trans-1,2-Bis(3,5-dimethoxy­phen­yl)ethene

Stefanie Ritter; Jörg-M Neudörfl; Janna Velder; Hans-Günther Schmalz

doi:10.1107/S160053680903116X

. 2009 Aug 15;65(Pt 9):o2150. doi: 10.1107/S160053680903116X

trans-1,2-Bis(3,5-dimethoxyphenyl)ethene

Stefanie Ritter ^a, Jörg-M Neudörfl ^a, Janna Velder ^a, Hans-Günther Schmalz ^a,^*

PMCID: PMC2969882 PMID: 21577559

Abstract

The title compound, C₁₈H₂₀O₄, was prepared in high yield from 3,5-dimethoxystyrene via a Ru-catalysed homo-olefin metathesis. Exclusive formation of the E-configurated isomer was observed. Interestingly, one symmetric unit contains two molecules adopting an s-syn-anti and and an all-s-anti conformation.

Related literature

For the preparation of differently substituted stilbenes using a Ru-catalysed metathesis strategy, see: Velder et al. (2006 ▶). Alternative methodologies for the synthesis of oxy-functionalized stilbenes using Wittig-type olefinations or Heck couplings have been described by Kim et al. (2002 ▶), Lion et al. (2005 ▶), Botella & Nayera (2004 ▶) and Reetz et al. (1998 ▶). For the bioactivity of various stilbenes with a focus on their anticancer activity, see: Aggarwal et al. (2004 ▶); Wolter & Stein (2002 ▶); Fremont (2000 ▶); Jang et al. (1997 ▶); Wieder et al. (2001 ▶). For related structures and syntheses see: Yin et al. (2002 ▶); Uda et al. (2002 ▶).

Experimental

Crystal data

C₁₈H₂₀O₄
M _r = 300.34
Monoclinic,
a = 7.1954 (3) Å
b = 9.4203 (4) Å
c = 22.6762 (5) Å
β = 93.783 (2)°
V = 1533.71 (10) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.4 × 0.2 × 0.2 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: none
7687 measured reflections
3320 independent reflections
2142 reflections with I > 2σ(I)
R _int = 0.041

Refinement

R[F ² > 2σ(F ²)] = 0.055
wR(F ²) = 0.150
S = 1.03
3320 reflections
207 parameters
H-atom parameters constrained
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Data collection: COLLECT (Hooft, 1998 ▶); cell refinement: DENZO (Otwinowski & Minor, 1997 ▶); data reduction: DENZO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SCHAKAL99 (Keller 1999 ▶); software used to prepare material for publication: PLATON (Spek, 2009 ▶) and enCIFer (Allen et al., 2004 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S160053680903116X/hg2547sup1.cif

e-65-o2150-sup1.cif^{(18.8KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053680903116X/hg2547Isup2.hkl

e-65-o2150-Isup2.hkl^{(162.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

In recent years, polyhydroxylated stilbenes such as resveratrol have gained a tremendous importance especially due to their potential for the prevention and therapy of cancer (Aggarwal et al. (2004), Wolter et al. (2002), Fremont (2000), Jang et al. (1997)). In the course of our own research in the field of bioactive stilbenes (Wieder et al. (2001)) we were able to develop a highly efficient synthetic route towards symmetrically as well as unsymmetrically substituted E-stilbenes applying a Ru-catalyzed metathesis strategy (Velder et al. (2006)). 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 was the title compound trans-1,2-bis-(3,5-dimethoxyphenyl)ethene. The asymmetric unit contains two molecules, A and B, both of which exhibit a center of symmetry (figure 1). The 3,5-dimethoxy groups of molecule B all adopt a s-anti configuration, whereas in molecule A, a s-syn as well as a s-anti conformation is found on both sides. Zhang and co-workers reported the same observation on a related structure (Yin et al., 2002). The torsion angles between the benzene ring planes in molecule A are 0.2 (3)° (C1a—C1—C2—C3), which gives the molecule a planar shape. Molecule B, in contrast, adopts a slightly twisted conformation with a torsion angle of 7.0 (2)° (C10b—C10—C11—C12). The molecules form slightly twisted pseudo-layers which are arranged along the b axis (Fig. 2). In figure 3, two of those pseudo-layers are shown from the top view (with the front layer being displayed in dark and the retral layer in light green).

Experimental

In a glove-box (Labmaster 130, mBraun), the catalyst (Grubbs-II, 2 mol %) was weighted into a 25 ml Schlenk tube, which was then 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 3,5-dimethoxy-styrene (1 mmol) in CH₂Cl₂ (10 ml) was then 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 flash chromatography (SiO₂, cyclohexane/ ethyl acetate = 10:1) to give 138 mg (0.46 mmol; 92%) of the homo metathesis product (1). mp. 142 °C (Uda et al., 2002: 141–144 °C). 1H NMR (300 MHz, CDCl₃): δ = 3.81 (s, 6H, OCH₃), 6.4 (t, 1H, J = 2.1 Hz,H-4), 6.67 (d, 2H, J = 2.1 Hz, H-2, H-6), 7.00 (s, 1H, H-7); ¹³C NMR (75 MHz, CDCl₃): δ = 55.4 (OCH₃), 100.2 (C-4), 104.7 (C-2, C-6), 129.2 (C-7), 139.2 (C-1), 161.0 (C-3, C-5); HRMS, calcd for C₁₈H₂₀O₄ (M⁺) 300.1361, found 300.136.