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C. Zheng et al. / Tetrahedron 63 (2007) 5437–5449
1.33 (m, 2H, –CH2), 1.62 (m, 2H, –CH2), 2.76 (t, 2H,
J¼7.6 Hz, –CH2), 7.53 (s, 1H, thiophene-H), 9.71 (s, 1H,
–CHO).
(376 MHz, TMS): d ꢁ110.51 (4F), ꢁ131.99 (2F); 13C
NMR (CDCl3, 100 MHz, TMS): d 13.70, 24.23, 31.07,
65.29, 99.92, 123.28, 125.83, 140.09, 149.13.
2.2.13. Synthesis of 4-bromo-5-n-propyl-2-(1,3-dioxo-
lane)thiophene (7c). Compound 6c (3.04 g, 13.03 mmol),
glycol (3.6 mL, 65.1 mmol), and p-toluenesulfonic acid
(0.05 g, 0.26 mmol) were dissolved in benzene (160 mL).
Under the Dean–Stark condition, the reaction mixture was
refluxed overnight, and then washed sequentially three times
with NaOH (3.0 mol/L) and water. The combined benzene
layers were dried, filtered, and evaporated in vacuum to
2.2.18. Synthesis of 1,2-bis{2-n-butyl-5-[2-(1,3-dioxo-
lane)]-3-thienyl}perfluorocyclopentene (8d). Compound
8d was prepared by a method similar to that used for 8c
1
(43% yield). H NMR (CDCl3, 400 MHz, TMS): d 0.74 (t,
6H, J¼7.2 Hz, –CH3), 1.14 (m, 4H, –CH2), 1.22 (m, 4H,
–CH2), 2.09 (t, 4H, J¼7.8 Hz, –CH2), 3.96 (t, 4H,
J¼6.8 Hz, –CH2), 4.04 (t, 4H, J¼6.8 Hz, –CH2), 5.94 (s,
2H, –CH–), 6.90 (s, 2H, thiophene-H).
1
give acetal 5 as yellow oil (2.6 g, 84% yield). H NMR
(CDCl3, 400 MHz, TMS): d 0.92 (t, 3H, J¼7.2 Hz, –CH3),
1.63 (m, 2H, –CH2), 2.66 (t, 2H, J¼7.6 Hz, –CH2), 3.94 (t,
2H, J¼6.6 Hz, –CH2), 4.05 (t, 2H, J¼6.8 Hz, –CH2), 5.93
(s, 1H, –CH–), 6.91 (s, 1H, thiophene-H).
2.2.19. Synthesis of 1,2-bis{2-n-pentyl-5-[2-(1,3-dioxo-
lane)]-3-thienyl}perfluorocyclopentene (8e). Compound
8e was prepared by a method similar to that used for 8c
1
(26% yield). H NMR (CDCl3, 400 MHz, TMS): d 0.77 (t,
6H, J¼7.2 Hz, –CH3), 1.27 (m, 8H, –CH2), 2.09 (m, 4H,
–CH2), 2.80 (t, 4H, J¼7.6 Hz, –CH2), 3.95 (t, 4H,
J¼6.8 Hz, –CH2), 4.03 (t, 4H, J¼6.8 Hz, –CH2), 5.93 (s,
2H, –CH–), 7.01 (s, 2H, thiophene-H).
2.2.14. Synthesis of 4-bromo-5-n-butyl-2-(1,3-dioxolane)-
thiophene (7d). Compound 7d was prepared by a method
similar to that used for 7c (78% yield). H NMR (CDCl3,
1
400 MHz, TMS): d 0.87 (t, 3H, J¼7.2 Hz, –CH3), 1.33 (m,
2H, –CH2), 1.56 (m, 2H, –CH2), 2.68 (t, 2H, J¼7.6 Hz,
–CH2), 3.93 (t, 2H, J¼6.4 Hz, –CH2), 4.04 (t, 2H,
J¼6.4 Hz, –CH2), 5.93 (s, 1H, –CH–), 6.89 (s, 1H, –CHO).
2.2.20. Synthesis of 1,2-bis{2-n-hexyl-5-[2-(1,3-dioxo-
lane)]-3-thienyl}perfluorocyclopentene (8f). Compound
8f was prepared by a method similar to that used for 8c
(17% yield). There is no structural analysis data for com-
pound 8f because it is very difficult to purify completely
and the unpurged compound 8f can be easily and directly
converted to diarylethene 6a by a hydrolyzing reaction.
2.2.15. Synthesis of 4-bromo-5-n-pentyl-2-(1,3-dioxolane)-
thiophene (7e). Compound 7e was prepared by a method
similar to that used for 7c (67% yield). H NMR (CDCl3,
1
400 MHz, TMS): d 0.83 (t, 3H, J¼6.4 Hz, –CH3), 1.29 (m,
4H), 1.58 (m, 2H, –CH2), 2.67 (t, 2H, J¼7.6 Hz, –CH2),
3.93 (t, 2H, J¼6.8 Hz, –CH2), 4.04 (t, J¼7.4 Hz, 2H,
–CH2), 5.93 (s, 1H, –CH–), 6.90 (s, 1H, thiophene-H).
2.2.21. Synthesis of 1,2-bis(2-n-propyl-5-formyl-3-thi-
enyl)perfluorocyclopentene (3a). Compound 8c (1.14 g,
2.00 mmol) and p-toluenesulfonic acid (0.4 g) were dis-
solved in mixture of water (30 mL) and acetone (90 mL);
2 mL pyridine was added into the mixture and reaction mix-
ture was refluxed for 24 h. After stopping the reaction, the
mixture was washed sequentially by aqueous NaHCO3 and
water. The organic layer was dried over anhydrous
Na2SO4, filtrated, and evaporated. The crude product was
purified by column chromatography on SiO2 using ethyl ace-
tate and petroleum ether mixture (v/v¼1/6) as the eluent to
give 0.8 g of compound 3a in 83% yield. The compound
crystallized from diethyl ether at room temperature and
produced the suitable crystals for X-ray analysis. Colorless
crystal: mp 100.7–101.2 ꢂC; MS m/z (M+) 479.0 (–H),
503.0 (+Na); Anal. Calcd for C21H18F6O2S2 (%): Calcd
C, 52.49; H, 3.78. Found C, 52.41; H, 3.59; 1H NMR
(CDCl3, 400 M Hz, TMS): d 0.75 (t, 6H, J¼7.4 Hz,
–CH3), 1.34 (m, 4H, –CH2), 2.18 (t, 4H, J¼7.8 Hz, –CH2),
7.65 (s, 2H, thiophene-H), 9.80 (s, 2H, –CHO); 19F NMR
(376 MHz, TMS): d ꢁ110.57 (4F), ꢁ131.85 (2F); 13C
NMR (CDCl3, 100 MHz, TMS): d 13.53, 24.17, 31.66,
124.94, 135.38, 142.28, 157.86, 181.74; IR (KBr, n,
cmꢁ1): 941, 1120, 1217, 12,661, 1329, 1461, 1539, 1670,
2928, 2976.
2.2.16. Synthesis of 4-bromo-5-n-hexyl-2-(1,3-dioxolane)-
thiophene (7f). Compound 7f was prepared by a method
similar to that used for 7c (88% yield). H NMR (CDCl3,
1
400 MHz, TMS): d 0.82 (t, 3H, J¼6.6 Hz, –CH3), 1.24 (m,
6H, –CH2), 1.56 (t, 2H, J¼7.6 Hz, –CH2), 2.67 (t, 2H,
J¼7.6 Hz, –CH2), 3.93 (t, 2H, J¼6.8 Hz, –CH2), 4.03 (t,
2H, J¼3.8 Hz, –CH2), 5.93 (s, 1H, –CH–), 6.89 (s, 1H, thio-
phene-H).
2.2.17. Synthesis of 1,2-bis{2-n-propyl-5-[2-(1,3-dioxo-
lane)]-3-thienyl}perfluorocyclopentene (8c). To a stirred
solution of compound 7c (2.60 g, 9.38 mmol) in THF,
1.6 mol/L n-BuLi/hexane (5.86 mL, 9.38 mmol) was added
at ꢁ78 ꢂC under nitrogen atmosphere. Stirring was con-
tinued for 40 min, perfluorocyclopentene (0.64 mL,
4.69 mmol) was slowly added to the reaction mixture, and
the mixture was stirred for 3.0 h at this low temperature.
The reaction was stopped by the addition of water. After ex-
tracting with ether, the organic layer was washed sequen-
tially by concentrated sodium chloride solution and water.
The organic layer was dried over anhydrous MgSO4, fil-
trated, and evaporated. The crude product was purified by
column chromatography on SiO2 using chloroform and
petroleum ether mixture (v/v¼1/1) as the eluent to give
2.2.22. Synthesis of 1,2-bis(2-n-butyl-5-formyl-3-thi-
enyl)perfluorocyclopentene (4a). Compound 4a was pre-
pared by a method similar to that used for 3a (80% yield).
Colorless crystal: mp 81.9–82.3 ꢂC; MS m/z (M+) 507.0
(–H), 531.1 (+Na); Anal. Calcd for C23H22F6O2S2 (%):
Calcd C, 54.32; H, 4.36. Found C, 54.43; H, 4.24; 1H
NMR (CDCl3, 400 MHz, TMS): d 0.82 (t, 6H, J¼7.2 Hz,
1
1.14 g of compound 8c in 42% yield. H NMR (CDCl3,
400 MHz, TMS): d 0.78 (t, 6H, J¼7.2 Hz, –CH3), 1.30 (m,
4H, –CH2), 2.14 (t, 4H, J¼7.6 Hz, –CH2), 3.44 (t, 4H,
J¼7.0 Hz, –CH2), 4.12 (t, 4H, J¼6.8 Hz, –CH2), 6.01
(s, 2H, –CH–), 7.09 (s, 2H, thiophene-H); 19F NMR