 intramolecular, 2 intermolecular (C-H···O and C-H···F) and one π-π interaction. All of the fluoride atoms participate in weak intramolecular C-H···F interactions ( Fig. 1) with H···F distances equal or shorter than 2.50 Å, which is shorter than the sum of their Van der Waals radii (Bondi, 1964). Two of the fluoride atoms interact with the hydrogen atom connected to the chiral carbon atom C9 while the third fluoride atom interacts with one of the phenyl hydrogen atoms (Table 1). The dihedral angle between Cg1 and Cg2 rings in previously published structures of flavanones (Wera et al., 2012;Białońska et al., 2007;Krishnaiah et al., 2005;Wu et al., 2005) is in the range from 55 to 75° while the corresponding dihedral angle in the case of the title compound is 66.06 (15)°.
The flavanone molecules are connected into rows by the C3-H3···O2 intermolecular interaction forming chains down the crystallographic a axis (Fig. 2). The second intermolecular interaction, C5-H5···F3, connects the molecules into another chain in the direction of the screw axis following the crystallographic c axis, thus forming a two dimensional net of molecules (Fig. 3). Strings of molecules along the crystallographic c axis are further connected by π-π interactions ( Fig. 4). Perpendicular distance from the centroid of one Cg1 ring, molecule at (x, y, z), to the plane of the second Cg1 ring, molecule at (1 -x, 2 -y, 1/2 + z), and vice versa are 3.70 and 3.62 Å respectively, while the distance between the ring centroids measures 4.101 (3) Å. The Cg1 ring planes of molecules at (x, y, z) and (1 -x, 2 -y, 1/2 + z) are nearly parallel with the dihedral angle being 5.59 (3)°.

Experimental
The proposed compound was prepared in two steps. The first step in the synthetic route consisted of the condensation of 2-hydroxy acetophenone with 2-trifluoromethylbenzaldehyde to give an α,β-unsaturated ketone (chalcone). In the second step the obtained chalcone was dissolved under stirring in a 50:50 water/ethanol mixture. The pH was set to 9.0 with 0.1 M NaOH and the reaction mixture was refluxed for 2 h after which it was cooled over night to room temperature. Small crystals of the title compound formed in the reaction vessel and, after draining excess fluid, the crystals were dried at room temperature.

Refinement
The H atoms bonded to C atoms were placed at geometrically calculated positions and refined using a riding model. C-H distances were fixed to 0.93 Å for aromatic C atoms, 0.97 Å for the secondary CH 2 group and 0.98 Å for the tertiary CH group. Their U iso (H) values were equal to 1.2 times U eq of the corresponding C atom.
In the absence of significant anomalous scattering, the absolute configuration could not be reliably determined so the Friedel pairs were merged and any references to the Flack parameter were removed.      π-π interactions of two neighbouring Cg1 rings. Symmetry code: (i) 1 -x, 2 -y, 1/2 + z. Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq O1 0.3661 (