Stereoselective synthesis of cis- and trans-oligo(phenylenevinylene)s via palladium-catalyzed cross-coupling reactions

Article abstract of DOI:10.1021/jo052602c

cis-Oligo(phenylenevinylene)s (OPVs) are synthesized by Suzuki-Miyaura coupling of arylboronic acids with (Z)-bromoalkenes in over 96% geometrical purity. On the other hand, trans-oligo(phenylenevinylene)s can be synthesized by Hiyama coupling of aryl iod

Full text of DOI:10.1021/jo052602c

Stereoselective Synthesis of cis- and trans-Oligo(phenylenevinylene)s
via Palladium-Catalyzed Cross-Coupling Reactions
Hiroyuki Katayama,*,† Masato Nagao,† Fumiyuki Ozawa,*,† Masashi Ikegami,‡ and
Tatsuo Arai‡
International Research Center for Elements Science (IRCELS), Institute for Chemical Research,
Kyoto UniVersity, Uji, Kyoto 611-0011, Japan, and Department of Chemistry, Graduate School of Pure
and Applied Science, UniVersity of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
hiroyuki@scl.kyoto-u.ac.jp; ozawa@scl.kyoto-u.ac.jp
ReceiVed December 19, 2005
cis-Oligo(phenylenevinylene)s (OPVs) are synthesized by Suzuki-Miyaura coupling of arylboronic acids
with (Z)-bromoalkenes in over 96% geometrical purity. On the other hand, trans-oligo(phenylenevinylene)s
can be synthesized by Hiyama coupling of aryl iodide with (E)-alkenylsilanes in almost perfect purities.
Effect of π-conjugation chain length on photoisomerization behavior of OPVs is described.
Introduction
these findings, an extremely simple method of generating
microscale patterns of PPVs onto quartz substrates was devel-
oped.
Oligo(phenylenevinylene)s (OPVs) have attracted consider-
able recent interest because of their potential applications in
optoelectronic devices such as light-emitting diodes and pho-
tovoltaic cells.1,2 OPVs have also been investigated as well-
defined models of poly(phenylenevinylene)s (PPVs) with precise
conjugation lengths and structures. Such studies are useful for
understanding the relations between bulk material properties and
molecular structures of PPVs.
Recently, we succeeded for the first time in the synthesis of
all-cis PPVs, in which vinylene linkages in the polymer
backbone are entirely stereoregulated to cis geometry.3 The all-
cis PPVs readily underwent photoisomerization to the corre-
sponding all-trans PPVs in solution. The cis-to-trans isomer-
ization also took place when thin films of all-cis PPVs were
exposed to UV light. Interestingly, the PPV films were
insolubilized during the photoisomerization. On the basis of
The cis-to-trans isomerization of PPVs involves a rather
simple change of absorption spectrum. Thus, while the all-cis
PPVs that we have prepared have 12-42 vinylene units in the
polymer chain, the UV-vis spectrum changes clearly with
isosbestic points. Furthermore, no notable shift of the absorption
maximum of trans isomer has been observed during the
isomerization. These observations are consistent with the
isomerization process that converts cis-vinylene units in the
polymer chain all at once to the trans groups, rather than
stepwise.
The one-way photoisomerization of conjugated olefins has
been documented in several instances.4 Thus, while stilbene
undergoes two-way isomerization to give a cis/trans mixture in
the photostationary state, the olefins with extended π-conjuga-
tion systems such as alkenylanthracene and styrylstilbene are
isomerized solely from the cis to trans isomer.
† Kyoto University.
‡ University of Tsukuba.
To examine the effect of π-conjugation length on photo-
isomerization behavior of PPVs, we tried to synthesize all-cis
and all-trans OPVs in a stereoselective manner. Although all-
trans isomers have been prepared by Horner-Wadsworth-
Emmons olefination of aldehydes or by Heck-type arylation of
(1) For reviews, see: (a) (a) Martin, R. E.; Diederich, F. Angew. Chem.,
Int. Ed. 1999, 38, 1350. (b) Scherf, U. Top. Curr. Chem. 1999, 201, 163.
(c) Tour, J. M. Chem. ReV. 1996, 96, 537. (d) Segura, J. L.; Mart´ın, N.;
Guldi, D. M. Chem. Soc. ReV. 2005, 34, 31. (e) Hoeben, F. J. M.; Jonkheijm,
P.; Meijer, E. W.; Schenning, A. P. H. J. Chem. ReV. 2005, 105, 1491.
10.1021/jo052602c CCC: $33.50 © 2006 American Chemical Society
Published on Web 03/07/2006
J. Org. Chem. 2006, 71, 2699-2705
2699

Katayama et al.
SCHEME 1. Synthesis of cis-OPV1-4a
a Reagents and conditions: (a) Pd(PPh3)4 (1.5 mol %), aq KOH, toluene, 80 °C; (b) Pd(PPh3)4 (1.5 mol %), aq KOH, THF, 60 °C.
olefins,1,2 the synthesis of all-cis analogues has not been
reported. Herein, we describe that both isomers of OPVs having
1-4 vinylene units are successfully prepared by palladium-
catalyzed cross-coupling reactions.
synthesized from 1b and 2a, whereas (Z,Z)-(2-bromoethenyl)-
stilbene 2c was prepared by 1:1 coupling of 1a and 2b in 53%
yield. In the former case, because diboronic acid 1b was poorly
soluble in toluene, 1:2 coupling of 1b and 2a to give cis-OPV2
predominated under the conditions (a). Therefore, the cross-
coupling reaction was performed in THF (condition (b)) using
a 2-fold excess of 1b against 2a, where (Z)-1c was formed in
35% yield. Finally, the resulting (Z)-1c and (Z,Z)-2c were treated
under the conditions (a), and cis-OPV3 with 98% geometrical
purity was isolated in 30% yield. cis-OPV4 was similarly
prepared by 1:2 coupling of 1b and 2c in 76% yield (eq 4).
Synthesis of trans-Oligo(phenylenevinylene)s. We previ-
ously reported that hydrosilylation of phenylacetylene with
HSiMe2Ar [Ar ) 3,5-(CF3)2C6H3] catalyzed by RuHCl(CO)-
(PPh3)3, followed by Hiyama coupling of the resulting styryl-
silane with phenyl iodide, causes highly stereoselective synthesis
of (E)-stilbene.6 A series of trans-OPVs was prepared by this
method (Schemes 2 and 3).
2,5-Dioctyloxyiodobenzene (3a) was treated with (E)-2-
silylethenylbenzene 4a in THF at room temperature in the
presence of TBAF‚3H2O and a catalytic amount of [Pd(η3-allyl)-
(µ-Cl)]2 for 24 h (eq 5). Column chromatographic purification
of the reaction product afforded trans-OPV1 in 71% yield.
Similarly, trans-OPV2 was prepared in 31% yield by the
reaction of 2 equiv of 3a with (E,E)-1,4-bis(2-silylethenyl)-
benzene 4b (eq 6).
Results and Discussion
Synthesis of cis-Oligo(phenylenevinylene)s. cis-OPV1-4
were synthesized by Suzuki-Miyaura coupling using four kinds
of starting materials, 1a, 1b, 2a, and 2b (Scheme 1). 2,5-
Dioctyloxybenzeneboronic acid (1a) reacted cleanly with (Z)-
styryl bromide (2a) in toluene at 80 °C in the presence of
Pd(PPh3)4 and aqueous KOH to afford cis-OPV1 in quantitative
yield (eq 1). Similarly, 2 equiv of 1a reacted with (Z,Z)-1,4-
bis(2-bromoethenyl)benzene (2b) to give cis-OPV2 with 98%
geometrical purity in 85% yield (eq 2). In this case, (Z,Z)-2b
as a substrate was prepared by bromodesilylation of (Z,Z)-1,4-
bis[2-(dimethylphenylsilyl)ethenyl]benzene (4b) with NBS.5
Therefore, the synthesis of cis-OPV2 was attempted by Hiyama
coupling of (Z,Z)-4b with 2 equiv of 2,5-dioctyloxyiodobenzene
(3a) in THF in the presence of a palladium catalyst and TBAF‚
3H2O. However, hydrodesilylation of (Z,Z)-4b induced by
fluoride ion took place to a considerable extent, giving 1,4-
divinylbenzene. This compound subsequently underwent the
Heck-type arylation with 3a to lead to trans-OPV2 (ca. 40%)
as a byproduct.
Next, boronic acid 1c and alkenyl bromide 2c were assembled
into cis-OPV3 (eq 3). (Z)-4-Styrylbenzeneboronic acid 1c was
trans-OPV3 and OPV4 were prepared by using (E,E)-4-(2-
silylethenyl)stilbene 4c as a common starting material (Scheme
2700 J. Org. Chem., Vol. 71, No. 7, 2006

StereoselectiVe Synthesis of cis- and trans-Oligo(phenyleneVinylene)s
SCHEME 2. Synthesis of trans-OPV1 and 2a
a SiMe2Ar ) SiMe2[C6H3(CF3)2-3,5]. Reagents and conditions: (a) [Pd(η3-allyl)(µ-Cl)]2 (5 mol %), TBAF‚3H2O (1 equiv), THF, rt.
SCHEME 3. Synthesis of trans-OPV3 and 4a
a SiMe2Ar ) SiMe2[C6H3(CF3)2-3,5]. Reagents and conditions: (a) [Pd(η3-allyl)(µ-Cl)]2 (5 mol %), TBAF‚3H2O (1 equiv), THF, rt; (b) HSiMe2Ar,
RuHCl(CO)(PPh3)3 (5 mol %), CH2Cl2, rt; (c) HCtCSiMe3, PdCl2(PPh3)2, CuI, NEt3, 60 °C; (d) aq KOH, MeOH, THF, rt.
3). This compound was obtained by the sequence of reactions
outlined in eq 7. Hydrosilylation of 4-bromophenylacetylene
(5) with HSiMe2Ar catalyzed by RuHCl(CO)(PPh3)3 in CH2-
Cl2 was completed in 1.5 h at room temperature to give (E)-6
in almost quantitative yield. The product was then coupled with
2,5-dioxyloxyiodobenzene (3a) under Hiyama coupling condi-
tions (a), giving (E)-4-bromostilbene 7 in 75% yield. Compound
7 was then converted to terminal acetylene 9 by Sonogashira
coupling with (trimethylsilyl)acetylene, followed by desilylation.
Finally, 9 was subjected to (E)-selective hydrosilylation cata-
lyzed by RuHCl(CO)(PPh3)3, and the desired compound 4c was
obtained in 68% overall yield starting from 5.
Treatment of (E,E)-4c with (E)-iodostilbene 3c, prepared by
1:1 coupling of 3b and 4a (eq 8), in THF in the presence TBAF‚
3H2O and [Pd(η3-allyl)(µ-Cl)]2 catalyst at room temperature for
15 h afforded trans-OPV3 in 57% yield (eq 9). On the other
hand, 2:1 coupling of 4c with 2,5-dioctyloxy-1,4-diiodobenzene
(3b) under almost the same reaction conditions formed trans-
OPV4 in 44% isolated yield (eq 10).
J. Org. Chem, Vol. 71, No. 7, 2006 2701

Katayama et al.
FIGURE 1. Changes of UV-vis absorption spectra of OPVs under photoirradiation in benzene: (a) OPV1 (from cis isomer), (b) OPV1 (from
trans isomer), (c) OPV2 (cis to trans), (d) OPV3 (cis to trans), (e) OPV4 (cis to trans).
Photoisomerization of OPV1-4. The cis- and trans-OPVs
thus prepared were dissolved in benzene (0.01 mM) in a quartz
cell and irradiated by a Xe lamp (λmax ) 365 nm, 0.87 mW
cm-2) under a nitrogen atmosphere at room temperature. The
sample solutions were monitored at intervals by UV-vis
spectroscopy as illustrated in Figure 1a-e. OPV1 underwent
two-way isomerization to give a mixture of the cis and trans
isomers in a 52:48 ratio [(a), (b)]. On the other hand, OPV2-4
underwent one-way isomerization from cis to trans isomer [(c),
(d), (e)]. 1H NMR analysis of the products revealed quantitative
(>99%) conversion of cis-OPV2-4 to the corresponding trans
isomers (see the Supporting Information). These observations
are consistent with the previous ones,4 particularly the report
for 4-styrylstilbene by Sandros et al.7 Further study of photo-
isomerization of OPVs, particularly focused on the mechanisms,
will be reported in due course.
Experimental Section
(Z)-2,5-Dioctyloxystilbene (cis-OPV1). To a solution of 1a (75.7
mg, 0.200 mmol) and 2a [(Z) > 99%] (38.4 mg, 0.210 mmol) in
toluene (1.0 mL) were successively added Pd(PPh3)4 (3.5 mmol,
3.0 µmol) and 3.0 M aqueous KOH (0.20 mL, 0.60 mmol). The
mixture was stirred at 80 °C for 7 h in the dark. The resulting pale
yellow solution was concentrated to dryness to give a yellow oil,
which was purified by flash column chromatography on silica gel
eluted with hexane/CH2Cl2 (7/1). Evaporation of the eluate afforded
cis-OPV1 with 99% geometrical purity as a pale yellow oil (86.9
(2) For recent studies on OPVs as emissive materials, see: (a) Lin,
H.-C.; Tsai, C.-M.; Huang, G.-H.; Lin, J.-M. J. Polym. Sci. Part A: Polym.
Chem. 2006, 44, 783. (b) Summers, M. A.; Bazan, G. C.; Buratto, S. K. J.
Am. Chem. Soc. 2005, 127, 16202. (c) Hoeben, F. J. M.; Schenning, A. P.
H. J.; Meijer, E. W. ChemPhysChem 2005, 6, 2337. (d) Varghese, R.;
George, S. J.; Ajayaghosh, A. Chem. Commun. 2005, 593. (e) Mahler, A.
K.; Schlick, H.; Saf, R.; Stelzer, F.; Meghdadi, F.; Pogantsch, A.; Leising,
G.; Mo¨ller, K.-C.; Besenhard, J. O. Macromol. Chem. Phys. 2004, 205,
1840. OPVs in photovoltaic cells, see: (f) Jorgensen, M.; Krebs, F. C. J.
Org. Chem. 2004, 69, 6688. (g) Ramos, A. M.; Beckers, E. H. A.;
Offermans, T.; Meskers, S. C. J.; Janssen, R. A. J. J. Phys. Chem. A 2004,
108, 8201. (h) Wurthner, F.; Chen, Z. J.; Hoeben, F. J. M.; Osswald, P.;
You, C. C.; Jonkheijm, P.; van Herrikhuyzen, J.; Schenning, A. P. H. J.;
van der Schoot, P. P. A. M.; Meijer, E. W.; Beckers, E. H. A.; Meskers, S.
C. J.; Janssen, R. A. J. J. Am. Chem. Soc. 2004, 126, 10611. (i) Melzer, C.;
Krasnikov, V. V.; Hadziioannou, G. J. Polym. Sci. Part B: Polym. Phys.
2003, 41, 2665. (j) Neuteboom, E. E.; Meskers, S. C. J.; van Hal, P. A.;
van Duren, J. K. J.; Meijer, E. W.; Janssen, R. A. J.; Dupin, H.; Pourtois,
G.; Cornil, J.; Lazzaroni, R.; Bredas, J. L.; Beljonne, D. J. Am. Chem. Soc.
2003, 125, 8625. For OPVs in functional supramolecular systems, see: (k)
George, S. J.; Ajayaghosh, A. Chem. Eur. J. 2005, 11, 3217. (l) Hulvat, J.
F.; Sofos, M.; Tajima, K.; Stupp, S. I. J. Am. Chem. Soc. 2005, 127, 366.
(m) Messmore, B. W.; Hulvat, J. F.; Sone, E. D.; Stupp, S. I. J. Am. Chem.
Soc. 2004, 126, 14452. (n) van Herrikhuyzen, J.; Syamakumari, A.;
Schenning, A. P. H. J.; Meijer, E. W. J. Am. Chem. Soc. 2004, 126, 10021.
(o) Ajayaghosh, A.; George, S. J.; Praveen, V. K. Angew. Chem., Int. Ed.
2003, 42, 332. (p) Ajayaghosh, A.; George, S. J. J. Am. Chem. Soc. 2001,
123, 5148. For other examples of synthesis and properties of OPVs, see:
(q) Jian, H.; Tour, J. M. J. Org. Chem. 2005, 70, 3396. (r) Xue, C.; Luo,
F.-T. J. Org. Chem. 2003, 68, 4417. (s) Stuhr-Hansen, N.; Christensen, J.
B.; Harrit, N.; Bjørnholm, T. J. Org. Chem. 2003, 68, 1275. (t) Gu, T.;
Ceroni, P.; Marconi, G.; Armaroli, N.; Nierengarten, J.-F. J. Org. Chem.
2001, 66, 6432. (u) Hilberer, A.; van Hutten, P. F.; Wildeman, J.;
Hadziioannou, G. Macromol. Chem. Phys. 1997, 198, 2211. (v) Koch, F.;
Heitz, W. Macromol. Chem. Phys. 1997, 198, 1531.
1
mg, 100% yield). H NMR (CDCl3): δ 7.28-7.11 (m, 5H), 6.79
(dd, J ) 7.1, 2.2 Hz, 1H), 6.73 (d, J ) 2.2 Hz, 1H), 6.72 (d, J )
7.1 Hz, 1H), 6.69 (d, J ) 12.4 Hz, 1H), 6.60 (d, J ) 12.4 Hz, 1H),
3.90 (t, J ) 6.6 Hz, 2H), 3.60 (t, J ) 6.6 Hz, 2H), 1.75-1.66 (m,
2H), 1.63-1.54 (m, 2H), 1.44-1.22 (m, 20 H), 0.88 (t, J ) 6.4
Hz, 6H). 13C NMR (CDCl3): δ 152.4, 151.0, 137.4, 130.0, 128.8,
128.0, 127.0, 126.9, 125.7, 115.5, 115.3, 113.6, 69.3, 68.4, 31.8,
29.4, 29.3, 29.2, 29.1, 26.1, 26.0, 22.7, 14.1. Anal. Calcd for
C30H44O2: C, 82.52; H, 10.16. Found: C, 82.51; H, 10.16.
1,4-Bis[(Z)-2,5-dioctyloxystyryl]benzene (cis-OPV2). This com-
pound was synthesized similarly to cis-OPV1, starting from 1a (279
(3) Katayama, H.; Nagao, M.; Nishimura, T.; Matsui, Y.; Umeda, K.;
Akamatsu, K.; Tsuruoka, T.; Nawafune, H.; Ozawa, F. J. Am. Chem. Soc.
2005, 127, 4350.
(4) Arai, T.; Tokumaru, K. Chem. ReV. 1993, 93, 23.
(5) Nagao, M.; Asano, K.; Umeda, K.; Katayama, H.; Ozawa, F. J. Org.
Chem. 2005, 70, 10511.
(6) (a) Katayama, H.; Taniguchi, K.; Kobayashi, M.; Sagawa, T.; Minami,
T.; Ozawa, F. J. Organomet. Chem. 2002, 645, 192. (b) Katayama, H.;
Nagao, M.; Moriguchi, R.; Ozawa, F. J. Organomet. Chem. 2003, 676, 49.
(7) Sandros, K.; Sundahl, M.; Wennerstro¨m, O.; Norinder, U. J. Am.
Chem. Soc. 1990, 112, 3082.
2702 J. Org. Chem., Vol. 71, No. 7, 2006

StereoselectiVe Synthesis of cis- and trans-Oligo(phenyleneVinylene)s
mg, 0.736 mmol), 2b [(Z,Z) > 99%] (79.5 mg, 0.276 mmol), toluene
(2.7 mL), Pd(PPh3)4 (4.7 mg, 4.1 µmol), and 3.0 M aqueous KOH
(0.60 mL, 1.8 mmol). The reaction was completed after 40 h. After
chromatographic purification using hexane/CH2Cl2 (2/1) as an
eluent, a yellow solid of cis-OPV2 [(Z,Z) ) 98%] was obtained
29.2, 29.2, 29.1, 26.1, 26.0, 25.9, 22.7, 14.1. Anal. Calcd for
C62H88O4: C, 82.98; H, 9.88. Found: C, 83.06; H, 9.89.
1,4-Bis[(Z)-4-[(Z)-2,5-dioctyloxystyryl]styryl]-2,5-dioctyloxy-
benzene (cis-OPV4). This compound was synthesized similarly
to cis-OPV1, starting from 1b (90.1 g, 0.213 mmol), 2c [(Z,Z) )
98%] (232 mg, 0.428 mmol), toluene (2.1 mL), Pd(PPh3)4 (3.7 mg,
3.2 µmol), and 3.0 M aqueous KOH (0.21 mL, 0.63 mmol). The
reaction was completed after 41 h. After chromatographic purifica-
tion using hexane/CH2Cl2 (1/1) as an eluent, and then recycle GPC,
a yellow solid of cis-OPV4 [(Z,Z,Z,Z) ) 96%] was obtained (204
mg, 76%). Mp: 96 °C. 1H NMR (CDCl3): δ 7.17 (d, J ) 9.5 Hz,
4H), 7.14 (d, J ) 9.5 Hz, 4H), 6.78 (d, J ) 8.9 Hz, 2H), 6.76 (d,
J ) 3.3 Hz, 2H), 6.75 (s, 2H), 6.71 (dd, J ) 8.9, 3.3 Hz, 2H), 6.64
(d, J ) 12.5 Hz, 2H), 6.63 (d, J ) 12.3 Hz, 2H), 6.51 (d, J ) 12.5
Hz, 2H), 6.49 (d, J ) 12.3 Hz, 2H), 3.89 (t, J ) 6.5 Hz, 4H), 3.65
(t, J ) 6.7 Hz, 4H), 3.53 (t, J ) 6.5 Hz, 4H), 1.75-1.38 (m, 12H)
1.24 (br, 60H), 0.89-0.85 (m, 18H). 13C NMR (CDCl3): δ 152.5,
150.9, 150.1, 136.2, 136.0, 129.7, 129.5, 128.6, 127.2, 126.2, 125.7,
125.3, 115.7, 115.0, 113.9, 113.5, 69.2, 68.8, 68.5, 31.8, 29.4, 29.3,
29.3, 29.2, 26.1, 26.0, 22.7, 14.1. Anal. Calcd for C86H126O6: C,
82.24; H, 10.11. Found: C, 82.00; H, 10.16.
1
(188 mg, 85%). Mp: 72 °C. H NMR (CDCl3): δ 7.12 (s, 4H),
6.78 (d, J ) 8.7 Hz, 2H), 6.77 (d, J ) 3.0 Hz, 2H), 6.70 (dd, J )
8.7, 3.0 Hz, 2H), 6.63 (d, J ) 12.3 Hz, 2H), 6.51 (d, J ) 12.3 Hz,
2H), 3.88 (t, J ) 6.6 Hz, 4H), 3.65 (t, J ) 6.6 Hz, 4H), 1.74-1.54
(m, 4H), 1.45-1.26 (m, 20H), 0.88 (t, J ) 7.1 Hz, 6H), 0.87 (t, J
) 7.0 Hz, 6H). 13C NMR (CDCl3): δ 152.5, 150.9, 136.0, 129.8,
128.6, 127.2, 125.6, 115.6, 115.1, 113.5, 69.2, 68.5, 31.8, 29.4,
29.3, 29.2, 26.1, 26.0, 22.7, 14.1. Anal. Calcd for C54H82O4: C,
81.56; H, 10.39. Found: C, 81.38; H, 10.52.
(Z)-2,5-Dioctyloxystilbene-4-boronic Acid (1c). This compound
was synthesized similarly to cis-OPV1, starting from 1b (3.38 g,
8.01 mmol), 2a [(Z) > 99%] (738 mg, 4.03 mmol), THF (80 mL),
Pd(PPh3)4 (34.7 mg, 30.0 µmol), and 3.0 M aqueous KOH (4.00
mL, 12.0 mmol). The reaction was completed after 2 h. After
chromatographic purification using hexane/AcOEt (10/1) as an
eluent, and then recrystallization from hexane, a white solid of 1c
(E)-2,5-Dioctyloxystilbene (trans-OPV1). To a solution of 3a
(206 mg, 0.447 mmol) and 4a [(E) > 99%] (205 mg, 0.548 mmol)
in THF (1.7 mL) were successively added [Pd(η3-allyl)(µ-Cl)]2 (8.4
mg, 23 µmol) and 1.0 M solution of TBAF‚3H2O in THF (0.55
mL, 0.55 mmol). The mixture was stirred at rt for 24 h and then
evaporated by pumping. The oily residue was subjected to flash
column chromatography on silica gel eluted with hexane/AcOEt
(50/1) to give trans-OPV1 [(E) > 99%] as pale yellow oil
containing small amounts of contaminant arise from silicon
compounds. Further purification was performed by recycle GPC
to give trans-OPV1 [(E) > 99%] as a colorless oil (138 mg, 71%).
Identification data was consistent with the literature.2u 1H NMR
(CDCl3): δ 7.53-7.51 (m, 5H), 7.46 (d, J ) 16.5 Hz, 1H), 7.38-
7.33 (m, 5H), 7.26-7.22 (m, 5H), 7.15 (d, J ) 2.9 Hz, 1H), 7.11
(d, J ) 16.5 Hz, 1H), 6.83 (d, J ) 9.0 Hz, 1H), 6.76 (dd, J ) 9.0,
2.9 Hz, 1H), 3.96 (t, J ) 6.4 Hz, 2H), 3.95 (t, J ) 6.6 Hz, 2H),
1.87-1.73 (m, 4H), 1.54-1.21 (m, 20H), 0.91-0.86 (m, 6H). Anal.
Calcd for C30H44O2: C, 82.52; H, 10.16. Found: C, 82.43; H, 10.18.
1,4-Bis[(E)-2,5-dioctyloxystyryl]benzene (trans-OPV2). This
compound was synthesized similarly to trans-OPV1, starting from
3a (193 mg, 0.420 mmol), 4b [(E,E) > 99%] (134 mg, 0.200
mmol), THF (1.6 mL), [Pd(η3-allyl)(µ-Cl)]2 (3.7 mg, 10 µmol),
and 1.0 M solution of TBAF‚3H2O in THF (0.40 mL, 0.40 mmol).
The reaction was completed after 24 h. After chromatographic
purification using hexane/AcOEt (50/1) as an eluent, and then
recycle GPC, a yellow solid of trans-OPV2 [(E,E) > 99%] was
obtained (50 mg, 32%). Identification data was consistent with the
literature.2u 1H NMR (CDCl3): δ 7.50 (s, 4H), 7.48 (d, J ) 16.5
Hz, 1H), 7.15 (d, J ) 2.9 Hz, 1H), 7.11 (d, J ) 16.5 Hz, 1H), 6.83
(d, J ) 8.8 Hz, 1H), 6.76 (dd, J ) 8.8, 2.9 Hz, 1H), 3.97 (t, J )
6.4 Hz, 2H), 3.96 (t, J ) 6.5 Hz, 2H), 1.88-1.74 (m, 4H), 1.55-
1.25 (m, 20H), 0.91-0.87 (m, 6H). Anal. Calcd for C54H82O4: C,
81.56; H, 10.39. Found: C, 81.35; H, 10.52.
Dimethyl[3,5-bis(trifluoromethyl)phenyl][(E)-4-bromostyryl]-
silane (6). To a solution of (4-bromophenyl)acetylene (1.58 g, 8.73
mmol) and dimethyl[3,5-bis(trifluoromethyl)phenyl]silane (4.75 g,
17.5 mmol) in CH2Cl2 (44 mL) was added RuHCl(CO)(PPh3)3 (416
mg, 0.437 mmol). The mixture was stirred at room temperature
for 1.5 h and then evaporated by pumping. The oily residue was
subjected to flash column chromatography on silica gel eluted with
hexane to give 6 [(E) > 99%] as a colorless oil (3.83 g, 97%). 1H
NMR (CDCl3): δ 7.94 (br, 2H), 7.87 (br, 1H), 7.50-7.46 (m, 4H),
7.34-7.30 (m, 4H), 6.90 (d, J ) 19.2 Hz, 1H), 6.51 (d, J ) 19.2
Hz, 1H), 0.50 (s, 6H). 13C NMR (CDCl3): δ 145.5, 142.0, 136.4,
133.5, 131.8, 130.8, 128.1, 125.6, 123.5, 123.0, 121.7, -3.0. MS,
m/z (rel intensity): 454, 452 (M+, 5, 5), 439 (7), 436 (6), 358 (18),
356 (18), 277 (27), 257 (25), 225 (15), 223 (14), 145 (9), 143 (10),
102 (11), 81 (15), 77 (100), 75 (14), 59 (14), 51 (12), 44 (23), 43
1
[(Z) ) 97%] was obtained (666 mg, 35%). Mp: 69 °C. H NMR
(CDCl3): δ 7.42-7.11 (m, 5H), 7.31 (s, 1H), 6.75 (d, J ) 12.3
Hz, 1H), 6.70 (s, 1H), 6.68 (d, J ) 12.3 Hz, 1H), 5.81 (s, 2H),
3.99 (d, J ) 6.6 Hz, 2H), 3.56 (d, J ) 6.6 Hz, 2H), 1.79-1.70 (m,
4H), 1.62-1.54 (m, 4H), 1.45-1.26 (m, 20H), 0.89 (t, J ) 6.6
Hz, 3H), 0.88 (t, J ) 6.6 Hz, 3H). 13C NMR (CDCl3): δ 157.3,
151.1, 137.4, 130.9, 130.2, 128.9, 128.2, 127.0, 125.6, 119.5, 113.0,
69.1, 68.6, 31.8, 31.8, 29.4, 29.2, 29.1, 29.0, 26.1, 25.8, 22.7, 22.6,
14.1. Anal. Calcd for C30H45BO4: C, 74.99; H, 9.44. Found: C,
74.89; H, 9.55.
(Z)-4′-[(Z)-2-Bromoethenyl]-2,5-dioctyloxystilbene (2c). This
compound was synthesized similarly to cis-OPV1, starting from
1a (945 mg, 2.50 mmol), 2b [(Z,Z) > 99%] (864 mg, 3.00 mmol),
toluene (13 mL), Pd(PPh3)4 (43.3 mg, 37.5 µmol), and 3.0 M
aqueous KOH (2.50 mL, 7.50 mmol). The reaction was completed
after 24 h. After chromatographic purification using hexane/AcOEt
(50/1) as an eluent, a fluorescent yellow solid of 1c [(Z,Z) ) 98%]
1
was obtained (710 mg, 53%). Mp: 40 °C. H NMR (CDCl3): δ
7.55 (d, J ) 8.4 Hz, 2H), 7.28 (d, J ) 8.4 Hz, 2H), 7.00 (d, J )
8.1 Hz, 1H), 6.82-6.72 (m, 3H), 6.71 (d, J ) 12.3 Hz, 1H), 6.57
(d, J ) 12.3 Hz, 1H), 6.38 (d, J ) 8.1 Hz, 1H), 3.90 (t, J ) 6.6
Hz, 2H), 3.64 (t, J ) 6.6 Hz, 2H), 1.71-1.56 (m, 4H), 1.34-1.26
(m, 20H), 0.88 (m, 6H). 13C NMR (CDCl3): δ 152.5, 150.9, 137.6,
133.4, 132.0, 129.5, 128.7, 126.9, 126.5, 115.5, 113.6, 105.9, 69.3,
68.5, 31.8, 31.8, 29.4, 29.3, 29.2, 29.2, 26.1, 25.9, 22.7, 14.1. Anal.
Calcd for C32H45BrO2: C, 70.96; H, 8.37. Found: C, 71.10; H,
8.42.
(Z)-2,5-Dioctyloxy-4′-[(Z)-2,5-dioctyloxy-4-[(Z)-styryl]styryl]-
stilbene (cis-OPV3). This compound was synthesized similarly to
cis-OPV1, starting from 1c [(Z) ) 97%] (217 mg, 0.401 mmol),
2c [(Z,Z) ) 98%] (193 mg, 0.402 mmol), toluene (2.0 mL), Pd-
(PPh3)4 (3.5 mg, 3.0 µmol), and 3.0 M aqueous KOH (0.20 mL,
0.60 mmol). The reaction was completed after 24 h. After
chromatographic purification using hexane/AcOEt (10/1) as an
eluent, and then recycle GPC, a yellow solid of cis-OPV3 [(Z) )
98%] was obtained (109 mg, 30%). Mp: 66 °C. 1H NMR
(CDCl3): δ 7.31-7.13 (m, 5H), 7.16 (s, 4H), 6.79 (d, J ) 8.7 Hz,
1H), 6.77 (d, J ) 3.3 Hz, 1H), 6.75 (s, 1H), 6.71 (dd, J ) 8.7, 3.3
Hz, 1H), 6.69 (d, J ) 12.5 Hz, 1H), 6.68 (s, 1H), 6.64 (d, J ) 12.5
Hz, 1H), 6.62 (d, J ) 12.3 Hz, 1H), 6.59 (d, J ) 12.5 Hz, 1H),
6.52 (d, J ) 12.5 Hz, 1H), 6.50 (d, J ) 12.3 Hz, 1H), 3.89 (t, J )
6.5 Hz, 2H), 3.65 (t, J ) 6.6 Hz, 2H), 3.55 (t, J ) 6.5 Hz, 2H),
3.47 (t, J ) 6.6 Hz, 2H), 1.75-1.38 (m, 8H) 1.25 (br, 40H), 0.89-
0.86 (m, 12H). 13C NMR (CDCl3): δ 152.4, 150.9, 150.1, 150.0,
137.7, 136.2, 136.0, 129.8, 129.7, 129.6, 128.9, 128.6, 128.6, 128.1,
127.2, 126.9, 126.1, 126.1, 125.7, 125.4, 125.3, 115.7, 115.0, 114.0,
114.0, 113.5, 69.3, 68.9, 68.7, 68.5, 31.8, 29.4, 29.3, 29.3, 29.2,
J. Org. Chem, Vol. 71, No. 7, 2006 2703

Katayama et al.
(19), 40 (53). Anal. Calcd for C8H15O6BrFSi: C, 47.69; H, 3.34.
Found: C, 47.93; H, 3.29.
6.83 (d, J ) 9.0 Hz, 1H), 6.77 (dd, J ) 9.0, 2.7 Hz, 1H), 6.51 (d,
J ) 19.1 Hz, 1H), 3.97 (t, J ) 6.4 Hz, 2H), 3.95 (t, J ) 6.5 Hz,
2H), 1.87-1.73 (m, 4H), 1.52-1.24 (br, 20H), 0.91-0.85 (m, 6H),
0.51 (s, 6H). 13C NMR (CDCl3): δ 153.2, 151.0, 146.4, 142.4,
138.4, 136.6, 133.6, 130.7, 128.4, 127.3, 127.0, 126.8, 124.0, 124.0,
122.9, 123.6, 114.7, 113.8, 112.2, 69.5, 68.6, 31.8, 29.4, 29.4, 29.3,
29.3, 26.3, 26.1, 22.7, 14.1, 14.1, -2.7. Anal. Calcd for C42H54F6O2-
Si: C, 68.82; H, 7.43. Found: C, 68.82; H, 7.47.
(E)-4′-Bromo-2,5-dioctyloxystilbene (7). This compound was
synthesized similarly to trans-OPV1, starting from 6 [(E) > 99%]
(2.33 g, 5.14 mmol), 3a (2.40 g, 5.21 mmol), THF (26 mL), [Pd-
(η3-allyl)(µ-Cl)]2 (94.0 mg, 257 µmol), and 1.0 M solution of
TBAF‚3H2O in THF (5.2 mL, 5.2 mmol). The reaction was
completed after 10 h. After chromatographic purification using
hexane/CH2Cl2 (10/1) as an eluent, a yellow oil of 7 [(E) > 99%]
(E)-2,5-Dioctyloxy-4-iodostilbene (3c). This compound was
synthesized similarly to trans-OPV1, starting from 3b (1.13 g, 1.92
mmol), 4a [(E) > 99%] (606 mg, 1.62 mmol), THF (6.4 mL), [Pd-
(η3-allyl)(µ-Cl)]2 (14.6 mg, 400 µmol), and 1.0 M solution of
TBAF‚3H2O in THF (1.6 mL, 1.6 mmol). The reaction was
completed after 14 h. After chromatographic purification using
hexane/AcOEt (50/1) as an eluent, and then recycle GPC, an orange
1
was obtained (2.00 g, 75%). H NMR (CDCl3): δ 7.49-7.46 (m,
4H), 7.39-7.36 (m, 4H), 7.43 (d, J ) 16.6 Hz, 1H), 7.12 (d, J )
2.7 Hz, 1H), 7.04 (d, J ) 16.6 Hz, 1H), 6.82 (d, J ) 9.0 Hz, 1H),
6.78 (dd, J ) 9.0, 2.7 Hz, 1H), 3.96 (t, J ) 6.4 Hz, 2H), 3.94 (t,
J ) 6.6 Hz, 2H), 1.86-1.71 (m, 4H), 1.51-1.22 (br, 20H), 0.90-
0.86 (m, 6H). 13C NMR (CDCl3): δ 153.2, 150.9, 136.8, 131.6,
128.0, 127.2, 127.0, 124.3, 121.0, 114.7, 113.8, 112.4, 69.4, 68.6,
31.8, 31.8, 29.4, 29.4, 29.3, 29.3, 26.2, 26.1, 22.7, 14.1. Anal. Calcd
for C30H43BrO2: C, 69.89; H, 8.41. Found: C, 69.92; H, 8.39.
(E)-2,5-Dioctyloxy-4′-[(trimethylsilyl)ethynyl]stilbene (8). To
a solution of 7 (1.99 g, 3.86 mmol) in NEt3 (19 mL) were
successively added PdCl2(PPh3)2 (108 mg, 0.154 mmol), CuI (29.4
mg, 154 mmol), and (trimethylsilyl)acetylene (818 µL, 5.79 mmol).
The mixture was stirred at 60 °C for 17 h. The resulting dark green
suspension was filtered, and volatile materials were removed by
pumping. The oily residue was poured into water and then extracted
with ether (100 mL × 3). The combined organic extracts were
washed with brine and dried over MgSO4. The drying agent was
filtered off, and the resulting filtrate was evaporated to give a brown
solid, which was subjected to flash column chromatography on silica
gel eluted with hexane/benzene (5/1) to give 8 (2.00 g, 97%) as a
1
oil of 3c [(E) > 99%] was obtained (270 mg, 30%). H NMR
(CDCl3): δ 7.53-7.51, 7.38-7.33 (m, 5H), 7.39 (d, J ) 16.7 Hz,
1H), 7.28 (s, 1H), 7.12 (d, J ) 16.7 Hz, 1H), 7.03 (s, 1H), 4.02 (t,
J ) 6.4 Hz, 2H), 3.95 (t, J ) 6.5 Hz, 2H), 1.89-1.78 (m, 4H),
1.55-1.26 (br, 20H), 0.91-0.86 (m, 6H). 13C NMR (CDCl3): δ
152.2, 151.3, 137.6, 129.4, 128.6, 127.6, 127.5, 126.5, 123.6, 123.1,
109.1, 85.8, 70.2, 69.6, 31.8, 31.8, 29.3, 29.3, 29.3, 26.2, 26.1, 22.7,
14.1, 14.1. Anal. Calcd for C30H43IO2: C, 64.05; H, 7.70. Found:
C, 64.01; H, 7.61.
(E)-2,5-Dioctyloxy-4′-[(E)-2,5-dioctyloxy-4-[(E)-styryl]styryl]-
stilbene (trans-OPV3). This compound was synthesized similarly
to trans-OPV1, starting from 3c [(E) > 99%] (246 mg, 0.437
mmol), 4c [(E,E) > 99%] (338 mg, 0.461 mmol), THF (1.8 mL),
[Pd(η3-allyl)(µ-Cl)]2 (9.0 mg, 24 µmol), and 1.0 M solution of
TBAF‚3H2O in THF (0.46 mL, 0.46 mmol). The reaction was
completed after 15 h. After chromatographic purification using
hexane/AcOEt (50/1) as an eluent, and then recycle GPC, a yellow
solid of trans-OPV3 [(E,E,E) > 99%] was obtained (222 mg, 57%).
1
yellow oil. H NMR (CDCl3): δ 7.47 (d, J ) 16.5 Hz, 1H), 7.44
(s, 4H), 7.13 (d, J ) 2.6 Hz, 1H), 7.08 (d, J ) 16.5 Hz, 1H), 6.83
(d, J ) 8.4 Hz, 1H), 6.77 (dd, J ) 8.4, 2.6 Hz, 1H), 3.97 (d, J )
6.4 Hz, 2H), 3.95 (d, J ) 6.4 Hz, 2H), 1.87-1.73 (m, 4H), 1.56-
1.25 (br, 20H), 0.91-0.86 (m, 6H), 0.26 (s, 9H). 13C NMR
(CDCl3): δ 153.2, 151.0, 138.1, 132.2, 128.3, 127.1, 126.2, 124.5,
121.7, 114.8, 113.8, 112.3, 105.3, 94.8, 69.5, 68.6, 31.8, 31.8, 29.4,
29.4, 29.3, 29.4, 26.2, 26.1, 14.1, 0.0. Anal. Calcd for C35H52-
O2Si: C, 78.89; H, 9.84. Found: C, 78.95; H, 9.98.
1
Mp: 56 °C. H NMR (CDCl3): δ 7.55-7.52 (m, 2H), 7.52 (s,
8H), 7.50 (d, J ) 16.3 Hz, 2H), 7.49 (d, J ) 16.1 Hz, 2H), 7.48
(d, J ) 16.1 Hz, 1H), 7.39-7.43 (m, 2H), 7.28-7.23 (m, 1H),
7.16 (d, J ) 3.0 Hz, 1H), 7.14 (d, J ) 16.1 Hz, 2H), 7.14 (s, 2H),
7.12 (d, J ) 16.3 Hz, 1H), 6.83 (d, J ) 8.9 Hz, 2H), 6.77 (dd, J )
8.9, 2.9 Hz, 2H), 4.07 (t, J ) 6.5 Hz, 4H), 3.98 (t, J ) 6.5 Hz,
2H), 3.96 (t, J ) 6.5 Hz, 2H), 1.93-1.74 (m, 12H), 1.61-1.24
(br, 60H), 0.91-0.87 (m, 18H). 13C NMR (CDCl3): δ 153.2, 151.1,
150.9, 137.9, 137.1, 128.7, 128.6, 128.4, 127.5, 127.4, 126.9, 126.8,
126.8, 126.5, 123.5, 123.4, 123,1, 114.4, 113.8, 112.2, 110.6, 110.5,
69.6, 69.5, 68.6, 31.8, 29.5, 29.4, 29.4, 29.3, 29.3, 29.3, 26.3, 26.3,
26.1, 22.7, 14.1. Anal. Calcd for C62H88O4: C, 82.98; H, 9.88.
Found: C, 82.60; H, 9.91.
(E)-2,5-Dioctylocy-4′-ethynylstilbene (9). To a solution of 8
(2.00 g, 3.75 mmol) in MeOH/THF (2/1, 62 mL) was added 0.8 M
aqueous KOH (5.6 mL, 4.5 mmol). The mixture was stirred at room
temperature for 2 h. The resulting yellow solution was evaporated
under reduced pressure. The oily residue was added H2O (100 mL)
and extracted with ether (100 mL × 3). The combined organic
extracts were washed with brine and dried over MgSO4. The drying
agent was filtered off, and the filtrate was evaporated to give an
orange oil, which was subjected to flash column chromatography
on silica gel eluted with hexane/CH2Cl2 (1/1) to give 9 (1.73 g,
100%) as a yellow oil. 1H NMR (CDCl3): δ 7.48 (d, J ) 16.6 Hz,
1H), 7.46 (s, 4H), 7.13 (d, J ) 2.7 Hz, 1H), 7.08 (d, J ) 16.6 Hz,
1H), 6.83 (d, J ) 8.8 Hz, 1H), 6.78 (dd, J ) 8.8, 2.7 Hz, 1H), 3.96
(t, J ) 6.5 Hz, 2H), 3.95 (t, J ) 6.5 Hz, 2H), 3.12 (s, 1H), 1.87-
1.72 (m, 4H), 1.55-1.26 (br, 20H), 0.90-0.86 (m, 6H). 13C NMR
(CDCl3): δ 153.2, 151.0, 138.4, 132.4, 128.1, 127.0, 126.3, 124.8,
120.7, 114.9, 113.8, 112.4, 83.8, 77.7, 69.5, 68.6, 31.8, 29.4, 29.4,
29.3, 29.3, 26.2, 26.1, 22.7, 14.1. Anal. Calcd for C32H44O2: C,
83.43; H, 9.63. Found: C, 83.20; H, 9.72.
(E)-2,5-Dioctyloxy-4′-[(E)-2-[dimethyl(3,5-bis(trifluorometh-
yl)phenyl)silyl]ethenyl]stilbene (4c). This compound was synthe-
sized similarly to 6, starting from 9 (408 mg, 0.886 mmol),
dimethyl[3,5-bis(trifluoromethyl)phenyl]silane (548 mg, 2.01 mmol),
CH2Cl2 (5.0 mL), and RuHCl(CO)(PPh3)3 (47.6 mg, 50.0 µmol).
The reaction was completed after 1 h. After chromatographic
purification using hexane as eluent, a yellow solid of 4c [(E,E) >
99%] was obtained (628 mg, 98%). Mp: 39 °C. 1H NMR
(CDCl3): δ 7.96 (br, 2H), 7.86 (br, 1H), 7.50 (d, J ) 8.2 Hz, 2H),
7.48 (d, J ) 16.5 Hz, 1H), 7.44 (d, J ) 8.2 Hz, 2H), 7.14 (d, J )
2.7 Hz, 1H), 7.10 (d, J ) 16.5 Hz, 1H), 6.98 (d, J ) 19.1 Hz, 1H)
1,4-Bis[(E)-4-[(E)-2,5-dioctyloxystyryl]styryl]-2,5-dioctyloxy-
benzene (trans-OPV4). This compound was synthesized similarly
to trans-OPV1, starting from 3b (157 mg, 0.265 mmol), 4c [(E,E)
> 99%] (427 mg, 0.582 mmol), THF (2.1 mL), [Pd(η3-allyl)(µ-
Cl)]2 (4.9 mg, 13 µmol), and 1.0 M solution of TBAF‚3H2O in
THF (0.58 mL, 0.58 mmol). The reaction was completed after 15
h. After chromatographic purification using hexane/CH2Cl2 (2/1)
as an eluent, and then recycle GPC, a yellow solid of trans-OPV4
1
[(E,E,E,E) > 99%] was obtained (143 mg, 44%). Mp: 90 °C. H
NMR (CDCl3): δ 7.52 (s, 8H), 7.50 (d, J ) 16.3 Hz, 2H), 7.48 (d,
J ) 16.3 Hz, 2H), 7.16 (d, J ) 2.9 Hz, 2H), 7.14 (d, J ) 16.3 Hz,
2H), 7.14 (s, 2H), 7.12 (d, J ) 16.3 Hz, 2H), 6.83 (d, J ) 8.9 Hz,
2H), 6.77 (dd, J ) 8.9, 2.9 Hz, 2H), 4.07 (t, J ) 6.5 Hz, 4H), 3.98
(t, J ) 6.5 Hz, 2H), 3.96 (t, J ) 6.5 Hz, 2H), 1.93-1.74 (m, 12H),
1.61-1.24 (br, 60H), 0.92-0.87 (m, 18H). 13C NMR (CDCl3): δ
153.3, 151.1, 150.9, 137.1, 137.1, 128.7, 128.4, 127.5, 126.9, 126.8,
126.8, 123.3, 123.2, 114.5, 113.8, 112.2, 110.5, 69.6, 69.5, 68.6,
31.8, 29.5, 29.4, 29.4, 29.3, 29.3, 29.3, 26.3, 26.3, 26.1, 22.7, 14.1.
Anal. Calcd for C86H126O6: C, 82.24; H, 10.11. Found: C, 82.14;
H, 10.23.
Photoirradiation. A benzene solution of OPV (0.01 mM) was
prepared in a quartz cell. Nitrogen gas was bubbled through the
2704 J. Org. Chem., Vol. 71, No. 7, 2006

StereoselectiVe Synthesis of cis- and trans-Oligo(phenyleneVinylene)s
solution at room temperature for 5 min. A Xe lamp (λ ) 365 nm,
0.87 mW cm-2) was used to irradiate the sample, and the
photoisomerization was monitored by UV-vis absorption spec-
troscopy. The photoirradiation experiment was also performed with
a more concentrated solution of OPV (0.10 mM) and a stronger
UV light (21 mW cm-2). After irradiation for 60 min under a
nitrogen atmosphere, the solution was evaporated by pumping, and
the residue was analyzed by 1H NMR spectroscopy (see the
Supporting Information).
Acknowledgment. This work was supported by a Grant-in
Aid for Scientific Research from the Ministry of Education,
Culture, Sports, Science and Technology, Japan.
Supporting Information Available: General experimental
method. Copies of 1H and 13C{1H} NMR spectra of all new
compounds. This material is available free of charge via the Internet
at http://pubs.acs.org.
JO052602C
J. Org. Chem, Vol. 71, No. 7, 2006 2705