(1E,4E)-1-(Thiophen-2-yl)-5-(2,6,6-trimethylcyclohex-1-en-1-yl)penta-1,4-dien-3-one

In the title curcumin–ionone derivative, C18H22OS, the dihedral angle between the thiazole ring and the mean plane through the cyclohexene ring is 5.16 (10)°. The molecule has an E conformation for each of the olefinic bonds.

In the title curcumin-ionone derivative, C 18 H 22 OS, the dihedral angle between the thiazole ring and the mean plane through the cyclohexene ring is 5.16 (10) . The molecule has an E conformation for each of the olefinic bonds.

Comment
The β-ionone unit is a phytochemical present in many fruit, vegetable and grain. It is found to exert in vitro anticarcinogenic and antitumor activities; ionone derivatives are valuable intermediates for the chemo-enzymatic synthesis of carotenoids, astaxanthin and zeaxanthin (Zhou et al., 2009a,b). On the other hand, curcumin (diferuloylmethane) is a polyphenolic phytochemical found in turmeric (Curcuma longa) that has useful medicinal properties (Anand et al., 2008). Previously, we have evaluated mono-carbonylanalogues of curcumin for anti-inflammatory properties and discussed structure-activity relationships (Liang et al., 2007;Zhao et al.,2010a,b).
In the ionone-based curcumin title compound (Scheme I), all bond dimensions are normal. The dihedral angles between the thiazole ring and the cyclohexene ring is 5.16 (10)°.

Experimental
To the mixture of β-ionone (2.5 mmol, 0.481 g) and thiophene-2-carbaldehyde (2.5mmol) in 10 ml EtOH, 1 ml of 10% NaOH was added and the mixture was stirred for 12 h at room temperature. After addition of 10 ml H 2 O, the solution was extracted by 3×10 ml CH 2 Cl 2 . The crude product obtained from the combined organic layers was purified by silica gel column chromatography (elutant: EtOAc/hexane). Crystals were obtained from an ethanol/EtOAc solution (1:2, v/v) at 293 K.
Hydrogen atoms are drawn as spheres of arbitrary radius.  Δρ min = −0.17 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.013 (5) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.