2,2′-[(1E)-3-Phenylprop-2-ene-1,1-diyl]bis(3-hydroxy-5,5-dimethylcyclohex-2-en-1-one)

In the title molecule, C25H30O4, the two cyclohexene rings adopt envelope conformations. The two hydroxy groups are involved in the formation of intramolecular O—H⋯O hydrogen bonds. In the crystal structure, weak intermolecular C—H⋯O hydrogen bonds link molecules related by translation along the axis a into chains.

In the title molecule, C 25 H 30 O 4 , the two cyclohexene rings adopt envelope conformations. The two hydroxy groups are involved in the formation of intramolecular O-HÁ Á ÁO hydrogen bonds. In the crystal structure, weak intermolecular C-HÁ Á ÁO hydrogen bonds link molecules related by translation along the axis a into chains.   Table 1 Hydrogen-bond geometry (Å , ).  In (I) (Fig. 1), the bond lengths and angles are normal and correspond to those observed in related structures (Bolte et al., 2001;Palakshi Reddy et al., 2010;Shi et al., 1998). Two six-membered cyclohexene rings adopt an envelope conformation.
In the crystal structure, weak intermolecular C-H···O hydrogen bonds (Table 1) link the molecules related by translation along axis a into chains.

Experimental
The title compound has been synthesized following the known procedures (Ramachary & Mamillapalli, 2007;Rohr & Mahrwald, 2009). A mixture of cinnamaldehyde (0.66 g, 5 mmol), 5,5-dimethyl-1,3-cyclohexanedione (1.40 g, 10 mmol), and palladium (II) chloride (0.0010 g) was refluxed in acetonitrile (10 ml) at 353 K for 6 h (Fig. 2). After being cooled to room temperature, the reaction mixture was poured into water. The white precipitate was filtered off with a silica pad, washed twice with water, and the filtrate was then dried under vacuum to yield the product in yield of 82%. Single crystals of the title compound were obtained by slow evaporation from ethanol at room temperature to yield colourless, block-shaped crystals.

Refinement
The H atoms were positioned geometrically (C-H 0.93-0.98 Å, O-H 0.82 Å) and allowed to ride on their parent atoms, with U iso = 1.2 or 1.5U eq (parent atom). Fig. 1. View of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Special details
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.