7-Bromo-9-(2-hydroxy-4,4-dimethyl-6-oxocyclohex-1-en-1-yl)-3,3-dimethyl-2,3,4,9-tetrahydro-1H-xanthen-1-one

In the xanthene ring system of the title compound, C23H25BrO4, the 4H-pyran ring is almost planar [maximum deviation = 0.040 (3) Å] and the cyclohexene ring adopts a sofa conformation. The cyclohexene ring attached to the xanthene system is puckered [Q T = 0.427 (3) Å, θ = 55.0 (4) ° and ϕ = 164.4 (6) °]. In the crystal, molecules are linked to each other by O—H⋯O and C—H⋯O hydrogen bonds.

Following to our recent study (Mohamed et al. 2012) on synthesis and structure characterization of tetrahydro xanthenones for biological investigation, herein we report the synthesis and crystal structure of the title compound.
The crystal structure is stabilized by intermolecular O-H···O and C-H···O hydrogen bonds (Table 1 and Fig. 2).

Experimental
The title compound (I) has been prepared from reaction of 1 mmol (201 mg) 5-bromo-2-hydroxybenzaldehyde with 1 mmol (140 mg) dimedone in presence of either (4-aminophenyl)methanol or TRIZMA (tris(hydroxymethyl)aminomethane) as a catalyst in 50 ml e thanol at 351 K. The reaction was monitored by TLC till completion after 4 h then left to cool at ambient temperature. The reaction mixture was concentrated under vacuum and the solid formed product was collected and dried using Buckner funnel then recrystallized from ethanol (82% yield; m.p. 521 K). Pure crystals suitable for X-ray structure analysis were obtained by slow evaporation method using ethanol as a solvent.

Refinement
The hydroxyl H atom was located from a difference Fourier map and refined with a distance restraint of O-H 0.82±0.02.

Figure 1
View of the title molecule with the atom numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 30% probability level.   Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.