(9.48 g, 43.68 mmol) gave the diene 1 in 48% (5.75 g,
20.95 mmol), as white crystals.
(dd, JHP = 15.0 Hz, J = 17.5 Hz, 2H), 3.03 (dd, JHP
=
8.9 Hz, J = 17.5 Hz, 2H), 2.27 (s, 6H), 1.80 (s, 6H); 13C NMR
(62.5 MHz, CDCl3) d 135.9 (2 Â C), 133.7 (C), 134.6 (C), 134.4
(C), 133.6 (d, JPC = 93.7 Hz, C), 133.5 (2 Â C), 132.2 (d,
This compound was also obtained by method (2), from
2,5-dimethylthiophene-3-boronic acid (3.43 g, 22 mmol) in
69% yield (1.89 g, 6.9 mmol).
JPC = 2.75 Hz, –CHQ), 130.9 (C), 130.7 (C), 129.6 (d, JPC =
Mp 36 1C; 1H NMR (250 MHz, CDCl3) d 6.45 (s, 2H), 5.06
(d, J = 1.1 Hz, 2H), 5.02 (d, J = 1.1 Hz, 2H), 2.33 (s, 6H),
2.24 (s, 6H); 13C NMR (62.5 MHz, CDCl3) d 144.3 (2 Â C),
137.5 (2 Â C), 134.9 (2 Â C), 132.8 (2 Â C), 127.6 (2 Â –CHQ),
118.3 (2 Â CH2Q), 15.2 (2 Â CH3–), 13.9 (2 Â CH3–). Anal.
Calc. for C16H18S2: C, 70.02; H, 6.61. Found: C, 69.92;
H 6.71%.
9.7 Hz, 2 Â –CHQ), 128.9 (d, JPC = 11.5 Hz, 2 Â –CHQ),
125.3 (2 Â –CHQ), 39.6 (d, JPC = 66.1 Hz, 2 Â –CH2–), 15.2
(2 Â CH3–), 14.2 (2 Â CH3–); 31P NMR (101.25 MHz, CDCl3)
d 50.45. Anal. Calc. for C22H23OPS2: C, 66.30; H, 5.82; S,
16.09; P, 7.77. Found: C, 66.21; H, 5.91; S, 16.17; P, 7.64%.
3,4-Bis(2-methylbenzo[b]thiophen-3-yl)-1-phenyl-2,5-dihydro-
phosphole 1-oxide: 4b. This compound was obtained by general
method (3), starting from 2,3-[bis(2-methylbenzo[b]thiophen-
3-yl)]buta-1,3-diene (838 mg, 2.42 mmol). The product was
2,3-[Bis(2-methylbenzo[b]thiophen-3-yl)]buta-1,3-diene:
2.
This compound was prepared by method (1): The Grignard
reagent was formed from 3-(a-bromovinyl)-2-methyl-
benzo[b]thiophene (13.82 g, 54.6 mmol) and magnesium
(1.59 g, 65.5 mmol), and subsequent conventional Kumada
coupling reaction of the latter with 3-(a-bromovinyl)-2-
methylbenzo[b]thiophene (11.06 g, 43.68 mmol) gave the diene
2 in 37% yield (5.6 g, 16.16 mmol), as a white powder.
This compound was also obtained by method (2), from
2-methylbenzo[b]thiophene-3-boronic acid (4.22 g, 22 mmol)
in 15% yield (519 mg, 1.5 mmol).
1
isolated as a yellowish solid (217 mg, 0.46 mmol, 19%). H
NMR (250 MHz, CDCl3) d 8.01–7.86 (m, 2H), 7.68–7.45 (m,
5H), 7.37–6.97 (m, 6H), 3.51 (dd, J = 16.3 Hz, J = 18.5 MHz,
2H), 3.13 (dd, J = 7.11 Hz, J = 18.3 Hz, 2H), 1.85 (s, 3H),
1.78 (s, 3H); 31P NMR (101.25 MHz, CDCl3) d 49.43. Anal.
Calc. for C28H23OPS2: C, 71.46; H, 4.93; S, 13.63; P, 6.58.
Found: C, 71.33; H, 4.87; S, 13.58; P, 6.52%.
General method (4) for the synthesis of silylated diaryl-
ethenes. An oven-dried resealable pressure tube containing a
stir bar, was charged with the appropriate diene (1 mmol),
trichlorosilane (542 mg, 4 mmol), tetrabutylphosphonium
chloride (29.5 mg, 0.1 mmol) and n-dodecane (2 mL), purged
with argon, and placed in a preheated oil-bath at 180 1C for
10 h. The reaction mixture was cooled to 0 1C and anhydrous
THF (5 mL) was added, followed by a 3 M solution of
methylmagnesium chloride in THF (4 mL, 12 mmol) with
vigorous stirring. The resulting mixture was stirred at room
temperature for 1 h. The reaction was quenched with 1 M
aqueous hydrochloric acid (15 mL), and extracted with Et2O
(3 Â 15 mL). The combined organic layers were dried over
MgSO4, filtered and concentrated under reduced pressure. The
crude residue was purified by column chromatography (SiO2;
eluent: n-hexane) to furnish the pure expected diarylethene.
The data for the individual compounds are given below.
Mp 156 1C; 1H NMR (250 MHz, CDCl3) d 7.73 (d, J = 7.5 Hz,
2H), 7.50 (d, J = 7.5 Hz, 2H), 7.40–7.15 (m, 4H), 5.17 (d, J =
1.1 Hz, 2H), 5.09 (d, J = 1.1 Hz, 2H), 2.50 (s, 6H); 13C NMR
(62.5 MHz, CDCl3) d 141.5 (2 Â C), 140.6 (2 Â C), 138.4 (2 Â C),
136.5 (2 Â C), 132.6 (2 Â C), 124.2 (2 Â –CHQ), 123.7 (2 Â
–CHQ), 122.4 (2 Â –CHQ), 122.0 (2 Â –CHQ), 120.9 (2 Â
CH2Q), 14.6 (2 Â CH3–). Anal. Calc. for C22H18S2: C, 76.26; H,
5.24. Found: C, 76.31; H, 5.19%.
General method (3) for the synthesis of phosphorylated
diarylethenes. A round-bottomed flask, equipped with a
magnetic stirrer, was charged with the appropriate diene
(2.42 mmol), dibromophenylphosphine (812 mg, 3.03 mmol)
and copper(II) stearate (5 mg) in petroleum ether (bp 60–80 1C),
10 mL), purged with argon and stirred for 10 days in
an oil-bath at 70 1C. The progress of the reaction was
monitored by TLC (pentane–diethyl ether, 1 : 1). After
complete disappearance of the diene, the reaction mixture
was allowed to come to ambient temperature, and was
quenched with saturated aqueous sodium bicarbonate solu-
tion (15 mL). The organic layer was separated and the aqueous
layer was extracted with dichloromethane (4 Â 15 mL). The
combined organic extracts were dried with MgSO4, filtered,
and then concentrated under vacuum. The crude residue was
purified by column chromatography (SiO2; cyclohexane–
AcOEt gradient 100 : 0 to 50 : 50) to provide the pure expected
phosphorylated diarylethenes. The data for the individual
compounds are given below.
3,4-Bis(2,5-dimethylthien-3-yl)-1,1-dimethyl-2,5-dihydro-1H-
silole: 5a. This compound was obtained by general method (4),
starting from 2,3-[bis(2,5-dimethylthien-3-yl)]buta-1,3-diene
(274 mg, 1 mmol). The product was isolated as white crystals
(296 mg, 0.89 mmol, 89%).
1
Mp 103 1C; H NMR (250 MHz, CDCl3) d 6.45 (s, 2H),
2.40 (s, 6H), 1.91 (s, 6H), 1.51 (s, 4H), 0.33 (s, 6H); 13C NMR
(62.5 MHz, CDCl3) d 141.6 (2 Â C), 136.7 (2 Â C), 136.5 (2 Â
C), 133.1 (2 Â C), 128.7 (2 Â –CHQ), 29.2 (–CH2–), 27.8
(–CH2–), 17.4 (2 Â CH3–), 16.3 (2 Â CH3–), À0.01 (2 Â
CH3–). Anal. Calc. for C18H24S2Si: C, 65.00; H, 7.27; S, 19.28.
Found: C, 65.12; H, 7.17; S, 19.31%.
3,4-Bis(2,5-dimethylthien-3-yl)-1-phenyl-2,5-dihydrophosphole
1-oxide: 4a. This compound was obtained by general
method (3), starting from 2,3-[bis(2,5-dimethylthien-3-yl)]
buta-1,3-diene (664 mg, 2.42 mmol). The product was isolated
as a pale yellow powder (569 mg, 1.43 mmol, 59%).
Mp 119 1C; 1H NMR (250 MHz, CDCl3) d 7.77–7.62
(m, 2H), 7.52–7.39 (m, 3H), 6.32 (s, 1H), 6.31 (s, 1H), 3.30
3,4-Bis(2-methylbenzo[b]thiophen-3-yl)-1,1-dimethyl-2,5-
dihydro-1H-silole: 5b. This compound was obtained by general
method (4), starting from 2,3-[bis(2-methylbenzo[b]thiophen-
3-yl)]buta-1,3-diene (346 mg, 1 mmol). The product was
isolated as white spangles (275 mg, 0.68 mmol, 68%).
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
1360 | New J. Chem., 2009, 33, 1357–1361