trans-Ethylenedi-p-phenylene diacetate

The centrosymmetric title compound, C18H26O4, was prepared in high yield from 4-acetoxystyrene via Ru-catalysed homo-olefin metathesis. Exclusive formation of the E-configurated isomer was observed. In the crystal, a strong C—H⋯π intermolecular interaction links the molecules together.

The centrosymmetric title compound, C 18 H 26 O 4 , was prepared in high yield from 4-acetoxystyrene via Ru-catalysed homoolefin metathesis. Exclusive formation of the E-configurated isomer was observed. In the crystal, a strong C-HÁ Á Á intermolecular interaction links the molecules together.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HG2554).  Resveratrol-related stilbenes exhibit promising anticancer activity (Aggarwal et al., 2004;Wolter et al., 2002;Fremont et al., 2000;Jang et al., 1997). Based on our own research in the field of bioactive stilbenes (Wieder et al., 2001) we decided to reinvestigate the possibility of using a cross-metathesis strategy for the synthesis of compounds of type 1 (Velder et al., 2006) which turned out to be a highly efficient route towards symmetrically as well as unsymmetrically substituted E-stilbenes. Alternative strategies for the synthesis of stilbenes are based on Wittig-type olefinations or Heck couplings (Kim et al. (2002), Lion et al. (2005), Botella et al. (2004), Reetz et al. (1998)). One of the compounds prepared is the title compound trans-1,2-bis-(4-acetoxyphenyl)ethene. Within each molecule the two planes defined by the arene moieties are co-planar but slightly stepped (by 0.324 (2) Å) due to the fact that the plane defined by the central double bond is twisted by a torsion angle of -13.8 (2)° (C1a-C1-C2-C7) and 165.7 (15)° (C1a-C1-C2-C3), respectively (figure 1). The molecules form layers which are intermolecularly linked through a C-H···π interaction of type III (Malone et al. 1997).

Structure Reports Online
This interaction occurs between the H atom of one phenyl group and the π-system of the other phenyl moiety (figure 2).
With a H···π distance of only 2.77 Å these interactions are rather strong.

Experimental
In a glove-box (Labmaster 130, mBraun), the catalyst (Grubbs-II, 2 mol %) was weighted into a 25 ml Schlenk tube, which was sealed with a rubber septum. This was then taken out of the box, connected to an Ar-vacuum double manifold and equipped with a reflux condenser under argon. A solution of 3-acetoxy-styrene (1.0 g, 6.17 mmol) in CH 2 Cl 2 (20 ml) was added via syringe and the resulting solution was refluxed for 1.5 h under argon. After allowing the reaction mixture to cool to room temperature, the solvent was evaporated in vacuo and the crude product was purified by recrystallization from EtOAc/cyclohexane 5:1 to give 0.8 g (88%) of the homo-metathesis product 1. mp. 214 °C (Johnson et al. (1952)

Refinement
Hydrogen atoms were located in difference syntheses, and are refined at idealized positions (C-H = 0.98Å for methyl H atoms and 0.95Å for all other H Atoms) using a riding model, the U values of the H atoms are constrained relative to U eq of the parent carbon atom (1.2 x U eq (C) for C-H and 1.5 x U eq (C) for methyl H). 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. The coordinates of the hydrogen atoms are constrained, and the U values of the H atoms are constrained relative to the U eq of the atom the hydrogen binds to (1.2 for CH and CH 2 , 1.5 for CH 3 ).