2-Phenyl-2,3-dihydrophenanthro[9,10-b][1,4]dioxine

In the title compound, C22H16O2, the phenanthrene ring system is essentially planar [maximum deviation = 0.058 (1) Å] and is inclined at an angle of 58.39 (6)° to the phenyl ring. The 1,4-dioxane ring is in a chair conformation. In the crystal, molecules are stacked along the b axis, but no significant hydrogen bonds are observed.


Comment
Phenanthrene is a major structural component of many natural products that play important roles in pharmaceutical and biological fields. For example, phenanthrene-based tylophorine derivatives could serve as potential antiviral agents against the tobacco mosaic virus in vitro (Wang et al., 2010). In addition, phenanthrene-based alkaloids are found to possess antitumor activities (Li & Wang, 2009) and other important bioactivities. Gao & Wong reported that phenanthrene has important effect on rice cultivation by degrading the bacterium affecting the rice plants (Gao & Wong, 2010). In a phenanthrene-contaminated soil, the activity of urease and catalase may be decreased while polyphenol oxidase was stimulated (Zhan & Jiang, 2010).
The importance of 9,10-disubstituted phenanthrene in biochemistry also has been reported. Phenanthrene 9,10-dihydrodiol could be used as a biomarker for ETS-exposure of children and the derivatives of pyrrolo(9, 10b)-phenanthrene were good templates for DNA intercalating drug delivery system (Becker & Dettbarn, 2009;Jones & Mathews, 1997). Due to the importance of the 9, 10-disubstituted phenanthrene derivatives, herewith, we report the crystal structure of the title compound.
The title compound ( Fig. 1) is made up of a phenanthrene (C9-C22) ring system, a phenyl (C1-C6) ring and a 1,4-dioxane (O1/O2/C7-C9/C22) ring. The phenanthrene ring system is essentially planar, with a maximum deviation of 0.058 (1) Å at atom C21, and is inclined at an angle of 58.39 (6) ° with the phenyl ring. The 1,4-dioxane ring is in chair conformation,  et al., 1987) and angles are within normal ranges. In the crystal (Fig.2), molecules are stacked along the b-axis but no significant hydrogen bonds are observed.

Experimental
The title compound is a product of the photoreaction between phenanthrenequinone and styrene. The compound was purified by flash column chromatography with ethyl acetate/petroleum ether (1:10) as eluents. Good quality crystals of the title compound were obtained from slow evaporation of an acetone and petroleum ether solution (1:10).

Refinement
All H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 -0.98 Å and U iso (H) = 1.2 U eq (C). The highest residual electron density peak is located at 0.74 Å from H1A and the deepest hole is located at 1.33 Å from C14.

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.
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 > 2sigma(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.