Cu2O/SiC as efficient catalyst for Ullmann coupling of phenols with aryl halides

Article abstract of DOI:10.1016/S1872-2067(17)62785-2

A Cu₂O/SiC heterogeneous catalyst was prepared via a two-step liquid-phase method using diethylene glycol as both the solvent and the reducing agent. The catalyst was characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and H₂ temperature-programmed reduction. All the results indicate that Cu is present on the SiC support primarily as Cu₂O. The SEM and TEM results show that cubic Cu₂O nanoparticles are uniformly dispersed on the β-SiC surface. The reaction conditions, namely the temperature, reaction time, and amounts of base and catalyst used, for the Ullmann-type C–O cross-coupling reaction were optimized. A model reaction was performed using iodobenzene (14.0 mmol) and phenol (14.0 mmol) with Cu₂O/SiC (5 wt% Cu) as the catalyst, Cs₂CO₃ (1.0 equiv.) as the base, and tetrahydrofuran as the solvent at 150 °C for 3 h; a yield of 97% was obtained and the turnover frequency (TOF) was 1136 h^?1. The Cu₂O/SiC catalyst has a broad substrate scope and can be used in Ullmann-type C–O cross-coupling reactions of aryl halides and phenols bearing a variety of different substituents. The catalyst also showed high activity in the Ullmann-type C–S cross-coupling of thiophenol with iodobenzene and substituted iodobenzenes; a TOF of 1186 h^?1 was achieved. The recyclability of the Cu₂O/SiC catalyst in the O-arylation of phenol with iodobenzene was investigated under the optimum conditions. The yield decreased from 97% to 64% after five cycles. The main reason for the decrease in the catalyst activity is loss of the active component, i.e., Cu₂O.

Full text of DOI:10.1016/S1872-2067(17)62785-2

Chinese Journal of Catalysis 38 (2017) 658–664
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
Cu2O/SiC as efficient catalyst for Ullmann coupling of phenols with
aryl halides
Yibing Wang a,b, Xiaoning Guo a, Manqian Lü c, Zhaoyang Zhai a, Yingyong Wang a,*, Xiangyun Guoa
a State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, Shanxi, China
b University of Chinese Academy of Sciences, Beijing 100049, China
c School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China
A R T I C L E I N F O
A B S T R A C T
Article history:
A Cu2O/SiC heterogeneous catalyst was prepared via a two‐step liquid‐phase method using diethy‐
lene glycol as both the solvent and the reducing agent. The catalyst was characterized using X‐ray
diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy (SEM), transmission
electron microscopy (TEM), and H2 temperature‐programmed reduction. All the results indicate
that Cu is present on the SiC support primarily as Cu2O. The SEM and TEM results show that cubic
Cu2O nanoparticles are uniformly dispersed on the β‐SiC surface. The reaction conditions, namely
the temperature, reaction time, and amounts of base and catalyst used, for the Ullmann‐type C–O
cross‐coupling reaction were optimized. A model reaction was performed using iodobenzene (14.0
mmol) and phenol (14.0 mmol) with Cu2O/SiC (5 wt% Cu) as the catalyst, Cs2CO3 (1.0 equiv.) as the
base, and tetrahydrofuran as the solvent at 150 °C for 3 h; a yield of 97% was obtained and the
turnover frequency (TOF) was 1136 h−1. The Cu2O/SiC catalyst has a broad substrate scope and can
be used in Ullmann‐type C–O cross‐coupling reactions of aryl halides and phenols bearing a variety
of different substituents. The catalyst also showed high activity in the Ullmann‐type C–S
cross‐coupling of thiophenol with iodobenzene and substituted iodobenzenes; a TOF of 1186 h−1
was achieved. The recyclability of the Cu2O/SiC catalyst in the O‐arylation of phenol with iodoben‐
zene was investigated under the optimum conditions. The yield decreased from 97% to 64% after
five cycles. The main reason for the decrease in the catalyst activity is loss of the active component,
i.e., Cu2O.
Received 24 November 2016
Accepted 2 January 2017
Published 5 April 2017
Keywords:
Cuprous oxide
Silica carbide
Ullmann coupling
O‐arylation
Phenols
Aryl halide
© 2017, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
1. Introduction
ethers in the presence of Cu powder [1]. However, this method
requires harsh reaction conditions, such as a large excess of the
The synthesis of diaryl ethers by O‐arylation of phenols with
aryl halides is one of the most significant reactions in modern
organic synthesis because diaryl ethers are important structur‐
al units in many biologically active compounds, industrial pol‐
ymers, and natural products. Initially, the Ullmann C–O cou‐
pling of phenols with aryl halides was used to synthesize diaryl
phenol, long reaction times, high temperatures (>200 °C) and
stoichiometric amounts of Cu, which restricts its applications
[2]. Much research has focused on overcoming these limitations
and good progress has been achieved in this area. The devel‐
opment of Pd(0)‐ and Cu(I)‐based catalytic systems enabled
major breakthroughs in coupling reactions [3–5]. However,
* Corresponding author. Tel/Fax: +86‐351‐4199306; E‐mail: wangyy79@sxicc.ac.cn
This work was supported by the National Natural Science Foundation of China (21203233, 21473232, 21403270) and Youth Innovation Promotion
Association, CAS (2013115).
DOI: 10.1016/S1872‐2067(17)62785‐2| http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 38, No. 4, April 2017

Yibing Wang et al. / Chinese Journal of Catalysis 38 (2017) 658–664
659
Pd‐based approaches suffer from drawbacks such as the high
was 5 wt%.
cost of Pd and the use of expensive ligands, therefore large‐
scale industrial applications of this method are limited [3,5].
Cu‐based catalysts have been receiving increasing attention as
cheap and readily available catalysts for Ullmann‐type C–O
coupling reactions.
2.2. Catalyst characterization
The crystalline phases of the catalyst were identified by
X‐ray diffraction (XRD, Rigaku D‐Max/RB X‐ray diffractometer)
using Cu Kα radiation. The structure and morphology of the
catalyst were examined using field‐emission scanning electron
microscopy (SEM, S‐4800, JEM‐2100F) and transmission elec‐
tron microscopy (TEM, JSM‐7001F). X‐ray photoelectron spec‐
troscopy (XPS) was performed using an ESCALAB 3 MKII de VG
spectrometer with a Mg Kα X‐ray source. H2 tempera‐
ture‐programmed reduction (H2‐TPR) was performed using an
automatic adsorption instrument (TP‐5080, Xianquan, China).
The Cu loadings of the fresh and recycled Cu2O/SiC catalysts
were determined using inductively coupled plasma optical
emission spectrometry (ICP‐OES, Thermo iCAP6300, USA).
In homogeneous reaction systems, Cu(I)‐based catalysts
show high activities and selectivities for O‐arylation in the
presence of an organic ligand, but separation of the products
and reuse of the catalysts are difficult [6,7]. Heterogeneous
Cu‐based catalysts for the C–O coupling reaction have therefore
attracted attention [8]. Cu nanoparticles and supported Cu na‐
noparticles have been used as catalysts for O‐arylation reac‐
tions and showed high catalytic activities [9–11]. Nano‐CuO
and CuO nanoparticles supported on carbon nanotubes modi‐
fied with iron oxide showed to be highly efficient and reusable
catalysts for the C–O cross‐coupling of phenols with aryl hal‐
ides [12,13]. Park et al. [14] reported that Cu2O nanocubes of
size about 45 nm were highly active and recyclable catalyst for
the cross‐coupling of aryl halides and phenols. Cu2O nanoparti‐
cles show high catalytic activity in C–O cross‐coupling reac‐
tions, but they are unstable and easily oxidized in moist air.
Recent results have indicated that graphene could stabilize
Cu2O nanoparticles and protect them from oxidation, and gra‐
phene‐supported Cu2O nanoparticles showed high catalytic
activity in C–O cross‐coupling reactions [15,16].
Cubic SiC has excellent chemical stability, and thermal and
electrical conductivities. It has been used as support in various
catalytic and photocatalytic reactions [17–21]. Li et al. [22]
modified SiC nanoparticles with Cu2O by the reduction of a
Cu(OH)2 precipitate using N2H4·H2O, and the obtained Cu2O/SiC
catalyst was used to photocatalytically reduce CO2 to CH3OH
under visible‐light irradiation. In this work, we used SiC as a
support to stabilize Cu2O nanoparticles because a p–n junction
can be formed between Cu2O and SiC. The Cu2O/SiC catalyst
was prepared using a two‐step liquid‐phase method and
showed high activity in the O‐arylation of phenols by aryl hal‐
ides, with high yields and turnover frequencies (TOFs).
2.3. Catalytic reaction
The catalytic O‐arylation reactions were conducted in a
sealed stainless‐steel reactor. A phenol (14 mmol), aryl halide
(14 mmol), Cs2CO3 (14 mmol), tetrahydrofuran (THF, 10 mL),
and the Cu2O/SiC catalyst (10 mg) were placed in the reactor.
The reaction was performed under Ar at 150 °C for 3 h. After
the reaction, the suspension was collected and centrifuged. The
supernatant was analyzed using gas chromatography‐mass
spectrometry (Bruker SCION SQ 456GC‐MS, Germany). The
yields and TOFs were calculated based on the aryl halide using
the following equations:
Yield = Conversion (%)  selectivity (%)
= (1 – na/nb)  ntp/(ntp + nbp)  100%
TOF = Amount of aryl halides (mol)  conversion (%) 
selectivity (%)/(mass of Cu2O/SiC (g)  Cu2O loading (%) 
reaction time (h)/M[Cu2O] (g/mol))
where na is the moles of aryl halide after reaction, nb is the
moles of aryl halide before reaction, ntp is the moles of target
product after reaction, and nbp is the moles of byproduct after
reaction.
2. Experimental
3. Results and discussion
2.1. Catalyst preparation
3.1. Catalyst characterization
The detailed preparation of β‐SiC with a specific surface ar‐
ea of 50 m2/g has been reported elsewhere [23]. A Cu2O/SiC
catalyst with a Cu loading of 5 wt% was prepared via a
two‐step liquid‐phase route. In the first step, SiC (50 mg) and
cupric acetate monohydrate (8.26 mg) were dispersed in ab‐
solute ethanol under sonication. The suspension was placed in
a heated oven at 60 °C to obtain a mixture of SiC and copper
acetate. In the second step, the resulting mixture was dispersed
in diethylene glycol (80 mL) and reduced at 180 °C for 2 h to
obtain the Cu2O/SiC catalyst.
Fig. 1 shows the XRD pattern of the Cu2O/SiC catalyst. The
diffraction peaks at 35.76°, 41.46°, 60.13°, 71.89°, and 75.72°
correspond to β‐SiC [18,23]. The peak at 33.6° arises from
stacking faults in SiC [24]. The diffraction peaks at 29.58°,
36.51°, 42.30°, 61.43°, and 73.57° can be indexed to the (110),
(111), (200), (220), and (311) lattice planes of Cu2O, respec‐
tively [25,26], indicating that Cu is present on the SiC support
primarily as the Cu2O phase.
XPS was used to examine the chemical states and surface
properties of the Cu2O/SiC catalyst. As shown in Fig. 2(a), the
peaks for Cu 2p3/2 and Cu 2p1/2 observed at around 932.5 and
952.4 eV are attributed to Cu+. This is in good agreement with
the reported values for Cu2O [27–29]. This confirms that the
For comparison, Cu2O/Al2O3 and Cu2O/SiO2 were prepared
using the same method as was used for the Cu2O/SiC catalyst.
CuO/SiC was prepared by calcination of Cu2O/SiC in a muffle
furnace at 400 °C for 4 h in air. The Cu loading for each catalyst

660
Yibing Wang et al. / Chinese Journal of Catalysis 38 (2017) 658–664
SiC(111)
(a)
(b)
C
D
SiC(220)
SiC(311)
1 µm
100 nm
Cu2O(200)
SiC(222)
(c)
(d)
10
20
30
40
50
60
70
80
90
2/(  )
Fig. 1. XRD pattern of Cu2O/SiC catalyst.
0.25 nm
1 nm
main species dispersed on the SiC support is Cu2O. Fig. 2(b)
shows a Cu LMM Auger peak at 569 eV, which is assigned to
Cu2O [26]. These results show that Cu2O nanoparticles can be
stabilized by using β‐SiC as the support.
Fig. 3. SEM (a, b) and TEM (c, d) images of Cu2O/SiC catalyst.
SEM and TEM were used to examine the morphology and
crystal structure of the catalyst. Fig. 3(a) and (b) show that the
Cu2O nanoparticles are well dispersed on the β‐SiC surface. Fig.
3(c) clearly shows that the Cu2O nanoparticles are cubic, and
based on statistical analysis, the mean diameter of the Cu2O
nanoparticles is about 61 nm. Fig. 3(d) shows that the Cu2O
nanoparticles have clear lattice fringes, and the interplanar
spacing of the nanoparticles is 0.25 nm, corresponding to the
(111) plane of Cu2O [15], which matches the XRD results well.
These results suggest that the Cu component in the Cu2O/SiC
catalyst is Cu2O.
Fig. 4 shows the H2‐TPR results for Cu2O/SiC and CuO/SiC;
the results for Cu2O/Al2O3 and Cu2O/SiO2 are also showed for
comparison. The CuO/SiC reduction peak appears at around
287 °C, corresponding to the reduction of Cu2+ to Cu0. Only one
Cu2O/SiC reduction peak is observed, at around 302 °C, i.e., at a
higher temperature than for CuO/SiC. Two reduction peaks are
observed for the Cu2O/Al2O3 catalyst because of partial oxida‐
tion of Cu2O. According to a previous study, CuO is more easily
reduced than Cu2O [30]. Therefore, we can conclude that the
reduction peaks for the Cu2O/Al2O3 catalyst at 233 and 287 °C
correspond to the reduction of Cu2+ to Cu0 and of Cu+ to Cu0,
respectively. Similarly, the reduction peaks for Cu2O/SiO2 at
236 and 292 °C are associated with the reduction of Cu2+ to Cu0
and of Cu+ to Cu0, respectively. A comparison of the peaks for
(a)
Cu 2p3/2
Cu 2p1/2
930
940
950
960
970
Binding energy (eV)
(b)
569 eV
CuO/SiC
Cu2O/SiC
Cu2O/Al2O3
Cu2O/SiO2
555 560 565 570 575 580 585
Kinetic energy (eV)
0
100
200
300
400
500
600
Temperature (C)
Fig. 2. Cu 2p XPS spectrum (a) and Cu LMM Auger spectrum (b) of
Fig. 4. H2‐TPR profiles of Cu2O/SiC, CuO/SiC, Cu2O/Al2O3, and Cu2O/SiO2
Cu2O/SiC.
catalysts.

Yibing Wang et al. / Chinese Journal of Catalysis 38 (2017) 658–664
661
CuO/SiC, Cu2O/Al2O3, and Cu2O/SiO2 shows that the reduction
Table 2
peak of Cu2O/SiC at around 302 °C can attributed to the reduc‐
tion of Cu+ to Cu0, suggesting that Cu is primarily dispersed on
SiC as the Cu2O phase.
Ullmann C–O cross‐coupling reactions of aryl halides with phenols
catalyzed by Cu2O/SiC.
3.2. Effects of reaction conditions
En‐
try
Yield* TOF
(%) (h−1)
Phenol
Aryl halide
Product
The effects of the reaction conditions, namely temperature,
reaction time, amount of base, and amount of catalyst, on the
Ullmann‐type C–O cross‐coupling reaction were investigated;
the results are summarized in Table 1. Entries 1–5 show that
the yield of diphenyl ether increased with reaction time. When
the reaction time was increased from 0.5 to 3 h, the diphenyl
ether yield increased from 73% to 97%. However, lengthening
the reaction time to 3.5 h did not further increase the yield. We
therefore chose 3 h as the reaction time.
The reaction temperature is also an important factor in the
Ullmann‐type C–O cross‐coupling reaction. The yield of diphe‐
nyl ether increased from 10% to 97% with increasing reaction
temperature from 80 to 150 °C, therefore, subsequent reactions
were performed at 150 °C (Table 1, entries 6–9). Increasing the
amounts of the base and catalyst also led to the increase in the
diphenyl ether yield. The yield of diphenyl ether reached 97%
when 1.0 equiv. of Cs2CO3 and 10 mg of the Cu2O/SiC catalyst
were used (Table 1, entries 10–16). In conclusion, the optimum
reaction conditions are as follows: iodobenzene 14 mmol, phe‐
nol 14 mmol, Cs2CO3 1.0 equiv., Cu2O/SiC 10 mg, and THF 10
mL, 150 °C, 3 h, and an Ar atmosphere.
OH
I
O
1
2
97 1136
87 1032
O
CH3
CH3
OH
I
CH3
CH3
3
83
985
OH
OH
OH
OH
I
O
O
OCH3
COCH3
NO2
I
OCH3
4
5
6
7
89 1056
98 1163
98 1163
95 1127
O
I
COCH3
NO2
I
O
I
H3C
H3C
O
H3C
H3C
OH
8
90 1068
I
I
O
O
OH
Cl
Cl
OH
OH
OH
9
81
961
H3CO
H3CO
10
89 1056
90 1068
I
O
H3CO
H3CO
11
12
13
O
O
CH3
I
CH3
OH
Br
59
58
700
688
H3CO
H3CO
Br
Br
Cl
O
O
OH
OH
Cl
Cl
14
15
49
2
581
24
3.3. Catalytic performance
OH
O
H3CO
H3CO
Table 2 shows the results for the O‐arylation of substituted
phenols with aryl halides using Cu2O/SiC as the catalyst. The
16
1
12
Cl
Cl
O
O
OH
OH
Cl
Cl
17
4
48
Table 1
Reaction conditions: aryl halides 14 mmol, phenols 14 mmol, 1.0 equiv‐
alent Cs2CO3, Cu2O/SiC 10 mg, THF 10 mL, 150 °C, 3 h, under Ar atomo‐
sphere. * Calculated based on the amount of iodobenzene.
Catalytic performance of Cu2O/SiC in O‐arylation of phenol and iodo‐
benzene under various reaction conditions.
Cu2O/SiC
HO
I
Cs2CO3, THF
Cu2O/SiC catalyst showed high activity in the O‐arylation of
phenol and iodobenzene, with a yield of 97%; the TOF was
1136 h−1, which is much higher than those of most heteroge‐
neous catalysts [13,16] (Table 2, entry 1). The electronic effects
of substituent groups on iodobenzene and phenol on the yield
of the O‐arylation reaction were studied.
For iodobenzenes with electron‐donating substituents such
as methyl and methoxy groups the yields were slightly lower
(Table 2, entries 2–4). In contrast, the yields were slightly in‐
creased by the presence of electron‐withdrawing groups such
as acetyl and nitro groups on iodobenzene (Table 2, entries 5
and 6). However, for substituted phenols, electron‐withdraw‐
ing and electron‐donating groups both decreased the yields,
because of an increase in the number of side reactions, but all
the yields were still higher than 80% (Table 2, entries 7–11).
The effects of different aryl halides on the O‐arylation yield
were also investigated. The yields decreased significantly, in
the order iodobenzene > bromobenzene > chlorobenzene, be‐
O
Time Temperature Amount of base Amount of Yield
Entry
(h)
0.5
1
2
3
3.5
3
3
3
3
3
3
3
3
3
3
3
(oC)
150
150
150
150
150
80
100
120
140
150
150
150
150
150
150
150
(equiv.)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
0.25
0.5
0.75
1.0
1.0
catalyst (mg) (%)
1
2
3
4
5
6
7
8
10
10
10
10
10
10
10
10
10
10
10
10
0
73
80
90
97
97
10
57
72
82
55
79
89
20
58
82
97
9
10
11
12
13
14
15
16
2
6
12
1.0
1.0
Reaction conditions: aryl halides 14 mmol, phenols 14 mmol, THF 10
mL.

662
Yibing Wang et al. / Chinese Journal of Catalysis 38 (2017) 658–664
Table 3
Table 4
Ullmann C–S cross‐coupling of thiophenol with iodobenzene and sub‐
stituted iodobenzenes catalyzed by Cu2O/SiC.
Recycling of Cu2O/SiC catalyst.
Run
1
2
3
4
5
Yield (%)
97
84
75
67
64
Reaction conditions: iodobenzene 14 mmol, phenol 14 mmol, other
reaction conditions were the same as those in Table 2.
Yield TOF
(%) (h−1)
Entry Thiophenol Aryl halthide
Product
[32], which enhances the O‐arylation activity.
SH
SH
S
I
1
2
95 1127
The recyclability of the Cu2O/SiC catalyst was investigated
by performing the O‐arylation of phenol with iodobenzene un‐
der the optimum conditions. The data in Table 4 show that the
yield in the first run was 97%; it decreased to 84% in the sec‐
ond run and to 64% after five runs. The decrease in the activity
is caused by loss of the active component (Cu2O). ICP‐OES
showed that the Cu content of fresh Cu2O/SiC was 4.81 wt%,
and it decreased to 2.53 wt% after use. Weak interactions be‐
tween Cu2O nanoparticles and SiC may result in the loss of ac‐
tive components. It is therefore necessary to develop methods
for strengthening the forces between Cu2O and SiC to improve
the reusability of the Cu2O/SiC catalyst. This could perhaps be
achieved by adjusting the thermal treatment conditions or
modifying the SiC surface by chemical oxidation with concen‐
trated sulfuric acid or permanganate to increase the number of
surface functional groups on SiC.
I
CH3
CH3
S
CH3
CH3
87 1032
97 1151
SH
3
I
S
SH
SH
SH
I
OCH3
NO2
S
OCH3
COCH3
NO2
4
5
6
100 1186
98 1163
89 1056
I
S
I
COCH3
S
The reaction conditions were the same as those in Table 2.
cause of the low reactivities of bromobenzene and chloroben‐
zene (Table 2, entries 12–17).
We also investigated the C–S cross‐coupling reactions of
thiophenol and iodobenzene and substituted iodobenzenes.
The results are shown in Table 3. The product yields were
slightly higher because the reactivity of thiophenol is higher
than that of phenol in the cross‐coupling reaction.
4. Conclusions
All the above results suggest that Cu2O/SiC is a highly active
heterogeneous catalyst for the O‐arylation of phenol, substi‐
tuted phenols, and thiophenol with iodobenzene or substituted
iodobenzenes, and the TOF values achieved with the Cu2O/SiC
catalyst for these reactions are much higher than those for
most heterogeneous catalysts. The catalyst also shows some
catalytic activity in the O‐arylation of phenol and substituted
phenols with bromobenzene and chlorobenzene.
The high activity of Cu2O/SiC in the Ullmann‐type C–O
cross‐coupling reaction probably originates from the p–n junc‐
tion between SiC and Cu2O. Cu2O is a p‐type semiconductor.
The β‐SiC we used was an n‐type semiconductor, based on the
positive slope in the Mott‐Schottky curve (Fig. 5) [31]. When
Cu2O nanoparticles are dispersed on the β‐SiC surface, the
electrons in SiC diffuse to Cu2O and the holes in Cu2O diffuse to
SiC until they reach a balance. A p–n junction is then formed
We prepared a Cu2O/SiC catalyst via a simple two‐step liq‐
uid‐phase method. The XRD, XPS, SEM, TEM, and H2‐TPR re‐
sults showed that Cu species were dispersed on the SiC primar‐
ily as the Cu2O phase. The effects of the reaction conditions, i.e.,
temperature, reaction time, amount of base used, and amount
of catalyst used, were investigated in the O‐arylation of iodo‐
benzene with phenol. The optimum conditions were iodoben‐
zene (14 mmol), phenol (14 mmol), Cs2CO3 (1 equiv), and THF
(10 mL), catalyzed by Cu2O/SiC (10 mg) at 150 °C for 3 h under
Ar. A high yield of diphenyl ether and a TOF of 1136 h−1 were
achieved under the optimum conditions. The high activity of
the Cu2O/SiC catalyst probably originates from the p–n junction
between SiC and Cu2O. The Cu2O/SiC catalyst was used with
various substrates to obtain a wide range of diaryl ethers. It
also showed high activity in the Ullmann C–S coupling reaction,
suggesting that this catalyst has general applicability to
Ullmann‐type cross‐coupling reactions.
1.0
0.8
0.6
0.4
0.2
0.0
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Yibing Wang et al. / Chinese Journal of Catalysis 38 (2017) 658–664
663
Graphical Abstract
Chin. J. Catal., 2017, 38: 658–664 doi: 10.1016/S1872‐2067(17)62785‐2
Cu2O/SiC as efficient catalyst for Ullmann coupling of phenols
with aryl halides
X = I, Br, Cl
X
R1 = H, CH3, OCH3, COCH3, NO2
R2 = H, Cl, CH3, OCH3
R
1
Yibing Wang, Xiaoning Guo, Manqian Lü, Zhaoyang Zhai,
Yingyong Wang *, Xiangyun Guo
R2
Institute of Coal Chemistry, Chinese Academy of Sciences;
University of Chinese Academy of Sciences;
Dalian University of Technology
R
2
HO
R1
Cu2O
O
Cu2O
Cu2O
A Cu2O/SiC heterogeneous catalyst was highly active in Ullmann‐type
C–O cross‐coupling reactions of aryl halides and phenols, with a
turnover frequency of up to 1136 h−1, and showed general applicabil‐
ity to Ullmann cross‐coupling reactions.
SiC
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