9-(2-Chlorophenyl)-4a-hydroxy-3,4,4a,5,6,7,9,9a-octahydro-2H-xanthene-1,8-dione

In the title compound, C19H19ClO4, the dihydropyran ring and the cyclohexane ring adopt a half-chair conformation and a chair conformation, respectively. The cyclohexene ring has an envelope conformation with the central CH2 C atom as the flap. This atom is disordered over two positions [site-occupancy ratio = 0.744 (12):0.256 (12)] above and below the mean plane formed by the other five atoms. In the crystal, O—H⋯O hydrogen bonds between hydroxy and carbonyl groups link molecules into chains propagating along [001].

In the title compound, C 19 H 19 ClO 4 , the dihydropyran ring and the cyclohexane ring adopt a half-chair conformation and a chair conformation, respectively. The cyclohexene ring has an envelope conformation with the central CH 2 C atom as the flap. This atom is disordered over two positions [siteoccupancy ratio = 0.744 (12):0.256 (12)] above and below the mean plane formed by the other five atoms. In the crystal, O-HÁ Á ÁO hydrogen bonds between hydroxy and carbonyl groups link molecules into chains propagating along [001].
In the main structure of this compound (Figure 1), there exist central dihydropyran ring (O1/C5/C6/C7/C8/C13) adopts a half-chair conformations while the cyclohexane ring adopts a chair conformation. The cyclohexene ring displays an approximate envelope conformation, and in the crystal this ring is disordered over two positions in an occupancy ratio of 0.744 (12):0.256 (12) with the flap atom located on the opposite sides of the mean plane formed by other five atoms. The bond lengths and angles are comparable to those in a related structure (Hua et al., 2006;Yang et al., 2011). The crystal packing is stabilized by intermolecular O-H···O hydrogen bond between hydroxyl and carbonyl groups, which links the molecules into supramolecular chains running along the c-axis direction.
The white precipitate was vacuum filtered and washed with methanol. And Then dried under vacuum to yield the white solid (6.1 g, 88% yield).
Single crystals of the title compound suitable for X-ray structure determination were obtained by slow evaporation from mixture solution of anhydrous ethanol and dichloromethane (v: v = 1:1) at room temperature to yield colorless, blockshaped crystal.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (