5,7-Bis(benzyloxy)-2-[4-(benzyloxy)phenyl]-4H-chromen-4-one

In the title compound, C36H28O5, the terminal benzene rings are twisted at dihedral angles of 6.75 (12), 70.86 (14) and 82.02 (12)° with the respect to the central plana r[maximum deviation = 0.070 (3) Å] chromen-4-one ring system. In the crystal structure, π–π stacking is observed between parallel benzene rings of adjacent molecules [centroid–centroid distance = 3.7459 (16) Å].


S1. Comment
Flavones are among the most ubiquitous groups of polyphenolic compounds in foods of plant origin. As integral constituents of the diet, they may exert a wide range of beneficial effects on human health, including protection against cardiovascular disease, certain forms of cancer (Formica & Regelson 1995) and modulatory activities at GABA-A receptors (Medina et al., 1998). Flavones likely produce such biological effects through their free radical-scavenging antioxidative activities and metal ion-chelating a bilities (Cotelle et al.1992). Some flavones are more potent than ascorbic acid and tocopherols in scavenging reactive oxygen species. The title compound was crystallized as part of an ongoing structure-activity study to determine the properties of those compounds that confer this activity in order to aid the design of more active compounds.
The molecular is shown in shown in Fig. 1, the bond lengths and angles are within normal ranges. The bond length of the carbonyl group C7=O2 of 1.228 Å is somewhat longer than typical carbonyl bond. This may be due to the fact that atom O2 participate in intermolecular Van der Waals forces. And the bond lengths of C1-O3, C3-O4 and C27-O5 are 1.353 Å, 1.369 Å and 1.375 Å, respectively. In the crystal structure π-π stacking is observed between parallel C24benzene and C24 i -benzene rings of adjacent molecules [centroids distance 3.7459 (16) Å; symmetry code: (i) 2-x, 1-y, 2z].

S2. Experimental
E-3-(4-Phenoxyphenyl)-1-(2,4-bisphenoxy-6-hydroxyphenyl) propenone (2 g, 3.40 mmol) was dissolved in DMSO (40 ml). I 2 (96 mg, 0.377 mmol) was added to the solution. The reaction mixture was heated at 400 K for 2 h under N 2 , then coolded to room temperature. The mixture was pured to 200 ml 1M HCl solution. The aqueous layer was extracted with ethyl acetate. The organic layer was washed with NaHCO 3 solution, watre and brine, and dried by MgSO 4 and concentrated under diminished pressure. The residue was purified by flash chromatography on a silica gel column (elutant: hexanesethyl /acetate, 4:1). Single crystals suitable for X-ray diffraction were obtained by solw evaporation of a dilute solution of the title compound in methanol/dichloromethane (1:5).

S3. Refinement
The H atoms were placed in calculated positions and refined in riding mode with U iso (H) = 1.2U eq (C).  The structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme.

5,7-Bis(benzyloxy)-2-[4-(benzyloxy)phenyl]-4H-chromen-4-one
where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.13 e Å −3 Δρ min = −0.14 e Å −3 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.