Suzuki cross-coupling of aryl halides with phenylboronic acid catalysed by an amidoxime fibres-nickel(0) complex

Article abstract of DOI:10.3184/174751913X13726940260318

Amidoxime fibres-nickel(0) complexes [Ni(0)-AOFs] were synthesised by combining a Ni2+-solution with amidoxime fibres and reduced by NaH ₂PO₂. The Ni(0)-AOFs are inexpensive phosphine-free recyclable heterogeneous catalysts for the Suzuki coupling reaction of aryl halides with phenylboronic acid to provide the corresponding biphenyls in high yields. The heterogeneous catalyst can be readily recovered by simple filtration and reused several times without significant loss of activity.

Full text of DOI:10.3184/174751913X13726940260318

JOURNAL OF CHEMICAL RESEARCH 2013
RESEARCH PAPER 451
AUGUST, 451–454
Suzuki cross-coupling of aryl halides with phenylboronic acid catalysed
by an amidoxime fibres-nickel(0) complex
Zhi-Chuan Wu, Ye-Neng Lu, Yi-Ming Ren, Zhi-Ming Chen and Ting-Xian Tao*
Department of Biochemical Engineering, Anhui Polytechnic University, Wuhu, 241000, P. R. China
Amidoxime fibres–nickel(0) complexes [Ni(0)–AOFs] were synthesised by combining a Ni2+-solution with amidoxime
fibres and reduced by NaH2PO2. The Ni(0)–AOFs are inexpensive phosphine-free recyclable heterogeneous catalysts
for the Suzuki coupling reaction of aryl halides with phenylboronic acid to provide the corresponding biphenyls
in high yields. The heterogeneous catalyst can be readily recovered by simple filtration and reused several times
without significant loss of activity.
Keywords: Ni(0)–AOFs, Suzuki reaction, amidoxime fibres, heterogeneous catalyst
The transition metal-catalysed Suzuki cross-coupling reaction
is an efficient methods for the construction of C–C bonds.1–6
The Suzuki reaction has been widely used in the synthesis
of natural products, pharmaceutical intermediate and useful
materials containing aryl–aryl bonds.7–12 Various efficient Pd
catalyst precursors have been developed that allow aryl iodides,
bromides, triflates and chlorides to be effectively coupled with
aryl boronic acids under mild reaction conditions.13–17 Ni-based
catalysts have also been successfully used for the Suzuki
reaction of aryl chlorides.18–21 Most of the Ni-based catalysts
are homogeneous and always have phosphine ligands.22–24
Although they have a high catalytic activity and selectivity,
homogeneous nickel catalysts are difficult to separate, reuse
and the phosphine ligands are harmful to environment. To
solve this problem, various heterogeneous nickel catalysts
have been developed.25–28 Modified fibres research has become
widespread.29–32 Previously, we have described the Suzuki
reactions of aryl bromides catalysed by an amidoxime
fibre–palladiumII complex.33 The use of amidoxime fibres
(AOFs)–nickel complex in catalysing the Suzuki reactions was
discovered during this experimental study.
We report here an efficient preparation of AOFs–nickel
complexes and their application as heterogeneous catalysts for
the Suzuki cross-coupling reaction under ambient conditions.
Firstly, the Ni(0)–AOFs was characterised. Figure 1 shows
SEM patterns of the AOFs (Fig. 1a), Ni(II)–AOFs (Fig. 1b),
Ni(0)–AOFs before (Fig. 1c), after reaction (Fig. 1d) and after
recycling five times (Fig. 1e). Before the preparation, the
amidoxime fibres and the Ni(II)–AOFs were cylindrical and
the surface was very smooth, showing unique fibrous texture
(Fig. 1a and 1b). The presence of Ni was confirmed by EDS
(Fig. 2a) on the surface of Ni(II)–AOFs. Before the Suzuki
cross-coupling reaction, the Ni(0)–AOFs showed a crude
surface with a lot of irregularly shaped particles. The particle
size was about 300 nm (Fig. 1c), and the presence of Ni was
confirmed by EDS (Fig. 2b) in the surface. Figure 1d shows
the Ni(0)–AOFs after the reaction. The morphology of the Ni
in Ni(0)–AOFs surface had changed after the reaction and the
amount of the highly active granular Ni had reduced. The
unique fibrous texture was clearly displayed in Fig. 1e. Most
of the highly active granular Ni had disappeared after the
recycling. This might be the reason for the low yield in the last
recycling reaction (Table 4, Run 5).
of SEM, it indicated small particle size of Ni(0) and poor
crystallinity.
The Ni(0)–AOFs were then used in the Suzuki cross-
coupling reaction to check their catalytic activity. The coupling
between iodobenzene and phenylboronic acid was chosen
as the model reaction. Initially, a single solvent such as
DMF, EtOH, and H2O was studied. As shown in Table 1, single
solvents gave low yields for the reaction (Table 1, entries 1–3).
However, high yields were obtained (Table 1, entries 4 and 5)
after we adopted an organic/aqueous co-solvent. The value of
the co-solvent may be attributed to the good solubility of the
organic reactants and the inorganic base.
Next, we examined the effects of bases on the Suzuki
reaction in EtOH/H2O. Organic and inorganic bases including
Et3N, NaOH, KOH, NaHCO3, Na2CO3, K3PO4·3H2O and
K2CO3 were investigated (Table 2, entries 2–7). As shown in
Table 2, K2CO3 was the best base for the reaction giving a high
yield. The results showed that the best amount of K2CO3 was
2 equiv. to iodobenzene (Table 2, entry 10). A low yield was
obtained without any base or by using a strong base (Table 2,
entries 1–3). Under the optimised reaction conditions, the
effect of the amount of the Ni(0)–AOFs was examined.
Various amounts of Ni(0)–AOFs were used to catalyse the
coupling between iodobenzene and phenylboronic acid. The
purified yield showed that the best amount of Ni(0)–AOFs was
6 mol% to iodobenzene (Table 2, entry 10). The yield was not
increased when more amount of Ni(0)–AOFs was added.
Finally, the coupling of various aryl iodides and aryl bro-
mides with phenylboronic acid catalysed by AOFs–nickel(0)
complex were investigated (Table 3). All of the aryl iodides
were converted to the corresponding biphenyls in high yields
(Table 3, entries 1–8). However, the yield obtained from
2-iodobenzoic acid was lower than the others possibly be due
to steric effects (Table 3, Entry 6). The yields from the aryl
bromides were slightly lower than the aryl iodides. Neverthe-
less, aryl bromides substituted by electron-withdrawing
substituents in the para-position increased the reactivity and
the corresponding products were obtained in high yields
(Table 3, entries 11–13).
The recycling performance of Ni(0)–AOFs was investigated
in the reaction of iodobenzene and phenylboronic acid. Ni(0)–
AOFs was filtered from the reaction, washed with hot ethanol
and water, and reused in a subsequent reaction. The data listed
in Table 4 show that Ni(0)–AOFs could be reused four times
without significant loss of catalytic activity.
In conclusion, Ni(0)–AOFs are polymer-supported and
inexpensive catalysts, which exhibit good catalytic activity in
promoting the Suzuki reaction of aryl halides with phenylbo-
ronic acid. The reaction has a wide functional group tolerance.
Furthermore, the catalyst can be reused four times without
significant loss of catalytic activity. The results imply that
the Ni–AOFs catalyst may be a potential alternative for the
construction of the aryl–aryl moiety.
Figure 3 shows the XRD patterns of AOFs (Fig. 3a), Ni(0)–
AOFs(Fig. 3b) and Ni(0)–AOFs (Fig. 3c). The XRD results
indicated that the diffraction peaks centered at 18.6° [33]
resulted from AOFs (Fig. 3a and 3b), and there were no char-
acteristic diffraction peaks for Ni. After the reduction reaction,
characteristic diffraction peaks of Ni disappeared at 46.2°
and indicated amorphous structure. Combining with analysis
* Correspondent. E-mail: tingxiantao@yahoo.cn

452 JOURNAL OF CHEMICAL RESEARCH 2013
Fig. 1 SEM patterns of the AOFs (a); Ni(II)–AOFs (b); Ni(0)–AOFs before reaction (c); after reaction (d); after recycling five times (e).
Fig. 2 Energy spectrum diagram of Ni(II)–AOFs (b) and Ni(0)–AOFs.
A Hitachi S-4800 field-emission scanning electron microscope
equipped with an energy dispersive spectrometer was employed to
examine the morphologies of the samples. The sample fibres were
pressed into disks to examine their phase structures using a Philips
X’ Pert PRO SUPER (XRD) with CuKα radiation in step-scan mode.
The tests were performed with an accelerating voltage of 40 kV and a
current of 50 mA, as well as a scanning step size of 0.02° and a step
time of 0.2 s (the XRD profiles were recorded from 10 to 80°). 1HNMR
spectra were obtained with Bruker ARX-300 spectrometer.
Experimental
The polyacrylonitrile (PAN) fibres were provided by the Jilin Carbon
Co., Ltd. (Jilin, China). Reagents were obtained from commercial
sources and were used without further purification. All products were
known compounds and were identified by comparing their melting
points and 1H NMR with those reported in the literature.
Table 1 The effect of solvents on the Ni(0)–AOFs catalysed
Suzuki reactiona
Entry
Solvents
Yield/%b
1
2
3
C2H5OH
H2O
DMF
/
17
/
4
5
6
7
C2H5OH/H2O (1: 1)
C2H5OH/H2O (2: 1)
DMF/H2O (1: 1)
DMF/H2O (2: 1)
87
98
16
10
a Reaction conditions: iodobenzene (10.0 mmol), phenylboronic
acid (11.0 mmol), Ni(0)–AOFs (6 mol%), K2CO3 (11.0 mmol),
reaction time (4 h), heating reflux, solvent (30 mL).
b Isolated yield.
Fig. 3 XRD patterns of AOFs (a) Ni(II)–AOFs (b), and Ni(0)–
AOFs (c).

JOURNAL OF CHEMICAL RESEARCH 2013 453
Table 2 The effect of various bases on the Ni(0)–AOFs
Table 4 Effect of reusability of catalyst on the Ni(0)–AOFs
catalysed Suzuki reactiona
catalysed Suzuki reactiona
Yield/%b
Run
Yield/%b
Entry Base (base: iodobenzene /mol:mol)
1
2
3
4
5
98
95
90
80
40
1
2
no base (/)
KOH(2:1)
NaOH (2:1)
Et3N (2:3)
/
<1
3
6
4
15
5
NaHCO3 (2:1)
Na2CO3 (1:1)
K3PO4·3H2O (2:3)
K2CO3 (1:2)
K2CO3 (1:1)
K2CO3 (2:1)
K2CO3 (3:1)
95
6
94
a Reaction conditions: iodobenzene (10.0 mmol), phenylboronic
acid (11.0 mmol), Ni(0)–AOFs (6 mol%), K2CO3 (11.0 mmol),
C2H5OH/H2O (V/V = 2) 30 mL, reaction time (4 h), heated under
reflux.
7
78
8
80
9
90
98, 41c, 80d, 98e, 98f
98
10
11
b Isolated yield.
a Reaction conditions: iodobenzene (10.0 mmol), phenylboronic
acid (11.0 mmol), Ni(0)–AOFs (6 mol%), C2H5OH: H2O (V/V = 2)
30 mL, reaction time (4 h), heating reflux
Subsequently, the AOFs (0.4 g) and NiSO4-solution (30 mL, 0.15 mol L−1)
were stirred at 25 °C for 6 h and then filtered. The NiII–AOFs were
washed by distilled water several times and reduced with NaH2PO2
(50 mL, 0.2 mol L−1), Finally the grey fibres [Ni(0)–AOFs] were dried
at room temperature in air (Scheme 1).
b Isolated yield.
c Ni(0)–AOFs: 3 mol%. d Ni(0)–AOFs: 4.5 mol%. e Ni(0)–AOFs:
7.5 mol%. f Ni(0)–AOFs: 9 mol%.
The AOFs–nickel(0) complex was dissolved in a nitric acid solution
(50 mL, 50% HNO3). The content of Ni(0)–AOFs surface was obtained
by using a titration analysis method to measure the concentration of
Ni2+-solution. It was 7.5 mmol g−1.
Table 3 Effect of substituent groups on the Ni(0)–AOFs
catalysed Suzuki reactiona
Coupling reactions
A solution of phenylboronic acid (11 mmol), aryl iodide (10 mmol)
and K2CO3 (20 mmol) in EtOH (30 mL, EtOH: H2O = 2: 1) was treated
with Ni(0)–AOFs (6 mol%) at room temperature. After the mixture
was stirred and refluxed for 4 h, the catalyst was separated by filtra-
tion, washed with hot ethanol and distilled water, and dried at room
temperature, and reused in a next cycle. The filtrate was cooled,
and products were precipitated as white scaly crystals. The the solid
product was filtered, dried, and recrystallised from EtOH–H2O to
afford the pure product.
Entry
R
X
Time/h Products Yield/%b
1
2
H
I
I
4
4
4
4
4
4
4
4
8
8
8
8
8
8
8
2a
2b
2c
2d
2e
2f
2g
2h
2a
2c
2i
98
95
90
87
92
75
89
96
91
54
92
94
90
48
28
4-H3CO
4-CH3
3
I
1
Biphenyl (2a): White solid, m.p. 70–71 °C (lit.33 70–71 °C), H
4
4-H2N
I
NMR (300 MHz, CDCl3): δ 7.32 (t, J = 7.5 Hz, 2H), 7.42(t, J = 7.5 Hz,
4H), 7.58 (d, J = 6.9 Hz, 4H).
5
4-O2N
2-COOH
3-COOH
4-COOH
H
I
6
I
4-Methoxybiphenyl (2b): White solid, m.p. 88–90 °C (lit.33 88–
90 °C), 1H NMR (300 MHz, CDCl3): δ 3.82 (s, 3H), 6.96 (d, J = 8.4
Hz, 2H), 7.28−7.31 (m, 1H), 7.40 (t, J = 7.2 Hz, 2H), 7.50−7.55 (m,
4H).
7
I
8
I
9
Br
Br
Br
Br
Br
Br
Br
10
11
12
13
14
15
4-CH3
4-Methylbiphenyl (2c): Colourless solid, m.p. 45–47 °C (lit.33 45–
48 °C), 1HNMR (300 MHz, CDCl3): δ 2.37 (s, 3H), 7.23 (d, J = 7.8 Hz,
2H), 7.27−7.32 (m, 1H), 7.38−7.43 (m, 2H), 7.48 (d, J = 8.1 Hz, 2H),
7.55−7.58 (m, 2H).
4-CH3CO
4-COOH
4-O2N
4-H2N
2h
2e
2d
2j
4-Aminobiphenyl (2d): Brown solid, m.p. 52–54 °C (lit.33 52–
3-CH3O
1
a Reaction conditions: aryl halides (10.0 mmol), phenylboronic
acid (11.0 mmol), Ni(0)–AOFs (6 mol%), C2H5OH:H2O (V/V = 2)
30 mL, reaction time, heated under reflux.
b Isolated yield.
54 °C), H NMR (300 MHz, CDCl3): δ 3.72 (br s, 2H), 6.75 (d, J =
8.4 Hz, 2H), 7.25−7.28 (m, 1H), 7.36−7.43 (m, 4H), 7.53 (d, J =
9.0 Hz, 2H).
4-Nitrobiphenyl (2e): Pale yellow solid, m.p. 114–115 °C (lit.33
114–115 °C), 1H NMR (300 MHz, CDCl3): δ 7.41−7.51 (m, 3H), 7.61
(d, J = 8.4 Hz, 2H), 7.71 (d, J = 9.0 Hz, 2H), 8.26 (d, J = 9.0 Hz,
2H).
Preparation of the catalyst
The PAN fibres (1 g) were immersed in NH2OH aqueous solution
(200 mL, 1 mol L−1) at 65 °C for 1.5 h. The resultant fibres (AOFs)
were filtered off, washed with distilled water several times and dried.33
2-Phenylbenzoic acid (2f): White solid, m.p. 110–113 °C (lit.8
110–113 °C), 1H NMR (300 MHz, CDCl3) 7.96 (d, J = 7.8 Hz, 1H),
7.60–7.55 (m, 1H), 7.46–7.36 (m, 7H).
Scheme 1 Synthesis of Ni(0)–AOFs.

454 JOURNAL OF CHEMICAL RESEARCH 2013
3-Phenylbenzoic acid (2g): White solid, m.p. 164–166 °C (lit.8
164–168 °C), H NMR (300 MHz, DMSO): δ 7.41−7.45 (m, 1H),
8
9
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7.53 (t, J = 7.8 Hz, 6.9 Hz, 2H), 7.63 (t, J = 7.8 Hz, 2H), 7.72 (d,
J = 7.2 Hz, 2H), 7.96 (t, J = 8.7 Hz, 8.1 Hz, 2H), 8.21 (s, 1H).
4-Phenylbenzoic acid (2h): White solid, m.p. 223–225 °C (lit.8
223–226 °C), 1H NMR (300 MHz, DMSO): δ 7.39−7.52 (m, 3H), 7.73
(d, J = 6.9 Hz, 2H), 7.79 (d, J = 8.4 Hz, 2H), 8.03 (d, J = 8.4 Hz,
2H).
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4-Acetylbiphenyl (2i): White solid, m.p. 118–120 °C (lit.33 118–
123 °C), 1H NMR (300 MHz, CDCl3): δ 2.62 (s, 3H), 7.38−7.48 (m,
3H), 7.60−7.68 (m, 4H), 8.02 (d, J = 8.4 Hz, 2H).
3-Methoxybiphenyl (2j): Pale yellow liquid, refractive index:
1.6070–1.6090 (lit.33 refractive index: 1.6070–1.6100), 1H NMR
(300 MHZ, CDCl3) δ 3.89 (s, 3H), 6.93–6.95 (d, J = 7.86, 1H), 7.18–
7.24 (dd, J1 = 10.86, J2 = 7.65, 2H), 7.37–7.40 (d, 2H), 7.45–7.50 (t,
J = 7.15, 2H), 7.62–7.65 (d, J = 7.23, 2H).
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This research was supported by the National Natural Science
Foundation of China (Nos. 21171003, 20771002, 21101002).
Received 28 March 2013; accepted 13 May 2013
Paper 1301863 doi: 10.3184/174751913X13726940260318
Published online: 9 August 2013
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