Efficient Ullmann C-X coupling reaction catalyzed by a recoverable functionalized-chitosan supported copper complex

Article abstract of DOI:10.1039/C8NJ02677G

Three different types of functionalized-CS were prepared and anchored with copper salts for use as the catalyst for the Ullmann C-X coupling reaction. The Schiff-basic chitosan supported copper complex (PCCS@CuI) exhibits the highest catalytic activity. The structure of the catalyst was characterized by FTIR spectroscopy, TG, XRD, SEM, EDS and XPS. This catalyst exhibited high applicability for the C-N and C-S coupling reactions, in which good to excellent yields were obtained. Its easy separation, good reusability and stability were notable.

Full text of DOI:10.1039/C8NJ02677G

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DOI: 10.1039/C8NJ02677G
Efficient Ullmann C-X coupling reaction catalyzed by
a recoverable functionalized-chitosan supported
copper complex
Xuemin Liu a, Shuo Chang a, Xinzhi Chen b, Xin Ge a* and Chao Qian b*
a School of Chemical and Material Engineering, Jiangnan University, Wuxi, P.R China
b Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture
Technology, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, P.R
China.
Abstract: The three different types of functionalizedꢀCS were prepared and anchored copper
salts to employed as the catalyst for Ullmann CꢀX coupling reaction. The Schiffꢀbasic chitosan
supported copper complex (PCCS@CuI) has the highest catalytic activity. The structure of the
catalyst was characterized by FTIR, TG, XRD, SEM, EDS and XPS. This catalyst exhibited high
applicability for the CꢀN and CꢀS coupling reactions, in which the good to excellent yields were
obtained. Its easy separation, good reusability and stability were noticeable.
Keywords: Schiffꢀbasic chitosan, copper, Ullmann coupling, supported catalysis
Graphical Abstract
*
Corresponding author. Xin, Ge, Eꢀmail: gexin@jiangnan.edu.cn and Chao Qian, Eꢀmail:
qianchao@zju.edu.cn

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1. Introduction
The copperꢀcatalyzed Ullmann coupling reaction is one of the most important strategies for
the construction of CꢀX bond, which plays a fundamental role in pharmaceutical and agrochemical
industry.1 However, the prototypical Ullmann reaction suffers from some disadvantages, such as
high temperature, excessive usage of copper catalyst, limited substrate scope and moderate yield,
which hinder its wide application.2 Up until 2001, important breakthroughs just started to be
achieved in developing novel efficient catalytic systems by introducing ligands.3 More specifically,
various ligands, e.g. diamines,3ꢀ4 glycol,5 Schiff base,6 amino acids,7 diketones,8 phenanthroline,9
2,2′ꢀbipyridine,10 carbohydrates,11 oxalamic acid12 and diamide,13 have been explored for
efficiently promoting the CꢀX coupling. Although these efficient ligands have made great
achievements in improving Ullmann reaction, the recovery of catalysts remains challenging. The
entrapment and coordination of transition metal complexes in heterogeneous supports, which
could enable the easy separation of the products and reusability of the catalyst, therefore have
gained enormous attention. Up to now, various organic and inorganic materials, e.g., alumina,14
zeolites,15 polymers16 and magnetic materials,17 have been evaluated, whereas their applications
were still limited from its instability in basic conditions, high energyꢀconsuming and
timeꢀdemanding, during the preparation process. Therefore, the exploration of new green,
renewable, environmental friendly and lowꢀcost materials for Ullmann reaction is becoming an
urgent and interesting issue.
Due to its biodegradable, renewable and ecoꢀfriendly characteristics, polysaccharides are
becoming the most popular bioꢀresources in recent years.18 Moreover, they have enormous
potential in variation and optimization for possessing many functional groups on the backbone.19
Among those kinds of polysaccharides, chitosan (CS) has many outstanding properties such as
antibacterial, high “metal affinity” and water solubility. In 2014, Shen et al.20 successfully applied
an unmodified chitosanꢀCu catalyst for Ullmann CꢀS coupling, nevertheless the CS in the form of
powders lack adequate catalytic activity and absorption capacity. Owning to its abundance in
amino groups, amenable for chemical modification,21 various CS derivatives and microspheres
have also been prepared to chelate different metals, e.g. Pd, Cu, Rh and Au, and have been used as
efficient and green catalysts for organic reactions, e.g. Sonogashira crossꢀcoupling,22

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hydroformylation,23 cyclopropanation24 and olefin oxidation25. However, so far as reported, there
were only a few examples using functional chitosan for Ullmann reaction. Importantly, the
functional chitosan anchored metal has been found to be more potential than chitosan metal
complex.26
Thus, following the interests in fineꢀtuning and design of carbohydrate structure,27 we report
a recoverable functionalizedꢀchitosan supported copper complex for Ullmann CꢀX coupling
reaction. To accomplish this, three different types of functionalizedꢀCS by introducing various
functional groups onto its backbone (in Figure 1) were studied and their catalytic activities for
Ullmann reaction were evaluated. The Schiffꢀbasic chitosan supported copper complex was
characterized and the stability of this catalyst was tested.
Figure 1. Preparation of the functionalizedꢀchitosan supported copper complex
2 Experimental Section
2.1 General
Chitosan powder (MW: 10,000ꢀ50,000, deacetylation degree 95%, purchased from Aladdin
reagent (Shanghai) Co., Ltd.) was used without further purification. Pyridineꢀ2ꢀcarboxaldehyde,

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2ꢀhydroxybenzaldehyde and N,N'ꢀcarbonyldiimidazole were purchased from Damasꢀbeta,
2ꢀPyridinecarboxylic acid was purchased from Sinopharm Chemical Reagent Co. Ltd. Aryl
halides, imidazole and sulfinate salts were purchased from Alfa Aesar. Melting points were
determined on an X4ꢀData microscopic melting point apparatus and were uncorrected. Nuclear
magnetic resonance (NMR) spectra were measured at 400 MHz (1H) or at 100 MHz (13C) with
CDCl3 as solvent on a Bruker Avance DRXꢀ400 spectrometer. All reactions were monitored by
analytical thinꢀlayer chromatography (TLC) from Merck with detection by UV. The products were
purified by column chromatography through silica gel (300ꢀ400 mesh). All reagents and solvents
were general reagent grade unless otherwise stated.
2.2 Preparation of Functional Chitosan.
As a linear polysaccharide of Dꢀglucosamine unit, CS possesses a number of amino groups.
In this work, the amino groups in CS were modified by introducing pyridineꢀ2ꢀcarboxaldehyde,
2ꢀhydroxybenzaldehyde and 2ꢀpyridinecarboxylic acid, to synthesize PCCS, HBCS and PACS,
respectively. Based on this design, recyclable functionalizedꢀchitosan supported copper complex
was prepared and used for Ullmann reaction. It was achieved by suspending the
functionalizedꢀchitosan in the solution of copper salts, subsequently was separated by using
centrifuge and dried under vacuum at 50 oC.
The preparation of PCCS. Chitosan (2.0 g, equivalent to 12.4 mmol NH2 group),
pyridineꢀ2ꢀcarboxaldehyde (4.72 mL, 49.6 mmol) and acetic acid (10 mL) were added to methanol
(75 mL). Then the mixture was refluxed for 12 h at 65 oC. After the resultant mixture was cooled
to 0 oC, the solid was separated by filtration, washed with ethanol and then dried under vacuum at
50 oC for 12 h.
The preparation of HBCS. Chitosan (2.0 g, equivalent to 12.4 mmol NH2 group) and
2ꢀhydroxybenzaldehyde (7.58 g, 62.1 mmol) were added to ethanol (100 mL), meanwhile 10 mL
acetic acid was added. The mixture was refluxed for 12 h at 70 oC, then cooled with ice water to 0
oC. The solid was separated by filtration, and finally dried under vacuum at 50 oC for 12 h.
The preparation of PACS. N,N'ꢀCarbonyldiimidazole (3.24 g, 20 mmol) and 2ꢀPyridinecarboxylic
acid (1.85 g, 15 mmol) were heated to 60 °C in THF (100 mL) with stirring. After adding chitosan
(1.61 g, 10 mmol), the mixture was stirred at 60 °C for 12 h. The product was crystallized by
adding ice water and dried under vacuum at 50 oC for 12 h.

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2.3 The preparation of functionalized-chitosan supported copper complex
Three modified chitosan supported copper salt was synthesized according to the following
procedure: the catalyst was prepared by suspending modified chitosan in a solution of copper salt
for 3 h under neutral conditions at 50 °C (For CuI, the solvent was acetonitrile. For CuSO4 and
Cu(OAc)2, water was used as solvent). After adsorption of the copper, the solid was preconditioned
by washing thoroughly to remove any loose Cu compounds and dried under vacuum at 50 °C
overnight to give the catalyst. After complexation with CuI, CuSO4 and Cu(OAc)2, the colors of these
catalyst are as follows: PCCS@CuI is reddish brown, PCCS@ CuSO4 is green, PCCS@Cu(OAc)2 is
green, HBCS@CuI is yellow, HBCS@CuSO4 is yellow, HBCS@Cu(OAc)2 is yellow, PACS@ CuI is
green, PACS@CuSO4 is blue, PACS@Cu(OAc)2 is blue.
2.4 General procedure for Ullmann reaction catalyzed by the PCCS@CuI
To a stirred solution of DMSO (3 mL) were added aryl halide (1.0 mmol), nucleophile (1.2
mmol), PCCS@CuI and Cs2CO3 (2 mmol) at room temperature. Then the reaction mixture was
o
heated to 110 C under air and stirred for 24 h. After cooling to room temperature, the catalyst
PCCS@CuI was separated by centrifugation. The reaction mixture was partitioned by adding the
ethyl acetate (20 mL) and water (20 mL). Subsequently, the organic phase was separated and the
aqueous phase was extracted with ethyl acetate (20 mL) twice. The combined organic phases were
washed with brine, dried over Na2SO4, and concentrated in vacuo. Then the crude product was
purified by column chromatography through silica gel, eluting with petroleum ether/ethyl acetate
solvent mixture, to give the pure product.
3. Results and Discussion
Performances of these functionalizedꢀchitosan supported copper complexes were evaluated in
the Ullmann CꢀN reaction of iodobenzene with imidazole. More details on the screening of
catalysts and optimization of the reaction conditions were summarized in Table 1. Initially, the
model reaction catalyzed by unmodifiedꢀchitosan@Cu was studied (Table1, entries 1ꢀ3), in which
CS@Cu(OAc)2 exhibited the highest activity. This result was consistent with previous report.20
A
preliminary comparison of the reaction catalyzed by functionalizedꢀchitosan@Cu with
unmodifiedꢀchitosan@Cu indicated that the fineꢀtuning on the backbone of chitosan promoted the

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activity of copper. Functionalizedꢀchitosan@Cu showed higher catalytic activity than
unmodifiedꢀchitosan@Cu (Table1, entries 4ꢀ12). For functionalizedꢀchitosan@Cu, various copper
sources, i.e. CuI, CuSO4 and Cu(OAc)2, were examined in this process, among which PCCS@CuI
was found to be the most effective catalyst, achieving an excellent yield (up to 99%). In addition,
a various of bases, e.g. Na2CO3, KOH, NaOH, K2CO3, Cs2CO3, NaOAc and NaHCO3, were tested,
and it was found that Cs2CO3 was the most ideal base (Table1, entries 5, 13ꢀ18). The mixture
solvent, i.e. DMSO, DMF and MeOH were studied, among which the reaction carried out in
foremost gave the highest yield (Table1, entries 17,19ꢀ20), while trying the reaction using water as
a solvent, the yield of the product is only 30% (Table1, entry 21). Other reaction temperature
o
including 70 C was screened, the yield was decreased from 99% to 75% (Table1, entry 22). In
summary, the optimum conditions for Ullmann CꢀN reaction were demonstrated as below: using
Cs2CO3 as base, DMSO as solvent, and PCCS@CuI as catalyst, under which condition the yield
of iodobenzene coupling with imidazole could reach up to 99%.
Table 1. The coupling reaction catalyzed by functionalizedꢀchitosan supported copper complex a
Entry
Catalyst
Base
Solvent
Yiled/% b
1
2
CS@CuSO4
CS@CuI
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
KOH
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
70
72
85
95
97
88
88
85
86
95
72
80
86
85
90
96
99
3
CS@Cu(OAc)2
PCCS@CuSO4
PCCS@CuI
4
5
6
PCCS@Cu(OAc)2
PACS@CuSO4
PACS@CuI
7
8
9
PACS@Cu(OAc)2
HBCS@CuSO4
HBCS@CuI
10
11
12
13
14
15
16
17
HBCS@Cu(OAc)2
PCCS@CuI
PCCS@CuI
K2CO3
PCCS@CuI
NaHCO3
NaOH
PCCS@CuI
PCCS@CuI
Cs2CO3

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18
19
20
21
22
PCCS@CuI
PCCS@CuI
PCCS@CuI
PCCS@CuI
PCCS@CuI
NaOAc
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
DMSO
MeOH
DMF
95
50
80
H2O
30
75c
DMSO
a Reaction conditions: iodobenzene 1a (1.0 mmol), imidazole 2a (1.2 mmol), base (2.0 mmol) and catalyst (0.05
o
b
mmol based on copper) in the solvent (3 mL), 110 C for 12 h. Isolated yield, c reaction was performed at
70 °C.
Catalyst PCCS@CuI were characterized by Fourier transform infrared spectroscopy (FTIR),
thermogravimetric analysis (TG), Xꢀray diffraction (XRD), scanning electron microscope (SEM),
energy disperse spectroscopy (EDS) and Xꢀray photoelectron spectroscopy (XPS). FTIR spectra
of CS, PCCS and PCCS@CuI are shown in Figure 2. For CS, the characteristic absorption peaks
appeared at 3400 cmꢀ1 (OꢀH stretching vibration), 2873 cmꢀ1 (CꢀH stretching vibration), 1591 cmꢀ1
(NꢀH bending vibration), 1375 cmꢀ1 (CꢀH bending vibration), 1150 cmꢀ1 (CꢀOꢀC stretching
vibration) and 1025 cmꢀ1 (CꢀO stretching vibration). Compared with the FTIR spectra of CS, a
new band at 1649 cmꢀ1 emerged in PCCS, which might be due to the C=N stretching vibration. In
addition, the peaks at 1569ꢀ1472 cmꢀ1 and 792 cmꢀ1 were foud, which can be attributed to the
bending vibration and stretching vibration of pyridine ring skeleton, respectively. These above
changes implied that pyridineꢀ2ꢀcarboxaldehyde was introduced to CS by the formation of Schiff
base. Differences were also found in the FTIR spectra of PCCS and PCCS@CuI: the band at 1649
cmꢀ1 (C=N stretching vibration) was changed to 1644 cmꢀ1 and turned broader, resulting from
coordination of the imine group and copper. Besides, the band of pyridine at 1600ꢀ1500 cmꢀ1 and
900ꢀ700 cmꢀ1 became weaker, which could be also attributed to complexation of copper with
pyridine.

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a
2873
1591
1375
3350
1150
894
b
1025
2885
1569 1471
3376
896
1649
1149
c
773
1026
2882
3358
1591
1361
1643
895
1150
772
1025
4000
3000
2000
1000
Wavenumber cmꢀ1
Figure 2. FTIR spectra of CS (a), PCCS (b) and PCCS@CuI (c)
TG curves of CS, PCCS and PCCS@CuI were shown in Figure3. It was obvious that they
had two different mass loss stages. The first stage was at the range of 50ꢀ100 oC, which might be
caused by the loss of water. In the second stage of mass loss, the decomposition of these materials
o
o
was occurred from 250 C to 350 C. Notably, the mass loss of PCCS@CuI was lower than the
others, due to the formation of Schiff base and coordination with the copper. Importantly,
PCCS@CuI was stable at up to 200 °C.

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100
80
60
40
20
0
c
b
a
100
200
300
400
500
600
700
800
Temperature (oC)
Figure 3. TG analysis of CS (a), PCCS (b) and PCCS@CuI (c)
As shown in Figure 4, the distinct morphologies of CS, PCCS and PCCS@CuI were recorded
via SEM. Compared with the relatively smooth surface of CS, the surface of PCCS became more
rough, due to the outcome of modification on the CS by grafting pyridineꢀ2ꢀcarboxaldehyde (in
Figure 4a and 4b). Further, the bright spot in Figure 4c suggested that CuI was chelated to PCCS.
Moreover, the copper of PCCS@CuI was measured by EDS (in Figure 4g), and a content of 2.05
mmol gꢀ1 was detected by ICP analysis. Therefore, it was demonstrated that copper was
successfully chelated to PCCS. The XRD patterns of CS, PCCS and PCCS@CuI were shown in
Figure 5. Obviously, the major characteristics of chitosan were the two peaks at 11.2o and 20.2o (in
Figure 5a), which was consistent with the literature reported previously 28. Furthermore, as shown
in Figure 5b, the peak at 11.2o disappeared and the peak at range of 20o became sharper, possibly
due to the formation of Schiff base and the decrease of free amino groups. Figure 5c exhibited
deposition of the composite film from a dispersion of CuI in PCCS, in which PCCS@CuI has
(111), (220) and (311) diffraction peaks of CuI film.

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g
Figure 4. SEM images of CS (a), PCCS (b), PCCS@CuI (c), recovered PCCS@CuI after the
second run (d), recovered PCCS@CuI after the third run (e), recovered PCCS@CuI after the fifth
run (f) and EDS of PCCS@CuI (g)

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a
b
c
10
20
30
40
50
60
70
80
90
2 Theta (Degree)
Figure 5. Xꢀray diffraction of CS (a), PCCS (b) and PCCS@CuI (c)
b
a
2p
932.3 ev
PCCS
PCCS@Cu
3/2
2p
1/2
952.1 ev
after the second run
Cu 2p
O1s
19.8 ev
I3d
C1s
PCCS@CuI
N1s
400
1000
800
600
200
0
965
960
955
950
945
940
935
930
Binding Energy (eV)
Binding Energy (eV)
c
d
N 1s
N 1s
398.2
398.6
399.3
399.6
399.2
398.
6
400.3
402
400
398
396
394
404
402
400
398
396
394
Binding Energy (eV)
Binding Energy (eV)
Figure 6. XPS spectra of PCCS and PCCS@CuI (a), Cu 2p peaks of PCCS@CuI and recovered

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PCCS@CuI after the second run (b), N 1s pattern of PCCS (c) and PCCS@CuI (d)
XPS spectra has been used to analyze the existence of different elements and to identify the
different valence of the same element. All peaks were corrected by taking the peak of C 1s at
284.6 eV. Figure 6a reveals the full spectrum of PCCS and PCCS@CuI, which appears two new
elements. The XPS peaks at 620 ev and 631 ev correspond to I 3d5/2 and 3d3/2 and at about 932.3
ev and 952.1 ev correspond to Cu 2p3/2 and 2p1/2,29 which in accordance with the results of EDS.
However, the absence of shakeꢀup satellite peak in the Cu 2p claims the +1 oxidation state of Cu is
present in the active catalyst in Figure 6b. With the weak of the peak of the Cu 2p and the
appearance of the noise peaks, which indicates that the copper ion has slightly lost after the second
run. The infrared analysis show that three forms of nitrogen: ꢀNH2, ꢀN=, N on the pyridine ring. In
Figure 6c and 6d, the typical N 1s XPS spectra of PCCS before and after Cu+ adsorption is
presented. Before adsorption, the peak at 399.3 eV, 398.6 ev and 398.2 ev were attributed to ꢀNHꢀ,
ꢀN=H and the N of pyridine in Figure 6c.30 After copper was chelated to PCCS, as shown in
Figure 6d, the peaks at 399.6 ev, 399.2 ev and 398.6 ev were attributed to ꢀNHꢀ,ꢀN= and N of
pyridine , simultaneously, it also exhibited a new N 1s binding energy at 400.3 ev, this
phenomenon demonstrates the formation of Cu···N–complexes,31 which is in accordance with the
results of FTIR.
Further extensive study focused on expanding the substrate scope for PCCS@CuI catalyzed
Ullmann CꢀN coupling reaction. Relative details were summarized in Table 2. It was shown that
electron withdrawing and donating effect of the groups substituted on aryl halide had much
influence on the CꢀN coupling with imidazole. When the electronꢀdonating substituents, e.g.
4ꢀOMe (3b), 4ꢀMe (3c), 4ꢀOEt (3d) and 4ꢀOCF3 (3g) were present at the aryl halide, the yields
were much better as compared to the ones with electronꢀwithdrawing substituents, e.g. 4ꢀF (3h),
4ꢀCl (3i), 4ꢀNO2 (3j) and 4ꢀAc (3k). In addition, aryl halide at orthoꢀsubstituents, e.g. OMe (3e)
and Me (3f), were well tolerated and the desired products were obtained with 85% and 83% yield,
respectively. In our previous report, substituent at orthoꢀposition catalyzed by βꢀCD@CuI, had
poor reactivity 27a. Thus, the catalytic activity of PCCS@CuI was impressive. Meanwhile, the
reactivities of different aryl halides were examined, and the order of corresponding reactivities
was PhI > PhBr > PhCl. Furthermore, different nucleophiles coupling with aryl halide were
performed, and several heterocycles, e.g. pyrrolidine (3i), nꢀbutylamine (3m), 2ꢀPyrrolidinone (3n),

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1Hꢀbenzoimidazole (3o), 4ꢀmethylꢀ1Hꢀimidazole (3p) and 5ꢀnitroindole (3q) gave the
corresponding products with good yields.
Table 2. The CꢀN coupling reaction catalyzed by PCCS@CuI a
a
Reaction conditions: aryl halides 1 (1.0 mmol), nitrogen nucleophiles 2 (1.2 mmol), Cs2CO3 (2.0 mmol) and
PCCS@CuI (25 mg, loading 5 mol%) in the DMSO (3 mL) at 110 oC for 24 h.
The PCCS@CuIꢀcatalyzed protocol was expanded to the Ullmann CꢀS coupling reaction of
aryl halides with sulfinate salts, and the results were shown in Table 3. To our delight, aryl

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sulfinate could react efficiently with iodobenzene, and targeted product was obtained with
excellent yields. Moreover, it was notable that the aryl iodide with electronꢀdonating substituents
were more reactive than the ones with electronꢀwithdrawing substituents. Besides, the steric
hindrance by orthoꢀsubstituents decreased the efficiency of this reaction. In addition, the
reactivities of aryl chloride and aryl bromide with sulfinate salts were lower than the one of aryl
iodide. For sulfinates, neither electron donating nor withdrawing groups substituted on the ring
showed obvious influences on the yields.
Table 3. The CꢀS coupling reaction catalyzed by PCCS@CuI a
a
Reaction conditions: aryl halides 1 (1.0 mmol), aryl sulfinate 4 (1.2 mmol), Cs2CO3 (2.0 mmol) and
PCCS@CuI (25 mg, loading 5 mol%) in the DMSO (3 mL) at 110℃ for 24 h.

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100
80
60
40
20
0
1
2
3
4
5
Run
Figure 7. Recycling and reuse of PCCS@CuI as catalyst
As a further advantage of PCCS@CuI, it can be easily separated from the reaction mixture
and reused. Herein, PCCS@CuI was removed from the reaction mixture by centrifugal filtration,
and then the separated catalyst was washed by 6 times using the deionized water, and dried at
50oC under vacuum, to reuse it directly again. In addition, the reusability of PCCS@CuI was
studied by the above Ullmann CꢀN model reaction. The results of reusable catalyst were shown in
Figure 7. It was obvious that the catalyst had excellent catalytic effect after being reused five times.
Moreover, the SEM of PCCS@CuI after being reused was shown in Figure 4dꢀ4f, in which there
are bright spots. These bright spots indicate the copper ions were attached to the complex.
Compared Figure 4c with Figure 4d, there is no significant loss of copper ions after the catalyst
being reused twice. Although some copper ions are missing after the catalyst being reused fifth run,
there are still much copper ions on the surface. Therefore, it gave obvious evidences to its
structural stability. The copper of recovered catalyst was measured by EDS (see the ESI in Figure
S3), and a content of 1.89 mmol gꢀ1 was detected by ICP analysis.

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4. Conclusions
In summary, we have successfully designed and prepared a green and efficient copper catalyst
based on the Schiffꢀbase chitosan. Schiffꢀbase chitosan was synthesized by the condensation of
pyridineꢀ2ꢀcarboxaldehyde and amino group on chitosan. The applicability of the catalyst was
proved by Ullmann reaction, in which good to excellent yields of CꢀN and CꢀS coupling reaction
were obtained. In addition to high catalytic activity, the functionalizedꢀchitosan supported copper
complex is easily recoverable and reused stably.
5. Acknowledgements
The authors are grateful for the financial support from the Natural Science Foundation of
China (21476194, 21606104), the National Key Research and Development Program of China
(2016YFB0301800) and the Opening Foundation from Zhejiang Provincial Key Laboratory of
Advanced Chemical Engineering Manufacture Technology (ACEMTꢀ17ꢀ03).
References
(1)
(a) Carroll, M. P.; Guiry, P. J. Chem. Soc. Rev 2014, 43, 819(b) Bariwal, J.; Van der Eycken, E.
Chem. Soc. Rev 2013, 42, 9283(c) Enugala, R.; Carvalho, L. C. R.; Pires, M. J. D.; Marques,
M. M. B. Chem-Asian J 2012, 7, 2482(d) Monnier, F.; Taillefer, M. Angew. Chem. Int. Ed
2008, 47, 3096.
(2)
(a) Beletskaya, I. P.; Cheprakov, A. V. Coord. Chem. Rev 2004, 248, 2337(b) Hassan, J.;
Sevignon, M.; Gozzi, C.; Schulz, E.; Lemaire, M. Chem. Rev 2002, 102, 1359.
Klapars, A.; Antilla, J. C.; Huang, X. H.; Buchwald, S. L. J. Am. Chem. Soc 2001, 123, 7727.
(a) Klapars, A.; Huang, X. H.; Buchwald, S. L. J. Am. Chem. Soc 2002, 124, 7421(b) Antilla, J.
C.; Baskin, J. M.; Barder, T. E.; Buchwald, S. L. J. Org. Chem 2004, 69, 5578(c) Surry, D. S.;
Buchwald, S. L. Chem. Sci 2010, 1, 13.
(3)
(4)
(5)
(6)
(a) Kwong, F. Y.; Klapars, A.; Buchwald, S. L. Org. Lett 2002, 4, 581(b) Yang, B.; Mao, Z. X.;
Zhu, X. H.; Wan, Y. Q. Catal. Commun 2015, 60, 92.
(a) Cristau, H. J.; Cellier, P. P.; Spindler, J. F.; Taillefer, M. Chem.eur. J 2004, 10, 5607(b)

Page 17 of 18
New Journal of Chemistry
View Article Online
DOI: 10.1039/C8NJ02677G
Wang, Y.; Gao, J. Y.; Zhao, M. D.; Li, J. M. Chem Res Chinese U 2015, 31, 549.
(7)
(8)
(a) Ma, D. W.; Cai, Q. Synlett 2004, 128(b) Tang, J. M.; Xu, B. Q.; Mao, X.; Yang, H. Y.;
Wang, X. X.; Lv, X. J. Org. Chem 2015, 80, 11108.
(a) Shafir, A.; Buchwald, S. L. J. Am. Chem. Soc 2006, 128, 8742(b) de Lange, B.;
LambersꢀVerstappen, M. H.; van de Vondervoort, L. S.; Sereinig, N.; de Rijk, R.; de Vries, A.
H. M.; de Vries, J. G. Synlett 2006, 3105.
(9)
Altman, R. A.; Buchwald, S. L. Org. Lett 2006, 8, 2779.
(10)
Zhang, C.; Huang, B.; Bao, A. Q.; Li, X.; Guo, S.; Zhang, J. Q.; Xu, J. Z.; Zhang, R.; Cui, D.
M. Org. Biomol. Chem 2015, 13, 11432.
(11)
(12)
(a) Cheng, D. P.; Gan, F. F.; Qian, W. X.; Bao, W. L. Green Chem 2008, 10, 171(b) Wen, M.;
Shen, C.; Wang, L. F.; Zhang, P. F.; Jin, J. Z. RSC Adv 2015, 5, 1522(c) Suresh, P.; Pitchumani,
K. J. Org. Chem 2008, 73, 9121.
(a) Zhang, Y.; Yang, X. Y.; Yao, Q. Z.; Ma, D. W. Org. Lett 2012, 14, 3056(b) Wang, Y. B.;
Zhang, Y.; Yang, B. B.; Zhang, A.; Yao, Q. Z. Org. Biomol. Chem 2015, 13, 4101.
Zhou, W.; Fan, M. G.; Yin, J. L.; Jiang, Y. W.; Ma, D. W. J. Am. Chem. Soc 2015, 137, 11942.
Handzlik, J.; Ogonowski, J.; Stoch, J.; Mikolajczyk, M. Catal. Lett 2005, 101, 65.
(a) Gu, L.; Ma, D.; Yao, S.; Wang, C.; Shen, W.; Bao, X. Chem. Commun 2010, 46, 1733(b)
Iwasaki, M.; Shinjoh, H. Chem. Commun 2011, 47, 3966.
(13)
(14)
(15)
(16)
(17)
Lei, Z. Q. React. Funct. Polym 2000, 43, 139.
(a) Polshettiwar, V.; Luque, R.; Fihri, A.; Zhu, H.; Bouhrara, M.; Basset, J. M. Chem. Rev
2011, 111, 3036(b) Baig, R. B. N.; Varma, R. S. Chem. Commun 2012, 48, 2582(c) Ayad, M.
M.; Amer, W. A.; Kotp, M. G. Mol. Catal 2017, 439, 72(d) Doustkhah, E.; Rostamnia, S.;
Gholipour, B.; Zeynizadeh, B.; Baghban, A.; Luque, R. Mol. Catal 2017, 434, 7.
Marques, M. M.; Queda, F.; Carvalho, L.; Santos, C. t. Chem Asian J 2016, 11.
(a) Sudheesh, N.; Sharma, S. K.; Khokhar, M. D.; Shukla, R. S. J. Mol. Catal. A: Chem 2011,
339, 86(b) Zhao, X.; Wei, Z.; Zhao, Z.; Miao, Y.; Qiu, Y.; Yang, W.; Jia, X.; Liu, Z.; Hou, H.
ACS Appl Mater Inter 2018.
(18)
(19)
(20)
(21)
(22)
Shen, C.; Xu, J.; Yu, W. B.; Zhang, P. F. Green Chem 2014, 16, 3007.
Xu, D.; Hein, S.; Wang, K. Mater. Sci. Technol 2013, volume 24, 1076.
(a) Frindy, S.; Primo, A.; Lahcini, M.; Bousmina, M.; Garcia, H.; El Kadib, A. Green Chem

New Journal of Chemistry
Page 18 of 18
View Article Online
DOI: 10.1039/C8NJ02677G
2015, 17, 1893(b) Hu, D.; Cui, Y.; Dong, X.; Fang, Y. React. Funct. Polym 2000, 48, 201.
Makhubela, B. C. E.; Jardine, A.; Smith, G. S. Green Chem 2012, 14, 338.
Xia, C. G.; Sun, W.; Wang, H. W. New J. Chem 2002, 26, 755.
(23)
(24)
(25)
Lei, X.; Zhou, D. J.; Li, T.; Ji, X. F.; Huang, M. Y.; Jiang, Y. Y. React. Funct. Polym 2004, 58,
117.
(26)
(27)
Anuradha; Kumari, S.; Pathak, D. D. Tetrahedron Lett 2015, 56, 4135.
(a) Chen, L.; Wang, C.; Zhou, L.; Sun, J. Adv. Synth. Catal 2014, 356, 2224(b) Iwasaki, F.;
Onomura, O.; Mishima, K.; Kanematsu, T.; Maki, T.; Matsumura, Y. Tetrahedron Lett 2001,
42, 2525(c) Nugent, T. C.; ElꢀShazly, M. Adv. Synth. Catal 2011, 353, Cp6(d) Nugent, T. C.;
ElꢀShazly, M. Adv. Synth. Catal 2010, 352, 753.
(28)
(29)
Zhang, H.; Dang, Q.; Liu, C.; Cha, D.; Yu, Z.; Zhu, W.; Fan, B. ACS Appl Mater Inter 2017, 9,
11144.
(a) Saha, S.; Das, S.; Sen, D.; Ghorai, U. K.; Mazumder, N.; Gupta, B. K.; Chattopadhyay, K.
K. J. Mater. Chem C 2015, 3, 6786(b) Kumar, M.; Bhatt, V.; Nayal, O. S.; Sharma, S.; Kumar,
V.; Thakur, M. S.; Kumar, N.; Bal, R.; Singh, B.; Sharma, U. Catal. Sci. Technol 2017, 7,
2857.
(30)
(31)
(a) Tong, J.; Li, Z.; Xia, C. J. Mol. Catal A :Chem 2005, 231, 197(b) Zeng, L.; Chen, Y.;
Zhang, Q.; Guo, X.; Peng, Y.; Xiao, H.; Chen, X.; Luo, J. Carbohydr. Polym 2015, 130, 333(c)
Teng, S. X.; Wang, S. G.; Liu, X. W.; Gong, W. X.; Sun, X. F.; Cui, J. J.; Gao, B. Y. Colloids
Surf. A 2009, 340, 86.
Zhou, Y. T.; BranfordꢀWhite, C.; Nie, H. L.; Zhu, L. M. Colloids Surf. B 2009, 74, 244.