Bis-benzimidazolium-palladium system catalyzed Suzuki-Miyaura coupling reaction of aryl bromides under mild conditions

Article abstract of DOI:10.1002/aoc.3896

Bis-benzimidazolium salts were prepared successfully from commercially available and inexpensive o-phenylenediamine through a series of simple reactions. The bis-NHC-Pd complexes prepared in situ can catalyze Suzuki-Miyaura cross-coupling reaction under very mild conditions in aqueous media with excellent yields. The efficiency of this reaction is demonstrated by its compatibility with a range of functional groups. Di-ortho-substituted biaryls could be accomplished in 89–99% yields. Moreover, the rigorous exclusion of air or moisture is not required in these transformations.

Full text of DOI:10.1002/aoc.3896

Received: 9 January 2017
DOI: 10.1002/aoc.3896
Revised: 16 April 2017
Accepted: 22 April 2017
F U L L PA P E R
Bis‐benzimidazolium‐palladium system catalyzed Suzuki‐Miyaura
coupling reaction of aryl bromides under mild conditions
Yi‐Rang Lin | Chien‐Cheng Chiu | Huai‐Tsu Chiu | Dong‐Sheng Lee
| Ta‐Jung Lu
Department of Chemistry, National Chung‐
Hsing University, Taichung 40227, Taiwan
Bis‐benzimidazolium salts were prepared successfully from commercially available
and inexpensive o‐phenylenediamine through a series of simple reactions. The bis‐
NHC‐Pd complexes prepared in situ can catalyze Suzuki‐Miyaura cross‐coupling
reaction under very mild conditions in aqueous media with excellent yields. The effi-
ciency of this reaction is demonstrated by its compatibility with a range of functional
groups. Di‐ortho‐substituted biaryls could be accomplished in 89–99% yields. More-
over, the rigorous exclusion of air or moisture is not required in these transformations.
Correspondence
Dong‐Sheng Lee, Department of Chemistry,
National Chung‐Hsing University, Taichung,
40227, Taiwan.
Email: dslee@mail.nchu.edu.tw
Funding information
The Ministry of Science & Technology of the
Republic of China, Grant/Award Number:
102WFA0500216
KEYWORDS
benzimidazolium salt, bis‐NHC ligand, carbine, Suzuki‐Miyaura coupling
1 | INTRODUCTION
The bis‐benzimidazolium salts are air‐ and moisture‐stable
both in the solid state and in solution. The Suzuki‐Miyaura
The Suzuki‐Miyaura coupling reaction is one of the most
important tools to construct C–C bond.[1–4] Aryl halides
coupled with arylboronic acids in the presence of Pd
catalyst to afford diversified biaryls which are important
skeletons in pharmaceutical, natural product, advanced
material, and agricultural chemistry.[5–15] In general,
Pd catalyst containing phosphine ligands have been very
successful for Suzuki coupling reaction in the past
decades.[16–23] Unfortunately, many of the phosphine
ligands are not easily available, and they are air‐sensitive
and expensive. The development of Pd catalyst with phos-
phine‐free ligands is of practical interest and thus has
been receiving great attention.[24–42]
N‐Heterocyclic carbenes (NHCs) have become a very
important class of ligands in organometallic chemistry and
catalysis.[43–47] The strong σ‐donating but poor π‐accepting
abilities of these N‐heterocyclic carbenes leads to the forma-
tion of many stable metal‐carbene complexes, which are good
catalysts in numerous organic transformations. A number
of NHC‐palladium complexes, Pd(OAc)2–benzimidazole or
imidazole, in particular, have emerged as effective catalysts
for Suzuki‐Miyaura cross‐coupling and Heck reaction. They
offer distinct advantages as possible alternatives to palla-
dium‐phosphine systems in C–C coupling reactions.[48–63]
cross‐coupling reaction carries out in aqueous media when
bis‐benzimidazolium salt is as a ligand. This feature has both
economical and environmental benefits. In addition, the
NHC metal complexes bearing bidentate bis‐NHC ligands
enhance stability harsher than those for monodentate NHCs
in catalysis.
Recently, Küçükbay and co‐workers[53] have reported
Suzuki coupling reactions using bis‐NHC‐Pd complex
as
a catalyst assisted by microwave irradiation in
very short reaction time. The coupling reaction of 4‐
bromoacetophenone and phenylboronic acid was performed
using microwave heating (145 °C) in the presence of 1 mol%
Pd(OAc)2 and gave the products in 99% yield. However, 82%
yield was given by conventional heating (145 °C). In 2009,
Leadbeater and co‐workers[55] have been prepared a series
of N‐alkylated benzimidazole and further synthesized bis‐
benzimidazolium salts. The bis‐benzimidazolim salts used
as a ligand for Pd‐mediated coupling reaction of 4‐
bromoanisole and phenylboronic acid under microwave irra-
diation. The low yield (39%) of the corresponding product
was obtained. In addition, sterically hindered di‐ortho‐biaryl
compounds remain a grand challenge in cross‐coupling
reaction catalyzed by bis‐NHC‐Pd system. Herein, we report
the efficient process for Pd‐catalyzed Suzuki‐Miyaura
Appl Organometal Chem. 2017;e3896.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.3896

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LIN ET AL.
coupling reaction of sterically hindered aryl bromides
with aryl boronic acids under mild reaction condition in the
presence of bis‐benzimidazolium salts.
2, K3PO4.H2O (3.0 equiv) as base, t‐BuOH as solvent at
30 °C or 60 °C for 24 h, respectively (Table 1, entries 1
and 2). High conversion rate (100%) and yield (95%) of
the coupling reaction were accomplished at 60 °C, but
modrate conversion (83%) and yield (78%) were obtained
at 30 °C. That means the complex of Pd(OAc)2 and bis‐
benzimidazolium salt may not be formed in situ completely
at low temperature (30 °C), because when the reaction tem-
perature markedly exceeded 60 °C, the coupling reaction
furnished high conversion and yield. This hypothesis
is further supported by a two stage temperature study,
in which Pd(OAc)2 and bis‐benzimidazolium salt 2 were
initially mixed at a higher temperature to accelerate the
formation of the complex; 3a and 4a are then added at a
lower temperature (entry 3). Our results show an excellent
converion (100%) and yield (95%) of coupling reaction
was achieved under these mild conditions. In addition,
various bis‐benzimidazolium salts (2Eta–2Etc) were com-
pared as ligands under the same reaction conditions (entries
3–5). Bis‐NHC 2Eta was the best choice as a ligand. Bis‐
benzimidazolium salts, containing various substituents on
benzimidazole ring, were investigated for the coupling
reaction (entries 3, 6–8). The conversion rate of reaction
decreases as the steric effect of substituents on the benz-
imidazole ring is increased (compare entries 3 and 6). Ele-
vating the first stage temperature, the temperature of
formation of Pd‐NHC complex, ligand 2nPra exhibited
excellent catalytic activity for coupling reaction (compare
entries 6 and 7). The ligand 2iPra was the best choice
under mild reaction conditions (entry 8). Moreover, after
2 | RESULTS AND DISCUSSION
A series of bis‐benzimidazolium salts 2 were prepared
from o‐phenylenediamine as reported in the literature
(Scheme 1).[53,55,64–67] They are air and moisture stable in
solid state.
We started to develop a general protocol for the
coupling of aryl halides with arylboronic acids by using
an unactivated 4‐bromoanisole 3a and phenylboronic acid
4a as the model substrates (Table 1). The test reactions
were performed using 1 mol% Pd(OAc)2, 1 mol% ligand
SCHEME 1 The synthesis of bis‐benzimidazolium salts 2
TABLE 1 Optimization of Suzuki coupling reaction conditions catalyzed by ligands 2a
Temp. 1 (°C)
Time 1 (h)
Temp. 2 (°C)
Time 2 (h)
Ratiob
3a:5aa
Yield
(%)c
Entry
Ligand
2Eta
Complex formation
Suzuki coupling
1
30
30
60
60
60
60
70
70
70
—
—
1
30
60
30
30
30
30
30
30
30
24
24
24
24
24
24
24
24
24
17:83
0:100
0:100
77:23
7:93
78
95
95
20
85
53
90
96
14
2
2Eta
3
2Eta
4
2Etb
2Etc
2nPra
2nPra
2iPra
2iPra
1
5
1
6
1
43:57
8:92
7
1
8
9[d]
1
0:100
79:21
1
aReaction conditions: ArBr (1.0 mmol), PhB(OH)2 (1.5 mmol), Pd(OAc)2 (1.0 mol%), ligand 2 (1.0 mol%), K3PO4.H2O (3.0 mmol) and t‐BuOH (3.0 mL) were used.
bRatio is determined by 400 MHz NMR.
cIsolated yield. [d] 0.1 mol% Pd(OAc)2 was used.

LIN ET AL.
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TABLE 2 Optimization of Suzuki coupling reaction condition catalyzed by the combination of palladium salt and ligand 2iPraa
Temp. (°C)
Suzuki coupling
Time (h)
Ratiob
3a:5aa
Yield
Entry
Solvent
t‐BuOH
(%)c
95
99
85
66
61
28
99
83
99
90
73
99
43
1
30
30
30
30
30
30
40
40
60
60
60
95
95
24
24
24
24
24
24
24
24
24
24
24
24
24
0:100
0:100
13:87
33:67
35:65
70:30
0:100
13:87
0:100
8:92
2
t‐BuOH/H2O (8/2)
t‐BuOH/H2O (6/4)
t‐BuOH/H2O (4/6)
t‐BuOH/H2O (2/8)
H2O
3
4
5
6
7
t‐BuOH/H2O (6/4)
t‐BuOH/H2O (4/6)
t‐BuOH/H2O (4/6)
t‐BuOH/H2O (2/8)
H2O
8
9
10
11
12
13d
24:76
0:100
56:44
H2O
H2O
aReaction conditions: ArBr (1.0 mmol), PhB(OH)2 (1.5 mmol), Pd(OAc)2 (1.0 mol%), ligand (1.0 mol%), K3PO4.H2O (3.0 mmol) and solvent (3.0 mL)
were used.
bDetermined by 400 MHz NMR.
cIsolated yield.
dThe complex recovered from entry 12 was used and 95 °C for 24 h.
TABLE 3 The coupling reaction of aryl bromides and arylboronic acids catalyzed by ligand 2iPra[a]
Entry
3 (R =)
4
Temp. (°C)
Yield (%)b
5aa (99)
5ba (74)
5ba (90)
5ca (97)
5da (98)
5ea (97)
5fa (98)
5ga (70)
5ga (92)
5 ha (97)
5ia (86)
1
4‐OMe (3a)
4‐t‐Bu (3b)
4‐t‐Bu (3b)
4‐CO2Me (3c)
4‐COMe (3d)
4‐COEt (3e)
3‐COEt (3f)
2‐CHO (3 g)
2‐CHO (3 g)
4a
4a
4a
4a
4a
4a
4a
4a
4a
4a
4a
40
40
60
40
40
40
40
40
60
40
40
2
3
4
5
6
7
8
9
10
11
2,4‐diNO2 (3 h)
2‐me (3i)
(Continues)

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LIN ET AL.
TABLE 3 (Continued)
Entry
12
3 (R =)
4
Temp. (°C)
Yield (%)b
5ja (64)
5ja (89)
5 ka (82)
5la (89)
2,6‐diMe (3j)
2,6‐diMe (3j)
4a
4a
4a
4a
4b
40
60
60
60
60
13
14
1‐bromo‐2‐methylnaphthalene (3 k)
1‐bromo‐2‐methoxynaphthalene (3 l)
2‐CHO (3 g)
15
16
5gb (93)
aReaction conditions: ArBr 3 (1.0 mmol), ArB(OH)2 4 (1.5 mmol), Pd(OAc)2 (1.0 mol%), ligand 2iPra (1.0 mol%), K3PO4.H2O (3.0 mmol) and t‐BuOH/H2O (6/4)
(3.0 mL) were used.
bIsolated yield.
the reduction of Pd loading to 0.1 mol%, a poor yield was
obtained at 24 h when Pd‐2iPra catalytic system was
employed (entry 9, 14%).
aryl bromides were able to give the corresponding cou-
pling products with phenylboronic acid in good yield at
60 °C (entries 13–16).
In order to develop more environmentally benign con-
ditions, we chose to examine t‐BuOH/H2O as the solvent
and different t‐BuOH/H2O ratios were studied (Table 2).
We have found that the reactions performed well in t‐
BuOH/H2O (8/2) at 30 °C, in t‐BuOH/H2O (6/4) at
40 °C or t‐BuOH/H2O (4/6) at 60 °C respectively (entries
2, 7 and 9). Gratifyingly, the reaction can go to completion
in pure water at 95 °C (entry 12). Unfortunately, the yield
decreases with recycled catalyst (entry 13). Such decreased
activity could be due to the observation of Pd black in the
first cycle.
A range of aryl bromides were examined in the pres-
ence of 1.0 mol% Pd(OAc)2/2iPra catalyst in t‐BuOH/
H2O (6/4) at 40 °C and the results were summarized in
Table 3. It was immediately clear that the catalytic system
was highly active towards the Suzuki–Miyaura coupling
reaction under mild reaction conditions. Functional groups
on the meta‐ or para‐position of aryl bromides 3 were
tolerated at 40 °C with excellent yields (entries 1–7),
except for product 5ba (entry 2, 74% yield). Because of
the strong bond energy of C–Br bond, the biaryl was
afforded in excellent yield by increasing reaction tempera-
ture (entry 3, 60 °C, 90% yield). Mono‐ortho‐substituted
biaryls were obtained at 40 °C with good‐to‐excellent
yields (entries 8–11). We attempted to apply the highly
active Pd/2iPra system to the Suzuki–Miyaura coupling
3 | CONCLUSION
In conclusion, we have developed a series of efficient bis‐
benzimiadolium salts, which was easy to prepare from
inexpensive and commercially available starting materials.
The catalytic system derived from these ligands and
Pd(OAc)2 in situ at 70 °C provides good results for Suzuki–
Miyaura coupling reaction under mild reaction conditions.
A wide range of aryl bromides bearing common functional
groups such as aldehyde, ketone, ester, and nitro were
compatible to the mild reaction conditions (40 °C). The Pd/
2iPra system is also highly efficient towards Suzuki–Miyaura
coupling reaction for sterically hindered aryl bromides with
arylboronic acid at 60 °C. Considering the simplicity of the
ligand synthesis as well as the easy modification of the ligand
skeleton, we anticipate that further enhancements in reactivity
and versatility of the ligand series will be attainable.
4 | EXPERIMENTAL SECTION
4.1 | Materials and methods
Anhydrous solvent (t‐BuOH) was obtained by distillation
over sodium. Pre‐coated silica gel 60 F‐254, layer thickness
0.2 mm, plates were used for analysis of reactions and
visualized by 0.5% phosphomolybdic acid solution in 95%
EtOH. Merck silica gel 60 (0.040–0.063 μm) was used for
column chromatography. 1H and 13C NMR spectra were
recorded on a Varian Mercury‐400 spectrometer in a solution
reaction
of
sterically
hindered
2‐bromo‐1,3‐
dimethylbenzene. The desired product 5ja could be
obtained in 64% yield at 40 °C (entry 12). However,
the yield could be up to 89% by way of increasing tem-
perature (entrt 13, 60 °C). Various di‐ortho‐substituted

LIN ET AL.
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CDCl3 or DMSO‐d6 with chemical shifts (δ) given in ppm
from internal TMS; J‐values are in Hz. Melting points were
determined with a Thermo 1001D digital melting point
apparatus and were uncorrected. High‐resolution mass
spectra were recorded on a Finnigan/Thermo Quest MAT
95XL mass spectrometer. Benzimidazole was prepared
according to similar literature procedures.[67]
119.5, 109.5, 46.8, 21.6; HRMS‐EI (m/z) [M]+ Calcd for
C10H12N2: 160.1000, found: 160.1004; Anal. Calcd for
C10H12N2: C, 74.97; H, 7.55; N, 17.48, found: C, 74.97; H,
7.55; N, 17.48.
4.3 | General procedures for the Bis‐
benzimidazolium salts
The benzimidazole derivatives (4.00 mmol) in sealed tube
with nitrogen was added with dibromoalkane (2.00 mmol)
and 1,4‐dioxane (5 ml). After stirring for 6 h at room temper-
ature, the resulting solution was heated at 90 °C for 10 h. The
reaction mixture was cooled to room temperature. The bis‐
benzimidazolinum salt precipitate was filtered off and
washed with EtOH.
4.2 | General procedure for the N‐
alkylbenzimidazole 1
To a suspension of benzimidazole (2.36 g, 20.0 mmol) and
KOH (2.24 g, 40.0 mmol) in CH3CN (40 ml) was added alkyl
bromide (40.0 mmol) over a period of 30 min at room
temperature. After stirring at room temperature for 18 h, the
solid was filtered off and the solution was added H2O
(20 ml). The aqueous layer was extracted with EtOAc
(20 ml × 3). The combined organic layers were dried
over MgSO4 and then filtered. The filtrate was concentrated
to afford the crude product which was purified by
chromatography to give N‐alkylbenzimidazole 1.
4.3.1 | 3,3′‐(Propane‐1,3‐diyl)bis(1‐ethyl‐1H‐
benzoimidazol‐3‐ium) bromide (2Eta)
Yield 48% (0.580 g); white solid; Mp 210–208 °C; 1H NMR
(DMSO‐d6, 400 MHz): δ 10.00 (s, 2H), 8.20–8.08 (m, 4H),
7.71 (s, broad, 4H), 4.73 (t, J = 6.8 Hz, 4H), 4.52 (q,
J = 7.2 Hz, 4H), 2.66 (quintet, J = 6.8 Hz, 2H), 1.55 (t,
J = 7.2 Hz, 6H); 13C NMR (DMSO‐d6, 100 MHz): δ
142.1, 131.1, 131.0, 126.5, 113.73, 113.71, 79.2, 43.9,
42.1, 30.7, 28.1, 14.1; HRMS‐ESI (m/z) [M‐H]+ Calcd for
C21H26Br2N4: 492.0524, found: 491.0447; Anal. Calcd for
C21H26Br2N4: C, 51.03; H, 5.30; Br, 32.33; N, 11.34, found:
C, 51.20; H, 5.55; Br, 32.41; N, 10.84.
4.2.1 | 1‐ethyl‐1H‐benzo[d]imidazole (1Et)
Yield = 55% (1.60 g); yellow oil; 1H NMR (CDCl3,
400 MHz): δ 7.92 (s, 1H), 7.82 (d, J = 7.2 Hz, 1H), 7.42
(d, J = 7.2 Hz, 1H), 7.37–7.27 (m, 2H), 4.24 (q,
J = 7.2 Hz, 2H), 1.55 (t, J = 7.2 Hz, 3H); 13C NMR (CDCl3,
100 MHz): δ 143.5, 142.2, 133.3, 122.4, 121.6, 119.75,
109.5, 39.3, 14.8; HRMS‐EI (m/z) [M]+ Calcd for
C9H10N2: 146.0844, found: 146.0843; Anal. Calcd for
C9H10N2: C, 73.95; H, 6.89; N, 19.16, found: C, 73.94; H,
6.89; N, 19.17.
4.3.2 | 3,3′‐(butane‐1,4‐diyl)bis(1‐ethyl‐1H‐
benzoimidazol‐3‐ium) bromide (2Etb)
Yield 71% (0.750 g); white solid; Mp 207–205 °C; 1H NMR
(DMSO‐d6, 400 MHz): δ 10.09 (s, 2H), 8.21–8.00 (m, 4H),
7.69–7.67 (m, 4H), 4.61 (s, broad, 4H), 4.53 (q,
J = 7.2 Hz, 4H), 2.05 (s, broad, 4H), 1.54 (t, J = 7.2 Hz,
6H); 13C NMR (DMSO‐d6, 100 MHz): δ 142.0, 131.09,
130.90, 126.5, 113.77, 113.68, 46.0, 42.1, 25.4, 14.1;
HRMS‐ESI (m/z) [M‐H]+ Calcd for C22H28Br2N4:
506.0681, found: 505.0610; Anal. Calcd for C22H28Br2N4:
C, 52.09; H, 5.36; Br, 31.50; N, 11.04, found: C, 52.05; H,
5.32; Br, 31.54; N, 11.09.
4.2.2 | 1‐n‐propyl‐1H‐benzo[d]imidazole
(1nPr)
Yield = 58% (1.85 g); yellow oil; 1H NMR (CDCl3,
400 MHz): δ 7.89 (d, J = 7.2 Hz, 1H), 7.84 (s, 1H), 7.33–
7.21 (m, 3H), 3.85 (t, J = 7.2 Hz, 2H), 1.67 (sextet,
J = 7.2 Hz, 2H), 0.77 (t, J = 7.2 Hz, 3H); 13C NMR (CDCl3,
100 MHz): δ 142.5, 141.7, 132.4, 121.2, 120.4, 118.6, 108.4,
44.8, 21.5, 9.6; HRMS‐EI (m/z) [M]+ Calcd for C10H12N2:
160.1000, found: 160.0996; Anal. Calcd for C10H12N2: C,
74.97; H, 7.55; N, 17.48, found: C, 74.93; H, 7.57; N, 17.50.
4.3.3 | 3,3′‐(pentane‐1,5‐diyl)bis(1‐ethyl‐1H‐
benzoimidazol‐3‐ium) bromide (2Etc)
4.2.3 | 1‐isopropyl‐1H‐benzimidazole (1iPr)
Yield 72% (0.840 g); white solid; Mp 212–209 °C; 1H NMR
(DMSO‐d6, 400 MHz): δ 10.45 (d, J = 13.6 Hz, 2H), 8.60 (d,
J = 7.2 Hz, 4H), 8.27–8.11 (m, 4H), 5.03 (d, J = 7.2 Hz, 8H),
3.00 (s, 4H), 2.04 (t, J = 7.2 Hz, 6H), 1.93 (s, 2H); 13C NMR
(DMSO‐d6, 100 MHz): δ 141.6, 130.9, 126.3, 113.5, 48.4,
41.9, 27.8, 24.2, 14.0; HRMS‐ESI (m/z) [M‐H]+ Calcd for
Yield = 63% (2.01 g); yellow oil; 1H NMR (CDCl3,
400 MHz): δ 7.95 (s, 1H), 7.85 (d, J = 2.4 Hz, 1H), 7.41–
7.32 (t, J = 3.6 Hz, 1H), 7.26 (d, J = 2.8 Hz, 2H), 4.47 (sep-
tet, J = 6.4 Hz, 1H), 1.47 (d, J = 6.8 Hz, 6H); 13C NMR
(CDCl3, 100 MHz): δ 143.3, 1395, 132.5, 121.8, 121.2,

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LIN ET AL.
C23H30Br2N4: 520.0837, found: 519.0755; Anal. Calcd for
C23H30Br2N4: C, 52.89; H, 5.79; Br, 30.60; N, 10.73, found:
C, 48.43; H, 5.96; Br, 35.44; N, 10.17.
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Yield 66% (0.970 g); white solid; Mp 212–210 °C; 1H NMR
(DMSO‐d6, 400 MHz): δ 9.85 (s, 2H), 7.98 (s, 4H), 7.55 (s,
4H), 4.56 (s, 4H), 4.31 (s, 4H), 2.34 (s, 2H), 1.78 (d,
J = 5.2 Hz, 4H), 0.78 (s, 6H); 13C NMR (DMSO‐d6,
100 MHz): δ 142.3, 131.2, 126.6, 113.8, 48.2, 44.0, 30.7,
28.1, 22.1, 10.8; HRMS‐ESI (m/z) [M‐H]+ Calcd for
C23H30Br2N4: 520.0837, found: 519.0763; Anal. Calcd for
C23H30Br2N4: C, 52.89; H, 5.79; Br, 30.60; N, 10.73, found:
C, 52.46; H, 6.22; Br, 30.20; N, 11.12.
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4.3.5 | 3,3′‐(Propane‐1,3‐diyl)bis(1‐isopropyl‐
1H‐benzoimidazol‐3‐ium) bromide (2iPra)
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Yield 62% (0.880 g); Mp 213–211 °C; 1H NMR (DMSO‐d6,
400 MHz): δ 9.85 (s, 2H), 7.96 (s, 4H), 7.50 (d, J = 4.0 Hz,
4H), 4.85 (t, J = 6.8 Hz, 2H), 4.51 (t, J = 6.8 Hz, 4H), 2.36
(s, 2H), 1.42 (d, J = 6.4 Hz, 12H); 13C NMR (DMSO‐d6,
100 MHz): δ 140.9, 131.3, 130.5, 126.6, 126.5, 114.1,
113.7, 50.6, 44.1, 28.1, 21.5; HRMS‐ESI (m/z) [M‐H]+
Calcd for C23H30Br2N4: 520.0837, found: 519.0763; Anal.
Calcd for C23H30Br2N4: C, 52.89; H, 5.79; Br, 30.60; N,
10.73, found: C, 52.72; H, 6.16; Br, 30.12; N, 10.90.
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How to cite this article: Lin Y‐R, Chiu C‐C, Chiu H‐
T, Lee D‐S, Lu T‐J. Bis‐benzimidazolium‐palladium
system catalyzed Suzuki‐Miyaura coupling reaction of
aryl bromides under mild conditions. Appl
Organometal Chem. 2017;e3896. https://doi.org/
10.1002/aoc.3896
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