Pillar[5]arene-based N-heterocyclic carbene ligand for Pd-catalysed Suzuki reaction

Article abstract of DOI:10.1007/s10847-016-0673-5

A pillar[5]arene-based N-heterocyclic carbene ligand was prepared by reaction of bromoethoxy pillar[5]arene with excess 1-methylimidazole at 130?°C in the absence of solvent and used as a catalyst for the Suzuki coupling reaction. Excellent yields were obtained when the Suzuki reactions were carried out under ambient atmosphere in ethanol, employing 0.2?mol% ligand, 1?mol% PdCl₂(CH₃CN)₂ and 1.5?mmol of K₂CO₃. The novel pillar[5]arene-based imidazolium salt is a promising material for the construction of highly active supramolecular catalytic systems.

Full text of DOI:10.1007/s10847-016-0673-5

J Incl Phenom Macrocycl Chem
DOI 10.1007/s10847-016-0673-5
ORIGINAL ARTICLE
Pillar[5]arene-based N-heterocyclic carbene ligand
for Pd-catalysed Suzuki reaction
1
1
1
1
1
Xue-Dong Xiao
•
Jia-Qi Liu
•
Ya-Li Bai
•
Rui-Hua Wang
•
Jun-Wen Wang
Received: 19 June 2016 / Accepted: 6 October 2016
Ó Springer Science+Business Media Dordrecht 2016
Abstract A pillar[5]arene-based N-heterocyclic carbene
ligand was prepared by reaction of bromoethoxy pil-
lar[5]arene with excess 1-methylimidazole at 130 °C in the
absence of solvent and used as a catalyst for the Suzuki
coupling reaction. Excellent yields were obtained when the
Suzuki reactions were carried out under ambient atmo-
sphere in ethanol, employing 0.2 mol% ligand, 1 mol%
PdCl (CH CN) and 1.5 mmol of K CO . The novel pil-
Since their discovery by Arduengo in 1991 [7, 8], N-
heterocyclic carbenes (NHCs) have demonstrated excel-
lent performance in various catalytic reactions, including
those catalysed by palladium [9–11]. Similarly,
supramolecular N-heterocyclic carbene ligands (such as
crown ethers [12–14], cyclodextrins [15, 16], calixarenes
[17, 18] and porphyrins [19, 20]) play an important role in
catalytic reactions, exhibiting excellent performance. The
Mei-Ming [21] group reported Pd(II)–NHC crown ether
complexes (Fig. 1a) in 2008, used to catalyse Suzuki–
Miyaura reactions of various aryl bromides in water.
These reactions did not require inert gas protection and
exhibited high product yields and turnover numbers
(TONs) of up to 99,000. We prepared a porphyrin-based
NHC ligand (Fig. 1b) and investigated its catalytic
activity in Suzuki coupling in 2009 [22, 23]. The Ulrich
Darbost [24] group reported calix[4]arene-supported N-
heterocyclic carbene palladium complexes (Fig. 1c) in
2014, and fully characterized their performance in
Suzuki–Miyaura reactions with a variety of aryl bromides
and heterocyclic substrates, revealing good catalytic
performance.
2
3
2
2
3
lar[5]arene-based imidazolium salt is a promising material
for the construction of highly active supramolecular cat-
alytic systems.
Keywords Pillar[5]arene Á N-Heterocyclic carbene Á
Supramolecular Á Suzuki Á Cross-coupling
Introduction
The Suzuki–Miyaura [1] reaction belongs to the valuable
class of organic coupling reactions, using palladium(0)
complexes to catalyse the coupling of boranes, boronic
esters, and boronic acids with aryl halides [2–5]. This
reaction has become one of the most important C–C bond
forming methods in the synthesis of natural products,
polymers, liquid crystals and organic materials [6].
Pillar[n]arenes, a new class of macrocyclic hosts, were
first reported by Tomoki Ogoshi [25] and co-workers in
2008. Their structural repeating units are connected by
methylene bridges in the two para-positions, forming a
rigid pillar-like architecture [26]. Due to ease of synthesis
and modification, pillar[n]arenes have attracted a lot of
attention in the field of analytical chemistry. Tomoki
Ogoshi and Yong Yao reported pillar[5]arene-based imi-
dazolium salts in 2012. This kind of pillar[5]arenes were
used in molecular recognition [27] and as a novel stabilizer
to fabricate gold nanoparticles in water [28]. As part of our
current research on supramolecular N-heterocyclic carbe-
nes, we have found that pillar[5]arene-based imidazolium
Electronic supplementary material The online version of this
article (doi:10.1007/s10847-016-0673-5) contains supplementary
material, which is available to authorized users.
&
Jun-Wen Wang
wangjunwen2013@126.com
1
Department of Chemistry, Shanxi Normal University,
Linfen 041004, People’s Republic of China
123

J Incl Phenom Macrocycl Chem
O
O
O
O
Bun
N
O
O
R
N
R
N
Br
N
N
Pd
N
N
O
O
O
N
3
3
Br
porphyrin
N
N
Cl
Pd
Cl
N
N
O
3
N
3
PF -
6
4
N
R
N
R
OPr OPr OPr OPr
R
R
A
B
C
Fig. 1 Structures of the complexes a, b and c
Scheme 1 Synthesis of NHC
ligand 3
H C
3
N
Br
O
Br
N
O
O
H C
3
N
N
(
HCHO)n, BF Et O
H
C
2
H
C
2
3
2
CH Cl
NH PF /CH OH
4 6 3
2
2
O
O
5
O
5
1
0PF -
6
Br
Br
N
N
CH3
1
2
3
salts as N-heterocyclic carbene precursors, exhibit good
base, solvent, temperature, etc. We used the reaction of
bromobenzene with phenylboronic acid as a prototypical
substrate combination to produce the biphenyl coupling
product 5a in presence of ligand 3, with the results sum-
marized in Table 1.
organocatalytic properties.
Results and discussion
Initially, a good yield (99%, entry 10) was obtained
using 1 mol% of ligand 3 and 5 mol% of PdCl (CH CN) .
In this study, we synthesized pillar[5]arene-based imida-
zolium hexafluorophosphate according to previously
reported procedures [27, 28]. The synthesis of NHC ligand
is outlined in Scheme 1. Bromoethoxy pillar[5]arene 2 was
2
3
2
The amount of 3 was subsequently reduced to 0.2 mol%,
still achieving a 99% yield (entry 11). During temperature
screening, we conducted the reaction for 1.5 h at 65 °C,
reaching a yield of 99% undoubtedly (entry 9). When the
temperature was lowered to 50 °C, the yield was still sat-
isfactory (entry 11). Surprisingly, when the reaction was
performed at room temperature for 12 h, the yield reached
90% (entry 8), indicating the novel pillar[5]arene-based
N-heterocyclic carbene ligand 3 exhibits excellent catalytic
properties for the Suzuki cross-coupling reactions.
prepared by stirring
a
mixture of 1,4-bis(2-bro-
moethoxy)benzene 1, BF ÁEt O and paraformaldehyde in
3
2
dry CH Cl for 150 min under N atmosphere. Pil-
2
2
2
lar[5]arene-based N-heterocyclic carbene ligand 3 was
prepared by reacting bromoethoxy pillar[5]arene 2 with
excess 1-methylimidazole at 130 °C in absence of solvent,
-
6
followed by anion exchange with PF [27, 29, 30]. The
1
product was characterized by H NMR, C NMR, IR
13
In order to explore the scope and limitations of ligand 3,
we coupled extensive aryl halide derivatives with phenyl-
boronic acid derivatives under optimized reaction condi-
tions, with the results summarized in Table 2.
1
spectroscopy and elemental analysis. The H NMR reso-
nance of the imidazolium proton of ligand 3 (NCHN) at d
8
.89 supports the formation of the expected carbene
precursor.
In the initial phase of the study, we tried to determine
optimum conditions for the catalytic system, including
Generally, the electronic properties of aryl halides sig-
nificantly influence the outcome of coupling reactions, i.e.
the presence of electron-withdrawing groups is proven
1
23

J Incl Phenom Macrocycl Chem
Table 1 Optimization of reaction conditions
Ligand 3, PdCl (CH CN) , Base
2
3
2
Br +
B(OH)2
Solvent, Temp, Time
5
a
a
Entry
Solvent
Base
T (°C)
T (h)
Yield (%)
1
2
3
4
5
6
7
8
9
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
Ethanol
DMF
KOH
PO
65
50
50
50
50
50
50
25
65
50
50
50
50
50
50
75
5
33
90
85
61
82
45
33
90
99
K
3
4
3
CH
3
t
COONa
3
KO Bu
3
NEt
t
NaO Bu
3
3
3
Na CO
2
3
3
K
K
K
2
CO
2
CO
2
CO
3
3
3
12
1.5
1.5
1.5
3
b
10
11
12
13
14
15
16
99
K
2
CO
3
99
15
27
K
K
K
K
K
2
CO
2
CO
2
CO
2
CO
2
CO
3
THF
3
3
c
2
H O
3
3
3
3
Trace
CH
3
CN
3
40
51
1,4-dioxane
3
Reaction condition: 0.50 mmol of bromobenzene, 0.55 mmol of phenylboronic acid, 1.5 mmol of base, 0.2 mol% ligand 3, 1 mol% PdCl
CH CN) , solvent 1.5 mL
2
(
3
2
Bold values indicate the best reaction condition
a
Isolated yields
b
2 3 2
The amount of ligand 3 is 1 mol%, PdCl (CH CN) is 5 mol%
c
Add TBAI 0.22 mmol
beneficial. In contrast, the presence of electron-donating
groups or neutral groups results in moderate yields. In this
experiment, we found that 4-bromotoluene and 4-bro-
moanisole, having electron-donating groups, are coupled
with phenylboronic acid in yields of 95% or more (Table 2,
entries 5 and 8). When 4-chlorophenylboronic acid was
used as a substrate, the reaction yield was slightly
decreased (Table 2, entry 6 and 9). Additionally, we tried
to couple less reactive chlorobenzene derivatives, but the
yields were relatively low (Table 2, entries 1 and 2).
After the NHC-pillar[5]arene was shown to be an
effective catalyst for the Suzuki–Miyaura cross-coupling of
aryl bromides and phenylboronic acid, the monomer-NHC
ligand 4 lacking the pillar-shaped architecture was also
prepared for comparison (Fig. 2). This new imidazolium
salt was then compared with the NHC–pillar[5]arene 3 in
standard Suzuki–Miyaura cross-coupling forming biaryls
pillar[5]arene core seems to have a large impact on the
coupling. Notably, with 0.2 mol% of NHC–pillar[5]arene 3
used, all of the aryl bromides and phenylboronic acid were
converted to the corresponding biaryls in excellent yields
(entries 1, 3, 5, 7, and 9). Ligand 4 was used in 1 mol%
loading, providing the same number of imidazolium units
as ligand 3. However, the corresponding reaction yields
were significantly reduced (entries 2, 4, 6, 8, and 10).
In order to further demonstrate the importance of
1
supramolecular macrocyclic for this reaction, H NMR
spectroscopy (Fig. 3) was employed to study the inclusion
interaction between ligand 3 and aryl bromide substrates.
As shown in Fig. 3, when ligand 3 was added to bro-
mobenzene solution, the signals of the homologous protons
of the bromobenzene showed different shifts. (Other
spectra in the Supplementary material) These facts suggest
that the higher yields obtained with ligand 3 are
attributable to its structural properties and capacity to
strongly bind aryl bromides in its hydrophobic cavity
(Fig. 4), which enhances the interaction with other reagents
and palladium [31–35].
(
Table 3).
Interestingly, both precursors gave comparable reaction
yields in the simple coupling of aryl bromides and
phenylboronic acid at 50 °C. It is surprising that the
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J Incl Phenom Macrocycl Chem
Table 2 Suzuki–Miyaura cross-coupling of aryl halide with different boronicacids
Ligand 3, PdCl (CH CN) , K CO
R1
X + R2
B(OH)2
2
3
2
2
3
R1
R2
C H OH, 50 , 1.5h
2
5
5
a-o
1
2
a
Entry
R
R
X
Product
Yield (%)
1
2
3
4
5
6
7
8
9
H
H
Cl
Cl
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
5a
5b
5c
5d
5b
5e
5f
40
34
99
99
99
82
97
99
90
90
99
95
91
99
96
92
CH
H
3
H
Cl
H
CH
3
3
3
3
3
CH
CH
CH
CH
CH
2
2
2
2
2
O
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
H
Cl
CH
H
O
O
O
O
5g
5h
5i
Cl
10
11
12
13
14
15
16
CH
H
O
O
O
NO
NO
NO
CN
CN
CN
2
5j
2
2
Cl
5k
5l
CH
H
5m
5n
5o
Cl
CH
Reaction condition: 0.50 mmol of Ar–X, 0.55 mmol phenylboronic acid, 1.5 mmol of K
ethanol 1.5 mL, 50 °C, 1.5 h
2 3 2 3 2
CO , 0.2 mol% ligand 3, 1 mol% PdCl (CH CN) ,
a
Isolated yields after chromatographic purification
Experimental
CH3
N
N
O
All manipulations, reactions were performed under air
atmosphere; solvents were purified using standard meth-
ods. Precursors 1, 2 and 3 were synthesized according to
the previously reported [27, 28]. IR spectra were recorded
PF -
2
6
O
1
13
N
on a Varian 660-IR spectrometer. H NMR and C NMR
spectra were obtained on a Bruker AVANCE III HD
N
H C
3
ligand 4
600 MHz spectrometer in CDCl and d -DMSO with TMS
3 6
as an internal reference. Coupling constants (J-values) are
given in hertz. NMR multiplicities are abbreviated as fol-
lows: s = singlet, d = doublet, t = triplet, m = multiplet
signal.
Fig. 2 Structure of the monomer-NHC ligand 4
Conclusion
In summary, a convenient and efficient Suzuki–Miyaura
cross-coupling for the synthesis of biaryls employing an
NHC ligand was disclosed. The novel NHC-pillar[5]arene
ligand was prepared and demonstrated to exhibit good
catalytic activity in Suzuki–Miyaura cross-coupling of aryl
bromides and phenylboronic acid under mild conditions,
without the protection of an inert gas. The hydrophobic
cavity present in the structure of pillar[5]arenes was found
to play a very important role in this coupling reaction.
Inspired by this, we are now pursuing a search for highly
active supramolecular catalytic systems.
Preparation of the 1,4-bis(2-bromoethoxy)benzene
(1) [27, 28]
A solution of 4-bis(2-hydroxyethoxy) benzene (6.0 g,
0 mmol) and triphenylphosphine (18.9 g, 72.1 mmol) in
3
dry acetonitrile (200 mL) was cooled with an ice bath.
Under vigorous stirring, carbon tetrabromide (24.0 g,
72.4 mmol) was slowly added. The mixture was stirred at
room temperature for 12 h. Then cold water (200 mL) was
added to the reaction mixture to give white precipitation.
1
23

J Incl Phenom Macrocycl Chem
Table 3 Suzuki–miyaura cross-coupling of bromobenzene derivatives with different catalysts
Ligand, PdCl (CH CN) , K CO
2
3
2
2
3
R
X +
B(OH)2
R
C H OH, 50 , 1.5h
2
5
a
Entry
R
Ligand
t (h)
Yield (%)
1
2
3
4
5
6
7
8
9
H
3
4
3
4
3
4
3
4
3
4
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
99
70
99
68
99
66
99
75
99
78
H
CH
CH
CH
CH
3
3
3
3
O
O
NO
NO
CN
CN
2
2
1
0
Reaction condition: 0.50 mmol of Ar–X, 0.55 mmol phenylboronic acid, 1.5 mmol of K
PdCl (CH CN)
, ethanol 1.5 mL, 50 °C
2 3
CO , 0.2 mol% ligand 3, 1 mol% ligand 4, 1 mol%
2
3
2
a
Isolated yields after chromatographic purification
1
Fig. 3 Partial H NMR spectra
(600 MHz) of ligand 3 and
bromobenzene in DMSO
The precipitate was collected, washed with methanol/water
(0.834 g, 27.8 mmol), CH Cl (200 mL) was then charged,
2 2
(
3:2, 3 9 100 mL), recrystallized from methanol, and
and the solution was cooled to 0 °C in an ice bath. Boron
trifluoride etherate (3.0 mL, 23.7 mmol) was added to the
dried under vacuum to afford 1 as white crystals, 82.7%
1
(
14.5 g). H NMR (600 MHz, CDCl ): d = 6.86 (s, 4H),
solution cooling with ice bath under N protection. The
2
3
4
.24 (t, J = 6.3, 4H), 3.61 (t, J = 6.3, 4H) ppm.
mixture was stirred for 2.5 h. The reaction mixture was
filtration. Filtrate washed with 2.5 M NaOH (2 9 30 mL)
and water (1 9 30 mL) and dried with anhydrous MgSO4.
The solvent was evaporated to provide a crude product.
Recrystallized from ethyl acetate, and dried under vacuum
to afford 2 as white or light yellow powder, 40% (1.2 g).
Preparation of the pillar[5]arene (2) [27]
To a 500 mL Schlenk flask with magnetic stir bar was
charged compound 1 (3.0 g 9.2 mmol), Paraformaldehyde
123

J Incl Phenom Macrocycl Chem
7.75 mmol) was added. The reaction mixture was stirred at
room temperature for 30 min. The precipitate was col-
lected by filtration to afford ligand 4 as white powder, 80%
(0.77 g). Elemental Analysis: Calcd for C18H24F12N
4
3
O2P2 C, 34.95; H, 3.88; N, 9.06. Found: C, 35.01; H,
1
.79; N, 9.11. H NMR (600 MHz, d -DMSO): d = 9.16
6
(
s, 2H), 7.79 (s, 2H), 7.71 (s, 2H), 6.90 (s, 4H), 4.55 (t,
1
3
J = 4.8, 4H), 4.27 (t, J = 4.7, 4H), 3.87 (s, 6H) ppm.
C
NMR (150 MHz, d -DMSO): d = 152.7, 137.5, 124.0,
6
123.2, 116.1, 66.7, 49.0, 36.3 ppm.
Catalysis
Fig. 4 The inclusion interaction mechanism for ligand 3 with aryl
bromide substrates
General procedure for the Suzuki coupling reactions
In a typical run, a mixture of aryl bromide (0.50 mmol),
phenylboronic acid (0.55 mmol), K CO (1.5 mmol),
1
H NMR (600 MHz, CDCl ): d = 6.91 (s, 10H), 4.22 (t,
3
2
3
J = 5.6, 20H), 3.84 (s, 10H), 3.63 (t, J = 5.7, 20H) ppm.
1
0
.2 mol% ligand, 1 mol% PdCl (CH CN) in 1.5 mL of
2 3 2
3
C NMR (150 MHz, CDCl ): d = 149.7, 129.1, 116.0,
3
ethanol were stirred at 50 °C for 1.5 h under air. Solvent
ethanol was removed completely under vacuum degree
6
9.0, 30.7, 29.4 ppm.
0.09 MPa at 45 °C to give a crude product. The pure
Preparation of the NHC-pillar[5]arene ligand (3)
27, 28]
product was isolated by column chromatography on silica.
1
Diphenyl (5a) White solid, H NMR (600 MHz,
[
CDCl ): d = 7.58 (d, J = 8.4, 4H), 7.43 (t, J = 7.5, 4H),
7
3
1
.34 (t, J = 7.4, 2H) ppm. C NMR (150 MHz, CDCl3):
3
To solution of 1-methylimidazole (6 mL), compound 2
0.50 g, 0.298 mmol) was added. The mixture was heated
(
d = 141.2, 128.7, 127.2, 127.1 ppm.
1
-Methylbiphenyl (5b) White solid, H NMR (600 MHz,
at 130 °C for 48 h. The resulting solution was poured into
diethyl ether and the precipitate was collected by filtration.
The reprecipitation process was repeated three times to
afford white solid. White solid in methanol (20 mL),
NH PF (0.86 g, 5.28 mmol) was added. The reaction
4
CDCl ): d = 7.51–7.50 (m, 2H), 7.42 (d, J = 8.1, 2H),
3
7
.35 (dd, J = 5.7, 13.2, 2H), 7.25 (t, J = 7.4, 1H),
1
3
.18–7.17 (m, 2H), 2.32 (s, 3H) ppm. C NMR (150 MHz,
7
4
6
CDCl ): d = 140.1, 137.3, 136.0, 128.4, 127.7, 126.0,
3
mixture was stirred at room temperature for 30 min. The
precipitate was collected by filtration to afford ligand 3 as
white powder, 85% (0.71 g). Elemental Analysis: Calcd for
C95H120F60N20O10P10 C, 36.19; H, 3.81; N, 8.89.
2
0.1 ppm.
0
4
-Chloro-1,1 -biphenyl (5c) White solid; 99% yield
1
(95 mg). H NMR (600 MHz, CDCl ): d = 7.48–7.47 (m,
3
2
H), 7.45–7.44 (m, 2H), 7.38–7.37 (m, 2H), 7.34–7.33 (m,
3
H), 7.29 (t, J = 7.4, 1H) ppm. C NMR (150 MHz,
1
1
Found: C, 36.04; H, 3.92; N, 8.93. H NMR (600 MHz, d6-
2
DMSO): d = 8.89 (s, 10H), 7.81 (s, 10H), 7.47 (s, 10H),
CDCl ): d = 127.9, 127.8, 127.3, 126.6, 126.0 ppm.
3
0
6
.70 (s, 10H), 4.62 (s, 20H), 4.29 (s, 20H), 3.74 (s, 30H),
4
-Ethoxy-1,1 -biphenyl (5d) White solid; 99% yield
1
1
.50 (s, 10H) ppm. C NMR (150 MHz, d -DMSO):
3
3
6
(100 mg). H NMR (600 MHz, CDCl ): d = 7.48 (td,
3
d = 149.1, 137.2, 128.4, 124.1, 123.1, 114.6, 66.8, 49.5,
6.2, 29.0 ppm.
J = 1.6, 8.1, 2H), 7.45–7.44 (m, 2H), 7.34 (dd, J = 5.0,
3
1
0.6, 2H), 7.24–7.21 (m, 1H), 6.90–6.89 (m, 2H), 4.01 (q,
1
J = 7.0, 2H), 1.37 (dd, J = 4.5, 9.5, 3H) ppm. C NMR
3
Preparation of the ligand (4)
(
150 MHz, CDCl ): d = 157.5, 139.9, 132.6, 127.7, 127.1,
3
1
25.7, 125.6, 113.7, 62.5, 13.9 ppm.
0
To a 100 mL round flask with magnetic stirbar was
4
-Chloro-4-Methylbiphenyl (5e) White solid; 82% yield
1
charged 1,4-bis(2-bromoethoxy)benzene
1
(0.50 g,
(83 mg). H NMR (600 MHz, CDCl ): d = 7.51–7.50 (m,
3
1
.55 mmol) and 1-methylimidazole (0.51 g, 6.21 mmol) in
2
H), 7.46–7.44 (m, 2H), 7.39–7.38 (m, 2H), 7.25 (d,
1
J = 8.9, 2H), 2.39 (s, 3H) ppm. C NMR (150 MHz,
3
THF (50 mL). This mixture was heated to reflux for 10 h.
The resulting solution was poured into diethyl ether and the
precipitate was collected by filtration. The reprecipitation
process was repeated three times to afford white solid.
CDCl ): d = 139.6, 137.5, 137.1, 133.0, 129.6, 128.9,
3
128.2, 126.8, 21.1 ppm.
0
0
4
-Methyl-4-ethoxy-1,1 -biphenyl (5f) White solid; 97%
1
White solid in methanol (20 mL), NH PF6 (1.26 g,
4
yield (103 mg). H NMR (600 MHz, CDCl ): d = 7.50 (d,
3
1
23

J Incl Phenom Macrocycl Chem
0
J = 8.5, 2H), 7.45 (d, J = 8.0, 2H), 7.22 (d, J = 7.8, 2H),
4 -Ethoxy-4-cyanobiphenyl (5o) White solid; 92% yield
1
6
.95 (d, J = 8.5, 2H), 4.08–4.06 (m, 2H), 2.38 (s, 3H),
(103 mg). H NMR (600 MHz, CDCl ): d = 7.69 (d,
3
1
3
.45–1.43 (m, 3H) ppm. C NMR (150 MHz, CDCl3):
1
J = 8.2, 2H), 7.64 (d, J = 8.3, 2H), 7.53 (d, J = 8.6, 2H),
d = 158.3, 138.0, 136.3, 133.6, 129.4, 127.9, 126.6, 114.7,
3.5, 21.1, 18.4 ppm.
-Methoxybiphenyl (5g) White solid; 99% yield
6.99 (d, J = 8.6, 2H), 4.09 (q, J = 7.0, 2H), 1.45 (t,
1
3
6
J = 7.0, 3H) ppm.
C NMR (150 MHz, CDCl3):
4
d = 159.6, 145.3, 132.6, 131.3, 128.3, 127.1, 119.1, 115.1,
110.1, 63.6, 14.8 ppm.
1
(
90 mg). H NMR (600 MHz, CDCl ): d = 7.49–7.45 (m,
3
4
H), 7.34 (t, J = 7.8, 2H), 7.23–7.22 (m, 1H), 6.92–6.90
1
m, 2H), 3.78 (s, 3H) ppm. C NMR (150 MHz, CDCl3):
3
Acknowledgements We are grateful for the support provided by the
Research Fund for the Shanxi Natural Science Foundation of China
for the Project (No. 2011011006-4).
(
d = 158.1, 139.8, 132.8, 127.7, 127.1, 125.7, 125.6, 113.2,
5
4.3 ppm.
0
4
-Chloro-4-Methoxybiphenyl (5h) White solid; 90%
1
References
yield (98 mg). H NMR (600 MHz, CDCl ): d = 7.50–7.47
3
(
m, 2H), 7.46–7.45 (m, 2H), 7.39–7.37 (m, 2H), 7.25 (d,
1
. Miyaura, N., Suzuki, A.: Palladium-catalysed cross-coupling
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1
J = 8.9, 2H), 2.39 (s, 3H) ppm. C NMR (150 MHz,
3
CDCl ): d = 139.6, 137.5, 137.1, 133.0, 129.6, 128.9,
3
1
28.2, 126.8, 21.1 ppm.
0
2. Andrus, M.B., Song, C.: Palladium–imidazolium carbene catal-
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0
4
-Methoxy-4-ethoxy-1,1 -biphenyl (5i) White solid;
1
6
3% yield (72 mg). H NMR (600 MHz, CDCl ): d = 7.40
3
3
4
5
. Bardin, V.V., Shabalin, A.Y., Adonin, N.Y.: Weakly nucleophilic
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(
t, J = 8.0, 4H), 6.89–6.87 (m, 4H), 4.00 (q, J = 7.0, 2H),
1
.77 (s, 3H), 1.36 (t, J = 7.0, 3H) ppm. C NMR
3
3
(
150 MHz, CDCl ): d = 157.6, 157.0, 132.5, 132.3, 131.2,
3
1
26.7, 113.7, 113.1, 62.5, 54.3, 13.9 ppm.
-Nitrobiphenyl (5j) Yellow solid; 99% yield (100 mg).
H NMR (600 MHz, CDCl ): d = 8.31–8.30 (m, 2H),
4
1
3
(
g3-1-t-Bu-indenyl)Pd(IPr)(Cl). Beilstein J. Org. Chem. 11,
7
.75–7.74 (m, 2H), 7.64–7.62 (m, 2H), 7.52–7.50 (m, 2H),
3
.46–7.44 (m, 1H) ppm. C NMR (150 MHz, CDCl3):
2
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1
7
˙
˙ ¨
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1
24.1 ppm.
0
4
-Chloro-4-Nitrobiphenyl (5k) Yellow solid; 95% yield
1
1
2, 81–88 (2016)
(
(
(
110 mg). H NMR (600 MHz, CDCl ): d = 8.31–8.30
m, 2H), 7.72–7.70 (m, 2H), 7.57–7.55 (m, 2H), 7.48–7.47
3
m, 2H) ppm. C NMR (150 MHz, CDCl ): d = 146.3,
3
6
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1
45.3, 136.2, 134.3, 128.4, 127.6, 126.7, 123.2 ppm.
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. Arduengo, A.J., Harlow, R.L., Kline, M.: A stable crystalline
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-Ethoxy-4-Nitrobiphenyl (5l) Yellow solid; 91% yield
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(
111 mg). H NMR (600 MHz, CDCl ): d = 8.27 (d,
3
J = 8.6, 2H), 7.69 (d, J = 8.7, 2H), 7.57 (d, J = 8.6, 2H),
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7
.01 (d, J = 8.6, 2H), 4.10 (q, J = 7.0, 2H), 1.46 (t,
1
9
3
J = 7.0, 3H) ppm.
C NMR (150 MHz, CDCl3):
d = 159.8, 147.3, 146.5, 130.9, 128.6, 127.0, 124.1, 115.1,
6
3.7, 14.8 ppm.
-Cyanobiphenyl (5m) White solid; 99% yield (90 mg).
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4
1
3
1
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.69 (d, J = 8.3, 2H), 7.59 (d, J = 7.2, 2H), 7.49 (t,
1
J = 7.6, 2H), 7.43 (t, J = 7.3, 1H) ppm. C NMR
3
1
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(
150 MHz, CDCl ): d = 145.7, 139.2, 132.6, 129.1, 128.7,
3
1
27.8, 127.2, 119.0, 110.9 ppm.
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4
-Chloro-4-cyanobiphenyl (5n) White solid; 96% yield
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1
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1
3
7
.47–7.45 (m, 2H) ppm. C NMR (150 MHz, CDCl3):
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