Rhodium-catalyzed regioselective arylation of phenylazoles and related compounds with arylboron reagents via C-H bond cleavage

Article abstract of DOI:10.1016/j.jorganchem.2008.04.029

The rhodium-catalyzed direct ortho-arylation reactions of phenylazoles using arylboron reagents such as tetraarylborates were examined. Ethyl chloroacetate and potassium fluoride were found to effectively act as a hydrogen acceptor and a promoter, respectively, to afford selective formation of the corresponding mono- or diarylated products with good yields. In addition, azobenzene as well as 2-phenylpyridine also underwent the direct arylation under similar conditions.

Full text of DOI:10.1016/j.jorganchem.2008.04.029

Journal of Organometallic Chemistry 693 (2008) 2438–2442
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Journal of Organometallic Chemistry
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Rhodium-catalyzed regioselective arylation of phenylazoles and related
compounds with arylboron reagents via C–H bond cleavage
*
*
Sawako Miyamura, Hayato Tsurugi, Tetsuya Satoh , Masahiro Miura
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The rhodium-catalyzed direct ortho-arylation reactions of phenylazoles using arylboron reagents such as
tetraarylborates were examined. Ethyl chloroacetate and potassium fluoride were found to effectively act
as a hydrogen acceptor and a promoter, respectively, to afford selective formation of the corresponding
mono- or diarylated products with good yields. In addition, azobenzene as well as 2-phenylpyridine also
underwent the direct arylation under similar conditions.
Received 24 March 2008
Received in revised form 23 April 2008
Accepted 24 April 2008
Available online 30 April 2008
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Rhodium catalyst
Arylation
Arylboron compounds
C–H activation
Phenylazoles
Azobenzene
1. Introduction
byproduct. Actually, formation of a significant amount of the amine
was observed in the reaction.
Transition-metal-catalyzed cross-coupling of arylmetal re-
agents (metal = Mg, Zn, B, Sn, Si, etc.) with aryl halides are now rec-
ognized to be one of the most useful methods for constructing
biaryls [1], whose skeletons are found in a wide range of important
compounds including natural products and organic functional
materials [2–4]. Particularly, the palladium-catalyzed coupling of
non-toxic, readily available arylboron reagents with aryl halides
(Suzuki-Miyaura coupling) is very often employed [1,5,6].
Obviously, the direct arylation of arenes with arylboron re-
agents, in which prehalogenation of the arene coupling partners
is not required, may provide a straightforward and environmen-
tally benign method for biaryl synthesis [7–14]. As an example
for the direct reaction, we have reported the multiple phenylation
of benzonitrile using sodium tetraphenylborate under rhodium
catalysis (Scheme 1) [15,16]. In this reaction, benzophenone imine,
generated initially through nucleophilic phenylation on the C–N
triple bond of benzonitrile, is considered to undergo the subse-
quent coordination-assisted ortho-phenylation via C–H bond cleav-
age to form multiply phenylated products, as depicted in Scheme 2.
According to this reaction scheme, however, 1 equivalent of benzo-
phenone imine is consumed as a hydrogen acceptor for the C–H
phenylation to form (diphenylmethyl)amine (Ph2CHNH2) as a
To suppress the undesired consumption of the imine intermedi-
ate, addition of ethyl a-chloroacetate as a hydrogen acceptor was
examined. a-Chloroacetyl compounds have been employed as
reoxidants in the palladium-catalyzed oxidative coupling reactions
of organometallic reagents with alkenes [17,18]. As a model sub-
strate, cyclohexanecarbonitrile was used, because the product mix-
ture would be simpler than that with benzonitrile. Thus, the
aliphatic nitrile was treated with sodium tetraphenylborate using
[RhCl(cod)]2 as a catalyst in o-xylene in the presence or absence
of ClCH2CO2Et, and (biphenyl-2-yl) cyclohexyl ketone was
obtained as a major product after hydrolysis with aq. HCl (Scheme
3) [19]. Expectedly, the addition of the hydrogen acceptor
increased the yield of the diphenylated product from 14% to 53%
without forming any amines. While efficiency of the reaction could
not be further improved, the catalyst system using the hydrogen
acceptor was found to be applicable to the direct arylation of other
substrates such as phenylazoles and related compounds. The find-
ings are described herein.
2. Results and discussion
In an initial attempt, 1-methyl-2-phenylimidazole (1)
(0.5 mmol) was treated with sodium tetraphenylborate (2a)
(0.5 mmol) in the presence of [RhCl(cod)]2 (cod = 1,5-cyclooctadi-
ene) (0.005 mmol) and ClCH2CO2Et (0.5 mmol) in o-xylene at
120 °C for 6 h under nitrogen. As a result, the ortho-phenylated
* Corresponding authors. Tel.: +81 6 6879 7361; fax: +81 6 6879 7362.
E-mail addresses: satoh@chem.eng.osaka-u.ac.jp (T. Satoh), miura@chem.eng.
osaka-u.ac.jp (M. Miura).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.04.029

S. Miyamura et al. / Journal of Organometallic Chemistry 693 (2008) 2438–2442
2439
[RhCl(cod)]2 (0.005 mmol)
KF (1 mmol)
Ph
N
N
N
N
Me
Me
NaBAr4
+
[RhCl(cod)]2
dppp
NH
Ph
Ar
Ph
ClCH2CO2Et (1 mmol)
2b, c
-xylene, 120 oC, 6 h
+
PhCN
NH
Ph2C
NaBPh4
o
(1 mmol)
NH
NH4Cl
1 (0.25 mmol)
Ph
3b, c
further
2
Product, Yield (%)a
phenylated
products
+
2b: Ar = 4-CH3C6H4
2c: Ar = 4-FC6H4
3b: Ar = 4-CH3C6H4, 88
3c: Ar = 4-FC6H4, 21
Scheme 1. Reaction of benzonitrile with sodium tetraphenylborate.
a Isolated yield.
Scheme 4. Reaction of 1 with sodium tetraarylborates 2.
Ph
Ph2C NH
Ph2C NH
NaBPh4
N
H
Rh-Cl
Rh-Ph
-BPh3, -NaCl
Rh
H
Me
N
Ph
Ph
Ph
NaBAr4
NH4Cl
-Ph2CHNH2
Ph
2
1
NH
N
Rh
H
Rh-X
Rh-Ar
H
-BAr3, -NaX
Rh-H
N
Ph
H
Ar
Me
Rh
N
-HCl or -CH3CO2Et
N
Scheme 2. Proposed mechanism for the C–H phenylation of benzophenone imine.
ClCH2CO2Et
Cl-Rh-H
CH2CO2Et
Rh-H
Ar
3
[RhCl(cod)]2 (0.005 mmol)
ClCH2CO2Et (1 mmol)
Scheme 5. Plausible mechanism for the C–H arylation of 1.
NH
+
CN
NaBPh4
o
-xylene, 120 oC, 6 h
cantly improved the yield to 46% (Entry 2). [Rh(OMe)(cod)]2
showed comparable activity to that of [RhCl(cod)]2, while Rh-
(acac)(cod) was less effective (Entries 3 and 4). At 140 °C, the yield
was somewhat decreased (Entry 5). Finally, under the conditions
using excess amounts of 2a and the additives, 3a was produced
in 92% yield (Entry 6). The phenylation with phenylboronic acid
(4a) in place of 2a proceeded to some extent, albeit sluggishly
(Entry 7).
Under the optimized conditions (Entry 6 in Table 1), sodium tet-
rakis(4-methylphenyl)borate (2b) reacted with 1 to give the corre-
sponding ortho-arylated product 3b in 88% isolated yield (Scheme
4). Sodium tetrakis(4-fluorophenyl)borate (2c) also underwent the
reaction with 1, although the yield of product 3c was low.
A plausible mechanism for the reaction of azole 1 with borate 2
is illustrated in Scheme 5. The reaction proceeds via C–H activation
(1 mmol)
(0.5 mmol)
O
aq. HCl (3 M)
100 oC, 4 h
53%a
14%a
without ClCH2CO2Et
Scheme 3. Reaction of cyclohexanecarbonitrile with sodium tetraphenylborate.
aYield based on the amount of NaBPh4 used.
product, 2-(biphenyl-2-yl)-1-methylimidazole (3a), was formed in
16% yield (Entry 1 in Table 1). Addition of KF (0.5 mmol) signifi-
Table 1
Reaction of 1-methyl-2-phenylimidazole (1) with sodium tetraphenylborate (2a)a
Rh-cat.
KF
N
N
N
N
Me
Me
NaBPh4
+
ClCH2CO2Et
o-xylene
2a
1
3a
Entry
1 (mmol)
2a (mmol)
Rh-cat. (mmol)
Temperature (°C)
Yield of 3a (%)b
lc
2
3
0.5
0.5
0.5
0.5
0.5
0.25
0.25
0.5
0.5
0.5
0.5
0.5
1
[RhCl(cod)]2 (0.005)
[RhCl(cod)]2 (0.005)
[Rh(OMe)(cod)]2 (0.005)
Rh(acac)(cod) (0.01)
[RhCl(cod)]2 (0.005)
[RhCl(cod)]2 (0.005)
[RhCl(cod)]2 (0.005)
120
120
120
120
140
120
120
16
46
41
23
35
92 (92)
17
4
5
6d
7e
1
a
Reaction conditions: KF (0.5 mmol), ClCH2CO2Et (0.5 mmol) in o-xylene (5 mL) for 6 h under N2.
GC yield based on the amount of 1 used. Value in parentheses indicates isolated yield.
Without KF.
KF (1 mmol) and ClCH2CO2Et (1 mmol) were used.
PhB(OH)2 (4a) (1 mmol) was used in place of 2a.
b
c
d
e

2440
S. Miyamura et al. / Journal of Organometallic Chemistry 693 (2008) 2438–2442
Oxidative addition of ClCH2CO2Et to the latter and reductive elim-
ination of HCl or CH3CO2Et may occur to regenerate Rh(I)X. It is ci-
ted that pinacolone [8] and tetrachloroethane solvents [14] were
reported to act as hydrogen acceptors in relevant catalytic direct
arylations. Use of TEMPO was also described very recently [13].
Although the significant promoting effect of KF was observed, the
exact role of the additive is not definitive at the present stage.
Next, the phenylation of other phenylazoles with 2a by using
the catalyst system of [RhCl(cod)]2/ClCH2CO2Et/KF was examined.
1-Methyl-2-phenylbenzimidazole (5) underwent the reaction
effectively to afford the product 6 in 64% yield (Scheme 6).
Sterically less demanding 1-phenylpyrazole (7) and 2-phenyl-2-
oxazoline (9), compared with phenylimidazoles 1 and 5, reacted
with 2a to give the corresponding diphenylated products, 8 and
10, respectively, in good yields (Schemes 7 and 8). In these reac-
tions, formation of monophenylated products could not be
detected. In the case of 7, the reaction took place efficiently with-
out adding KF. It is cited that related mono- and diarylation reac-
tions of these substrates with aryl halides or tosylates have been
reported [20–23].
[RhCl(cod)]2 (0.005 mmol)
KF (1 mmol)
N
N
N
N
Me
Me
NaBPh4
+
ClCH2CO2Et (1 mmol)
o-xylene, 140 oC, 6 h
2a
(1 mmol)
6, 64%a
5 (0.25 mmol)
Scheme 6. Reaction of 1-methyl-2-phenylbenzimidazole (5) with 2a. aIsolated
yield.
N
N
[RhCl(cod)]2 (0.005 mmol)
ClCH2CO2Et (1 mmol)
N
N
NaBPh4
+
2a
o
-xylene, 140 oC, 6 h
(1 mmol)
8, 98%a
7 (0.25 mmol)
Scheme 7. Reaction of 1-phenylpyrazole (7) with 2a. aIsolated yield.
For the phenylation of 2-phenylpyridine (11), which is often
examined as
a substrate for C–H functionalizations [13,14,
[RhCl(cod)]2 (0.005 mmol)
O
N
21–23], addition of P(biphenyl-2-yl)(But)2 as a ligand led to a bet-
ter yield of product 12 (47%) (Scheme 9). The yield was reduced to
30% without using the ligand.
O
N
KF (1 mmol)
NaBPh4
+
ClCH2CO2Et (1 mmol)
2a
o
-xylene, 140 oC, 6 h
(1 mmol)
It was of considerable interest that phenylation of azobenzene
(13) could also be conducted by the present method (Table 2), as
no report on the transition-metal-catalyzed C–H arylation of 13 as
well as 1 and 5 has to date appeared. Thus, treatment of 13
(0.25 mmol) using excess amounts of 2a, ClCH2CO2Et, and KF in
the presence of [RhCl(cod)]2 gave a diphenylated product 14a
in 15% yield (Entry 1). Since a comparable result was obtained in
the reaction of 13 with phenylboronic acid (4a) (Entry 2), 4a
was employed for further examinations. [Rh(OMe)(cod)]2 was
found to be more effective as a catalyst than [RhCl(cod)]2 and
Rh(acac)(cod) (Entries 2–4). The yield of 14a was enhanced up
to 50%, when the amount of KF was increased to 2 mmol (Entry 5).
Under the same conditions, the reactions of 13 with 4-methyl-
(4b) and 4-chlorophenyl boronic acids (4c) also took place to afford
the corresponding diarylated products 14b and 14c, respectively,
in moderate yields (Scheme 10).
9 (0.25 mmol)
10, 71%a
Scheme 8. Reaction of 2-phenyl-2-oxazoline (9) with 2a. aIsolated yield.
[RhCl(cod)]2 (0.005 mmol)
N
N
P(biphenyl-2-yl)(But)2 (0.02 mmol)
NaBPh4
+
ClCH2CO2Et (1 mmol)
o-xylene, 140 oC, 6 h
2a
(0.5 mmol)
12, 47%a
11 (1 mmol)
Scheme 9. Reaction of 2-phenylpyridine (11) with 2a. aGC yield.
at the 20-position of 1 by an arylrhodium(I) intermediate, which is
generated by transmetallation of a Rh(I)X species with 2. The
resulting diaryl(hydrido)rhodium species then undergoes reduc-
tive elimination to give an arylated product 3 and a Rh(I)H species.
In summary, we have demonstrated that the rhodium-catalyzed
direct arylation reactions of phenylazoles and related substrates
including azobenzene and 2-phenylpyridine can be performed by
Table 2
Phenylation of azobenzene (13)a
Rh-cat.
KF
N
N
N
N
Ph–B
+
ClCH2CO2Et
o-xylene
2a or 4a
14a
13
Entry
Ph-B
Rh-cat. (mmol)
Time (h)
Yield of 14a (%)b
1
2
3
NaBPh4 (2a)
[RhCl(cod)]2 (0.005)
[RhCl(cod)]2 (0.005)
Rh(acac)(cod) (0.01)
[Rh(OMe)(cod)]2 (0.005)
[Rh(OMe)(cod)]2 (0.005)
7
4
4
4
4
15
19
20
44
PhB(OH)2 (4a)
PhB(OH)2 (4a)
PhB(OH)2 (4a)
PhB(OH)2 (4a)
4
5c
50 (44)
a
Reaction conditions: 13 (0.25 mmol), 2a or 4a (1 mmol), KF (1 mmol), ClCH2CO2Et (1 mmol) in o-xylene (5 mL) at 140 °C under N2.
GC yield based on the amount of 13 used. Value in parentheses indicates isolated yield.
KF (2 mmol) was used.
b
c

S. Miyamura et al. / Journal of Organometallic Chemistry 693 (2008) 2438–2442
2441
3.2.3. 2-(40-Fluorobiphenyl-2-yl)-1-methylimidazole (3c)
Oil, 1H NMR (400 MHz, CDCl3): d 2.89 (s, 3H), 6.73 (d, J = 1.5 Hz,
1H), 6.94–6.99 (m, 2H), 7.10–7.15 (m, 3H), 7.42–7.48 (m, 2H),
7.51–7.55 (m, 1H), 7.58–7.60 (m, 1H); 13C NMR (100 MHz, CDCl3):
d 32.8, 115.3 (d, J = 21.4 Hz) 120.5, 127.6, 128.5, 129.5, 129.5,
129.7, 130.2 (d, J = 7.7 Hz), 131.9, 136.5 (d, J = 3.8 Hz), 140.6,
147.5, 162.1 (d, J = 247.2 Hz); HRMS (CI) m/z ((M+H)+) Calc. for
[Rh(OMe)(cod)]2 (0.005 mmol)
KF (2 mmol)
N
N
N
N
+
ArB(OH)2
Ar
Ar
ClCH2CO2Et (1 mmol)
o-xylene, 140 oC, 4 h
4b, c
(1 mmol)
13 (0.25 mmol)
14b, c
C16H14FN2: 253.1141. Found: 253.1144.
4
Product, Yield (%)a
3.2.4. 2-(Biphenyl-2-yl)-1-methylbenzimidazole (6)
4b: Ar = 4-CH3C6H4
4c: Ar = 4-ClC6H4
14b: Ar = 4-CH3C6H4, 40 (39)
14c: Ar = 4-ClC6H4, 27 (22)
M.p. 137–138 °C; 1H NMR (400 MHz, CDCl3): d 2.99 (m, 3H),
7.13–7.31 (m, 8H), 7.48–7.53 (m, 1H), 7.56–7.64 (m, 2H), 7.73–
7.75 (m, 1H), 7.83–7.85 (m, 1H); d 13C NMR (100 MHz, CDCl3): d
30.2 109.4, 119.8, 122.1, 122.4, 127.3, 127.6, 128.5, 128.6, 129.0,
129.8, 130.3, 132.1, 135.5, 140.2, 141.6, 143.1, 153.9; HRMS (CI)
m/z ((M+H)+) Calc. for C20H17N2: 285.1392. Found: 285.1385.
a GC yield. Value in parenthese indicates isolated yield.
Scheme 10. Reaction of 13 with arylboronic acids 2.
using arylboron reagents. In these reactions, ClCH2CO2Et acts as an
effective acceptor of the eliminated hydrogen, and KF also pro-
motes the coupling in a number of cases.
3.2.5. 1-(2,6-Diphenylphenyl)pyrazole (8)
M.p. 169–170 °C; 1H NMR (400 MHz, CDCl3): d 6.05 (dd, J = 1.8,
2.4 Hz, 1H), 7.07 (dd, J = 2.4, 0.5 Hz, 1H), 7.11–7.13 (m, 4H), 7.22–
7.25 (m, 6H), 7.37 (dd, J = 1.8, 0.5, 1H), 4.49–7.51 (m, 2H), 7.55-
7.59 (m, 1H); 13C NMR (100 MHz, CDCl3): d 106.0, 127.2, 128.0,
128.2, 129.0, 130.1, 132.4, 136.5, 138.7, 139.3, 140.4; HRMS (CI)
m/z ((M+H)+) Calc. for C21H17N2: 297.1392. Found: 297.1400.
3. Experimental
3.1. General
Reactions were carried out in a 20 mL two-necked flask under
N2. [Rh(OMe)(cod)]2 was prepared according to the published
method [24]. 1H and 13C NMR spectra were recorded at 400 MHz
and 100 MHz, respectively, for CDCl3 solutions. GC analysis was
carried out using a silicon OV-17 column (i.d. 2.6 mm ꢀ 1.5 m) or
a CBP-1 capillary column (i.d. 0.25 mm ꢀ 25 m). GC–MS analysis
was carried out using a CBP-1 capillary column (i.d. 0.25 mm ꢀ
25 m). Phenylimidazoles 1 and 5 were prepared according to the
published method [25]. Other reagents were commercially
available.
3.2.6. 2-(2,6-Diphenylphenyl)-2-oxazoline (10)
M.p. 134–135 °C (lit. [20] m.p. 140.6–141.2); 1H NMR (400 MHz,
CDCl3): d 3.58 (t, J = 9.5 Hz, 2H), 3.89 (t, J = 9.5 Hz, 2H), 7.3 (m,
13H); 13C NMR (100 MHz, CDCl3): d 54.8, 67.3, 127.3, 128.0 (over-
lapped), 128.6, 128.8, 129.6, 140.8, 142.3, 164.3; HRMS (CI) m/z
((M+H)+) Calc. for C21H18NO: 300.1388. Found: 300.1393.
3.3. Reaction of 2-phenylpyridine (11) with sodium tetraphenylborate
(2a) (Scheme 9)
The following experimental procedures may be regarded as typ-
ical in methodology and scale.
A mixture of 11 (1 mmol, 155 mg), 2a (0.5 mmol, 171 mg),
[RhCl(cod)]2
(0.005 mmol,
2.5 mg),
P(biphenyl-2-yl)(But)2
(0.02 mmol, 6.0 mg), ClCH2CO2Et (1 mmol, 122 mg), and dibenzyl
(ca. 50 mg) as an internal standard was stirred in o-xylene (5 mL)
at 140 °C under N2 for 6 h. After cooling, the reaction mixture
was extracted with Et2O and dried over sodium sulfate. Product
12 (40 mg, 35%) was isolated by column chromatography on silica
gel using hexane–ethyl acetate (98:2) as eluent.
3.2. Reaction of 1-methyl-2-phenylimidazole (1) with sodium
tetraphenylborate (2a) (Entry 6 in Table 1)
In a flask was placed KF (1 mmol, 58 mg), which was then dried
at 150 °C in vacuo for 1 h. Then, 1 (0.25 mmol, 40 mg), 2a (1 mmol,
342 mg), [RhCl(cod)]2 (0.005 mmol, 2.5 mg), ClCH2CO2Et (1 mmol,
122 mg), dibenzyl (ca. 50 mg) as an internal standard, and o-xylene
(5 mL) were added and the resulting mixture was stirred at 120 °C
under N2 for 6 h. After cooling, the reaction mixture was extracted
with Et2O and dried over sodium sulfate. Product 3a (54 mg, 92%)
was isolated by thin-layer chromatography on silica gel using hex-
ane–ethyl acetate–NEt3 (55:30:15) as eluent.
3.3.1. 2-(Bipheny-2-yl)pyridine (12)
M.p. 84–85 °C (lit. [26] m.p. 86.5–87.5); 1H NMR (400 MHz,
CDCl3): d 6.88 (dt, J = 7.7, 1.1 Hz, 1H), 7.09 (ddd, J = 7.7, 4.8,
1.1 Hz, 1H), 7.13–7.18 (m, 2H), 7.21–7.25 (m, 3H), 7.37 (td,
J = 7.7, 1.8 Hz, 1H), 7.42–7.48 (m, 3H), 7.68–7.72 (m, 1H), 8.63
(ddd, J = 4.8, 1.8, 1.1, 1H); 13C NMR (100 MHz, CDCl3): d 121.3,
125.4, 126.7, 127.6, 128.0, 128.5, 129.6, 129.7, 130.4, 135.2,
139.5, 140.6, 141.3, 149.4, 159.2; MS (EI) m/z 231 (M+).
3.2.1. 2-(Biphenyl-2-yl)-1-methylimidazole (3a)
Oil: 1H NMR (400 MHz, CDCl3): d 2.84 (s, 3H), 6.70 (d, J = 1.1 Hz,
1H), 7.11 (d, J = 1.1 Hz, 1H), 7.15–7.18 (m, 2H), 7.24-7.30 (m, 3H),
7.42–7.62 (m, 4H); 13C NMR (100 MHz, CDCl3): d 32.8, 120.5,
127.0, 127.5, 128.3, 128.4, 128.6, 129.5, 129.6, 129.6, 131.9,
140.6, 141.6, 147.7; HRMS (CI) m/z ((M+H)+) Calc. for C16H15N2:
235.1235. Found: 235.1241.
3.4. Reaction of azobenzene (13) with phenylboronic acid (4a) (Entry
5 in Table 2)
In a flask was placed KF (2 mmol, 116 mg), which was then
dried at 150 °C in vacuo for 1 h. Then, 13 (0.25 mmol, 46 mg), 4a
(1 mmol, 122 mg), [Rh(OMe)(cod)]2 (0.005 mmol, 2.4 mg),
ClCH2CO2Et (1 mmol, 122 mg), dibenzyl (ca. 50 mg) as an internal
standard, and o-xylene (5 mL) were added and the resulting mix-
ture was stirred at 140 °C under N2 for 4 h. After cooling, the reac-
tion mixture was extracted with Et2O and dried over sodium
sulfate. Product 14a (37 mg, 44%) was isolated by thin-layer chro-
matography on silica gel using hexane–ethyl acetate–NEt3
(94.5:5:0.5) as eluent.
3.2.2. 2-(40-Methylbiphenyl-2-yl)-1-methylimidazole (3b)
Oil, 1H NMR (400 MHz, CDCl3): d 2.32 (s, 3H), 2.85 (s, 3H), 6.71
(d, J = 1.1 Hz, 1H), 7.03-7.09 (m, 4H) 7.11 (d, J = 1.1 Hz, 1H), 7.39–
7.60 (m, 4H); 13C NMR (100 MHz, CDCl3): d 21.0, 32.8, 120.4,
127.2, 128.4, 128.5, 129.1, 129.4, 129.5, 129.6, 131.8, 136.8,
137.7, 141.6, 147.9; HRMS (CI) m/z ((M+H)+) Calc. for C17H17N2:
249.1392. Found: 249.1394.

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[10] R. Giri, N. Maugel, J.-J. Li, D.-H. Wang, S.P. Breazzano, L.B. Saunders, J.-Q. Yu, J.
Am. Chem. Soc. 129 (2007) 3510.
[11] Z. Shi, B. Li, X. Wan, J. Cheng, Z. Fang, B. Cao, C. Qin, Y. Wang, Angew. Chem., Int.
Ed. 46 (2007) 5554.
[12] S.-D. Yang, C.-L. Sun, Z. Fang, B.-J. Li, Y.-Z. Li, Z.-J. Shi, Angew. Chem., Int. Ed. 47
(2008) 1473.
[13] T. Vogler, A. Studer, Org. Lett. 10 (2008) 129.
[14] As an example of direct arylation with arylstannanes, see S. Oi, S. Fukita, Y.
Inoue, Chem. Commun. (1998) 2439.
Oil; 1H NMR (400 MHz, CDCl3): d 7.23–7.36 (m, 15H), 7.47–7.48
(m, 3H); 13C NMR (100 MHz, CDCl3): d 122.2, 126.6, 127.8, 127.9,
128.8, 130.3, 130.4, 130.8, 134.9, 139.5, 150.6, 152.5; HRMS (EI)
m/z (M+) Calc. for C24H18N2: 334.1470. Found: 334.1472.
3.4.2. 2,6-Bis(4-methylphenyl)azobenzene (14b)
M.p. 108–109 °C, 1H NMR (400 MHz, CDCl3): d 2.33 (s, 6H),
7.09–7.17 (m, 8H), 7.32-7.37 (m, 5H), 7.4 (m, 3H); 13C NMR
(100 MHz, CDCl3): d 21.1, 122.3, 127.8, 128.5, 128.8, 130.2, 130.2,
130.7, 134.6, 136.2, 136.5, 150.8, 152.6; HRMS (EI) m/z (M+) Calc.
for C26H22N2: 362.1783. Found: 362.1779.
[15] K. Ueura, T. Satoh, M. Miura, Org. Lett. 7 (2005) 2229.
[16] See also for the monoarylation of nitriles K. Ueura, S. Miyamura, T. Satoh, M.
Miura, J. Organomet. Chem. 691 (2006) 2821.
[17] K. Fugami, S. Hagiwara, H. Oda, M. Kosugi, Synlett (1998) 477.
[18] X. Du, M. Suguro, K. Hirabayashi, A. Mori, T. Nishikata, N. Hagiwara, K. Kawata,
T. Okeda, H.F. Wang, K. Fugami, M. Kosugi, Org. Lett. 3 (2001) 3313.
[19] S. Miyamura, H. Tsurugi, T. Satoh, M. Miura, unpublished results.
[20] S. Oi, E. Aizawa, Y. Ogino, Y. Inoue, J. Org. Chem. 70 (2005) 3113.
[21] O. Daugulis, V.G. Zaitsev, D. Shabashov, Q.-N. Pham, A. Lazareva, Synlett (2006)
3382.
3.4.3. 2,6-Bis(4-chlorophenyl)azobenzene (14c)
M.p. 111–112 °C; 1H NMR (400 MHz, CDCl3): d 7.18–7.49 (m,
16H); 13C NMR (100 MHz, CDCl3): d 122.3, 128.0, 128.1, 129.0,
130.6, 131.3, 131.5, 132.8, 133.9, 137.9, 150.3, 152.3; HRMS (EI)
m/z (M+) Calc. for C24H16Cl2N2: 402.0691. Found: 402.0674.
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