1-(3-p-Tolylisoxazol-5-yl)cyclohexanol

The title compound, C16H19NO2, contains two molecules in the asymmetric unit. Each molecule is composed of three interconnected rings, two essentially planar rings, viz. the isoxazole and the methylbenzyl aromatic ring [maximum deviations of 0.0027 (13) and 0.0031 (19) Å from the isoxazole and methylbenzyl ring planes, respectively, in the first molecule, 0.0018 (12) and 0.019 (2) Å in the second molecule], and one cyclohexanol ring having a chair conformation. Although the two molecules have similar bond distances and angles, they differ in the orientation of the cyclohexanol ring with respect to the tolylisoxazole unit. In the first molecule, the dihedral angle between the isoxazole and methylbenzyl rings is 22.03 (8)° and between the isoxazole and cyclohexanol rings is 30.15 (8)°. The corresponding values in the second molecule are 6.13 (10) and 88.44 (8)°, respectively. In the crystal, the molecules are linked by O—H⋯O and O—H⋯N hydrogen bonds, building up a zigzag chain parallel to the a axis.


Related literature
Hydrogen-bond geometry (Å , ).  (Tu et al. 2009, Tang et al. 2009). Isoxazole systems have also been targeted in synthetic investigations for their known biological and pharmacological properties such as hypoglycemic, anti-inflammatory and anti-bacterial activities. Recently, the growing interest in such analogues also rises from their high potential value as antiviral (Deng et al. 2009, Lee et al. 2009) and anti-tumor agents (Kozikowski et al. 2008).
We have undertaken the X-ray diffraction study of the title compound, in order to understand the molecular features which stabilize its observed conformation. The asymmetric unit contains two molecules crystallographically independent. Each molecule is formed by three interconnected cycles, two essentially planar rings: isoxazole and methylbenzyl rings while the 3rd ring (cyclohexanol) has a chair conformation (Fig. 1). The difference between the molecules lies in the orientation of the rings in each molecule as shown in the fitting drawing (  (Table 1, Fig. 3).

Experimental
A mixture of 1-ethynylcyclohexanol (1 mmol) and p-methylbenzylaldoxime (1.2 mmol) was dissolved in CH 2 Cl 2 (20 ml), the solution was then cooled thoroughly with ice at 0-5°C. 15 ml of sodium hydroxide solution (12 g. of sodium hydroxide per 100 g. of water) were gradually added under vigorously stirring for 5 h. The organic phase was separated and dried over anhydrous sodium sulfate, filtered and the solvent evaporated under reduced pressure. The residue was purified by recrystallization from ethanol. The structure of adduct was confirmed by spectroscopic methods.
In the absence of significant anomalous scattering, the absolute structure could not be reliably determined and then the Friedel pairs were merged and any references to the Flack parameter were removed.

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 > σ(F 2 ) is used only for calculating Rfactors(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 )