A highly selective catalytic system for the cross-coupling of (E)-Styryl Bromide with Benzeneboronic acid: Application to the synthesisof all-trans poly(arylenevinylene)s

Article abstract of DOI:10.1246/bcsj.82.1292

Ahighlyselective system for palladium-catalyzed polycondensation of (E, E)-1,4-bis(2-bromoethenyl)benzene ((E, E)-1)with 2,5-dioctyloxybenzene-1,4- diboronicacid(2a)togive all-trans poly[(p-phenylenevinylene)-alt-(2,5- dioctyloxy-1,4-phenylenevinylene)] (all-trans 3) has been investigated using (E)-styryl bromide ((E)-4) and 2,5-dioctyl- oxybenzeneboronicacid(5a) as model compounds of and 2a, respectively. The reaction of (E)-4 and 5a in toluene in the presence of Pd(PPh₃)₄ catalyst and aqueous K ₂CO₃ base affords considerable amounts of homocoupling products (i.e., 1,4-diphenylbutadiene (13%) and 2,2',5,5'-tetraoctyloxybiphenyl (22%)), together with (E)-2,5-dioctyl- oxystilbene ((E)-6a) as the cross-coupling product (30%). The use of aqueous NaOH as a strong base and Bu₄NBr as a phase-transfer catalyst notably reduces the homocoupling products, and the use of Pd(PBu^t₃)₂ instead of Pd(PPh₃)₄ results inalmost perfect selectivity of the cross-coupling product (E)-6a. Under optimized catalytic conditions, the desired all- trans 3 has been successfully prepared without notabledefects in the polymer chain.

Full text of DOI:10.1246/bcsj.82.1292

1292 Bull. Chem. Soc. Jpn. Vol. 82, No. 10, 1292–1298 (2009)
© 2009 The Chemical Society of Japan
A Highly Selective Catalytic System for the Cross-Coupling of
(E)-Styryl Bromide with Benzeneboronic Acid: Application
to the Synthesis of All-Trans Poly(arylenevinylene)s
Masayuki Wakioka, Yuichiro Mutoh, Ryo Takita, and Fumiyuki Ozawa*
International Research Center for Elements Science (IRCELS), Institute for Chemical Research,
Kyoto University, Uji, Kyoto 611-0011
Received June 5, 2009; E-mail: ozawa@scl.kyoto-u.ac.jp
A highly selective system for palladium-catalyzed polycondensation of (E,E)-1,4-bis(2-bromoethenyl)benzene
((E,E)-1) with 2,5-dioctyloxybenzene-1,4-diboronic acid (2a) to give all-trans poly[(p-phenylenevinylene)-alt-(2,5-
dioctyloxy-1,4-phenylenevinylene)] (all-trans 3) has been investigated using (E)-styryl bromide ((E)-4) and 2,5-dioctyl-
oxybenzeneboronic acid (5a) as model compounds of (E,E)-1 and 2a, respectively. The reaction of (E)-4 and 5a in
toluene in the presence of Pd(PPh3)4 catalyst and aqueous K2CO3 base affords considerable amounts of homocoupling
products (i.e., 1,4-diphenylbutadiene (13%) and 2,2¤,5,5¤-tetraoctyloxybiphenyl (22%)), together with (E)-2,5-dioctyl-
oxystilbene ((E)-6a) as the cross-coupling product (30%). The use of aqueous NaOH as a strong base and Bu4NBr as a
phase-transfer catalyst notably reduces the homocoupling products, and the use of Pd(PBut3)2 instead of Pd(PPh3)4 results
in almost perfect selectivity of the cross-coupling product (E)-6a. Under optimized catalytic conditions, the desired all-
trans 3 has been successfully prepared without notable defects in the polymer chain.
Poly(phenylenevinylene)s (PPVs) and their homologs (i.e.,
poly(arylenevinylene)s: PAVs) are among the ³-conjugated
polymers that have wide application in optoelectronic devices
such as light-emitting diodes (LEDs), photovoltaic cells, plastic
lasers, and field-effect transistors (FETs).1 It has been recog-
nized that ³-conjugated polymers are advantageous over small
organic molecules as well as inorganic compounds in terms of
accessibility of thin films by solution processes, which enable
easy and low-cost fabrication of large-area devices. We have
found that all-cis PPVs with the vinylene linkages entirely
controlled to cis geometry exhibit a unique film-forming
property.2-4 Reflecting the all-cis geometry with a zigzag
structure, the polymers are well soluble in common organic
solvents and form highly amorphous films by spin-coating.2,4
Furthermore, the resulting films become much less soluble
under UV light, along with cis-to-trans isomerization of
vinylene linkages to give all-trans PPVs.2 On the basis of
these findings, an extremely simple method of generating
microscale patterns of all-trans PPVs on a quartz substrate has
been developed. Given the fact that most of the devices have
multilayer structures and the establishment of well-defined
interfacial boundaries of thin films is of particular importance
for gaining high device performance, this phenomenon (i.e.,
photoinduced insolubilization) should be useful for fabricating
organic devices by solution processes.5
has been noted that the former group evidently facilitates the
photoinduced insolubilization. Thus, although all-trans PPVs
prepared by other synthetic methods are scarcely insolubilized
under UV-irradiation,7 all-trans PPVs prepared by Suzuki-
Miyaura-type polycondensation (i.e., all-trans 3 in Scheme 1)
possibly undergo photoinduced insolubilization. To examine
this point, we attempted to prepare all-trans 3 under the same
reaction conditions as applied for all-cis 3.3 However, as
already documented for related systems,9 unlike (Z,Z)-1,
(E,E)-1 was very prone to undergo homocoupling, and the
resulting polymer contained structural defects including
butadiene units in the main chain.
Therefore, we examined in this study highly selective
conditions using (E)-styryl bromide ((E)-4) and 2,5-dioctyl-
OC8H17
Br
Pd cat.
+
(XO)2B
C8H17
B(OX)2
2a
base
additive
Br
O
(E,E)-1
Br
OC8H17
OC8H17
C8H17
O
All-cis PPVs that form insoluble films of all-trans PPVs
under UV light have been synthesized by palladium-catalyzed
polycondensation of (Z,Z)-bis(2-bromoethenyl)benzene ((Z,Z)-
1) with 2,5-dioctyloxybenzene-1,4-diboronic acid (2a) (i.e.,
Suzuki-Miyaura-type polycondensation).6 The resulting poly-
mer bears 2-bromoethenyl and 2,5-dioctyloxybenzene groups,
derived from (Z,Z)-1 and 2a, respectively, at each terminus.3 It
n
all-trans 3
C8H17
O
O
O
a
B(OX)2 = B(OH)2 (2a), B
(2b)
Scheme 1.
Published on the web October 8, 2009; doi:10.1246/bcsj.82.1292

M. Wakioka et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 10 (2009) 1293
oxybenzeneboronic acid (5a) as model compounds of (E,E)-1
and 2a, respectively (Scheme 2). To our knowledge, Suzuki-
Miyaura cross-coupling of (E)-styryl bromide has been limited
to up to 90% yield,10,11 while polycondensation requires almost
perfect chemical yields.
obtained with Cs2CO3 and K3PO4 in place of K2CO3 (Entries 2
and 3). Thus, the highly reactive nature of (E)-4 toward
homocoupling has been evidenced.
Unlike previous reports,9 Ag2O did not improve the cross-
coupling selectivity, but resulted in hydrolysis of 5a (Entry 4).
Metal fluorides11c were also ineffective (Entries 5 and 6). On
the other hand, NaOH and KOH as strong bases notably
enhanced the selectivity of (E)-6a (Entries 7 and 8). The
selectivity was further improved by addition of Bu4NBr and
(Octyl)3MeNCl to the system (Entries 9-11). The combination
of aqueous NaOH and Bu4NBr was particularly effective,
giving a quantitative yield of (E)-6a (Entry 9).
Results and Discussion
Examination of Catalytic Conditions. Table 1 lists the
results of cross-coupling of (E)-4 with 5a under various
conditions. The reaction performed in toluene at 80 °C in the
presence of Pd(PPh3)4 (1.5 mol %) and aqueous K2CO3 (3
equiv) afforded four kinds of products; i.e., cross-coupling
product (E)-6a (30%), homocoupling products 7 (13%) and 8a
(22%), and a trace amount of 1,4-dioctyloxybenzene (9a) as a
hydrolysis product of 5a (Entry 1). Comparable results were
It is likely that the cross- and homocoupling reactions
involve styrylpalladium of the formula trans-Pd(CH=CHPh)-
Br(PPh3)2 (A) as a common intermediate. In the cross-coupling,
A reacts with 5a via transmetallation to give Pd(CH=CHPh)-
Ar(PPh3)2, which reductively eliminates (E)-6a.6 On the other
hand, as we already confirmed for related trans-Pd(CH=
CHPh)Br(PMePh2)2,12 A also reacts with (E)-4 via a novel
homocoupling process induced by P-C reductive elimination.13
Accordingly, A undergoes transmetallation and homocoupling
competitively in the catalytic system. Since it is known that the
association of areneboronic acid with a base is essential for
transmetallation to take place,7 it is reasonable that strong bases
such as NaOH and KOH facilitate transmetallation. Further-
more, ammonium salts, which serve as a phase-transfer catalyst
in a two-phase system consisting of toluene and water, enhance
the efficiency of base, and thereby transmetallation rate.
Another approach to the highly selective cross-coupling
system was accomplished with basic and bulky phosphine
ligands, because we recently confirmed that the homocoupling
reaction of (E)-4 to give 7 is induced by P-C reductive
Pd cat. (1.5 mol%)
base (3 equiv)
Br
ArB(OH)2
+
Ph
toluene
(E )-4
5
Ar
Ph
+
+
Ar Ar
+
Ar
H
Ph
Ph
(E )-6
7
8
9
Me
OC8H17
(b)
(c)
Ar =
C8H17
MeO
O
MeO
F3C
(a)
(d)
(e)
(f)
Scheme 2.
Table 1. Cross-Coupling Reaction of (E)-4 and 5aa)
Yield/%c)
Entry
Pd cat.
Baseb)
Additive
Time/h
6ad)
7e)
8a
9a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16g)
17g)
18g)
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PPh3)4
Pd(PCy3)2
Pd(PBut3)2
Pd(PBut3)2
Pd(PBut3)2
Pd(PBut3)2
Pd(PBut3)2
Pd(PBut3)2
K2CO3
Cs2CO3
K3PO4
Ag2O
KF
CsF
NaOH
KOH
NaOH
KOH
NaOH
KOH
NaOH
KOH
NaOH
NaOH
KOH
none
none
none
none
none
none
none
none
Bu4NBr
Bu4NBr
Aliquatf)
none
none
none
Bu4NBr
none
none
2
2
2
2
2
2
2
2
1
1
1
3
1
1
1
1
1
8
30 (97/3)
25 (99/1)
31 (96/4)
22 (98/2)
20 (98/2)
21 (99/1)
95 (>99/1)
72 (98/2)
99 (>99/1)h)
97 (>99/1)
97 (>99/1)
83 (99/1)
96 (>99/1)
97 (>99/1)
98 (>99/1)i)
98 (>99/1)
98 (>99/1)
55 (>99/1)
13 (29/71)
11 (18/82)
11 (22/78)
6 (77/23)
9 (28/72)
10 (22/78)
4 (42/58)
27 (18/82)
22
18
20
4
15
16
4
20
<1
1
<1
2
<1
74
2
2
1
4
<1
<1
<1
7
2
2
1
1
1
<1
0
0
0
3
7
10 (16/84)
<1
<1
0
0
<1
<1
<1
<1
<1
<1
<1
1
K2CO3
none
a) Unless otherwise noted, the reactions were run on a 0.20 mmol scale in toluene (1.0 mL) at 80 °C using Pd catalyst
(3.0 ¯mol), base (0.60 mmol), and/or additive (0.20 mmol). b) Bases were employed as aqueous solutions (3.0 M).
1
c) Determined by H NMR spectroscopy using hexamethylbenzene as an internal standard. d) E/Z ratios of 6a are
given in parentheses. e) E,E/E,Z ratios of 7 are given in parentheses. f) Aliquat 336: trioctylmethylammonium
chloride. g) The reaction was run at room temperature. h) Isolated yield: 98%. i) Isolated yield: 97%.

1294 Bull. Chem. Soc. Jpn. Vol. 82, No. 10 (2009)
Cross-Coupling of (E)-Styryl Bromide
elimination from A, and the P-C reductive elimination
significantly decelerates when tertiary phosphines are highly
basic and bulky.13 As seen from Entries 12-18 in Table 1, PCy3
was insufficient (Entry 12), but bulkier PBut3 led to an almost
quantitative yield of (E)-6a even in the absence of Bu4NBr
(Entries 13 and 14). The reaction successfully proceeded at
room temperature (Entries 16-18). Interestingly, unlike the
reaction using Pd(PPh3)4 (Entry 1), the homocoupling products
were negligible even in the presence of K2CO3 (Entry 18).
The Pd(PBut3)2 catalyst was highly effective in the cross-
coupling reactions of (E)-4 with boronic acids with electron-
rich aryl groups (5b-5e in Scheme 2), providing the desired
(E)-6 in nearly quantitative yields (Entries 1-4 in Table 2),
while 5f having an electron-deficient 4-trifluoromethylphenyl
group formed a small amount of homocoupling product 7
(Entry 5). In these attempts, K2CO3 was found to be the base of
choice; the boronic acids were hydrolyzed to a considerable
extent in the presence of NaOH and KOH.
Synthesis and Characterization of All-Trans PAVs. All-
trans 3 in Scheme 1 was synthesized under the catalytic
conditions of Entry 9 in Table 1 (Entry 1 in Table 3). A 1:1
mixture of (E,E)-1,4-bis(2-bromoethenyl)benzene (1) and
2,5-dioctyloxybenzene-1,4-diboronic acid (2a) was heated
in toluene at 80 °C for 24 h in the presence of Pd(PPh3)4
(1.5 mol %), aqueous NaOH (3 equiv), and Bu4NBr (1 equiv),
giving orange fluorescent suspension, which was diluted with
CH2Cl2, washed with H2O, and precipitated in methanol. The
resulting polymer however contained diene structures in the
main chain (ca. 5%) as confirmed by H NMR spectroscopy.
1
On the other hand, the reaction using Pd(PBut3)2 in place
of Pd(PPh3)4 afforded all-trans 3 without notable defects
in the PPV skeleton (Entry 2). The molecular weight de-
creased in the absence of Bu4NBr (Entry 3), but increased
when the reaction was carried out at room temperature using
the pinacolate ester 2b (Entry 4). The reaction was further
improved in THF (Entry 5), and all-trans 3 with Mn = 9700
was obtained in a quantitative yield under a slightly warmed
condition (Entry 6). Although the reaction was also examined
under reflux conditions, the resulting polymer was insoluble
in CHCl3.
Polycondensation reactions of four kinds of (E,E)-bis(2-
bromoethenyl)arenes (arene = m-phenylene (10), o-phenylene
(11), 4,4¤-biphenylene (12), and 2,7-fluorenylene (13)) with 2b
were also successful under the optimized conditions, giving the
corresponding all-trans PAVs 14-17 without notable structural
defects (Table 4).
The polymer structures were determined by NMR spec-
troscopy. Figure 1 compares the 1H NMR spectrum of all-trans
3 (A) with that of 4-(2-bromoethenyl)stilbene (18) having
the presumed terminal structures (B). The stereoregularity of
vinylene linkages can be estimated from the peak intensities of
the OCH2 signals of octyloxy groups; the signal of trans-PPV
appears at ¤ 4.08, whereas that of cis isomer at ¤ 3.54.2,3 Thus,
no trace of the signal of cis isomer was observed. Spectrum
(A) exhibited the signals assignable to 2,5-dioctyloxyphenyl
(a-d) and (E)-2-bromoethenyl (e) groups in reasonable inten-
sities, showing the presence of these groups at the chain ends of
all-trans 3.
Finally, the performance in photoinduced insolubilization
was investigated. A thin film of all-trans 3 (Mn = 7500, Entry 5
in Table 3) was prepared from a CHCl3 solution (2.0 wt %)
by spin-coating on a quartz substrate (i), irradiated with a Xe
lamp (- = 300-400 nm, 21.0 mW cm¹2) for 1 h under vacuum
at room temperature (ii), and rinsed twice with CHCl3 and dried
(iii). The amount of thin-film on the quartz substrate at each
step was evaluated by UV-vis spectroscopy.
Figure 2 shows the UV-vis spectra. No notable change was
observed before and after UV-irradiation ((i) and (ii)). On the
other hand, the absorption intensity decreased to 22% after
rinsing (iii). This remaining percent of film was clearly higher
than that of all-trans PPV prepared by Hiyama-type poly-
condensation (8%),7 but much lower than that of all-cis 3
(84%; Mn = 7000, Mw/Mn = 2.69).
Table 2. Cross-Coupling Reactions of (E)-4 and 5a)
Yield/%b)
Entry
5
Time/h
6c)
7d)
1
2
3
4
5
5b
5c
5d
5e
5f
1
1
1
2
24
98 (>99/1)
98 (>99/1)
99 (>99/1)
97 (>99/1)
79 (>99/1)e)
<1
<1
<1
<1
5 (75/25)e)
a) All reactions were run on a 0.20 mmol scale in toluene
(1.0 mL) at room temperature in the presence of Pd(PBut3)2
(3.0 ¯mol) and aqueous K2CO3 (3.0 M, 0.60 mmol). b) Isolated
yields, unless otherwise noted. c) E/Z ratios of 6 determined
by 1H NMR spectroscopy are given in parentheses. d) E,E/E,Z
ratios of 7 determined by 1H NMR spectroscopy are given
in parentheses. e) The product yields were determined by
1H NMR analysis of the mixture of (E)-6f and 7 after
chromatographic purification.
Table 3. Polycondensation of (E,E)-1 with 2a)
c)
c)
Entry Pd cat.
2
Bu4NBr Solvent Temp/°C Yieldb)/% Mn
Mw/Mn
cis/transd) Defectd)
1
2
3
4
5
6
Pd(PPh3)4
2a 1 equiv toluene
2a 1 equiv toluene
80
80
80
20
20
30
>99
>99
91
98
>99
>99
8400
4900
2700
4100
7500
9700
3.03
2.48
1.57
1.44
1.80
1.96
<1/99
<1/99
<1/99
<1/99
<1/99
<1/99
trace
none
none
none
none
none
Pd(PBut3)2
Pd(PBut3)2
Pd(PBut3)2
Pd(PBut3)2
Pd(PBut3)2
2a
2b
2b
2b
®
®
®
®
toluene
toluene
THF
THF
a) Reactions were carried out for 24 h using (E,E)-1 (0.20 mmol), 2 (0.20 mmol), aqueous NaOH (3.0 M, 0.60 mmol), and
Pd catalyst (3.0 ¯mol) in solution (2.0 mL). b) Yield of MeOH-insoluble polymer. c) Determined by GPC calibration
1
based on polystyrene standards. d) Determined by H NMR spectroscopy.

M. Wakioka et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 10 (2009) 1295
Table 4. All-Trans PAVs Prepared by Polycondensation of (E,E)-BrCH=CH-Ar-CH=CHBr 10-13 with 2ba)
Yield/%b)
>99
Mn
Mw/Mn
cis/transd)
<1/99
c)
c)
Entry
PAV
OC8H17
1
18300
2.10
n
C8H17
O
14
OC8H17
2
3
99
9900
7600
2.66
1.44
<1/99
<1/99
n
15
16
C8H17O
OC8H17
>99
n
C8H17
O
OC8H17
4
>99
6900
1.17
<1/99
n
C8H17O
17
a) Reactions were run at 20 °C for 24 h using (E,E)-10-13 (0.20 mmol), 2b (0.20 mmol), aqueous NaOH (3.0 M,
0.60 mmol), and Pd(PBut3)2 (3.0 ¯mol) in THF (2.0 mL). b) Yield of MeOH-insoluble polymer. c) Determined
1
by GPC calibration based on polystyrene standards. d) Determined by H NMR spectroscopy.
Toluene (Kanto, dehydrated) and THF (Wako, dehydrated) were
used as received. (E)-Styryl bromide ((E)-4) was purified under
alkaline conditions to remove contamination of the Z isomer.14 The
Conclusion
We found a highly selective catalytic system for Suzuki-
following compounds were synthesized according to the literature:
Miyaura cross-coupling of (E)-styryl bromide ((E)-4) with
Pd(PPh3)4,15 Pd(PCy3)2,16 Pd(PBut3)2,16 2,5-dioctyloxybenzene-
areneboronic acids (5), giving almost quantitative yields of (E)-
boronic acid (5a),17 2,5-dioctyloxy-1,4-benzenediboronic acid
6. Under optimized conditions, five kinds of all-trans PAVs 3
(2a),18 and 2,5-dioctyloxy-1,4-bis(4,4,5,5-tetramethyl-1,3,2-dioxa-
and 14-17 were synthesized without notable structural defects
borolan-2-yl)benzene (2b).3 All other chemicals, except for 8a and
in the polymer chain. Although all-trans 3 thus prepared
(E,E)-10-13 (see Supporting Information), were obtained from
underwent photoinduced insolubilization, its performance was
commercial suppliers and used without further purification.
much lower than that of all-cis 3, showing the importance of
all-cis configuration for photoinduced insolubilization.
Cross-Coupling of (E)-4 with 5a (Entry 9 in Table 1). A 10-
mL Schlenk tube was charged with 5a (75.7 mg, 0.200 mmol),
Pd(PPh3)4 (3.5 mg, 3.0 ¯mol), Bu4NBr (64.5 mg, 0.200 mmol),
toluene (1 mL), and 3.0 M aqueous NaOH (0.20 mL, 0.60 mmol).
Experimental
General Considerations. All manipulations using organo-
metallic compounds were carried out under a nitrogen or argon
atmosphere using conventional Schlenk techniques. NMR spectra
were recorded on a Bruker Avance 400 spectrometer (1H NMR
400.13 MHz and 13C NMR 100.62 MHz). Chemical shifts are
reported in ¤, referenced to the 1H (residual protons) and 13C signals
of deuterated solvents. Analytical GPC was carried out on a JASCO
GPC assembly consisting of a model PU-980 precision pump, a
model RI-1530 refractive index detector, and three polystyrene gel
columns (Shodex KF-801, KF-803L, and KF-805L). THF was used
as the mobile phase with a flow rate of 1.0 mL min¹1 at 40 °C. The
columns were calibrated against 9 standard polystyrene samples
(Shodex; Mn = 980-1920000). Melting points were measured with
a Yanaco MP-S3 instrument. Elemental analysis was performed
by the ICR Analytical Laboratory, Kyoto University. Spin-coating
of PPV was performed with a Mikasa spin coater 1H-DX2.
Photoirradiation was carried out at room temperature with an Asahi
Spectra LAX-101 Xe lamp. UV-vis absorption spectra were
recorded on a JASCO V-560 spectrometer.
Compound (E)-4 (36.6 mg, 0.200 mmol) was added, and the
mixture was stirred at 80 °C for 1 h. After cooling to room
temperature, the mixture was passed through a short column (SiO2,
hexane/CH2Cl2 (1/1)), concentrated to dryness, and examined by
1H NMR using hexamethylbenzene as an internal standard,
showing the formation of (E)-2,5-dioctyloxystilbene (6a, E/Z >
99/1) in 99% yield, which was isolated as a colorless oil by
column chromatography (SiO2, hexane and then hexane/CH2Cl2
(4/1)) (85.7 mg, 98% yield). The NMR data for (E)-6a were
identical to those reported.19 1H NMR (CDCl3): ¤ 7.52 (d, J = 7.5
Hz, 2H, H2,6 of C6H5), 7.46 (d, J = 16.5 Hz, 1H, C6H3CH=CH),
7.35 (t, J = 7.7 Hz, 2H, H3,5 of C6H5), 7.24 (t, J = 7.5 Hz, 1H, H4
of C6H5), 7.15 (d, J = 3.0 Hz, 1H, H6 of C6H3), 7.11 (d, J =
16.5 Hz, 1H, C6H3CH=CH), 6.82 (d, J = 8.9 Hz, 1H, H3 of C6H3),
6.77 (dd, J = 8.9, 2.9 Hz, 1H, H4 of C6H3), 3.96 (t, J = 6.5 Hz, 2H,
OCH2), 3.95 (t, J = 6.5 Hz, 2H, OCH2), 1.87-1.73 (m, 4H, CH2),
1.54-1.23 (m, 20H, CH2), 0.93-0.84 (m, 6H, CH3).
Cross-Coupling of (E)-4 with 5b-5f. A typical procedure
is reported for Entry 2 in Table 2. A 10-mL Schlenk tube was

1296 Bull. Chem. Soc. Jpn. Vol. 82, No. 10 (2009)
Cross-Coupling of (E)-Styryl Bromide
charged with 5b (24.4 mg, 0.200 mmol), Pd(PBut3)2 (1.5 mg,
3.0 ¯mol), toluene (1 mL), and 3.0 M aqueous K2CO3 (0.20 mL,
0.60 mmol). Compound (E)-4 (36.6 mg, 0.200 mmol) was added,
and the mixture was stirred at room temperature for 1 h. The
mixture was passed through a short column (SiO2, hexane/
CH2Cl2 (1/1)), concentrated to dryness, and examined by
1H NMR, showing the absence of butadiene 7. Purification by
column chromatography (SiO2, hexane) afforded (E)-6b as a white
solid (35.3 mg, 98% yield). The NMR data of (E)-6b-6f were
identical to those reported.20
(E)-6b:20a 1H NMR (CDCl3): ¤ 7.51 (d, J = 7.3 Hz, 4H, C6H5),
7.35 (t, J = 7.4 Hz, 4H, C6H5), 7.25 (t, J = 7.2 Hz, 2H, C6H5), 7.10
(s, 2H, CH=CH).
(E)-6c:20b 1H NMR (CDCl3): ¤ 7.49 (d, J = 7.3 Hz, 2H, C6H5),
7.40 (d, J = 8.0 Hz, 2H, C6H4), 7.34 (t, J = 7.7 Hz, 2H, C6H5),
7.23 (t, J = 7.7 Hz, 1H, C6H5), 6.15 (d, J = 8.0 Hz, 2H, C6H4),
7.09 and 7.04 (each d, J = 16.6 Hz, 2H, CH=CH), 2.35 (s, 3H,
CH3).
(E)-6d:20b
1H NMR (CDCl3): ¤ 7.47 (d, J = 7.3 Hz, 2H,
C6H5), 7.44 (d, J = 8.7 Hz, 2H, C6H4), 7.33 (t, J = 7.5 Hz, 2H,
C6H5), 7.22 (t, J = 7.4 Hz, 1H, C6H5), 7.06 and 6.96 (each d, J =
16.3 Hz, 2H, CH=CH), 6.88 (d, J = 8.7 Hz, 2H, C6H4), 3.80 (s,
3H, OCH3).
(E)-6e:20b 1H NMR (CDCl3): ¤ 7.50 (d, J = 7.3 Hz, 2H, C6H5),
7.34 (t, J = 7.4 Hz, 2H, C6H5), 7.29-7.21 (m, 2H, C6H5 and C6H4),
7.10 (d, J = 16.4 Hz, 1H, CH=CH), 7.10 (d, J = 7.7 Hz, 1H,
C6H4), 7.06 (d, J = 16.4 Hz, 1H, CH=CH), 7.04 (t, J = 1.8 Hz,
1H, C6H4), 6.81 (dd, J = 8.2, 2.4 Hz, 1H, C6H4), 3.83 (s, 3H,
OCH3).
(E)-6f:20c 1H NMR (CDCl3): ¤ 7.62-7.55 (m, 4H, C6H4), 7.52
(d, J = 7.3 Hz, 2H, C6H5), 7.37 (t, J = 7.2 Hz, 2H, C6H5), 7.29 (t,
J = 7.2 Hz, 1H, C6H5), 7.18 and 7.10 (each d, J = 16.4 Hz, 2H,
CH=CH).
Figure 1. 1H NMR spectra of (A) all-trans 3 (Run 2 in
Table 2) and (B) 4-(2-bromoethenyl)stilbene (18) in CDCl3
at room temperature.
Synthesis of All-Trans PPV (3). A 10-mL Schlenk tube was
charged with (E,E)-1 (57.6 mg, 0.200 mmol), 2a (84.4 mg, 0.200
mmol), Bu4NBr (64.5 mg, 0.200 mmol), toluene (2 mL), and 3.0 M
aqueous NaOH (0.20 mL, 0.60 mmol). The complex Pd(PBut3)2
(1.5 mg, 3.0 ¯mol) was added, and the mixture was stirred at 80 °C
for 24 h. After cooling to room temperature, the mixture was
diluted with CH2Cl2 (5 mL), washed with water, and then poured
into a vigorously stirred MeOH (50 mL). An orange precipitate of
all-trans 3 was collected by membrane filter (0.5 ¯m), washed with
MeOH, and dried under vacuum at room temperature overnight
1
(94.4 mg, >99% yield). H NMR (CDCl3): ¤ 7.53 (s, C6H4), 7.50
(d, J = 16.5 Hz, CH=CH), 7.50-7.45 (m, H2,6 of terminal
C6H4CH=CHBr), 7.30 (d, J = 8.6 Hz, H3,5 of terminal C6H4CH=
CHBr), 7.15 (d, J = 16.7 Hz, CH=CH), 7.14 (s, H3,6 of C6H2),
7.11 (d, J = 14.2 Hz, CH=CHBr of terminal C6H4CH=CHBr),
6.83 (d, J = 9.1 Hz, H3 of terminal C6H3(OC8H17)2), 6.79 (d, J =
14.0 Hz, 1H, CH=CHBr), 6.77 (dd, J = 8.9, 2.8 Hz, H4 of terminal
C6H3(OC8H17)2), 4.08 (t, J = 6.0 Hz, OCH2), 3.98 and 3.96 (t,
J = 6.3 Hz, OCH2 of terminal C6H3(OC8H17)2), 1.96-1.80 and
1.62-1.18 (m, CH2), 0.94-0.80 (m, CH3). 13C{1H} NMR (CDCl3):
¤ 151.2 (s, C2,5 of C6H2), 137.2 (s, C1,4 of C6H4), 128.5 (s,
CH=CH), 127.0 (s, C1,2 of C6H2), 126.8 (s, C2,3,5,6 of C6H4), 123.2
(s, CH=CH), 110.6 (s, C3,6 of C6H2), 69.6 (s, OCH2), 31.8, 29.5,
29.4, 29.3, 26.3, 22.7 (each s, CH2), 14.1 (s, CH3).
Synthesis of All-Trans PAVs (14-17). These polymers were
synthesized similarly to all-trans 3 using (E,E)-10-13 (0.200
mmol), 2b (117 mg, 0.200 mmol), THF (2 mL), 3.0 M aqueous
NaOH (0.20 mL, 0.60 mmol), and Pd(PBut3)2 (1.5 mg, 3.0 ¯mol) at
20 °C for 24 h.
Figure 2. UV-vis absorption spectra of all-trans 3 (Mn =
7500) in thin film, before and after UV-irradiation (i and
ii), and after rinsing twice with CHCl3 (iii).

M. Wakioka et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 10 (2009) 1297
All-Trans 14: Yellow solid. 1H NMR (CDCl3): ¤ 7.65 (s, H2 of
C6H4), 7.54 (d, J = 16.3 Hz, CH=CH), 7.48 (d, J = 7.5 Hz, H4,6 of
C6H4), 7.38 (t, J = 7.3 Hz, H5 of C6H4), 7.22-7.13 (m, H3,6 of
C6H2 and CH=CH), 4.10 (t, J = 6.0 Hz, OCH2), 1.96-1.83 and
1.63-1.18 (m, CH2), 0.92-0.80 (m, CH3). 13C{1H} NMR (CDCl3):
¤ 151.2 (s, C2,5 of C6H2), 138.3 (s, C1,3 of C6H4), 128.9 (s,
CH=CH), 127.0 (s, C1,2 of C6H2), 125.5 and 125.3 (each s, C2 and
C6 of C6H4), 123.8 (s, CH=CH), 110.9 (s, C3,6 of C6H2), 69.7 (s,
OCH2), 31.8, 29.5, 29.4, 29.4, 26.3, and 22.7 (each s, CH2), 14.1
(s, CH3).
temperature for 30 min, the film was placed in a quartz cell under
N2 atmosphere, and analyzed by UV-vis absorption spectroscopy.
Next, the film was placed in a stainless-steel holder with a quartz
window, and irradiated by a Xe lamp (-max = 365 nm, 21.0
mW cm¹2) for 60 min under vacuum at room temperature. UV-vis
absorption spectrum of the resulting film was then recorded. The
film was rinsed twice in CHCl3 (each 3 mL) with light shaking,
dried under vacuum at room temperature, and examined by UV-
vis absorption spectroscopy.
1
All-Trans 15: Yellow solid. H NMR (CDCl3): ¤ 7.70-7.58
This work was supported by Grants-in-Aid for Scientific
Research (No. 20350049) from the Ministry of Education,
Culture, Sports, Science and Technology (MEXT), Japan.
(m, C6H4), 7.53 (d, J = 16.2 Hz, CH=CH), 7.37 (d, J = 16.2 Hz,
CH=CH), 7.32-7.22 (m, C6H4), 7.12 (s, H3,6 of C6H2), 3.99 (t,
J = 6.3 Hz, OCH2), 1.83-1.68 and 1.50-1.12 (m, CH2), 0.90-0.77
(m, CH3). 13C{1H} NMR (CDCl3): ¤ 151.2 (s, C2,5 of C6H2),
136.7 (s, C1,2 of C6H4), 127.5 (s, CH=CH), 127.2 (s, C1,4 of
C6H2), 126.9, 126.8, and 126.1 (each s, C3,6 and C4,5 of C6H4 and
CH=CH), 110.8 (s, C3,6 of C6H2), 69.5 (s, OCH2), 31.8, 29.5, 29.4,
29.4, 26.3, and 22.7 (each s, CH2), 14.1 (s, CH3).
Supporting Information
Experimental procedures for the preparation of 8a and (E,E)-
10-13. This material is available free of charge on the web at
http://www.csj.jp/journals/bcsj/.
1
All-Trans 16: Yellow solid. H NMR (CDCl3): ¤ 7.70-7.48
References
(m, C6H4), 7.55 (d, J = 16.3 Hz, CH=CH), 7.19 (d, J = 16.3 Hz,
CH=CH), 7.17 (s, H3,6 of C6H2), 4.09 (t, J = 6.3 Hz, OCH2), 1.96-
1.80 and 1.63-1.18 (m, CH2), 0.94-0.82 (m, CH3). 13C{1H} NMR
analysis was not feasible due to low solubility.
1
For reviews, see: a) A. Kraft, A. C. Grimsdale, A. B.
Holmes, Angew. Chem., Int. Ed. 1998, 37, 402. b) U. Scherf, Top.
Curr. Chem. 1999, 201, 163. c) L. Akcelrud, Prog. Polym. Sci.
2003, 28, 875. d) J. L. Segura, N. Martin, D. M. Guldi, Chem. Soc.
Rev. 2005, 34, 31. e) F. J. M. Hoeben, P. Jonkheijm, E. W. Meijer,
A. P. H. J. Schenning, Chem. Rev. 2005, 105, 1491. f) V.
Coropceanu, J. Cornil, D. A. da Silva Filho, Y. Olivier, R.
Silbey, J.-L. Brédas, Chem. Rev. 2007, 107, 926. g) I. D. W.
Samuel, G. A. Turnbull, Chem. Rev. 2007, 107, 1272. h) S. Günes,
H. Neugebauer, N. S. Sariciftci, Chem. Rev. 2007, 107, 1324.
i) S. W. Thomas, III, G. D. Joly, T. M. Swager, Chem. Rev. 2007,
107, 1339. j) A. C. Grimsdale, K. L. Chan, R. E. Martin, P. G.
Jokisz, A. B. Holmes, Chem. Rev. 2009, 109, 897.
1
All-Trans 17: Orange solid. H NMR (CDCl3): ¤ 7.83-7.68
and 7.62-7.46 (m, Fl), 7.55 (d, J = 16.0 Hz, CH=CH), 7.24-7.10
(m, H3,6 of C6H2 and CH=CH), 4.10 (t, J = 6.3 Hz, OCH2), 1.97-
1.81 and 1.65-1.18 (m, CH2), 0.96-0.82 (m, CH3). 13C{1H} NMR
analysis was not feasible due to low solubility.
Synthesis of (E,E)-4¤-(2-Bromoethenyl)-2,5-dioctyloxystil-
bene (18). To a solution of (E,E)-1 (130 mg, 0.450 mmol) and
5a (114 mg, 0.300 mmol) in toluene (1.5 mL) were successively
added Pd(PBut3)2 (2.3 mg, 4.5 ¯mol) and 3.0 M aqueous KOH
(0.30 mL, 0.90 mmol). The mixture was stirred at 80 °C for 24 h.
After cooling to room temperature, the mixture was passed through
a short column (SiO2, hexane/CH2Cl2 (1/1)), and purified by flash
column chromatography (SiO2, hexane and then hexane/CH2Cl2
(10/1)), giving the title compound as a yellow solid (89.2 mg, 55%
2
H. Katayama, M. Nagao, T. Nishimura, Y. Matsui, K.
Umeda, K. Akamatsu, T. Tsuruoka, H. Nawafune, F. Ozawa, J.
Am. Chem. Soc. 2005, 127, 4350.
3
H. Katayama, M. Nagao, T. Nishimura, Y. Matsui, Y.
Fukuse, M. Wakioka, F. Ozawa, Macromolecules 2006, 39, 2039.
H. Katayama, F. Ozawa, Y. Matsumiya, H. Watanabe,
Polym. J. 2006, 38, 184.
1
yield). Mp: 44-46 °C. H NMR (CDCl3): ¤ 7.47 (d, J = 16.3 Hz,
1H, C6H3CH=CH), 7.46 (d, J = 8.3 Hz, 2H, H2¤,6¤ of C6H4), 7.28
(d, J = 8.2 Hz, 2H, H3¤,5¤ of C6H4), 7.13 (d, J = 3.7 Hz, 1H, H6 of
C6H3), 7.10 (d, J = 14.0 Hz, 1H, CH=CHBr), 7.07 (d, J = 16.5
Hz, 1H, C6H3CH=CH), 6.83 (d, J = 8.9 Hz, 1H, H3 of C6H3), 6.78
(d, J = 13.9 Hz, 1H, CH=CHBr), 6.78 (dd, J = 9.1, 2.8 Hz, 1H,
H4 of C6H3), 3.96 (t, J = 6.3 Hz, 2H, OCH2), 3.95 (t, J = 6.4 Hz,
2H, OCH2), 1.87-1.73 (m, 4H, CH2), 1.54-1.23 (m, 20H, CH2),
0.93-0.85 (m, 6H, CH3). 13C{1H} NMR (CDCl3): ¤ 153.3 and
151.0 (each s, C2,5 of C6H3), 138.0 and 134.8 (each s, C1¤,4¤ of
C6H4), 136.9 (s, CH=CHBr), 128.3 (s, CH=CH), 127.3 (s, C1 of
C6H3), 126.9 and 126.4 (each s, C2¤,3¤,5¤,6¤ of C6H4), 124.1 (s,
CH=CH), 114.7, 113.9, and 112.3 (each s, C3,4,6 of C6H3), 106.2
(s, CH=CHBr), 69.5 and 68.7 (each s, OCH2), 31.8, 31.8, 29.5,
29.4, 29.4, 29.3, 29.3, 26.3, 26.3, 26.1, and 22.7 (each s, CH2),
14.1 (s, CH3). Anal. Calcd for C32H45BrO2: C, 70.96; H, 8.37%.
Found: C, 70.81; H, 8.45%.
4
5
6
J. G. C. Veinot, T. J. Marks, Acc. Chem. Res. 2005, 38, 632.
For Suzuki-Miyaura cross-coupling, see: a) N. Miyaura,
A. Suzuki, Chem. Rev. 1995, 95, 2457. b) N. Miyaura, in
Metal-Catalyzed Cross-Coupling Reactions, ed. by A. de Meijere,
F. Diederich, Wiley-VCH, Germany, 2004, Chap. 2.
7
As for all-trans PPV (Mn = 7200, Mw/Mn = 1.81) prepared
by Hiyama-type polycondensation of 2,5-dioctyloxy-1,4-diiodo-
benzene with (E,E)-bis(2-silylethenyl)benzene,8 only 8% of
polymer film remained on a quartz substrate after UV-irradiation
(-max = 365 nm, 21.0 mW cm¹2, for 1 h at room temperature),
followed by rinsing twice with CHCl3.
8
H. Katayama, M. Nagao, R. Moriguchi, F. Ozawa, J.
Organomet. Chem. 2003, 676, 49.
a) F. Koch, W. Heitz, Macromol. Chem. Phys. 1997, 198,
9
Photoinduced Insolubilization of PPV. A solution of PPV in
CHCl3 (2.0 wt %) was passed through a syringe filter (DISMIC-13
JP, PTFE 0.50 ¯m, Hydrophobic; ADVANTEC). A thin-film of
PPV was prepared by spin-coating on a quartz plate (1 cm2); the
filtrate (50 ¯L) was added dropwise on a plate, and the plate was
accelerated to 1200 rpm for 2 s, kept at this rate for 10 s, and then
rotated at 2000 rpm for 60 s. After drying under vacuum at room
1531. b) L. C. Lopez, P. Strohriegl, T. Stübinger, Macromol. Chem.
Phys. 2002, 203, 1926.
10 a) G. A. Molander, M. R. Rivero, Org. Lett. 2002, 4, 107. b)
F. Berthiol, H. Doucet, M. Santelli, Eur. J. Org. Chem. 2003, 1091.
11 For representative studies of Suzuki-Miyaura cross-
coupling of alkenyl halides, see: a) N. Miyaura, K. Yamada, H.
Suginome, A. Suzuki, J. Am. Chem. Soc. 1985, 107, 972. b) J.

1298 Bull. Chem. Soc. Jpn. Vol. 82, No. 10 (2009)
Cross-Coupling of (E)-Styryl Bromide
Chem. Soc. 1976, 98, 5850.
17 D. M. Johansson, X. Wang, T. Johansson, O. Inganäs, G.
Yu, G. Srdanov, M. R. Andersson, Macromolecules 2002, 35,
4997.
Uenishi, J. M. Beau, R. W. Armstrong, Y. Kishi, J. Am. Chem. Soc.
1987, 109, 4756. c) A. F. Littke, C. Dai, G. C. Fu, J. Am. Chem.
Soc. 2000, 122, 4020. d) G. A. Molander, L. A. Felix, J. Org.
Chem. 2005, 70, 3950.
12 M. Wakioka, M. Nagao, F. Ozawa, Organometallics 2008,
27, 602.
18 Q.-S. Hu, W.-S. Huang, D. Vitharana, X.-F. Zheng, L. Pu,
J. Am. Chem. Soc. 1997, 119, 12454.
13 M. Wakioka, Y. Nakajima, F. Ozawa, Organometallics
2009, 28, 2527.
19 H. Katayama, M. Nagao, F. Ozawa, M. Ikegami, T. Arai,
J. Org. Chem. 2006, 71, 2699.
14 L. J. Dolby, C. Wilkins, T. G. Frey, J. Org. Chem. 1966, 31,
1110.
15 D. R. Coulson, Inorg. Synth. 1972, 13, 121.
16 S. Otsuka, T. Yoshida, M. Matsumoto, K. Nakatsu, J. Am.
20 a) Z. Zhang, Z. Zha, C. Gan, C. Pan, Y. Zhou, Z. Wang,
M.-M. Zhou, J. Org. Chem. 2006, 71, 4339. b) B. Mu, T. Li, W.
Xu, G. Zeng, P. Liu, Y. Wu, Tetrahedron 2007, 63, 11475. c) K.
Selvakumar, A. Zapf, M. Beller, Org. Lett. 2002, 4, 3031.