Synthesis of functionalized oligophenylenes and oligoarylenes bearing heteroaryl groups

Article abstract of DOI:10.1055/s-0028-1083260

Oligo-P-phenylenes have proven to be versatile building blocks for the generation of self-assembled nanoaggregates via vapour deposition on solid supports whose optical properties and morphologies can be influenced by the introduction of functional groups

Full text of DOI:10.1055/s-0028-1083260

PAPER
79
Synthesis of Functionalized Oligophenylenes and Oligoarylenes Bearing
Heteroaryl Groups
S
ynthesi
v
s
of oligoary
o
lenes nne Wallmann,a Gregor Schnakenburg,b Arne Lützen*a
a
Kekulé-Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
Fax +49(228)739608; E-mail: arne.luetzen@uni-bonn.de
b
Institute of Inorganic Chemistry, University of Bonn, Gerhard-Domagk-Str. 1, 53121 Bonn, Germany
Received 20 October 2008
where heteroaryls such as pyridines, thiophenes, and car-
bazoles have been incorporated into the oligoarylene
structures. Importantly, the heteroaryl groups are known
to have a marked influence on the opto(electric) properties
Abstract: Oligo-p-phenylenes have proven to be versatile building
blocks for the generation of self-assembled nanoaggregates via va-
pour deposition on solid supports whose optical properties and mor-
phologies can be influenced by the introduction of functional
groups. These aggregates show strong polarized luminescence and of p-conjugated materials,1,2 which might allow for the
they have been demonstrated to have wave-guiding, lasing and even
construction of electroluminescent devices in the future.
non-linear optical properties (e.g., frequency doubling) when the
molecular building blocks are suitably functionalized. Thus, there is
According to our previous reports, we again used Suzuki
cross-coupling reactions as reliable key steps in order to
achieve the synthesis of our target compounds by assem-
bling the oligoarylene scaffold from smaller building
blocks bearing the desired functional unit.
a demand for the synthesis of further functionalised p-phenylenes
because similar properties can be expected from derivatives incor-
porating heteroaryl groups in the oligoarylene scaffold such as
thiophenes, pyridines or carbazole units. The synthesis of such de-
rivatives using a reliable Suzuki cross-coupling strategy is present-
ed here.
Fortunately, most of the necessary building blocks that we
used for this purpose are commercially available. Other-
wise, they were prepared according to published proce-
dures.
Key words: p-conjugated
molecules,
oligo-p-phenylenes,
thiophenes, carbazoles, Suzuki cross-coupling
The first compound that was focussed on was p-terphenyl
3, decorated with a 4-pyridyl group. This compound was
synthesised in 57% yield by coupling 4-(4-iodophe-
nyl)pyridine (1)6 with 4-biphenylboronic acid (2) using
tetrakis(triphenylphosphine)palladium [Pd(PPh3)4] as cat-
alyst and caesium fluoride as base in tetrahydrofuran
(Scheme 1).
Materials built up from p-conjugated organic oligomers1
have recently seen an astonishing development due to
their interesting optical, electrical and optoelectrical prop-
erties.2 Among these, oligo-p-phenylenes have been
demonstrated to form interesting nanofibers upon vapour
deposition on suitable solid supports that are confined to
the submicron regime in two dimensions, and many ex-
hibit interesting optical properties.3
+
N
I
(HO)2B
[Pd(PPh3)4],
In order to influence the morphological and optical prop-
erties on demand, the introduction of functional groups
into the p-phenylene scaffold in a controlled manner has
been a valid approach.4 These functionalities do not
hinder the self-assembly growth and allow for fine tuning
of the materials’ linear and non-linear optical properties,
for example, the anisotropic blue luminescence with high
quantum yields, and the wave-guiding, lasing, and fre-
quency doubling properties.
1
2
CsF, THF,
57%
∆, 15 h
N
3
Scheme 1 Synthesis of (4-pyridyl)-[4,1¢:4¢,1¢¢]terphenyl (3)
Thus, there is a demand for the development of reliable
protocols for the synthesis of oligo-p-phenylenes. Recent-
ly, we reported on the successful preparation of symmet-
rically and non-symmetrically 1,4¢¢¢-disubstituted p-
quarterphenylenes and some 1-monofunctionalised deriv-
atives.5 Here, we present an extension of this work to in-
clude further examples carrying pentafluorophenyl units
and, especially, we describe a novel set of compounds
From our previous results, we assume that the growth pro-
cess of the fibres on suitable solid supports will allow
bulky substituents only in the free para-positions of the
oligo-p-phenylene scaffold because it is crucial that the
aryl units can adopt a coplanar arrangement. The only
substituent that has a size similar to a hydrogen atom and
might therefore be suitable for introduction into other po-
sitions is fluorine. Thus, we were also interested in the in-
corporation of pentafluorphenyl groups because this
group has a strong electron-withdrawing effect. Using our
protocol, we were able to prepare a first example (5),
SYNTHESIS 2009, No. 1, pp 0079–0084
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Advanced online publication: 12.12.2008
DOI: 10.1055/s-0028-1083260; Art ID: C04608SS
© Georg Thieme Verlag Stuttgart · New York

80
I. Wallmann et al.
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through coupling of boronic acid 2 with 1-iodo-4- col boronic acid ester 10 as described previously.5 The
pentafluorophenylbenzene7 (4) in 54% yield (Scheme 2).
product was subsequently coupled with either 2,5-dibro-
mothiophene or 5,5¢-bithiophene in order to obtain 14 and
13 in 60% and 48% yield, respectively. The use of the bo-
ronic acid ester proved to be essential for the success of
these transformations since the use of the respective bo-
ronic acid lead to a number of side products (mainly the
singly functionalised intermediate) in considerable
amounts. The side products turned out to have low solu-
bilities similar to the desired products and could therefore
not be removed from the doubly functionalised products.
Generally, oligoarylenes show very low solubility in com-
mon organic solvents, which makes them almost impossi-
ble to purify by column chromatography. Such
compounds usually precipitate from the reaction mixtures
and are purified by repeated washing with water and or-
ganic solvents (in some cases also trifluoroacetic acid).
Unfortunately, this method usually leads to retention of
residual solvents in the product, which cannot always be
removed upon drying under standard laboratory high vac-
uum (10–3 mbar). In order to isolate and purify compound
5, however, we found sublimation under ultrahigh vacu-
um (10–7 mbar) to be very convenient.
Cl
I
9
n-BuLi,
B(OMe3),
pinacol,
–78 °C
F
F
quant.
+
F
I
(HO)2B
2
4
O
O
[Pd(PPh3)4],
54% CsF, THF,
F
F
Cl
B
+
Br
∆, 48 h
S
n Br
10
F
F
F
n = 1 (11), n = 2 (12)
[Pd(PPh3)4],
CsF, THF,
∆, 40 h
48%
F
5
F
Scheme 2 Synthesis of 1-(pentafluorophenyl)-[4,1¢:4¢,1¢¢]-terphe-
nyl (5)
S
Cl
n
n = 1 (13, 60%), n = 2 (14, 48%)
We also synthesised a biphenyl analogue equipped with
two pentafluorophenyl moieties (8) by two-fold coupling
of commercially available pentafluorophenylboronic acid
(6) and 4,4¢-diiodobiphenyl (7). Since the reactivity of 6
was found to be very low under our standard conditions,
the addition of further activating Ag2O8 was found to be
crucial in order to obtain the desired product in an accept-
able yield of 56% (Scheme 3).
Cl
Scheme 4 Synthesis of 5,5¢-bis(4¢-chlorobiphenyl-4-yl)-2,2¢-bithio-
phene (14) and 2,5-bis(4¢-chlorobiphenyl-4-yl)thiophene (13) from 4-
chloro-4¢-iodobiphenyl (9)
Oligophenylenethiophenes 17 and 18, having only a sin-
gle phenylene unit attached to the thiophene rings, could
also be prepared. Therefore, we coupled commercially
available 4-chloro- and 4-methoxyphenylboronic acids 15
and 16 with dibromothiophenes 11 and 12 using 5 mol%
[Pd(PPh3)4] and CsF. This reaction gave 17 and 18 in 83
and 45% yield, respectively (Scheme 5).
F
F
+
I
F
B(OH)2
7
F
F
[Pd(PPh3)4],
CsF, THF,
∆, 3 d
6
Another interesting group of thiophenes are thiophenes
carrying naphthyl groups. Again we used our standard Su-
zuki cross-coupling conditions, [Pd(PPh3)4] as catalyst
56%
F
F
F
F
F
F
F
F
Br
OH
S
8
+
R
B
F
F
S
OH
Br
Scheme 3 Synthesis of 4,4¢-bis(pentafluorophenyl)biphenyl (8)
R = Cl (15), OMe (16)
12
[Pd(PPh3)4],
CsF, THF,
∆, 40 h
We then turned our attention to compounds that have het-
eroaryl groups in central, rather than terminal positions
within the oligoarylene structure. First we concentrated on
the incorporation of thiophene rings into the structures.
The synthesis of 5,5¢-bis(4¢-chlorobiphenyl-4-yl)-2,2¢-
bithiophene (14) and 2,5-bis(4¢-chlorobiphenyl-4-
yl)thiophene (13) is outlined in Scheme 4. 4-Chloro-4¢-io-
dobiphenyl (9) was transformed into the respective pina-
R
S
S
R
R = Cl (17, 83%), OMe (18, 45%)
Scheme 5 Synthesis of the phenylthiophenes 17 and 18
Synthesis 2009, No. 1, 79–84 © Thieme Stuttgart · New York

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Synthesis of Oligoarylenes
81
Boc
N
and CsF as base, to react dibromide 12 with commercially
available boronic acid 19 in tetrahydrofuran in order to
obtain 20 in a good yield of 79% (Scheme 6).
Br
Br
(HO)2B
[Pd(PPh3)4],
R
+
Br
OMe
24
S
R = H (25), Cl (15)
+
2
CsF, THF
∆, 46 h
S
(HO)2B
Br
19
12
Boc
N
[Pd(PPh3)4],
CsF, THF,
∆, 48 h
79%
R
R
in situ deprotection
MeO
S
S
OMe
H
20
N
R
R
Scheme 6 Synthesis of 5,5¢-bis(6-methoxynaphthalene-2-yl)-2,2¢-
bithiophene (20)
R = H (26, 73%), Cl (27, 70%)
Furthermore, we were able to synthesize 2,2¢-(6-methoxy-
naphthalene-2-yl)thiophene (23) by coupling thiophene-
2,5-diboronic acid (21) with 2-bromo-6-methoxynaphtha-
lene (22). It should be noted, however, that a mixture of
toluene, methanol, and water had to be used in this case in
order to ensure enough solubility of boronic acid 21 to
achieve a successful transformation. As a result, the base
was changed to potassium carbonate in order to adapt to
these conditions. Thus, we used potassium carbonate in
this case to obtain 23 in a moderate yield of 43%
(Scheme 7).
Scheme 8 Synthesis of phenylcarbazoles 26 and 27
Figure 1 X-ray crystal structure analysis of phenylcarbazole 26
(HO)2B
OMe
S
ray diffraction by repeated crystallisation from DMF. The
result of this analysis is shown in Figure 1, which demon-
strates the packing of the slightly curved individual mole-
cules within the crystal lattice.
+
2
B(OH)2
Br
22
21
[Pd(PPh3)4],
K2CO3, THF,
∆, 48 h
43%
In conclusion, we have developed a reliable protocol for
the synthesis of oligo-p-phenylenes using Suzuki cross-
coupling reactions. The synthesis could be extended to the
preparation of derivatives with heteroaryl functions either
in the centre or on the periphery of the oligoarylene scaf-
fold. These procedures allow the isolation of the target
compounds in sufficient purity to perform vapour deposi-
tion studies. These compounds are promising candidates
for the formation of well-defined nanoaggregates with in-
teresting opto(electrical) properties.
S
OMe
23
MeO
Scheme 7 Synthesis of 2,5-(6-methoxynaphthalene-2-yl)thiophene
(23)
Finally, we focused on another important class of het-
eroaryls for our purposes – the carbazoles. To this end, we
first prepared the known dibromide 24 in three steps.9
Compound 24 was then subjected to two-fold Suzuki
cross-couplings with commercially available phenylbo-
ronic acids 25 and 15. The carbazoles were deprotected in
situ and recrystallised from DMF to give the desired prod-
ucts 26 and 27 in yields of 73% and 70%, respectively
(Scheme 8).
Solvents were dried, distilled and stored under argon according to
standard procedures. Reactions with air- and moisture-sensitive
transition-metal compounds were performed under an argon atmo-
sphere in oven-dried glassware using standard Schlenk techniques.
Thin-layer chromatography was performed on aluminium TLC
plates (silica gel 60 F254) from Merck and the products were visu-
alized under UV-light (254 or 366 nm). Products were purified ei-
ther by column chromatography on silica gel 60 (70–230 mesh or
230–400 mesh) from Merck, by extraction and washing procedures,
or by sublimation under ultrahigh vacuum.
Compound 26 has been described before by Simpson and
co-workers,10 though it was synthesised through a differ-
ent route and used for a different purpose. We were able
to grow single crystals of this compound suitable for X-
1H and 13C NMR spectra were recorded at 298 K on a Bruker AM
400 spectrometer operating at 400.1 MHz and 100.6 MHz, respec-
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82
I. Wallmann et al.
PAPER
tively. Because of the low solubility of the compounds it was not
possible to record 1H and 13C NMR spectra that showed all the ex-
pected resonances for most of the compounds; therefore, these are
not listed here. Mass spectra were recorded on a Finnigan MAT-
95XL. UV/Vis spectra were measured on a Jena Analytic Specord
200 spectrometer in a 1 cm quartz cuvette. Fluorescence spectra
were measured on an Aminco Bowman AB2 spectrometer in a 1 cm
quartz cuvette. Elemental analyses were carried out with a Heraeus
Vario EL instrument. Since the products were obtained as amor-
phous solids, they usually contain residual amounts of solvents
from the extraction and washing procedure that could not be re-
moved completely in all cases even after heating for longer periods
of time under standard laboratory high vacuum (10–3 mbar). In these
cases, detailed analyses are not listed here. However, we give
HRMS data in all cases.
2 mmol, 2 equiv), Pd(PPh3)4 (115 mg, 0.05 mmol, 10 mol%), and
Ag2O (279 mg, 1.2 mmol, 1.2 equiv). THF (20 mL) was added and
the reaction mixture was refluxed for 3 d. After allowing to cool to
r.t., CH2Cl2 was added to the reaction mixture, which was then fil-
tered through Celite. The residue was extracted with EtOAc (×3),
dried over MgSO4 and the solvent was removed under reduced pres-
sure to give 8.
Yield: 243 mg (56%); white amorphous solid.
MS (EI): m/z (%) = 486.0 (100) [M+].
HRMS (EI): m/z calcd for C24H8F10: 486.0466; found: 486.0468.
UV/Vis (CH2Cl2): lmax = 381 nm.
Fluorescence (CH2Cl2): lmax = 351 nm.
4-(4¢-Chlorobiphenyl-4-yl)-4,4,5,5-tetramethyl-1,3,2-dioxa-
borolane (10)
4-Chlorophenylboronic acid (15), phenylboronic acid (25), 4-meth-
oxyphenylboronic acid (16), pentafluorophenylboronic acid (6),
5,5¢-dibromo-2,2¢-bithiophene (12), 2,5-dibromothiophene (11),
thiophene-2,5-diboronic acid (21), 2-methoxy-6-naphthylboronic
acid (19), 2-bromo-6-methoxynaphthalene (22), 4-biphenyl dibo-
ronic acid (2), silver(I) oxide, 4-iodobiphenyl (7), CsF, and
Pd(PPh3)4 were purchased from Sigma–Aldrich, Alfa Aesar,
Merck, Lancaster or Strem, and used as received. 4-Chloro-4¢-
iodobiphenyl5 (9), 4-iodo-4¢-(pentafluorophenyl)benzene7 (4), 4-
(4¢-iodophenyl)pyridine6 (1), and Boc-protected 2,7-dibromo-
carbazole9 (24), were prepared according to published procedures.
A two-neck flask equipped with a condenser was charged with 4-
chloro-4¢-iodobiphenyl (9; 261 mg, 0.83 mmol) and Et2O (15 mL).
Under an argon atmosphere, n-BuLi (1.6 M in hexane, 1.29 mL,
1.31 mmol, 1.2 equiv) was added dropwise at –78 °C. After 30 min,
trimethylborate (0.82 mL, 0.99 mmol, 1.2 equiv) was added at this
temperature. The reaction mixture was allowed to warm to r.t. and
stirred for a further 3 h before pinacol (128 mg, 1.08 mmol, 1.3
equiv) was added. After 10 min, glacial AcOH (1 mL) was added
and stirring was continued for 8 h. The reaction mixture was filtered
over Celite and the residue was extracted repeatedly with CH2Cl2–
EtOH (3:1; 3 × 20 mL). Subsequent removal of the solvents under
reduced pressure gave the crude product that was finally washed
with acetone to give 10.
4-Pyridyl[4,1¢:4¢,1¢¢]terphenyl (3)
A two-neck flask equipped with a condenser was charged with 4-(4-
iodophenyl)pyridine (1; 250 mg, 0.89 mmol, 1 equiv), 4-biphenyl-
boronic acid (2; 185 mg, 0.93 mmol, 1.05 equiv), CsF (406 mg, 2.67
mmol, 3 equiv), and Pd(PPh3)4 (31 mg, 0.027 mmol, 3 mol%). THF
(40 mL) was added and the reaction mixture was refluxed for 15 h.
After allowing to cool to r.t., the precipitate was collected and
washed with THF, CH2Cl2, and H2O (2 × 40 mL each) to give 3.
Yield: 261 mg (quant.); slightly brownish amorphous solid.
MS (EI): m/z (%) = 486.0 (100) [M+].
HRMS (EI): m/z calcd for C18H20BClO2: 314.1245; found:
314.1244.
1H NMR (400 MHz, CDCl3): d = 7.85–7.89 (m, 2 H, ArH), 7.50–
7.65 (m, 4 H, ArH), 7.38–7.43 (m, 2 H, ArH), 1.36 (s, 12 H, 4 ×
CH3).
Yield: 155 mg (57%); grey amorphous solid.
MS (EI): m/z (%) = 307.1 (100) [M+].
HRMS (EI): m/z calcd for C23H17N: 307.1361; found: 307.1365.
13C NMR (100 MHz, CDCl3): d = 142.6, 139.4 (2 × Cq), 135.3 (3 ×
CAr), 133.6 (Cq), 128.9, 128.4 (4 × CAr), 126.2 (2 × CAr), 83.9
[C(CH3)2], 24.9 (4 × CH3).
Anal. Calcd for C23H17N·0.25 CH2Cl2: C, 84.98; H, 5.37; S, 4.26.
Found: C, 85.36; H, 5.37; S, 4.23.
UV/Vis (CH2Cl2): lmax = 303 nm.
2,5-Bis(4¢-chlorobiphenyl-4-yl)thiophene (13)
Fluorescence (CH2Cl2): lmax = 383 nm.
A two-neck flask equipped with a condenser was charged with 2,5-
dibromothiophene (308 mg, 1.27 mmol, 1 equiv), 2-(4¢-chlorobi-
phenyl-4-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (10; 800 mg,
2.54 mmol, 2 equiv), CsF (579 mg, 3.81 mmol, 3 equiv), and
Pd(PPh3)4 (74 mg, 0.064 mmol, 5 mol%). THF (50 mL) was added
and the reaction mixture was refluxed for 48 h. After allowing to
cool to r.t., the precipitate was collected and washed with THF,
CH2Cl2, and H2O (2 × 25 mL each) to give 13.
4-Pentafluorophenyl[4,1¢:4¢,1¢¢]terphenyl (5)
A two-neck flask equipped with a condenser was charged with 1-
iodo-4-(pentafluorophenyl)benzene (4; 859 mg, 2.32 mmol, 1
equiv), 4-biphenylboronic acid (2; 482 mg, 2.44 mmol, 1.05 equiv),
CsF (1.06 g, 6.96 mmol, 3 equiv), and Pd(PPh3)4 (80 mg, 0.07
mmol, 3 mol%). THF (80 mL) was added and the reaction mixture
was refluxed for 46 h. After allowing to cool to r.t., the precipitate
was collected and washed with THF, CH2Cl2, and H2O (2 × 40 mL
each). The crude product was sublimed under ultrahigh vacuum
(10–7 mbar) to give the product 5.
Yield: 348 mg (60%); yellow amorphous solid.
MS (EI): m/z (%) = 456.0 (100) [M+].
HRMS (EI): m/z calcd for C28H18Cl2S: 456.0506; found: 456.0508.
Yield: 497 mg (54%); white crystalline needles.
MS (EI): m/z (%) = 396.1 (100) [M+].
Anal. Calcd for C28H18Cl2S·0.5 H2O: C, 72.10; H, 4.11; S, 6.87.
Found: C, 71.62; H, 3.97; S, 6.75.
UV/Vis (CH2Cl2): lmax = 352 nm.
HRMS (EI): m/z calcd for C24H13F5: 396.0937; found: 396.0940.
UV/Vis (CH2Cl2): lmax = 293 nm.
Fluorescence (CH2Cl2): lmax = 414, 435 nm.
Fluorescence (CH2Cl2): lmax = 365 nm.
5,5¢-Bis(4¢-chlorobiphenyl-4-yl)-2,2¢-bithiophene (14)
A two-neck flask equipped with a condenser was charged with 2-
(4¢-chlorobiphenyl-4-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane
(10; 208 mg, 0.66 mmol, 1 equiv), 5,5¢-dibromo-2,2¢-bithiophene
(12; 102 mg, 0.314 mmol, 2.1 equiv), CsF (143 mg, 0.942 mmol, 3
4,4¢-Bis(pentafluorophenyl)biphenyl (8)
A two-neck flask equipped with a condenser was charged with pen-
tafluorophenyl boronic acid (6; 434 mg, 2.05 mmol, 2.05 equiv),
4,4¢-diiodobiphenyl (7; 406 mg, 1.0 mmol, 1 equiv), CsF (303 mg,
Synthesis 2009, No. 1, 79–84 © Thieme Stuttgart · New York

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Synthesis of Oligoarylenes
83
equiv), and Pd(PPh3)4 (18 mg, 0.016 mmol, 5 mol%). THF (30 mL)
was added and the reaction mixture was refluxed for 40 h. After al-
lowing to cool to r.t. the precipitate was collected and washed with
THF, CH2Cl2, and H2O (2 × 25 mL each) to give 14.
Fluorescence (CH2Cl2): lmax = 411, 435, 456 nm.
2,5-(6-Methoxynaphthalene-2-yl)thiophene (23)
A two-neck flask equipped with a condenser was charged with
thiophene-2,5-diboronic acid (21; 500 mg, 2.91 mmol, 1 equiv), 2-
bromo-6-methoxynaphthalene (22; 1.45 g, 6.11 mmol, 2.1 equiv),
K2CO3 (1.21 g, 8.73 mmol, 3 equiv), and Pd(PPh3)4 (168 mg, 0.15
mmol, 5 mol%). A mixture of toluene (60 mL), MeOH (30 mL) and
H2O (3 mL) was added and the reaction mixture was refluxed for 48
h. After allowing to cool to r.t., the precipitate was collected and
washed with toluene, CH2Cl2, and H2O (2 × 50 mL each) to give 23.
Yield: 82 mg (48%); yellow amorphous solid.
MS (EI): m/z (%) = 538.0 (100) [M+].
HRMS (EI): m/z calcd for C32H20Cl2S2: 538.0383; found: 538.0381.
Anal. Calcd for C32H20Cl2S2·0.5 CH2Cl2: C, 67.07; H, 3.64; S,
11.02. Found: C, 67.23; H, 3.58; S, 11.00.
UV/Vis (CH2Cl2): lmax = 396 nm.
Yield: 500 mg (43%); yellow amorphous solid.
MS (EI): m/z (%) = 396.1 (100) [M+].
Fluorescence (CH2Cl2): lmax = 377, 456, 483 nm.
HRMS (EI): m/z calcd for C26H20O2S: 396.1184; found: 396.1186.
5,5¢-Bis(4-chlorophenyl)-2,2¢-bithiophene (17)
A two-neck flask equipped with a condenser was charged with 5,5¢-
dibromo-2,2¢-bithiophene (12; 480 mg, 1.48 mmol, 1 equiv), 2-(4¢-
chlorobiphenyl-4-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (10;
486 mg, 3.11 mmol, 2.1 equiv), CsF (674 mg, 4.44 mmol, 3 equiv),
and Pd(PPh3)4 (86 mg, 0.074 mmol, 5 mol%). THF (50 mL) was
added and the reaction mixture was refluxed for 48 h. After allow-
ing to cool to r.t., the precipitate was collected and washed with
THF, CH2Cl2, and H2O (2 × 35 mL each) to give 17.
Anal. Calcd for C26H20O2S·0.5 H2O: C, 77.07; H, 5.01; S, 8.38.
Found: C, 77.01; H, 5.22; S, 7.91.
UV/Vis (CH2Cl2): lmax = 362 nm.
Fluorescence (CH2Cl2): lmax = 411, 432 nm.
Synthesis of Carbazoles; General Procedure (GP 1)
A two-neck flask equipped with a condenser was charged with Boc-
protected 9H-carbazole 24 (1 equiv), a phenylboronic acid (2.05
equiv), CsF (3 equiv), and Pd(PPh3)4 (3 mol%). THF (50 mL) was
added and the reaction mixture was refluxed for 46 h. After allow-
ing to cool to r.t., the solution was diluted with CH2Cl2 (30 mL) and
washed with H2O (3 × 40 mL). The organic phase was concentrated
and dried in vacuo. The resulting Boc-protected product was sus-
pended in CH2Cl2 (30 mL), cooled to 0 °C and TFA (5 mL) was
added dropwise. The reaction mixture was allowed to warm to r.t.
and then stirred for 1 h. The solution was made basic by dropwise
addition of concd aq NaOH, which resulted in the formation of a vo-
luminous white precipitate. The crude product was collected by fil-
tration and washed repeatedly with H2O and CH2Cl2 (2 × 20 mL
each). Recrysallisation from DMF gave the desired carbazole.
Yield: 474 mg (83%); slightly yellow amorphous solid.
MS (EI): m/z (%) = 386.0 (100) [M+].
HRMS (EI): m/z calcd for C20H12Cl2S2: 385.9757; found: 385.9754.
Anal. Calcd for 3 C20H12Cl2S2·4 CH2Cl2·H2O: C, 51.19; H, 2.95; S,
12.81. Found: C, 51.54; H, 2.795; S, 12.58.
UV/Vis (CH2Cl2): lmax = 381 nm.
Fluorescence (CH2Cl2): lmax = 444, 468 nm.
5,5¢-Bis(4-dimethoxyphenyl)-2,2¢-bithiophene (18)
A two-neck flask equipped with a condenser was charged with 5,5¢-
dibromo-2,2¢-bithiophene (12; 465 mg, 1.44 mmol, 1 equiv), 4-
methoxyphenylboronic acid (16; 458 mg, 3.02 mmol, 2.1 equiv),
CsF (656 mg, 4.32 mmol, 3 equiv), and Pd(PPh3)4 (83 mg, 0.072
mmol, 5 mol%). THF (50 mL) was added and the reaction mixture
was refluxed for 48 h. After allowing to cool to r.t., the precipitate
was collected and washed with THF, CH2Cl2, and H2O (2 × 35 mL
each) to give 18.
2,7-Diphenyl-9H-carbazole (26)
Boc-protected 9H-carbazole 24 (500 mg, 1.17 mmol), phenylboron-
ic acid 25 (291 mg, 2.39 mmol), CsF (533 mg, 3.51 mmol), and
Pd(PPh3)4 (41 mg, 0.035 mmol) reacted according to GP 1 to afford
26. Analytical data were in accordance with literature data.10
Yield: 272 mg (73%); white crystalline needles.
MS (EI): m/z (%) = 319.1 (100) [M+].
Yield: 247 mg (45%); slightly yellow amorphous solid.
MS (EI): m/z (%) = 378.1 (100) [M+].
HRMS (EI): m/z calcd for C24H17N: 319.1361; found: 319.1363.
UV/Vis (CH2Cl2): lmax = 320 nm.
HRMS (EI): m/z calcd for C22H18O2S2: 378.0748; found: 378.0744.
Anal. Calcd for C22H18O2S2·0.25 CH2Cl2·0.25 H2O: C, 68.19; H,
4.94; S, 16.55. Found: C, 68.25; H, 4.73; S, 16.51.
Fluorescence (CH2Cl2): lmax = 384 nm.
UV/Vis (CH2Cl2): lmax = 382 nm.
X-ray crystal data for 26: Empirical formula: C24H17N; Formula
weight: 319.39; Unit cell dimensions: a = 7.5147(9) Å,
b = 6.7446(5) Å, c = 36.382(4) Å, a = 90°, b = 95.684(10)°,
g = 90°; V = 1562.9(3) Å3; Z = 4; rcalcd = 1.357 Mg·m–3; Crystal sys-
tem = monoclinic; space group P21/c. Data were collected on a Stoe
IPDS 2T diffractometer equipped with a low-temperature device
(Cryostream, Oxford Cryosystems) at 123(2) K using graphite
monochromated Mo-Ka radiation (l = 0.71073 Å). Programs used:
data collection COLLECT (Nonius B.V., 1998), data reduction
Fluorescence (CH2Cl2): lmax = 432, 454 nm.
5,5¢-Bis(6-methoxynaphthalene-2-yl)-2,2¢-bithiophene (20)
A two-neck flask equipped with a condenser was charged with 5,5¢-
dibromo-2,2¢-bithiophene (12; 1.14 g, 3.52 mmol, 1 equiv), 2-meth-
oxy-6-naphthylboronic acid (19; 1.5 g, 7.39 mmol, 2.1 equiv), CsF
(1.61 g, 10.62 mmol, 3 equiv), and Pd(PPh3)4 (203 mg, 0.176 mmol,
5 mol%). THF (50 mL) was added and the reaction mixture was re-
fluxed for 48 h. After allowing to cool to r.t., the precipitate was col-
lected and washed with THF, CH2Cl2, and H2O (2 × 50 mL each) to
give 20.
Denzo-SMN,11
absorption
correction
Denzo.12
Crystal
dimensions = 0.47 × 0.24 × 0.11 mm; F(000) = 372, Qmax = 29°,
–10 < h < 8; –7 < k < 7; –49 < l < 49; 12736 measured reflections,
4136 independent reflections (Rint = 0.0906), m = 0.078 mm–1;
max. and min. transmission: 0.9915 and 0.9639. The structures
were solved by direct methods (SHELXS-97) and refined by full-
matrix least squares on F2 (SHELXL-97).13 All non-hydrogens
were refined anisotropically. Hydrogen atoms at carbon were
placed in calculated positions and refined isotropically using a
Yield: 1.34 g (79%); yellow amorphous solid.
MS (EI): m/z (%) = 478.1 (100) [M+].
HRMS (EI): m/z calcd for C30H22O2S2: 478.1061; found: 478.1068.
UV/Vis (CH2Cl2): lmax = 224 nm.
Synthesis 2009, No. 1, 79–84 © Thieme Stuttgart · New York

84
I. Wallmann et al.
PAPER
riding model. 4136 reflections I > 2s(I) and 295 refined parameters;
GOF(F2) = 0.534; final R indices: R1 = 0.0335, wR2 = 0.0440;
max./min. residual electron density 0.130 and –0.143 eÅ3.
(2) Some recent books: (a) Müllen, K.; Wegner, G. Electronic
Materials: The Oligomer Approach; Wiley-VCH:
Weinheim, 1998. (b) Fichou, D. Handbook of Oligo- and
Polythiophenes; Wiley-VCH: Weinheim, 1999. (c) Nalva,
H. S. Handbook of Advanced Electronic and Photonic
Materials and Devices; Academic Press: San Diego, 2000.
(d) Müllen, K.; Scherf, U. Organic Light Emitting Devices –
Synthesis, Properties and Applications; Wiley-VCH:
Weinheim, 2006. (e) Klauk, H. Organic Electronics – An
Industrial Perspective; Wiley-VCH: Weinheim, 2006.
(f) Müller, T. J. J.; Bunz, U. H. F. Functional Organic
Materials; Wiley-VCH: Weinheim, 2007.
(3) Organic Nanostructures for Next Generation Devices; Al-
Shamery, K.; Rubahn, H.-G.; Sitter, H., Eds.; Springer:
Berlin, 2008.
(4) (a) Schiek, M.; Balzer, F.; Al-Shamery, K.; Brewer, J.;
Lützen, A.; Rubahn, H.-G. Small 2008, 4, 176. (b) Schiek,
M.; Balzer, F.; Al-Shamery, K.; Lützen, A.; Rubahn, H.-G.
Soft Matter 2008, 4, 277.
CCDC-705361 contains the supplementary data for this structure.
These data can be obtained free of charge via www.ccdc.cam.ac.uk/
data_request/cif, or by emailing: data_request@ccdc.cam.ac.uk, or
by contacting The Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB2 1EZ, UK; fax: +44(1223)336033.
2,7 Bis(4-chlorophenyl)-9H-carbazole (27)
Boc-protected 9H-carbazole 24 (500 mg, 1.17 mmol), 4-chlorophe-
nylboronic acid (15; 415 mg, 2.39 mmol), CsF (533 mg, 3.51
mmol), and Pd(PPh3)4 (41 mg, 0.035 mmol) reacted according to
GP 1 to afford 27.
Yield: 323 mg (70%); slightly off-white crystalline needles.
1H NMR: (400 MHz, DMSO-d6): d = 11.44 (s, 1 H, NH), 8.21 (d,
3J = 8.16 Hz, 2 H, ArH), 7.76–7.79 (m, 4 H, ArH.), 7.74 (d,
4J = 1.34 Hz, 2 H, ArH), 7.52–7.56 (m, 4 H, ArH), 7.47 (dd,
3J = 8.16 Hz, 4J = 1.34 Hz, 2 H, ArH).
(5) (a) Schiek, M.; Al-Shamery, K.; Lützen, A. Synthesis 2007,
613. (b) Wallmann, I.; Schiek, M.; Koch, R.; Lützen, A.
Synthesis 2008, 2446.
MS (EI): m/z = 387.0 (100) [M+].
HRMS (EI): m/z calcd for C24H15Cl2N: 387.0582; found: 387.0579.
UV/Vis (CH2Cl2): lmax = 322 nm.
(6) Khlobystov, A. N.; Brett, M. T.; Blake, A. J.; Champness, N.
R.; Gill, P. M. W.; O’Neill, D. P.; Teat, S. J.; Wilson, C.;
Schröder, M. J. Am. Chem. Soc. 2003, 125, 6753.
(7) Frohn, H. J.; Klose, A. J. Fluorine Chem. 1993, 64, 201.
(8) Korenga, T.; Kosaki, T.; Fukumura, R.; Ema, T.; Sakai, T.
Org. Lett. 2005, 7, 4915.
(9) (a) Freeman, A. W.; Urvoy, M.; Criswell, M. E. J. Org.
Chem. 2005, 70, 5014. (b) Moon, K.-S.; Kim, H.-J.; Lee, M.
Angew. Chem. Int. Ed. 2007, 46, 6807.
Fluorescence (CH2Cl2): lmax = 315 nm.
Acknowledgment
Financial support from the DFG is gratefully acknowledged.
(10) Simpson, E.; Daup, H.; Hayes, F. N. J. Org. Chem. 1973, 38,
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Synthesis 2009, No. 1, 79–84 © Thieme Stuttgart · New York