Exploiting the versatility of organometallic cross-coupling reactions for entry into extended aromatic systems

Article abstract of DOI:10.1016/S0022-328X(02)01166-X

Using a variety of Pd-catalyzed cross-coupling techniques, we have prepared several pendant arene derivatives (5,6,12,15). From these materials, we have expanded upon earlier work and developed new electrophilic cyclization strategies. By employing suffic

Full text of DOI:10.1016/S0022-328X(02)01166-X

Journal of Organometallic Chemistry 653 (2002) 215–222
www.elsevier.com/locate/jorganchem
Exploiting the versatility of organometallic cross-coupling reactions
for entry into extended aromatic systems
John D. Tovar, Timothy M. Swager *
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts A6enue, Room 18-209, Cambridge, MA 02139, USA
Received 3 September 2001; accepted 5 October 2001
Abstract
Using a variety of Pd-catalyzed cross-coupling techniques, we have prepared several pendant arene derivatives (5, 6, 12, 15).
From these materials, we have expanded upon earlier work and developed new electrophilic cyclization strategies. By employing
sufficiently strong electrophile sources, we may efficiently effect double annulations to afford polycyclic aromatics 10, 11, 13 and
16. This chemistry allows for the participation of both heteroaromatic and heteroatomic moieties thus providing an electronically
diverse array of extended aromatic systems. © 2002 Elsevier Science B.V. All rights reserved.
Keywords: Polycyclic aromatics; Electrophilic; Dehydrogenation; Cyclization; Pyrylium
ately substituted alkoxy donors as models for 1. We
found conditions to effect high yielding, often quantita-
tive, cyclization to the corresponding benzo- and phen-
anthro-fused anthracenes [5]. The potential for utilizing
such discrete polycyclic aromatics as higher mobility
FET materials has spurned the development of syn-
thetic methods for new and otherwise challenging poly-
cyclic scaffolds. Notably, Mu¨llen has elegantly applied
a cyclodehydrogenation scheme to the synthesis of ‘su-
peracene’ graphite sheets, [6] while Anthony has re-
cently developed a strategy to access higher acenes and
rylenes through sequential Bergman cyclizations [7]. In
this study, we report an extension of our methodology
[5] where we now utilize stronger amine donors as
cyclization directing groups. Key to the study of this
cyclization chemistry, the model compounds presented
herein shall attest to the power and specificity of
organometallic cross-coupling methodologies towards
constructing extended, differentially functionalized pol-
yaromatic systems.
1. Introduction
Fully aromatic ladder polymers represent extended
electronic structures of high stability for potential uti-
lization in a variety of electronic applications. Schlu¨ter
first elaborated the synthesis of such fully aromatized
ribbons by dehydrogenation of a polymeric Diels–
Alder adduct [1]. In 1993, Chmil and Scherf disclosed a
ketone condensation route to phenacene-type graphite
ribbons; [2] shortly thereafter, our group reported a
structurally similar polymer by way of an acid-induced
electrophilic cyclization of the alkyne appended
polyphenylene 1 to provide the aromatized ribbon 2 [3].
Very recently, Bard utilized the inherent stability of
such fused ladder polymers in the design of robust
electrochromic materials [4]. Common to all these ap-
proaches, the verification of the ‘polymer-analogous’
chemistry requires study of appropriate molecular mod-
els that allow for more rigorous structural characteriza-
tion. With respect to 1 and 2, our group studied smaller
terphenyl and quinquephenyl systems with appropri-
(1)
* Corresponding author. Tel.: +1-617-253-4423; fax: +1-617-253-
7929.
E-mail address: tswager@mit.edu (T.M. Swager).
0022-328X/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(02)01166-X

216
J.D. To6ar, T.M. Swager / Journal of Organometallic Chemistry 653 (2002) 215–222
With these precursor models readily available, we
2. Results and discussion
could assess the competency of the stronger amine
donors in the electrophilic cyclization. In line with our
previous results, the starting terphenyls reacted immedi-
ately upon addition of trifluoroacetic acid; however, a
basic work-up only regenerated the starting materials.
We postulated that the enhanced basicity of the amine-
substituted terphenyls allowed for mere protonation of
the amino moiety rather than an electrophilic attack
and cyclization on the acetylene. To support this claim,
we performed NMR experiments with 5 at room tem-
perature that indicated no new aryl or olefinic protons
upon TFA addition. These measurements revealed that
the alkynes persisted under such acidic conditions (13C
resonances at 92.1 and 91.6 ppm) while the N-butyl
amine chains exhibited an a-methylene resonance at
59.9 ppm, significantly downfield from the value of 50.9
ppm exhibited by 5. The absence of any new products
resulting from rehybridization of the alkynes of 5 confi-
rms that the protonated donor A was the most favor-
able species under the cyclization conditions at room
temperature (depicted in Scheme 2). Subsequently, we
found that the cyclization proceeded smoothly under
refluxing conditions to provide the cyclized dibenz[a,h]-
anthracene systems 10–11 in excellent yields. Consis-
tent with earlier findings, the enhanced degree of aro-
maticity in the cyclized materials provided downfield
shifts in the proton NMR for the dibenzanthracene ring
protons. Furthermore, the extension of the p-conju-
gated pathway via rigidification provided red-shifted
(ca. 28 nm between 6 and 11), weakly-allowed transi-
tions often observed in similar polycyclic aromatic
systems.
We developed two different synthetic routes to ob-
tain the desired amine-donor terphenyl models 5 and 6,
both of which rely on Sonogashira and Suzuki proto-
cols [8,9]. Scheme 1 depicts both of these synthetic
routes, as well as the final cyclization step. The first
route (Route A) installs the dibutylamine donor early
and allows entry to polymerizable substrates, in anal-
ogy with our previous studies [5a]. Starting from the
halide 3, [10] Sonogashira cross-coupling of TMS acety-
lene installed two alkynes chemoselectively at the iodo
positions. Subsequent protiodesilylation and Sono-
gashira cross coupling of N,N-dibutyliodoaniline [11]
provided the dibromide 4, again taking advantage of
the differential reactivity between bromo- and iodo-
substituted arenes. From 4, Suzuki cross-coupling of
dimethyl- or dimethoxy phenylboronic acid provided
the terphenyls 5 and 6, respectively, in high yields. The
second route (Route B) initially constructs a desired
terphenyl, allowing for the addition of a donor direct-
ing functionality at a later stage. Analogous to the
preparation of 4, chemoselective Sonogashira cross-
coupling of TIPS acetylene provided the dibromide 7.
The robustness of the TIPS protecting groups allowed
for clean Suzuki cross-coupling with dimethyl- or
dimethoxy phenylboronic acid without apparent desily-
lation. Fluoride-promoted deprotection of the TIPS
moieties then provided 8–9 in modest overall yields
from 7. From these terminal alkynes, Sonogashira
cross-coupling with N,N-dibutyliodoaniline again pro-
vided 5–6 in high yield. Over both four-step proce-
dures, Route A provided higher overall yields from the
halide parent 3:5 (Route A, 44%; Route B, 30%), 6
(Route A, 37%; Route B, 25%).
One of the limitations of our earlier methodology
arose from the fact that ethynyl cyclization onto a
thienyl moiety (as opposed to an arene) often provided
Scheme 1. Reagents and conditions: (a) Sonogashira: (Ph3P)2PdCl2, CuI, PhMe, DIPA; (b) deprotection: K2CO3, THF, MeOH, rt; (c) Suzuki:
Pd(PPh3)4, Na2CO3, PhMe, EtOH, H2O, reflux; (d) deprotection: TBA, THF, H2O, rt.

J.D. To6ar, T.M. Swager / Journal of Organometallic Chemistry 653 (2002) 215–222
217
Scheme 2.
rearrangement products, and unsubstituted thienyls did
not undergo cyclization at all [5a]. To test if the amine
donor would allow for more efficient entry into thio-
phene-fused anthracenes, we prepared bisthienyl deriva-
tive 12 through Stille cross coupling between 4 and
tributyltin thiophene (Scheme 3) [12]. Initial cyclization
attempts with TFA provided no reaction, even under
refluxing conditions. Fortunately, when we employed
the much stronger triflic acid as the electrophilic proton
source, we obtained the cyclized anthracene 13 in mod-
erate yield. We envisioned that an unsubstituted thio-
phene-based monomer such as 13 would allow for
electrodeposition of highly stable, electroactive polymer
films; however, the readily oxidized aryl amines pen-
dant to the aromatic scaffold complicated efforts to
characterize the electrochemical behavior of 13. As a
result, anodic oxidation led to completely irreversible
activity but no apparent polymer film deposition. We
have observed that other thiophene-based polycyclic
aromatics of comparable size to 13 afford highly stable,
multiply charged species upon electrochemical oxida-
tion and that polymers incorporating such units exhibit
electrochromicity and robust environmental stability
[13].
findings for dibenz[a,h]anthracenes (vide supra), these
salts exhibit lower energy charge-transfer optical transi-
tions upon cyclization (umax=539 nm in CHCl3 for 16).
Our current investigations seek to utilize this chemistry
towards the construction of larger electron deficient
aromatics.
3. Concluding remarks
In closing, we have described extensions to an acid-
induced electrophilic cyclization of pendant alkynes to
provide electronically diverse families of polycyclic aro-
matics. By harnessing the versatility of the
organometallic cross-coupling reaction, we may readily
construct a variety of substrates through which we may
design and examine new reaction manifolds. The array
of polyaromatics available on behalf of this generality
stands to provide exciting new materials for current
electronics and photonics applications.
4. Experimental
We found that a similar methodology applied to
heteroatoms in addition to arenes and heterocycles,
where we could employ a carbonyl oxygen in place of
an arene to trap the electrophilic site of intermediate B
(Scheme 2) [14]. Our group has studied a number of
amide-containing poly(p-phenyleneethynylene)s (PPEs),
[15] and we saw them as attractive candidates for
post-polymerization modification involving a pyrylium
intermediate. From the halide 14, [15a] Sonogashira
cross-coupling afforded 15, a model for the amide PPE
system (Scheme 4). Much like the situation for 12,
subjection of 15 to the TFA cyclization conditions
failed to provide any isolable, cyclized materials. The
use of a stronger acid (HBF4) allowed the deep bur-
gundy-colored cyclized salt 16 to precipitate upon addi-
tion of ethyl ether to the reaction solution. Our studies
on smaller isobenzopyrylium compounds demonstrated
that this cyclization reaction could couple with addi-
tional chemical ring transformations in one synthetic
step, thus providing isoquinoline ring systems from
readily available aryl alkynes [14,16]. In line with our
General: all air and water sensitive synthetic manipu-
lations were performed under an argon atmosphere
using standard Schlenk techniques. All chemicals were
of reagent grade and used as received: anhydrous diiso-
Scheme 3.
Scheme 4.

218
J.D. To6ar, T.M. Swager / Journal of Organometallic Chemistry 653 (2002) 215–222
1
propylamine (DIPA), methylene chloride and tetrahy-
drofuran (THF) were purchased from Aldrich and used
without further purification. The following abbrevia-
tions have been used: N,N-dibutyl-4-iodoaniline
(BuNI); 2,5-dimethylphenyl boronic acid (Me2B(OH)2);
2,5-dimethoxyphenyl boronic acid ((MeO)2B(OH)2).
Column chromatography was performed using Baker
40 mm silica gel. All organic extracts were dried over
MgSO4 and filtered prior to removal. NMR spectra
were obtained on a Bruker AC-250, Varian Mercury-
300 or Varian Inova-500 spectrometers, and all chemi-
ther purification. H-NMR (250 MHz, CDCl3): 7.72 (s,
2H), 3.50 (s, 2H). HR–MS (EI): found m/z=
281.868090.00056 (M+); calc. for C10H4Br2:
281.8680%.
4.3. 2,5-Bis(4-(N,N-dibutylamino)phenylethynyl)-1,4-
dibromobenzene (4)
A
solution of BuNI (7.14 g, 21.56 mmol),
(Ph3P)2PdCl2 (519 mg, 0.739 mmol) and CuI (541 mg,
2.84 mmol) in THF (75 ml) and DIPA (10 ml) was
stirred under argon for 20 min. To this, a solution of
2,5-bisethynyl-1,4-dibromobenzene (2.77 g, 9.76 mmol)
in THF (25 ml) was transferred dropwise under argon,
followed by a THF rinse (25 ml). The reaction was
stirred at r.t. for 17 h at which point it was diluted with
ether and NH4Cl (aq.). The organic layer was washed
with NH4Cl and NaCl, dried and removed in vacuo to
provide a crude material that was chromatographed on
silica gel (4:1 hexane/CH2Cl2). Recrystallization from
CH2Cl2/MeOH yielded the product as an orange pow-
der (4.47 g, 6.47 mmol, 66%). Melting point (m.p.)
1
cal shifts are referenced to CHCl3 (7.26 ppm for H,
77.23 ppm for 13C) and TMS or CHDCl2 (5.32 ppm).
High resolution mass spectra were obtained at the MIT
Department of Chemistry Instrumentation Facility
(DCIF) on a Finnigan MAT 8200 using a peak match-
ing protocol to determine the mass and error range of
the molecular ion; FAB spectra were obtained using a
3-nitrobenzyl alcohol matrix. UV–vis measurements
were obtained on a Hewlett–Packard 8452A diode
array spectrophotometer. Fluorescence measurements
were recorded on a SPEX Fluorolog-t2 fluorimeter
(model FL112, 450 W Xe lamp). Elemental analyses
were obtained at Desert Analytics (Tucson, AZ). Melt-
ing points are uncorrected.
1
143–144.5 °C. H-NMR (250 MHz, CDCl3): 7.69 (s,
hH), 7.39 (d, 4H, J=8.56 Hz), 6.58 (d, 4H, J=8.65
Hz), 3.29 (t, 8H, J=7.22 Hz), 1.57 (quin, 8H, J=6.30
Hz), 1.35 (sex, 8H, J=7.43 Hz), 0.96 (t, 12H, J=
7.20Hz). 13C-NMR (125 MHz, CDCl3): 148.62, 135.43,
133.36, 126.43, 123.30, 111.35, 107.88, 98.66, 85.65,
50.90, 29.55, 20.52, 14.22. FTIR (KBr): w (cm−1): 2955,
2929, 2870, 2208, 1604, 1520, 1373, 1287, 1191, 1144,
1055, 811, 423. HR–MS (EI): found m/z=688.20289
0.0014 (M+); calc. for C38H46Br2N2: 688.2028%.
4.1. 2,5-Bis(trimethylsilylethynyl)-1,4-dibromobenzene
(en route to 4)
Under an argon atmosphere, 125 ml THF was added
to 3 (6.00 g, 12.3 mmol), (Ph3P)2PdCl2 (860.3 mg, 1.266
mmol) and CuI (745.4 mg, 3.91 mmol). After the
addition of 15 ml DIPA, the solution was stirred at
room temperature (r.t.) for 15 min followed by the
dropwise addition of TMS acetylene (3.65 ml, 25.8
mmol). After stirring for 17 h at r.t., an ethereal
solution of the reaction mixture was washed with
NH4Cl (×2) and brine. The organic phase was dried
and removed in vacuo to provide crude material that
was chromatographed on silica gel (hexane) to yield the
desired product (4.67 g, 10.90 mmol, 89%) as a pale
yellow solid which was used without further purifica-
tion. 1H-NMR (250 MHz, CDCl3): 7.67 (s, 2H), 0.27 (s,
18H). 13C-NMR (125 MHz, CDCl3): 136.62, 126.63,
123.91, 103.27, 101.56, −0.10.
4.4. 2%,5%-Bis(4-(N,N-dibutylamino)phenyl)ethynyl-
2,2¦,5,5¦-tetramethyl[1,1%:4%,1¦]terphenyl (5)
A mixture of 4 (100 mg, 0.144 mmol), Me2B(OH)2
(108 mg, 0.721 mmol), KOH (113 mg, 2.01 mmol) and
Pd(PPh3)4 (18 mg, 0.016 mmol) were placed under
argon followed by the addition of 1.5 ml toluene, 0.5 ml
ethanol and 1.0 ml water. A reflux condenser was
attached under a purge of argon, and the reaction was
stirred at reflux for 20 h at which point the solution was
cooled to r.t. and diluted with toluene, ether and 2 M
KOH (aq.). The organic layer was washed with 2 M
KOH, 1 M HCl and brine, dried and removed in vacuo
to provide a reddish oil. Chromatography on silica
(3.5:1 hexane/CH2Cl2) yielded the desired product as a
yellow solid (86 mg, 0.116 mmol, 80%). M.p. 123–
4.2. 2,5-Bisethynyl-1,4-dibromobenzene (en route to 4)
A solution of 2,5-bis(trimethylsilylethynyl)-1,4-dibro-
mobenzene (4.439 g, 10.36 mmol) and K2CO3 (5.73 g,
41.5 mmol) in 65 ml THF and 65 ml MeOH was stirred
at r.t. for 7 h. The reaction was diluted with ether and
washed with brine and NH4Cl (×2), and the organic
layer was dried and removed in vacuo to yield a light
brown solid (2.734 g, 9.63 mmol, 93%) which was of
limited stability and was, therefore, used without fur-
1
124.5 °C. H-NMR (250 MHz, CDCl3): 7.44 (s, 2H),
7.19 (d, 2H, J=7.6 Hz), 7.15 (s, 2H), 7.11 (d, 2H,
J=7.60 Hz), 6.98 (d, 4H, J=8.70 Hz), 6.46 (d, 4H,
J=8.82 Hz), 3.22 (t, 8H, J=7.30 Hz), 2.37 (s, 6H),
2.27 (s, 6H), 1.50 (quin, 8H, J=6.18 Hz), 1.32 (sex,
8H, J=7.57 Hz), 0.93 (t, 12H, J=7.19 Hz). 13C-NMR
(125 MHz, CDCl3): 147.97, 142.80, 140.41, 134.64,

J.D. To6ar, T.M. Swager / Journal of Organometallic Chemistry 653 (2002) 215–222
219
133.69, 132.89. 132.16, 130.85, 129.68, 128.29, 122.77,
111.25, 109.14, 95.23, 87.27, 50.87, 29.56, 21.22, 20.51,
19.82, 14.19. FTIR (KBr): w (cm−1): 2955, 2928, 2870,
2202, 1605, 1521, 1367, 1193, 1136, 811. HR–MS (EI):
found m/z=740.507090.0015 (M+); calc. for
C54H64N2: 740.5070%.
NMR (125 MHz, CDCl3): 147.35, 139.10, 134.37,
133.28, 132.79, 132.57, 132.25, 130.86, 130.28, 130.06,
129.98, 129.88, 129.47, 127.07, 111.48, 51.13, 29.70,
26.93, 25.38, 20.66, 14.30. FTIR (KBr): w (cm−1): 2954,
2930, 2868, 1609, 1517, 1457, 1365, 1180, 1105, 915,
817, 784. HR–MS (EI): found m/z=740.507090.0015
(M+); calc. for C54H64N2: 740.5070%.
4.5. 2%,5%-Bis(4-(N,N-dibutylamino)phenyl)ethynyl-
2,2¦,5,5¦-tetramethoxy[1,1%:4%,1¦]terphenyl (6)
4.7. 5,12-Bis(4-(N,N-dibutylamino)phenyl)ethynyl-
1,4,8,11-tetramethoxydibenz[a,h]anthracene (11)
A mixture of 4 (340 mg, 0.492 mmol), (MeO)2B(OH)2
(534 mg, 2.93 mmol), Na2CO3 (858 mg, 8.09 mmol) and
Pd(PPh3)4 (80 mg, 0.069 mmol) was placed under argon
followed by the addition of toluene (19 ml), ethanol (4
ml) and water (4 ml). The system was opened and
purged for 10 min to allow for attachment of a reflux
condenser, and the reaction was stirred at reflux for 19
h. The reaction was worked up as for compound 5 and
subsequent chromatography on silica (1:1 hexane/
CH2Cl2) yielded 306 mg of the desired product as a
reddish white solid. Recrystallization from CH2Cl2/
MeOH yielded a pure product as a fluffy pale yellow
solid (269 mg, 0.334 mmol, 68%). M.p. 168–169 °C.
1H-NMR (300 MHz, CDCl3): 7.57 (s, 2H), 7.05 (d, 4H,
J=8.7 Hz), 7.02 (d, 2H, J=2.4 Hz), 6.93 (m, 4H), 6.47
(d, 4H, J=9.0 Hz), 3.81 (s, 6H), 3.78 (s, 6H), 3.23 (t,
8H, J=7.8 Hz), 1.53 (quin, 8H, J=8.1 Hz), 1.33 (sex,
8H, J=7.5 Hz), 0.94 (t, 12H, J=7.2 Hz). 13C-NMR
(125 MHz, CDCl3): 153.33, 151.65, 147.88, 139.30,
133.15, 132.90, 130.55, 122.98, 116.76, 114.63, 112.52,
111.25, 109.40, 94.71, 87.58, 56.69, 56.05, 50.88, 29.56,
20.52, 14.20. FTIR (KBr): w (cm−1): 2951, 2921, 2863,
2013, 1604, 1520, 1473, 1366, 1225, 1194, 1054, 812.
UV–vis (CHCl3) u (nm) (log m): 314 (4.46), 387 (4.74),
402 (4.73). Emission (CHCl3) umax (nm): 437. HR–MS
(EI): found m/z=804.486690.0016 (M+); calc. for
C54H64N2O4: 804.4866%.
To a solution of 6 (49 mg, 0.061 mmol) in CH2Cl2 (6
ml) under argon was added 60 ml TFA, and the reac-
tion was refluxed for 20 h. After working up as for
compound 10, the residual crude solid was chro-
matographed on silica (3:2 CH2Cl2/hexane) to yield the
desired product as a yellow solid (44 mg, 0.055 mmol,
1
91%). H-NMR (250 MHz, CDCl3): 10.10 (s, 2H), 7.84
(s, 2H), 7.30 (d, 4H, J=8.45 Hz), 7.19 (d, 2H, J=8.62
Hz), 7.07 (d, 2H, J=8.75 Hz), 6.73 (d, 4H, J=8.38
Hz), 4.14 (s, 6H), 3.47 (s, 6H), 3.34 (t, 8H, J=7.15 Hz),
1.62 (quin, 8H, J=6.28 Hz), 1.40 (sex, 8H, J=7.53
Hz), 0.99 (t, 12H, J=7.18 Hz). 13C-NMR (125 MHz,
CDCl3): 154.26, 151.96, 146.72, 136.05, 133.69, 132.87,
131.29, 129.12, 128.12, 127.94, 125.12, 122.88, 111.67,
111.10, 109.66, 57.62, 56.51, 51.26, 29.80, 20.67, 14.31.
FTIR (KBr): w (cm−1): 2928, 2868, 1612, 1518, 1428,
1371, 1254, 1186, 1115, 1068, 1033, 922, 796, 731, 415.
UV–vis (CHCl3) l (nm) (log m): 251 (4.60), 281 (4.76),
319 (4.71), 405 (4.22), 431 (4.15). Emission (CHCl3)
umax (nm): 437, 468. HR–MS (EI): found m/z=
804.486690.0016 (M+); calc. for C54H64N2O4:
804.4866%.
4.8. 2,5-Bis(triisopropylsilylethynyl)-1,4-dibromobenzene
(7)
Under an argon atmosphere, 200 ml THF was added
to 3 (9.88 g, 20.26 mmol), (Ph3P)2PdCl2 (1.01 g, 1.43
mmol) and CuI (0.596 g, 3.13 mmol). After the addition
of 25 ml DIPA, the solution was stirred at r.t. for 15
min followed by the dropwise addition of triisopropylsi-
lylacetylene (10 ml, 44.58 mmol). After stirring for 40 h
at r.t., the reaction was worked up as described for 4.
The crude material was pushed through a silica gel plug
to provide 11 g of a white solid contaminated with the
starting diiodide. Recrystallization from CH2Cl2/hexane
provided a total of 4.75 g of a purer product, and
further recrystallization from isopropanol provided an
additional 3.77 g. All collected solids were further
chromatographed on silica (hexanes) to yield 6.62 g of
the desired product as a white solid in pure form next
to 0.95 g of a mixture containing an additional 0.686 g
of the desired product as determined by 1H-NMR
integration against an internal standard. In addition,
534 mg of the starting material was recovered (1.09
4.6. 5,12-Bis(4-(N,N-dibutylamino)phenyl)ethynyl-
1,4,8,11-tetramethyldibenz[a,h]anthracene (10)
To a solution of 5 (20 mg, 0.027 mmol) in CH2Cl2 (3
ml) under argon was added trifluoroacetic acid (TFA,
80 ml), and the reaction was refluxed for 2 days, cooled
and quenched with NaHCO3 (aq.). After dilution with
CH2Cl2, the organic layer was washed with NaHCO3
and brine, dried and removed in vacuo. The crude solid
was chromatographed on silica (1:1 hexane/CH2Cl2) to
yield the desired product as a yellow solid (16 mg, 0.022
1
mmol, 82%). M.p. 211–213 °C. H-NMR (300 MHz,
CD2Cl2): 9.09 (s, 2H), 7.72 (s, 2H), 7.44 (d, 2H, J=7.5
Hz), 7.26 (d, 2H, J=7.5 Hz), 7.21 (d, 4H, J=8.4 Hz),
6.72 (d, 4H, J=8.7 Hz), 3.34 (t, 8H, J=7.5 Hz), 3.20
(s, 6H), 2.11 (s, 6H), 1.64 (quin, 8H, J=7.8 Hz), 1.40
(sex, 8H, J=8.1 Hz), 0.99 (t, 12H, J=7.2 Hz). 13C-

220
J.D. To6ar, T.M. Swager / Journal of Organometallic Chemistry 653 (2002) 215–222
mmol, 5.4%). Total desired product: 7.31 g (12.25
mmol, 64% based on recovered starting material). H-
NMR (250 MHz, CDCl3): 7.67 (s, 2H), 1.14 (s, 42H).
13C-NMR (125 MHz, CDCl3): 136.74, 126.81, 123.95,
103.41, 100.00, 18.87, 11.46. FTIR (KBr): w (cm−1):
2924, 2864, 2164, 1460, 1342, 1064, 883, 811, 674, 585.
flask followed by THF (25 ml) and water (2 ml). The
system was briefly purged with a stream of argon at
which point a 1 M solution of TBAF in THF (5 ml, 5
mmol) was added dropwise. The reaction was stirred at
r.t. for 45 h and the reaction was diluted with ether and
washed with NaCl (×3). The organic layer was dried
and removed in vacuo to yield a white solid (148 mg,
0.442 mmol, 95%) which was used without further
1
4.9. 2%,5%-Bis(triisopropylsilylethynyl)-2,2¦,5,5¦-
tetramethyl[1,1%:4%,1¦]terphenyl (en route to 8)
1
purification. H-NMR (500 MHz, CDCl3): 7.44 (s, 2H),
7.17 (d, 2H, J=8 Hz), 7.12 (d, 2H, J=7.5 Hz), 7.07 (s,
2H), 3.01 (s, 2H), 2.36 (s, 6H), 2.20 (s, 6H).
A 100 Schlenk flask was charged with 7 (1.004 g,
1.683 mmol), Me2B(OH)2 (1.111 g, 7.41 mmol), KOH
(1.5 g, 26.7 mmol) and Pd(PPh3)4 (278 mg, 0.241 mmol)
and placed under argon. Toluene (19 ml), ethanol (10
ml) and water (15 ml) were added, and the system was
purged for 15 min to allow for the installation of a
reflux condenser. The reaction was heated at reflux for
14 h and worked up similar to 5. The crude material
was chromatographed on silica gel (hexanes) to yield
the desired product as a white solid (820 mg, 1.267
mmol, 75%). 1H-NMR (500 MHz, CDCl3): 7.39 (s,
2H), 7.10 (d, 2H, J=8.0 Hz), 7.04 (m, 4h), 2,32 (s, 3H),
2.17 (s, 3H), 0.90 (s, 42H). 13C-NMR (125 MHz,
CDCl3): 143.86, 140.00, 134.88, 133.27, 130.27, 129.89,
128.49, 123.05, 105.72, 95.35, 21.07, 19.80, 18.64, 11.36.
FTIR (KBr): w (cm−1): 2941, 2863, 2157, 1482, 1460,
1188, 995, 882, 808, 677, 594, 422. HR–MS (EI): found
m/z=646.439090.0013 (M+); calc. for C44H62Si2:
646.4390%.
4.12. 2%,5%-Diethynyl-2,2¦,5,5¦-tetramethoxy-
[1,1%:4%,1¦]terphenyl (9)
The TIPS tetramethoxy terphenyl (listed at 4.9, 300
mg, 0.421 mmol) was placed in a 100 ml round bottom
flask followed by THF (35 ml) and water (2 ml). The
system was briefly purged with a stream of argon at
which point a 1 M solution of TBAF in THF (5 ml, 5
mmol) was added dropwise. The reaction was stirred at
r.t. for 5 days, and an additional 5 ml of TBAF
solution (5 mmol) was added. After a total of 6 days,
workup as described for 8 provided a white solid (149
mg, 0.375 mmol, 89%) that was used without further
1
purification. H-NMR (250 MHz, CDCl3): 7.57 (s, 2H),
6.92 (bm, 6H), 3.80 (s, 6H), 3.78 (s, 6H), 3.03 (s, 2H).
13C-NMR (125 MHz, CDCl3): 153.41, 151.25, 140.27,
134.99, 129.36, 122.46, 116.97, 114.58, 112.50, 82.88,
80.83, 56.45, 56.01.
4.10. 2%,5%-Bis(triisopropylsilylethynyl)-2,2¦,5,5¦-
tetramethoxy[1,1%:4%,1¦]terphenyl (en route to 9)
A 100 Schlenk flask was charged with 7 (1.005 g,
1.684 mmol), (MeO)2B(OH)2 (1.347 g, 7.40 mmol),
KOH (1.4 g, 26.7 mmol) and 278 mg Pd(PPh3)4 (278
mg, 0.241 mmol) and placed under argon. Toluene (19
ml), ethanol (10 ml) and water (15 ml) were added, and
the system was purged for 15 min to allow for the
installation of a reflux condenser. The reaction was
heated at reflux for 14 h and worked up similar to 5.
The crude material was chromatographed on silica gel
(2:1 hexanes/CH2Cl2) to yield the desired product as a
4.13. 5 (Route B)
BuNI (336 mg, 1.01 mmol) was placed in a 10 ml
Schlenk flask under argon and diluted with toluene (3
ml). To another 10 ml Schlenk flask was added 8 (148
mg, 0.4419 mmol) and toluene (3 ml). A 25 ml Schlenk
flask was charged with (Ph3P)2PdCl2 (31 mg, 0.044
mmol) and CuI (28 mg, 0.145 mmol) and was placed
under argon. The BuNI solution was then transferred
into the catalyst mixture followed by a toluene rinse (1
ml) and the dropwise addition of DIPA (0.6 ml). This
solution was stirred for 10 min at which point the
solution of 8 was cannulated in dropwise followed by a
toluene rinse (1 ml) and a THF rinse (1 ml). The
reaction was stirred at r.t. for 20 h and worked up
similar to 4. Silica gel chromatography (4:1 hexanes/
CH2Cl2) yielded 212 mg of clean product as a oily
yellow solid (0.286 mmol, 70%). Recrystallization from
CH2Cl2/EtOH again yielded the desired product as a
yellow solid (151 mg, 71% recovery). Characterization
data described above.
1
white solid (750 mg, 1.055 mmol, 63%). H-NMR (500
MHz, CDCl3): 7.48 (s, 2H), 8.86 (m, 6H), 3.77 (s, 6H),
3.74 (s, 6H), 0.93 (s, 42H). 13C-NMR (125 MHz,
CDCl3): 153.46, 151.31, 140.46, 134.06, 130.26, 123.40,
116.92, 114.21, 112.27, 106.11, 94.78, 56.48, 55.97,
18.70, 11.38. HR–MS (EI): found m/z=710.41879
0.0014 (M+); calc. for C44H62O4Si2: 710.4187%.
4.11. 2%,5%-Diethynyl-2,2¦,5,5¦-tetramethyl-
[1,1%:4%,1¦]terphenyl (8)
The TIPS tetramethyl terphenyl (listed at 4.8, 301
mg, 0.465 mmol) was placed in a 50 ml round bottom

J.D. To6ar, T.M. Swager / Journal of Organometallic Chemistry 653 (2002) 215–222
221
4.14. 6 (Route B)
was quenched with NaHCO3 and the organic phase was
washed with NaHCO3 (×2) and brine, dried and re-
moved. The crude material was purified on silica gel
(3:1 hexane/CH2Cl2) to provide the desired product as a
deep burgundy–red solid (105 mg, 0.151 mmol, 51%).
BuNI (290.6 mg, 0.877 mmol) was placed in a 10 ml
Schlenk flask under argon and diluted with THF (3 ml).
To another 10 ml Schlenk flask was added 9 (149 mg,
0.375 mmol) and THF (3 ml). A 25 ml Schlenk flask
was charged with (Ph3P)2PdCl2 (26 mg, 0.038 mmol)
and CuI (22 mg, 0.116 mmol) and was placed under
argon. Following the procedure for 5 (Route B), the
reaction was stirred at r.t. for 2 days and worked up
similar to 4. Silica gel chromatography (1:1 hexanes/
CH2Cl2) yielded 211 mg of product as a pale yellow
solid (0.262 mmol, 70%). Recrystallization from
CH2Cl2/MeOH provided the desired compound as a
off-white-beige needles (141 mg, 67% recovery). Char-
acterization data described above.
1
M.p. 208–209 °C. H-NMR (500 MHz, CDCl3): 7.76
(s, 2H), 7.59 (d, 4H, J=8,5 Hz), 7.48 (s, 2H), 7.46 (d,
2H, J=5.0 Hz), 7.14 (d, 2H, J=5.0 Hz), 6.70 (d, 4H,
J=9.0 Hz). 13C-NMR (125 MHz, CDCl3): 148.45,
145.57, 142.05, 141.88, 132.72, 131.79, 129.34, 126.99,
125.14, 123.54, 123.25, 111.21, 110.58, 50.98, 29.68,
20.58, 14.26. FTIR (KBr): w (cm−1): 2954, 2858, 1594,
1520, 1367, 1186, 1140. UV–vis (CHCl3) u (nm) (log m):
287 (4.46), 314 (4.53), 361 (4.55), 470 (4.74). HR–MS
(EI): found m/z=696.356190.0020 (M+); calc. for
C46H52N2S2: 696.3572%. Anal: calc. for C46H52N2S2: C,
79.26; H, 7.52; N, 4.02. Found: C, 78.98; H, 7.74; N,
3.89%.
4.15. 2,5-Bis(4-(N,N-dibutylamino)phenylethynyl)-1,4-
bis(thiophen-2-yl)benzene (12)
4.17. 2,5-Bis(4-decyloxyphenylethynyl)-1,4-
di(N,N-dioctylcarbamoyl)benzene (15)
A 50 ml Schlenk flask was charged with 4 (1.000 g,
1.448 mmol) and (Ph3P)2PdCl2 (50 mg, 0.071 mmol)
and placed under argon. DMF was added (15 ml) and
heated to 80 °C. Upon complete dissolution of the
solids, 2-(tributylstannyl)thiophene was added dropwise
(1.13 ml, 3.56 mmol), and the reaction stirred at 80 °C
for 68 h. Upon cooling, the mixture was pushed
through a pad of celite, and the organic eluent was
diluted with ether, washed with brine (×3), dried and
removed in vacuo. The crude material was pushed
through a silica plug (hexane to 1:1 hexane/CH2Cl2) to
provide a brown material, which was subjected to fur-
ther column chromatography (hexane to 2:1 hexane/
CH2Cl2). Removal of the solvents provided the desired
product as a bright yellow solid (753 mg, 1.080 mmol,
75%). M.p. 157.5–158.5 °C. 1H-NMR (500 MHz,
CDCl3): 7.82 (s, 2H), 7.74 (d, 2H, J=2.5 Hz), 7.37 (d,
4H, J=8.5 Hz), 7.14 (dd, 2H, J=4.5, 4.5 Hz), 6.59 (d,
4H, J=8.5 Hz), 3.29 (t, 8H, J=7.0 Hz), 1.58 (m, 8H),
1.36 (sex, 8H, J=8.0 Hz), 0.97 (t, 12H, J=7.5 Hz).
13C-NMR (125 MHz, CDCl3): 148.30, 141.68, 133.80,
133.29, 133.00, 127.30, 126.96, 126.00, 120.78, 111.38,
108.80, 97.26, 87.52, 50.91, 29.56, 20.53, 14.23. FTIR
(KBr): w (cm−1): 2953, 2927, 2868, 2198, 1604, 1520,
1367, 1192, 1135, 810. UV–vis (CHCl3) u (nm) (log m):
289 (4.54), 334 (4.68), 417 (4.73). HR–MS (EI): found
m/z=696.357290.0014 (M+); calc. for C46H52N2S2:
696.3572%.
A 10 ml Schlenk flask was charged with 14 (400 mg,
0.463 mmol), (Ph3P)2PdCl2 (18 mg, 0.026 mmol) and
CuI (11 mg, 0.056 mmol) and placed under argon. THF
(2 ml) and DIPA (1 ml) were added and the solution
was stirred at r.t. during the addition of a solution of
(p-decyloxy)phenylacetylene (254 mg. 0.983 mmol) in
THF (0.5 ml). After addition, very thick precipitates
formed, and toluene was added to facilitate stirring (1
ml). After 3 h at r.t., the reaction was worked up
similar to 4 while subsequent purification on silica gel
(9:1 hexane/EtOAc) yielded a yellowish solid (310 mg,
1
0.275 mmol, 60%). H-NMR (250 MHz, CDCl3): 7.42
(s, 2H), 7.38 (d, 4H, J=8.7 Hz), 6.83 (d, 4H, J=8.81
Hz), 3.95 (t, 4H, J=6.5 Hz), 3.75 (bm, 2H), 3.16 (bm,
6H), 1.0–1.9 (bm, 80H), 0.85 (m, 18H). 13C-NMR (75
MHz, CDCl3): 168.9, 159.8, 139.8, 133.4, 130.2, 120.5,
114.67, 114.63, 95.2, 85.2, 68.3, 48.8, 44.9, 32.1, 31.9,
29.77, 29.71, 29.60, 29.53, 29.44, 29.39, 29.32, 28.8,
27.9, 27.4, 26.9, 26.2, 22.88, 22.83, 14.34, 14.28. FTIR
(KBr): w (cm−1): 2923, 2853, 2212, 1636, 1603, 1512,
1249, 1173, 837. HR–MS (FAB): found m/z=
1125.9304 (M+H)+; calc. for C76H120N2O4+H:
1125.9326%.
4.18. 3,7-Bis(4-decyloxyphenylethynyl)-1,5-
di(N,N-dioctylcarbamoyl)-2,6-dioxanthracene (16)
4.16. 4,10-Bis(4-(N,N-Dibutyl)phenyl)-bisthien[2,3-a,h]-
anthracene (13)
A 100 ml Schlenk flask was charged with 15 (80 mg,
0.071 mmol) and placed under argon. After the addi-
tion of CH2Cl2 (15 ml), the solution was stirred vigor-
ously as HBF4 (0.5 ml of a 40% solution in diethyl
ether, 3.63 mmol) was added dropwise. The reaction
stirred for 1 h at which point diethyl ether was added.
The intensely colored material that precipitated was
A 200 ml Schlenk flask was charged with 12 (205 mg,
0.294 mmol) and placed under argon. CH2Cl2 (100 ml)
was added and stirred vigorously as TfOH was added
dropwise (0.52 ml, 5.88 mmol). After 2 h, the reaction

222
J.D. To6ar, T.M. Swager / Journal of Organometallic Chemistry 653 (2002) 215–222
[2] K. Chmil, U. Scherf, Makromol. Chem. Rapid Commun. 14
(1993) 217.
[3] M.B. Goldfinger, T.M. Swager, J. Am. Chem. Soc. 116 (1994)
7895.
collected by filtration and washed with ether to provide
a fluffy burgundy solid product (75 mg, 0.57 mmol,
81%). H-NMR (300 MHz, CD3CN): 8.32 (s, 2H), 7.84
1
(d, 4H, J=8.7 Hz), 7.51 (s, 2H), 7.13 (d, 4H, J=9.0
Hz), 4.10 (m, 12H), 1.80 (m, 4H), 1.7–1.2 (bm, 76H),
0.89 (m, 18H). UV–vis (CHCl3) u (nm) (log m): 302
(4.40), 389 (4.74), 539 (3.79).
[4] J.D. Debad, A.J. Bard, J. Am. Chem. Soc. 120 (1998) 2476.
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(b) M.B. Goldfinger, K.B. Crawford, T.M. Swager, J. Org.
Chem. 63 (1998) 1668.
[6] V.S. Iyer, M. Wehmeier, J.D. Brand, M.A. Keegstra, K. Mu¨llen,
Angew. Chem. Int. Ed. Engl. 36 (1997) 1604.
[7] D.M. Bowles, G.J. Palmer, C.A. Landis, J.L. Scott, J.E. An-
thony, Tetrahedron 57 (2001) 3753.
Acknowledgements
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[15] (a) Q. Zhou, T.M. Swager, J. Am. Chem. Soc. 117 (1995) 12593;
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(1999) 1466;
The Army Research Office (through the Turnable
Optical Polymer System MURI project) provided gen-
erous financial support for this work. NSF and ONR
(TOPS-MURI) provided generous financial support for
this work. We thank Professor Keiki Kishikawa and
Dr. Jinsang Kim for supplying precursors to model
compound 15.
References
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