Pd-mediated C-H arylation of EDOT and synthesis of push-pull systems incorporating EDOT

Article abstract of DOI:10.1016/j.tet.2007.07.037

The direct C-H arylation of 3,4-ethylenedioxythiophene (EDOT) is described under Heck-type experimental conditions. This methodology has been used to synthesize a series of push-pull systems containing EDOT units.

Full text of DOI:10.1016/j.tet.2007.07.037

Tetrahedron 63 (2007) 10363–10371
Pd-mediated C–H arylation of EDOT and synthesis of push–pull
systems incorporating EDOT
*
P. Amaladass, J. Arul Clement and Arasambattu K. Mohanakrishnan
Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025, Tamil Nadu, India
Received 18 April 2007; revised 28 June 2007; accepted 12 July 2007
Available online 19 July 2007
Abstract—The direct C–H arylation of 3,4-ethylenedioxythiophene (EDOT) is described under Heck-type experimental conditions. This
methodology has been used to synthesize a series of push–pull systems containing EDOT units.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
Our preliminary work on arylation of 3,4-ethylenedioxythio-
phene under Heck-type conditions has been recently pub-
lished.11 This simple and new method afforded various
arylated products in reasonable yields in contrast with the
usual arylation methods involving a metal-catalyzed cross-
coupling reaction of EDOT-metals and organic halides
(Kumada,12 Negishi,13 Stille,14 Suzuki15). Borghese and
co-workers also simultaneously reported similar arylation
of EDOT under Heck-type conditions.16
Organic electro-optical materials due to their intriguing pho-
tophysical properties have received prominent attention in
molecular electronic and optical devices.1 Over the years,
oligothiophenes are established as the most important elec-
tro-optical materials, which are used in the fabrication of
electroluminescent and semi-conducting devices. The re-
quired oligothiophenes are mostly prepared via palladium/
nickel mediated cross-coupling of either heteroaryl halides
with aryl metals or aryl halides with heteroaryl metals.2
However, the direct arylation of thiophene bearing elec-
tron-withdrawing groups was reported by Lemaire and
co-workers.3 It is also known that aryl halides/heteroaryl
halides can couple directly with thiophene bearing electron-
releasing groups at the reactive 2- and/or 5-position.4 The
regioselective arylation of methylthiophene-3-carboxylate
by an aryl bromide, catalyzed by Pd(PPh3)4 has been
reported.5 The synthesis of 2-arylthiophene via CuI or
MnBr2 catalyzed cross-coupling of 2-thienyltributylstan-
nane with aryl halides has also been reported.6 Yokooji
et al. reported a straightforward synthesis of 5,50-diarylated-
2,20-bithiophene via a palladium catalyzed arylation.7 Mori
and co-workers recently reported the synthesis of donor–
acceptor type 2,5-diarylthiophenes via palladium mediated
sequential arylation reaction.8 The 3,4-ethylenedioxythio-
phene (EDOT) has been used as a building block in several
conjugated systems that incorporate unique properties
such as electrochromic behavior9 and in low band gap
polymers.10
Roncali and co-workers reported the synthesis of stable and
soluble oligo(3,4-ethylenedioxythiophenes),17 and also the
synthesis of thienylvinylenes incorporating EDOT units.18
Very recently, a direct arylation of heteroarenes including
3-methoxythiophene was reported with aryl iodides using
rhodium catalyst.19 Roncali and co-workers reported the
synthesis of 3,4-ethylenedioxythiophene (EDOT) tethered
symmetrical benzo[c]thiophene derivative,20 and also re-
ported the synthesis of push–pull chromophores.21 Since
a large number of thiophene oligomers have recently been
explored as push–pull type systems,21,22 we decided to ex-
plore our synthetic design of the NLO materials exploiting
high electron-rich system of the EDOT. The low yield
obtained during cross-coupling of EDOT-metals15 with
aryl halides also encouraged us to undertake the present
investigation. Hence, the coupling reaction of EDOT was
carried out with a variety of aryl/heteroaryl halides. The
resulting arylated EDOTs are converted into the respective
push–pull systems and the detailed results have been
described.
2. Results and discussions
Keywords: EDOT; Arylation; Thienylvinylene; Heteroarylation.
* Corresponding author. Tel.: +91 44 24451108; fax: +91 44 22352494;
e-mail: mohan_67@hotmail.com
As mentioned in Section 1, there is only one report on
EDOT incorporated benzo[c]thiophene derivative.20 In
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.07.037

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P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
continuation of our interest on benzannelated thienyl oligo-
mers,23 initially, an attempt was made to incorporate EDOT
unit on the benzo[c]thiophene skeleton using either 3,4-
ethylenedioxy thiophenyl-2-magnesium bromide (Kumada)
or 3,4-ethylenedioxythiopheneyl-2-zinc bromide (Negishi)
or using stable 2-tributylstannyl-3,4-ethylenedioxythio-
phene (Stille) or pinacolboronic ester of 3,4-ethylenedioxy-
thiophene (Suzuki) and known bromo compound 2 in the
presence of various catalysts [Pd(PPh3)4, Pd(PPh3)Cl2, and
Pd(dba)3] without any success, Scheme 1.
Pd(PPh3)4. Usual workup and purification of the crude prod-
uct led to the isolation of mono- and bis-arylated products 8a
and 9a in 30 and 20% yields, respectively. The isolation of
compound 9a prompted us to explore the direct arylation
of EDOT. Thus, the direct arylation of EDOT with 4-iodo-
anisole in the presence of Pd(PPh3)4 and K2CO3 in DMF
at 80 ꢀC for 14 h afforded the corresponding mono-arylated
product 8a in reasonable yield, Scheme 3.
However, all attempts to couple either 1-(5-bromothiophen-
2-yl)-3-(thiophen-2-yl)benzo[c]thiophene 2 or 1,3-bis(5-
iodothiophen-2-yl)benzo[c]thiophene 4 with EDOT were
unsuccessful. The arylation reactions of EDOT were per-
formed in dry DMF in the presence of K2CO3 and catalytic
amounts of Pd(PPh3)4 at 80 ꢀC using either aryl iodide or
bromide. The use of acetonitrile or THF as a solvent in place
of DMF did not afford any arylated products. The selectivity
observed in the polar solvent (DMF) for the arylation could
be due to the ionization of the Ar–Pd–X into the Ar–Pd+ Xꢁ.
The electrophilic Ar–Pd+ Xꢁ species would react at the
electron-rich 2-position of the 3,4-ethylenedioxythiophene,
affording the cationic intermediate 10b, which on proton
abstraction followed by subsequent reductive elimination
would afford the arylated product 10d, Scheme 4.
Kisselev and Thelakkat recently reported Pd-catalyzed
(Pd(dppf)Cl2 or Pd2(dba)3) coupling of 1,2-bis(5-iodo-2-thi-
enyl)isothianaphthene 4 with secondary amines.24 However,
all our attempts to incorporate EDOT unit on the benzo[c]-
thiophene skeleton using pinacolboranate ester of EDOT
and iodo compound 4 in the presence of Pd(PPh3)4 or
Pd(PPh3)2Cl2 were unsuccessful, Scheme 2.
Having failed to incorporate the EDOT unit into the benzo-
[c]thiophene skeleton, we have turned our focus on the cou-
pling of EDOTwith simple aryl halides. As a model reaction,
we have carried out coupling reaction of pinacol boronate
ester of EDOT 1 with 4-iodoanisole in the presence of
O
O
O
O
Pd
X
S
+
S
S
S
X
S
S
S
S
Br
1
2
3
X = MgBr, ZnCl
SnBu3, B(OR)2
Scheme 1.
S
Pd
X
1
S
S
+
S
O
O
S
S
I
I
S
S
O
O
4
5
Scheme 2.
O
O
I
OMe
O
O
7a
MeO
OMe
O
8a
+
S
9a
B
O
S
Pd(PPh3)4
K2CO3/DMF/80 °C
30%
O
20%
6
O
O
O
7a
Pd(PPh3)4
K2CO3/DMF/80 °C
OMe
S
10
S
8a
42%
Scheme 3.

P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
10365
The yield of the arylated products was not significantly
changed by using different bases such as Cs2CO3 or
K3PO4 in the place of K2CO3. The use of bromoaryl or
iodoaryl compounds did not have much effect on the yield
of the arylated products. A minor amount (5–10%) of the
starting material (EDOT) was always recovered even on
an extended reaction time without any appreciable change
in the yield of the arylated products. The 5,50-dibromo-
2,20-bithiophene 7h underwent a smooth bis-arylation
with EDOT to afford the coupled product 8h in 40% yield.
It should be noted that the same product was obtained in
relatively very low yield (20%) involving a cross-coupling
between pinacol boronate ester of EDOT 7 and 2,5-dibromo-
thiophene.21 The fluorenyl dibromo compound 7i
afforded the respective coupled product 8i in 45% yield,
Table 2.
O
O
O
O
O
O
Pd-Ar
Ar-Pd x
S
S
10
H
S
10a
10b
B
O
O
O
O
B
Ar
S
Pd-Ar
S
10d
10c
Pd0
Scheme 4. Mechanistic pathway for EDOT arylation.
Among the three palladium catalysts [Pd(PPh3)4,
Pd(PPh3)2Cl2, and Pd2(dba)3] employed for arylation of
EDOT, Pd(PPh3)4 was found to be the most suitable one.
We also observed that aryl halides bearing electron-
withdrawing groups react faster than aryl halides containing
electron-donating groups. The results of coupling reaction of
EDOT with aryl halides bearing electron-withdrawing
groups are presented in Table 1.
The electron-rich aromatic halides 7a and 7j–l afforded the
corresponding arylated products 8a and 8j–l in relatively
less yields. Moreover, the reaction temperature and the reac-
tion time are high compared to electron-deficient aromatic
halides. The results of coupling reaction of EDOT with
aryl halides bearing electron-donating groups are presented
in Table 3.
The bis-arylation of EDOT was carried out with 2 equiv of
aryl halides 7a–m and the results are summarized in Table 4.
Table 1. Mono-arylation of 3,4-EDOT with aryl halides bearing electron-
withdrawing groups
The electron-deficient aromatic halides 7b and 7c afforded
the corresponding bis-arylated products 9b and 9c in 40
and 35% yields, respectively. Similar to mono-arylation,
the reaction temperature and the reaction time are also less
compared to electron-rich aromatic halides 7a and 7m.
The structure of 2,5-bis(benzo[b]-2-thienyl)EDOT 9m was
confirmed by X-ray analysis25 (Fig. 1).
Entry
Ar–X
Product
Temp Yielda
(ꢀC);
(%);
time (h) mp (ꢀC)
O
O
I
NO2
1
65; 8
60; 8
55; 158
50; 92
NO2
S
7b
8b
Finally, arylation of 2,20-bis(EDOT) 11 with 4-methoxyiodo-
benzene 7a in dry DMF at 80 ꢀC for 14 h led to the isolation
of mono-arylated product 12 in 30% yield, Scheme 5. All at-
tempts to couple bis(EDOT) 11 with other aryl/heteroaryl
halo compounds are found to be unsuccessful, Scheme 5.
O
O
NO2
2
I
S
7c
O2N
8c
O
O
The push–pull system containing EDOTas a conjugated sys-
tem is regarded as potential non-linear optical material.
Hence, the synthesis of 3,4-ethylenedioxythiophene analogs
having an electron acceptor group at one end and a donor
group at the opposite end is planned. To realize the above-
mentioned objective, the mono-arylated products 8a, 8j,
and 8k were formylated under the Vilsmeier–Haack condi-
tion to afford the corresponding mono-aldehydes 13–15 in
60–80% yields, Scheme 6. Condensation of these aldehydes
with malononitrile/thiopheneacetonitrile led to the forma-
tion of corresponding cyano derivatives 16–20 in 40–65%
yields, Scheme 7.
Br
CHO
3
4
60; 10 50; 122
CHO
S
7d
8d
O
O
Br
COCH3
65; 8
52; 118
COCH3
S
8e
7e
O
O
Br
5
80; 10 35; 125
N
S
N
7f
Finally, olefin tethered extended system of 16 was prepared.
The Wittig reaction of 4-methoxybenzylphosphonium salt
with known 3,4-ethylenedioxythiophene aldehyde afforded
the corresponding vinylene 21. The Vilsmeier–Haack
formylation of the latter afforded aldehyde 22 in 55% yield.
Condensation of aldehyde 22 with thiophene-2-acetonitrile
using t-BuOK in ethanol led to the push–pull system 23 in
51% yield, Scheme 8.
8f
O
O
6
80; 10 34; 70
N
Br
S
N
8g
7g
a
Isolated yield after column chromatography.

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P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
Table 2. Synthesis of EDOT-based oligothiophenes
Entry
1
Ar–X
Product
Temp (ꢀC); time (h)
Yielda (%); mp (ꢀC)
O
O
O
O
Br
Br
80; 10
40; 190
S
S
S
S
S
S
7h
8h
O
O
O
O
Br
Br
2
80; 12
45; 105
C6H13
S
C6H13
S
C6H13
C6H13
7i
8i
a
Isolated yield after column chromatography.
Table 3. Mono-arylation of EDOT using aryl halides bearing electron-releasing groups
Entry
Ar–X
Product
Temp (ꢀC); time (h)
Yielda (%); mp (ꢀC)
O
O
O
I
OCH3
CH3
1
80; 14
42; 75
MeO
H3C
S
8a
7a
O
I
2
3
80; 12
80; 12
45; Liquid
40; 120
S
7j
8j
Br
O
O
MeO
S
8k
7k
MeO
Br
O
O
4
60; 12
40; 192
S
8l
7l
a
Isolated yield after column chromatography.
Table 4. Bis-arylation of EDOT
Entry
Ar–X
Product
Temp (ꢀC); time (h)
80; 13
Yielda (%); mp (ꢀC)
O
O
I
OCH3
1
35; 160
MeO
O2N
OMe
S
7a
9a
O
O
I
NO2
2
3
80; 10
80; 10
40; 155
35; 166
NO2
S
9b
7b
O
O
NO2
I
S
7c
NO2 9c O2N
O
O
I
4
70; 8
50; 165
S
S
S
9m
S
7m
Isolated yield after column chromatography.
a

P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
10367
Figure 1. ORTEP style plot of compound 9m in thermal ellipsoids drawn at the 50% probability level.
OMe
I
OMe
O
O
S
O
O
i) n-BuLi/EtOH
O
O
S
O
O
O
MeO
7a
O
O
O
Pd(PPh3)4
S
S
21
Br
S
ii)
OCH3
K2CO3/DMF, 80 °C
30%
CHO
PPh3
12
S
11
60%
Scheme 5.
O
O
O
O
DMF/POCl3
55%
MeO
CHO
S
22
O
O
CN
DMF/POCl3
CN
S
8a, 8j
R
S
CHO
DCM
S
t-BuOK/EtOH
51%
S
H3CO
13 R = OMe (72%)
14 R = Me (60%)
23
Scheme 8.
O
O
DMF/POCl3
DCM
CHO
8k
S
15
3. UV–vis spectroscopy
80%
H3CO
The electronic absorption data of the arylated products and
cyanovinylenes are listed in Table 5.
Scheme 6.
The UV–vis spectra are characterized by a well-resolved fine
structure with EDOT median core. The arylated products of
O
O
CN
CN
S
CN
S
S
16
H3CO
13
Table 5. Electronic absorption data (DCM)
t-BuOK/EtOH
62%
Compound
lmax (DCM)
O
O
8a
8b
8c
8d
8e
8k
8l
9b
9m
16
17
18
20
23
301
376
345
445
335
318
370
374
395
435
377
379
365
460
NC
CN
CN
S
13 or 14
R
t-BuOK/EtOH
18 R = OMe (51%)
19 R = Me (56%)
O
O
CN
Ar
Ar
CN
S
15
MeO
t-BuOK/EtOH
17 Ar = 2-Thienyl (65%)
20 Ar = 3,4-Dimethoxyphenyl (42%)
Scheme 7.

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P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
EDOT containing electron-withdrawing group produce
a slight bathochromic shift of the absorption bands
compared to EDOT containing electron-releasing group.
On the other hand, comparison of these data shows that
replacement of electron-withdrawing group by electron-
releasing group in arylated products produces a >30–
60 nm shift of the absorption bands. The UV–vis spectra
of thienylvinylene incorporating EDOT units show lmax
value greater than 400 nm, which indicates the bathochro-
mic shift of the absorption bands.
8b was obtained as a yellow solid (0.30 g, 55%); mp
1
158 ꢀC; H NMR (400 MHz, CD3COCD3): dH 4.19–4.21
(2H, m, OCH2), 4.28–4.30 (2H, m, OCH2), 6.38 (1H, s,
EDOT), 8.09 (2H, d, J¼8.8 Hz, CHAPh), 8.26 (2H, d,
J¼8.4 Hz, CHBPh); 13C NMR (100.6 MHz, CD3COCD3):
dC 64.28, 65.00, 100.97, 115.14, 124.03, 124.35, 125.66,
128.30, 140.61, 144.95; mass m/z: 263 (M+). Anal. Calcd
for C12H9NSO4: C, 54.75; H, 3.45; N, 5.32; S, 12.18. Found:
C, 54.64; H, 3.52; N, 5.38; S, 12.10.
5.2.3. 2,3-Dihydro-5-(2-nitrophenyl)thieno[3,4-b][1,4]di-
oxine (8c). Following the general procedure, compound 8c
was obtained as a yellow solid (0.23 g, 50%); mp 92 ꢀC;
1H NMR (400 MHz, CD3COCD3): dH 4.13–4.18 (4H, m,
OCH2), 6.59 (1H, s, EDOT), 7.53 (2H, m, Ph), 7.67–7.69
(1H, m, Ph), 7.89 (1H, d, J¼8.28 Hz, Ph); 13C NMR
(100.6 MHz, CD3COCD3): dC 65.21, 65.31, 100.89,
111.84, 125.48, 127.03, 129.26, 132.71, 133.57, 140.22,
142.59, 149.98; mass m/z: 263 (M+). Anal. Calcd for
C12H9NO4S: C, 54.75; H, 3.45; S, 12.18; N, 5.32. Found:
C, 54.66; H, 3.30; S, 12.29; N, 5.25.
4. Conclusions
The syntheses of a variety of mono- and bis-arylated EDOT
analogs have been achieved in moderate yields, involving
direct Heck arylation of EDOT with various aryl and hetero-
aryl halides. The synthesis of push–pull systems containing
3,4-ethylenedioxythiophenes has been achieved in good
yield.
5. Experimental
5.1. General
5.2.4. 4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-7-yl)benz-
aldehyde (8d). Following the general procedure, compound
8d was obtained as a white solid (0.43 g, 50%); mp 122 ꢀC;
1H NMR (400 MHz, CD3COCD3): dH 4.25–4.27 (4H, m,
OCH2), 6.51 (1H, s, EDOT), 7.72 (2H, d, J¼8.21 Hz,
CHAPh), 8.13 (2H, d, J¼8.21 Hz, CHBPh), 9.97 (1H, s,
CHO); 13C NMR (100.6 MHz, CD3COCD3): dC 64.26,
64.85, 100.13, 116.13, 125.72, 130.27, 133.93, 139.24,
140.03, 142.37; mass m/z: 246 (M+). Anal. Calcd for
C13H10O3S: C, 63.40; H, 4.09; S, 13.02. Found: C, 63.52;
H, 4.02; S, 12.98.
All melting points are uncorrected. IR spectra were recorded
on a Shimadzu FT-IR 8300 instrument. H and 13C NMR
1
spectra were recorded in CDCl3 using TMS as an internal
standard on a Jeol 400 spectrometer at 400 and 100 MHz
and Bruker spectrometer at 300 and 75 MHz, respectively.
Mass spectra were recorded on a Jeol DX 303 HF spectro-
meter. Elemental analyses were carried out on a Perkin–
Elmer 240 B instrument.
5.2.5. 1-(4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-7-yl)-
phenyl)ethanone (8e). Following the general procedure,
compound 8e was obtained as a white solid (0.68 g, 52%);
mp 118 ꢀC; 1H NMR (400 MHz, CD3COCD3): dH 2.53
(3H, s, CH3), 4.27–4.35 (4H, m, OCH2), 6.54 (1H, s, EDOT),
7.79 (2H, d, J¼8.32 Hz, CHAPh), 7.95 (2H, d, J¼8.32 Hz,
CHBPh); 13C NMR (100.6 MHz, CD3COCD3): dC 26.52,
65.13, 65.85, 100.32, 116.24, 125.92, 129.54, 135.65,
138.58, 141.0, 143.61, 197.16; mass m/z: 260 (M+). Anal.
Calcd for C14H12SO3: C, 64.60; H, 4.65; S, 12.32. Found:
C, 64.71; H, 4.56; S, 12.25.
5.2. A representative procedure for mono-arylation
5.2.1. 2,3-Dihydro-5-(4-methoxyphenyl)thieno[3,4-
b][1,4]dioxine (8a). A two-necked flask containing 4-iodo-
anisole 8a (0.5 g, 2.13 mmol), EDOT (0.3 g, 2.11 mmol),
Pd(PPh3)4 (246 mg, 0.21 mmol), and K2CO3 (0.34 g,
2.52 mmol) was evacuated. To this, dry DMF (10 mL) was
added via syringe. The reaction mixture was allowed to
stir at 80 ꢀC for 14 h. Then, the mixture was cooled to
room temperature and passed through a Celite pad, which
was successively washed with chloroform. The filtrate was
washed with water and the aqueous layer was extracted
with chloroform. The combined organic layer was extracted
with anhydrous sodium sulfate and concentrated under
pressure to leave a crude residue. Purification by chro-
matography on silica gel (hexane–EtOAc 9:1) afforded
0.22 g of 8a as a colorless solid (42%); mp 75 ꢀC; 1H
NMR (400 MHz, CD3COCD3): dH 3.71 (3H, s, OCH3),
4.22–4.31 (4H, m, OCH2), 6.33 (1H, s, EDOT), 6.61 (2H,
d, J¼8.8 Hz, CHAPh), 7.61 (2H, d, J¼8.8 Hz, CHBPh);
mass m/z: 248 (M+); 13C NMR (100.6 MHz, CD3COCD3):
dC 55.35, 64.50, 64.73, 96.45, 114.10, 114.21, 125.98,
127.44, 127.74, 158.44, 158.75. Anal. Calcd for
C13H12SO3: C, 62.88; H, 4.87; S, 12.91. Found: C, 62.66;
H, 4.96; S, 12.79.
5.2.6. 3-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-7-yl)quino-
line (8f). Following the general procedure, compound 8f
was obtained as a white solid (0.26 g, 35%); mp 125 ꢀC;
1H NMR (400 MHz, CDCl3): dH 4.20–4.22 (2H, m,
OCH2), 4.28–4.31 (2H, m, OCH2), 6.33 (1H, s, EDOT),
7.41 (1H, t, J¼7.4 Hz, ArH), 7.61 (1H, t, J¼7.6 Hz, ArH),
7.71 (1H, d, J¼8 Hz, ArH), 8.05 (1H, d, J¼8.40 Hz, ArH),
8.32 (1H, s, ArH), 9.2 (1H, d, J¼4.0 Hz, ArH); 13C NMR
(100.6 MHz, CDCl3): dC 64.4, 64.9, 99.1, 113.9, 126.7,
126.9, 127.8, 127.9, 128.9, 129.2, 131.1, 139.5, 142.4, 146.5,
148.7; mass m/z: 269 (M+). Anal. Calcd for C15H11NO2S: C,
66.89; H, 4.12; N, 5.20; S, 11.91. Found: C, 66.78; H, 4.20;
N, 5.26; S, 12.01.
5.2.7. 2-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-7-yl)pyri-
dine (8g). Following the general procedure, compound 8g
was obtained as a white solid (0.52 g, 34%); mp 70 ꢀC; 1H
5.2.2. 2,3-Dihydro-5-(4-nitrophenyl)thieno[3,4-b][1,4]-
dioxine (8b). Following the general procedure, compound

P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
10369
NMR (300 MHz, CDCl3): dH 4.32–4.35 (4H, m, OCH2),
6.36 (1H, s, EDOT), 7.34 (1H, d, J¼5.8 Hz, ArH), 7.67 (2H,
m, ArH), 7.91 (1H, d, J¼5.8 Hz, ArH); mass m/z: 219 (M+).
Anal. Calcd for C11H9NO2S: C, 60.26; H, 4.14; N, 6.39; S,
14.62. Found: C, 60.15; H, 4.20; N, 6.35; S, 14.72.
room temperature and passed through a Celite pad, which
was successively washed with chloroform. The filtrate was
washed with water and the aqueous layer was extracted
with chloroform. The combined organic layer was extracted
with anhydrous sodium sulfate and concentrated under pres-
sure to leave a crude residue. Purification by chromato-
graphy on silica gel (hexane–EtOAc 9:1) afforded (0.20 g,
30%) 12 as a yellow solid; mp 135 ꢀC; 1H NMR
(400 MHz, CD3COCD3): dH 3.81 (3H, s, OCH3), 4.26–
4.37 (8H, m, OCH2), 6.31 (1H, s, BEDOT), 6.90 (2H, d,
J¼9.28 Hz, CHAPh), 7.60 (2H, d, J¼8.82 Hz, CHBPh);
mass m/z: 388 (M+). Anal. Calcd for C19H16O5S2: C,
58.75; H, 4.15; S, 16.51. Found: C, 58.67; H, 4.26; S, 16.60.
5.2.8. 2,3-Dihydro-5-(5-(5-(2,3-dihydrothieno[3,4-b]-
[1,4]dioxin-7-yl)thiophen-2-yl)thiophen-2-yl)thieno[3,4-
b][1,4]dioxine (8h). Following the general procedure,
compound 8h was obtained as a red solid (0.11 g, 40%);
mp 190 ꢀC; 1H NMR (300 MHz, CDCl3): dH 4.25–4.27
(m, 4H, OCH2), 4.36–4.68 (m, 4H, OCH2), 6.23 (2H, s,
EDOT), 7.07 (2H, d, J¼3.8 Hz, thiophene), 7.11 (2H, d,
J¼3.9 Hz, thiophene); mass m/z: 445 (M+). Anal. Calcd
for C20H14O4S4: C, 53.79; H, 3.16; S, 28.72. Found: C,
53.93; H, 3.21; S, 27.61.
5.3. A representative procedure for bis-arylation
5.3.1. 2,3-Dihydro-5,7-bis(4-nitrophenyl)thieno[3,4-
b][1,4]dioxine (9b). A two-necked flask containing 4-iodo
nitrobenzene 8b (1.75 g, 7.04 mmol), EDOT (0.5 g,
3.52 mmol), Pd(PPh3)4 (810 mg, 0.70 mmol), and K2CO3
(1.06 g, 7.74 mmol) was evacuated. To this, dry DMF
(10 mL) was added via syringe. The reaction mixture was al-
lowed to stir at 80 ꢀC for 14 h. Then, the mixture was cooled
to room temperature and passed through a Celite pad, which
was successively washed with chloroform. The filtrate was
washed with water and the aqueous layer was extracted
with chloroform. The combined organic layer was extracted
with anhydrous sodium sulfate and concentrated under pres-
sure to leave a crude residue. Purification by chromato-
graphy on silica gel (hexane–EtOAc 9:1) afforded (0.54 g,
40%) 9b as a yellow solid; mp 155 ꢀC; 1H NMR
(300 MHz, CDCl3): dH 4.45 (4H, s, OCH2), 7.75 (4H, d,
J¼8.7 Hz, CHAPh), 8.30 (4H, d, J¼8.4 Hz, CHBPh); 13C
NMR (75 MHz, CDCl3): dC 64.58, 115.17, 124.04, 128.31,
140.61, 145.50, 148.10; mass m/z: 384 (M+). Anal. Calcd
for C18H12N2O6S: C, 56.25; H, 3.15; N, 7.29; S, 8.34. Found:
C, 56.36; H, 3.22; N, 7.16; S, 8.25.
5.2.9. 5-(9,9-Dihexyl-2-(2,3-dihydrothieno[3,4-b][1,4]-
dioxin-7-yl)-9H-fluoren-7-yl)-2,3-dihydrothieno[3,4-
b][1,4]dioxine (8i). Following the general procedure,
compound 8i was obtained as a yellow solid (0.38 g,
1
45%); mp 105 ꢀC; H NMR (400 MHz, CD3COCD3): dH
0.72 (6H, t, J¼6.84 Hz, CH3), 1.02–1.20 (16H, m, CH2),
2.90–2.93 (4H, m, CH2), 4.26–4.37 (8H, m, OCH2), 6.43
(2H, s, EDOT), 7.71–7.80 (6H, m, Ph); 13C NMR
(100.6 MHz, CD3COCD3): dC 14.33, 23.22, 24.66, 30.74,
41.03, 56.07, 65.39, 65.92, 98.24, 118.38, 120.81, 120.93,
125.82, 133.33, 139.54, 140.34, 143.73, 152.15; mass m/z:
614 (M+). Anal. Calcd for C37H42O4S2: C, 72.28; H, 6.89;
S, 10.43. Found: C, 72.15; H, 6.77; S, 10.52.
5.2.10. 2,3-Dihydro-5-(2-methoxynaphthalen-6-yl)thi-
eno[3,4-b][1,4]dioxine (8k). Following the general proce-
dure, compound 8k was obtained as a white solid (0.41 g,
1
40%); mp 120 ꢀC; H NMR (400 MHz, CDCl3): dH 3.0
(3H, s, OCH3), 3.38–3.45 (4H, m, OCH2), 6.18–6.20 (2H,
m, Ph), 6.22 (1H, s, EDOT), 6.78–6.92 (4H, m, Ph); 13C
NMR (100.6 MHz, CDCl3): dC 54.23, 64.03, 63.85,
104.89, 112.36, 118.18, 122.56, 122.93, 124.22, 126.18,
127.03, 128.04, 128.30, 128.45, 132.29, 137.27, 137.61;
mass m/z: 298 (M+). Anal. Calcd for C17H14SO3: C,
68.44; H, 4.73; S, 10.75. Found: C, 68.37; H, 4.69; S, 10.82.
5.3.2. 2,3-Dihydro-5,7-bis(2-nitrophenyl)thieno[3,4-
b][1,4]dioxine (9c). Following the general procedure, com-
pound 9c was obtained as a yellow solid (0.47 g, 35%); mp
166 ꢀC; 1H NMR (300 MHz, CDCl3): dH 4.08 (4H, s,
OCH2), 7.33–7.39 (2H, m, Ph), 7.47–7.55 (4H, m, Ph),
7.79 (2H, d, J¼7.8 Hz, Ph); 13C NMR (75 MHz, CDCl3):
dC 64.43, 112.22, 124.90, 125.93, 128.00, 128.36, 131.76,
132.13, 132.60, 138.88, 148.95; mass m/z: 384 (M+).
Anal. Calcd for C18H12N2O6S: C, 56.25; H, 3.15; N, 7.29;
S, 8.34. Found: C, 56.37; H, 3.07; N, 7.38; S, 8.26.
5.2.11. 5-(Anthracen-10-yl)-2,3-dihydrothieno[3,4-b]-
[1,4]dioxine (8l). Following the general procedure, com-
pound 8l was obtained as a brown solid (0.17 g, 40%); mp
1
192 ꢀC; H NMR (500 MHz, CDCl3): dH 4.13 (2H, br s,
OCH2), 4.26 (2H, br s, OCH2), 6.67 (1H, s, EDOT), 7.48
(4H, br s, CHAPh), 7.91–8.01 (4H, m, CHBPh), 8.53 (1H,
s, CHCPh); 13C NMR (125 MHz, CDCl3): dC 64.80, 64.87,
100.00, 112.47, 126.21, 126.59, 128.46, 128.67, 131.52,
132.07, 139.12, 141.12; mass m/z: 318 (M+). Anal. Calcd
for C20H14O2S: C, 75.45; H, 4.43; S, 10.07. Found: C,
75.39; H, 4.38; S, 10.11.
5.3.3. 5,7-Di(benzo[b]thiophen-2-yl)-2,3-dihydro-
thieno[3,4-b][1,4]dioxine (9m). Following the general pro-
cedure, compound 9m was obtained as a green solid (0.71 g,
1
50%); mp 165 ꢀC; H NMR (300 MHz, CDCl3): dH 4.43
(4H, s, OCH2), 7.25–7.35 (4H, m, Ph), 7.50 (2H, s, ArH),
7.70–7.79 (4H, m, ArH); 13C NMR (75 MHz, CDCl3): dC
65.01, 110.94, 119.44, 121.98, 122.18, 123.21, 124.61,
134.26, 138.81, 139.05, 139.95. mass m/z: 406 (M+).
Anal. Calcd for C22H14O2S3: C, 65.00; H, 3.47; S, 23.66.
Found: C, 65.20; H, 3.39; S, 23.59.
5.2.12. 2,3-Dihydro-5-(2,3-dihydro-5-(4-methoxyphe-
nyl)thieno[3,4-b][1,4]dioxin-7-yl)thieno[3,4-b][1,4]diox-
ine (12). A two-necked flask containing 4-iodoanisole
8a (1.41 g, 1.77 mmol), BEDOT 11 (0.5 g, 1.77 mmol),
Pd(PPh3)4 (200 mg, 0.17 mmol), and K2CO3 (0.3 g,
2.17 mmol) was evacuated. To this, dry DMF (10 mL) was
added via syringe. The reaction mixture was allowed to
stir at 80 ꢀC for 14 h. Then, the mixture was cooled to
5.3.4. 2,3-Dihydro-5,7-bis(4-methoxyphenyl)thieno[3,4-
b][1,4]dioxine (9a). Following the general procedure, com-
pound 9a was obtained as a colorless solid (0.53 g, 35%); mp

10370
P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
160 ꢀC; 1H NMR (400 MHz, CDCl3): dH 3.82 (6H, s,
OCH3), 4.38 (4H, s, OCH2), 6.95 (4H, d, J¼8.82 Hz,
CHAPh), 7.65 (4H, d, J¼8.82 Hz, CHBPh); 13C NMR
(100.6 MHz, CDCl3): dC 55.33, 64.57, 97.54, 114.51,
125.87, 127.35, 137.63, 158.30; mass m/z: 354 (M+).
Anal. Calcd for C20H18O4S: C, 67.78; H, 5.12; S, 9.05.
Found: C, 67.67; H, 4.98; S, 9.16.
mixture of aldehyde 13 (0.12 g, 0.43 mmol), thiophene-2-
acetonitrile (0.06 g, 0.52 mmol), and t-BuOK (0.06 g,
0.57 mmol) in dry ethanol was stirred for 24 h under nitro-
gen atmosphere. The red solid was filtered, washed with
hexane, and dried (0.10 g, 62%); mp 165 ꢀC; 1H NMR
(400 MHz, CDCl3): dH 3.83 (3H, s, OCH3), 4.28–4.35
(4H, m, OCH2), 6.92 (2H, d, J¼8.00 Hz, CHAPh), 7.02
(2H, m, thiophene), 7.21 (1H, m, thiophene), 7.54 (1H, s,
vinyl), 7.74 (2H, d, J¼7.96 Hz, CHBPh); 13C NMR
(100.6 MHz, CDCl3): dC 55.3, 64.4, 65.1, 98.1, 110.5,
114.1, 117.8, 122.9, 124.7, 124.9, 125.5, 127.8, 128.0, 128.1,
136.7, 139.8, 144.9, 159.4; mass m/z: 381 (M+). Anal. Calcd
for C20H15NO3S2: C, 62.97; H, 3.96; N, 3.67; S, 16.81.
Found: C, 62.82; H, 4.05; N, 3.77; S, 16.75.
5.4. A representative procedure for Vilsmeier–Haack
formylation
5.4.1. 2,3-Dihydro-7-(4-methoxyphenyl)thieno[3,4-
b][1,4]dioxine-5-carbaldehyde (13). POCl3 (0.14 mL,
1.6 mmol) was slowly added to a mixture of dry DCM
(10 mL) and DMF (0.12 mL, 1.6 mmol) at 0 ꢀC. After the
addition was completed, the reaction mixture was stirred at
room temperature until a pale yellow color (Vilsmeier re-
agent) formed. Then it was added to a solution of 9a
(0.2 g, 0.80 mmol) in dry DCM (10 mL) at 0 ꢀC. The reac-
tion mixture was stirred at room temperature for additional
10 h. Then the solvent was completely removed and treated
with aqueous 5% NaOH (20 mL) at room temperature for
15 min. The crude product was then extracted with DCM
(30 mL) and dried (Na2SO4). Removal of solvent followed
by column chromatographic purification of the crude
product on neutral alumina (hexane–EtOAc 9:1) afforded
5.5.2. 3-(2,3-Dihydro-5-(2-methoxynaphthalen-6-yl)thi-
eno[3,4-b][1,4]dioxin-7-yl)-2-(thiophen-2-yl)acrylonitrile
(17). Following the general procedure, compound 17 was
obtained as a red solid (0.12 g, 65%); mp 240 ꢀC; 1H
NMR (400 MHz, CDCl3): dH 3.94 (3H, s, OCH3), 4.41–
4.43 (4H, m, OCH2), 7.04–7.06 (1H, dd, J¼3.70 Hz,
J¼1.15 Hz, thiophene), 7.11 (1H, d, J¼2.34 Hz, thiophene),
7.15 (2H, d, J¼8.85 Hz, ArH), 7.24 (1H, d, J¼8.50 Hz,
ArH), 7.28 (1H, d, J¼3.28 Hz, ArH), 7.57 (1H, s, vinyl),
7.74 (2H, dd, J¼8.68 Hz, J¼9.4 Hz, ArH), 7.87 (1H, dd,
J¼0.94 Hz, J¼1.0 Hz, thiophene); 13C NMR (100.6 MHz,
CDCl3): dC 64.49, 65.06, 98.58, 105.87, 111.29, 117.75,
119.31, 123.22, 125.03, 125.06, 125.58, 125.68, 127.09,
127.38, 127.79, 128.03, 128.88, 129.86, 134.05, 137.60,
139.79, 144.96, 158.22; mass m/z: 431 (M+). Anal. Calcd
for C24H17NO3S2: C, 66.80; H, 3.97; N, 3.25; S, 14.86.
Found: C, 66.71; H, 3.86; N, 3.29; S, 14.95.
1
13 as orange solid (0.15 g, 72%); mp 158 ꢀC; H NMR
(400 MHz, CDCl3): dH 3.81 (3H, s, OCH3), 4.29–4.36
(4H, m, OCH2), 6.93 (2H, d, J¼8.28 Hz, CHAPh), 7.73
(2H, d, J¼8.38 Hz, CHBPh), 9.92 (1H, s, CHO); 13C NMR
(100.6 MHz, CDCl3): dC 55.3, 64.4, 65.1, 110.6, 114.8,
124.4, 128.4, 136.8, 141.7, 149.1, 160.1, 180.1; mass m/z:
276 (M+). Anal. Calcd for C14H12O4S: C, 60.86; H, 4.38;
S, 11.60. Found: C, 60.72; H, 4.47; S, 11.67.
5.5.3. 2-((2,3-Dihydro-5-(4-methoxyphenyl)thieno[3,4-
b][1,4]dioxin-7-yl)methylene)malononitrile (18). Follow-
ing the general procedure, compound 18 was obtained as
a red solid (0.11 g, 51%); mp 198 ꢀC; 1H NMR (400 MHz,
CD3CN): dH 3.26 (3H, s, OCH3), 3.84–3.87 (4H, m,
OCH2), 6.48 (2H, d, J¼8.8 Hz, CHAPh), 7.21 (2H, d,
J¼8.8 Hz, CHBPh), 7.45 (1H, s, vinyl); mass m/z: 324
(M+). Anal. Calcd for C17H12N2O3S: C, 62.95; H, 3.73; N,
8.64; S, 9.89. Found: C, 62.82; H, 3.82; N, 8.57; S, 9.95.
5.4.2. 2,3-Dihydro-7-p-tolylthieno[3,4-b][1,4]dioxine-5-
carbaldehyde (14). Following the general procedure, com-
pound 14 was obtained as a yellow solid (0.19 g, 60%);
mp >300 ꢀC; 1H NMR (300 MHz, CDCl3): dH 2.83 (3H, s,
CH3), 4.40–4.43 (4H, m, OCH2), 6.93 (2H, d, J¼7.80 Hz,
CHAPh), 7.53 (2H, d, J¼8.1 Hz, CHBPh), 9.89 (1H, s,
CHO); mass m/z: 260 (M+). Anal. Calcd for C14H12O3S:
C, 64.60; H, 4.65; S, 12.32. Found: C, 64.52; H, 4.81; S,
12.25.
5.5.4. 2-((2,3-Dihydro-5-p-tolylthieno[3,4-b][1,4]dioxin-
7-yl)methylene)malonitrile (19). Following the general
procedure, compound 19 was obtained as a red solid
(0.099 g, 56%); mp >300 ꢀC; 1H NMR (300 MHz,
CDCl3): dH 2.53 (3H, s, CH3), 4.49–4.51 (4H, m, OCH2),
7.20 (2H, d, J¼7.8 Hz, CHAPh), 7.59 (2H, d, J¼7.8 Hz,
CHBPh), 7.98 (1H, s, vinyl); mass (EI) m/z (%): 308 (M+).
Anal. Calcd for C17H12N2O2S: C, 66.22; H, 3.92; N, 9.08;
S, 10.40. Found: C, 66.42; H, 4.02; N, 9.01; S, 10.29.
5.4.3. 2,3-Dihydro-7-(2-methoxynaphthalen-6-yl)thi-
eno[3,4-b][1,4]dioxine-5-carbaldehyde (15). Following
the general procedure, compound 15 was obtained as a yel-
1
low solid (0.19 g, 60%); mp 154 ꢀC; H NMR (400 MHz,
CDCl3): dH 3.9 (3H, s, OCH3), 4.25–4.27 (2H, m, OCH2),
4.34–4.36 (2H, m, OCH2), 7.11–7.16 (2H, m, Ph), 7.71–
7.79 (4H, m, Ph), 9.91 (1H, s, CHO); 13C NMR (100.6 MHz,
CDCl3): dC 53.33, 65.15, 65.27, 105.85, 110.66, 115.46,
118.52, 119.48, 124.89, 126.95, 127.25, 128.69, 129.56,
134.51, 141.80, 158.51, 149.09; mass m/z: 326 (M+).
Anal. Calcd for C18H14O4S: C, 66.24; H, 4.32; S, 9.82.
Found: C, 66.32; H, 4.22; S, 9.75.
5.5.5. 3-(2,3-Dihydro-5-(2-methoxynaphthalen-6-yl)-
thieno[3,4-b][1,4]dioxin-7-yl)-2-(3,4-dimethoxyphenyl)-
acrylonitrile (20). Following the general procedure,
compound 20 was obtained as a red solid (0.062 g, 42%);
mp 220 ꢀC; 1H NMR (300 MHz, CDCl3): dH 3.76 (3H,
s, OCH3), 3.85 (6H, s, OCH3), 4.43–4.46 (4H, m,
OCH2), 6.95–6.98 (2H, m, ArH), 7.12–7.20 (4H, m, ArH),
7.79–7.86 (3H, m, ArH), 8.41 (1H, s, vinyl); mass m/z: 485
(M+). Anal. Calcd for C28H23NO5S: C, 69.26; H, 4.77; N,
2.88; S, 6.60. Found: C, 69.35; H, 4.72; N, 2.97; S, 6.55.
5.5. A representative procedure for condensation
reaction
5.5.1. 3-(2,3-Dihydro-5-(4-methoxyphenyl)thieno[3,4-
b][1,4]dioxin-7-yl)-2-(thiophen-2-yl)acrylonitrile (16). A

P. Amaladass et al. / Tetrahedron 63 (2007) 10363–10371
10371
9. (a) Sotzig, G. A.; Reynolds, J. R.; Steel, P. J. Chem. Mater.
1996, 8, 882–889; (b) Balasubramanian, S.; Reynolds, J. R.
Macromolecules 1997, 30, 2582–2588.
10. (a) Sotizg, G. A.; Thomas, T. A.; Reynolds, J. R.; Steel,
P. J. Macromolecules 1998, 31, 3750–3752; (b) Fu, Y.;
Cheng, H.; Elsenbaumer, R. L. Chem. Mater. 1997, 9,
1720–1724.
5.5.6. 3-(5-(4-Methoxystyryl)-2,3-dihydrothieno[3,4-
b][1,4]dioxin-7-yl)-2-(thiophen-2-yl)acrylonitrile (23).
Following the general procedure, compound 23 was
obtained as a red solid (0.068 g, 51%); mp 195 ꢀC; 1H
NMR (400 MHz, CDCl3): dH 3.83 (3H, s, OCH3), 4.34–
4.36 (4H, m, OCH2), 6.88 (2H, d, J¼8.7 Hz, CHAPh),
7.01–7.03 (3H, m), 7.22–7.28 (2H, m), 7.41 (2H,
d, J¼8.7 Hz, CHBPh), 7.51 (1H, s, vinyl); mass m/z:
407 (M+). Anal. Calcd for C22H17NO3S2: C, 64.84; H,
4.20; N, 3.44; S, 15.74. Found: C, 64.82; H, 4.05; N, 3.57;
S, 15.85.
11. Mohanakrishnan, A. K.; Amaladass, P.; Arul Clement, J.
Tetrahedron Lett. 2007, 48, 539–544.
12. (a) Sotzig, G. A.; Reynolds, J. R. J. Chem. Soc., Chem.
Commun. 1995, 703–704; (b) Reddinger, J. L.; Sotzig, G. A.;
Reynolds, J. R. Chem. Commun. 1996, 1777–1778; (c)
Peptidone, M. F.; Hardaker, S. S.; Gregory, R. V. Chem.
Mater. 2003, 15, 557–563.
Acknowledgements
13. Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz, E.; Lemaire, M.
Chem. Rev. 2002, 102, 1359–1470.
The authors thank DST, New Delhi (SR/S1/OC-37/2005)
and UGC-PFE for financial support. P.A. thanks CSIR, for
a CSIR-SRF fellowship. J.A.C. thanks UGC-PFE for
fellowship. The authors thank DST-FIST for 300 MHz
NMR facility.
14. (a) Zhu, S. S.; Swager, T. M. J. Am. Chem. Soc. 1997, 119,
12568–12577; (b) Hicks, R. G.; Nodwell, M. B. J. Am.
Chem. Soc. 2000, 12, 6746–6753; (c) Meng, H.; Tucker, D.;
Chaffins, S.; Chen, Y.; Helgeson, R.; Dunn, B.; Wudl, F. Adv.
Mater. 2003, 15, 147–149.
15. Mohanakrishnan, A. K.; Hucke, A.; Lyon, M. A.;
Lakshmikantham, M. V.; Cava, M. P. Tetrahedron 1999, 55,
11745–11754.
References and notes
16. Borghese, A.; Geldhof, G.; Antoine, L. Tetrahedron Lett. 2006,
47, 9249–9252.
17. Turbiez, M.; Frere, P.; Roncali, J. J. Org. Chem. 2003, 68,
5357–5360.
18. Turbiez, M.; Frere, P.; Roncali, J. Tetrahedron 2005, 61, 3045–
3053.
19. Yanagisawa, S.; Sudo, T.; Noyori, R.; Itami, K. J. Am. Chem.
Soc. 2006, 126, 11748–11749.
20. Raimundo, J.-M.; Blanchard, P.; Brisset, H.; Akoudad, S.;
Roncali, J. Chem. Commun. 2000, 939–940.
21. Raimundo, J.-M.; Blanchard, P.; Gallego-Plans, N.; Mercier,
N.; Ledoux-Rak, I.; Hierle, R.; Roncali, J. J. Org. Chem.
2002, 67, 205–218.
22. Manuela, M.; Raposo, M.; Sousa, A. M. R. C.; Kirsch, G.;
Cardoso, P.; Belsley, M.; Gomes, E. de. M.; Fonseca, A. M.
Org. Lett. 2006, 8, 3681–3684.
1. (a) Yoshinno, K. Synth. Met. 1989, 28, 669–674; (b) Garnier, F.;
Horowitz, G.; Fichou, D. Synth. Met. 1989, 28, 705–714; (c)
Garnier, F.; Horowitz, G.; Peng, X.; Fichou, D. Adv. Mater.
1990, 2, 592–594; (d) Meng, H.; Bao, Z.; Lovinger, A. J.;
Wang, B.-C.; Mujsce, A. M. J. Am. Chem. Soc. 2001, 123,
9214–9215; (e) Mushush, M.; Facchetti, A.; Lefenfeld, M.;
Katz, H. E.; Marks, T. J. J. Am. Chem. Soc. 2003, 125, 9414–
9423; (f) Yoshida, Y.; Tanigaki, N.; Yase, K.; Hotta, S. Adv.
Mater. 2002, 12, 1587–1591.
2. (a) Mori, A.; Sekiguchi, A.; Masui, K.; Shimada, T.; Horie, M.;
Osakada, K.; Kawamoto, M.; Ikeda, T. J. Am. Chem. Soc. 2003,
125, 1700–1701; (b) Mochizuki, H.; Hasui, T.; Kawamoto, M.;
Shiono, T.; Ikeda, I.; Adachi, C.; Taniguchi, Y.; Shiroto, T.
Chem. Commun. 2000, 1923–1924.
3. Gozzi, C.; Lavenot, L.; IIg, K.; Penalva, V.; Lemaire, M.
Tetrahedron Lett. 1997, 38, 8867–8870.
23. (a) Mohanakrishnan, A. K.; Amaladass, P. Tetrahedron Lett.
2005, 46, 4225–4229; (b) Mohanakrishnan, A. K.;
Amaladass, P.; Arul Clement, J. Tetrahedron Lett. 2007, 48,
779–784.
24. Kisselev, R.; Thelakkat, M. Macromolecules 1998, 37, 8951–
8958.
4. (a) Ohta, A.; Akita, Y.; Ohkama, T.; Chiba, M.; Fukunaga, R.;
Miyafuji, A.; Nakata, T.; Tani, N.; Aoyagi, Y. Heterocycles
1990, 31, 1951–1958; (b) Okazawa, T.; Satoh, T.; Miura, M.;
Nomura, M. J. Am. Chem. Soc. 2002, 124, 5286–5287.
5. Glover, B.; Harvey, K. A.; Liu, B.; Sharp, M. J.; Timoschenko,
M. F. Org. Lett. 2003, 5, 301–304.
25. Crystallographic data for 9m have been deposited with the
Cambridge Crystallographic Data Center as supplementary
publication number CCDC 652138. Copies of the data may
be obtained, free of charge, on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44(0) 1223
33603 or e-mail: deposit@ccdc.cam.ac.uk).
6. Kang, S.-K.; Kim, J.-S.; Choi, S.-C. J. Org. Chem. 1997, 62,
4208–4209.
7. Yokooji, A.; Satoh, T.; Miura, M.; Nomura, M. Tetrahedron
2004, 60, 6757–6763.
8. Masui, K.; Mori, A.; Okano, K.; Takamura, K.; Kinoshita, M.;
Ikeda, T. Org. Lett. 2004, 6, 2011–2014.