Synthesis of a photochromic conjugated polymer incorporating spirobenzopyran in the backbone

Article abstract of DOI:10.1055/s-2006-942529

Photochromic conjugated polymer with photochemically isomerizable spirobenzopyran (SP) moiety as part of the conjugated backbone was synthesized. Upon irradiation with UV light of 365 nm, a new absorption band appeared above 500 nm due to the formation of

Full text of DOI:10.1055/s-2006-942529

PAPER
3075
Synthesis of a Photochromic Conjugated Polymer Incorporating
Spirobenzopyran in the Backbone
A
P
hotoch
i
romic
n
h
olymer
w
ith
u
Spirobenzo
a
Ybone ang, Man-Kit Ng*
Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
Fax +1(585)2760205; E-mail: ng@chem.rochester.edu
Received 30 March 2006; revised 13 May 2006
chemically allowed electrocyclic reactions. In this paper,
we report our preliminary effort in the design and synthe-
sis of a new spirobenzopyran-based polymer system with
photochromic units incorporated in the backbone of a typ-
Abstract: Photochromic conjugated polymer with photochemical-
ly isomerizable spirobenzopyran (SP) moiety as part of the conju-
gated backbone was synthesized. Upon irradiation with UV light of
365 nm, a new absorption band appeared above 500 nm due to the
formation of the merocyanine (MC) form, which corresponds to a ical conjugated polymer, poly(p-phenylene ethynylene)
highly conjugated structure.
(PPE). While typical photochromes such as derivatives of
spirobenzopyran, 1,2-dithienylethene, and azobenzene
have been frequently employed in a number of photochro-
mic polymeric or dendritic systems,4–6 the specific incor-
poration of spirobenzopyran units into part of the p-
conjugated polymer backbone (rather than as moieties on
the side chains) that would lead to a linear polymer capa-
ble of completing full conjugation along the polymer
backbone in the merocyanine form is new. The general
synthetic strategy leading to the spirobenzopyran-contain-
ing PPE (based on palladium-catalyzed cross-coupling)
outlined in this paper should be readily applicable to the
synthesis of other interesting conjugated polymers such as
poly(3-alkylthiophenes) (PT), poly(p-phenylene vinyl-
enes) (PPV) and poly(p-phenylenes) (PP) as well.
Keywords: conjugation, cross-coupling, isomerizations, polymers,
spiro compounds
p-Conjugated semi-conducting polymers represent a nov-
el class of organic semi-conductive materials that have
been intensively investigated because of their interesting
optoelectronic properties and potential applications in
several technologically important areas such as all-organ-
ic field-effect transistors, organic light-emitting devices,
solar cells, photoconductive materials, nonlinear optical
materials, and sensors.1 Photochromism is a phenomenon
associated with light-induced reversible isomerization of
a molecular species between two isomeric forms having
different absorption properties.2 The spirobenzopyran
family constitutes one of the most widely studied photo-
chromic systems due to their ease of synthesis and poten-
tial applications in optical information storage and
processing, molecular switching, memory devices, and
other emerging technologies.3 The photochromism of
spirobenzopyran is associated with a reversible color
change between the closed-ring (colorless) spiropyran
(SP) structure and the open-ring (highly colored) merocy-
anine (MC) form.4
The synthesis of polymer 9 was carried out following the
reaction sequences described in Schemes 1– 4. The two
monomers needed for the palladium-catalyzed (Sono-
gashira cross-coupling) condensative polymerization are
1,4-diiodobenzene and bis(acetylene) 8. The long alkoxy
chains introduced on the aromatic rings in monomer 8
serve to increase the solubility of the resulting rigid rod-
like segmented PPE polymer. It is noteworthy that a con-
venient protecting group (hydroxymethylethynyl group)
for masking terminal acetylenic functionality was suc-
cessfully used in the synthesis of various terminal acety-
lenes in this work, in good agreement with previous work
reported by Godt and coworkers.7 This masked protecting
group can be deprotected under relatively mild conditions
by simply stirring with a mixture of commercial manga-
nese dioxide (20 equiv) and powdered potassium hydrox-
ide (10 equiv) in dichloromethane or diethyl ether at room
temperature. This condition is mild when compared to the
conditions normally required for the deprotection of the 2-
hydroxyprop-2-yl moiety where a strong base (NaOH,
KOH, or NaH) in refluxing toluene or alcohol is used.8 In
addition, the corresponding acetylene starting material
used (propargyl alcohol) is inexpensive when compared
with the more commonly used silyl-substituted terminal
acetylenes such as trimethylsilylacetylene or triisopropyl-
silylacetylene. In our case, an added advantage is that the
separation and purification of all of the intermediates were
made easier with the introduction of this polar acetylene-
We have become interested in integrating the concept of
photochromic systems and p-conjugated polymers to pro-
duce new organic semi-conductive polymers that may po-
tentially
exhibit
photoswitchable
optoelectronic
properties. As evident from the literature on photochromic
polymeric systems, the majority reported so far have pho-
tochromic units appended as side chains on a few class of
readily accessible polymers such as poly(methyl meth-
acrylates) (PMMA) and polystyrenes (PS).5 There have
been a few recent reports of photochromic backbone con-
jugated polymers as well.6 In these works, the photo-
chromes used were based on the 1,2-dithienylethene or
related systems, by taking advantage of the facile photo-
SYNTHESIS 2006, No. 18, pp 3075–3079
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x.
x
x
.
2
0
0
6
Advanced online publication: 02.08.2006
DOI: 10.1055/s-2006-942529; Art ID: M01906SS
© Georg Thieme Verlag Stuttgart · New York

3076
J. Yang, M.-K. Ng
PAPER
masking group. Furthermore, we have extended the appli- 62% yield (Scheme 3). The polymerization of 8 with 1,4-
cation of this protecting group by converting the hydroxyl diiodobenzene was catalyzed by Pd(PPh3)2Cl2 and CuI in
functionality to the corresponding tetrahydropyranyl a mixture of toluene and triethylamine (Scheme 4). The
(THP) ether as well. For example, tetrahydro-2-(2-propy- polymerization was allowed to run at room temperature
nyloxy)-2H-pyran was used as the staring material to for 48 hours before it was quenched with a saturated aque-
achieve the preparation of compound 2 carrying two dif- ous ammonium chloride solution. The crude polymer was
ferently masked acetylene functionalities. When treated purified by repeated precipitation of a concentrated
with mild acid (p-TsOH), the THP linkage in compound 4 dichloromethane solution of the polymer from methanol.
was readily removed and the corresponding hydroxy- The purified polymer was determined to have a molecular
methyl moiety was easily regenerated (Scheme 1).
weight (Mw) of 24,272 by gel permeation chromatography
(GPC) analysis, with a polydispersity index (PDI) of 1.23.
A selective mono-cross coupling reaction of 1,4-bis(do-
decyloxy)-2,5-diiodobenzene (> two-fold excess) with Figure 1 shows the UV-Vis absorption spectra of the
tetrahydro-2-(2-propynyloxy)-2H-pyran under typical polymer 9 (0.01 mg/mL) in chloroform. Upon irradiation
Sonogashira conditions provided monoiodo acetylene 1 in with UV light of 365 nm, a new absorption band appeared
reasonable yield (61%). This compound was further sub- above 500 nm due to the formation of the merocyanine
jected to another cross-coupling with excess propargyl al- form which bridges the conjugated systems between two
cohol to give bis(acetylene) 2 having different protecting adjacent ethynylphenyl moieties (Scheme 5). In addition,
groups on the two acetylene moieties. The hydroxymeth- the absorption bands at 397 nm and 315 nm in the closed-
ylethynyl masking group was then removed by stirring a ring PPE polymer were slightly blue-shifted to 388 nm
solution of compound 2 with a mixture of powdered man- and 309 nm, respectively, as a result of the ring-opening
ganese dioxide and potassium hydroxide in diethyl ether isomerization reaction. Overall the signal changes appear
at room temperature to yield terminal acetylene 3. Com- to be relatively small which may point to the fact that rel-
pound 4 was then obtained upon further treatment of 3 atively few spirobenzopyran units undergo ring-opening
with catalytic amounts of p-toluenesulfonic acid (PTSA) isomerization upon irradiation. The general difficulty en-
in dichloromethane and methanol (2:1). 7-Iodo-6-nitro-5¢- countered in the isolation of unstable merocyanine form
iodospirobenzopyran 6 was readily available from the of the polymer has also precluded the determination of the
condensation of commercially available 1,3,3-trimethyl- extinction coefficient of the appropriate functionality that
2-methyleneindoline with 4-iodo-5-nitrosalicylaldehyde,9 could quantify the degree of ring opening in the present
followed by iodination with benzyltriethylammonium system. In summary, a new photochromic polymer with
dichloroiodate (BnEt3NICl2) as shown in Scheme 2.10
spirobenzopyran units incorporated in the PPE backbone
was synthesized. Future studies will focus on optimization
of the photochromic properties by fine-tuning the elec-
tronic and optical properties of the substituent on the con-
jugated system.
A two-fold cross-coupling reaction of diiodide 6 with
acetylene alcohol 4 afforded 7 in 59% yield. Removal of
the hydroxymethyl moiety by manganese dioxide and po-
tassium hydroxide afforded bis(acetylenic) monomer 8 in
OC12H25
OC12H25
I
OC12H25
HO
ii
i
I
I
O
O
2
1
C12H25O
O
C12H25
O
C12H25O
O
iii
OC12H25
OC12H25
iv
H
H
OH
O
4
C12H25O
C12H25O
O
3
Scheme 1 Synthesis of terminal acetylene 4. Reagents and conditions: (i) Tetrahydro-2-(2-propynyloxy)-2H-pyran, Pd(PPh3)2Cl2, CuI, Et3N;
(ii) propargyl alcohol, Pd(PPh3)2Cl2, CuI, Et3N; (iii) MnO2, powdered KOH, Et2O, r.t.; (iv) PTSA, CH2Cl2, MeOH, r.t.
OH
I
CHO
i
ii
+
N
N
N
O
NO2
O
NO2
I
NO2
I
I
5
6
Scheme 2 Synthesis of diiodospirobenzopyran 6. Reagents and conditions: (i) EtOH, reflux; (ii) BnEt3NICl2, CaCO3, CH2Cl2, MeOH.
Synthesis 2006, No. 18, 3075–3079 © Thieme Stuttgart · New York

PAPER
A Photochromic Conjugated Polymer with Spirobenzopyran in the Backbone
3077
HOH2C
H
OC12H25
OC12H25
C12H25O
C12H25O
ii
i
N
O
NO2
6
N
O
NO2
OC12H25
OC12H25
7
8
C12H25O
C12H25O
CH2OH
H
Scheme 3 Synthesis of bis(acetylene) monomer 8. Reagents and conditions: (i) 4, Pd(PPh3)2Cl2, CuI, Et3N, toluene; (ii) MnO2, KOH, Et2O,
r.t.
NO2
OC12H25
OC12H25
O
i
N
I
I
8 +
C12H25O
Polymer 9
OC12H25
n
Scheme 4 Synthesis of polymer 9 by palladium-catalyzed polymerization of monomer 8 with 1,4-diiodobenzene. Reagents and conditions:
(i) Pd(PPh3)2Cl2, CuI, Et3N, toluene.
0.17 mmol) in toluene (100 mL) and Et3N (30 mL), was added drop-
All reagents and solvents were obtained from commercial suppliers
unless otherwise noted. All cross-coupling reactions and other air-
sensitive reactions were performed under a nitrogen (or argon) at-
mosphere. 1H NMR spectra were recorded on a Bruker Avance-400
NMR spectrometer at 400 MHz. 13C NMR spectra were recorded on
a Bruker Avance-500 NMR spectrometer at 100 MHz. HRMS data
were obtained at the Washington University Mass Spectrometry
Resource using the ESI technique.
wise a solution of tetrahydro-2-(2-propynyloxy)-2H-pyran (2.40 g,
17.12 mmol) in toluene (10 mL) over a period of 1 h at r.t. under a
nitrogen atmosphere. The reaction mixture was stirred for an addi-
tional hour and then poured into H2O and extracted with Et2O. The
aqueous layer was further extracted with Et2O. The combined or-
ganic extracts were washed with H2O, brine and dried over anhyd
Na2SO4. The solvent was evaporated on a rotary evaporator under
reduced pressure and the solid residue was chromatographed on a
silica gel column (hexane–CH2Cl2, 5:1 → 1:2) to afford 1 (yield:
7.45 g, 10.48 mmol, 61%) as a white solid; mp 34–35 °C.
Compound 1
To a solution of 1,4-bis(dodecyloxy)-2,5-diiodobenzene (29.0 g,
41.5 mmol), Pd(PPh3)2Cl2 (60 mg, 0.085 mmol) and CuI (32.6 mg,
NO2
OC12H25
OC12H25
O
N
C12H25O
visible light
N
365 nm
OC12H25
n
O
C12H25O
OC12H25
OC12H25
NO2
OC12H25
n
Scheme 5 Linear spirobenzopyran-functionalized p-conjugated polymer with segmented conjugation (SP form) and fully extended conjuga-
tion (MC form) in different photoisomerizable states.
Synthesis 2006, No. 18, 3075–3079 © Thieme Stuttgart · New York

3078
J. Yang, M.-K. Ng
PAPER
desired product as a white solid (yield: 0.40 g, 0.76 mmol, 92%); mp
68–69 °C.
1H NMR (400 MHz, CDCl3): d = 6.94 (s, 1 H), 6.91 (s, 1 H), 4.53
(s, 2 H), 3.95 (m, 4 H), 3.32 (s, 1 H), 1.79 (m, 4 H), 1.45 (m, 4 H),
1.26–1.36 (m, 33 H), 0.88 (t, J = 6.8 Hz, 6 H).
13C NMR (100 MHz, CDCl3): d = 154.0, 153.3, 117.8, 117.2, 113.7,
112.8, 92.6, 82.3, 81.8, 79.8, 69.7, 69.6, 51.8, 31.9, 29.7, 29.6, 29.6,
29.3, 29.1, 25.9, 25.9, 22.7, 14.1.
HRMS (ESI): m/z [M + Na]+ calcd for C35H56O3: 548.4161; found:
548.4156.
Compound 5
To a suspension 2-hydroxy-4-iodo-5-nitrobenzaldehyde (1.50 g,
5.12 mmol) in EtOH (30 mL) was added a solution of 1,3,3-tri-
methyl-2-methyleneindoline (887 mg, 5.12 mmol) in EtOH (30
mL). The resulting mixture was heated to 65 °C for 3 h. Excess sol-
vent was removed in vacuo and the solid residue was chromato-
graphed on a silica gel column (hexane–CH2Cl2, 3:1 → 2:1) to
afford the desired product as a yellow solid (yield: 0.80 g, 1.785
mmol, 34%); mp 150 °C (dec.).
Figure 1 UV–Vis absorption spectra of polymer 9 upon irradiation
with UV light at 365 nm (arrow indicates changes in spectral response
upon initial UV irradiation).
1H NMR (400 MHz, CDCl3): d = 7.82 (s, 1 H), 7.40 (s, 1 H), 7.21
(t, J = 7.7 Hz, 1 H), 7.09 (d, J = 7.2 Hz, 1 H), 6.87–6.91 (m, 2 H),
6.56 (d, J = 7.7 Hz, 1 H), 5.89 (d, J = 10.3 Hz, 1 H), 2.74 (s, 3 H),
1.30 (s, 3 H), 1.18 (s, 3 H).
1H NMR (400 MHz, CDCl3): d = 7.25 (s, 1 H), 6.83 (s, 1 H), 4.93
(t, J = 3.3 Hz, 1 H), 4.45–4.55 (m, 2 H), 3.90–3.95 (m, 4 H), 3.85–
3.89 (m, 1 H), 3.53–3.58 (m, 1 H), 1.26–1.88 (m, 46 H), 0.88 (t, J =
6.8 Hz, 6 H).
HRMS (ESI): m/z [M + Na]+ calcd for C38H63O4I: 733.3669; found:
733.3646.
Compound 6
Compound 5 (800 mg, 1.785 mmol) was dissolved in CH2Cl2 and to
the solution were added successively BnEt3NICl2 (1000 mg, 2.56
mmol) and CaCO3 (367 mg, 3.67 mmol). The resulting mixture was
stirred at r.t. for 24 h. Excess CaCO3 was removed by filtration and
the filtrate was poured into H2O and washed with aq sodium
bisulfite, H2O, and brine, then dried over anhyd Na2SO4. Excess sol-
vent was removed in vacuo and the solid was purified by column
chromatography (silica gel; hexane–EtOAc, 4:1 → 3:1) to afford
the desired product as a yellow solid (yield: 0.65 g, 1.13 mmol,
63%); mp 175 °C (dec.).
1H NMR (400 MHz, CDCl3): d = 7.81 (s, 1 H), 7.48 (dd, J = 1.7, 8.2
Hz, 1 H), 7.40 (s, 1 H), 7.32 (d, J = 1.7 Hz, 1 H), 6.89 (d, J = 10.3
Hz, 1 H), 6.34 (d, J = 8.2 Hz, 1 H), 5.85 (d, J = 10.3 Hz, 1 H), 2.70
(s, 3 H), 1.26 (s, 3 H), 1.17 (s, 3 H).
Compound 2
The synthetic procedure of 2 is similar to that of 1; yield: 85%; mp
61 °C.
1H NMR (400 MHz, CDCl3): d = 6.90 (s, 1 H), 6.89 (s, 1 H), 4.94
(t, J = 3.3 Hz, 1 H), 4.57 (s, 2 H), 4.47 (s, 2 H), 3.91–3.96 (m, 4 H),
3.85–3.88 (m, 1 H), 3.54–3.57 (m, 1 H), 1.74–1.89 (m, 7 H), 1.54–
1.68 (m, 4 H), 1.41–1.47 (m, 4 H), 1.26–1.30 (m, 32 H), 0.88 (t, J =
6.8 Hz, 6 H).
HRMS (ESI): m/z [M + Na]+ calcd for C41H66O5: 661.4808; found:
661.4797.
HRMS (ESI): m/z [M + H]+ calcd for C19H16N2O3I2: 574.9329;
found: 574.9332.
Compound 3
To a solution of 2 (1.15 g, 1.80 mmol) in Et2O (20 mL) was added
KOH powder (1.01 g, 18.0 mmol) and MnO2 (3.13 g, 36.0 mmol).
The mixture was stirred at r.t. for 2 h and then filtered through a
short pad of silica gel, eluted with Et2O to afford 3 (yield: 1.06 g,
1.74 mmol, 97%) as a light yellow solid; mp 53–54 °C.
1H NMR (400 MHz, CDCl3): d = 6.93 (s, 1 H), 6.91 (s, 1 H), 4.94
(t, J = 3.1 Hz, 1 H), 4.48–4.56 (m, 2 H), 3.92–3.97 (m, 4 H), 3.86–
3.91 (m, 1 H), 3.55–3.57 (m, 1 H), 3.31 (s, 1 H), 1.26–1.87 (m, 46
H), 0.88 (t, J = 6.8 Hz, 6 H).
Compound 7
A mixture of compound 6 (50 mg, 0.087 mmol), 4 (114 mg, 0.217
mmol), Pd(PPh3)2Cl2 (2.4 mg, 0.0034 mmol) and CuI (0.7 mg,
0.00348 mmol) in toluene (3 mL) and Et3N (2 mL) were stirred at
r.t. for 30 min and then heat to 50 °C overnight. The mixture was
poured into sat. aq NH4Cl solution. The organic layer was washed
with H2O, brine and dried over anhyd Na2SO4. Excess solvent was
removed in vacuo and the residue was chromatographed on a silica
gel column (hexane–EtOAc, 4:1 → 3:1) to afford the desired prod-
uct as a thick brown oil (yield: 70 mg, 0.0511 mmol, 59%).
HRMS (ESI): m/z [M + Na]+ calcd for C40H64O4: 632.4736; found:
632.4734.
1H NMR (400 MHz, CDCl3): d = 7.95 (s, 1 H), 7.39 (d, J = 7.9 Hz,
1 H), 7.23 (s, 1 H), 6.96–6.98 (m, 3 H), 6.90–6.93 (m, 3 H), 6.49 (d,
J = 8.1 Hz, 1 H), 5.85 (d, J = 10.3 Hz, 1 H), 4.52 (s, 2 H), 4.51 (s, 2
H), 3.93–3.99 (m, 8 H), 2.75 (s, 3 H), 1.74–1.86 (m, 8 H), 1.39–1.62
(m, 8 H), 1.18–1.34 (m, 72 H), 0.82–0.87 (m, 12 H).
13C NMR (100 MHz, CDCl3): d = 157.4, 154.0, 153.5, 153.4, 153.2,
147.7, 141.8, 136.2, 132.1, 128.0, 124.9, 124.0, 121.7, 121.0, 120.3,
118.4, 117.4, 117.3, 117.2, 116.6, 115.0, 114.3, 114.1, 113.2, 112.3,
106.8, 105.9, 96.1, 94.5, 93.1, 92.3, 90.6, 83.9, 82.1, 81.9, 69.6,
69.5, 52.1, 51.8, 51.7, 31.9, 29.6, 29.5, 29.3, 29.2, 29.1, 29.1, 29.0,
28.7, 26.0, 25.9, 25.8, 25.8, 22.6, 19.9, 14.1.
Compound 4
A solution of 3 (0.50 g, 0.82 mmol) and p-toluenesulfonic (PTSA)
monohydrate (31.2 mg, 0.164 mmol) in CH2Cl2 (10 mL) and MeOH
(5 mL) was stirred at r.t. until all of the starting material was con-
sumed as monitored by TLC analysis. The resulting solution was
poured into sat. aq NaHCO3 solution. The organic layer was sepa-
rated and the aqueous layer was further extracted with CH2Cl2. The
combined organic layers were washed with H2O, brine and dried
over anhyd Na2SO4. The solvent was removed in vacuo to afford the
Synthesis 2006, No. 18, 3075–3079 © Thieme Stuttgart · New York

PAPER
A Photochromic Conjugated Polymer with Spirobenzopyran in the Backbone
3079
Compound 8
(2) Photochromism: Molecules and Systems; Dürr, H.; Bouas-
Laurent, H., Eds.; Elsevier: Amsterdam, 1990.
(3) (a) Sakata, T.; Yan, Y.; Marriot, G. J. Org. Chem. 2005, 70,
2009. (b) Berkovic, G.; Krongauz, V.; Weiss, V. Chem. Rev.
2000, 100, 1741.
(4) (a) Reeves, D. A.; Wilkinson, F. J. Chem. Soc., Faraday
Trans. 2 1973, 69, 1381. (b) Heiligman-Rim, R.; Hirshberg,
Y.; Fischer, E. J. Phys. Chem. 1962, 66, 2465.
Compound 7 (300 mg, 0.22 mmol) was dissolved in Et2O (20 mL).
To the resulting solution were added KOH powder (129 mg, 2.30
mmol) and MnO2 (400 mg, 4.60 mmol). The mixture was stirred at
r.t. overnight and then passed through a short pad of silica gel, and
eluted with Et2O. Excess solvent was removed in vacuo to afford the
desired product (yield: 180 mg, 0.137 mmol, 62%) as a thick brown
oil.
(c) Heiligman-Rim, R.; Hirshberg, Y.; Fischer, E. J. Phys.
Chem. 1962, 66, 2470. (d) Kim, S.-H.; Choi, S.-W.; Suh, H.-
J.; Jin, S.-H.; Gal, Y.-S.; Koh, K. Dyes Pigm. 2002, 55, 17.
(e) Keum, S.-R.; Ku, B.-S.; Shin, J.-T.; Ko, J. J.; Buncel, E.
Tetrahedron 2005, 61, 6720.
1H NMR (400 MHz, CDCl3): d = 7.97 (s, 1 H), 7.41 (d, J = 8.0 Hz,
1 H), 7.24 (s, 1 H), 6.93–7.00 (m, 6 H), 6.51 (d, J = 8.1 Hz, 1 H),
5.87 (d, J = 10.3 Hz, 1 H), 3.97–4.02 (m, 8 H), 3.35 (s, 1 H), 3.33
(s, 1 H), 2.77 (s, 3 H), 1.77–1.87 (m, 8 H), 1.20–1.57 (m, 78 H),
0.85–0.89 (m, 12 H).
13C NMR (100 MHz, CDCl3): d = 157.5, 154.2, 154.0, 153.9, 151.1,
147.8, 141.9, 136.2, 132.2, 128.1, 125.0, 124.0, 121.8, 121.0, 120.4,
118.5, 117.8, 117.7, 117.2, 116.6, 115.4, 114.1, 113.8, 113.6, 111.8,
106.8, 105.9, 96.2, 94.5, 90.7, 83.9, 82.8, 82.0, 80.1, 79.9, 69.7,
69.6, 69.6, 52.1, 31.9, 29.7, 29.6, 29.6, 29.5, 29.3, 29.2, 29.2, 28.8,
26.1, 25.9, 25.9, 22.7, 19.9, 14.1.
(5) (a) Hirano, H.; Miyashita, A.; Nohira, H. Chem. Lett. 1991,
209. (b) Miyashita, A.; Hirano, H.; Nakono, S.; Nohira, H. J.
Mater. Chem. 1993, 3, 221. (c) Nakano, S.; Miyashita, A.;
Nohira, H. Chem. Lett. 1993, 501. (d) Deblauwe, V.; Smets,
G. J. Polym. Sci., Polym. Chem. 1989, 27, 671.
(6) (a) Marsella, M. J.; Wang, Z.-Q.; Mitchell, R. H. Org. Lett.
2000, 2, 2979. (b) Stellacci, F.; Bertarelli, C.; Toscano, F.;
Gallazzi, M. C.; Zotti, G.; Zebra, G. Adv. Mater. 1999, 11,
292. (c) Yassar, A.; Moustrou, C.; Youssoufi, H. K.; Samat,
A.; Guglielmetti, R.; Garnier, F. J. Chem. Soc., Chem.
Commun. 1995, 471. (d) Yassar, A.; Moustrou, C.;
Youssoufi, H. K.; Samat, A.; Guglielmetti, R.; Garnier, F.
Macromolecules 1995, 28, 4548. (e) Yassar, A.; Rebière-
Galy, N.; Frigoli, M.; Moustrou, C.; Samat, A.;
HRMS (ESI): m/z [M + H]+ calcd for C87H122N2O7: 1307.9330;
found: 1307.9271.
Polymer 9
Compound 8 (143 mg, 0.109 mmol) and 1,4-diiodobenzene (36 mg,
0.109 mmol) were dissolved in toluene (2 mL) and Et3N (1 mL). To
the solution were added Pd(PPh3)2Cl2 (3 mg, 0.004 mmol) and CuI
(0.8 mg, 0.004 mmol). The reaction mixture was stirred at r.t. for 48
h under a nitrogen atmosphere. The solution was poured into sat.
NH4Cl solution and the organic layer was separated. The aqueous
layer was further extracted with Et2O. The combined organic layer
was washed with H2O, brine and dried over anhyd Na2SO4. The so-
lution was concentrated to a small volume and MeOH was added
slowly to precipitate the polymer.
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Acknowledgment
We gratefully acknowledge the University of Rochester and ACS
(PRF Type G) for support of this research. We also wish to thank
Mr. Yong Zhang and Prof. Mitchell Anthamatten for help with GPC
measurements. Mass spectrometry was provided by the Washington
University Mass Spectrometry Resource with support from the NIH
National Center for Research Resources (Grant No. P41RR0954).
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Synthesis 2006, No. 18, 3075–3079 © Thieme Stuttgart · New York