1-(4-Methoxyphenyl)ethane-1,2-diyl 1,1′-biphenyl-2,2′-dicarboxylate

In the title molecule, C23H18O5, the methoxy-substituted benzene ring makes dihedral angles of 65.12 (4) and 88.55 (4)° with the other two benzene rings. These two benzene rings form a dihedral angle of 45.70 (4)°. In the crystal, molecules are linked into inversion dimers by pairs of weak C—H⋯O hydrogen bonds.

In the title molecule, C 23 H 18 O 5 , the methoxy-substituted benzene ring makes dihedral angles of 65.12 (4) and 88.55 (4) with the other two benzene rings. These two benzene rings form a dihedral angle of 45.70 (4) . In the crystal, molecules are linked into inversion dimers by pairs of weak C-HÁ Á ÁO hydrogen bonds.

Hoong-Kun Fun, Ching Kheng Quah and Dongdong Wu Comment
The title compound belongs to the biphenyl-containing bislactone family whose preparation could be achieved through a concise photochemical method (Wu et al., 2012). In the title compound, Fig. 1, the methoxy attached phenyl ring (C17-C22) inclines at dihedral angles of 65.12 (4) and 88.55 (4)° with the two benzene rings (C2-C7 and C8-C13), respectively. The two benzene rings form a dihedral angle of 45.70 (4)°. Bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable to a related structure (Fun et al., 2012). In the crystal (Fig. 2), molecules are linked into inversion dimers by pairs of intermolecular C16-H16A···O3 hydrogen bonds (Table 1).

Experimental
The title compound was the major diastereoisomer of the sequential photoreaction products of 9,10-phenanthrenedione with 1-methoxy-4-vinylbenzene. The compound was purified by flash column chromatography with ethyl acetate/petroleum ether (1:9) as eluents. X-ray 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 or 1.5U eq (C). A rotating-group model was applied for the methyl group.  The molecular structure of the title compound, showing 50% probability displacement ellipsoids for non-H atoms.

Figure 2
The crystal structure of the title compound, viewed along the b axis. H atoms not involved in hydrogen bonds (dashed lines) have been omitted for clarity.   (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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.