3,4-Dihydro-1H-benzo[c]chromene-1,6(2H)-dione

In the title compound, C13H10O3, the pyranone and benzene rings are almost coplanar, making a dihedral angle of 1.9 (1)°. The cyclohexenone ring adopts an envelope conformation, with a methylene C atom located at the flap and displaced by 0.639 (3) Å from the mean plane of the other five atoms. In the crystal, pairs of weak C—H⋯π interactions occur between inversion-related molecules.

In the title compound, C 13 H 10 O 3 , the pyranone and benzene rings are almost coplanar, making a dihedral angle of 1.9 (1) . The cyclohexenone ring adopts an envelope conformation, with a methylene C atom located at the flap and displaced by 0.639 (3) Å from the mean plane of the other five atoms. In the crystal, pairs of weak C-HÁ Á Á interactions occur between inversion-related molecules.

Experimental
Cg is the centroid of the C1-C6 benzene ring.
As part of our research (Fan et al. 2012), we have synthesized the title compound (I), and report its crystal structure here.
The title compound, C 13 H 10 O 3 , consists of three fused six-membered rings, benzene, pyranone and cyclohexenone ring.
The pyranone ring is in the middle. All the bond lengths and bond angles are within normal ranges. The pyranone ring and the benzene ring are almost coplanar with a dihedral angle of 1.9 (1) °. The cyclohexenone ring adopts an envelope conformation, a methylene C atom located on the flap and displaced from the mean plane of the other five ring atoms (C8 In the crystal, weak intermolecular C-H···π interactions occur between benzene ring and methylene group of adjacent molecules, the separation between the centroid of benzene ring and methylene H atom being 2.91 Å.

Experimental
The title compound was synthesized following the previously reported procedure (Fan et al., 2012). Single crystals, suitable for X-ray diffraction analysis, were obtained by slow evaporation of the solvents from a petroleum ether-ethyl acetate (5:1 v/v) solution of the title compound.

Refinement
H atoms were positioned geometrically and refined using riding model with C-H = 0.93-0.97 Å and U iso (H) = 1.2U eq (C).

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.