Suzuki-Miyaura monocouplings of p-dibromobiphenyl and substituted p-dibromo(penta-p-phenylenes)

Article abstract of DOI:10.1016/j.tet.2011.02.025

The mono/bis ratio for the Suzuki-Miyaura cross coupling of p-dibromobiphenyl and p-dibromo(pentap-phenylenes) with arylboronic acids and esters has been studied. The coupling reaction is demonstrated to be highly selective for monoarylation when the substrate is a p-dibromooligoarene, while selective biarylation is obtained for p-diiodoterphenyl. The mono/bis coupling-ratio for these compounds was highly sensitive to the nature of the halogen involved, however steric hindrance or electronic characteristics of the boronic derivative did not affect the selectivity of the reaction. The reaction yields observed were higher at room temperature and when arylboronic pinacol esters were used. These reactions also offer a useful method for the preparation of asymmetrically substituted terphenyls and hexa-p-phenylenes, giving good yields.

Full text of DOI:10.1016/j.tet.2011.02.025

Tetrahedron 67 (2011) 2555e2561
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
SuzukieMiyaura monocouplings of p-dibromobiphenyl and substituted
p-dibromo(penta-p-phenylenes)
*
ꢀ
ꢀ
ꢀ
Elena Guillen, Jesus Hierrezuelo, Rocio Martínez-Mallorquín, J. Manuel Lopez-Romero , Rodrigo Rico
ꢀ
ꢀ
ꢀ
Departamento de Química Organica, Facultad de Ciencias, Universidad de Malaga, 29071 Malaga, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
The mono/bis ratio for the SuzukieMiyaura cross coupling of p-dibromobiphenyl and p-dibromo(penta-
p-phenylenes) with arylboronic acids and esters has been studied. The coupling reaction is demonstrated
to be highly selective for monoarylation when the substrate is a p-dibromooligoarene, while selective
biarylation is obtained for p-diiodoterphenyl. The mono/bis coupling-ratio for these compounds was
highly sensitive to the nature of the halogen involved, however steric hindrance or electronic charac-
teristics of the boronic derivative did not affect the selectivity of the reaction. The reaction yields ob-
served were higher at room temperature and when arylboronic pinacol esters were used. These reactions
also offer a useful method for the preparation of asymmetrically substituted terphenyls and hexa-p-
phenylenes, giving good yields.
Received 23 December 2010
Received in revised form 1 February 2011
Accepted 10 February 2011
Available online 15 February 2011
Dedicated to the memory of Professor Rafael
Suau Suarez
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
Cross-coupling
Oligo-p-phenylenes
Hexa-p-phenylenes
Quaterphenyls
Dibromoarenes
Nanostructures
1. Introduction
the key-step. The reaction is a flexible, advantageous synthetic
method for constructing CeC biaryl bonds under mild reaction
Research on
p-conjugated poly-p-phenylenes has seen a tre-
conditions,17 and has been used for a great number of applications
in arylearyl bond formation. These include variously substituted
derivatives, such as highly substituted biphenyls, heterobiaryls,
poly-p-phenylenes, polyheterobiaryls, and many other classes of
biaryls.18
mendous number of recent developments due to their interesting
optoelectronic and electrical properties. Upon doping, they not only
act as excellent organic conductors, but also as long-range electron
transfer materials.1,2 They can be used as the active component in
optical devices, such as light-emitting diodes,3 and they display
liquid crystalline properties as well as a high degree of thermal
stability.4 Among them, oligo-p-phenylenes are of particular in-
terest because, when compared with polymers, they are easily
obtained by controlled organic reactions as a monodisperse mate-
rial of great purity5e8 and owing to its rigid rod-like molecular
structure9 they have been used in the construction of organic
nanostructures.10e13. Use in the latter case has been demonstrated
with symmetrical penta-p-phenylenes, which were rigid enough to
be used to form the legs of giant tripod-shaped molecules.14,15
These molecules have been proposed as adsorbates for control-
ling the orientation and location of individual molecules on nano-
structured surfaces.16
In cases involving poly-haloaromatic precursors in a Suzuki re-
action, the most common outcome is exhaustive multiple coupling,
and an excess of the boronic acid or ester coupling partner is often
employed to drive the reaction to completion. However, a significant
number of selective single couplings with di- or tri-haloaromatics
have also been reported.19 In these cases, to encourage single cou-
pling products, a low molar ratio of boronic acid to polyhalo-
benzenes is employed. However, contradictory to this, it has also
been reported that during the selective double coupling of arylbor-
onic acids and esters with symmetrical p-dihalobenzene this molar
ratio does not affect the selectivity. Even when the ratio is 10/1 the
products of double coupling are preferentially obtained.19 Halogen
has also been identified as one of the major factors in determining
selectivity, with p-dibromobenzene resulting in single couplings
with arylboronic acids with high selectivity, while p-diiodobenzene
results in double-coupled products.19
The syntheses of oligo-p-phenylenes usually involves the pal-
ladium-catalyzed Suzuki cross coupling of dihaloaryl derivatives as
To the best of our knowledge, no study on the selectivity of the
p-dihalobiphenyl and p-dihalo(oligo-p-phenylenes) reaction has
ꢀ
* Corresponding author. E-mail address: jmromero@uma.es (J.M. Lopez-Romero).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.02.025

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E. Guillen et al. / Tetrahedron 67 (2011) 2555e2561
2556
been reported. In this paper we study the selectivity of the Suzuki
cross-coupling reaction of the p-dibromobiphenyl and p-dibromo
(penta-p-phenylene) derivatives. These are, as mentioned above,
compounds of interest in the synthesis of tripod-shaped oligo-p-
phenylenes. The results also provide a concise, practical, and high-
yielding synthesis of asymmetrical ter- and hexa-p-phenylenes
by employing selective SuzukieMiyaura reactions for the mono-
arylation of symmetrical dibromoarenes.
Sinclair for p-dibromobenzene (2).19 We investigated the re-
action of 1 with a number of boronic acids and esters with
different substitution patterns (compounds 3aef, Table 1). Pre-
viously, model compound 2 was coupled with p-methoxyphenyl
boronic acid (3a) by using 1.5 equiv of 3a, 8 mol % of palladium
catalyst, 2 equiv of Cs2CO3, and a mixture of toluene/methanol
as a solvent (Table 1, entry 1). After 12 h refluxing, the reaction
was complete and only the mono-coupled compound p-
methoxybiphenyl (4) was isolated in 82% yield. The bis-coupled
product was not detected.
2. Results and discussion
Selectivity of this reaction was then studied for 1 (results are
shown in Table 1). Under the above conditions, the cross coupling of
1 with the p-methoxy substituted boronic acid 3a did not give the
We evaluated the Suzuki cross coupling of p-dibromobi-
phenyl (1) under the same optimized conditions reported by
Table 1
Pd catalyzed cross coupling of p-dibromobiphenyl (1) and p-dibromobenzene (2) with boronic acids or esters (3aef)
OH
a, R= p-OMe
b, R= o-OMe
c, R= o-CN
+
MeO
Br
Br
MeO
B
OH
d and e, R= p-CN
f, R= p-COOMe
4
2
3a
OR1
OR1
R
R
R
R
R
+
+
+
Br
Br
B
Br
H
2
2
2
2
1
6a-d
3a-f
5a-f
7a-f
Mono-coupled
Mono-coupling and
debromination
Bis-coupled
Entry
Dibromide 1 or 2
Boronic acid/ester 3aef
Conditions (a) or (b)
Ratio % Mono/Bis
React. Prod. and yield (%)
Mono
Bis
Br
B(OH)2
1
(a), reflux, 12 h
100/0
4 (82)
7a (0)
MeO
3a
Br
2
2
(a), reflux, 12 h
(a), rt, 18 h
72a/28
99/1
6b (61)a
5b (58)
6a (83)a
5a (93)
6c (43)a
5c (61)
6d (62)a
5d (69)
5e (78)
7b (24)
7b (4)
d
B(OH)2
OMe
3
3b
4
(a), reflux, 12 h
(a), rt, 18 h
100a/0
100/0
74a/26
73/27
74a/26
73/27
87/13
B(OH)2
MeO
5
3a
d
6
(a), reflux, 12 h
(a), rt, 18 h
7c (9)
7c (22)
7d (16)
7d (25)
7e (11)
Br
Br
B(OH)2
CN
7
3c
8
(a), reflux, 12 h
(a), rt, 18 h
B(OH)2
NC
NC
9
3d
1
O
B
10
(b), rt, 18 h
O
3e
O
B
11
(b), rt, 18 h
98/2
5f (56)
7f (5)
O
MeOOC
3f
(a) 1/1.5 mol ratio boronic acid or ester to dibromide/8 mol % Pd(PPh3)4/2 equiv Cs2CO3/toluene/methanol.
(b) 8 mol % Pd(PPh3)4/2 equiv Ag2CO3/tetrahydrofuran.
a
Monocoupling and debromination product.

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E. Guillen et al. / Tetrahedron 67 (2011) 2555e2561
2557
expected mono-coupled product 5a (Table 1, entry 4). Instead, the
only product resulting from the monocoupling and debromination
(6a) was isolated in 83% yield (entry 4). Similar results were
obtained under refluxing conditions when 1 was coupled with
phenyl boronic acids 3bed: monocoupling and debromination
products 6bed were obtained, respectively, as the main reaction
products (entries 2, 6, and 8) with 61, 43, and 62% yields, re-
spectively. In these cases, bis-coupled products were also isolated
as minor compounds (7bed, entries 2, 6, and 8). The debromination
reaction under Pd-catalyzed coupling conditions is known to occur
as an undesired side reaction, for example, when protic conditions
are used.20
boronate, where the bis-coupled product is the main compound
(86%), in preference to the mono-coupled compound (14%).19 In
fact, selective multiple couplings appear to be a general trait of
polyiodoaryls, while selective monocoupling is a general trait of
polybromoaryls. We studied the coupling reaction of p-diiodoter-
phenyl (8) with boronic acids 9 and 10 under Suzuki conditions
(Table 2), since we used compound 8 as a starting material for
phenyl homologation to obtain several substituted oligo-p-phe-
nylenes, used as molecular legs in tripodal adsorbates.14 As for 1, in
this reaction a 1/1.5 mol ratio of boronic acid to diiodide 8 was used.
Even with an excess of diiodide we only obtained the bis-coupled
products (11 and 12), while monocoupling products were not
detected. This result means that the selectivity to biscoupling found
for p-diiodobenzene and p-diiodobiphenyl is also extended to
p-diiodoterphenyl (8).
No significant yield or mono/bis coupling differences were
found with electron rich (3a and 3b), electron poor (3c and 3d) or
sterically hindered (3b and 3c) or unhindered aromatic boronic
Table 2
Pd-catalyzed coupling of p-diiodoterphenyl (8) with boronic acids (9 and 10)
Entry
p-Diiodoterphenyl
Boronic acid
Conditions
Yield %
94
React. Prod. and ratio (%)
mono/bis
B(OH)2
1
I
0/100, 11
Br
9
1/1.5 mol ratio boronic acid to 8/Reflux 8%
Pd(PPh3)4/2 equiv Cs2CO3/toluene/MeOH
MeO
Br
B(OH)2
OMe
2
90
0/100, 12
10
I
8
acids. These results show the monocoupling and debromination
processes to be predominant for p-dibromobiphenyl (1) when the
reaction is carried out under reflux.
Access to the substituted penta-p-phenylenes 11 and 12 allowed
us to extend the study of the mono/bis ratio for Suzuki coupling for
these products, with a special interest in the monocoupling, since
the synthetic use of oligo-p-phenylenes of defined length depends
on the ability to differentiate both ends of the molecule.5,12,13
However, any attempt to react the tetramethoxy derivative 12
with the boronic acid 3a only resulted in the isolation of the
debromination product 13, together with a small quantity of the
monocoupling and debromination compound 14 (Table 3, entries
1 and 2). When the reaction was carried out with compound 11 at
room temperature or under refluxing conditions, only the starting
material was recovered, and no reaction products were isolated
(Table 3, entries 4 and 5).
In order to avoid the debromination process, reactions of 1 with
arylboronic acids 3aed were carried out at room temperature
(Table 1, entries 3, 5, 7, and 9). Monocoupling products were
obtained in good yields, and the corresponding p-bromoterphenyls
5aed were isolated in good yields too. Small quantities of the bis-
coupled products were also isolated; p-quaterphenyls 7bed, as
shown in entries 3, 7, and 9. Under room temperature conditions no
bis-coupled product (7a) was found for the electron rich phenyl
boronic acid 3a, and only a small quantity for the ortho-methoxy
substituted 3b (compound 7b, 4% yield, entry 3).
The Suzuki reaction of p-dibromobiphenyl (1) was also carried
out with phenyl boronic esters 3e and 3f (Table 1, entries 10 and 11).
Good yields were obtained in both cases under smooth conditions
(rt, 18 h) by using 1.5 equiv of ester, 8 mol % of Pd(PPh3)4, 2 equiv of
Ag2CO3 as the base and tetrahydrofuran as the solvent. The use of
silver carbonate and an aprotic solvent was found to optimize
coupling reactions with arylboronic esters.21 Major compounds
were the mono-coupled products 5e and 5f, isolated in a mono/bis
ratio of 87/13 and 98/2 to the bis-coupled products 7e and 7f,
respectively.
These results show that the reported monocoupling selectivity
for the reaction of p-dibromobenzene (2) with boronic acids and
esters can be extended to p-dibromobiphenyl (1). However,
contrary to the data reported in the literature,19 yields and
selectivity to monocoupling of 1 is more pronounced in pinacolate
esters than in the corresponding acid derivatives (Table 1, entries 9
and 10). These results are in agreement with those reported for the
coupling of p-diiodobiphenyl with pinacolyl 2,6-dimethoxyphenyl
The lack of reactivity of penta-p-phenylene 11, even in refluxing
toluene/methanol, can probably be attributed to the remarkably
poor solubility of this compound in this mixture of solvents. Also,11
is less soluble than 12 in usual organic solvents. The coupling re-
action with 11 as a substrate was also carried out in ethanol and
DMF, both typically used Suzuki solvents. In this case only the
starting material was recovered and the expected monocoupling
product of 11 was not detected.
However, when we carried out the Suzuki reaction for 11 and 12
using the corresponding phenyl boronic pinacol ester (3e and 3f),
good yields of the mono-coupled product were obtained, and the
hexa-p-phenylenes 15,16 and 17 were isolated in yields of 78, 54, and
55%, respectively (Table 3, entries 3, 6, and 7), and bis-coupled prod-
ucts were not detected. The higher yield obtained for the coupling of
12 can be again attributed to the better solubility of this compound in
THF compared to 11. As for compound 1, coupling reactions with bo-
ronic acid pinacol ester derivatives give better reaction yields, to-
gether with a higher selectivity to the mono-coupled products.

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E. Guillen et al. / Tetrahedron 67 (2011) 2555e2561
2558
Table 3
Pd-catalyzed coupling of p-dibromo(penta-p-phenylenes) 11 and 12 with boronic acids or esters 3a, 3e, and 3f
MeO
MeO
R2
R2
3
R2
R2
OMe
OMe
13
OR1
OR1
+
Br
Br
R
B
+
+
Br
R
MeO
MeO
3
3
R2
R2
R2
R2
OMe
11, R= Me
3a, 3e, 3f
15, R= COOMe, R2= OMe
16, R= COOMe, R2= Me
17, R= CN, R2= OMe
12, R= OMe
3
OMe
OMe
14
Entry
Dibromide
Boronic acid/ester
Conditions (a) or (b)
Ratio %
React. Prod. and yield (%)
Mono/Bis
Debromin.
Mono
Br
OMe
MeO
MeO
1
2
(a), rt, 18 h
NR
d
d
d
B(OH)2
(a), reflux, 12 h
d
13a (80)
14b (14)
MeO
3
3a
OMe
O
B
3
(b), rt, 18 h
100/0
d
15 (78)
O
Br
12
MeOOC
3f
4
5
6
(a), rt, 18 h
NR
d
d
d
d
B(OH)2
O
Br
MeO
3a
(a), reflux, 12 h
(b), rt, 18 h
NR
d
B
100/0
16 (54)
O
3
MeOOC
3f
O
B
Br
7
(b), rt, 18 h
100/0
d
17 (55)
O
11
NC
3e
(a) 1/1.5 mol ratio boronic acid or ester to dibromide/8 mol % Pd(PPh3)4/2 equiv Cs2CO3/toluene/methanol.
(b) 8 mol % Pd(PPh3)4/2 equiv Ag2CO3/tetrahydrofuran.
a
Didebromination product.
Monocoupling and debromination product.
b
3. Conclusions
asymmetrically substituted p-terphenyls and hexa-p-phenylenes,
compounds of interest in the synthesis of giant tripod-shaped
molecules.
In summary, we studied the Suzuki cross-coupling reaction
behavior of p-dibromobiphenyl (1) showing that monocoupling is
preferentially obtained in good yields when the reaction is carried
out at room temperature. As expected, the selectivity does not
depend on the electronic or steric characteristics of the boronic
derivative, but better yields were obtained with arylboronic pinacol
ester derivatives. Suzuki cross coupling was also studied with
p-diiodoterphenyl (8) as the substrate. In this case only bis-coupled
products were obtained in good yields, showing that the coupling is
highly sensitive to the nature of the halogen involved. Finally, the
analysis was extended to substituted p-dibromo(penta-p-phenyl-
enes) (11 and 12) where monocoupling was found to be selective
when arylboronic pinacol esters were used at room temperature
with THF as the solvent. The results reported for the Suzuki mon-
ocoupling of 1, 11, and 12 provides a practical protocol for preparing
4. Experimental
4.1. General
p-Dibromobenzene (2), p-dibromobiphenyl (1), and arylboronic
acids and esters (3aef) were purchased from Aldrich, and they
were used without purification. p-Diiodoterphenyl (8) was pre-
pared from terphenyl following reported procedures.22 Melting
points were determined with a Gallenkamp instrument and are
given uncorrected. IR spectra were recorded on Beckman Aculab IV
and PerkineElmer 883 spectrophotometers. Mass spectrometry
was done with a Thermo Finnigan instrument, using the direct
injection and electron-impact (EI) modes. HRMS were recorded

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E. Guillen et al. / Tetrahedron 67 (2011) 2555e2561
2559
with a Micromass (Autospec-Q) spectrometer. 1H NMR and 13C
NMR spectra were recorded in a 400 MHz ARX 400 Bruker spec-
trometer, using the residual solvent peak in CDCl3 (dH 7.24 ppm for
1H and dC 77.0 ppm for 13C). TLC analyses were performed on Merck
silica gel 60 F254 plates, and column chromatography on silica gel 60
(0.040e0.063 mm).
116e118 ꢀC; 1H NMR (400 MHz, CDCl3)
7.50 (t, 2H, J1¼7.9 Hz, ArH), 7.36e7.44 (m, 3H, ArH), 7.10 (t, 1H,
J¼7.2 Hz, ArH), 7.05 (d, 1H, J¼8.4 Hz, ArH), 3.88 (s, 3H, OCH3) ppm;
MS m/z (%): 260 (Mþ, 100%), 245 (12), 227 (22), 215 (14).
d
: 7.67e7.71 (m, 6H, ArH),
4.2.5. 2-Cyano-p-terphenylene (6c)27. The reaction was carried out
by following the reflux-12 h procedure, using p-dibromobiphenyl
(1, 0.48 g, 1.54 mmol), 2-cyanophenyl boronic acid (3c, 0.15 g,
1.03 mmol), cesium carbonate (0.67 g, 2.06 mmol), Pd(PPh3)4
(0.10 g, 0.08 mmol), toluene (20 mL), and methanol (20 mL). Com-
pound 6c was isolated by column chromatography (silica gel, cy-
clohexane/AcOEt 9.8/0.2) as a white solid (0.11 g, 43% yield), mp:
4.2. General procedure for the Pd(PPh3)4 catalyzed coupling
reaction
Under an argon atmosphere, an oven-dried round bottom flask
was charged with the appropriate phenyl boronic acid [or ester]
(1.00 mmol), p-dihaloarene (1.50 mmol), cesium carbonate [or sil-
ver carbonate] (2.00 mmol), and Pd(PPh3)4 (8 mol %). The flask was
evacuated and re-filled with argon three times, then toluene/
methanol [or tetrahydrofuran] was added.
160e162 ꢀC; 1H NMR (400 MHz, CDCl3)
d: 7.77 (d, 1H, J¼7.6 Hz,
ArH), 7.71 (d, 2H, J¼8.4 Hz, ArH), 7.64 (d, 4H, J¼8 Hz, ArH), 7.56
(d, 1H, J¼7.6 Hz, ArH), 7.48e7.43 (m, 4H, ArH), 7.37 (dd, 1H, J¼7.6,
7.2 Hz, ArH) ppm; 13C NMR (100 MHz, CDCl3)
d: 145.0 (C), 141.5 (C),
The reaction mixture was heated to reflux for 12 h or stirred for
18 h at room temperature (see Tables 1e3). When the reaction was
complete (TLC), inorganic solids were removed by filtration
through Celite, and washed with several portions of dichloro-
methane. The organic filtrates were then concentrated to dryness.
The crude product was purified by column chromatography.
140.3 (C), 136.9 (C), 133.8 (CH), 132.8 (CH), 130.0 (CH), 129.1 (2ꢁCH),
128.8 (2ꢁCH), 127.6 (CH), 127.5 (2ꢁCH), 127.4 (2ꢁCH), 127.1 (CH),
118.8 (CN), 111.1 (C) ppm; IR (KBr)
255 (Mþ, 100), 254 (48).
n
: 2226 nCN cmꢂ1; MS m/z (%):
4.2.6. 4-Cyano-p-terphenylene (6d)28. The reaction was carried out
by following the reflux-12 h procedure, using p-dibromobiphenyl
(1, 0.73 g, 2.34 mmol), 4-cyanophenyl boronic acid (3d, 0.23 g,
1.56 mmol), cesium carbonate (1.00 g, 3.12 mmol), Pd(PPh3)4
(0.14 g, 0.13 mmol), toluene (20 mL), and methanol (20 mL). Com-
pound 6d was isolated by column chromatography (silica gel, cy-
clohexane/CH2Cl2 5/5) as a pale yellow solid (0.25 g, 62% yield), mp:
4.2.1. 4-Bromo-40-methoxybiphenyl (4)23. The reaction was carried
out by following the reflux-12 h procedure, using p-dibromo-
benzene (2, 0.50 g, 2.12 mmol), 4-methoxyphenyl boronic acid (3a,
0.22 g, 1.41 mmol), cesium carbonate (0.92 g, 2.82 mmol), Pd
(PPh3)4 (0.13 g, 0.11 mmol), toluene (20 mL), and methanol (10 mL).
Compound 4 was isolated by column chromatography (silica gel,
cyclohexane/AcOEt 8/2) as a white solid (0.31 g, 82% yield), mp:
195e197 ꢀC; 1H NMR (400 MHz, CDCl3)
(m, 4H, ArH), 7.40 (m, 1H, ArH), 7.29 (br s, 4H, ArH) ppm; IR (KBr)
: 2229 nCN cmꢂ1; MS m/z (%): 255 (Mþ, 100), 254 (10).
d: 7.73 (m, 4H, ArH), 7.66
143e145 ꢀC; 1H NMR (400 MHz, CDCl3)
8.8 Hz, ArH), 7.40 (d, 2H, J¼8.3 Hz, ArH), 6.97 (d, 2H, J¼8.8 Hz, ArH),
3.84 (s, 3H, OCH3) ppm; MS m/z (%): 264 (Mþ, 0.2), 262 (0.2), 184
(100), 169 (47), 152 (5).
d
: 7.53 (dd, 4H, J¼7.6,
n
4.2.7. 2,2000-Dimethoxy-p-quaterphenylene (7b)29. From the same
reaction where 6b was obtained, compound 7b was isolated as
a brown solid (60 mg, 24% yield); 1H NMR (400 MHz, CDCl3)
4.2.2. 4-Bromo-400-methoxy-p-terphenyl (5a)24. The reaction was
carried out by following the rt-18 h procedure, using p-dibromo-
biphenyl (1, 0.62 g, 1.98 mmol), 4-methoxyphenyl boronic acid
(3a, 0.20 g, 1.32 mmol), cesium carbonate (0.86 g, 2.64 mmol), Pd
(PPh3)4 (0.12 g, 0.11 mmol), toluene (20 mL), and methanol (20 mL).
Compound 5a was isolated by column chromatography (silica gel,
cyclohexane/AcOEt 9.8/0.2) as a white solid (0.42 g, 93% yield), mp:
d: 7.87e7.76 (m, 4H, ArH), 7.56e7.38 (m, 4H, ArH), 7.19e7.11 (m, 8H,
ArH), 3.92 (s, 6H, 2ꢁOCH3) ppm; MS m/z (%): 366 (100), 336 (12),
306 (28), 282 (13). This compound was also obtained in 4% yield
from the reaction where 5b was isolated (Table 1, entry 3).
4.2.8. 2,2000-Dicyano-p-quaterphenylene (7c). From the same re-
action where 6c was obtained, compound 7c was isolated as
a pale yellow solid (20 mg, 9% yield), mp: 167e170 ꢀC; 1H NMR
145e146 ꢀC; 1H NMR (400 MHz, CDCl3)
d: 7.63e7.60 (m, 4H, ArH),
7.56 (d, 4H, J¼8.4 Hz, ArH), 7.48 (d, 2H, J¼8.8 Hz, ArH), 6.98 (d, 2H,
J¼8.8 Hz, ArH), 3.85 (s, 3H, OCH3) ppm; MS m/z (%): 338 (Mþ, 0.1),
336 (0.1), 258 (100).
(400 MHz, CDCl3)
d
: 7.79 (d, 2H, J¼8.4 Hz), 7.77 (d, 4H J¼8 Hz),
7.67 (d, 4H, J¼8.0 Hz, ArH), 7.66 (dd, 2H, J¼7.6 Hz, ArH), 7.57 (d,
2H, J¼7.6 Hz, ArH), 7.46 (dd, 2H, J¼6.8, 7.2 Hz, ArH) ppm; 13C
NMR (100 MHz, CDCl3)
d
: 141.2 (2ꢁC), 137.9 (2ꢁC), 137.0 (2ꢁC),
4.2.3. 4-Methoxy-p-terphenyl (6a)25. The reaction was carried out
by following the reflux-12 h procedure, using p-dibromobiphenyl
(1, 1.86 g, 5.95 mmol), 4-methoxyphenyl boronic acid (3a, 0.60 g,
3.97 mmol), cesium carbonate (2.59 g, 7.94 mmol), Pd(PPh3)4
(0.37 g, 0.32 mmol), toluene (30 mL), and methanol (20 mL).
Compound 6a was isolated by column chromatography (silica gel,
cyclohexane/CH2Cl2 8/2) as a white solid (0.86 g, 83% yield), mp:
134.5 (2ꢁCH), 133.9 (2ꢁCH), 129.0 (8ꢁCH), 128.1 (2ꢁCH), 128.0
(2ꢁCH), 118.1 (2ꢁCN), 107.9 (2ꢁC) ppm; IR (KBr)
n: 2224
nCN cmꢂ1; MS m/z (%): 356 (Mþ, 100), 178 (23), 164 (13); HRMS
calcd for C26H16N2: 356.1313, Found: 356.1314. This compound
was also obtained in 22% yield from the reaction where 5c was
isolated (Table 1, entry 7).
222e224 ꢀC; 1H NMR (400 MHz, CDCl3)
d: 7.63 (m, 4H, ArH), 7.57
4.2.9. 4,4000-Dicyano-p-quaterphenylene (7d/7e)5. From the same
reaction where 6d was obtained, compound 7d was isolated as
a white solid (44 mg,16% yield), mp: 185 ꢀC dec; 1H NMR (400 MHz,
(d, 2H, J¼8.8 Hz, ArH), 7.45 (d, 2H, J¼7.2 Hz, ArH), 7.43 (d, 2H,
J¼8 Hz, ArH), 7.35 (q, 1H, J¼7.2 Hz, ArH), 6.98 (d, 2H, J¼8.4 Hz, ArH),
3.85 (s, 3H, OCH3) ppm; MS m/z (%): 260 (100), 246 (8), 245 (42).
CDCl3)
(100 MHz, CDCl3)
(4ꢁCH),127.7 (4ꢁCH) 127.6 (8ꢁCH),118.9 (2ꢁCN),111.0 (2ꢁC) ppm;
IR (KBr)
: 2224 nCN cmꢂ1; MS m/z (%): 356 (Mþ, 100), 178 (15), 152
d
: 7.74e7.76 (m, 8H, ArH), 7.70 (br s, 8H, ArH) ppm; 13C NMR
d: 144.9 (2ꢁC), 140.5 (2ꢁC), 138.4 (2ꢁC), 132.7
4.2.4. 2-Methoxy-p-terphenyl (6b)26. The reaction was carried out
by following the reflux-12 h procedure, using p-dibromobiphenyl
(1, 0.62 g, 1.98 mmol), 2-methoxyphenyl boronic acid (3b, 0.20 g,
1.32 mmol), cesium carbonate (0.86 g, 2.64 mmol), Pd(PPh3)4
(0.12 g, 0.11 mmol), toluene (20 mL), and methanol (20 mL). Com-
pound 6b was isolated by column chromatography (silica gel, cy-
clohexane/AcOEt 9.8/0.2) as a white solid (0.27 g, 61% yield), mp:
n
(11). This compound was obtained in 25% and 11% yields from the
reactions where 5d and 5e was isolated (Table 1, entries 9 and 10).
4.2.10. 400-Bromo-2-methoxy-p-terphenyl (5b). The reaction was
carried out by following the rt-18 h procedure, using p-

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E. Guillen et al. / Tetrahedron 67 (2011) 2555e2561
2560
dibromobiphenyl (1, 1.00 g, 3.19 mmol), 2-methoxyphenyl boronic
acid (3b, 0.32 g, 2.13 mmol), cesium carbonate (1.39 g, 4.26 mmol),
Pd(PPh3)4 (0.20 g, 0.17 mmol), toluene (50 mL), and methanol
(50 mL). Compound 5b was isolated by column chromatography
(silica gel, cyclohexane/AcOEt 9.8/0.2) as a white solid (0.42 g, 58%
145.7 (2ꢁC), 140.1 (4ꢁC), 130.2 (4ꢁCH), 129.0 (4ꢁCH), 128.2 (2ꢁC),
127.4 (4ꢁCH), 127.2 (4ꢁCH), 52.2 (OCH3); IR (KBr)
n ;
: 1734 nCO cmꢂ1
MS m/z (%): 422 (Mþ, 25).
4.2.15. 4,40000-Dibromo-2,20000,5,50000-tetramethyl-(penta-p-phenylene)
(11). The reaction was carried out by following the reflux-12 h pro-
cedure, using p-diiodoterphenyl (8, 0.50 g,1.00 mmol), boronic acid 9
(0.16 g, 0.69 mmol), cesium carbonate (0.45 g, 1.38 mmol), Pd(PPh3)4
(0.064 g, 0.055 mmol), toluene (10 mL), and methanol (10 mL).
Compound 11 was isolated by column chromatography (silica gel,
cyclohexane/CH2Cl2 5/5) as a pale yellow solid (0.19 g, 94% yield), mp:
yield), mp: 205e210 ꢀC; 1H NMR (400 MHz, CDCl3)
d: 7.69e7.51
(m, 8H, ArH), 7.43e7.36 (m, 2H, ArH), 7.14e7.03 (m, 2H, ArH), 3.88 (s,
3H, OCH3) ppm; MS m/z (%): 340 (5), 338 (6), 260 (100); 13C NMR
(100 MHz, CDCl3) d: 154.0 (C), 140.10 (C), 140.07 (C), 137.0 (C), 132.0
(C),131.0 (CH),130.6 (CH),130.5 (CH),127.9 (CH),127.5 (2ꢁCH),127.1
(2ꢁCH), 122.4 (2ꢁCH),122.3 (CH), 122.1 (C), 115.2 (CH), 58.0 (OCH3)
ppm; HRMS calcd for C19H15BrO: 338.0306, Found: 338.0312.
256e260 ꢀC; 1H NMR (400 MHz, CDCl3)
d: 7.73 (s, 4H, ArH), 7.68 (d,
4H, J¼8.3 Hz, ArH), 7.46 (s, 2H, ArH), 7.37 (d, 4H, J¼8.3 Hz, ArH), 7.14 (s,
4.2.11. 400-Bromo-2-cyano-p-terphenylene (5c). The reaction was
carried out by following the rt-18 h procedure, using p-dibromobi-
phenyl (1, 0.48 g,1.54 mmol), 2-cyanophenyl boronic acid (3c, 0.15 g,
1.03 mmol), cesium carbonate (0.67 g, 2.06 mmol), Pd(PPh3)4
(0.10 g, 0.08 mmol), toluene (20 mL), and methanol (20 mL). Com-
pound 5c was isolated by column chromatography (silica gel, cy-
clohexane/AcOEt 9.8/0.2) as a white solid (0.21 g, 61% yield), mp:
2H, ArH), 2.39 (s, 6H, 2ꢁCH3), 2.26 (s, 6H, 2ꢁCH3) ppm; 13C NMR
(100 MHz, CDCl3)
d
: 140.6 (2ꢁC), 140.0 (2ꢁC), 139.7 (2ꢁC), 139.3
(2ꢁC), 135.1 (2ꢁC), 134.7 (2ꢁC), 133.8 (2ꢁCH), 132.0 (2ꢁCH), 129.5
(4ꢁCH), 127.4 (4ꢁCH), 126.7 (4ꢁCH), 123.6 (2ꢁC), 22.3 (2ꢁCH3), 19.8
(2ꢁCH3); HRMS calcd for C34H28Br2: 594.0558, Found: 594.0555.
4.2.16. 4,40000-Dibromo-2,20000,5,50000-tetramethoxy-(penta-p-phenyl-
ene) (12). The reaction was carried out by following the reflux-12 h
procedure, using p-diiodoterphenyl (8, 0.50 g, 1.00 mmol), boronic
acid 10 (0.18 g, 0.69 mmol), cesium carbonate (0.45 g, 1.38 mmol),
Pd(PPh3)4 (0.064 g, 0.055 mmol), toluene (10 mL), and methanol
(10 mL). Compound 12 was isolated by column chromatography
(silica gel, cyclohexane/CH2Cl2 5/5) as a pale yellow solid (0.20 g,
120e123 ꢀC; 1H NMR (400 MHz, CDCl3)
4H, ArH), 7.58 (d, 2H, J¼8.4 Hz, ArH), 7.49(d, 2H, J¼8.4 Hz, ArH) ppm;
13C NMR (100 MHz, CDCl3)
: 95.1, 96.8, 99.0,102.7,111.4,111.5,113.2,
d: 7.73 (m, 4H, ArH), 7.66 (s,
d
113.9,116.8,117.7,121.2,124.6,128.8 ppm; IR (KBr) n ;
: 2224 nCN cmꢂ1
MS m/z (%): 335 (Mþ, 83), 333 (100), 255 (26), 254 (54), 253 (42);
HRMS calcd for C19H12BrN: 333.0153, Found: 333.0150.
90% yield), mp: >300 ꢀC; 1H NMR (400 MHz, CDCl3)
d: 7.72 (s, 4H,
4.2.12. 400-Bromo-4-cyano-p-terphenylene (5d/5e)5. The reaction
was carried out by following the rt-12 h procedure, using
p-dibromobiphenyl (1, 0.54 g, 1.73 mmol), 4-cyanophenyl boronic
acid pinacol ester (3e, 0.26 g, 1.15 mmol), silver carbonate (0.91 g,
3.30 mmol), Pd(PPh3)4 (0.11 g, 0.09 mmol), and tetrahydrofuran
(50 mL). Compound 5e was isolated by column chromatography
(silica gel, cyclohexane/AcOEt 9.8/0.2) as a white solid (0.30 g, 78%
ArH), 7.69 (d, 4H, J¼8.2 Hz, ArH), 7.60 (d, 4H, J¼8.2 Hz, ArH), 7.19
(s, 2H, ArH), 6.95 (s, 2H, ArH), 3.89 (s, 6H, 2ꢁOCH3), 3.79 (s, 6H,
2ꢁOCH3) ppm; 13C NMR (100 MHz, CDCl3)
: 150.9 (2ꢁC), 150.3
d
(2ꢁC), 139.71 (4ꢁC), 139.69 (2ꢁC), 136.8 (2ꢁC), 129.8 (4ꢁCH), 127.5
(4ꢁCH), 126.5 (4ꢁCH),117.7 (2ꢁCH), 114.0 (2ꢁCH), 110.6 (2ꢁC), 57.0
(2ꢁOCH3), 56.5 (2ꢁOCH3); HRMS calcd for C34H28Br2O4: 658.0354,
Found: 658.0359.
yield), mp: 115e120 ꢀC; 1H NMR (400 MHz, CDCl3)
ArH), 7.66 (s, 4H, ArH), 7.58 (d, 2H, J¼8.4 Hz), 7.49 (d, 2H, J¼8.4 Hz)
ppm; IR (KBr)
: 2229 nCN cmꢂ1; MS m/z (%): 335 (Mþ, 96), 333
d: 7.73 (m, 4H,
4.2.17. 2,20000,5,50000-Tetramethoxy-(penta-p-phenylene) (13). The re-
action was carried out by following the reflux-12 h procedure, us-
ing 12 (0.12 g, 0.18 mmol), 4-methoxyphenyl boronic acid (3a,
0.018 g, 0.12 mmol), cesium carbonate (0.078 g, 0.24 mmol), Pd
(PPh3)4 (0.011 g, 0.010 mmol), toluene (18 mL), and methanol
(15 mL). Compound 13 was isolated by column chromatography
(silica gel, cyclohexane/AcOEt 9.8/0.2) as a white solid (0.048 g, 80%
n
(100), 255 (1), 254 (10), 253 (30).
Compound 5d was also obtained by following the rt-18 h pro-
cedure, using p-dibromobiphenyl (1, 0.48 g, 1.54 mmol), 4-cyano-
phenyl boronic acid (3d, 0.15 g, 1.03 mmol), cesium carbonate
(0.67 g, 2.06 mmol), Pd(PPh3)4 (0.10 g, 0.08 mmol), toluene (20 mL),
and methanol (20 mL). Compound 5d was isolated by column
chromatography (silica gel, cyclohexane/AcOEt 9.8/0.2) as a white
solid (0.26 g, 69% yield).
yield), mp: 220e225 ꢀC; 1H NMR (400 MHz, CDCl3)
d: 7.72 (s, 4H,
ArH), 7.69 (d, 4H, J¼8.4 Hz, ArH), 7.62 (d, 4H, J¼8.4 Hz, ArH),
6.97e6.83 (m, 6H, ArH), 3.79 (s, 6H, 2ꢁOCH3), 3.76 (s, 6H, 2ꢁOCH3)
ppm; 13C NMR (100 MHz, CDCl3)
d
: 153.8 (2ꢁC), 150.8 (2ꢁC), 139.8
4.2.13. 400-Bromo-4-methoxycarbonyl-p-terphenylene (5f). The re-
action was carried out by following the rt-12 h procedure, using
p-dibromobiphenyl (1, 0.40 g, 1.28 mmol), 4-(methoxycarbonyl)
phenyl boronic acid pinacol ester (3f, 0.22 g, 0.85 mmol), silver
carbonate (0.47 g, 1.70 mmol), Pd(PPh3)4 (0.08 g, 0.07 mmol), and
tetrahydrofuran (40 mL). Compound 5f was isolated by column
chromatography (silica gel, cyclohexane/AcOEt 9.8/0.2) as a white
solid (0.17 g, 56% yield), mp: 120e123 ꢀC; 1H NMR (400 MHz,
(2ꢁC), 139.4 (2ꢁC), 137.4 (2ꢁC), 131.1 (2ꢁC), 129.9 (4ꢁCH), 127.5
(4ꢁCH), 126.7 (4ꢁCH), 116.6 (2ꢁCH), 113.2 (2ꢁCH), 112.6 (2ꢁCH),
56.5 (2ꢁOCH3), 56.2 (2ꢁOCH3); HRMS calcd for C34H30O4:
502.2144, Found: 502.2147.
4.2.18. 20,200000,4,50,500000-Pentamethoxy-(hexa-p-phenylene)
(14). From the same reaction as for 13, compound 14 was isolated
as a yellowish syrup (0.010 g, 14% yield); 1H NMR (400 MHz, CDCl3)
CDCl3)
d
: 8.09 (d, 2H, J¼8.2 Hz, ArH), 7.70e7.46 (m, 10H, ArH), 3.93
d
: 7.73e7.52 (m, 15H, ArH), 7.02e6.87 (m, 6H, ArH), 3.85 (s, 3H,
OCH3), 3.82 (s, 3H, OCH3), 3.82 (s, 3H, OCH3), 3.80 (s, 3H, OCH3),
3.79 (s, 3H, OCH3) ppm; 13C NMR (100 MHz, CDCl3)
: 159.1 (C),
(s, 3H, COOCH3) ppm; 13C NMR (100 MHz, CDCl3)
d
: 167.0 (CO),
142.2 (C), 140.1 (C), 140.0 (2ꢁC), 131.3 (2ꢁCH), 127.3 (C), 127.2
(2ꢁCH), 127.0 (2ꢁCH), 126.9 (4ꢁCH), 121.0 (C), 120.8 (2ꢁCH), 58.0
d
154.1 (C), 151.1 (3ꢁC), 140.1 (4ꢁC), 139.7 (C), 137.8 (2ꢁC), 131.4
(2ꢁC), 130.8 (C), 130.2 (CH), 129.7 (CH), 127.8 (2ꢁCH), 127.7 (4ꢁCH),
127.1 (2ꢁCH), 127.0 (4ꢁCH), 116.9 (CH), 114.9 (CH), 114.8 (CH), 113.9
(CH), 113.5 (CH), 112.9 (2ꢁCH), 56.8 (OCH3), 56.7 (OCH3), 56.6
(OCH3), 56.1 (OCH3), 55.6 (OCH3) ppm; HRMS calcd for C41H36O5:
608.2563, Found: 608.2565.
(OCH3); IR (KBr) n
: 1734 nCO cmꢂ1; HRMS calcd for C20H15BrO2:
366.0255, Found: 366.0257.
4.2.14. 4,400-Di(methoxycarbonyl)-p-quaterphenylene (7f)30. From
the same reaction as for 5f, compound 7f was isolated as a white
solid (9 mg, 5% yield); 1H NMR (400 MHz, CDCl3)
d
: 8.11 (d, 4H,
J¼8.0 Hz, ArH), 7.71e7.60 (m, 8H, ArH), 7.53e7.40 (m, 4H, ArH), 3.93
(s, 6H, COOCH3) ppm; 13C NMR (100 MHz, CDCl3)
: 167.1 (2ꢁCO),
4.2.19. 400000-Bromo-20,200000,5’,500000-tetramethoxy-4-methoxycarbonyl-
(hexa-p-phenylene) (15). The reaction was carried out by following
d

ꢀ
E. Guillen et al. / Tetrahedron 67 (2011) 2555e2561
2561
the rt-12 h procedure, using 12 (0.20 g, 0.30 mmol), 4-(methox-
ycarbonyl)phenyl boronic acid pinacol ester (3f, 0.052 g, 0.20
mmol), silver carbonate (0.11 g, 0.40 mmol), Pd(PPh3)4 (0.018 g,
0.016 mmol), and tetrahydrofuran (50 mL). Compound 15 was iso-
lated by column chromatography (silica gel, cyclohexane/AcOEt 9.2/
0.8) as a white solid (0.30 g, 78% yield), mp: 230 ꢀC dec; 1H NMR
n
: 2220 nCN cmꢂ1; HRMS calcd for C41H32BrNNa: 640.1616, Found:
640.1623.
Acknowledgements
This work was funded by the Spanish Ministerio de Ciencia
(400 MHz, CDCl3)
d: 8.10 (d, 2H, J¼8.4 Hz, ArH), 7.73e7.66 (m, 12H,
ꢀ
e Innovacion (Project Number CTQ2010-17633).
ArH), 7.61 (d, 2H, J¼8 Hz, ArH), 7.19 (s,1H, ArH), 7.04 (s,1H, ArH), 6.99
(s, 1H, ArH), 6.95 (s, 1H, ArH), 3.94 (s, 3H, OCH3), 3.90 (s, 3H, OCH3),
3.83 (s, 3H, OCH3), 3.81 (s, 3H, OCH3), 3.79 (s, 3H, OCH3) ppm; 13C
Supplementary data
NMR (100 MHz, CDCl3) d: 168.5 (CO), 150.9 (C), 150.8 (C), 150.7 (C),
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.tet.2011.02.025.
150.4 (C), 143.0 (C), 139.9 (C), 139.7 (C), 139.6 (2ꢁC), 137.2 (2ꢁC),
136.8 (2ꢁC), 129.9 (2ꢁCH), 129.8 (C), 129.5 (3ꢁCH), 129.4 (3ꢁCH),
127.5 (3ꢁCH), 126.8 (3ꢁCH), 117.0 (CH), 114.8 (2ꢁCH), 114.7 (2ꢁCH),
114.5 (C), 57.0 (2ꢁOCH3), 56.5 (OCH3), 56.5 (OCH3), 52.1 (OCH3)
References and notes
ppm; IR (KBr) n
: 1729 nCO cmꢂ1; HRMS calcd for C42H35BrO6Na:
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(hexa-p-phenylene) (16). The reaction was carried out by following
the rt-12 h procedure, using 11 (0.46 g, 0.77 mmol), 4-(methox-
ycarbonyl)phenyl boronic acid pinacol ester (3f, 0.135 g, 0.51
mmol), silver carbonate (0.28 g, 1.02 mmol), Pd(PPh3)4 (0.047 g,
0.041 mmol), and tetrahydrofuran (50 mL). Compound 16 was
isolated by column chromatography (silica gel, cyclohexane/CH2Cl2
9/1) as a white solid (0.18 g, 54% yield), mp: >300 ꢀC dec; 1H NMR
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(400 MHz, CDCl3)
d
: 8.09 (d, 2H, J¼8.6 Hz, ArH), 7.75 (s, 4H, ArH),
7.71e7.70 (m, 4H, ArH), 7.48e7.43 (m, 5H, ArH), 7.37 (d, 2H,
J¼8.6 Hz, ArH), 7.22 (s, 1H, ArH), 7.17 (s, 1H, ArH), 7.14 (s, 1H, ArH),
3.94 (s, 3H, COOCH3), 2.39 (s, 3H, CH3), 2.34 (s, 3H, CH3), 2.30 (s, 3H,
11. Park, M.-H.; Ryu, J.-Y.; Lee, E.; Han, K.-H.; Chung, Y.-W.; Cho, B.-K.; Lee, M.
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CH3), 2.26 (s, 3H, CH3) ppm; 13C NMR (100 MHz, CDCl3)
d: 168.4
ꢀ
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13. Hierrezuelo, J.; Guillen, E.; Lopez-Romero, J. M.; Rico, R.; Lopez-Ramírez, M. R.;
(CO), 142.0 (C), 139.5 (C), 138.9 (C), 138.7 (C), 138.5 (C), 136.1 (2ꢁC),
135.70 (C),135.69 (C),133.9 (2ꢁC),132.8 (C),131.7 (C),130.2 (2ꢁCH),
129.9 (C), 129.8 (3ꢁCH), 129.0 (3ꢁCH), 128.1 (3ꢁCH), 126.1 (3ꢁCH),
119.5 (CH), 117.8 (2ꢁCH), 114.9 (2ꢁCH), 114.5 (C), 52.0 (OCH3), 29.2
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(CH3), 23.5 (CH3), 19.5 (CH3), 14.2 (CH3) ppm; IR (KBr) n: 1730
nCO cmꢂ1
673.1720.
; HRMS calcd for C42H35BrO2Na: 673.1718, Found:
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4.2.21. 400000-Bromo-4-cyano-20,200000,50,500000-tetramethyl-(hexa-p-phe-
nylene) (17). The reaction was carried out by following the rt-12 h
procedure, using 11 (0.52 g, 0.87 mmol), 4-cyanophenyl boronic
acid pinacol ester (3e, 0.133 g, 0.58 mmol), silver carbonate (0.32 g,
1.16 mmol), Pd(PPh3)4 (0.054 g, 0.046 mmol), and tetrahydrofuran
(50 mL). Compound 17 was isolated by column chromatography
(silica gel, cyclohexane/CH2Cl2 9/1) as a white solid (0.20 g, 55%
20. (a) Smyth, L. A.; Matthews, T. P.; Horton, P. N.; Hursthouse, M. B.; Collins, I.
Tetrahedron 2010, 66, 2843e2854; (b) Balaban, T. S.; Goddard, R.; Linke-
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yield), mp: >300 ꢀC dec; 1H NMR (400 MHz, CDCl3)
d: 7.76e7.67 (m,
12H, ArH), 7.48 (d, 2H, J¼8.2 Hz, ArH), 7.45 (d, 2H, J¼8.2 Hz, ArH),
7.39 (s, 1H, ArH), 7.35 (s, 1H, ArH), 7.14 (s, 1H, ArH), 7.13 (s, 1H, ArH),
2.39 (s, 3H, CH3), 2.34 (s, 3H, CH3), 2.26 (s, 6H, 2ꢁCH3) ppm; 13C
NMR (100 MHz, CDCl3)
d
: 143.6 (C), 139.8 (2ꢁC), 139.4 (2ꢁC), 133.9
(C), 133.2 (2ꢁC), 133.0 (2ꢁC), 132.5 (C), 132.3 (C), 132.1 (2ꢁCH),
131.7 (2ꢁC), 130.1 (2ꢁCH), 129.7 (2ꢁCH), 129.6 (6ꢁCH), 128.0
(4ꢁCH), 127.6 (2ꢁCH), 126.9 (2ꢁCH), 120.0 (C), 118.5 (CN), 112.6 (C),
30.4 (CH3), 22.4 (CH3), 19.9 (CH3), 14.2 (CH3) ppm; IR (KBr)