Synthesis of highly functionalized pyridines for planar polymers. Maximized π-conjugation in electron deficient macromolecules

Article abstract of DOI:10.1021/ja972744r

Synthetic routes to planar polypyridines are described. Two pyridine monomers for the step growth polymerization are prepared starting from 2,5- 1utidine via 2,5-dibromopyridine-3,6-dicarboxylic acid as the common intermediate, The dicarboxylic acid serve

Full text of DOI:10.1021/ja972744r

J. Am. Chem. Soc. 1998, 120, 2805-2810
2805
Synthesis of Highly Functionalized Pyridines for Planar Polymers.
Maximized π-Conjugation in Electron Deficient Macromolecules
Yuxing Yao, Jaydeep J. S. Lamba, and James M. Tour*
Contribution from the Department of Chemistry and Biochemistry, UniVersity of South Carolina,
Columbia, South Carolina 29208
ReceiVed August 7, 1997
Abstract: Synthetic routes to planar polypyridines are described. Two pyridine monomers for the step growth
polymerization are prepared starting from 2,5-lutidine via 2,5-dibromopyridine-3,6-dicarboxylic acid as the
common intermediate. The dicarboxylic acid serves as the key intermediate for the preparation of both the A
and B components for the step-growth polymerization. Several novel transformations on sensitive pyridine
cores are disclosed while preparing the monomers for the condensation polymerizations. A bis(Curtius)
rearrangement followed by tert-butyl alcohol capture of the bis(isocyanate) effects the high-yielding conversion
of carbonyl moieties to the tert-butoxycarbonyl-protected aryldiamine. Lithium-halogen exchange on the
protected diaminopyridine followed by stannylation affords the required dimetalated diamine monomer.
Treatment of the pyridine(dibromodiacid chloride) with mild cuprates or organocopper reagents affords the
pyridine(dibromodiketones). Pd/Cu-catalyzed couplings of dibromopyridines with distannylpyridines are utilized
for the polymerization schemes. This approach permits the ladder linkages of the planar polymers to (i) form
in high yields upon proton activation once the polymer backbone is intact, (ii) be substituted so that the newly
formed polypyridines are soluble, unlike many other aromatic ladder polymers, and (iii) contain double-bonded
ladder units to keep the consecutive aryl moieties planar which maximizes extended π-conjugation through
the polymer backbones, thereby increasing the bandwidths and lowering the optical band gaps. The planar
polypyridines here have optical band gaps of 1.5-2.0 eV which represent 1.3-1.8 eV smaller gaps than
nonplanarized polypyridines in similar solvents, demonstrating the efficacy of planarization for band gap
shortening.
Recent studies in nonlinear optics, light emitting diodes,
photovoltaic devices, laser systems utilizing conductive polymer
films, and optoelectronic sensors have required the preparation
of novel conjugated polymeric frameworks for enhanced
performance.1 The ability to control optical or electronic
behavior in these emerging technologies depends, in large part,
on the capability to modulate the band gaps and electron
densities in the polymeric materials at the core of the devices’
functionalities. The optoelectronic properties of conjugated
polymers vary significantly based upon the degree of extended
conjugation between the consecutive repeat units and the
describe here routes to soluble planar electron deficient hetero-
cyclic polymers based on pyridines. A convergent approach
6
is utilized wherein both the A and B components for the
condensation polymerizations arise from a common pyridine
intermediate. Functionalizations of the heterocyclic cores are
achieved using bis(Curtius) rearrangements, and dilithiation
reactions, via a lithium-halogen exchange process. The planar
polypyridines here have dramatically smaller optical band gaps
than nonplanarized polypyridines thereby demonstrating the
effectiveness of planarization for band gap shortening. More-
over, highly functionalized pyridines are of importance in a
broad range of chemistries ranging from materials science to
natural products; therefore, the new synthetic reactions described
here will likely have applications far beyond the scope of this
study.
,2
3
inherent electron densities in the polymer backbones. By
forming bridging linkages between the repeat units of conjugated
4
polymers, the extended π-conjugation can be maximized. The
majority of conjugated ladder polymers are based upon poly-
4
(
p-phenylene)s, and there are no reports of ladder polymers,
5
(4) (a) Overberger, C. G.; Moore, J. A. AdV. Polym. Sci. 1970, 7, 113.
b) Schl u¨ ter, A.-D. AdV. Mater. 1991, 3, 282. (c) Yu, L.; Chen, M. Dalton,
to our knowledge, based on electron deficient heterocycles. We
(
1) Conwell, E. Trends Polym. Sci. 1997, 5, 218.
L. R. Chem. Mater. 1990, 2, 649. (d) Hong, S. Y.; Kertesz, M.; Lee, Y. S.;
Kim, O.-K. Chem. Mater. 1992, 4, 378. (e) Godt, A.; Schl u¨ ter, A.-D. AdV.
Mater. 1991, 3, 497. (f) Yu. L.; Dalton, L. R. Macromolecules 1990, 23,
3439. (g) Scherf, U.; M u¨ llen, K. Synthesis 1992, 23. (h) Lamba, J. J. S.;
Tour, J. M. J. Am. Chem. Soc. 1994, 116, 11723. (i) Schl u¨ ter, A.-D.;
Schlicke, B. Synlett. 1996, 425. (j) Kertesz, M.; Hong, S. Y. Macromolecules
1992, 25, 5424. (k) Kintzel, O.; M u¨ nch, W.; Schl u¨ ter, A.-D.; Godt, A. J.
Org. Chem. 1996, 61, 7304. (l) Scherf, U.; M u¨ llen, K. AdV. Polym. Sci.
1995, 123, 1. (m) Roncali, J. Chem. ReV. 1997, 1733. (n) Dai, Y.; Katz, T.
J.; Nichols, D. A. Angew. Chem., Int. Ed. Engl. 1996, 35, 2109. (o) Nuckolls,
C.; Katz, T. J. Castellanos, L. J. Am. Chem. Soc. 1996, 118, 3767. (p)
Goldfinger, M. B.; Swager, T. M. J. Am. Chem. Soc. 1994, 116, 7895.
(5) For a recent study on electron rich planar conjugated polymers based
on thiophenes, see: Zhang, Q. T.; Tour, J. M. J. Am. Chem. Soc. 1997,
119, 9624
1
1
1
2
2214. (b) McCullough, R. D.; Williams, S. P. J. Am. Chem. Soc. 1993,
15, 11608. (c) Brockmann, T. W.; Tour, J. M. J. Am. Chem. Soc. 1995,
17, 4437. (d) McCullough, R. D.; Williams, S. P. Chem. Mater. 1995, 7,
001. (e) Jenekhe, S. A.; Osaheni, J. A. Macromolecules 1992, 25, 5828.
(f) Tarkka, R. M.; Zhang, X.; Jenekhe, S. A. J. Am. Chem. Soc. 1996, 118,
9
438. (g) van Mullekom, H. A. M.; Vekemans, J. A. J. M.; Meijer E. W.
Chem. Commun. 1996, 2163. (h) Delnoye, D. A. P.; Sijbesma, R. P.;
Vekemans, J. A. J. M.; Meijer, E. W. J. Am. Chem. Soc. 1996, 118, 8717.
(
i) Bao, Z.; Chan, W. K.; Yu, L. J. Am. Chem. Soc. 1995, 117, 12426. (j)
Bolognesi, A.; Bajo, G.; Paloheimo, J.; O¨ sterg a˚ rd, T.; Stubb, H. AdV. Mater.
997, 9, 121.
3) Handbook of Conducting Polymers; Skotheim, T. J., Ed.; Dekker:
New York, 1986.
1
(
S0002-7863(97)02744-3 CCC: $15.00 © 1998 American Chemical Society
Published on Web 03/13/1998

2806 J. Am. Chem. Soc., Vol. 120, No. 12, 1998
Yao et al.
The retrosynthetic strategy for the synthesis of the planar
polypyridines (1) is outlined in eq 1. The planarization was
planned via Schiff base formation between alternating amine
and ketone moieties.4h This approach permits the imine bridges
the two oxidation reactions alone. Conversion of 2 to the di-
(carboxylic acid chloride) 4 permits divergence to the two
to (i) form in high yields upon proton activation once the
polypyridine backbone is established, (ii) be substituted so that
the newly formed polymers are soluble, and (iii) contain double-
bonded ladder units to keep the consecutive aryl moieties planar
which maximize extended π-conjugation through the polypy-
needed monomers. Remarkably, conversion of 4 to the bis-
(acyl azide) under phase transfer conditions followed by a bis-
(Curtius) rearrangement and tert-butyl alcohol capture of the
isocyanates affords the bis(Boc-protected)diamine 5 in quantita-
4h,9
tive yield.
Removal of the NH protons with MeLi is followed
ridine backbones, thereby increasing the bandwidths and lower-
ing the band gaps.3 We chose to utilize dimetalodiamines and
by lithium-halogen exchange with tert-BuLi affording the
tetralithio-intermediate that is quenched with chlorotri-n-butyl-
stannane to yield the desired distannyldiamine 6 (eq 2). Use
of excess tert-BuLi, without MeLi treatment, could be prob-
lematic because lithium-halogen exchange with tert-BuLi is
faster than deprotonation of the Boc-protected amine and could
result in subsequent proton transfer and overall reduction of
dihalodiketones as the monomer units (rather than the comple-
mentary usage of dimetalodiketones and dihalodiamines) be-
cause subsequent oxidative addition reactions of the inherently
electron rich late transition metal coupling catalysts are facili-
tated by electron deficient aryl halides.2
h,i,7
Finally, the two
monomers can be prepared from the common dibromopy-
ridinedicarboxylic acid 2.
4h
5.
Stannane 6 undergoes severe decomposition during column
chromatography, and some decomposition is unavoidable even
when amine-washed silica gel is used. After workup, rapid flash
chromatography of the crude product on an amine-washed silica
gel column followed by standing in air for several days gives
colorless crystals of 6. To ensure the high purity of monomers
required for the step-growth polymerizations, 6 is further
recrystallized from methanol, thereby resulting in its low isolated
yield.
The dibromodiketone-containing pyridine monomers 7a-d
are prepared by lower order cyanocuprate or organocopper
additions to the acyl moieties. The latter neutral copper reagent
works more efficiently for the aryl additions to form 7c and
The monomers for the polymerization reactions can be
prepared rapidly as shown in eqs 2 and 3. Due to the electro-
philicity of the pyridyl ring system, 2,5-lutidine can only
undergo electrophilic bromination to afford 3 under extremely
vigorous conditions.8 The two-step permanganate oxidation
process provides far better yields of the diacid 2 than either of
(6) For recent studies on nonplanar polypyridines, see: (a) Yamamoto,
T.; Maruyama, T.; Zhou, Z.-h.; Ito, T.; Fukuda, T.; Yoneda, Y.; Begum,
F.; Ikeda, T.; Sasaki, S.; Takezoe, H.; Fukuda, A.; Kubota, K. J. Am. Chem.
Soc. 1994, 116, 4832. (b) Epstein, A. J.; Blatchford, J. W.; Wang, Y. Z.;
Jessen, S. W.; Gebler, D. D.; Lin, L. B.; Gustafson, T. L.; Wang, H.-L.;
Park, Y. W.; Swager, T. M.; MacDiarmid, A. G. Synth. Metal. 1996, 78,
2
53. (c) Yamamoto, T.; Sugiyama, K.; Kushida, T.; Inoue, T.; Kanbara, T.
J. Am. Chem. Soc. 1996, 118, 3930. For recent studies on related poly-
pyridine vinylene)s and mixed pyridine-based polymers, see: (d) Marsella,
7d. Use of ArZnCl/Pd(0) results in multiple products, presum-
(
ably from addition to the 2-position of 4 due to that center’s
activation by an R-nitrogen and a â-carbonyl moiety. Use of 4
in a Friedel-Crafts reaction to prepare 7c and 7d is unsuccess-
ful.
M. J.; Fu, D.-K.; Swager. T. M. AdV. Mater. 1995, 7, 145 (e) Tian, J.; Wu,
C.-C.; Thompson, M. E.; Sturm, J. C.; Register, R. A. Chem. Mater. 1995,
7
, 2190. (f) Bunten, K. A.; Kakkar, A. K. Macromolecules 1996, 29, 2885.
(g) Peng, Z.; Yu, L. J. Am. Chem. Soc. 1996, 118, 3777. (h) Zhu, S. S.;
Swager, T. M. AdV. Mater. 1996, 8, 497. (i) Yamamoto, T.; Zhou, Z.-h.;
Kanbara, T.; Shimura, M.; Kizu, K.; Maruyama, T.; Nakamura, Y.; Fukuda,
T.; Lee, B.-L.; Ooba, N.; Tomaru, S.; Kurihara, T.; Kaino, T.; Kubota, K.;
Sasaki, S. J. Am. Chem. Soc. 1996, 118, 10389. (j) Jenkins, I. H.; Salzner,
U.; Pickup, P. G. Chem. Mater. 1996, 8, 2444. (k) Peng, Z.; Gharavi, A.
R.; Yu, L. J. Am. Chem. Soc. 1997, 119, 4622. (l) Schanze, K. S.; Ley, K.
D.; Whittle, C. E.; Bartberger, M. D. J. Am. Chem. Soc. 1997, 119, 3423.
The polymerization reactions between 6 and 7a-d are shown
in eq 4. The optimal catalyst system for the polymerization of
the pyridine monomers is PdCl2(PPh3)2/CuI in mixed solvents
2
h,2i,7
of THF/NMP or toluene/NMP.
In the reactions, no
polypyridines are isolated without the addition of CuI, even if
the mixture is heated for 7 days. Moreover, PPh3 is the preferred
(m) Yamamoto, T.; Saitoh, Y.; Chem. Lett. 1995, 785.
(
7) (a) Stille, J. K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508. (b) Farina,
V. Pure Appl. Chem. 1996, 68, 73. (c) Farina, V.; Krishnan, B. J. Am.
Chem. Soc. 1991, 113, 9585.
(9) (a) Smith, P. A. S. Org. React. 1946, 3, 337. (b) Baumgarten, H. E.;
Smith, H. L.; Staklis, A. J. Org. Chem. 1975, 40, 3554. (c) Pfister, J. R.;
Wymann, W. E. Synthesis 1983, 38. (d) Ruediger, E. H.; Gandhi, S. S.;
Gibson, M. S.; Farcasiu, D.; Uncuta, C. Can. J. Chem. 1986, 64, 577. (e)
Binder, D.; Habison, G.; Noe, C. R. Synthesis 1977, 255.
(8) (a) Abblard, P. J.; Decoret, C.; Cronenberger, L.; Pacheco, E. H.
Bull. Soc. Chim. Fr. 1972, 6, 2466. (b) van der Does, L.; den Hertog, H. J.
Recl. TraV. Chim. Pays. Bas. 1965, 84, 951.

Synthesis of Highly Functionalized Pyridines
J. Am. Chem. Soc., Vol. 120, No. 12, 1998 2807
Table 1. Optical Data for the Polypyridines
λ
abs
λ
abs
λ
emis
a
(
THF),
(CH
2
Cl
2
/TFA,
λ
emis
2 2
(CH Cl /TFA,
a
b
compd
(nm)
3/2), (nm)
(THF), (nm)
3/2), (nm)
8
8
8
8
1
1
1
1
a
b
c
d
a
b
c
355, 438
352, 437
364, 451
363, 453
d
d
d
d
c
c
c
c
529
534
540
530
d
d
d
c
c
c
c
NE
NE
e
351, 559
355, 566
350, 512
348, 505
e
e
NE
NE
e
d
d
a
No absorptions <310 nm are listed here. The underlined values
b
are the more intense of the two listed. Excitation wavelength was 350
nm. c Addition of TFA would result in loss of the Boc group. The
d
e
polymers were not soluble in THF. No emission signal was observed.
ligand since PdCl2(AsPh3)2/CuI gives no polypyridine products.
The polar solvent additive NMP can stabilize the homogeneous
catalyst; deletion of the additive results in no polypyridines. If
only THF is used as the solvent, starting material remains after
7
days. However, some THF or toluene is needed to maintain
the solubility of these polymers. In contrast, with thiophene-
based polymerizations involving thienylstannanes and thienyl
halides, we find that Pd(dba)2/CuI/AsPh3 is the optimal system.
Figure 1. Optical Spectra of 8b (THF) (-), 1b (CH
2 2
Cl /TFA, 3/2)
5
(- - -), 8c (THF) (‚‚‚), and 1c (CH Cl /TFA, 3/2) (-‚‚‚-).
2
2
For poly(phenylene thiophene)s, Pd(dba)2/AsPh3 is the optimal
system; addition of CuI retards the coupling reaction. There-
partial loss of the Boc groups and cyclization occurs in 8a-d
5
under the polymerization conditions. Boc-protected amines are
fore, we observe no general catalyst system for this range of
arylstannane-aryl halide polymerizations; several catalyst mix-
tures need to be investigated for each particular monomer
combination. The lower molecular weights obtained for the
polymers with the aryl pendant groups, 8c and 8d, are
presumably due to greater steric interactions inhibiting the
oxidative addition, the typical slow step in the cross-coupling
reaction sequence. All the polymers are analyzed prior to
planarization by size exclusion chromatography (SEC) in THF
relative to polystyrene (PS) standards. Since SEC is a measure
of the hydrodynamic volume rather than the molecular weight,
significant yet consistent errors in Mn and Mw usually result
when comparing rigid rod polymers to the flexible coils of PS
standards. The Mn data in this range are generally larger than
the actual molecular weights by a factor of 1.5-2.10
1
1
known to be thermally labile. Hence it is more accurate to
record the yields for the two-step sequences 7a-d to 1a-d,
respectively, as shown in eq 4. Thus the imine formation
strategy provides an efficient method for planarization because
all the requisite atoms are present in the monomers; we can
avoid the difficult problem of introducing new atoms along a
rigid rod backbone from exogenous reagents. Intermolecular
Schiff bases unlikely remain in the final polymers since that
would have resulted in a cross-linked insoluble network; the
more stable six-membered imine ring is thermodynamically
preferred.
The optical absorption data were recorded in THF for 8a-d
and CH2Cl2/TFA (3/2) for 1a-d (Table 1, Figure 1). Com-
pounds 8a-d have two major absorption bands. The lower
wavelength bands are at 352-364 nm, which are close to the
absorptions of the less sterically encumbered poly(pyridine-2,5-
diyl)s (ca. 370 nm in formic acid) and poly(6-hexylpyridine-
Exposure of 8a-d to trifluoroacetic acid (TFA) induces Boc-
removal and Schiff base formation to afford the planarized
polymers 1a-d, respectively. There are only trace amounts of
carbonyl groups, and no Boc absorptions, in the FTIR spectra
of 1a-d. There are no remaining CH2CO resonances in the
2
,5-diyl) (ca. 340 nm in formic acid; ca. 320 nm in benzene).6a
However the higher wavelength absorptions at 437-453 nm in
a-d are unique. Several factors could account for this
8
1
H NMR spectrum of 1b (1a is insufficiently soluble to be
observation. First, 8a-d are partially planarized as discussed
above, thereby generating units that are further conjugated and
bathochromically shifted. Second, the amine-bearing pyridyl
units are more electron rich than the ketone-bearing pyridyl
rings. This establishes an alternating electron donor/acceptor
arrangement which generates intramolecular charge-transfer
character along the polymer backbone that can result in large
clearly examined by NMR). The weak carbonyl absorptions
are probably derived from the end groups. Further heating in
an amine solvent at high temperature is required for the clean
cyclization/planarization of 8a and 8c. As with other ladder
polymers that we have prepared, the planar polypyridines are
4
h,5
only soluble in acidic media such as CH2Cl2/TFA (3/2).
It
is apparent from the spectral and elemental analysis data that
(
11) Greene, T. W.; Wuts, P. G. M. ProtectiVe Groups in Organic
(10) Tour, J. M. Chem. ReV. 1996, 96, 537.
Synthesis, 2nd ed.; Wiley: New York, 1991.

2808 J. Am. Chem. Soc., Vol. 120, No. 12, 1998
Yao et al.
bathochromic shifts.5,6i,12 Third, intramolecular hydrogen bond-
ing between the protons of Boc-protected amines and the
adjacent pyridine nitrogens may induce planarity in the polymer
GC analyses were obtained using an Alltech model 932525 (25 m ×
0
.25 mm, 0.2 µm film of AT-1 stationary phase) capillary GC column.
Alkyllithium reagents were obtained from FMC. Reagent grade diethyl
ether and tetrahydrofuran (THF) were distilled under nitrogen from
sodium benzophenone ketyl. Reagent grade benzene and dichlo-
romethane were distilled over calcium hydride. Bulk grade hexane
was distilled prior to use. Gravity column chromatography, silica gel
plugs, and flash chromatography were carried out using 230-400 mesh
silica gel from EM Science. Thin-layer chromatography was performed
using glass plates precoated with silica gel 60 F254 with a layer thickness
of 0.25 mm purchased from EM Science. Unless otherwise noted, all
monomers for the polymerizations were >99.5% pure, and all other
nonpolymeric materials were >96% pure as judged by NMR, GC, or
combustion analyses. The absorption and emission spectral data are
listed in Table 1, while the molecular weight data are listed in the
equations.
backbones and further extend the π-conjugations with concomi-
tant bathochromic shifts.2
e-h
These factors notwithstanding,
there are enormous bathochromic shifts upon Schiff base
formation (8a-d to 1a-d, respectively) indicative of greater
electron delocalizations through the polymer backbones once
planarizations are achieved (Table 1, Figure 1). Since Boc-
removal and planarization would have accompanied the study
of 8a-d in acidic solvents, and the different solvent systems
(
neutral versus acidic) can have influences on the degree of
5
intramolecular charge transfer in the planar systems, further
comparisons between the optical spectra of 8a-d and 1a-d
would not be conclusive. However, the best analogy comes
from comparison of 1a-d with the reported poly(pyridine-2,5-
diyl) and poly(6-hexylpyridine-2,5-diyl) wherein all the spectra
were recorded in an acidic environment. There are ca. 200 nm
bathochromic shifts in the planarized polypyridines versus the
nonplanar polypyridines. Poly(pyridine-2,5-diyl) and poly(6-
2
,5-Dibromo-3,6-dimethylpyridine (3).8 The procedure by Abblard
was modified as follows. A stock solution of 70% fuming sulfuric
acid was prepared by slowly adding molten SO (40 g) to commercially
6a
3
available 30% fuming sulfuric acid (15.7 mL) and storing it in a Teflon-
capped bottle. To 70% fuming sulfuric acid (30 mL) in a screw cap
tube cooled to -78 °C was slowly added 2,5-lutidine (11.6 mL, 100
mmol) and bromine (7.2 mL, 140 mmol). The tube was capped, and
the mixture was warmed to room temperature and then heated to 100
6a
hexylpyridine-2,5-diyl) have optical band gaps of 3.3 eV, while
the planar polymers here have 1.3-1.8 eV smaller optical band
gaps (1a ) 1.5 eV, 1b ) 1.5 eV, 1c ) 2.0 eV, 1d ) 2.0 eV as
determined from the tailing edge of the optical spectra). This
demonstrates the efficacy of the planarization strategy for
obtaining dramatic decreases in the optical band gaps of
conjugated polymers. Attempts to cast films of 1a-d from CH2-
Cl2/TFA followed by removal of the solvent in vacuo does not
permit salt removal as judged by FTIR analysis.6i
Emission signals with large Stokes shifts are apparent for
the preplanar polymers 8a-d in THF. Polymers 1a-d showed
no emission signals; a trend we have observed in other nitrogen-
containing planar aromatic polymers (Table 1).5 Therefore, the
nitrogen atoms play a key role in exciton quenching.
In summary, synthetic routes to planar polypyridines are
described which represent the first examples of planar conju-
gated polymers based on electron deficient heterocycles.
Several novel transformations of the pyridine intermediates are
used to attain the desired monomers. These include bis(Curtius)
rearrangements and bis(metalation) reactions by lithium-
halogen exchange to afford highly functionalized pyridines. Pd/
Cu-couplings yield the polymerized products that can be easily
planarized via the formation of imine bridges by proton
activation. Thus the effective formation of electron deficient
ladder polymers is achieved which demonstrates the efficacy
of ladder formation for intense optical band gap shortening.
Further optoelectronic studies may reveal unique properties of
these planar polymers which could also act as proton acceptors
and metal binders.
°
C. After 41 h, the temperature was raised to 120 °C and held there
for an additional 9 h. The solution was allowed to cool to room
temperature and poured onto ice. The precipitate was collected by
filtration. The solid was washed with water and dissolved in ether
and filtered. The ether solution was washed with water (3×) and dried
over magnesium sulfate. Removal of solvent in vacuo gave 23.0 g
(
87%; 90% based on the 96% purity of commercially available 2,5-
8a
lutidine) of 3 as a white solid. Mp 87-88 °C (lit. 92 °C). FTIR
(KBr) 3415, 3138, 3015, 1574, 1523, 1420, 1384, 1333, 1128, 1077,
-
1
1
969, 753 cm
H), 2.31 (s, 3 H). C NMR (100 MHz, CDCl
141.83, 133.97, 120.08, 23.98, 21.18.
,5-Dibromo-3,6-pyridinedicarboxylic Acid (2). To 3 (21.76 g,
2.1 mmol) in pyridine (120 mL) at 100 °C was added aqueous
potassium permanganate (58.4 g/750 mL of H O) over 4 h through a
.
H NMR (400 MHz, CDCl
3
) δ 7.61 (s, 1 H), 2.58 (s,
13
3
3
) δ 155.49, 141.92,
2
8
2
dropping funnel. After the addition, the mixture was stirred until the
purple color disappeared. The reaction mixture was cooled to ca. 60
°C and filtered. The residue was washed with hot water and ethyl
acetate. The aqueous layer was extracted with ethyl acetate (2×). The
combined organics gave unreacted starting material 3 (4.23 g). The
aqueous solvent was removed to give a white solid which was a mixture
of potassium salts of the diacid and monoacid. This solid was
redissolved in water (150 mL). The solution was heated to reflux,
aqueous potassium permanganate (19 g/250 mL water) was added over
4
0 min, and the solution was further stirred for 1 h. The reaction
mixture was cooled to room temperature, and methanol (10 mL) was
added. Filtration and removal of solvent afforded a white solid. The
solid was acidified to ca. pH ) 1 with 3 N HCl. The resultant slurry
was extracted with ethyl acetate (3×). The extracts were washed with
brine and dried over magnesium sulfate. Removal of solvents in vacuo
afforded 2 as a white solid (18.21 g, 85% on reacted 3). Mp 171-173
°
1
C. FTIR (KBr) 3500-2100, 1707, 1569, 1446, 1379, 1328, 1272,
Experimental Section
-
1
1
6
226, 1066, 923, 785 cm . H NMR (400 MHz, DMSO-d ) δ 8.5 (s,
13
General Methods. Unless otherwise noted, all operations were
carried out under a dry, oxygen-free nitrogen atmosphere. Molecular
weight analyses were performed using two 30 × 75 cm Burdick and
1 H). C NMR (100 MHz, DMSO-d ) δ 165.36, 165.07, 153.10,
6
144.06, 137.30, 133.77, 116.14.
3
,6-Dibromo-2,5-pyridinedi(carboxylic acid chloride) (4). To 2
5
Jackson GPC columns (10 Å 10 µ and 500 Å 5 µ) eluted with THF
(13.17 g, 40.5 mmol) in benzene (100 mL) was added one drop of
at 60 °C (flow rate 1.0 mL/min). Molecular weight results were based
DMF and oxalyl chloride (10.8 mL, 122 mmol). The mixture was
heated to reflux for 6 h. The resulting golden yellow clear solution
was cooled to room temperature. The solvent was removed in vacuo
to give 4 as a crystalline yellow solid (14.72 g, 100%). Mp 62-67
on five polystyrene standards (M ) 435 500, 96 000, 22 000, 5050,
w
and 580 with a correlation coefficient >0.9998) purchased from
Polymer Laboratories Ltd. Combustion analyses were obtained from
Atlantic Microlab, Inc., P.O. Box 2288, Norcross, GA 30091. Capillary
°
7
C. FTIR (KBr) 3073, 1749, 1560, 1389, 1323, 1200, 1089, 922, 850,
-
1
1
13
13 cm
.
H NMR (400 MHz, CDCl
3
) δ 8.46 (s, 1 H). C NMR
(12) (a) Ferraris, J. P.; Bravo, A.; Kim, W.; Hrncir, D. C. J. Chem. Soc.,
(
1
100 MHz, CDCl
16.86.
N,N′-Di(tert-butoxycarbonyl)-2,5-diamino-3,6-dibromopyridine
(5). A solution of 4 (7.6 g, 21.0 mmol) in dichloromethane (40 mL)
3
) δ 165.14, 163.51, 151.11, 145.79, 136.73, 136.14,
Chem. Commun. 1994, 991. (b) Karikomi, M.; Kitamura, C.; Tanak, S.;
Yamashita, Y. J. Am. Chem. Soc. 1995, 117, 6791. (c) Havinga, E. E.; Ten
Hoeve, W.; Wynberg, H. Polym. Bull. 1992, 29, 119. (d) Zhang, Q. T.;
Tour, J. M. J. Am. Chem. Soc. 1997, 119, 5065.

Synthesis of Highly Functionalized Pyridines
J. Am. Chem. Soc., Vol. 120, No. 12, 1998 2809
was added to a mixture of tetra-n-butylammonium bromide (12 mg),
saturated aqueous sodium azide (20 mL, 130 mmol, ca. 6.4 M), and
dichloromethane (20 mL) at -5 to 0 °C over 20 min. The mixture
was further stirred for 10 min at -5 to 0 °C. The organic layer was
separated. The aqueous layer was extracted with cold dichloromethane
2,5-Bis(1′-oxo-n-tridecyl)-3,6-dibromopyridine (7b). To a solution
of tert-butyllithium (30.3 mL, 50 mmol, 1.65 M in pentane) in ether
(20 mL) at -78 °C was added 1-iodododecane (6.3 mL, 25 mmol)
dropwise. The solution was warmed to 0 °C and transferred via cannula
to a suspension of copper(I) cyanide (2.53 g, 28 mmol) in THF (45
mL) at -78 °C. The slurry was stirred for 25 min before warming to
0 °C. The resultant green/black solution was recooled to -78 °C, and
a precooled THF (10 mL) solution of 4 (3.62 g, 10 mmol) at -78 °C
was added by cannula. The slurry was stirred for 10 min at -78 °C.
(
2×). Combined organic fractions were washed with cold water (2×)
and cold brine (1×). The solution was dried over magnesium sulfate
at 0 °C for 10 min and filtered. The filtrate was stirred with calcium
hydride at 0 °C for 45 min. The mixture was filtered through a pad of
Celite. To the filtrate (ca. 200 mL) was added tert-butyl alcohol (44
mL, 460 mmol), and the mixture was heated to reflux for 12 h. The
colorless solution was cooled to room temperature. Removal of solvents
in vacuo gave 5 as a white solid (9.81 g, 100%). Mp 164 °C (dec).
FTIR (KBr) 3303, 2985, 2933, 1703, 1564, 1528, 1513, 1364, 1354,
4 4
A saturated solution of NH Cl/NH OH (9/1, 50 mL) was added. The
mixture was warmed to room temperature and filtered. The aqueous
phase was separated and extracted with ether (2×). Combined organic
fractions were washed with water (2×) and brine (1×). The solution
was dried over magnesium sulfate. The solvent was removed in vacuo.
-
1
1
1
272, 1256, 1231, 1149, 1103, 1046, 1026, 764 cm
.
H NMR (400
2 2
The residues were dissolved in a hexane/CH Cl mixture (3/2) and
MHz, CDCl
3
) δ 8.67 (br s, 1 H), 6.98 (br s, 1 H), 6.88 (br s, 1 H), 1.51
filtered through a plug of silica gel. Removal of the solvents in vacuo
followed by recrystallization from hexane gave 7b as light yellow
crystals (4.32 g, 69%). Mp 58-60 °C. FTIR (KBr) 2913, 2854, 1703,
13
(
1
s, 9 H), 1.50 (s, 9 H). C NMR (100 MHz, CDCl
3
) δ 151.91, 150.82,
42.31, 131.58, 130.91, 127.74, 110.22, 82.17, 81.67, 28.21, 28.19.
: 464.9899. Found: 464.9883.
-
1
1
HRMS calcd for C15
H21Br
2
N O
3 4
1560, 1466, 1406, 1312, 1099, 955, 901, 777, 717 cm
400 MHz CDCl ) δ 7.84 (s, 1 H), 3.03 (t, J ) 7.3 Hz, 2 H), 2.91 (t,
J ) 7.3 Hz, 2 H), 1.69 (p, J ) 7.2 Hz, 2 H), 1.67 (p, J ) 7.5 Hz, 2 H),
.24 (m, 36 H), 0.86 (t, J ) 7.0 Hz, 6 H). 13C NMR (100 MHz, CDCl
δ 200.92, 199.95, 154.05, 142.26, 141.06, 134.80, 116.45, 42.72, 40.04,
.
H NMR
(
3
N,N′-Di(tert-butoxycarbonyl)-2,5-bis(tri-n-butylstannyl)-3,6-di-
aminopyridine (6). Methyllithium (1.3 mL, 2.2 mmol, 1.67 M in ether)
was added dropwise to a suspension of 5 (0.467 g, 1.00 mmol) in ether
1
3
)
(
-
10 mL) at 0 °C. After 30 min, the pale yellow slurry was cooled to
78 °C, and tert-butyllithium (2.9 mL, 4.5 mmol, 1.57 M in pentane)
was added. The mixture was stirred at -78 °C for 40 min and another
0 min at room temperature. The resultant brown slurry was recooled
3
1.91, 29.69, 29.65, 29.62, 29.57, 29.46, 29.41, 29.34, 29.08, 29.02,
2
3.80, 23.53, 22.68, 14.11. Anal. Calcd for C31 NO : C, 59.14;
H
51Br
2
2
H, 8.16; N, 2.22. Found: C, 59.22; H, 8.10; N, 2.23. HRMS calcd
for C31 NO : 627.2287. Found: 627.2283.
3
H51Br
2
2
to -78 °C. Chlorotri-n-butylstannane (1.4 mL, 5 mmol) was added,
followed by THF (10 mL). The solution was allowed to warm to room
temperature and was stirred for 50 min before pouring into water. The
aqueous phase was extracted with ether. The combined organic
fractions were washed with water and brine. The solution was dried
over sodium sulfate, and the solvent was removed in vacuo. Flash
chromatography (silica gel, treated with 10% triethylamine in hexane,
then rinsing with hexane, and using hexane as eluent) gave a yellow
oil. The oil was left standing in air for 5 days and crystals formed.
The crystals were washed with methanol and recrystallized from
methanol to afford 6 as colorless cubic crystals (0.281 g, 32%). Mp
2,5-Bis(p-tert-butylbenzoyl)-3,6-dibromopyridine (7c). To p-(tert-
butyl)bromobenzene (3.20 g, 15 mmol) in THF (15 mL) at -78 °C
was added tert-butyllithium (17.9 mL, 30 mmol, 1.68 M in pentane)
dropwise. The solution was stirred for 20 min and transferred via
cannula to a suspension of copper(I) bromide dimethyl sulfide complex
(3.29 g, 16 mmol) in THF (25 mL) at -78 °C. The mixture was stirred
for 35 min. To this mixture was added by cannula a precooled THF
(6 mL) solution of 4 (1.81 g, 5 mmol) at -78 °C. The resultant slurry
was stirred for 20 min at -78 °C. A saturated solution of NH
4
Cl/
NH OH (9/1, 10 mL) was added. The mixture was warmed to room
4
8
1
6-87 °C. FTIR (KBr) 3223, 3169, 3116, 2957, 2913, 2860, 1698,
temperature and filtered. The aqueous phase was separated and
extracted with ether (2×). Combined organic fractions were washed
with 1 N HCl (1×), water (2×), and brine (1×). The solution was
dried over magnesium sulfate and then filtered. Removal of solvents
-1
1
560, 1501, 1458, 1384, 1362, 1245, 1154, 1064 cm
) δ 7.84 (br s, 1 H), 6.87 (s, 1 H), 6.12 (br s, 1 H), 1.57-
.50 (m, 12 H), 1.48 (s, 9 H), 1.47 (s, 9 H), 1.35-1.26 (m, 12 H), 1.09
t, J ) 8.2 Hz, 6 H), 1.02 (t, J ) 8.3 Hz, 6 H), 0.87 (t, J ) 7.3 Hz, 18
. H NMR (400
MHz, CDCl
1
(
3
followed by flash chromatography [silica gel, hexane/Et
2
O (12/1) and
1
3
H). C NMR (100 MHz, CDCl
3
) δ 154.33, 153.52, 137.79, 128.10,
0.33, 29.14, 29.07, 28.34, 28.31, 27.48, 27.34, 13.66, 13.63, 11.64,
0.32. Anal. Calcd for C39 Sn : C, 52.78; H, 8.52; N, 4.73.
then hexane/CH Cl (1/1) as eluent], and recrystallization from ethyl
2
2
8
1
acetate gave 7c as white crystals (1.37 g, 49%). Mp 204.5-206 °C.
FTIR (KBr) 3046, 2964, 2872, 1682, 1600, 1564, 1462, 1415, 1364,
H N
75 3
O
4
2
12
14
66
16
120
-1
1
Found: C, 52.84; H, 8.52, N, 4.67. HRMS calcd for
Sn
35
C H
N
3
O
4
-
1323, 1262, 1190, 1169, 933, 908, 846, 733 cm
CDCl ) δ 7.88 (s, 1 H), 7.80 (d, J ) 8.4 Hz, 2 H), 7.78 (d, J ) 8.4 Hz,
H), 7.54 (d, J ) 8.0 Hz, 2 H), 7.52 (d, J ) 8.2 Hz, 2 H), 1.35 (s, 9
. H NMR (400 MHz,
2
(M-C
4 9
H ): 832.3079. Found: 832.3076.
3
2
2,5-Bis(1′-oxo-n-pentyl)-3,6-dibromopyridine (7a). To a suspen-
1
3
H), 1.34 (s, 9 H). C NMR (100 MHz CDCl
3
) δ 191.47, 190.74,
59.06, 158.73, 157.50, 141.23, 139.62, 136.32, 132.25, 131.55, 130.47,
30.33, 126.13, 125.93, 116.58, 35.44, 35.39, 31.02. Anal. Calcd for
NO : C, 58.19; H, 4.88; N, 2.51. Found: C, 58.32; H, 4.92;
N, 2.41. HRMS calcd for C27 NO : 555.0409. Found: 555.0406.
sion of copper(I) cyanide (2.26 g, 25 mmol) in THF (50 mL) at -78
C was added dropwise n-butyllithium (14.5 mL, 22 mmol, 1.52 M in
hexane). The slurry was warmed to -20 °C and then recooled to -78
C. A precooled THF (10 mL) solution of 4 (3.62 g, 10 mmol) at
78 °C was transferred via cannula to the above green/black cuprate
slurry. The slurry was stirred for 15 min at -78 °C. A saturated
solution of NH Cl/NH OH (9/1, 50 mL) was added. The mixture was
1
1
°
C
27
H
27Br
2
2
°
-
H27Br
2
2
2,5-Bis(p-n-octylbenzoyl)-3,6-dibromopyridine (7d). To p-(n-
octyl)bromobenzene4h (5.65 g, 21 mmol) in THF (20 mL) at -78 °C
was added tert-butyllithium (25 mL, 42 mmol, 1.68 M in pentane)
dropwise. The solution was stirred for 15 min and added by cannula
to a suspension of copper(I) bromide dimethyl sulfide complex (4.52
g, 22 mmol) in THF (30 mL) at -78 °C. The mixture was stirred for
20 min. To the mixture was added by cannula a precooled THF (6
mL) solution of 6 (3.62 g, 10 mmol) at -78 °C. The resultant slurry
4
4
warmed to room temperature and filtered. The aqueous phase was
separated and extracted with ether (2×). The combined organic
fractions were washed with water (2×) and brine (1×). The solution
was dried over magnesium sulfate and filtered. Removal of the solvent
in vacuo followed by flash chromatography [silica gel, hexane/ether
(
15:1)] gave 7a as a pale yellow solid (3.7 g, 91%). Mp 45-46 °C.
FTIR (KBr) 2964, 2933, 2872, 1713, 1564, 1462, 1405, 1328, 1256,
was stirred for 20 min at -78 °C. A saturated solution of NH
4
Cl/
-
1
1
1
195, 1123, 1092, 1015, 974, 769 cm
.
H NMR (400 MHz, CDCl
3
)
NH OH (9/1, 10 mL) was added. The mixture was warmed to room
4
δ 7.83 (s, 1 H), 3.04 (t, J ) 7.3 Hz, 2 H), 2.92 (t, J ) 7.3 Hz, 2 H),
temperature and filtered. The aqueous phase was separated and
extracted with ether (2×). Combined organic fractions were washed
with 1 N HCl (1×), water (2×), and brine (1×). The solution was
dried over magnesium sulfate and then filtered. Removal of solvents
followed by flash chromatography [silica gel, hexane/ethyl acetate (20/
1
.69 (p, J ) 7.4 Hz, 2 H), 1.67 (p, J ) 7.5 Hz, 2 H), 1.39 (sext, J )
.6 Hz, 4 H), 0.933 (t, J ) 7.3 Hz, 3 H), 0.930 (t, J ) 7.4 Hz, 3 H).
7
1
3
C NMR (100 MHz CDCl
34.78, 116.44, 42.42, 39.74, 25.84, 25.59, 22.22, 22.18, 13.88, 13.81.
NO : C, 44.47; H, 4.73; N, 3.46. Found:
3
) δ 200.88, 199.90, 154.05, 142.25, 141.07,
1
Anal. Calcd for C15
H
19Br
2
2
2 2
1) and then CH Cl as eluent], and recrystallization from hexane gave
C, 44.47; H, 4.67; N, 3.48. HRMS calcd for C15
Found: 402.9763.
2 2
H19Br NO : 402.9782.
7d as white cotton-like crystals (2.41 g, 36%). Mp 101.5-102.5 °C.
FTIR (KBr) 3056, 2954, 2923, 2851, 1677, 1662, 1605, 1333, 1251,

2810 J. Am. Chem. Soc., Vol. 120, No. 12, 1998
Yao et al.
1
164, 1082, 939, 908 cm-1. 1H NMR (400 MHz, CDCl
3
) δ 7.88 (s, 1
General Procedure for Imine-Bridge Formation. To a solution
of the polymer in dichloromethane was added trifluoroacetic acid (TFA).
The mixture was heated to reflux overnight. After cooling to room
temperature, the solution was carefully and slowly added to a mixed
solvent of triethylamine and dichloromethane. The precipitate was
collected by filtration. The solid was suspended in triethylamine and
heated in a screw cap tube. The solution was filtered. The residue
was further washed with dichloromethane and ether.
H), 7.77 (d, J ) 7.9 Hz, 2 H), 7.75 (d, J ) 7.9, 2 H), 7.33 (d, J ) 8.6
Hz, 2 H), 7.30 (d, J ) 8.5, 2 H), 2.69 (t, J ) 6.2 Hz, 2 H), 2.67 (t, J
)
7.3 Hz, 2 H), 1.64 (m, 4 H), 1.30-1.25 (m, 20 H), 0.86 (t, J ) 6.8
13
Hz, 6 H). C NMR (100 MHz, CDCl
3
) δ 191.50, 190.79, 157.45,
51.13, 150.84, 141.24, 139.63, 136.37, 132.54, 131.83, 130.61, 130.48,
29.18, 128.99, 116.58, 36.22, 31.84, 30.98, 29.39, 29.28, 29.20, 22.65,
4.10. Anal. Calcd for C35 NO : C, 62.79; H, 6.47; N, 2.09.
NO
1
1
1
H43Br
2
2
Found: C, 62.68; H, 6.50; N, 2.09. HRMS calcd for C35
67.1661. Found: 667.1636.
General Procedure for Polymerization Reactions of Pyridine-
Derived Monomers. To an oven dried screw cap tube was added the
dibromodiketone monomer (1.0 equiv), 6 (1.02 equiv), PdCl (PPh
0.02 equiv), and CuI (0.02 equiv). The tube was transferred to a
H43Br
2
2
:
Polymer 1a. Used were 8a (0.565 g), dichloromethane (20 mL),
and TFA (10 mL), and the polymer precipitated from the solution.
Further precipitation was performed from triethylamine (35 mL) and
dichloromethane (35 mL). The solid and triethylamine (15 mL) were
heated to 100 °C for 10 h and 180 °C for 1 day. 1a was obtained as
a dark brown solid (0.380 g, 74% over two steps). FTIR (KBr) 3395,
6
2
3 2
)
(
nitrogen-filled drybox. To the tube was added THF (toluene was used
for 8c) and NMP. The tube was capped and heated to 90 °C for 2
days (unless otherwise stated). The reaction mixture was cooled to
room temperature. Dichloromethane (10 mL) was added, and the
mixture was filtered through a pad of Celite. The solution was
concentrated in vacuo to ca. 10 mL which was then added to acetone
2
1
954, 2923, 2862, 1697 (w), 1574, 1503, 1462, 1395, 1369, 1292-
108, 903, 821 cm . No H NMR data could be obtained due to the
-
1
1
20 4 n
minimal solubility. Anal. Calcd for (C20H N )
: C, 75.92; H, 6.37;
N, 17.71. Found: C, 69.26; H, 6.00; N, 15.27. The precipitation from
the dichloromethane/TFA mixture, hence the low degree of solubility,
1
3
likely contributed to the poor elemental analysis data obtained.
(methanol was used for 8d) (150 mL) dropwise. The precipitate was
collected by filtration. The solid was dissolved in a minimal amount
of chloroform, and the fractional precipitation procedure was repeated.
As stated previously, the analytical analysis data suggested that partial
cyclization had occurred; therefore, the yield was calculated after the
planarization step.
Polymer 1b. Used were 8b (0.481 g), dichloromethane (20 mL),
and TFA (10 mL). Precipitation was performed from triethylamine
(30 mL) and dichloromethane (20 mL). The solid in triethylamine (15
mL) was heated to 90 °C for 6 h. 1b was obtained as a black solid
(0.40 g, 92% over two steps) that had a solubility of ca. 6 mg/mL in
Polymer 8a. Used were 6 (1.810 g, 2.04 mmol), 7a (0.810 g, 2.00
CH Cl /TFA (2:1). FTIR (KBr) 2925, 2848, 1707 (w), 1576, 1465,
1397, 1387, 1363, 1295, 1101, 908, 820. H NMR (300 MHz, TFA/
2
2
1
mmol), PdCl
2
(PPh
)
3 2
(0.028 g, 0.04 mmol), CuI (0.008 g, 0.04 mmol),
THF (20 mL), and NMP (10 mL). 8a was obtained as a brown solid
CDCl 1:1) δ 1.30 (br s, 44 H), 0.88 (br s, 6 H). Anal. Calcd for
3
(
1
0.695 g). FTIR (cast) 3210, 2954, 2933, 2872, 1728, 1574, 1503,
(C H N ) : C, 79.95; H, 9.69; N, 10.36. Found: C, 75.28; H, 9.24;
36
52
4 n
467, 1369, 1236, 1154, 1082, 1051, 764 cm-
1
.
1
H NMR (400 MHz)
13
N, 10.05.
1
3
δ 8.0-7.4 (br m), 4.0-3.0 (br m), 2.3-0.9 (br m). C NMR (125
MHz, CDCl ) δ 204.0, 166.6, 153.6-121.4, 81.8, 44.3, 39.5, 35.0,
1.6-13.6. Anal. Calcd for (C30 : C, 65.20; H, 7.29; N,
0.14. Found: C, 67.83; H, 6.85; N, 13.07.
Polymer 8b. Used were 6 (0.869 g, 0.98 mmol), 7b (0.604 g, 0.96
mmol), PdCl (PPh (0.014 g, 0.019 mmol), CuI (0.004 g, 0.019 mmol),
Polymer 1c. Used were 8c (0.892 g), dichloromethane (30 mL),
and TFA (15 mL). Precipitation was performed from triethylamine
3
3
1
40 4 6 n
H N O )
(50 mL) and dichloromethane (30 mL). The solid in triethylamine (20
mL) was heated at 100 °C for 13 h and 180 °C for 24 h. 1c was
obtained as a brown solid (0.868 g, 64% over two steps) that had a
2
3 2
)
solubility of ca. 38 mg/mL in CH
2
Cl
2
/TFA (2:1). FTIR (KBr) 3385,
THF (12 mL), and NMP (5 mL). The solution was heated to 80 °C
for 3.5 days. 8b was obtained as a brown solid (0.572 g). FTIR (cast)
3
1
1
056, 2964, 2903, 2872, 1667 (w), 1605, 1492, 1456, 1395, 1364, 1267,
-
1
1
195, 1103, 1021, 949, 836 cm
:1) δ 8.8-7.6 (m, 8 H), 1.8-1.2 (m, 18 H). Anal. Calcd for
: C, 82.02; H, 6.02; N, 11.96. Found: C, 77.16; H, 6.26;
. H NMR (300 MHz, TFA/CDCl
3
3
1
210, 2923, 2851, 1728, 1703, 1574, 1503, 1467, 1369, 1236, 1154,
-
1
1
082, 1051, 764, 718 cm
3
. H NMR (400 MHz, CDCl ) δ 7.8-7.1
(C
32
H
28
N
4
1
)
n
3
(
br m), 3.7-3.1 (br m), 2.13 (br m), 1.7-1.5 (br m), 1.2 (br m), 0.8
13
N, 11.32.
(
br m). C NMR (125 MHz CDCl
21.3, 87.4, 54.1-53.4, 32.3-28.8, 23.0, 14.4. Anal. Calcd for
: C, 71.10; H, 9.34; N, 7.21. Found: C, 74.11; H, 9.23;
3
) δ 204.1, 169.1-165.7, 153.5-
1
Polymer 1d. Used were 8d (0.196 g), dichloromethane (15 mL),
and TFA (5 mL). Precipitation was performed from triethylamine (30
mL) and dichloromethane (10 mL). The solid in triethylamine (10 mL)
was heated to 80 °C for 1 day. 1d was obtained as a brown solid
(0.144 g, 80% over two steps) that had a solubility of ca. 30 mg/mL in
(C
H N O )
46 72 4 6 n
N, 8.60.
Polymer 8c. Used were 6 (0.453 g, 0.51 mmol), 7c (0.279 g, 0.5
mmol), PdCl (PPh (0.007 g, 0.01 mmol), CuI (0.002 g, 0.01 mmol),
2
3 2
)
toluene (3 mL), and NMP (3 mL). The solution was heated to 100 °C
for 21 h. Another portion of 6 (0.013 g, 0.015 mmol) and toluene (1
mL) was added. The solution was further stirred at 100 °C for 2 days.
CH
1553, 1461, 1383, 1301, 1183, 1121, 1018, 951, 838, 807 cm
NMR (300 MHz, TFA/CDCl 1:1) δ 8.9-7.6 (m, 8 H), 3.0 (m, 4 H),
1.9 (m, 4 H), 1.4 (m, 20 H), 0.97 (m, 6 H). Anal. Calcd. for
: C, 82.72; H, 7.64; N, 9.65. Found: C, 80.08; H, 7.65;
2 2
Cl /TFA (2:1). FTIR (KBr) 2925, 2857, 1666 (w), 1610, 1579,
-
1
1
.
H
3
8
3
1
cm
m).
1
c was obtained as a dark brown solid (0.155 g). FTIR (cast) 3313,
067, 2964, 2903, 2872, 1728, 1672, 1605, 1569, 1508, 1477, 1395,
364, 1267, 1236, 1154, 1108, 1077, 1015, 944, 908, 846, 764, 728
44 4 n
(C40H N )
13
N, 9.40.
-
1
1
.
H NMR (400 MHz, CDCl
3
) δ 8.7-7.4 (br m), 1.8-1.0 (br
) δ 162.9-153.5, 149.9-139.5,
1
3
C NMR (125 MHz, CDCl
3
Acknowledgment. Support came from the Office of Naval
Research and the National Science Foundation (DMR-9158315,
CHE-9601723). We thank FMC for a gift of alkyllithium
reagents.
35.4-121.3, 81.2, 35.4, 31.9, 31.5, 28.6. Anal. Calcd for
42 48 4 6 n
(C H N O ) : C, 71.57; H, 6.86; N, 7.95. Found: C, 74.41; H, 6.47;
N, 9.76.
Polymer 8d. Used were 6 (1.810 g, 2.04 mmol), 7d (1.339 g, 2.00
mmol), PdCl (PPh (0.028 g, 0.04 mmol), CuI (0.008 g, 0.04 mmol),
2
3 2
)
THF (10 mL), and NMP (10 mL). The solution was heated to 100 °C
for 3 days. 8d was obtained as a brown solid (1.252 g). FTIR (cast)
JA972744R
3
292, 2954, 2923, 2851, 1728, 1667, 1605, 1569, 1549, 1503, 1462,
-1
1
410, 1364, 1308, 1267, 1236, 1154, 1076, 1046, 1015, 939, 846 cm
.
(13) It is common to obtain low carbon values in combustion analyses
of highly unsaturated polymers based on arene structures. This is due to
incomplete combustion with remaining carbon residues. In most cases, the
H and N values remain reasonably accurate. See ref 4h and (a) Chimil, K.;
Scherf, U. Makromol. Chem., Rapid Commun. 1993, 14, 217. (b) Wallow,
T. I.; Novak, B. M. J. Am. Chem. Soc. 1991, 113, 7411. (c) Stephens, E.
B.; Tour, J. M. Macromolecules 1993, 26, 2420.
1
H NMR (400 MHz, CDCl
3
) δ 8.6-7.2 (br m), 2.8 (br m), 1.7-0.8
br m). C NMR (125 MHz CDCl ) δ 198.0-193.0, 159.5-120.8,
2.5-81.1, 36.5, 32.6-28.6, 23.1, 14.6, 14.5. Anal. Calcd for
: C, 73.50; H, 7.89; N, 6.86. Found: C, 77.36; H, 7.56;
1
3
(
8
3
(C
H N O )
50 64 4 6 n
N, 8.40.