5,6-Dimethyl-4-phenyl-2H-pyran-2-one

In the title compound, C13H12O2, the dihedral angle between the pyranone and phenyl rings is 57.55 (9)°. In the crystal, the molecules are linked by π–π stacking interactions between the parallel pyranone rings of neighboring molecules with distances of 3.5778 (11) Å and 3.3871 (11) Å between the planes. C—H⋯O interactions also occur.

In the title compound ( Fig. 1), all the bond lengths and bond angles are within normal ranges. All the atoms connected with the pyranone ring are in the pyranone plane with a maximal deviation of 0.052 (2) Å for substituent C12. The dihedral angle between the pyranone ring and the phenyl ring is 57.55 (9)°.

Experimental
To a flask containing methyl 3-hydroxy-4-methyl-3-phenylhexa-4,5-dienoate (1 mmol) were added CH 2 Cl 2 (5 ml) and conc. H 2 SO 4 (0.1 mmol). The solution was stirred at room temperature until completion as monitored by TLC. The reaction was quenched with aqueous NaHCO 3 , and then extracted with ethyl acetate (5 ml × 3). The combined organic phases were dried, filtered and concentrated under vacuum. The residue was purified by column chromatography on silica gel eluenting with petroleum ether-ethyl acetate (10:1 v/v) to give the title compound as colorless solids with a yield of 90%. Single crystals, suitable for X-ray diffraction analysis, were obtained by slow evaporation of solvent from a petroleum ether-dichloromethane (3:1 v/v) solution.

Refinement
The H atoms were included at calculated positions and were refined as riding atoms: C-H = 0.93 and 0.96 Å for aromatic and methyl H atoms, respectively, with U iso (H) =x×U eq (C), where x = 1.5 for methyl H, and x = 1.2 for aromatic H atoms.

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

Figure 2
Crystal packing of the title compound, viewed along the b axis. Intermolecular C-H···O hydrogen bonds are shown as dashed lines, only H atoms involved in hydrogen bonds are shown. π-π stacking interactions between the parallel pyranone rings of neighboring molecules are observed. 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 Rfactors based on ALL data will be even larger.