Efficient and rapid synthesis of oligo(p-phenylenevinylene) via iterative coherent approach

Article abstract of DOI:10.1021/jo026907s

A general and controlled bidirectional growth strategy enables a very rapid and efficient construction of OPV compounds possessing functional groups such as aldehyde and mercapto groups at both ends. The strategy employs only one reaction type with high y

Full text of DOI:10.1021/jo026907s

Efficien t a n d Ra p id Syn th esis of Oligo(p-p h en ylen evin ylen e) via
Iter a tive Coh er en t Ap p r oa ch
Cuihua Xue†,‡ and Fen-Tair Luo*,†
Institute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan 11529, and The Faculty of Chemistry,
Sichuan University, Chengdu 610064, China
luoft@chem.sinica.edu.tw
Received December 24, 2002
A general and controlled bidirectional growth strategy enables a very rapid and efficient construction
of OPV compounds possessing functional groups such as aldehyde and mercapto groups at both
ends. The strategy employs only one reaction type with high yields and stereoselectivities to grow
the conjugated chains, eliminating the need for protecting groups in the overall intermediates.
Recently, poly-para-phenylenevinylene (PPV) and oligo-
para-phenylene-vinylene (OPV) derivatives that possess
long conjugated systems have drawn much attention in
materials science due to their electrooptic properties.1
Thus, various applications in light-emitting diodes, in
semiconductive or photoconductive devices, in nonlinear
optics, conversion of sunlight, etc., have been reported.2
In particular, PPV has been used as an emissive material
for use in electroluminescent devices. In addition, OPV
molecules possessing well-defined conjugation lengths
and structures may also serve as model systems for
understanding the relationships between bulk material
properties and molecular structures in conducting poly-
mers. Though it is well-documented that bulk conjugated
organic materials can be semiconducting or even con-
ducting when doped, the synthesis of mercapto-ended
linear conjugated molecules that orient themselves on
gold surfaces is still limited. Herein, we describe a rapid
synthetic route for the formation of soluble oligo(2,5-
dihexyloxy-1,4-phenylenevinylene)s, potential molecular
nanoscale wires, by a rapid iterative coherent approach.
These mercapto-ends can serve as molecular-scale al-
ligator clips for adhesion of the molecular scale wires to
the gold probes. Recently, there has been considerable
effort to prepare large conjugated molecules of precise
length and constitution.1h,3,4 Our approach to these
compounds maintains several key features that make it
well-suited for the requisite large molecular architectures
for molecular-scale electronics studies. Specifically, the
route involves (1) a rapid construction method that
permits large prolongation of molecular length at each
coupling stage to afford an unbranched oligomer, (2)
using only one key molecular building block to make the
desired linear molecular wires, (3) very simple and
efficient separation and purification by recrystallization
at each step, (4) an iterative coherent approach so that
the same high-yielding reaction can be used throughout
the sequence, (5) products that are stable to light and
air so that subsequent engineering manipulations will
not be impeded, (6) products that could easily permit
independent functionalization of the ends to mercapto
groups to serve as molecular alligator clips that are
required for surface contacts to metal probes, and (7)
products that serve as useful models for the understand-
ing of bulk polymeric materials.
† Academia Sinica.
‡ Sichuan University.
(1) (a) Greenham, N. C.; Moratti, S. C.; Bradley, D. D. C.; Friend,
R. H.; Holems, A. B. Nature 1993, 365, 628. (b) Katz, H. E.; Bent, S.
F.; Wilson, W. L.; Schilling, M. L.; Ungashe, S. B. J . Am. Chem. Soc.
1994, 116, 6631. (c) Segura, J . L.; Martin, N. J . Mater. Chem. 2000,
10, 2403. (d) Martin, R. E.; Diederich, F. Angew. Chem., Int. Ed. 1999,
38, 1350. (e) Scherf, U. Top. Curr. Chem. 1999, 201, 163-222. (f)
Mu¨llen, K.; Wegner, G. Electronic Materials: The Oligomer Approach;
Wiley-VCH: Weinheim, Germany, 1998. (g) Kraft, A.; Grimsdale, A.
C.; Holmes, A. B. Angew. Chem., Int. Ed. 1998, 37, 403. (h) Tour, J .
M. Chem. Rev. 1996, 96, 537. (i) Salaneck, W. R.; Lundstro¨m, I.; Ranby,
B. Conjugated Polymers and Related Materials; Oxford University
Press: Oxford, 1993. (j) Mu¨llen, K. Pure Appl. Chem. 1993, 65, 89.
(2) (a) Mullner, R.; Winkler, B.; Stelzer, F.; Tasch, S.; Hochfilzer,
C.; Leising, G. Synth. Met. 1999, 105, 129. (b) Thorn-Csa´nyi, E.;
Kraxner, P.; Hammer, J . J . Mol. Catal. A: Chem. 1994, 90, 15. (c)
Thorn-Csa´nyi, E.; Ho¨hnk, H.-D.; Pflug, K. P. J . Mol. Catal. A: Chem.
1993, 84, 253. (d) Thorn-Csa´nyi, E.; Kraxner, P. Macromol. Chem.
Phys. 1997, 198, 3827. (e) Thorn-Csa´nyi, E.; Pflug, K. P. Makromol.
Chem. 1993, 194, 2287. (f) Schlick, H.; Stelzer, F.; Tasch, S.; Leising,
G. J . Mol. Catal. A: Chem. 2000, 160, 71.
Our initial synthetic results showed that the stepwise
synthesis of oligo(p-phenylenevinylene) larger than decam-
ers via Heck-type reaction of aryl bromide or iodide with
a styryl vinyl group (e.g., 1 and 2) could provide only low
yields and other unidentified byproducts by using various
palladium catalysts. We then turned our attention to the
iterative coherent approach as shown in Scheme 1.
(3) Maddux, T.; Li, W.; Yu, L. J . Am. Chem. Soc. 1997, 119, 844.
(4) Meier, H.; Ickenroth, D. Eur. J . Org. Chem. 2002, 1745.
10.1021/jo026907s CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/03/2003
J . Org. Chem. 2003, 68, 4417-4421
4417

Xue and Luo
SCHEME 1
F IGURE 1. Absorption and emission spectra of compounds
9-11 in a dilute solution of dichloromethane.
is itself derived from monoprotection as cyclic ethylene
acetal in 70% yield of 2,5-dihexyloxybenzene-1,4-dicar-
baldehyde9 in one simple step. Thus, under the Horner-
Wadsworth-Emmons reaction conditions, 12 and 13
could afford 3 and 14 in a ratio of 2:3 in 98% total yield.
Compounds 3 and 14 can be separated and purified by
column chromatography (silica gel, hexane/EtOAc ) 25:1
and CH2Cl2:EtOAc ) 10:1). Acidic hydrolysis of 14 could
afford 4 in quantitative yield (Scheme 3). The trans
stereochemistry of the styryl double bonds in 3 and 4 was
The key to the overall strategy is the synthesis of the
building block molecule, monomer 3, which possesses a
dimethylphosphonate ester group at one end and a cyclic
acetal functional group at the other end. Monomer 4
possesses a dialdehyde group at both ends. The phos-
phonate terminus of 2 equiv of monomer 3 can couple
with both aldehyde termini of monomer 4 under the
Horner-Wadsworth-Emmons reaction conditions and
give oligomer 5 in 95% yield after hydrolysis of the cyclic
acetal group under acidic conditions. Similar condensa-
tion of oligomer 5 with monomer 3 under the Horner-
Wadsworth-Emmons reaction conditions and followed
by the sequential hydrolysis under acidic conditions could
afford oligomer 6 in 94% yield. Iterative condensation of
oligomer 6 with monomer 3 and followed by acidic
hydrolysis could successfully afford oligomer 7 in 96%
yield. Therefore, the growth of the OPV chain commences
with compound 4 and thereafter monomer 3 is added in
a repetitive stepwise fashion. The process could be
repeated to quickly build up longer OPV molecules
possessing aldehyde groups as the functionalized termini.
Oligomers 5-7 with two aldehyde groups at the termini
can further undergo Horner-Wadsworth-Emmons reac-
tion with 8, the molecule with methyl sulfide at the one
end and the dimethylphosphonate ester group at the
other end, to form 9-11 in 96, 94, and 93% yields,
respectively (Scheme 2). The transformation of the
terminal methyl sulfide groups on 9 to the two terminal
mercapto groups in good yield (>90% yield) can be done
by treating 9 with 5 equiv of sodium 2-methyl-2-pro-
panethiolate in very dry DMF.5
1
confirmed by their H NMR spectral analysis.
Interestingly, under the Horner-Wadsworth-Em-
mons reaction conditions, no cis isomers of 3 and 4 were
detected. The solubility of 5-7 and 9-11 in CHCl3 and
CH2Cl2 is noteworthy. When we attempted to prepare the
analogues of these oligomers with 2,5-dimethyoxyl or 2,5-
dihexyloxyl groups at alternative positions of the benzene
rings without attaching the 2,5-dihexyloxyl groups, only
the analogue of 6 with 2,5-dimethyoxyl groups and the
analogue of 5 with 2,5-dihexyloxyl groups at the alterna-
tive positions of the benzene rings were obtained in good
yields but with very low solubilities in various organic
solvents. In contrast, oligomers 5-7 and 9-11 without
the 2,5-alkoxyl groups at the alternative positions of the
benzene rings can easily dissolve in chloroform. Yields
for each of the Horner-Wadsworth-Emmons reaction
steps to prepare oligomers 5-7 and 9-11 were good
without the influence from the longer length of the
oligomers. Thus, oligomers 9-11 can be obtained in 91,
88, and 89% isolated yields, respectively, starting from
monomers 3 and 4. Presently, we have succeeded in the
synthesis and purification of compound 11, which pos-
sesses 17 aryl rings and 16 styryl double bonds in its
conjugation pathway, and a molecular weight of 3404.
Synthesis of longer oligomers is still in progress. All of
the spectroscopic studies and high-resolution mass spec-
tral results are consistent with the proposed molecular
structures. The synthesis of other smaller building blocks
in good to moderate yields via the conventional pathway
is shown in Schemes 4 and 5.
Both monomers 3 and 4 are conveniently prepared in
a highly stereoselective manner from 126-8 and 13, which
The absorption and emission spectra for the series of
OPVs 9-11 that possess two methyl sulfide end groups
are shown in Figure 1. All of the oligomers show strong
(5) Pinchart, A.; Dallaire, C.; Bierbeek, A. V.; Gingras, M. Tetrahe-
dron Lett. 1999, 40, 5479.
(6) Griffin, C. E.; Gordon, M. J . Am. Chem. Soc. 1967, 89, 4427.
(7) Eldo, J .; Arunkumar, E.; Ajayaghosh, A. Tetrahedron Lett. 2000,
41, 6241.
(8) Pillow, J . N. G.; Halim, M.; Lupton, J . M.; Burn, P. L.; Samuel,
I. D. W. Macromolecules 1999, 32, 5985.
(9) Sarker, A. M.; Ding, L.; Lahti, P. M.; Karasz, F. E. Macromol-
ecules 2002, 35, 223.
4418 J . Org. Chem., Vol. 68, No. 11, 2003

Synthesis of Oligo(p-phenylenevinylene)
SCHEME 2
SCHEME 3
SCHEME 4
cence. There is a major band with a shoulder to the red
of moderate intensity in the emission spectrum of oligo-
mers 9-11. The fluorescence quantum yields of the
oligomers 9 to 11 in dichloromethane are 36, 37, and 33%,
respectively.
It should be pointed out that various syntheses of
different OPVs have been reported in the past.3,4,11-12
Schenk et al. have investigated the charging capacity of
OPV molecules and the charge distribution within the
OPV chain.11 Katz et al. have studied the fluorescence
dynamics of OPVs both in solution and the solid state
and observed little difference between them.12 Yu et al.
has presented an orthogonal approach to stepwise syn-
thesis of long oligomers with 12 rings and 11 double
bonds.3 Meier et al. has reported the synthesis of OPV
oligomers with 16 rings and 15 double bonds in low yield
via a multistep synthesis on the basis of hydroquinone.4
In this paper, we use an iterative coherent approach to
effectively and rapidly synthesize longer oligomers with
17 rings and 16 double bonds. Due to the fact that the
Horner-Wadsworth-Emmons reaction can tolerate a
wide variety of functional groups, it should be possible
to synthesize many different OPV molecules of various
lengths and structures. This is useful for fine-tuning the
band gap in emissive organic materials that will more
closely resemble organic polymeric conducting materials.
Also noteworthy is the use of only one reaction type to
construct the requisite functionality; this eliminates the
need of repetitive protection steps in the overall inter-
mediates. The use of a stilbene analogue as the building
block allows for efficient and fast construction of the OPV
chain. After each step, two aldehyde functional groups
are left for further chemical manipulation, which may
include either continued elongation or reaction with an
SCHEME 5
and broad absorption in the visible region. Elongation of
the conjugation length from 9 to 11 results in a red shift
of 4 nm in the emission spectra but a red shift of 6 nm
from 9 to 10 and the same λmax for 10 and 11 in the
absorption spectra. The small red shift and blue shift in
the absorption spectra of oligomers 9 to 11 are notewor-
thy. They indicate that the limitations to electron delo-
calization in the longer oligomers have been reached.10
Thus, the effective conjugation length in this series of
oligomers is reached at oligomer 10. The absorption
wavelength maximum in the oligomers converges to that
of PPV over relatively short conjugation lengths, which
suggests the validity of using OPV to better understand
the electronic properties of electroactive PPV materials.
The extinction coefficients for compounds 9-11 are 1.71
× 105, 2.40 × 105, and 3.20 × 105, respectively. This
indicates that increasing the conjugation length of OPV
may also increase the transition probability of electrons
from their ground states to the excited states. Solutions
of these oligomers 9-11 give a brilliant green fluores-
(11) Schenk, R.; Gregorious, H.; Meerholz, K.; Heinze, J .; Mullen,
K. J . Am. Chem. Soc. 1991, 113, 2634.
(10) Graham, S. C.; Bradley, D. D. C.; Friend, R. H.; Spangler, C.
Synth. Met. 1991, 41.
(12) Katz, H. Z.; Bent, S. F.; Wilson, W. Z.; Schilling, M. L.; Ungashe,
S. B. J . Am. Chem. Soc. 1994, 116, 6631.
J . Org. Chem, Vol. 68, No. 11, 2003 4419

Xue and Luo
washed with 15% NaHCO3 (3 × 30 mL) and brine (3 × 30 mL),
and dried over MgSO4. The solvent was evaporated, and the
residue was recrystallized from hexane/EtOAc to provide pure
compound 4 as a yellow solid (0.56 g, 57% yield).
end-functionalized polymer to form novel diblock copoly-
mers or with an end-capped monomer to form longer
oligomers.
In summary, our general and controlled bidirectional
growth strategy enables a very rapid and efficient
construction of OPV compounds possessing functional
groups at both ends. The strategy employs only one
reaction type to grow the conjugated chains, eliminating
the need for a protecting group in the overall intermedi-
ates. We intend to use these molecules in the production
of novel molecular wires.
Com p ou n d 3. 1H NMR (CDCl3, TMS): δ 0.92 (t, J ) 7 Hz,
6 H), 1.34-1.37 (m, 8 H), 1.45-1.50 (m, 4 H), 1.79-1.85 (m, 4
H), 3.18 (d, J ) 20 Hz, 2 H), 3.68 (d, J ) 10 Hz, 6 H), 3.98-
4.16 (m, 8 H), 6.13 (s, 1 H), 7.08 (d, J ) 16 Hz, 1 H), 7.09 (s,
1 H), 7.10 (s, 1 H), 7.28 (dd, J ) 2.4, 8.1 Hz, 2 H), 7.45 (d, J )
16 Hz, 1 H), 7.46 (s, 1 H), 7.49 (s, 1 H) ppm. 13C NMR (CDCl3,
TMS): δ 14.11, 22.72, 25.84, 26.01, 29.45, 29.52, 31.69, 32.15,
33.52, 52.99, 53.06, 65.35, 65.38, 69.57, 69.64, 99.27, 110.65,
111.65, 123.77, 123.79, 126.38, 126.89, 126.92, 128.10, 128.84,
128.87, 130.04, 130.11, 130.40, 130.50, 136.80, 150.95, 151.65
ppm. IR (CH2Cl2) υmax: 2848, 1604, 1512, 1450, 1036 cm-1
.
Exp er im en ta l Section
MS m/z: 574 (M+). HRMS: calcd for C32H47O7P, 574.3059;
Solvents were dried by appropriate methods wherever
needed. All organic extracts were dried over anhydrous
magnesium sulfate. TLC was done on aluminum sheets with
precoated silica gel 60 F254 (40 × 80 mm). Purification by
column chromatography was carried out with neutral silica
gel 60 (70-230 mesh ASTM). The purity of each compound
was judged to be >95% by 1H NMR or 13C NMR spectral
analyses. Melting points were taken on a capillary tube
apparatus and are uncorrected. IR spectra were recorded as
either Nujol mulls or in the solution form as denoted. 1H NMR
and 13C NMR spectra were recorded in CDCl3 solution on
either a 300 or 400 MHz instrument using TMS (0 ppm) and
CDCl3 (77.0 ppm) as internal standards. HRMS spectra were
collected on an orthogonal acceleration-time-of-flight mass
spectrometer with a resolution of 6000 (5% valley definition)
and fitted with a magnet bypass flight tube. MALDI-MS
spectra were collected on a spectrometer equipped with a
nitrogen laser (337 nm) and operated in the delayed extraction
reflector mode. MS spectra were determined on a quadrupole
spectrometer or a GC/MS spectrometer. UV and fluorescent
spectra were recorded in CH2Cl2 solution.
4-(1,3-Dioxola n -2-yl)-2,5-d ih exyloxyben za ld eh yd e 13.
2,5-Bis-hexyloxy-1,4-dibenzaldehyde (7.4 g, 22 mmol), 1.3 equiv
of ethylene glycol, and a catalytic amount of p-toluenesulfonic
acid in 100 mL of toluene were stirred under reflux for 12 h.
After cooling to room temperature, the solution was washed
with water (3 × 50 mL) and dried over MgSO4, and the solvent
was removed in a vacuum. The crude product was then
purified by column chromatography (silica gel, hexene:EtOAc
) 25:1) to yield the desired acetal 13 as a yellow solid (5.9 g,
70% yield). Mp: 36-37 °C. 1H NMR (CDCl3, TMS): δ 0.88-
0.92 (m, 6 H), 1.23-1.28 (m, 8 H), 1.32-1.35 (m, 4 H), 1.74-
1.85 (m, 4 H), 3.98-4.18 (m, 8 H), 6.11 (s, 1 H), 7.19 (s, 1 H),
7.32 (s, 1 H), 10.47 (s, 1 H) ppm. 13C NMR (CDCl3, TMS): δ
13.98, 22.56, 25.63, 25.72, 29.07, 29.15, 31.49, 65.38, 69.21,
98.71, 110.14, 111.91, 125.50, 133.95, 151.24, 156.06, 189.52
ppm. IR (CH2Cl2) υmax: 2876, 2854, 1679, 1617, 1468, 1206,
1024 cm-1. MS m/z: 378 (M+). HRMS: calcd for C22H34O5,
378.2406; found, 378.2410.
found, 574.3054.
Com p ou n d 4. Mp: 130-131 °C. 1H NMR (CDCl3, TMS): δ
0.92 (t, J ) 6.8 Hz, 12 H), 1.38 (m, 16 H), 1.52-1.57 (m, 8 H),
1.83-1.88 (m, 8 H), 4.04 (t, J ) 6.4 Hz, 4 H), 4.12 (t, J ) 6.4
Hz, 4 H), 7.18 (s, 2 H), 7.22 (d, J ) 16 Hz, 2 H), 7.33 (s, 2 H),
7.48 (d, J ) 16 Hz, 2.H), 7.56 (s, 4 H), 10.45 (s, 2 H) ppm. 13C
NMR (CDCl3, TMS): δ 14.01, 22.61, 25.79, 25.86, 29.24, 31.57,
69.20, 69.32, 110.25, 110.62, 123.20, 124.40, 127.31, 131.71,
134.19, 137.22, 150.84, 156.24, 189.14 ppm. IR (CH2Cl2) υmax
:
2869, 2850, 1673, 1209, 1023 cm-1. MS m/z: 738 (M+).
HRMS: calcd for C48H66O6, 738.4859; found, 738.4841.
Gen er a l P r oced u r e for th e P r ep a r a tion of Oligom er s
5-7. NaH (0.2 g, 8.33 mmol) was added to a solution of
dialdehyde 4 (0.26 g, 0.35 mmol) and 3 (0.43 g, 0.75 mmol) in
dry THF (25 mL). The mixture was stirred at 50 °C for 5-12
h. After cooling to room temperature, the reaction mixture was
diluted with CHCl3 (50 mL) and washed with water (3 × 30
mL). The organic layer was separated and concentrated to give
the condensation product. This product was redissolved in
CHCl3 (30 mL), and 2 M HCl (20 mL) was gradually added;
the mixture was stirred at room temperature for 5-10 h. The
organic layer was separated, washed with 15% NaHCO3
solution (3 × 30 mL) and brine (3 × 30 mL), and dried over
MgSO4. The solvent was removed to give crude product, which
was washed with EtOAc and hexane to yield the pure product
5 in 95% yield.
Com p ou n d 5. Mp: 140-142 °C. 1H NMR (CDCl3, TMS): δ
0.93-0.97 (m, 24 H), 1.36-1.44 (m, 32 H), 1.53-1.57 (m, 16
H), 1.87-1.89 (m, 16 H), 4.03-4.11 (m, 16 H), 7.14-7.32 (m,
12 H), 7.47-7.54 (m, 20 H), 10.45 (s, 2H) ppm. 13C NMR
(CDCl3, TMS): δ 14.35, 22.93, 22.97, 26.09, 26.17, 26.29, 29.54,
29.81, 31.88, 31.97, 69.47, 69.58, 69.94, 110.48, 110.79, 110.86,
110.94, 122.89, 123.54, 124.13, 124.53, 127.18, 127.54, 128.50,
128.84, 132.23, 134.70, 136.66, 137.50, 138.36, 151.07, 151.47,
151.54, 156.55, 189.43 ppm. IR (CH2Cl2) υmax: 2870, 2848,
1674, 1210, 1025 cm-1. MS m/z: 1547 (M+). HRMS: calcd for
C
104H138O10, 1547.0290; found, 1547.0293.
Com p ou n d 6. Yield: 94%. Mp: 195-197 °C. 1H NMR
(CDCl3, TMS): δ 0.92-0.97 (m, 36 H), 1.36-1.42 (m, 48 H),
1.56-1.59 (m, 24 H), 1.85-1.91 (m, 24 H), 4.04-4.12 (m, 24
H), 7.13-7.33 (m, 20 H), 7.48-7.54 (m, 32 H), 10.45 (s, 2 H)
ppm. 13C NMR (CDCl3, TMS): δ 14.04, 22.57, 22.60, 22.65,
25.76, 25.84, 25.96, 29.20, 29.48, 31.53, 31.55, 31.64, 69.13,
69.22, 69.59, 110.12, 110.42, 110.53, 122.54, 123.21, 123.79,
124.17, 126.82, 127.22, 128.15, 128.39, 128.52, 131.90, 134.36,
P r ep a r a tion of Mon om er s ({4-[(1E)-2-(4-(1,3-Dioxola n -
2-y l)-2,5-d ih e x y lo x y -p h e n y l)v in y l]p h e n y l}m e t h y l)-
d im eth oxyp h osp h in o-1-on e 3 a n d 4-((1E)-2-{4-[(1E)-2-(4-
F or m yl-2,5-d ih exyloxyp h en yl)vin yl]p h en yl}vin yl)-2,5-
d ih exyloxyben za ld eh yd e 4. Compound 13 (1.0 g, 2.6 mmol)
and NaH (0.3 g, 12.5 mmol) were sequentially added to the
solution of compound 125-7 (2.0 g, 6.2 mmol) in 50 mL of dry
THF. The mixture was stirred at 40 °C for 4 h. After cooling
to room temperature, the mixture was diluted with EtOAc (50
mL), washed with brine (3 × 50 mL), and dried over MgSO4.
The solvent was evaporated, and the residue was purified by
column chromatography (silica gel), first employing hexene:
EtOAc ) 25:1 as the eluent to give intermediate compound
14 and then using CH2Cl2:EtOAc ) 10:1 to obtain compound
3 as a yellow oil (0.59 g, 39% yield).
137.16, 150.73, 151.14, 156.22, 189.13 ppm. IR (CH2Cl2) υmax
:
2867, 2846, 1667, 1208, 1023 cm-1. MS m/z: 2356 (M+).
HRMS: calcd for C160H210O14, 2355.5721; found, 2355.5652.
Com p ou n d 7. Yield: 96% yield. Mp: 206-208 °C. 1H NMR
(CDCl3, TMS): δ 0.94-0.98 (m, 48 H), 1.38-1.43 (m, 64 H),
1.58-1.61 (m, 32 H), 1.88-1.93 (m, 32 H), 4.04-4.15 (m, 32
H), 7.14-7.56 (m, 72 H), 10.46 (s, 2H) ppm. 13C NMR (CDCl3,
TMS): δ 14.03, 22.64, 25.75, 25.82, 25.94, 29.18, 29.45, 31.53,
31.62, 69.10, 69.19, 69.56, 110.08, 110.37, 110.48, 122.50,
123.17, 123.75, 124.12, 126.80, 127.21, 128.12, 128.37, 131.89,
HCl (2 M, 15 mL) was gradually added to the solution of
compound 14 in 20 mL of CHCl3. The mixture was stirred at
room temperature for 5 h. The organic layer was separated,
137.14, 150.69, 151.11, 156.20, 189.16 ppm. IR (CH2Cl2) υmax
:
4420 J . Org. Chem., Vol. 68, No. 11, 2003

Synthesis of Oligo(p-phenylenevinylene)
2865, 2844, 1667, 1206, 1024 cm-1. MS m/z: 3164 (M+).
HRMS: calcd for C216H282O18, 3164.1151; found, 3164.1139.
Dim et h yl (4-Met h ylt h iob en zyl)p h osp h on a t e 8. 4-
(Methylthio)benzyl alcohol (2.0 g, 13 mmol) and 48% hydro-
bromic acid (4 mL, 36 mmol) were stirred in 20 mL of toluene
at 90 °C for 1 h. The organic layer was separated, washed with
water (3 × 30 mL), and dried over MgSO4, and the solvent
was removed under reduced pressure to provide 4-methylth-
iobenzyl bromide as a white solid, which was then stirred with
P(OCH3)3 (8 mL, 69 mmol) at 120 °C for 10 h. Excess trimethyl
phosphite was distilled under vacuum to yield a faint brown
oil, which was purified by column chromatography (silica gel,
CH2Cl2:EtOAc ) 10:1) to give compound 8 as a colorless oil
(95% yield). 1H NMR (CDCl3, TMS): δ 2.47 (s, 3 H), 3.12 (d, J
) 20 Hz, 2 H), 3.67 (d, J ) 11 Hz, 6 H), 7.21 (s, 4 H) ppm. 13C
NMR (CDCl3, TMS): δ 15.81, 31.31, 33.15, 52.79, 52.88,
126.86, 127.83, 127.96, 130.01, 130.10, 137.16 ppm. IR (CH2-
Cl2) υmax: 2851, 1603, 1184, 1096, 969 cm-1. MS m/z: 246 (M+).
HRMS: calcd for C10H15O3PS, 246.0480; found, 246.0476.
Rep r esen ta tive P r oced u r e for th e P r ep a r a tion of
Oligom er s 9-11. Oligomer 5 was reacted with 3 equiv of
compound 8 in the presence of 10 equiv of NaH in dry THF,
similar to the procedure for the preparation of 5. Oligomers
9-11 were obtained in 96, 94, and 93% yields, respectively.
Com p ou n d 9. Mp: 215-217 °C. 1H NMR (CDCl3, TMS): δ
0.93-0.97 (m, 24 H), 1.38-1.41 (m, 32 H), 1.56-1.58 (m, 16
H), 1.88-1.93 (m, 16 H), 2.51 (s, 6 H), 4.04-4.09 (m, 16 H),
7.07-7.23 (m, 20 H), 7.42-7.53 (m, 24 H) ppm. 13C NMR
(CDCl3, TMS): δ 14.17, 16.01, 22.79, 26.10, 29.62, 31.78, 69.74,
110.70, 123.05, 123.36, 126.95, 127.01, 127.11, 128.22, 128.54,
135.16, 137.31, 137.63, 151.29 ppm. IR (CH2Cl2) υmax: 2863,
2842, 1601, 1215, 975 cm-1. MS m/z: 1787 (M+). HRMS: calcd
for C120H154O8S2, 1787.1085; found, 1787.1021.
1
Com p ou n d 10. Mp: 226-228 °C. H NMR (CDCl3, TMS):
δ 0.90-0.96 (m, 36 H), 1.33-1.50 (m, 48 H), 1.57-1.59 (m, 24
H), 1.89-1.95 (m, 24 H), 2.52 (s, 6 H), 4.06-4.11 (m, 24 H),
7.08-7.54 (m, 64 H) ppm. 13C NMR (CDCl3, TMS): δ 13.97,
15.98, 22.61, 25.94, 29.48, 31.62, 69.68, 110.72, 123.30, 126.79,
128.45, 137.21, 151.21 ppm. IR (CH2Cl2) υmax: 2860, 2841,
1601, 1213, 970 cm-1. MS m/z: 2596 (M+). HRMS: calcd for
C176H226O12S2, 2595.6516; found, 2595.6430.
1
Com p ou n d 11. Mp: 255-257 °C. H NMR (CDCl3, TMS):
δ 0.93-0.95 (m, 48 H), 1.40-1.42 (m, 64 H), 1.58-1.60 (m, 32
H), 1.88-1.92 (m, 32 H), 2.51 (s, 6 H), 4.07-4.10 (m, 32 H),
7.07-7.54 (m, 84 H) ppm. 13C NMR (CDCl3, TMS): δ 14.13,
15.98, 22.74, 26.06, 29.58, 31.73, 69.72, 110.69, 123.33, 126.91,
128.19, 128.52, 137.28, 151.26 ppm. IR (CH2Cl2) υmax: 2864,
2840, 1601, 973 cm-1. MS m/z: 3404 (M+). HRMS: calcd for
C232H298O16S2, 3404.1943; found, 3404.1916.
Ack n ow led gm en t. The authors thank the National
Science Council of ROC and Academia Sinica for finan-
cial support.
1
Su p p or tin g In for m a tion Ava ila ble: Copies of H NMR
and 13C NMR spectra of oligomers 5-11, monomers 3 and 4,
and small molecules 8 and 13 are included. This material is
available free of charge via the Internet at http://pubs.acs.org.
J O026907S
J . Org. Chem, Vol. 68, No. 11, 2003 4421