6,6′-Oxydichroman

The title compound, C18H18O3, was synthesized from dichroman in concentrated sulfuric acid. The molecule has a twofold axis passing through the central O atom. The dihedral angle between the two symmetry-related benzene rings is 63.6 (3)°. Weak C—H⋯π interactions are present in the structure.

The title compound, C 18 H 18 O 3 , was synthesized from dichroman in concentrated sulfuric acid. The molecule has a twofold axis passing through the central O atom. The dihedral angle between the two symmetry-related benzene rings is 63.6 (3) . Weak C-HÁ Á Á interactions are present in the structure.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BQ2049).

Comment
Synthesized organic compounds with a pyran cycle are found being good biological activities Xiao, Shi et al., 2007;Xiao, Xue et al., 2007;Huang et al., 2007;Zhang et al., 2007;Shi et al., 2007;Cao et al., 2007;Ruan et al., 2006;Li et al., 2006). So we prepared a series of derivatives with pyran cycles. Here we report the crystal structure of the title compound.
The title compound consists of an oxygen atom bridged two chroman (Fig. 1). The molecule has a twofold axis symmetry position at the central O1 atom. The dihedal angle between the two symmetry-related benzene rings is 63.6 (3)°. In each chroman, all the atoms, except C8 atom, are nearly coplanar, with mean deviation from plane by 0.021 (4) Å. C8 atom is located 0.577 (4)Å above the plane defined by other non-hydrogen atoms. All the bond values are within normal ranges (Allen et al., 1987). There exists weak C8-H8B···Cg1 interaction (Cg1:C1-C6) ( Table 1, Fig. 2).

Experimental
Dichroman was disolved in toluene solution and a few drops of concentrated sulfuric acid was added. The above solution was refluxed for two hours. After the solution was cooled to room temperature colorless microcrystals were precipitated.
They were filtered, washed with toluene for three times. Yield: 32%.

Refinement
C-bound H atoms were included in the riding model approximation with C-H = 0.93 Å, and with U iso (H) = 1.2U eq (C). 631 Friedel pairs were averaged before the final refinement as the absolute configuration could not be determined unambiguously. Fig. 1. The molecular structure of (I), showing 30% probability displacement ellipsoids and the atom-numbering scheme. Symmetry code (i): −x, 1 − y, z.  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.