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The stilbene derivative 1,2,3-trimethoxy-4-[(E)-2-phenylvinyl]benzene, C17H18O3, (I), and its homocoupling co-product (E,E)-1,4-bis(2,3,4-trimethoxyphenyl)buta-1,3-diene, C22H26O6, (II), both have double bonds in trans conformations in their conjugated linkages. In the structure of stilbene (I), the aromatic rings deviate significantly from coplanarity, in contrast with coproduct (II), the core of which is rigorously planar. The deviation in stilbene (I) seems to be driven by intermolecular electrostatic interactions. Diene (II) sits on a crystallographic inversion centre, which bisects the conjugated linkage.
Supporting information
CCDC references: 742234; 742235
Compounds (I) and (II) were prepared according to the literature procedure of
Bazin et al. (2007). Compound (II) was isolated as the
homocoupling
by-product. Compound (I) was recrystallized from methanol to afford pure (I)
as white [Colourless in CIF] crystals (m.p. 355 K). Spectroscopic
analysis: 1H NMR (CDCl3, 400 MHz, δ, p.p.m.): 3.89 (s, 3H, –OMe),
3.90 (s, 3H, –OMe), 3.91 (s, 3H, –OMe), 6.71 (d, 1H,
J = 8.8 Hz), 7.03 (d, 1H, J = 16.6 Hz), 7.24–7.37
(m, 5H), 7.51–7.53 (m, 2H); 13C NMR (CDCl3, 100 MHz, δ,
p.p.m.): 56.0 (–OMe), 60.9 (–OMe), 61.3 (–OMe), 107.8, 120.7, 122.9, 124.5,
126.4 (2 C), 127.2, 127.9, 128.6 (2 C), 137.9, 142.4, 151.7, 153.2; MS (ESI):
[M+H]+ 271. Compound (II) was recrystallized by slow evaporation of a
cyclohexane/ethyl acetate [Solvent ratio?] solution, giving yellow
[Colourless in CIF] crystals of (II) after 1 or 2 d. Spectroscopic
analysis: 1H NMR (CDCl3, 400 MHz, δ, p.p.m.): 3.87, 3.88 and 3.89
(3s, 18H, 6-OMe), 6.41–6.54 (m, 2H), 6.63–6.70 (m, 2H),
6.87–6.90 (m, 1H), 7.12–7.23 (m, 3H); MS (ESI):
[M+H]+ 387.
All H atoms were determined via difference Fourier maps and refined with
isotropic atomic displacement parameters. [Please give range of refined
C—H distances]
For both compounds, data collection: APEX2 (Bruker, 2006); cell refinement: APEX2 (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
(I) 1,2,3-Trimethoxy-4-[(
E)-2-phenylvinyl]benzene
top
Crystal data top
C17H18O3 | F(000) = 576 |
Mr = 270.31 | Dx = 1.231 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 9739 reflections |
a = 10.7138 (7) Å | θ = 2.5–36.0° |
b = 7.1069 (5) Å | µ = 0.08 mm−1 |
c = 19.8033 (13) Å | T = 296 K |
β = 104.760 (3)° | Plate, colourless |
V = 1458.10 (17) Å3 | 0.52 × 0.37 × 0.25 mm |
Z = 4 | |
Data collection top
Bruker APEXII CCD area-detector diffractometer | 5406 reflections with I > 2σ(I) |
Radiation source: sealed tube | Rint = 0.027 |
Graphite monochromator | θmax = 35.0°, θmin = 2.0° |
ϕ and ω scans | h = −16→17 |
66478 measured reflections | k = −11→11 |
6392 independent reflections | l = −31→31 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.038 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.122 | All H-atom parameters refined |
S = 1.07 | w = 1/[σ2(Fo2) + (0.0729P)2 + 0.2108P] where P = (Fo2 + 2Fc2)/3 |
6392 reflections | (Δ/σ)max < 0.001 |
253 parameters | Δρmax = 0.63 e Å−3 |
0 restraints | Δρmin = −0.22 e Å−3 |
Crystal data top
C17H18O3 | V = 1458.10 (17) Å3 |
Mr = 270.31 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 10.7138 (7) Å | µ = 0.08 mm−1 |
b = 7.1069 (5) Å | T = 296 K |
c = 19.8033 (13) Å | 0.52 × 0.37 × 0.25 mm |
β = 104.760 (3)° | |
Data collection top
Bruker APEXII CCD area-detector diffractometer | 5406 reflections with I > 2σ(I) |
66478 measured reflections | Rint = 0.027 |
6392 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.122 | All H-atom parameters refined |
S = 1.07 | Δρmax = 0.63 e Å−3 |
6392 reflections | Δρmin = −0.22 e Å−3 |
253 parameters | |
Special details top
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 F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
C1 | 0.14291 (6) | 0.47639 (8) | 0.16862 (3) | 0.01361 (10) | |
C2 | 0.23922 (6) | 0.33830 (9) | 0.18580 (3) | 0.01582 (11) | |
H2 | 0.2361 (11) | 0.2457 (16) | 0.2228 (6) | 0.022 (2)* | |
C3 | 0.33426 (6) | 0.31824 (9) | 0.14994 (3) | 0.01656 (11) | |
H3 | 0.4022 (11) | 0.2228 (17) | 0.1645 (6) | 0.027 (3)* | |
C4 | 0.33371 (6) | 0.43529 (8) | 0.09331 (3) | 0.01398 (10) | |
C5 | 0.23913 (5) | 0.57579 (8) | 0.07491 (3) | 0.01343 (10) | |
C6 | 0.14696 (5) | 0.59793 (8) | 0.11299 (3) | 0.01333 (10) | |
C7 | 0.03922 (6) | 0.49449 (8) | 0.20434 (3) | 0.01495 (11) | |
H7 | −0.0253 (11) | 0.5923 (16) | 0.1849 (6) | 0.024 (3)* | |
C8 | 0.02736 (6) | 0.38905 (9) | 0.25873 (3) | 0.01576 (11) | |
H8 | 0.0932 (12) | 0.2921 (19) | 0.2796 (7) | 0.035 (3)* | |
C9 | −0.07715 (6) | 0.39765 (8) | 0.29423 (3) | 0.01448 (10) | |
C10 | −0.06031 (6) | 0.30219 (10) | 0.35774 (3) | 0.01853 (12) | |
H10 | 0.0218 (11) | 0.2408 (17) | 0.3789 (6) | 0.028 (3)* | |
C11 | −0.15615 (7) | 0.30006 (10) | 0.39362 (3) | 0.02069 (12) | |
H11 | −0.1400 (11) | 0.2281 (17) | 0.4377 (6) | 0.027 (3)* | |
C12 | −0.27147 (7) | 0.39405 (10) | 0.36657 (4) | 0.02157 (13) | |
H12 | −0.3388 (12) | 0.3902 (18) | 0.3924 (6) | 0.033 (3)* | |
C13 | −0.29003 (7) | 0.48988 (11) | 0.30344 (4) | 0.02386 (14) | |
H13 | −0.3715 (13) | 0.5524 (19) | 0.2817 (7) | 0.037 (3)* | |
C14 | −0.19428 (6) | 0.49194 (10) | 0.26734 (4) | 0.01983 (12) | |
H14 | −0.2121 (11) | 0.5589 (16) | 0.2220 (6) | 0.026 (3)* | |
O1 | 0.05531 (4) | 0.73719 (7) | 0.09349 (3) | 0.01729 (10) | |
C15 | 0.10639 (8) | 0.92301 (10) | 0.11076 (5) | 0.02610 (15) | |
H15A | 0.0376 (14) | 1.010 (2) | 0.0899 (7) | 0.045 (4)* | |
H15B | 0.1303 (17) | 0.940 (2) | 0.1641 (9) | 0.070 (5)* | |
H15C | 0.1811 (13) | 0.9449 (19) | 0.0938 (7) | 0.040 (3)* | |
O2 | 0.24124 (4) | 0.69496 (7) | 0.02055 (2) | 0.01632 (9) | |
C16 | 0.15007 (7) | 0.64190 (11) | −0.04315 (3) | 0.02276 (13) | |
H16A | 0.1667 (11) | 0.7272 (17) | −0.0786 (6) | 0.029 (3)* | |
H16B | 0.1671 (12) | 0.5092 (19) | −0.0577 (7) | 0.038 (3)* | |
H16C | 0.0608 (12) | 0.6544 (18) | −0.0386 (7) | 0.033 (3)* | |
O3 | 0.41951 (5) | 0.42633 (7) | 0.05340 (2) | 0.01679 (10) | |
C17 | 0.52332 (8) | 0.29419 (12) | 0.07398 (4) | 0.02635 (15) | |
H17A | 0.4905 (12) | 0.1651 (18) | 0.0716 (6) | 0.034 (3)* | |
H17B | 0.5762 (12) | 0.3230 (18) | 0.1204 (6) | 0.031 (3)* | |
H17C | 0.5735 (11) | 0.3116 (17) | 0.0392 (6) | 0.032 (3)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1 | 0.0145 (2) | 0.0134 (2) | 0.0134 (2) | −0.00109 (17) | 0.00449 (17) | 0.00001 (17) |
C2 | 0.0180 (2) | 0.0160 (2) | 0.0146 (2) | 0.00184 (19) | 0.00626 (19) | 0.00274 (18) |
C3 | 0.0185 (2) | 0.0163 (2) | 0.0162 (2) | 0.00356 (19) | 0.00678 (19) | 0.00339 (19) |
C4 | 0.0143 (2) | 0.0149 (2) | 0.0135 (2) | 0.00065 (18) | 0.00482 (17) | 0.00072 (18) |
C5 | 0.0134 (2) | 0.0137 (2) | 0.0132 (2) | −0.00054 (17) | 0.00350 (17) | 0.00195 (17) |
C6 | 0.0126 (2) | 0.0129 (2) | 0.0145 (2) | −0.00028 (17) | 0.00339 (17) | 0.00099 (17) |
C7 | 0.0155 (2) | 0.0152 (2) | 0.0150 (2) | −0.00097 (18) | 0.00554 (18) | −0.00045 (18) |
C8 | 0.0149 (2) | 0.0174 (2) | 0.0159 (2) | −0.00015 (19) | 0.00551 (18) | 0.00145 (19) |
C9 | 0.0150 (2) | 0.0140 (2) | 0.0152 (2) | −0.00095 (18) | 0.00524 (18) | 0.00076 (18) |
C10 | 0.0174 (3) | 0.0211 (3) | 0.0178 (2) | 0.0008 (2) | 0.0057 (2) | 0.0049 (2) |
C11 | 0.0224 (3) | 0.0237 (3) | 0.0179 (2) | −0.0022 (2) | 0.0087 (2) | 0.0032 (2) |
C12 | 0.0221 (3) | 0.0204 (3) | 0.0266 (3) | −0.0005 (2) | 0.0142 (2) | 0.0010 (2) |
C13 | 0.0198 (3) | 0.0229 (3) | 0.0322 (3) | 0.0054 (2) | 0.0126 (3) | 0.0081 (3) |
C14 | 0.0177 (3) | 0.0210 (3) | 0.0223 (3) | 0.0029 (2) | 0.0078 (2) | 0.0072 (2) |
O1 | 0.01418 (19) | 0.01464 (19) | 0.0234 (2) | 0.00198 (14) | 0.00547 (16) | 0.00408 (16) |
C15 | 0.0252 (3) | 0.0144 (3) | 0.0400 (4) | 0.0017 (2) | 0.0107 (3) | 0.0009 (3) |
O2 | 0.01591 (19) | 0.0180 (2) | 0.01482 (18) | −0.00124 (15) | 0.00357 (15) | 0.00482 (15) |
C16 | 0.0249 (3) | 0.0255 (3) | 0.0153 (2) | −0.0006 (2) | 0.0005 (2) | 0.0040 (2) |
O3 | 0.01709 (19) | 0.0189 (2) | 0.01663 (19) | 0.00391 (15) | 0.00838 (15) | 0.00314 (15) |
C17 | 0.0245 (3) | 0.0314 (4) | 0.0275 (3) | 0.0135 (3) | 0.0146 (3) | 0.0116 (3) |
Geometric parameters (Å, º) top
C1—C2 | 1.4017 (9) | C11—C12 | 1.3865 (10) |
C1—C6 | 1.4093 (8) | C11—H11 | 0.989 (12) |
C1—C7 | 1.4667 (8) | C12—C13 | 1.3926 (10) |
C2—C3 | 1.3893 (8) | C12—H12 | 0.986 (12) |
C2—H2 | 0.991 (11) | C13—C14 | 1.3919 (9) |
C3—C4 | 1.3951 (8) | C13—H13 | 0.977 (13) |
C3—H3 | 0.983 (12) | C14—H14 | 0.991 (11) |
C4—O3 | 1.3578 (7) | O1—C15 | 1.4370 (9) |
C4—C5 | 1.4030 (8) | C15—H15A | 0.970 (14) |
C5—O2 | 1.3745 (7) | C15—H15B | 1.028 (17) |
C5—C6 | 1.3956 (8) | C15—H15C | 0.956 (13) |
C6—O1 | 1.3783 (7) | O2—C16 | 1.4351 (8) |
C7—C8 | 1.3445 (8) | C16—H16A | 0.979 (12) |
C7—H7 | 0.987 (11) | C16—H16B | 1.016 (13) |
C8—C9 | 1.4673 (8) | C16—H16C | 0.987 (12) |
C8—H8 | 0.998 (13) | O3—C17 | 1.4332 (8) |
C9—C10 | 1.3997 (8) | C17—H17A | 0.980 (13) |
C9—C14 | 1.4024 (9) | C17—H17B | 0.971 (12) |
C10—C11 | 1.3896 (9) | C17—H17C | 0.983 (12) |
C10—H10 | 0.975 (12) | | |
| | | |
C2—C1—C6 | 116.84 (5) | C10—C11—H11 | 118.1 (7) |
C2—C1—C7 | 123.06 (5) | C11—C12—C13 | 119.47 (6) |
C6—C1—C7 | 120.08 (5) | C11—C12—H12 | 118.9 (7) |
C3—C2—C1 | 122.54 (5) | C13—C12—H12 | 121.6 (7) |
C3—C2—H2 | 118.4 (6) | C14—C13—C12 | 120.71 (6) |
C1—C2—H2 | 118.9 (6) | C14—C13—H13 | 117.5 (7) |
C2—C3—C4 | 119.75 (6) | C12—C13—H13 | 121.8 (7) |
C2—C3—H3 | 120.3 (7) | C13—C14—C9 | 120.35 (6) |
C4—C3—H3 | 119.9 (7) | C13—C14—H14 | 118.2 (6) |
O3—C4—C3 | 125.10 (5) | C9—C14—H14 | 121.4 (6) |
O3—C4—C5 | 115.69 (5) | C6—O1—C15 | 113.10 (5) |
C3—C4—C5 | 119.21 (5) | O1—C15—H15A | 106.4 (9) |
O2—C5—C6 | 120.58 (5) | O1—C15—H15B | 109.3 (10) |
O2—C5—C4 | 119.14 (5) | H15A—C15—H15B | 109.2 (13) |
C6—C5—C4 | 120.24 (5) | O1—C15—H15C | 111.6 (8) |
O1—C6—C5 | 118.77 (5) | H15A—C15—H15C | 111.1 (11) |
O1—C6—C1 | 119.82 (5) | H15B—C15—H15C | 109.3 (12) |
C5—C6—C1 | 121.35 (5) | C5—O2—C16 | 112.53 (5) |
C8—C7—C1 | 125.12 (6) | O2—C16—H16A | 105.1 (7) |
C8—C7—H7 | 120.4 (6) | O2—C16—H16B | 111.2 (7) |
C1—C7—H7 | 114.5 (6) | H16A—C16—H16B | 107.0 (10) |
C7—C8—C9 | 126.87 (6) | O2—C16—H16C | 110.7 (7) |
C7—C8—H8 | 121.0 (7) | H16A—C16—H16C | 111.6 (10) |
C9—C8—H8 | 112.1 (7) | H16B—C16—H16C | 111.0 (11) |
C10—C9—C14 | 118.09 (6) | C4—O3—C17 | 117.17 (5) |
C10—C9—C8 | 118.10 (5) | O3—C17—H17A | 110.9 (7) |
C14—C9—C8 | 123.80 (5) | O3—C17—H17B | 110.8 (7) |
C11—C10—C9 | 121.45 (6) | H17A—C17—H17B | 111.0 (10) |
C11—C10—H10 | 118.5 (7) | O3—C17—H17C | 104.0 (7) |
C9—C10—H10 | 119.9 (7) | H17A—C17—H17C | 109.8 (10) |
C12—C11—C10 | 119.93 (6) | H17B—C17—H17C | 110.2 (10) |
C12—C11—H11 | 121.9 (7) | | |
(II) (
E,
E)-1,4-bis(2,3,4-trimethoxyphenyl)buta-1,3-diene
top
Crystal data top
C22H26O6 | F(000) = 412 |
Mr = 386.43 | Dx = 1.299 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 9216 reflections |
a = 10.2899 (4) Å | θ = 2.3–36.3° |
b = 7.0186 (3) Å | µ = 0.09 mm−1 |
c = 13.9897 (5) Å | T = 296 K |
β = 102.138 (2)° | Plate, colourless |
V = 987.76 (7) Å3 | 0.32 × 0.21 × 0.18 mm |
Z = 2 | |
Data collection top
Bruker APEXII CCD area-detector diffractometer | 3409 reflections with I > 2σ(I) |
Radiation source: sealed tube | Rint = 0.053 |
Graphite monochromator | θmax = 35.0°, θmin = 2.3° |
ϕ and ω scans | h = −16→16 |
30080 measured reflections | k = −11→10 |
4333 independent reflections | l = −21→22 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.046 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.136 | All H-atom parameters refined |
S = 1.07 | w = 1/[σ2(Fo2) + (0.0829P)2 + 0.1139P] where P = (Fo2 + 2Fc2)/3 |
4333 reflections | (Δ/σ)max < 0.001 |
179 parameters | Δρmax = 0.68 e Å−3 |
0 restraints | Δρmin = −0.28 e Å−3 |
Crystal data top
C22H26O6 | V = 987.76 (7) Å3 |
Mr = 386.43 | Z = 2 |
Monoclinic, P21/n | Mo Kα radiation |
a = 10.2899 (4) Å | µ = 0.09 mm−1 |
b = 7.0186 (3) Å | T = 296 K |
c = 13.9897 (5) Å | 0.32 × 0.21 × 0.18 mm |
β = 102.138 (2)° | |
Data collection top
Bruker APEXII CCD area-detector diffractometer | 3409 reflections with I > 2σ(I) |
30080 measured reflections | Rint = 0.053 |
4333 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.046 | 0 restraints |
wR(F2) = 0.136 | All H-atom parameters refined |
S = 1.07 | Δρmax = 0.68 e Å−3 |
4333 reflections | Δρmin = −0.28 e Å−3 |
179 parameters | |
Special details top
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 F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
C1 | 0.28922 (7) | 0.06584 (11) | 0.12655 (6) | 0.01294 (14) | |
C2 | 0.29912 (8) | −0.06337 (11) | 0.20410 (6) | 0.01579 (15) | |
H2 | 0.2234 (14) | −0.150 (2) | 0.2091 (10) | 0.021 (3)* | |
C3 | 0.41067 (8) | −0.07076 (11) | 0.27982 (6) | 0.01584 (15) | |
H3 | 0.4118 (14) | −0.161 (2) | 0.3324 (10) | 0.026 (3)* | |
C4 | 0.51690 (7) | 0.05351 (11) | 0.28063 (6) | 0.01356 (14) | |
C5 | 0.51088 (7) | 0.18244 (10) | 0.20317 (6) | 0.01276 (14) | |
C6 | 0.39819 (7) | 0.18788 (10) | 0.12767 (5) | 0.01247 (14) | |
C7 | 0.17092 (7) | 0.08541 (11) | 0.04843 (6) | 0.01402 (14) | |
H7 | 0.1750 (14) | 0.1769 (19) | −0.0002 (10) | 0.021 (3)* | |
C8 | 0.05752 (7) | −0.01658 (11) | 0.03862 (5) | 0.01399 (14) | |
H8 | 0.0492 (13) | −0.117 (2) | 0.0854 (9) | 0.022 (3)* | |
O1 | 0.39277 (6) | 0.32140 (8) | 0.05491 (4) | 0.01553 (13) | |
C9 | 0.45411 (10) | 0.25947 (14) | −0.02267 (7) | 0.02239 (18) | |
H9A | 0.5473 (15) | 0.221 (2) | 0.0032 (11) | 0.034 (4)* | |
H9B | 0.4567 (15) | 0.365 (2) | −0.0674 (11) | 0.029 (3)* | |
H9C | 0.4056 (15) | 0.149 (2) | −0.0570 (10) | 0.030 (4)* | |
O2 | 0.61634 (6) | 0.30017 (8) | 0.19888 (4) | 0.01464 (12) | |
C10 | 0.62063 (9) | 0.46692 (12) | 0.25903 (6) | 0.01910 (16) | |
H10A | 0.6370 (15) | 0.4368 (19) | 0.3281 (11) | 0.026 (3)* | |
H10B | 0.5335 (15) | 0.533 (2) | 0.2442 (11) | 0.033 (4)* | |
H10C | 0.6886 (13) | 0.542 (2) | 0.2437 (9) | 0.021 (3)* | |
O3 | 0.62882 (6) | 0.06182 (9) | 0.35277 (4) | 0.01632 (13) | |
C11 | 0.64741 (9) | −0.08735 (12) | 0.42413 (6) | 0.01779 (16) | |
H11C | 0.5806 (15) | −0.085 (2) | 0.4615 (10) | 0.025 (3)* | |
H11A | 0.7306 (15) | −0.056 (2) | 0.4665 (11) | 0.031 (4)* | |
H11B | 0.6526 (14) | −0.211 (2) | 0.3929 (10) | 0.026 (3)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1 | 0.0130 (3) | 0.0113 (3) | 0.0140 (3) | −0.0013 (2) | 0.0015 (2) | −0.0003 (2) |
C2 | 0.0148 (3) | 0.0147 (3) | 0.0169 (3) | −0.0041 (2) | 0.0009 (2) | 0.0025 (2) |
C3 | 0.0155 (3) | 0.0145 (3) | 0.0165 (3) | −0.0032 (2) | 0.0009 (2) | 0.0033 (2) |
C4 | 0.0133 (3) | 0.0124 (3) | 0.0140 (3) | −0.0009 (2) | 0.0006 (2) | 0.0006 (2) |
C5 | 0.0123 (3) | 0.0104 (3) | 0.0154 (3) | −0.0017 (2) | 0.0028 (2) | 0.0002 (2) |
C6 | 0.0136 (3) | 0.0100 (3) | 0.0136 (3) | −0.0004 (2) | 0.0024 (2) | 0.0008 (2) |
C7 | 0.0135 (3) | 0.0134 (3) | 0.0142 (3) | −0.0013 (2) | 0.0009 (2) | −0.0004 (2) |
C8 | 0.0137 (3) | 0.0135 (3) | 0.0140 (3) | −0.0008 (2) | 0.0014 (2) | −0.0018 (2) |
O1 | 0.0184 (3) | 0.0122 (3) | 0.0158 (3) | −0.00030 (19) | 0.0032 (2) | 0.00383 (19) |
C9 | 0.0308 (4) | 0.0200 (4) | 0.0179 (4) | −0.0025 (3) | 0.0087 (3) | 0.0018 (3) |
O2 | 0.0136 (2) | 0.0126 (2) | 0.0181 (3) | −0.00376 (18) | 0.00403 (19) | −0.00145 (19) |
C10 | 0.0238 (4) | 0.0144 (3) | 0.0197 (4) | −0.0065 (3) | 0.0060 (3) | −0.0031 (3) |
O3 | 0.0146 (2) | 0.0151 (3) | 0.0167 (3) | −0.00239 (19) | −0.00243 (19) | 0.00352 (19) |
C11 | 0.0188 (3) | 0.0159 (3) | 0.0169 (3) | 0.0002 (3) | −0.0002 (3) | 0.0035 (3) |
Geometric parameters (Å, º) top
C1—C2 | 1.4012 (11) | C8—C8i | 1.4441 (14) |
C1—C6 | 1.4085 (10) | C8—H8 | 0.977 (14) |
C1—C7 | 1.4614 (10) | O1—C9 | 1.4330 (11) |
C2—C3 | 1.3896 (11) | C9—H9A | 0.988 (15) |
C2—H2 | 1.001 (14) | C9—H9B | 0.973 (16) |
C3—C4 | 1.3966 (11) | C9—H9C | 0.992 (16) |
C3—H3 | 0.967 (14) | O2—C10 | 1.4367 (10) |
C4—O3 | 1.3637 (9) | C10—H10A | 0.968 (15) |
C4—C5 | 1.4032 (11) | C10—H10B | 0.992 (16) |
C5—O2 | 1.3752 (9) | C10—H10C | 0.935 (14) |
C5—C6 | 1.3952 (10) | O3—C11 | 1.4314 (10) |
C6—O1 | 1.3761 (9) | C11—H11C | 0.947 (15) |
C7—C8 | 1.3511 (11) | C11—H11A | 0.958 (15) |
C7—H7 | 0.943 (13) | C11—H11B | 0.979 (14) |
| | | |
C2—C1—C6 | 117.19 (7) | C8i—C8—H8 | 116.3 (8) |
C2—C1—C7 | 123.60 (7) | C6—O1—C9 | 113.45 (6) |
C6—C1—C7 | 119.15 (7) | O1—C9—H9A | 110.7 (9) |
C3—C2—C1 | 121.89 (7) | O1—C9—H9B | 109.4 (9) |
C3—C2—H2 | 117.0 (8) | H9A—C9—H9B | 106.6 (12) |
C1—C2—H2 | 121.0 (8) | O1—C9—H9C | 110.3 (9) |
C2—C3—C4 | 120.16 (7) | H9A—C9—H9C | 108.4 (13) |
C2—C3—H3 | 118.7 (9) | H9B—C9—H9C | 111.4 (12) |
C4—C3—H3 | 121.1 (9) | C5—O2—C10 | 113.04 (6) |
O3—C4—C3 | 124.78 (7) | O2—C10—H10A | 112.6 (8) |
O3—C4—C5 | 115.93 (7) | O2—C10—H10B | 110.2 (9) |
C3—C4—C5 | 119.29 (7) | H10A—C10—H10B | 105.7 (12) |
O2—C5—C6 | 119.23 (7) | O2—C10—H10C | 104.8 (8) |
O2—C5—C4 | 120.94 (7) | H10A—C10—H10C | 111.7 (12) |
C6—C5—C4 | 119.80 (7) | H10B—C10—H10C | 112.0 (12) |
O1—C6—C5 | 118.46 (6) | C4—O3—C11 | 116.94 (6) |
O1—C6—C1 | 119.84 (7) | O3—C11—H11C | 111.6 (9) |
C5—C6—C1 | 121.65 (7) | O3—C11—H11A | 103.7 (9) |
C8—C7—C1 | 126.30 (7) | H11C—C11—H11A | 108.3 (12) |
C8—C7—H7 | 117.1 (8) | O3—C11—H11B | 110.5 (8) |
C1—C7—H7 | 116.6 (8) | H11C—C11—H11B | 112.0 (12) |
C7—C8—C8i | 123.04 (9) | H11A—C11—H11B | 110.5 (12) |
C7—C8—H8 | 120.6 (8) | | |
Symmetry code: (i) −x, −y, −z. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | C17H18O3 | C22H26O6 |
Mr | 270.31 | 386.43 |
Crystal system, space group | Monoclinic, P21/n | Monoclinic, P21/n |
Temperature (K) | 296 | 296 |
a, b, c (Å) | 10.7138 (7), 7.1069 (5), 19.8033 (13) | 10.2899 (4), 7.0186 (3), 13.9897 (5) |
β (°) | 104.760 (3) | 102.138 (2) |
V (Å3) | 1458.10 (17) | 987.76 (7) |
Z | 4 | 2 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.08 | 0.09 |
Crystal size (mm) | 0.52 × 0.37 × 0.25 | 0.32 × 0.21 × 0.18 |
|
Data collection |
Diffractometer | Bruker APEXII CCD area-detector diffractometer | Bruker APEXII CCD area-detector diffractometer |
Absorption correction | – | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 66478, 6392, 5406 | 30080, 4333, 3409 |
Rint | 0.027 | 0.053 |
(sin θ/λ)max (Å−1) | 0.806 | 0.806 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.122, 1.07 | 0.046, 0.136, 1.07 |
No. of reflections | 6392 | 4333 |
No. of parameters | 253 | 179 |
H-atom treatment | All H-atom parameters refined | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.63, −0.22 | 0.68, −0.28 |
Selected bond lengths (Å) for (I) topC1—C7 | 1.4667 (8) | C8—C9 | 1.4673 (8) |
C7—C8 | 1.3445 (8) | | |
Selected bond lengths (Å) for (II) topC1—C7 | 1.4614 (10) | C8—C8i | 1.4441 (14) |
C7—C8 | 1.3511 (11) | | |
Symmetry code: (i) −x, −y, −z. |
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Stilbenes are important core structures and their photochemical [photooxygenation (Kwon et al., 1989)] and photophysical properties [photoisomerization (Waldeck, 1991), fluorescence (Chaudhuri & Ganguly, 1969; Singh & Kanvah, 2001), photochromic activity (Irie et al., 1994; Lucas et al., 1998)] have been widely studied in connection with π–π* electronic transitions of the C═C double bound. Stilbenes can exist as two possible isomers, trans-stilbene and cis-stilbene. The cis series, for example, is involved in the combretastatin derivatives, compounds that display cytotoxic activities against a wide range of human cancers (Pettit et al., 2005). Stilbenes are not only used as dyes and in optics (lasers), but are also of interest from a medical point of view (Heynekamp et al., 2006; Sanoh et al., 2006; Vander Jagt & Deck, 2007).
Other natural products, derived from trans-stilbenes such as resveratrol and its analogues, exhibit important biological activities. Indeed, trans-resveratrol is known to possess antioxidant and anti-inflammatory properties and is antiproliferative with pro-apoptotic effects (Baur & Sinclair, 2006).
We have previously reported a synthesis of trans-1,2-diarylethenes (trans-stilbenes), compounds having potential photoprotective properties. They were synthesized from trans-cinnamic acids using a strategy combining Hunsdiecker-type bromodecarboxylation and the Suzuki cross-coupling reaction under microwave heating (Bazin et al., 2007). Bromodecarboxylation starting from 2,3,4-trimethoxycinnamic acid gave the corresponding β-bromostyrene intermediate, which allowed the Suzuki cross-coupling reaction with phenylboronic acid. The desired stilbene, (I), was obtained in 71% yield and we also observed 1,4-diarylbuta-1,3-diene, (II), as an unexpected homocoupling by-product (8% yield).
The asymmetric unit of compound (I) (Fig. 1a) contains one molecule and that of compound (II) (Fig. 1c) contains one half molecule, the remainder of (II) being generated by the symmetry centre situated at the midpoint of C8—C8i in the conjugated linkage [symmetry code: (i) -x, -y, -z].
For both compounds, the double bonds in the conjugated linkage are in the trans configuration. Futhermore, the observed double bonds are longer and the single bonds shorter (Tables 1 and 2) than the theoretical values (1.32 Å for double bonds and 1.51 Å for single bonds; Glusker et al., 1994), indicating the formation of a weak conjugated π-electron system.
In the stilbene structure, (I), the aromatic rings deviate significantly from a coplanar arrangement, with a dihedral angle of 16.92 (3)°. The origin of this deviation seems to be an intermolecular interaction occurring between neighbouring molecules rather than internal steric hindrance. A contact is observed between the benzene ring C11—H11 and atom O3ii of the methoxy group of a neighbouring molecule [symmetry code: (ii) -1/2 + x, 1/2 - y, 1/2 + z], with H11···O3ii = 2.473 (12) Å, C11···O3ii = 3.457 (1) ° and C11—H11···O3ii 173.6 (9)°. Among the three methoxy substituents of each aromatic ring, only that at C4 is approximately coplanar with the aromatic ring; the other two, at C5 and C6, are oriented towards opposite sides of the aromatic ring (Fig. 1b).
The core of the co-product structure, (II), is rigorously planar, as the two halves are related by a symmetry centre. As in compound (I), only one of the three methoxy substituents is approximately coplanar with the aromatic ring. The other two are again out of the plane on opposite sides.
In stilbene (I) there are two nearly edge-on (or T-shaped) stacking contacts (Fig. 2), one involving each of the two aromatic rings. Atom H14 of the unsubstituted phenyl is oriented toward the centroid Cg1i of its neighbour [symmetry code: (i) -1/2 - x, 1/2 + y, 1/2 - z], with H14···Cg1i = 2.765 (11) Å and C14—H14···.Cg1i = 136.2 (9)°. The second contact, between atom H8 of the double-bonded fragment and the substituted phenyl of a neighbour, is weak but appears to be directed; H8···Cg2iii = 3.23 (13) Å and C8—H8···Cg2iii = 166.7 (10)° [symmetry code: (iii) 1/2 - x, -1/2 + y, 1/2 - z]. As we have already described, a weak electrostatic H11···O3ii interaction is also present.
In the extended structure of co-product (II), only one significant contact was found, which consists of a T-shaped stacking interaction between the aromatic rings. C2—H2 contacts the centroid Cg1i of a neighbouring ring [symmetry code: (i) 1/2 - x, -1/2 + y, 1/2 - z], with H2···Cg1i = 2.837 (15) Å and C2—H2···Cg1i = 154.6 (11)°.
[Please define all Cg in terms of atom labels.]