Crystal structure of 3-hydroxy-2-(4-hydroxy-3-methoxyphenylmethyl)-5,5-dimethylcyclohex-2-enone

In the title dimedone derivative, the 4-hydroxy-3-methoxybenzyl substituent adopts a sofa conformation. In the crystal, molecules are assembled into a sheet structure parallel to the ab plane via O—H⋯O hydrogen bonds.

In the title compound, C 16 H 20 O 4 , a new starting compound for the synthesis of various heterocycles, the partially saturated six-membered ring adopts a sofa conformation. An intramolecular O-HÁ Á ÁO hydrogen bond is observed in the guaiacol residue. In the crystal, molecules are assembled into a sheet structure parallel to the ab plane via O-HÁ Á ÁO hydrogen bonds. The hydrogen-bond pattern is described by an R 4 4 (28) graph-set motif. The sheets are further linked by C-HÁ Á ÁO hydrogen bonds into a three-dimensional network.

Supramolecular features
In the crystal, the molecules are assembled into a sheet structure parallel to the ab plane via O-HÁ Á ÁO hydrogen bonds ( Table 1). The hydrogen-bonding pattern in the sheet is described by an R 4 4 (28) graph-set motif (Fig. 2). Furthermore, weak C-HÁ Á ÁO hydrogen bonds join the sheets into a threedimensional network (Table 1).

Figure 2
A packing diagram of the title compound, viewed along the c axis. O-HÁ Á ÁO hydrogen bonds are shown as dashed lines. For clarity weak C-HÁ Á ÁO bonds are not depicted.

Figure 1
The molecular structure of the title compound, with the atom-numbering scheme and 50% probability displacement ellipsoids.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms bonded to O atoms were refined freely. Other H atoms were included in the refinement at geometrically calculated positions with C-H = 0.93-0.97 Å and treated as riding with U iso (H) = 1.2U eq (C) or 1.5U eq (C-methyl). Reaction scheme for the title compound (1a) and its tautomer (1 b).  Data collection: COLLECT (Bruker, 2001); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction:

3-Hydroxy-2-(4-hydroxy-3-methoxyphenylmethyl)-5,5-dimethylcyclohex-2-enone
Crystal data 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.