Glucopyranoside-substituted imidazolium-based chiral ionic liquids for Pd-catalyzed homo-coupling of arylboronic acids in water

Article abstract of DOI:10.1080/07328303.2020.1788573

Chiral ionic liquids (CILs) are widely used solvents and materials with prominent properties. Carbohydrate-derived imidazolium-based CILs represent a distinctive type of CILs possessing multiple chiral centers from natural chiral pool. Herein, a series of glucopyranoside-substituted imidazolium-based CILs (Glu-imi-CILs) were synthesized and evaluated as ligands for Pd-catalyzed homo-coupling reactions of arylboronic acids in water. The glucopyranoside substituent was instrumental for improving the catalytic activity of the resulting catalysts. Moreover, a Glu-imi-CIL with a free hydroxyl group for additional coordination was found to be the most efficient ligand. A series of symmetric biaryl compounds (13 examples) were synthesized from arylboronic acids by this method in high isolated yields (85?99percent).

Full text of DOI:10.1080/07328303.2020.1788573

Journal of Carbohydrate Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/lcar20
Glucopyranoside-substituted imidazolium-based
chiral ionic liquids for Pd-catalyzed homo-coupling
of arylboronic acids in water
Zhonggao Zhou , Jing Li , Yue Wu , Yangyang Yuan , Lingfang Kong , Jun Xue &
Zhiqiang Huang
To cite this article: Zhonggao Zhou , Jing Li , Yue Wu , Yangyang Yuan , Lingfang Kong , Jun Xue
&
Zhiqiang Huang (2020): Glucopyranoside-substituted imidazolium-based chiral ionic liquids for
Pd-catalyzed homo-coupling of arylboronic acids in water, Journal of Carbohydrate Chemistry, DOI:
0.1080/07328303.2020.1788573
1
To link to this article: https://doi.org/10.1080/07328303.2020.1788573
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JOURNAL OF CARBOHYDRATE CHEMISTRY
https://doi.org/10.1080/07328303.2020.1788573
Glucopyranoside-substituted imidazolium-based chiral
ionic liquids for Pd-catalyzed homo-coupling of
arylboronic acids in water
a,b
a
a,b
a,b
a,b
Zhonggao Zhou , Jing Li , Yue Wu , Yangyang Yuan , Lingfang Kong
,
a,b
c
Jun Xue , and Zhiqiang Huang
a
College of Chemistry and Chemical Engineering, Gannan Normal University, Jiangxi, People’s
b
Republic of China; Key Laboratory of Jiangxi University for Functional Materials Chemistry,
Ganzhou, People’s Republic of China; School of Resource and Environment Engineering, Jiangxi
University of Science and Technology, Ganzhou, People’s Republic China
c
ABSTRACT
ARTICLE HISTORY
Chiral ionic liquids (CILs) are widely used solvents and materi-
als with prominent properties. Carbohydrate-derived imidazo-
lium-based CILs represent a distinctive type of CILs possessing
multiple chiral centers from natural chiral pool. Herein, a
series of glucopyranoside-substituted imidazolium-based CILs
Received 21 March 2020
Accepted 24 June 2020
KEYWORDS
Carbohydrate; imidazolium-
based ionic liquid;
palladium catalysts;
arylboronic acid; homo-
coupling; green chemistry
(
Glu-imi-CILs) were synthesized and evaluated as ligands for
Pd-catalyzed homo-coupling reactions of arylboronic acids in
water. The glucopyranoside substituent was instrumental for
improving the catalytic activity of the resulting catalysts.
Moreover, a Glu-imi-CIL with a free hydroxyl group for add-
itional coordination was found to be the most efficient ligand.
A series of symmetric biaryl compounds (13 examples) were
synthesized from arylboronic acids by this method in high iso-
lated yields (85ꢀ99%).
Introduction
Ionic liquids (ILs) are outstanding materials. Research about room tem-
perature ILs is booming in the fields of extraction, catalysis, analytics, elec-
[1–7]
trochemistry, fuel production, energy storage, biotechnology, etc.
Although the synthesis of chiral ILs (CILs) is costly and difficult, in light of
their excellent physical and chemical properties and wide range of applica-
tions, including in chiral drug synthesis, asymmetric organic synthesis,
racemic mixture resolution, stationary phases in chiral chromatography and
chiral shifting reagents in nuclear magnetic resonance (NMR) spectroscopy,
[8–10]
recently many CILs have been synthesized and explored.
On the other
hand, carbohydrate is ubiquitous in nature and is biocompatible and of low
CONTACT Zhonggao Zhou
zhgzhou@foxmail.com
College of Chemistry and Chemical Engineering,
Gannan Normal University, Jiangxi, People’s Republic of China.
Supplemental data for this article can be accessed here.
ß 2020 Taylor & Francis Group, LLC

2
Z. ZHOU ET AL.
[
11–16]
cost.
As a result, studies dealing with carbohydrate-derived CILs and
[
17–24]
their metal complexes have been reported.
Carbon–carbon bond construction is one of the most essential subjects
of catalytic synthesis and lies at the center of organic chemistry.
[
25]
Over
the past several decades, transition metal-catalyzed coupling have
changed the way that organic compounds are constructed through the
evolution of different kinds of carbon–carbon bond-forming cross-cou-
pling reactions. The importance and economic significance of such reac-
[
26–28]
tions have been recognized by the 2010 Nobel Prize in Chemistry.
Biaryl fragments are the core building blocks of many functional mole-
cules, and a series of elegant methodologies for the construction of biaryl
[29–31]
compounds have been investigated and established.
Among the strat-
egies for Caryl–Caryl bond formation, the most widely used one is transition
metal-catalyzed cross-coupling reaction, while homo-coupling of aryl com-
pounds provides a simple and efficient way to symmetrical biaryl or polyar-
[32]
omatic compounds.
Recently, the catalytic activity of carbohydrate-derived imidazolium-based
[
33–39]
CILs or N-heterocyclic carbenes and their metal complexes,
including
[35]
[36]
[40]
Ir,
Ru,
and Pd complexs,
have been reported. To the best of our
knowledge, the catalytic activity of carbohydrate-derived imidazolium-based
CILs in Pd-catalyzed homo-coupling have not been investigated extensively.
On the other hand, most Pd-catalyzed C–C bond-forming cross-coupling
reactions demand extra efforts to dissolve catalysts and reaction substrates
and enhance catalytic activity in water, including the application of biphasic
[
41–43]
water/organic solvent system.
To expand the application of carbohydrate-derived imidazolium-based
CILs, we turn our attention to systematically study Pd-catalyzed C–C
bond-forming cross-coupling reactions using more environmental friendly
[
44–46]
systems.
In the present work, we report the synthesis of six glucopyr-
1
anoside-substituted imidazolium-based CILs (Glu-imi-CILs). The H and
C NMR signals of these Glu-imi-CILs were fully assigned with 2 D NMR.
13
The activities of these Glu-imi-CIL-based Pd-catalysts were evaluated in
Pd-catalyzed homo-coupling of arylboronic acids in water.
Results and discussion
Glu-imi-CILs 1a–f having imidazole linked to the same derivative of
tetra-O-acetyl glucopyranoside glucoside and various other substituents,
respectively, were readily synthesized in 90–97% isolated yields. From the
structural features of Glu-imi-CILs 1a–f (Fig. 1), it is clear that the main
difference among these Glu-imi-CILs is the alkyl or aryl substituent
attached to the imidazole ring. Glu-imi-CILs 1a–f were fully characterized

JOURNAL OF CARBOHYDRATE CHEMISTRY
3
Figure 1. Synthesis of Glu-imi-CILs 1a–f.
1
13
with 1D H, C, DEPT135, DEPT90, and 2D COSY, HSQC, HMBC NMR
1
13
spectra (see Supporting Information). The H and C signals for Glu-imi-
1
13
CILs 1a–f were unambiguously and completely assigned (their H and
C
chemical shifts are listed in Tables S1–S3). These NMR data combined with
elemental analysis and high-resolution mass spectrometry verified the com-
[23,39]
position and structure of Glu-imi-CILs 1a–f.
We found that Glu-imi-CILs 1a–f were easily soluble in water due to the
formation of imidazolinium salts. Based on this property, we investigated
their activity as ligands to generate Pd-catalysts for promoting homo-cou-
pling of arylboronic acids in aqueous solutions. In order to optimize the
reaction conditions, 4-methylphenylboronic acid was selected as a model
substrate to explore the reaction in water, and the results are listed in
Table 1.
Glu-imi-CILs 1a–f (2.0 mol%) and PdCl (1.0 mol%) were combined and
2
0
directly used as the catalysts. The reactions gave 48–78% yields of the 4,4 -
dimethylbiphenyl product (Table 1, entries 1–6). However, as a compari-
son, when PdCl /Imi-IL 1g (1-butyl-3-methylimidazolium bromide) was
2
utilized as the catalyst, the reaction yield was decreased to 26% (Table 1,
entry 7). PdCl /Glu-imi-CILs 1d gave the best result and thus was recog-
2
nized as the best catalyst ligand (Table 1, entry 4). To our delight, when
NaClO and p-TsCl were used as additives, the reaction yields were
improved significantly to 99% and 88%, respectively (Table 1, entries 10
[32]
and 12). The results are similar to previous reports in the literature.
When a common phase transfer catalyst Bu NBr was added, the yield was
4
decreased to 50% (Table 1, entry 13), but the role of Bu NBr was not clear.
4
In view of the water solubilities of Glu-imi-CILs, they may act as phase
transfer catalyst and consequently enhanced the solubility of 4-methylphe-
nylboronic acid. In contrast, only 15% yield of the product was obtained

4
Z. ZHOU ET AL.
Table 1. Pd-catalyzed homo-coupling of 4-methylphenylboronic acid in the presence of Glu-
a
imi-CILs 1a–f and Imi-IL 1g .
[
Pd]
Me
Me
Me
B(OH)
2
Ligand
°
H O, 90 C
2
b
Entry
Catalyst (mol%)
Ligand (mol%)
Additive
Time (h)
Yield (%)
48
1
2
3
4
5
6
7
8
9
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
1% PdCl
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2% 1a
2% 1b
2% 1c
2% 1d
2% 1e
2% 1fd
2% 1g
2% 1d
2% 1d
2% 1d
2% 1d
2% 1d
2% 1d
2% 1d
–
K
K
K
K
K
K
K
2
2
2
2
2
2
2
CO
3
CO
3
CO
3
CO
3
CO
3
CO
3
CO
3
12
12
12
12
12
12
12
12
12
3
12
12
12
12
3
3
3
3
1
3
3
1
3
50
66
78
75
70
26
82
80
99
58
88
50
15
10
trace
98
97
98
95
96
93
99
c
KOH
NaOH
NaClO
NaOAc
p-TsCl
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
a
Bu NBr
4
–
c
NaClO
–
c
–
c
2% 1d
1% 1d
1% 1d
1% 1d
1% 1d
0.6% 1d
0.6% 1d
0.2% 1d
NaClO
NaClO
NaClO
NaClO
NaClO
NaClO
NaClO
NaClO
c
0.5% PdCl
0.5% Pd (dba)
0.5% Pd(COD)Cl
0.5% Pd(CF COO)
2
c
2
3
c
2
c
3
2
c
0.3% Pd
0.3% Pd
0.1% Pd
2
(dba)
2
(dba)
2
(dba)
3
3
3
c
c
3
85
ꢁ
Reaction conditions: 4-methylphenylboronic acid (1.0 mmol), additive (1.0 mmol), H O (3.0 mL), 90 C in oil bath.
2
b
Isolated yields after column chromatography.
Reactions at room temperature.
Ligand 1g was 1-butyl-3-methylimidazolium bromide.
c
d
without any additive (Table 1, entry 14). In the absence of Glu-imi-CILs,
there were only trace amounts of product formed either in the presence or
absence of additives (Table 1, entries 15 and 16), demonstrating that Glu-
imi-CILs were necessary for this reaction probably through ionization of
[
47]
ILs in water and showing weak basicity.
After the reaction temperature
was reduced to room temperature, no significant change in the yield was
observed (Table 1, entry 17). By decreasing the loading of PdCl /Glu-imi-
2
CIL 1d to 0.5 mol% Pd, no significant change in yield was observed either
(
97%, Table 1, entry 18).
We also examined different palladium salts, including Pd (dba) ,
2
3
Pd(COD)Cl , and Pd(CF COO) , for the homo-coupling reaction (Table 1,
2
3
2
Entries 19–21). Among the palladium salts studied, the commonly used
Pd (dba) salt was found to be the most efficient and the yield reached
2
3
9
4
8% in just 1 h of reaction time (Table 1, entry 21). Overall, the yield of
0
,4 -dimethylbiphenyl using Pd (dba) as the catalyst was higher than that
2
3
of PdCl , Pd(COD)Cl , and Pd(CF COO) . Therefore, Pd (dba) was
2
2
3
2
2
3

JOURNAL OF CARBOHYDRATE CHEMISTRY
5
chosen as the palladium catalyst used in the next reaction (Table 1, entries
2
2–24). Further decrease in the loading of catalyst to 0.1 ꢂ 0.3 mol% had a
negative effect on the yields (Table 1, entries 23 and 24), but through
extending the reaction time to 3 h, the yield was improved to 99% (Table 1,
entry 23). Therefore, the best reaction conditions for homo-coupling of
arylboronic acids were using Pd (dba) /Glu-imi-CIL 1d (0.3/0.6 mol%) as
2
3
the catalyst in water at room temperature for 12 h in the presence of
NaClO (100 mol%).
The above results promoted us to further investigate the scope and limi-
tations of the Pd (dba) /Glu-imi-CIL 1d system to catalyze arylboronic acid
2
3
homo-coupling. Thus, a range of arylboronic acids with both electron-with-
drawing and electron-donating substituents were investigated. To our
delight, various substituted arylboronic acids afforded the corresponding
products in very good to excellent isolated yields (85–99%, Fig. 2). In gen-
eral, substrates with electron-donating substituents, such as Me-, MeO-, F-,
and Cl-, afforded the corresponding biaryl products in higher yields than
those with electron-withdrawing substituents, such as NO -, CN-, and
2
CF -. Among all substrates studied, 4-methoxyphenylboronic acid gave
3
0
4
,4 -dimethoxybiphenyl 3g in the highest yield (99%), whereas 3-(trifluoro-
0
0
methyl)benzeneboronic acid afforded 2,2 -bis(trifluoromethyl)-1,1 -biphenyl
l in the lowest yield (86%). In addition, the reactions of heteroarylboronic
3
acids, such as 3-pypridylboronic and 2-thienylboronic acids, also afforded
the corresponding products in very good yields (85–90%).
The above results revealed that these water-soluble Glu-imi-CILs 1 were
important in generating and stabilizing the palladium-based catalytic spe-
cies during the reactions. Glu-imi-CIL 1d possessing a free OH group in
addition to the imidazolinium-based N-heterocyclic carbene showed better
catalytic activity as compared to the remaining Glu-imi-CILs 1a–c, 1e, and
Imi-ILs 1g, which may be due to the weak coordination ability of the free
[
48–50]
OH group.
Conclusion
In summary, we have developed an efficient and green method for the
synthesis of symmetrical biphenyl compounds via Pd (dba) /Glu-imi-CIL
2
3
catalyzed homo-coupling of arylboronic acids. The ancillary ligand
Glu-imi-CIL 1d with a free OH group was found to be the most efficient
ligand and the reaction was most productive in the presence of a catalytic
amount of NaClO. A series of symmetric biaryl compounds (13 examples)
were synthesized in high isolated yields (85ꢀ99%) by this new method
under environmentally friendly conditions. These new CIL ligands will be
explored for catalytic chiral reactions in the future.

6
Z. ZHOU ET AL.
Figure 2. Pd (dba) /Glu-imi-CIL 1d catalyzed homo-coupling reactions of arylboronic acids.
2
3
Reagents and conditions: arylboronic acid 2 (1.0 mmol), Pd (dba) /Glu-imi-CIL 1d (0.03/
2
3
0
.06 mmol), NaClO (1.0 mmol), H O (3.0 mL), rt, 3 h. Isolated yields are given.
2
Experimental section
Typical procedure for the synthesis of Glu-imi-CILs 1a–f
Glu-imi-CILs 1a–f was synthesized according to a previously reported
[
23,39]
method.
The solution of a specific N-substituted imidazole (1.1 mmol)
and 2-bromoethyl glucoside (1.0 mmol) in 10.0 mL of CH CN was refluxed
3
for 24 h. The resulting Glu-imi-CILs were purification by column chroma-
tography (dichloromethane/methanol, 20:1).
1
-(2-b-D-Glucopyranosyloxyethyl)-3-methyl-imidazolium bromide (1a)
1
Viscous liquid, 97%. H NMR (400 MHz, CDCl ): 1.78 (s), 1.80 (s), 1.81
3
(
(
s), 1.87 (s), 3.15 (s), 3.67 (m), 3.85 (s), 4.46 (m), 3.89 (m), 3.96 (m), 4.05
m), 4.41 (m), 4.46 (m), 4.52 (d, J ¼ 8.0 Hz), 4.71 (d, J ¼ 8.0 Hz), 4.82 (t,

JOURNAL OF CARBOHYDRATE CHEMISTRY
7
1
3
J ¼ 10.0 Hz), 4.99 (t, J ¼ 8.0 Hz), 7.39 (s), 7.43 (s), 9.27 (s); C NMR
(
100 MHz, CDCl ): d 19.9, 20.0, 20.2, 20.3, 36.1, 49.2, 53.2, 61.1, 67.3, 67.6,
3
7
1
0.6, 67.6, 70.6, 71.2, 71.8, 99.7, 122.6, 122.8, 136.6, 168.9, 169.2, 169.4,
70.2; Elemental analysis calcd (%) for C H BrN O : C, 44.70; H, 5.44;
2
0
29
2 10
found C, 44.72, H, 5.43. HR-MS (ESI, positive mode): m/z (%): 457.1844
þ
(
100) [M–Br] .
1
-(2-b-D-Glucopyranosyloxyethyl)-3-butyl-imidazolium bromide (1b)
1
Viscous liquid, 93%. H NMR (400 MHz, CDCl ): 1.34 (t, J ¼ 8.0 Hz), 1.741
3
(
(
m), 2.25 (m), 2.31 (s), 2.34 (s), 2.35 (s), 2.40 (s), 4.27 (m), 4.37 (m), 4.51
m), 4.62 (m), 4.84 (s), 5.12 (d, J ¼ 8.0 Hz), 5.21 (t, J ¼ 8.0 Hz), 5.33 (t,
1
3
J ¼ 9.6 Hz), 5.59 (t, J ¼ 9.6 Hz), 7.97 (s), 8.02 (s), 9.35 (s); C NMR
(
100 MHz, CDCl ): d 11.7, 18.2, 18.5, 18.6, 18.8, 30.8, 48.5, 60.6, 66.2, 67.3,
3
70.2, 70.6, 71.5, 99.1, 121.2, 122.0, 135.4, 168.9, 168.9, 169.2, 169.9;
Elemental analysis calcd (%) for C H BrN O : C, 47.68; H, 6.09; found
2
3
35
2 10
C, 47.69, H, 6.07. HR-MS (ESI, positive mode): m/z (%): 499.2316
þ
(
100) [M–Br] .
1
-(2-b-D-Glucopyranosyloxyethyl)-3-isopropyl-imidazolium bromide (1c)
1
Viscous liquid, 92%. H NMR (400 MHz, CDCl ): 1.59 (d, J ¼ 8.0 Hz), 1.95
3
(
s), 1.97 (s), 1.98 (s), 2.04 (s), 3.78 (m), 4.07 (m), 4.11 (d, J ¼ 2.0 Hz), 4.20
d, J ¼ 6.0 Hz), 4.23 (d, J ¼ 8.0 Hz), 4.62 (d, J ¼ 8.0 Hz), 4.67 (m), 4.73 (m),
(
4
(
.90 (dd, J ¼ 9.6 Hz, J ¼ 8.0 Hz), 4.99 (t, J ¼ 9.6 Hz), 5.16 (t, J ¼ 9.6 Hz), 7.33
13
s), 7.55 (s), 9.99 (s); C NMR (100 MHz, CDCl ): d 20.3, 20.4, 20.67, 20.7;
3
2
1
2.9, 49.8, 53.2, 61.6, 67.9, 68.1, 71.1, 71.8, 72.2, 100.4, 118.9, 123.7, 135.8,
69.4, 169.6, 169.8, 170.5; Elemental analysis calcd (%) for C H BrN O :
2
2
33
2 10
C, 46.73; H, 5.88; found C, 46.75, H, 5.86. HR-MS (ESI, positive mode): m/
þ
z (%): 485.21576 (100) [M–Br] .
1
-(2-b-D-Glucopyranosyloxyethyl)-3-(2-(2,4-dichlorophenyl)-2-hydroxyethyl)-
imidazolium bromide (1d)
1
White solid, 90%. H NMR (400 MHz, CDCl ): 1.74 (s), 1.76 (s), 1.79 (s),
3
1
.82 (s), 3.62 (m), 3.83 (m), 3.96 (m), 4.12 (m), 4.35 (t, J ¼ 10.8 Hz), 4.48
(
7
t, J ¼ 6.4 Hz), 4.69 (d, J ¼ 16.0 Hz), 4.81 (m), 5.13 (d, J ¼ 8.0 Hz), 5.16 (m),
1
3
.05 (m), 7.11 (m), 7.26 (m), 7.35 (d, J ¼ 8.4 Hz), 9.00 (q, J ¼ 8.0 Hz);
C
NMR (100 MHz, CDCl ): d 19.8, 19.9, 20.1, 20.2, 49.2, 53.2, 54.0, 61.0, 66.9,
3
6
1
7.1, 67.2, 67.3, 67.5, 70.4, 71.1, 71.6, 99.5, 99.7, 121.9, 122.0, 122.3, 127.0,
28.4, 131.2, 133.6, 135.2, 135.3, 136.3, 168.8, 169.1, 169.3, 170.0; Elemental
analysis calcd (%) for C H BrCl N O : C, 45.52; H, 4.67; found C, 45.53,
2
7
33
2 2 11
þ
H, 4.66. HR-MS (ESI, positive mode): m/z (%):631.14603 (100) [M–Br] .

8
Z. ZHOU ET AL.
1
-(2-b-D-Glucopyranosyloxyethyl)-3-(2,6-dimethylphenyl)-imidazolium
bromide (1e)
1
White solid, 91%. H NMR (400 MHz, CDCl ): 2.23 (s), 2.24 (s), 2.26 (s),
3
2
.27 (s), 2.37 (s), 2.39 (s), 4.13 (m), 4.46 (m), 4.51 (m), 4.61 (m), 5.02 (d,
J ¼ 8.0 Hz), 5.16 (dd, J ¼ 9.6 Hz, J ¼ 8.0 Hz), 5.26 (t, J ¼ 9.6 Hz), 5.28 (m),
.46 (t, J ¼ 9.6 Hz), 7.47 (m), 7.47 (m), 7.48 (s), 7.62 (m), 8.39 (t,
5
1
3
J ¼ 4.0 Hz), 10.02 (s); C NMR (100 MHz, CDCl ): d 17.6, 22.4, 22.5, 22.6,
3
2
1
2.8, 50.4, 61.6, 68.1, 68.5, 71.2, 71.9, 72.4, 100.8, 122.3, 124.7, 129.1, 129.1,
31.2, 133.2, 134.6, 138.1, 169.5, 169.6, 169.8, 170.5; Elemental analysis
calcd (%) for C H BrN O : C, 51.68; H, 5.62; found C, 51.69, H, 5.58.
2
7
35
2 10
þ
HR-MS (ESI, positive mode): m/z (%):631.1463 (100) [M–Br] .
1
-(2-b-D-Glucopyranosyloxyethyl)-3-(4-ethyl benzoaty)-imidazolium
bromide (1f)
1
White solid, 92%. H NMR (400 MHz, CDCl ): 1.27 (t, J ¼ 8.0 Hz), 1.85 (s),
3
1
.86 (s), 1.88 (s), 1.91 (s), 3.74 (m), 4.01 (m), 4.12 (m), 4.26 (m), 4.52 (d,
J ¼ 8.0 Hz), 4.73 (s), 4.81 (t, J ¼ 8.0 Hz), 4.90 (t, J ¼ 8.0 Hz), 5.10 (t,
J ¼ 12.0 Hz), 7.82 (d, J ¼ 8.0 Hz), 7.86 (s), 7.92 (s), 8.10 (d, J ¼ 8.0 Hz),
1
3
1
5
1
0.15 (s); C NMR (100 MHz, CDCl ): d 13.8, 20.1, 20.2, 20.3, 20.5, 22.3,
3
0.0, 61.3, 67.2, 67.7, 70.8, 71.5, 71.9, 100.0, 120.0, 121.4, 124.5, 131.4,
31.6, 135.5, 137.2, 164.5, 169.1, 169.5, 169.6, 170.3, 173.1; Elemental ana-
lysis calcd (%) for C H BrN O : C, 50.08; H, 5.25; found C, 50.09, H,
2
8
35
2 12
þ
5
.23. HR-MS (ESI, positive mode): m/z (%):591.2003 (100) [M–Br] .
Typical procedure for arylboronic acid homo-coupling
Arylboronic acid (1.0 mmol), Pd (dba) (0.03 mmol), Glu-imi-CILs 1
2
3
(
0.06 mmol), and an additive (1.0 mmol) were added to a round-bottomed
flask containing 3.0 mL of deionized water. The mixture was stirred for the
temperature and time specified in Table 1. The mixture was monitored
with TLC (n-hexane/EtOAc, 30:1–20:1). When the reaction was complete,
the product was separated by dilution with ether and water, and the
organic phase was dried over MgSO , filtered and then concentrated under
4
reduced pressure. The symmetrical biphenyl product was purified by col-
umn chromatography (n-hexane/EtOAc, 40:1–10:1).
Funding
This work was financially supported by the National Natural Science Foundation of China
[No. 21562002], the Funding Project for Academic and Technical Leaders of Jiangxi
Province [No. 20172BCB22021], Jiangxi Provincial Department of Education [GJJ170834],

JOURNAL OF CARBOHYDRATE CHEMISTRY
9
and Undergraduate Training Program for Innovation and Entrepreneurship
No. CX190009].
[
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