Ethyl 4-(4-methoxyphenyl)-2-oxo-6-phenylcyclohex-3-ene-1-carboxylate

The asymmetric unit of the title compound, C22H22O4, consists of two independent molecules (A and B) which differ significantly in the orientations of ethyl carboxylate groups. The phenyl ring in molecule B is disordered over two orientations with occupancies of 0.55 (2) and 0.45 (2). The cyclohexenone ring of both molecules adopts an envelope conformation. The dihedral angle between the two aromatic rings is 81.12 (7)° in molecule A and 70.8 (3)° in molecule B [57.5 (4)° in the minor disorder component]. The crystal structure is stabilized by weak intermolecular C—H⋯O hydrogen bonds and C—H⋯π interactions.

The asymmetric unit of the title compound, C 22 H 22 O 4 , consists of two independent molecules (A and B) which differ significantly in the orientations of ethyl carboxylate groups. The phenyl ring in molecule B is disordered over two orientations with occupancies of 0.55 (2) and 0.45 (2). The cyclohexenone ring of both molecules adopts an envelope conformation. The dihedral angle between the two aromatic rings is 81.12 (7) in molecule A and 70.8 (3) in molecule B [57.5 (4) in the minor disorder component]. The crystal structure is stabilized by weak intermolecular C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions.

S1. Comment
Cyclohexenone is an organic compound which is a versatile intermediate used in the synthesis of a variety of chemical products such as pharmaceuticals and fragrances. The Robinson annulation is an organic reaction used to create a cyclic six-membered, β-unsaturated ketones. Different methods including solvent-free synthesis of these compounds have been reported (Kalluraya & Rai, 2003). Cyclohexenone and their derivatives are known for anti-inflammatory and analegesic activities (Kalluraya & Rahiman, 2003).
The dihedral angle between the two aromatic rings is 81.12 (7)° in molecule A and 70.8 (3)° in molecule B [57.5 (4)° in the minor disorder component].

S2. Experimental
To a solution of 1-phenyl-3-anisyl-prop-2-en-1-one (0.01 mol) in dry acetone (25 ml), dry potassium carbonate (0.04 mol) and ethyl acetoacetate (0.02 mol) in dry acetone (25 ml) were added. The mixture was stirred at room temperature for overnight and was filtered. The solvent from the filtrate on evaporation gave a solid which was recrystallized from a mixture of ethanol-dioxane.

S3. Refinement
The phenyl ring in molecule B is disordered over two orientations with refined occupancies of 0.545 (17) and 0.455 (17).
The C-C bond lengths involving the disordered atoms were restrained to be equal and also the U ij components of the disordered atoms were approximated to isotropic behaviour. The two orientations were restrained to be planar. H atoms were positioned geometrically (C-H = 0.95-1.00 Å) and refined using a riding model, with U iso (H) = 1.2U eq (C) and 1.5U eq (C methyl ). A rotating group model was used for the methyl groups. The highest four difference peaks were observed at 0.92, 0.83, 0.87 and 84 Å, respectively, from atoms C3B, C2B, C2A and C3A. No suitable disorder model involving these atoms were found.    The crystal packing of the title compound, viewed down the c axis. Only the major disorder component of an independent molecule is shown.

Ethyl 4-(4-methoxyphenyl)-2-oxo-6-phenylcyclohex-3-ene-1-carboxylate
Special details Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. 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. 0.0524 (7) 0.0269 (5)