(E)-4-(4-Methoxyphenyl)but-3-en-2-one

In the title compound, C11H12O2, the dihedral angle between the benzene ring and the but-3-en-2-one group is 4.04 (5)°. The crystal packing features chains, parallel to [-101], composed of dimers connected by weak C—H⋯O interactions..


Comment
The title compound belongs to the class of unsaturated α,β-acyclic ketones. α,β-unsaturated ketones have been found useful in the preparation of a wide variety of nitrogen heterocycles both in solution phase and solid state. Many of these synthesis have proceeded through interesting mechanisms. These compounds have been used as substrates for the preparation of anti-cancer, cell-specific triarylpyridines via immobilized bismuth nitrate catalyzed cascade reactions.
These compounds have been extensively used in the preparation of cardiovascular Hantzsch products, many of which are prescribed drugs. α,β-unsaturated ketones are easily elaborated to anti-anxiety diazepines which also regulate our central nervous system. When treated with hydrazine, α,β-unsaturated compounds yield substituted pyrazoles which have a wide spectrum of bioactivity. The molecular structure of the title compound is shown in Fig.1. The bond distances are within normal ranges (Allen et al., 1987) and comparable to those in related structures (Jasinski et al., 2010;Fun et al., 2011;Dutkiewicz et al., 2011). The six bond lengths in the benzene ring lie in the range 1.355 (2)-1.391 (2) Å with an average value of 1.372 (2) Å. The average bond angle of the phenyl ring is 120.0 (1)°. In the title compound the benzene ring is perfectly planar with a maximum deviation of 0.006 (2) Å for C2′. The dihedral angle between the benzene ring and the acyclic chain is 4.04 (5)°. In the crystal structure, intermolecular C-H···O hydrogen bonds link the molecules into chains ( Fig.2).

Experimental
Normally, α,β-unsaturated compounds are prepared by the reaction of an aldehyde and an active methylene compounds by Claisen-Schmidt reaction, using a strong base or an acid as catalyst. Under these reaction conditions, aromatic aldehydes and acetone react hard to form diarylidene ketone by double Claisen condensation. Monocondensation processes are known but yields are poor. To improve yield of monocondensation products, a search for catalyst was undertaken and sodium tungstate in ethanol was found as the catalyst of choice. The title compound was prepared in 96% yield by stirring the mixture of anisaldehyde (1 X 10-2 mol) and acetone (1 X 10-2 mol) in the presence of sodium tungstate (30 mol %) using ethanol as solvent at room temperature (25°C) for 24h. The reaction was monitored by thin layer chromatography. On completion of the reaction, the reaction mixture was diluted with water (25ml) and extracted with ethyl acetate (50 ml). The organic layer was washed with water, brine and water, dried over anhydrous sodium sulphate and concentrated. The title compound was purified by column chromatography on silica gel, using CH 2 Cl 2 -EtOAC (9:1v/v) as solvent. The compound was crystallized from chloroform-methanol, m.p. 445K. Single crystals for XRD study were obtained by slow evaporation of chloroform solution.

Refinement
All H atoms were positioned geometrically and were treated as riding on their parent C atoms, with C-H distances of 0.93-0.96 Å and with U iso (H) = 1.2Ueq(C), except for the methyl groups where U iso (H) = 1.5Ueq(C),.

Computing details
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: PLATON (Spek, 2009).   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.36 e Å −3 Δρ min = −0.60 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.093 (13) 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.