Syntheses of Dithienylcyclopentene Optical Molecular Switches
FULL PAPER
reaction without further workup because the product is hydrolyzed
during isolation.
(1.50 g, 4.12 mmol), Zn dust (0.53 g, 8.2 mmol) and THF (25 mL)
were stirred under nitrogen at 40 °C for 1 h. The mixture was co-
oled and poured through a glass filter containing silica gel that
was pretreated with petroleum ether. The silica was rinsed with
petroleum ether. A white solid (0.49 g, 55%) was obtained after
purification by chromatography on silica gel (petroleum ether),
1-[5-(5-Dodecylthien-2-yl)-2-methylthien-3-yl]-2-[(5-{5-[(methoxy-
carbonyl)methyl]thien-2-yl})-2-methylthien-3-yl]cyclopentene (23):
Methyl 2-(5-bromothien-2-yl)acetic acid (0.13 g, 0.55 mmol) was
dissolved in THF (12 mL) and Pd(PPh3)4 (53 mg, 3 mol %) was
added, this solution was stirred for 15 min at room temperature.
Then aq. Na2CO3 (6 mL, 2 ) and 6 drops of ethylene glycol were
added. This two-phase system was heated in an oil bath just below
reflux (60 °C) and the solution of 22 (0.55 mmol) in THF (5 mL)
was added dropwise via a syringe over a short time, followed by
reflux of the mixture for 4 h. After cooling, diethyl ether (100 mL)
and H2O (50 mL) were added. The organic layer was washed with
H2O (1 ϫ 20 mL), saturated aq. NH4Cl (1 ϫ 25 mL), a saturated
aq. bicarbonate solution (1 ϫ 25 mL), brine (2 ϫ 25 mL) and dried
(Na2SO4). After concentration, the compound was purified by col-
umn chromatography (hexane/ethyl acetate, 9:1) on silica to yield
an oil (0.12 g, 32%). 1H NMR (300 MHz, CDCl3): δ ϭ 0.87 (t, J ϭ
6.3, J ϭ 6.9, 3 H), 1.20Ϫ1.34 (m, 20 H), 1.58Ϫ1.71 (m, 2 H), 1.90
(s, 3 H), 1.91 (s, 3 H), 1.98- 2.09 (m, 2 H), 2.71Ϫ2.81 (m, 4 H),
3.73 (s, 3 H), 3.78 (s, 2 H), 6.62 (d, J ϭ 3.6 Hz, 1 H), 6.78 (d, J ϭ
3.9 Hz, 1 H), 6.80 (s, 1 H), 6.83 (d, J ϭ 3.3 Hz, 1 H), 6.84 (s, 1 H),
6.87 (d, J ϭ 3.3 Hz, 1 H) ppm. 13C NMR (CDCl3, 300 MHz): δ ϭ
14.1 (q), 14.3 (q), 22.7 (t), 22.9 (t), 29.1 (t), 29.3 (t), 29.5 (t), 29.6
(t), 30.1 (t), 31.6 (t), 31.9 (t), 35.4 (t), 38.5 (t), 52.3 (q), 122.5 (d),
123.63 (d), 124.3 (d), 124.5 (d), 127.5 (d), 132.9 (s), 133.3 (s), 133.6
(s), 133.9 (s), 134.3 (s), 134.6 (s), 135.1 (s), 136.1 (s), 136.3 (s), 137.6
(s), 144.4 (s), 144.7 (s), 170.7 (s) ppm. HRMS: calcd. for
C38H48O2S4 664.254, found 664.252.
1
m.p. 132 °C. H NMR (200 MHz, CDCl3): δ ϭ 1.88 (s, 6 H), 6.88
(s, 2 H) ppm. 13C NMR (500 MHz, CDCl3): δ ϭ 14.3 (q), 110.7
(t), 117.7 (t), 123.9 (d), 125.4 (s), 127.9 (s), 135.8 (s), 140.4 (s) ppm.
19F NMR (470.3 MHz, CDCl3): δ ϭ Ϫ114.78 (dd, J ϭ 5.5, 5.0 Hz,
4 F), Ϫ136.37 (dd, J ϭ 6.2, 5.0 Hz, 2 F) ppm. C15H8Cl2F6S2
(437.3): calcd. C 41.20, H 1.84; found C 41.25, H 1.87.
Acknowledgments
The Royal Netherlands Academy of Sciences is gratefully acknow-
ledged for a fellowship for J. v. E. The authors thank Patrick van
Rijn for his contribution to the synthetic work.
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fication (1.36 g, 70%). H NMR (200 MHz, CDCl3): δ ϭ 2.70 (s, 6
[25]
H), 7.31 (s, 2 H) ppm. 13C NMR (125.7 MHz, CDCl3): δ ϭ 17.1
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177.9 (s) ppm. 19F NMR (470.3 MHz, CDCl3): δ ϭ Ϫ116.18 (dd,
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165