Preparation and photoluminescence of p-terphenyl derivatives containing cyano groups

Article abstract of DOI:10.1016/j.tet.2005.03.030

Fifteen p-terphenyls containing alkoxylated backbones with and without cyano groups on the phenyl moieties have been designed and synthesized. The influences of the position and the number of cyano groups on the phenyl moieties as well as the skeleton to

Full text of DOI:10.1016/j.tet.2005.03.030

Tetrahedron 61 (2005) 4735–4741
Preparation and photoluminescence of p-terphenyl derivatives
containing cyano groups
Chien-Jung Jack Wu,a Cuihua Xue,b Yang-Ming Kuoa and Fen-Tair Luob,
*
aInstitute of Applied Chemistry, Chinese Culture University, Taipei 111, Taiwan
bInstitute of Chemistry, Academia Sinica, Nankang, Taipei 115, Taiwan
Received 24 January 2005; revised 6 March 2005; accepted 8 March 2005
Available online 24 March 2005
Abstract—Fifteen p-terphenyls containing alkoxylated backbones with and without cyano groups on the phenyl moieties have been
designed and synthesized. The influences of the position and the number of cyano groups on the phenyl moieties as well as the skeleton to the
absorption and emission spectra both, in solution and in solid state of these new p-terphenyls are discussed.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
efficiency in LED devices even using stable aluminum
electrodes.4 However, despite its interesting properties in
this field, as to our knowledge, there is no report in the
literature about the synthesis of the p-terphenyls with or
without cyano groups on the phenylene moieties. The aryl–
aryl bond formation has been known for more than a century
and was one of the first reaction using a transition metal.5
Over the last ten years many articles have dealt with new
results in the area of aryl–aryl bond formation. Nowadays,
many more syntheses use palladium catalysts than their
nickel and copper counterparts. As to our knowledge, the
palladium-catalyzed Stille,6 Suzuki,7 Negishi,8 and
Kumada9 reaction have been the most studied over the
past few years. We have focused on the Suzuki coupling, a
palladium(0)-catalyzed carbon–carbon bond-forming reac-
tion between an organohalide and an organoboron reagent,
in the a-arylation or a-vinylation of N,N-dimethylacetamide
recently.10,11 Since the boron reagents are compatible with a
large number of functional groups and tolerate cyanides,
thus fulfilling our goals for synthetic flexibility. Herein, we
report the efficient synthesis of a series of p-terphenyl with
and without cyano groups 1–10 and their photoluminescent
behavior. As for comparison, we also synthesized
p-terphenyl derivatives with cyano groups on the central
benzene ring and p-terphenyl with hexahexyloxyl groups
11–15 (Scheme 1).
Recently, we have reported a series of distyrylbenzene
(DSB) derivatives, as the oligomeric analogue of poly-para-
phenylene-vinylene (PPV), which was assessed as the
emitter in organic light emitting diode (OLED) fabrication.1
The presence of electron-withdrawing cyano group at
various positions in the molecule may influence on the
photophysical property and the electroluminescent behavior
of these derivatives in OLED. Thus, bright blue emissions
were achieved with these materials, as a dopant, in the
device structure of ITO/NPB/CBP/TPBI:DSB/TPBI/
Mg:Ag.1 Although there were not much difference in the
absorption and emission spectra of the analogues com-
pounds containing n-hexyloxy and 2-ethylhexyloxy groups.
However, 2-ethylhexyloxy groups could produce more
saturated blue color in their EL. Our preliminary results
from ZINDO calculations2 on p-terphenyls with or without
cyano groups on the phenylene moieties showed that para-
or meta-substituted cyano groups on the peripheral rings
could cause red shifts in the absorption spectra. The
presence of the alkoxy unit should enhance the solubility
of oligomers and the introduction of high electron affinity of
cyano groups to oligo-para-phenylene-vinylene (OPV)
derivatives has been reported to lower the energy of the
LUMO and reduces the barrier to the electron injection in
LED.3 Thus, PPV derivatives containing cyano groups
could present high electron affinity and therefore exhibit a
relatively low threshold voltage and high quantum
2. Results and discussion
Keywords: Suzuki–Miyaura reaction; p-Terphenyl containing cyano
groups; Photoluminescence.
The Suzuki cross-coupling reaction to form p-terphenyls
with or without cyano groups were shown in Scheme 1.
Thus, the palladium-catalyzed cross-coupling reaction of
*
Corresponding author. Tel.: C886 2 27898576; fax: C886 2 27888199;
e-mail: luoft@chem.sinica.edu.tw
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.03.030

4736
C.-J. J. Wu et al. / Tetrahedron 61 (2005) 4735–4741
Scheme 1. Synthesis of a series of p-terphenyl with or without cyano groups.
2,5-dihexyloxy-1,4-benzenediboronic acid (16), prepared in
79% yield from the lithium–halogen exchange reaction of
2,5-dibromo-1,4-dihexyloxybenzene with n-butyllithium
followed by the treatment of trimethylborate and dilute
acid, with 2.5 equiv of bromoarene with or without cyano
groups at ortho-, meta-, para-, or two meta-positions in the
presence K2CO3 as the base in DMSO could give
p-terphenyls 1–5 in fair to good yields (70 to 78%). Under
the similar reaction conditions, the cross-coupling reaction
of 2,5-dibromo-1,4-dihexyloxybenzene with arylboronic
acid with or without cyano groups gave 1–5 in low yields
(33 to 42%). Likewise, 2-(2-ethylhexyloxy)-5-methoxy-1,4-
benzenediboronic acid (17) could give the corresponding
p-terphenyls 6–10 in fair to good yields (60 to 85%). 2,5-
Dibromo-3,6-dihexyloxybenzene-1,4-dicarbonitrile (18)
and 2,5-dibromo-6-(2-ethylhexyloxy)-3-methoxybenzene-
1,4-dicarbonitrile (19) could undergo Suzuki coupling
reaction with 2.5 equiv of phenylboronic acid to give
p-terphenyls 11 and 12 with cyano groups on the central
benzene ring in 87 and 88% yields, respectively. The
coupling of 18 and 19 with phenylboronic acid with cyano
groups on the phenyl rings, prepared from lithium–halogen
exchange of cyano-substituted bromobenzene and n-butyl-
lithium at K78 8C in THF followed by the addition of
trimethylborate, gave very low yields. However, the
palladium-catalyzed cross-coupling reaction of 2.5 equiv
of 4,4,5,5-tetramethyl-2-(4-cyanophenyl)-1,3,2-dioxaboro-
lane (20) with 18 and 19 could give p-terphenyls 13–14 with
two cyano groups on the central benzene ring and two cyano
groups at the para-positions of the peripheral rings in 75 and
73% yields, respectively. The use of PdCl2(dppf) as the
catalyst and K3PO4 as the base could give better yields than

C.-J. J. Wu et al. / Tetrahedron 61 (2005) 4735–4741
4737
Table 1. UV spectral data of symmetric and asymmetric p-terphenyls
dihexyloxybenzenecarbonitrile in the presence of various
palladium catalysts and bases failed.
Compound
UVa lmax
(nm)
UVb lmax
(nm)
3a!103 dm3 molK1 cmK1
Tables 1 and 2 showed the lmax of their UV, PL, and EX
spectral data along with the extinction coefficiency and the
fluorescent quantum yield, FF, of p-terphenyls 1–14 both in
ethyl acetate solution and in their solid states. In general, the
extinction coefficiencies of UV spectra in solution for
p-terphenyls without cyano groups on the central benzene
ring (1–10) are higher for asymmetric p-terphenyls (6–10)
containing 2-ethylhexyloxy and methoxy groups than the
corresponding symmetric p-terphenyls (1–5) containing two
n-hexyloxy groups. The lower extinction coefficiency (a
measure of transition probability or allowedness of an
electronic transition at a given wavelength) for 1–5 may be
due to their bigger steric hindrance than that for the
corresponding 6–10.12 Since one of the n-hexyloxy group in
1–5 is a little bigger than the corresponding methoxy group
in 6–10 so that the three phenyl groups tend to be non-
coplanar in 1–5, while the three phenyl groups are relatively
not so non-coplanar in 6–10.13 That means that there is a
bigger structure change in the excited states from the ground
states for 1–5 than that for 6–10. So, the transition
probability for 6–10 is higher than that of 1–5. In other
words, the extinction coefficiencies for 6–10 is relatively
higher than that for 1–5. On the contrary, the extinction
coefficiencies of UV spectra for p-terphenyls with cyano
groups on the central benzene ring (11–14) is lower for
asymmetric p-terphenyls (12 and 14) than the corresponding
symmetric p-terphenyls (11 and 13). For p-terphenyls 1–14,
the lmax in both UV absorption and PL emission spectra in
solution shows a red shift (2 to 6 nm) for symmetric
1
2
3
4
5
6
7
8
320
331
332
346
344
318
327
329
342
345
341
336
337
336
357
372
337
383
361
320
335
346
368
356
355
349
347
347
7.96
2.20
7.55
8.81
7.98
10.22
9.38
12.32
9.62
8.96
9.61
6.61
11.95
8.88
9
10
11
12
13
14
a The UV spectra in ethyl acetate solution.
b The UV spectra in solid state.
the use of other kinds of catalysts (Pd(PPh3)4, Pd(PPh3)2Cl2)
and bases (K2CO3, CsF, Cs2CO3, i-Pr2NEt) in the case of
coupling 1,3,2-dioxaborolane with 18 and 19. Attempts to
prepare 3,6-dicyano-2,5-dihexyloxy-1,4-benzenediboronic
acid from 18 by lithium–halogen exchange at low
temperature and followed by the addition of trimethylborate
gave only debrominated product, 2,5-dihexyloxybenzene-
1,4-dicarbonitrile, in 70% yield. The palladium-catalyzed
cross-coupling reaction of 16 with 2.5 equiv of 2-bromo-
1,4-dihexyloxy-benzene (21), prepared in 86% yield by
mono-lithium–halogen exchange of 2,5-dibromo-1,4-
dihexyloxybenzene with n-butyllithium followed by acidic
hydrolysis, gave p-terphenyl 15 with hexahexyloxyl groups.
Attempts
to
couple
16
with
4-bromo-2,5-
Table 2. PL and EX spectral data of symmetric and asymmetric p-terphenyls
PLa lmax (nm)
PLb lmax (nm)
EXa lmax (nm)
EXb lmax (nm)
FF
a,c
Compound
385
384
319
277
330
274
331
278
344
290
347
280
321
277
328
276
333
279
344
288
341
280
338
278
337
279
339
279
335
277
329
283
344
244
332
268
358
294
351
281
323
281
344
259
344
270
360
291
353
284
348
265
344
284
342
268
339
259
0.530
1
413
402
424
419
381
408
399
420
422
419
413
431
430
403
411
420
452
397
401
415
418
448
402
394
409
408
0.513
0.573
0.834
0.867
0.571
0.560
0.616
0.921
0.823
0.159
0.183
0.210
0.231
2
3
4
5
6
7
8
9
10
11
12
13
14
a In ethyl acetate.
b In solid state.
c Use Coumarin I in ethyl acetate (FFZ0.99) as the standard.15

4738
C.-J. J. Wu et al. / Tetrahedron 61 (2005) 4735–4741
p-terphenyls than asymmetric p-terphenyls except the pair
of 5 and 10. Symmetric p-terphenyl 5 with four cyano
groups at meta-positions on the peripheral rings has a blue
shift (1 and 3 nm in UV and PL spectra, respectively), than
the corresponding asymmetric p-terphenyl 10. The fluor-
escence quantum yield for symmetric and asymmetric
p-terphenyls with cyano groups at either para-positions or
two meta-positions on the peripheral rings are much higher
than that of other p-terphenyls. The results also showed that
the fluorescence quantum yields decreased when cyano
groups are substituted on the central benzene ring (11–14).
All the excitation spectra of these p-terphenyls showed two
electronic transitions. Such behavior points to a strong
mesomeric interaction of the alkoxy groups with the
terphenyl chromophore.14
the lmax in both UV absorption and PL emission spectra.
The lmax in UV of these p-terphenyls shows a red shift in
solid state than that in solution. Furthermore, only
p-terphenyls with two or four cyano groups at the meta-
positions of the peripheral rings showed a red shift in
emission spectra in their solid states than that in solution,
other p-terphenyls showed a blue shift in the emission
spectra in their solid states. The relationship between the
position and number of cyano groups and their influence on
the absorption and emission spectra of these p-terphenyls is
very interesting as compared to the phenylene–vinylene
analogues and need to have further studied.
4. Experimental
4.1. General
The lmax in both UV absorption and PL emission spectra
for 15 with hexahexyloxyl groups (319 and 385 nm,
respectively), are similar to that of symmetric p-terphenyl
1 and asymmetric p-terphenyl 6 with only two alkoxy
groups on the central benzene ring. This indicated that
alkoxy group influenced very little on the lmax in both
absorption and emission spectra.
4.1.1. Representative procedure of Suzuki coupling
reaction for the preparation of 2,5-dihexyloxy-1,4-
diphenylbenzene (1). o-Xylene (25 mL) was added to a
mixture of 2,5-dihexyloxy-1,4-benzenediboronic acid
(2.20 g, 5 mmol), bromobenzene (1.95 g, 12.5 mmol), and
potassium carbonate (4.15 g, 30 mmol) in a 100 mL round-
bottom flask under nitrogen atmosphere. A solution of
Pd(PPh3)4 (0.035 g, 0.03 mmol) in 5 mL of o-xylene was
added into the above mixture at 130 8C. The mixture was
cooled to room temperature after it was stirred and heated
for 72 h. The mixture was worked up with water and ethyl
acetate. The organic layer was dried over magnesium
sulfate, filtrated, and concentrated before recrystallization
by ethyl acetate and methanol to give 1.81 g (83% yield) of
the desired product. Mp 67–68 8C; RfZ0.9 (n-hexane/ethyl
It is interesting to know that the lmax in UV of these
symmetric and asymmetric p-terphenyls shows a red shift in
solid state than that in ethyl acetate solution, especially
for symmetric p-terphenyls 1, 2, and 4, which could have
37–41 nm red shift in their solid states than that in ethyl
acetate solution. Furthermore, symmetric p-terphenyls 1 and
2 both have a red shift (37 nm) in absorption than the
corresponding asymmetric p-terphenyls 6 and 7 in their
solid states. Contrast to the lmax in UV of these symmetric
and asymmetric p-terphenyls, only symmetric and asym-
metric p-terphenyls with two or four cyano groups at the
meta-positions of the peripheral rings (3, 5, 8, and 10)
showed a red shift (9–33 nm) of the emission spectra in their
solid states than that in ethyl acetate solution, other
symmetric and asymmetric p-terphenyls showed a blue
shift (1–22 nm) in the emission of their solid states than that
in ethyl acetate solution. Thus, the solid state of symmetric
and asymmetric p-terphenyls with four cyano groups at the
meta-positions of the peripheral rings could reach to the
blue light range in PL spectra. The preparation of devices
and their electro-optical properties are still under active
investigation in our collaborator’s lab, and their results will
be reported elsewhere when they are available.
1
acetateZ4:1) ; H NMR (CDCl3, 500 MHz) d 0.86 (t, JZ
7 Hz, 6H), 1.26–1.36 (m, 12H), 1.65–1.68 (m, 4H), 3.90 (t,
JZ6.4 Hz, 4H), 6.98 (s, 2H), 7.32 (t, JZ7.5 Hz, 2H), 7.41
(t, JZ7.5 Hz, 4H), 7.60 (d, JZ7.5 Hz, 4H) ppm; 13C NMR
(CDCl3, 125 MHz) d 13.96, 22.56, 25.72, 29.33, 31.45,
69.70, 116.44, 126.88, 127.89, 129.53, 130.91, 138.46,
150.31 ppm; IR n 1484.8, 1400.4, 1211.4, 1054.1, 763.9,
698.1 cmK1; MS m/z 430 (MC), 347, 262; HRMS calcd for
C30H38O2: 430.2872; found: 430.2869. Anal. Calcd for
C30H38O2: C, 83.68; H, 8.89. Found: C, 83.82; H, 8.79.
4.1.2. 2-[4-(2-Cyanophenyl)-2,5-dihexyloxyphenyl]ben-
zenecarbonitrile (2). Mp 129–130 8C; RfZ0.6 (n-hexane/
1
ethyl acetateZ4:1); H NMR (CDCl3, 500 MHz) d 0.83 (t,
JZ7 Hz, 6H), 1.21–1.28 (m, 12H), 1.64–1.67 (m, 4H), 3.94
(t, JZ6.5 Hz, 4H), 6.94 (s, 2H), 7.44 (t, JZ7.6 Hz, 2H),
7.56 (d, JZ7.7 Hz, 2H), 7.64 (t, JZ7.7 Hz, 2H), 7.74 (d,
JZ7.6 Hz, 2H) ppm; 13C NMR (CDCl3, 125 MHz) d 13.88,
22.47, 25.53, 29.05, 31.35, 69.19, 113.21, 115.51, 118.61,
127.42, 128.52, 131.11, 132.17, 132.74, 142.17,
149.80 ppm; IR n 2228.1, 1513.9, 1390.7, 1215.4, 1035.9,
762.8 cmK1; MS m/z 480.2 (MC), 412.0, 395.2, 313.1;
HRMS calcd for C32H36O2N2: 480.2777; found: 480.2786.
Anal. Calcd for C32H36O2N2: C, 79.97; H, 7.55; N, 5.83.
Found: C, 79.75; H, 7.67; N, 5.72.
3. Conclusion
Fifteen alkoxylated p-terphenyls with or without cyano
groups on either the central benzene ring or the peripheral
rings have been synthesized efficiently. The extinction
coefficiencies of UV spectra for p-terphenyls without cyano
groups on the central benzene ring are higher for
asymmetric p-terphenyls than the corresponding symmetric
p-terphenyls. The fluorescence quantum yield for
p-terphenyls with cyano groups at either para-positions or
two meta-positions of the peripheral rings are much higher
than that of other p-terphenyls. The fluorescence quantum
yields decreased when cyano groups are substituted on the
central benzene ring. Alkoxy group influenced very little on
4.1.3. 3-[4-(3-Cyanophenyl)-2,5-dihexyloxyphenyl]ben-
zenecarbonitrile (3). Mp 102–103 8C; RfZ0.525
(n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.87 (t, JZ7.5 Hz, 6H), 1.26–1.68 (m, 12H),

C.-J. J. Wu et al. / Tetrahedron 61 (2005) 4735–4741
4739
1.67–1.71 (m, 4H), 3.94 (t, JZ6 Hz, 4H), 6.94 (s, 2H), 7.52
(t, JZ7.7 Hz, 2H), 7.63 (d, JZ7.7 Hz, 2H), 7.7 (d, JZ
7.7 Hz, 2H), 7.89 (s, 2H) ppm; 13C NMR (CDCl3,
125 MHz) d 13.96, 22.53, 25.75, 29.17, 31.40, 69.58,
112.21, 115.48, 118.93, 128.77, 129.21, 130.57, 133.14,
133.89, 139.29, 150.16 ppm; IR n 2232.1, 1478.3, 1397.7,
1216.6, 1037.7, 785.9 cmK1; MS m/z 480.2 (MC), 397.1,
325.1, 312.1; HRMS calcd for C32H36O2N2: 480.2777;
found: 480.2772. Anal. Calcd for C32H36O2N2: C, 79.97; H,
7.55; N, 5.83. Found: C, 79.76; H, 7.73; N, 5.97.
for C29H30O2N2: C, 79.42; H, 6.89; N, 6.39. Found: C,
79.63; H, 7.05; N 6.54.
4.1.8. 3-[4-(3-Cyanophenyl)-2-(2-ethylhexyloxy)-5-meth-
oxyphenyl]benzenecarbonitrile (8). Mp 89–90 8C; RfZ
0.48 (n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.81–0.85 (m, 6H), 1.21–1.35 (m, 8H), 1.60–
1.62 (m, 1H), 3.78–3.83 (m, 5H), 6.92 (s, 1H), 6.93 (s, 1H),
7.50–7.54 (m, 2H), 7.61–7.63 (m, 2H), 7.79–7.81 (m, 2H),
7.87–7.88 (m, 2H) ppm; 13C NMR (CDCl3, 125 MHz) d
11.06, 13.97, 22.92, 23.93, 28.97, 30.60, 39.49, 56.33,
71.74, 112.12, 11.29, 114.00, 115.33, 118.84, 118.94,
128.70, 128.90, 130.56, 130.63, 133.07, 133.18, 133.82,
133.88, 132.67, 132.88, 142.01, 139.19, 150.37,
150.43 ppm; IR n 2228.0, 11518.3, 1396.4, 1216.1,
1039.0, 680.1 cmK1; MS m/z 439.1 (MCC1), 326.1,
265.1, 190.1; HRMS calcd for C29H31O2N2: 439.2386;
found: 439.2389. Anal. Calcd for C29H30O2N2: C, 79.42; H,
6.89; N, 6.39. Found: C, 79.66; H, 6.76; N, 6.31.
4.1.4. 4-[4-(4-Cyanophenyl)-2,5-dihexyloxyphenyl]ben-
zenecarbonitrile (4). Mp 153–154 8C; RfZ0.68 (n-hexane/
1
ethyl acetateZ4:1); H NMR (CDCl3, 500 MHz) d 0.87 (t,
JZ7 Hz, 6H), 1.25–1.33 (m, 12H), 1.67–1.68 (m, 4H), 3.93
(t, JZ6 Hz, 4H), 6.93 (s, 2H), 7.69 (s, 8H) ppm; 13C NMR
(CDCl3, 125 MHz) d 13.89, 22.48, 25.65, 29.11, 31.31,
69.56, 110.70, 115.55, 118.96, 129.82, 130.13, 131.70,
142.80, 150.18 ppm; IR n 2226.4, 1647.6, 1601.0, 1214.5,
776.0 cmK1; MS m/z 480.2 (MC), 397.1, 325.1, 312.1;
HRMS calcd for C32H36O2N2: 480.2777; found: 480.2772.
Anal. Calcd for C32H36O2N2: C, 79.97; H, 7.55; N, 5.83.
Found: C, 79.82; H, 7.75; N, 5.94.
4.1.9. 4-[4-(4-Cyanophenyl)-2-(2-ethylhexyloxy)-5-meth-
oxyphenyl]benzenecarbonitrile (9). Mp 192–193 8C; RfZ
0.13 (n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.80–0.84 (m, 6H), 1.20–1.33 (m, 8H), 1.55–
1.57 (m, 1H), 3.79–3.81 (m, 5H), 6.93 (s, 1H), 6.94 (s, 1H),
7.66–7.71 (m, 8H) ppm; 13C NMR(CDCl3,125 MHz) d
11.05, 13.96, 22.92, 23.90, 28.92, 30.54, 39.48, 56.35,
71.71, 110.74, 110.84, 114.14, 115.38, 118.97, 129.51,
129.84, 130.11, 130.19, 131.65, 131.86,142.70, 142.79,
150.44, 150.47 ppm; IR n 2228.8, 1601.8, 1211.1, 1048.8,
846.1, 554.8 cmK1; MS m/z 439.2 (MCC1), 339.1, 326.1,
267.1; HRMS calcd for C29H31O2N2: 439.2386; found:
439.2388. Anal. Calcd for C29H30O2N2: C, 79.42; H, 6.89;
N, 6.39. Found: C, 79.56; H, 6.97; N, 6.66.
4.1.5. 1,4-Bis(3,5-dicyanophenyl)-2,5-dihexyloxybenzene
(5). Mp 214–215 8C (dec); RfZ0.75 (ethyl acetate); 1H
NMR (CDCl3, 500 MHz) d 0.86 (t, JZ7.0 Hz, 6H), 1.28–
1.36 (m, 12H), 1.69–1.72 (m, 4H), 3.97 (t, JZ6.4 Hz, 4H),
6.91 (s, 2H), 7.90 (s, 2H), 8.08 (s, 4H) ppm; 13C NMR
(CDCl3, 125 MHz) d 13.93, 22.48, 25.79, 29.02, 31.35,
69.56, 113.88, 114.72, 116.67, 127.60, 133.47, 136.83,
140.50, 150.06 ppm; IR n 2236.2, 1222.1, 1026.7, 871.8,
779.72, 676.5 cmK1; MS m/z 530.1 (MC) 443.1, 389.1,
362.0, 273.1; HRMS calcd for C34H34O2N4: 530.2682;
found: 530.2688.
4.1.10. 1,4-Bis(3,5-dicyanophenyl)-2-(2-ethylhexyloxy)-
5-methoxybenzene (10). Mp O300 8C; RfZ0.575 (ethyl
acetate); 1H NMR (CDCl3, 500 MHz) d 0.83–0.87 (m, 6H),
1.20–1.38 (m, 8H), 1.60–1.68 (m, 1H), 3.84–3.87 (m, 5H),
6.91 (s, 1H), 6.92 (s, 1H), 7.90 (s, 2H), 8.06 (s, 2H), 8.08 (s,
2H) ppm; 13C NMR (CDCl3, 125 MHz) d 11.11, 14.03,
22.94, 24.02, 29.05, 30.72, 39.47, 56.39, 71.86, 113.55,
113.91, 114.03, 114.77, 116.64, 116.78, 133.54, 133.60,
136.87, 136.91, 140.74, 150.38 ppm; IR n 2237.7, 1593.0,
1388.2, 1218.4, 1028.8, 875.6 cmK1; MS m/z 488.1 (MC)
460.0, 443.1, 338.3, 195.1; HRMS calcd for C31H28O2N4:
488.2212; found: 488.2212.
4.1.6. 2-(2-Ethylhexyloxy)-5-methoxy-1,4-diphenylben-
zene (6). RfZ0.86 (n-hexane/ethyl acetateZ4:1); 1H
NMR (CDCl3, 500 MHz) d 0.82–0.88 (m, 6H), 1.23–1.38
(m, 8H), 1.60–1.64 (m, 1H), 3.79–3.83 (m, 5H), 6.99–7.01
(m, 2H), 7.34–7.36 (m, 2H), 7.41–7.47 (m, 4H), 7.60–7.62
(m, 4H) ppm; 13C NMR (CDCl3, 125 MHz) d 11.07, 14.02,
23.00, 23.89, 30.54, 39.57, 56.42, 71.80, 114.64, 116.14,
126.89, 127.05, 127.81, 128.06, 129.46, 129.58, 130.39,
130.89, 138.39, 150.45, 150.55 ppm; IR n 1600.1, 1519.9,
1393.4, 1208.3,1057.1, 760.2 cmK1; MS m/z 388.2 (MC),
289.1, 276.1, 262.1, 215; HRMS calcd for C27H32O2:
388.2402; found: 388.2403.
4.1.11. 3,6-Dihexyloxy-2,5-diphenylbenzene-1,4-dicarbo-
nitrile (11). Mp 134–135 8C; RfZ0.77 (n-hexane/ethyl
acetateZ4:1); H NMR (CDCl3, 500 MHz) d 0.82 (t, JZ
7 Hz, 6H), 1.08–1.20 (m, 12H), 1.47–1.49 (m, 4H), 3.62 (t,
JZ7 Hz, 4H), 7.52 (m, 10H) ppm; 13C NMR (CDCl3,
125 MHz) d 13.89, 22.38, 25.09, 29.65, 31.20, 75.54,
113.78, 114.32, 128.58, 129.36, 129.61, 132.44, 139.47,
4.1.7. 2-[4-(2-Cyanophenyl)-2-(2-ethylhexyloxy)-5-meth-
oxyphenyl]benzenecarbonitrile (7). Mp 148–149 8C; RfZ
0.38 (n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.76–0.89 (m, 6H), 1.14–1.24 (m, 8H), 1.60–
1.62 (m, 1H), 3.79–3.81 (m, 5H), 6.91 (s, 1H), 6.94 (s, 1H),
7.42–7.43 (m, 2H), 7.53–7.55 (m, 2H), 7.61–7.65 (m, 2H),
7.73–7.75 (m, 2H) ppm; 13C NMR (CDCl3, 125 MHz) d
11.04, 13.94, 22.91, 23.81, 28.89, 30.47, 39.38, 56.11,
71.58, 113.12, 113.26, 114.27, 115.49, 118.55, 118.58,
127.48, 127.54, 128.18, 128.65, 130.96, 131.14, 132.06,
132.42, 132.67, 132.88, 142.01, 142.13, 150.12 ppm; IR n
2228.8, 1472.8, 1395.4, 1214.7, 1037.8, 757.6 cmK1; MS
m/z 438.1 (MC), 327.1, 326.1, 311.1, 295.1; HRMS calcd
for C29H30O2N2: 438.2307; found: 438.2309. Anal. Calcd
1
155.67 ppm; IR n 2226.8, 1660.0, 1217.3, 763.9, 667.9 cmK1
;
MS m/z 481.2 (MCC1), 397.2, 325.5, 312.1; HRMS calcd
for C32H37O2N2: 481.2855; found: 481.2852. Anal. Calcd
for C32H36O2N2: C, 79.97; H, 7.55; N, 5.83. Found: C,
79.80; H, 7.65; N, 5.98.
4.1.12. 6-(2-Ethylhexyloxy)-3-methoxy-2,5-diphenyl-
benzene-1,4-dicarbonitrile (12). Mp 132–133 8C; RfZ0.7

4740
C.-J. J. Wu et al. / Tetrahedron 61 (2005) 4735–4741
(n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3, 500 MHz)
d 0.67 (t, JZ7.4 Hz, 3H), 0.82 (t, JZ7.5 Hz, 3H), 1.01–1.23
(m, 8H), 1.34–1.39 (m, 1H), 3.54–3.55 (m, 5H), 7.48–7.55
(m, 10H) ppm; 13C NMR (CDCl3, 125 MHz) d 10.84, 13.95,
22.80, 23.21, 28.80, 29.82, 40.17, 61.98, 78.01, 113.50,
114.19, 128.61, 129.73, 129.46, 129.64, 139.23, 139.65,
156.03, 156.11 ppm; IR n 2231.7, 1444.2, 1378.5, 1240.2,
1010.5, 699.2 cmK1; MS m/z 438.2 (MC), 326.1, 311.1,
282.1, 256.1, 227.1; HRMS calcd for C29H30O2N2:
438.2307; found: 438.2299. Anal. Calcd for C29H30O2N2:
C, 79.42; H, 6.89; N, 6.39. Found: C, 79.58; H, 6.97; N,
6.55.
gradually warmed up and stirred for another 12 h. Then,
2 N HCl (20 mL) was added and stirred for another 30 min
before adding water (30 mL). The product was extracted by
diethyl ether (50 mL!5), dried over magnesium sulfate,
filtrated, and concentrated. Ethyl acetate (60 mL) was added
to the concentrated mixture, filtrated and used ethyl acetate
to washed the precipitate. After removing volatile solvents
under vacuum, the product was obtained as a white powder
(2.27 g, 79% yield). Mp 194–195 8C (dec); 1H NMR
(DMSO-d6, 500 MHz) d 0.93 (t, JZ7 Hz, 6H), 1.34–1.48
(m, 12H), 1.76–1.80 (m, 4H), 3.36 (s, 4H), 4.04 (t, JZ
6.5 Hz, 4H), 7.83 (s, 2H) ppm; 13C NMR (DMSO-d6,
125 MHz) d 14.24, 22.42, 25.52, 29.14, 31.33, 68.82,
118.39, 124.87 (C–B(OH)2), 157.31 ppm.
4.1.13. 1,4-Bis(4-cyanophenyl)-3,6-dicyano-2,5-dihexyl-
oxybenzene (13). Mp 112–113 8C; RfZ0.36 (n-hexane/
1
ethyl acetateZ4:1); H NMR (CDCl3, 500 MHz) d 0.82 (t,
4.1.17. 2-(2-Ethylhexyloxy)-5-methoxy-1,4-benzene-
diboronic acid (17). Following the procedure as described
above for the synthesis of 16, compound 17 was prepared
from 1,4-dibromo-2-(2-ethyl-hexyloxy)-5-methoxybenzene
(1.97 g, 5 mmol), n-butyllithium (2.5 M in hexanes, 5 mL,
12.5 mmol), and trimethylborate (1.42 mL, 12.5 mmol).
The crude product (1.26 g, 78% yield) was used without
further purification. It can be further purified by recrystal-
lization three times from ethyl acetate to give the desired
JZ7.3 Hz, 6H), 1.08–1.23 (m, 12H), 1.46–1.49 (m, 4H),
3.66 (t, JZ6.4 Hz, 4H), 7.62 (d, JZ8.3 Hz, 4H), 7.82 (d,
JZ8.3 Hz, 4H) ppm; 13C NMR (CDCl3, 125 MHz) d 13.92,
22.43, 25.13, 29.70, 31.20, 76.00, 113.56, 113.64, 113.78,
117.97, 130.60, 132.45, 136.71, 138.65, 155.67 ppm; IR n
2236.2, 1435.9, 1373.3, 1306.9, 1218.4, 997.2, 757.6 cmK1
;
MS m/z 530.1 (MC), 443.1, 389.1, 362.0, 273.1; HRMS
calcd for C34H34O2N4: 530.2682; found: 530.2686. Anal.
Calcd for C34H34O2N4: C, 76.96; H, 6.46; N, 10.56. Found:
C, 77.10; H, 6.65; N, 10.59.
1
product 17 as a white solid. Mp 114–115 8C; H NMR
(DMSO-d6, 500 MHz) d 0.77 (t, JZ7 Hz, 6H), 1.17–1.33
(m, 8H), 1.58 (m, 1H), 3.67 (s, 3H), 3.78 (d, JZ5.5 Hz, 2H),
7.07 (s, 1H), 7.08 (s, 1H), 7.68 (s, 4H) ppm; 13C NMR
(DMSO-d6, 125 MHz) d 11.40, 14.34, 22.90, 23.89, 28.86,
30.45, 39.77, 56.17, 71.13, 117.18, 118.31, 124.68
(C–B(OH)2), 125.18 (C–B(OH)2), 157.48, 157.80 ppm.
4.1.14. 1,4-Bis(4-cyanophenyl)-3,6-dicyano-2-(2-ethyl-
hexyloxy)-5-methoxybenzene (14). Mp 194–195 8C; RfZ
0.3 (n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.68 (t, JZ7.5 Hz, 3H), 0.84 (t, JZ7.5 Hz,
3H), 1.00–1.25 (m, 8H), 1.35–1.38 (m, 1H), 3.56–3.62 (m,
5H), 7.63–7.66 (m, 4H), 7.84–7.89 (m, 4H) ppm; 13C NMR
(CDCl3, 125 MHz) d 10.87, 13.99, 22.83, 23.21, 24.85,
28.86, 29.83, 40.27, 62.55, 78.85, 113.37, 113.49, 113.56,
113.81, 113.88, 117.92, 130.43, 130.65, 132.44, 132.60,
135.09, 136.49, 136.66, 138.50, 138.77, 156.00,
156.09 ppm; IR n 2231.1, 1376.5, 1101.4, 836.3,
558.5 cmK1; MS m/z 489.1 (MCC1) 388.1, 376.0, 349.1,
263.1; HRMS calcd for C31H29O2N4: 489.2391; found:
489.2305. Anal. Calcd for C31H28O2N4: C, 76.21; H, 5.78;
N, 11.47. Found: C, 76.42; H, 5.88; N, 11.62.
4.1.18. 2,5-Dibromo-3,6-dihexyloxybenzene-1,4-dicarbo-
nitrile (18). To a mixture of 2,5-dihexyloxybenzene-1,4-
dicarbonitrile (1.65 g, 5 mmol) and N-bromosuccinimide
(2.23 g, 12.5 mmol) in 100 mL round-bottom flask was
added trifluoroacetic acid (2 mL) until all compounds are
completely dissolved. Then, concentrated sulfuric acid
(2.7 mL, 50 mmol) was added and stirred for another 4 h
at room temperature. Saturated sodium bicarbonate (5 mL)
was added to the mixture and extracted with ethyl acetate
(30 mL!5), dried over magnesium sulfate, filtrated, and
concentrated. The crude product was recrystallized by ethyl
acetate (10 mL) and methanol (5 mL) to give 1.79 g (74%
yield) of the desired product as a white powder. Mp 107–
108 8C; RfZ0.775 (n-hexane/ethyl acetateZ4:1); 1H NMR
(CDCl3, 500 MHz) d 0.90 (t, JZ7 Hz, 6H), 1.32–1.54 (m,
12H), 1.83–1.93 (m, 4H), 4.16 (t, JZ6.6 Hz, 4H) ppm; 13C
NMR (CDCl3, 125 MHz) d 13.98, 22.50, 25.27, 29.94,
31.44, 76.75, 113.08, 117.00, 120.68, 156.43 ppm; IR n
2234.0, 1427.9, 1371.9, 1204.4, 759.9 cmK1; MS m/z 487.3
(MCC3), 484 (MC), 219, 307, 370; HRMS calcd for
C20H26Br2N2O2: 484.0361; found: 484.0364. Anal. Calcd
for C20H26Br2O2N2: C, 49.40; H, 5.39; N, 5.76. Found: C,
49.62; H, 5.53; N, 5.89.
4.1.15. 2-[4-(2,5-Dihexyloxyphenyl)-2,5-dihexyloxy-
phenyl]-1,4-dihexyloxybenzene (15). Mp 64–65 8C (dec);
1
RfZ0.9 (n-hexane/ethyl acetateZ4:1); H NMR (CDCl3,
500 MHz) d 0.83–0.92 (m, 18H), 1.22–1.34 (m, 24H), 1.56–
1.64 (m, 12H), 1.75–1.78 (m, 12H), 3.81–3.94 (m, 12H),
6.81–702 (m, 8H) ppm; 13C NMR (CDCl3, 125 MHz) d
13.98, 22.55, 25.65, 25.68, 25.74, 29.39, 29.65, 31.56,
31.59, 68.55, 69.41, 69.47, 69.70, 114.07, 114.39, 116.72,
116.88, 117.06, 117.99, 127.44, 127.54, 129.35, 149.95,
150.00, 150.75, 152.74 ppm; MS m/z 830 (MC), 630, 570,
554, 486, 470; IR n 1465.4, 1207.4, 1037.8, 938.2,
798.2 cmK1; HRMS calcd for C54H86O6: 830.6424; found:
830.6425.
4.1.19. 2,5-Bibromo-6-(2-ethylhexyloxy)-3-methoxy-
benzene-1,4-dicarbonitrile (19). Following the procedure
as described above for the synthesis of 18, compound 19
was prepared from 2-(2-ethylhexyloxy)-5-methoxy-
benzene-1,4-dicarbonitrile (1.43 g, 5 mmol), N-bromo-
succinimide (2.85 g, 15 mmol), trifluoroacetic acid
(12 mL), and concentrated sulfuric acid (2.78 mL,
4.1.16. 2,5-Dihexyloxy-1,4-benzenediboronic acid (16).
n-Butyllithium (2.5 M in hexanes, 5 mL, 12.5 mmol) was
added dropwise to a solution of 2,5-dibromo-1,4-dihexyl-
oxybenzene (2.2 g, 5 mmol) in dried diethyl ether (50 mL)
for 1 h at 0 8C followed by the dropwise addition of
trimethylborate (1.7 mL, 15 mmol). The mixture was

C.-J. J. Wu et al. / Tetrahedron 61 (2005) 4735–4741
4741
50 mmol). The crude product was recrystallized from ethyl
References and notes
acetate–methanol to give the desired product 19 as a white
solid (1.95 g, 88% yield). Mp 125–126 8C; RfZ0.8
(n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3,
500 MHz) d 0.90–0.99 (m, 6H), 1.34–1.62 (m, 8H), 1.82–
1.85 (m, 1H), 4.05–4.09 (m, 5H) ppm; 13C NMR (CDCl3,
125 MHz) d 11.08, 14.02, 22.91, 23.43, 28.98, 29.93, 40.24,
62.70, 79.12, 112.83, 112.98, 116.70, 116.78, 120.55,
167.76, 156.80 ppm; IR n 2233.4, 1455.1, 1376.9, 1208.9,
1007.2, 730.64 cmK1; MS m/z 445 (MCC3), 442 (MC),
334, 332, 316, 288; HRMS calcd for C17H21Br2N2O2:
442.9970; found: 442.9966. Anal. Calcd for
C17H20Br2N2O2: C, 45.97; H, 4.54; N, 6.31. Found: C,
46.12; H, 4.69; N, 6.46.
1. Luo, F. T.; Tao, Y. T.; Ko, S. L.; Chuen, C. H.; Chen, H.
J. Mater. Chem. 2002, 12, 47.
2. Wang, B. C.; Chang, J. C.; Tso, H. C.; Cheng, C. Y. Chemistry
2001, 59, 545 and references cited therein.
3. Bredas, J. L. Adv. Mater. 1995, 7, 263.
4. (a) Greenham, N. C.; Moratti, S. C.; Bradley, D. D. C.; Friend,
R. H.; Holmes, A. B. Nature 1993, 365, 628. (b) Moratti, S. C.;
Cervini, R.; Holmes, A. B.; Baigent, D. R.; Friend, R. H.;
Greenham, N. C.; Gru¨ner, J.; Hamer, P. J. Synth. Met. 1995,
71, 2117.
5. Ullmann, F.; Bielecki, J. Chem. Ber. 1901, 34, 2174.
6. (a) Shirakawa, E.; Murota, Y.; Nakao, Y.; Hiama, T. Synlett
1997, 1143. (b) Yamaguchi, S.; Ohno, S.; Tamao, K. Synlett
1997, 1199. (c) Pabst, G. R.; Sauer, J. Tetrahedron 1999, 55,
5067. (d) Pabst, G. R.; Pfu¨ller, O. C.; Sauer, J. Tetrahedron
1999, 55, 5047. (e) Hittchcok, S.; Mayhugh, D. R.; Gregory,
G. S. Tetrahedron Lett. 1995, 36, 9085. (f) Iyoda, M.; Miura,
M.; Sasaki, S.; Kabir, S. M. H.; Kuwatani, Y.; Yoshida, M.
Tetrahedron Lett. 1997, 38, 4581.
4.1.20. 4,4,5,5-Tetramethyl-2-(4-cyanophenyl)-1,3,2-
dioxaborolane (20). The mixture of 4-bromobenzene-
carbonitrile (0.91 g, 5 mmol), potassium acetate (1.17 g,
15 mmol), bis(pinaconato)diboron (1.40 g, 5.5 mmol),
PdCl2(dppf) (0.018 g, 0.015 mmol) in DMSO (5 mL) was
heated under nitrogen at 80 8C for 6 h. The mixture was
cooled to room temperature and water (50 mL) was added,
and the product was extracted with ethyl acetate (50 mL!
3), dried over magnesium sulfate, filtrated, and concen-
trated. The product was purified by column chromatography
(silica gel, ethyl acetate /n-hexanesZ1/20) to give 0.86 g
(75% yield) of the desired product. Mp 94–95 8C; RfZ0.725
(n-hexane/ethyl acetateZ4:1); 1H NMR (CDCl3, 500 MHz)
d 1.35 (s, 12H), 7.65 (d, JZ7.7 Hz, 2H), 7.87 (d, JZ7.7 Hz,
2H) ppm; IR n 2221.4, 1358.5, 1273.7, 1441.0, 838.7,
7. (a) Miyaura, N.; Yanagi, T.; Suzuki, A. Synth. Commun. 1981,
11, 513. (b) Martin, A. R.; Yang, Y. Acta Chem. Scand. 1993,
47, 221. (c) For review: Miyaura, N.; Suzuki, A. Chem. Rev.
1995, 95, 2457. (d) Fitton, P.; Rick, E. A. J. Organomet. Chem.
1971, 28, 287.
8. (a) Negishi, E.-I.; Luo, F.-T.; Frisbee, R.; Matsushita, H.
Heterocycles 1982, 18, 117. (b) Tucker, C. E.; Majid, T. N.;
Knochel, P. J. Am. Chem. Soc. 1992, 114, 3983. (c) Amat, M.;
Hadida, S.; Bosch, J. Tetrahedron Lett. 1994, 35, 793. (d)
Miller, J. A.; Farrell, R. P. Tetrahedron Lett. 1998, 39, 7275.
(e) Majid, T. N.; Knochel, P. Tetrahedron Lett. 1990, 31, 4413.
(f) Wu, X.; Rieke, R. D. J. Org. Chem. 1995, 60, 6658. (g)
Rieke, R. D.; Kim, S.-H.; Wu, X. J. Org. Chem. 1997, 62,
6921. (h) Sakamoto, T.; Kondo, Y.; Murata, N.; Yamanaka, H.
Tetrahedron Lett. 1992, 33, 5373. (i) Sakamoto, T.; Kondo, Y.;
Murata, N.; Yamanaka, H. Tetrahedron 1993, 49, 9713.
9. (a) Minato, A.; Tamao, K.; Hayashi, T.; Suzuki, K.; Kumada,
M. Tetrahedron Lett. 1981, 22, 5319. (b) Sekiya, A.; Ishikawa,
N. J. Organomet. Chem. 1976, 118, 349. (c) Widdowson,
D. A.; Zhang, Y.-Z. Tetrahedron 1986, 42, 2111. (d) Amatore,
C.; Jutand, A.; Negri, S.; Fauvarque, J.-F. J. Organomet.
Chem. 1990, 390, 389. (e) Bumagin, N. A.; Sokolova, A. F.;
Beletskaya, I. P. Russ. Chem. Bull. 1993, 42, 1926. (f)
Kamikawa, T.; Hayashi, T. Synlett 1997, 163.
650.7 cmK1
.
4.1.21. 2-Bromo-1,4-dihexyloxybenzene (21). To a
solution of 2,5-dibromo-1,4-dihexyloxybenzene (2.2 g,
5 mmol) in dried diethyl ether (50 mL) at 0 8C was added
n-butyllithium (2.5 M in hexanes, 2.2 mL, 5.5 mmol)
dropwise. After the temperature of the mixture was
gradually warmed up to the room temperature for 12 h,
2 N HCl (20 mL) was added to it and stirred for another
30 min. The product was extracted with ethyl acetate
(50 mL!3), dried over magnesium sulfate, filtrated, and
concentrated. The product was purified by column chroma-
tography (silica gel, ethyl acetate/n-hexanesZ1/20) to give
1.45 g (80% yield) of the desired product as a liquid in
10. Lu, T. Y.; Xue, C.; Luo, F. T. Tetrahedron Lett. 2003, 44,
1587.
1
orange color. RfZ0.85 (n-hexane/ethyl acetateZ4:1); H
11. Luo, F. T.; Lu, T. Y.; Xue, C. Tetrahedron Lett. 2003, 44,
7249.
NMR (CDCl3, 500 MHz) d 0.90 (t, JZ7 Hz, 6H), 1.22–1.56
(m, 12H), 1.70–1.83 (m, 4H), 3.78–4.07 (m, 4H), 6.81 (d,
JZ9.3 Hz, 2H), 7.10 (d, JZ3.5 Hz, 1H) ppm; 13C NMR
(CDCl3, 125 MHz) d 13.89, 22.49, 25.59, 29.15, 31.46,
68.50, 69.87, 112.58, 113.99, 114.34, 119.33, 149.61,
153.43 ppm; MS m/z 358.1, 356.1 (MC), 278.2, 190.0;
HRMS calcd for C18H29BrO2: 356.1351; found: 356.1352.
12. (a) Mirbach, M. J.; Liu, K.-C.; Mirbach, M. F.; Cherry, W. R.;
Turro, N. J.; Engel, P. S. J. Am. Chem. Soc. 1978, 100, 5122.
(b) Kassab, E. A.; Marzouk, M. I.; El-Hashash, M. J. Serb.
Chem. Soc. 2002, 67, 593.
13. For example, the minimum dihedral angle for the two adjacent
phenyl rings was 51.178 (for 1), while the minimum dihedral
angle for the two adjacent phenyl rings was 47.168 (for 6) by
Spartan’04//6-31G** calculations.
14. Ndayikengurukiye, H.; Jacobs, S.; Tachelet, W.; Van Der
Looy, J.; Pollaris, A.; Geise, H. J.; Claeys, M.; Kauffmann,
J. M.; Janietz, S. Tetrahedron 1997, 53, 13811.
Acknowledgements
We thank the National Science Council and Academia
Sinica for financial support.
15. Jones, G.; Jackson, W. R.; Choi, C. Y.; Bergmark, W. R.
J. Phys. Chem. 1985, 89, 294.