Copper-loaded hypercrosslinked polymer decorated with pendant amine groups: A green and retrievable catalytic system for quick [3 + 2] Huisgen cycloaddition in water

Article abstract of DOI:10.1039/c6ra05234g

A novel heterogeneous copper catalyst based on a 3D-network polymer containing pendant amine groups was synthesized via post-functionalization of the polymeric backbone followed by incorporation of copper(i) ions. Catalytic activity of the newly designed

Full text of DOI:10.1039/c6ra05234g

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: A.
mouradzadegun and M. mostafavi, RSC Adv., 2016, DOI: 10.1039/C6RA05234G.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Page 1 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
Copper-loaded Hypercrosslinked Polymer Decorated with
Pendant Amine Groups: A Green and Retrievable Catalytic
System for Quick [3+2] Huisgen Cycloaddition in Water
Arash Mouradzadegun*, Mahsa Mostafavi
Department of Chemistry, Faculty of Science, Shahid Chamran University, Ahvaz, Iran
*
Corresponding author: Fax +98(61)33337009; Tel +98(61)33331042
Eꢀmail: arash_m@scu.ac.ir
Abstract
A novel heterogeneous copper catalyst based on 3Dꢀnetwork polymer containing pendant
amine groups was synthesized via postꢀfunctionalization of the polymeric backbone followed
by incorporation of copper(I) ions. Catalytic activity of the newly designed catalyst was
tested in a oneꢀpot synthesis of 1,4ꢀdisubstituted 1,2,3ꢀtriazoles by click reactions between
primary halides, sodium azide and terminal acetylenes in water under aerobic conditions. It
increases the reaction rate many fold when compared with common transition metal catalysts.
The synergistic incorporation of the porous matrix and active sites of this new catalyst
offered a unique combination for effective catalyticꢀsubstrate interactions, which made it a
new class of solidꢀsupport transition metal catalysts for chemical preparation.
Keywords: 3Dꢀnetwork polymer, 1,4ꢀdisubstituted 1,2,3ꢀtriazoles, solidꢀsupport transition
metal catalysts, heterogeneous copper catalyst, [3+2] Huisgen Cycloaddition
1

RSC Advances
Page 2 of 25
View Article Online
DOI: 10.1039/C6RA05234G
Introduction
Sustainable chemistry focuses on the design, manufacture, and use of chemicals and chemical
processes that cause little or no pollution potential or environmental risk and are both
economically and technologically feasible [1]. Since optimization of existing chemical
processes together with the development of novel, environmentally friendly processes depend
greatly on improvement of catalyst performance; the catalysis has a strong impact on the
development of modern sustainable chemistry.
Recently, solidꢀsupport heterogeneous catalysis have drawn great interest in industrial
processes owing to their potential advantages over solutionꢀbased homogeneous catalysis,
such as the easier operation/purification and recycling catalysts from reaction environments
which lead to improved processing steps, better process economics, and environmentally
friendly manufacturing [2]. However, compared with the similar homogeneous catalysis, the
heterogeneous catalysis usually suffered from decreased reactivity owing to the less effective
interactions between catalytic centers and reactants. This is challenging for transition metalꢀ
promoted organic transformations, in which a good mix between catalysts and substrates is
often required for effective reactions.
In order to solve this problem, porous materials have been proposed as a new type of solidꢀ
support for heterogeneous catalysis with much higher efficiency in catalystꢀreactant
interactions [3]. In this context, inorganic porous materials, such as mesoporous silica and
zeolite have received considerable attention. However, defects such as need to expensive
organic surfactants or templates and calcinations at high temperature for obtaining opening
channels have restricted their widespread practical applications on an industry scale.
Compared with inorganic supports, porous organic polymers (POPs), a new class of porous
materials with a crossꢀlinked amorphous organic framework, have emerged as a sustainable
catalyst support owing to their advantages in good dispersion of active sites, poreꢀsurface
2

Page 3 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
modifiability and the adsorption of reactant molecules on the material surface [4]. Moreover,
owing to the inherited nature of the organic pores, the cavities of the organic polymers are the
best mimic of the chemical environment in the organic solventꢀmediated homogeneous
catalysis and thus help in the maintenance of the catalyst reactivity. These features, coupled
with their biodegradability and green nature, make POPs attractive materials to organic and
industrial chemistry.
Although a variety of POPs have been reported, some of them suffer from one or more
defects in their synthetic or functionalization routes and properties including long reaction
times, multiple steps for synthesis, functionalization via copolymerization or further postꢀ
polymerization under harsh reaction conditions, the use of expensive catalysts, solubility in
various solvents, and low thermal and/or chemical stability. Therefore, developing and
applying new POPs for heterogeneousꢀtype catalytic systems, which may quickly move from
the laboratory to green industrial plants, have received increased attention.
3Dꢀnetwork polymer based on calix[4]resorcinarene could be ideal candidate for the
development of solidꢀsupport POPs due to both their simple synthesis and the unique
properties such as straightforward functionalization route via postꢀfunctionalization without
undergoing copolymerization or further postꢀpolymerization, versatile chemical modification
(acylation, alkylation and silylation of hydroxyl group and nucleophilic aromatic substitution
on the aromatic rings) and high thermal and chemical stability.
Despite convenient properties and significant potential of 3Dꢀnetwork polymer based on
calix[4]resorcinarene in functionalization under mild reaction conditions without the use of
acidic or basic catalyst, so far, there have been no reports on the use of these porous organic
polymer as heterogeneous organometallic catalyst.
1,2,3ꢀtriazole derivatives, five membered nitrogen containing heterocycles, have received
considerable interest because of their tremendous applications in various research fields
3

RSC Advances
Page 4 of 25
View Article Online
DOI: 10.1039/C6RA05234G
including organic synthesis, material science and cell biology [5]. The classical method for
the synthesis of these derivatives, thermal 1,3ꢀdipolar cycloaddition of azides with alkynes,
suffers from a few disadvantages such as low yields and lack of selectivity. To overcome
these drawbacks, the Cu(I)ꢀcatalyzed azideꢀalkyne cycloaddition (CuAAC) has rapidly
crossed traditional disciplinary boundaries [6]. Toxicity of copper ions to cells and organisms
coupled with high cost of transition metal catalysts has led to an increasing interest in
immobilizing these catalysts onto a support. This class of supported reagent can facilitate
both the isolation and recycling of the catalyst by filtration, thus providing environmentally
cleaner processes.
Due to extensive practical validation of this transformation, several examples of polymerꢀ
supported catalysts have been reported in the literature. However, in most of these cases,
nonporous polymer and porous polymers with low porosity and surface area were used
generally which limited the interaction between substrates and catalytic sites. Furthermore,
most of the reliable CuAAC protocols are performed under anaerobic conditions. These
defects coupled with the need to extended reaction times and the use of organic solvents
render the approaches unsatisfactory from the standpoint of green chemistry.
Under this light, as part of our continuing efforts to develop high performance and
environmentally friendly procedures for various important reactions and transformations [7]
and due to our new interest in the application of the 3Dꢀnetwork porous polymer based on
calix[4]resorcinarene for the preparation of biologically important molecules [8], herein, we
have attempted to design, for the first time, a new type of porous network polymer containing
a high concentration of amine sites as a more effective heterogeneous catalyst in promoting
CuAAC reaction under aerobic conditions in water.
4

Page 5 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
Experimental
Chemicals were purchased from Fluka, Merck and Aldrich chemical companies and used
1
without further purification. Products were characterized by physical data, IR, HNMR,
1
3
CNMR and HRMS spectra. Melting points were determined on a Thermo Scientific 9200
1
apparatus. IR spectra were obtained on a Bomen MB:102 FTꢀIR spectrophotometer. HNMR
13
and CNMR spectra were recorded on a Bruker spectrometer at 400 and 100 MHz,
respectively, in CDCl or DMSO with tetramethylsilane as an internal standard. HRMS
3
spectra were measured on an Agilent 5975 mass spectrometer and elemental analyses were
performed on a Thermo Finnigan Flash EA 1112 CHNSꢀAnalyzer. The polymer morphology
was examined by AFM (Nano Wizard II) and FEꢀSEM (MIRA3 TESCAN)). The thermal
stability of functionalized polymer was investigated by NETZSCH STA 409 PC/PG under a
ꢀ1
2
nitrogen atmosphere (rate of N ≈ 1 L h ). The catalyst copper content was determined by
atomic absorption spectrophotometer (GBC Avanta instrument) and EDS (SAME, France)
analysis.
Monitoring of the reactions and the purity determination of the products were accomplished
by TLC on PolyGram SILG/UV 254 silica gel plates.
Synthesis of calix[4]resorcinarene 1
Calix[4]resorcinarene was prepared according to a previously reported procedure [9].
Synthesis of the 3D-network polymer based on calix[4]resorcinarene 2
The desired polymer was synthesized by adding 42 mmol of formaldehyde to 14 mmol of the
prepared calix[4]resorcinarene dissolved in 40 mL NaOH solution (10%) at room
temperature. The resultant mixture was heated to 90 °C and maintained at this temperature
for 20 h. Next, the excess alkali was washed out of the gel formed with cold water. The gel
5

RSC Advances
Page 6 of 25
View Article Online
DOI: 10.1039/C6RA05234G
was allowed to stand at 100 °C for 1 h. Then, the gel was transformed into the acidic form by
treatment with the 0.1 M HCl solution. The resulting solid was dried at 100 °C for 10 h [10].
Synthesis of novel amine-functionalized polymer 3
The synthesized polymer 2 obtained from the above procedure (1.0 g), 3ꢀ
(
triethoxysilyl)propylamine (4.0 g, 18 mmol) were introduced into 50ꢀmL roundꢀbottomed
flask containing 10 mL H O/EtOH at room temperature. The reaction mixture was heated to
0 °C and stirred at this temperature for 20 h. The desired amineꢀfunctionalized polymer 3
was collected by filtration and washed several times with hot toluene before being dried at
00 °C.
2
9
1
Determination of the amount of amine functionalities grafted onto the polymer
The amount of amine functionalities grafted onto the polymer was determined by elemental
analysis to be 3.5 mmol per gram of dry polymer.
Preparation of copper(I) iodide salt
To a stirred solution of 10 g copper(II) iodide in 10 mL water was added slowly at room
2 3
temperature a solution of 7.6 g of anhydrous sodium sulfite, Na SO , in 50 mL water. The
copper(I) iodide solution first became very dark brown, and then white copper(I) iodide
slowly separated. After all the sodium sulfite solution was added and the mixture stirred
thoroughly, the copper(I) iodide settled readily and the supernatant liquid was faintly green.
The precipitate and supernatant liquid were then poured into about a liter of water to which 1
g of sodium sulfite and 2 mL of concentrated hydrochloric acid were added, and the mixture
was stirred well and allowed to stand until all the copper(I) iodide was settled. The
supernatant liquid was carefully decanted and the precipitate was quickly washed onto a
6

Page 7 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
suction filter (sintered glass type preferred) with dilute sulfurous acid solution. Care should
be taken that a layer of liquid covers the salt in the funnel at all times. The copper(I) iodide
was then washed four or five times with 20 to 25 mL of glacial acetic acid. During this
washing process the suction should be adjusted so that the washed liquid would be sucked
through rather slowly. When only a thin film of liquid covered the solid, the next portion of
glacial acetic acid was added. The walls of the funnel should be washed each time with the
washing liquid. The washed copper(I) iodide with glacial acetic acid was then washed by
three 30ꢀmL of absolute alcohol and six 15ꢀmL of anhydrous ether in exactly the same way.
After the last portion of ether was removed fairly completely by applying suction for about
30 seconds, the white solid (with filter paper removed) was transferred quickly to a
previously dried watch glass and placed in an oven (75 to 100 ºC) for 20 to 25 minutes. The
sample should be preserved in an airtight bottle. The copper(I) iodide prepared by this
method is a white crystalline powder that remains practically unchanged for an indefinite
period if kept dry. If all the alcohol is not removed during the washing process, the copper(I)
iodide may become slightly discolored on heating or standing. Some samples of anhydrous
ether tend to impart a gray tint to the product [11].
Preparation of novel polymer-supported copper(I) catalyst 4
In a small Schlenk tube, amineꢀfunctionalized polymer 3 (1.0 g) was mixed with CuI (0.017
g, 0.1 mmol) in DMF (5 mL). The mixture was stirred for 4 h under a N atmosphere at r.t.
2
The solid was isolated by filtration and washed consecutively with acetone (5 mL) and
MeOH (5 mL). Finally the resultant product was dried at r.t. for 16 h.
7

RSC Advances
Page 8 of 25
View Article Online
DOI: 10.1039/C6RA05234G
Determination of the copper content of catalyst 4
The catalyst copper content was measured using a GBC Avanta, Australia, atomic absorption
spectrophotometer (AAS) to be 1.26 percent of the resulted catalyst 4.
General procedure for the one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles 7A-F
Benzyl bromide (0.118 mL, 1 mmol) and sodium azide (0.065 g, 1 mmol) were charged into
a 25 mL roundꢀbottomed flask containing 3 mL water. Then, phenylacetylene (0.102 g, 1
mmol) and polymerꢀsupported copper catalyst 4 (0.258 g, 0.05 mmol) were added to the
reaction mixture. The mixture was heated and stirred under reflux condition till the reaction
completion (TLC monitoring). After cooling to r.t., the reaction mixture was vacuumꢀfiltered
through a sintered glass funnel and washed with ethyl acetate (5 mL). The resulting solution
was poured in a water/ethyl acetate mixture. After extraction of the aqueous phase with ethyl
acetate, the combined organic phase was dried over magnesium sulfate and filtered. The
resultant solution was concentrated and pure crystalline product was isolated through
filtration.
Recycling of the polymer-supported copper catalyst 4
After the reaction had been carried out, the mixture was vacuumꢀfiltered onto a sinteredꢀglass
funnel. The residue was consecutively washed with CH Cl (5 mL), Et O (5 mL), EtOH (5
2
2
2
mL), and nꢀhexane (5 mL). The solid catalyst dried under vacuum after each cycle, and then
reused for the next reaction.
8

Page 9 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
Results and discussion
This research is essentially focused on developing a novel copper(I)ꢀimmobilized catalytic
system on the basis of calix[4]resorcinarene that can efficiently modify the CuAAC reaction
conditions by combining the advantages of both homogeneous and heterogeneous catalysts.
To achieve this objective, the 3Dꢀnetwork polymer 2 was prepared by the reaction of
resorcinol and acetaldehyde, followed by the polycondensation of calix[4]resorcinarene 1
with formaldehyde [10] as outlined in scheme 1.
<
Scheme 1>
The structure of compound 1 was established unambiguously from the spectroscopic (IR,
1
13
HNMR, CNMR) data (see ESI†). The formation of polymer 2 was also confirmed and
characterized by atomic force microscopy (AFM), Xꢀray diffraction (XRD) and scanning
electron microscope (SEM) [8a] (available in the ESI†).
Among the families of ligands reported for CuAAC reaction, amine groups are prominent as
they produce highly robust catalysts capable of conferring outstanding catalytic activity on
copper center, often at extremely low catalytic loading. In this regard, we attempted to
design, for the first time, a amine functionalized 3Dꢀnetwork polymer based on
calix[4]resorcinarene.
To this end, the prepared polymer 2 was treated with 3ꢀ(triethoxysilyl)propylamine (APTES)
in common solvents to undergo a condensation reaction, yielding amine functionalized
polymer 3 in a oneꢀstep modification reaction (Scheme 2).
<
Scheme 2>
The loading amount of the amine moieties on the polymer was determined by elemental
analysis. As shown in table 1, solvent and the amount of added linker (APTES) were
optimized. The best result were obtained when a 1:1 water:ethanol mol ratio in the presence
of 18 mmol of APTES per gram of polymer was used (Table 1, entry 4). Adding further
9

RSC Advances
Page 10 of 25
View Article Online
DOI: 10.1039/C6RA05234G
amount of APTES didn’t change the extent of attached amine groups notably (Table 1, entry
).
5
<Table 1>
It is noteworthy to highlight that the nitrogen analysis of supported amine 3 (N, 4.95%)
indicates that 3.5 mmol of the amine moieties were grafted onto the surface per 1 g of the
polymer which show more potential for covalently anchored amine moieties than most
previously reported solidꢀsupports [12]. Furthermore, the amine polymer 3 is effectively
insoluble in various solvents, including water, methanol, ethanol, dimethyl sulfoxide,
N,Ndimethylformamide, acetonitrile, dichloromethane, and chloroform. These properties
make polymer 3 suitable for being used as an efficient solidꢀsupported reagent or catalyst in
various reaction media.
The formation of amine functionalized polymer 3 is of considerable interest since it is the
first example of loading of basic groups as well as acidic groups [8b] on the 3Dꢀnetwork
polymer based on calix[4]resorcinarene.
The significant properties of amine functionalized polymer 3 encouraged us to characterize
its structure.
ꢀ1
IR spectrum of the functionalized polymer 3 is consisted of a broad band in 1120 cm which
ꢀ1
is representative of SiꢀO bonds. On the other hand, broad band in 3100ꢀ3600 cm revealed
that all of the phenolic hydroxyl groups of polymer 2 are not functionalized (see ESI†).
In order to gain an insight into the topography of the surface, AFM was utilized (Fig. 1, a,b).
All of the AFM scans were taken in ambient air in tapping mode, which is ideal for this kind
of polymer [13]. More details could be obtained from the 3D height and phase plots (Fig. 1,
b). Since the amine functionalized polymer 3 shows smaller pores (about 57 nm in diameter,
Fig. 2) than polymer 2 (300 nm in diameter, see ESI†), it can be concluded that the
propylamine moieties are successfully grafted onto the polymeric backbones.
1
0

Page 11 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
<
Fig. 1>
Fig. 2>
<
Scanning electron microscope of the functionalized polymer 3 was undertaken on a FEꢀSEM
MIRA3 TESCAN) instrument (Fig. 3). The SEM images confirmed that the average size of
pores is in agreement with the AFM data.
(
<Fig. 3>
With these results in hand, we believe that 3Dꢀnetwork functionalized polymer 3 could be
introduced as a proper porous surface for the inclusion of atomic or molecular guests in
chemical reactions.
To investigate the thermal behavior of the functionalized polymer 3 including thermal
stability, moisture content and possible decomposition of volatile materials, its thermal
gravimetric analysis was carried out under nitrogen atmosphere with a NETZSCH STA 409
PC/PG, from room temperature to 1100 ºC, with a heating rate of 10 ºC per minute (Fig. 4).
According to TG diagram, the weight loss processes of the functionalized polymer could be
divided into 3 stages. The first weight loss in the range of 40ꢀ120 ºC is attributed to the
release of physically adsorbed water molecules and organic solvents. A 31.07% weight loss
at 200ꢀ770 ºC is probably corresponding to the thermal decomposition of the attached amine
linkers and some parts of polymer which is representative of high thermal stability of this
polymeric support. Ultimately the weight loss in the range of 770ꢀ1100 ºC is associated with
decomposition of the polymeric network. Thus, the TGA curve also conveys the clear
information that propylamine chains are successfully grafted onto the polymeric backbones.
Fortunately, the TGA of polymer 3 demonstrated high thermal stability, with decomposition
starting at around 200 °C. The thermal stability of this functionalized polymer allows heatꢀ
demanding chemical reactions along with its backbone and side chains without leaching of
1
1

RSC Advances
Page 12 of 25
View Article Online
DOI: 10.1039/C6RA05234G
the active species, thereby providing an excellent means of polymer support and catalyst for
conducting chemical reactions.
<Fig. 4>
After the characterization of novel functionalized polymer 3, in the second step, the resultant
amine functionalized polymer was further reacted with CuI in DMF to form the
corresponding 3Dꢀnetwork polymerꢀsupported Cu(I) catalyst 4 (Scheme 3).
<
Scheme 3>
The copper content of catalyst, measured by a GBC Avanta, Australia, atomic absorption
spectrophotometer (AAS), showed the value of about 1.26 percent of the resulted catalyst
(0.2 mmol Cu per gram of the dry polymerꢀsupported catalyst 4).
Energy dispersive Xꢀray spectroscopy (EDS) was also employed to investigate the elemental
composition of the novel catalyst 4 using a SAME, France instrument (Fig. 5).
<Fig. 5>
The copper loadings predicted from EDS analysis (0.62 wt%) does not present a clear trend
as we observed in AAS analysis (1.26 wt%). The EDS analysis is capable of measuring
copper present on the surface of the catalyst support and cannot detect the copper present
inside the pores of the catalyst. So, this absence of the expected trend as in AAS analysis of
the copper loading gave us confidence that porous structure of catalyst 4 as well as sideꢀ
chains have the vital role in supporting of Cu(I) onto the catalyst.
With the copperꢀincorporated 3Dꢀnetwork polymer 4 in hand, the reactivity of this new type
of solidꢀsupport transition metal catalyst was investigated. In this regard, owing to the
widespread applications of 1,2,3ꢀtriazole derivatives, we decided to investigate the synthetic
applicability of 4 as a transition metal catalyst for the rapid and efficient construction of these
privileged compounds according to the principles of green chemistry.
1
2

Page 13 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
For this purpose, benzyl bromide, phenylacetylene and sodium azide were chosen as the
model substrates to optimize the reaction conditions including the amount of catalyst, solvent
and reaction temperature.
Since, water is the most easily available, economical and environment friendly solvent in the
word, we first attempted to perform the soꢀcalled click reaction in distilled water medium.
To our pleasure, the reaction of model substrates in the presence of catalyst 4 at room
temperature in water was successful and the corresponding 1,4ꢀdisubstituted 1,2,3ꢀtriazole
2
(7A) were obtained in excellent yield without N atmosphere. Different solvents and solventꢀ
coꢀsolvent mixtures were tested, and water was found to be the most effective medium for
this reaction.
Encouraged by the excellent result, further experiments were designed to survey catalytic
virtue of catalyst 4 in the same reaction. As shown in table 2, the best yield (97%) and the
shortest time (5 min) were obtained in the presence of 5 mol% catalyst 4 under reflux
conditions (Table 2, entry 3).
To confirm the catalyst efficiency, control experiments were also carried out. Initially, the
model reaction was probed in the absence of any catalyst. In this case, only a trace amount of
product was detected after 3 h (Table 2, entry 6). Next, the model reaction was examined in
the presence of CuI as a homogeneous catalyst and notably decreased yield was resulted
(Table 2, entry 7).
<Table 2>
To examine the utility and generality of this approach, we have performed the reaction under
optimized reaction conditions for the synthesis of a wide variety of 1,2,3ꢀtriazole derivatives.
Representative results of this synthetic modification are listed in table 3.
<Table 3>
1
3

RSC Advances
Page 14 of 25
View Article Online
DOI: 10.1039/C6RA05234G
As it can be observed in table 3, all the examined benzyl halides with electron donating or
electron withdrawing groups in all positions of the phenyl ring (ortho, meta and para) were
well compatible with the reaction conditions. Gratifyingly, it was found that the reactions run
in air with no need for purification on silica gel.
The products were identified by comparing their physical and spectral data with those of
authentic samples.
Considering the above results, we believe that high yields, short reaction times and reactivity
of catalyst 4 might be attributed to the existence of a synergistic effect between the cavities of
the polymeric support and the immobilized amine groups. The adsorption of substrate into the
pores of the functionalized polymer based on hydrophobic interaction between the substrates
and polymeric backbone could increase the local concentration of substrates around the active
sites of the polymer and effectively promote the reaction.
It is noteworthy that all the reactions proceed without any reducing agent which is commonly
used in analogous reactions to prevent Cu(I) from being oxidized to Cu(II). It seems that the
porous polymeric matrix could effectively protect the active catalytic sites, copper(I) ions,
from interactions leading to oxidation and degradation. On the other hand, the endꢀ
functionalized polymer with amine moieties prepares suitable positions for copper ions
adsorption to make them stabilized [14].
Based on the previous discussion, a possible mechanism for the sequence of events could be
expressed such as authentic samples [21]. In a first stage, the nucleophilic substitution was
carried out on alkyl/aryl halides affording the respective benzyl azides. The amine groups
supported on catalyst 4 could function as proton accepters from terminal alkynes activating
them to prepare acetylideꢀcopper complex. A newly formed acetylideꢀcopper complex would
interact with the azide, activating it toward nucleophilic attack of the acetylide carbon to the
1
4

Page 15 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
‘end’ nitrogen atom of the azide. Subsequent ring contraction of the generated metallacycle
would lead to a copperꢀtriazolide, a direct precursor of the reaction product upon protonation.
It is well known that the reusability of a catalytic system is the key factors that identify
whether it has potential applications in industry. Considering this fact, in order to test the
catalyst reusability, the reaction of model substrates in the presence of catalyst 4 was carried
out under optimal reaction conditions. After completion of each reaction, the catalyst was
recovered by simple filtration through a sintered glassꢀbed, washed with dichloromethane,
diethyl ether, ethanol and nꢀhexane, dried and reused. The results illustrated in fig. 6 show
that the catalyst can be reused for up to five cycles without significant loss in its activity.
Moreover, copper leaching was also determined. AAS analysis of the clear filtrates obtained
by filtration after the reaction indicate trace amount of copper ions. This may be rationalized
by considering the fact that copper species were properly fixed on the polymeric support.
This result indicates that the catalyst was very stable and could endure this reaction's
conditions without decomposition or leaching of the active species in the reaction media.
<Fig. 6>
The performances of catalyst 4 and previously reported catalysts were compared in table 4.
Although the methods are effective, the present procedure comparatively affords a truly green
process with high yield of the products in shorter reaction times, and carries out these
reactions in water without exclusion of air.
<Table 4>
Based on these results, we expect that the catalyst 4 will be a suitable alternative to the
existing transition metal catalyst in laboratory and industrial applications.
1
5

RSC Advances
Page 16 of 25
View Article Online
DOI: 10.1039/C6RA05234G
Conclusion
In summary, we have successfully developed a new type of copperꢀmodified porous organic
polymerꢀbased catalyst which combine the catalytic power of transition metal complexes
with the architecture of 3Dꢀnetwork polymer and display particularly high efficiency for the
Huisgen [3+2] cycloaddition. The introduced catalyst can promote the yields and reaction
times over 5 repeated runs with very low leaching amounts of supported catalyst into the
2
reaction mixture. The reaction conditions (H O as solvent, no additive, without exclusion of
air) coupled with the sustainability of the catalyst make the described heterogeneous system
highly desirable from the point of view of green chemistry. We expect that this new and
practical protocol will be useful in academic research and in pharmaceutical development.
Acknowledgments
This work was supported by the Research Council at the University of Shahid Chamran.
References and Notes
1
. (a) J. Dupont, R. F. de Souza and P. A. Z. Suarez, Chem. Rev., 2002, 102, 3667; (b) R. E.
Galian and J. PerezꢀPrieto, Energy Environ. Sci., 2010, 3,1488; (c) A. Corma, Nature, 2009,
61, 182; (d) D. R. MacFarlane and K. R. Seddon, Aust. J. Chem. 2007, 60, 3; (e) P. T.
Anastas, M. M. Kirchhoff, Acc. Chem. Res., 2002, 35, 686.
4
2
3
5
. (a) A. P. Wight and M. E. Davis, Chem. Rev. 2002, 102, 3589.
. (a) P. P. KnopsꢀGerrits, D. E. Devos, F. Thibaultstarzyk, P. A. Jacobs, Nature, 1994, 369,
43; (b) A.ꢀJ. Chen, S.ꢀT. Wong, C.ꢀC. Hwang, C.ꢀY. Mou, ACS Catal. 2011, 1, 786; (c) L.
Wang, X. J. Meng, B. Wang, W. Y. Chi, F.ꢀS. Xiao, Chem. Commun. 2010, 46, 5003; (d) S.
Sahoo, H. Lundberg, M. Eden, N. Ahlsten, W. Wan, X. D. Zou, B. MartinꢀMatute, Chem.
Cat. Chem. 2012, 4, 243; (e) S. Farsadpour, L. T. Ghoochany, S. Shylesh, G. Dorr, A. Seifert,
1
6

Page 17 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
S. Ernst, W. R. Thiel, Chem. Cat. Chem. 2012, 4, 40; (f) L. Wang, H. Wang, P. Hapala, L. F.
Zhu, L. M. Ren, X. J. Meng, J. P. Lewis, F.ꢀS. Xiao, J. Catal. 2011, 281, 30.
4. (a) X. H. Liang, S. M. George, A. W. Weimer, Chem. Mater. 2007, 19, 5388; (b) J. Li, Y.
Zhang, Chem. Mater. 2007, 19, 2581; (c) Y. Zhang, S. Wei, F. Liu, Y. Du, S. Liu, Y. Ji, T.
Yokoi, T. Tatsumi, F.ꢀS. Xiao, Nano Today 2009, 4, 135; (d) Y. Zhang, J. N. Wang, Y. He,
Y. Y. He, B. B. Xu, S. Wei, F.ꢀS. Xiao, Langmuir 2011, 27, 12585.
5
. (a) S. L. Jain, B. S. Rana, B. Singh, A. K. Sinha, A. Bhaumik, M. Nandi and B. Sain,
Green Chem., 2010, 12, 374; (b) S. L. Jain, A. Modak and A. Bhaumik, Green Chem., 2011,
3, 586; (c) S. Wacharasindhu, S. Bardhan, Z.ꢀK. Wan, K. Tabei and T. S. Mansour, J. Am.
1
Chem. Soc., 2009, 131, 4174; (d) Y. X. Liu, W. M. Yan, Y. F. Chen, J. L. Petersen and X. D.
Shi, Org. Lett., 2008, 10, 5389; (e) A. R. Katritzky, S. Bobrov, K. Kostyantyn, Y. Ji and P. J.
Steel, J. Org. Chem., 2003, 68, 5713.
6. (a) Hein, J. E.; Fokin, V. V. Chem. Soc. Rev. 2010, 39, 1302; (b) Medal, M.; Tornøe, C. W.
Chem. Rev. 2008, 108, 2952; (c) Worrell, B. T.; Malik, J. A.; Fokin, V. V. Science 2013, 340,
457.
7. (a) A. Mouradzadegun and S. Dianat, J. Heterocycl. Chem., 2009, 46, 778; (b) A.
Mouradzadegun and F. Abadast, Monatsh. Chem., 2013, 144, 375; (c) A. R. Kiasat, A.
Mouradzadegun, S. Elahi and M. FallahꢀMehrjardi, Chin. Chem. Lett., 2010, 21, 146; (d) A.
Mouradzadegun and F. Abadast, Tetrahedron Lett., 2013, 54, 2641; (e) A. Mouradzadegun
and F. Abadast, Synth. Commun., 2014, 44, 640; (f) A. Mouradzadegun and F. Abadast,
Synlett, 2014, 25, 448.
8
. (a) A. Mouradzadegun, A. R. Kiasat and P. Kazemian Fard, Catal. Commun., 2012, 29, 1;
b) A. Mouradzadegun, S. Elahi, F. Abadast, RSC Adv. 2014, 4, 31239; (c) A.
Mouradzadegun, S. Elahi, F. Abadast, Synthesis, 2015, 47, 630.
(
1
7

RSC Advances
Page 18 of 25
View Article Online
DOI: 10.1039/C6RA05234G
9
. L. M. Tunstad, J. A. Tucker, E. Dalcanale, J. Weiser, J. A. Bryant, J. C. Sherman, R. C.
Helgeson, C. B. Knobler and D. J. Cram, J. Org. Chem., 1989, 54, 1305.
0. W. H. Awad, J. W. Gilman, M. Nydena, R. H. Harris, Jr, T. E. Sutto, J. Callahan, P. C.
Trulove, H. C. DeLong and D. M. Fox, Thermochim. Acta, 2004, 409, 3.
1
11. R. Keller, H. Wycoff, Inorg. Synth., 1946, 2, 1.
12. (a) M. W. McKittrick, C. W. Jones, Chem. Mater. 2003, 15, 1132; (b) K. Parida, K. G.
Mishra, S. K. Dash, Ind. Eng. Chem. Res. 2012, 51, 2235; (c) Y. Zhu, H. Li, Q. Zheng, J. Xu,
X. Li, Langmuir 2012, 28, 7843.
1
1
1
3. S. Magonov, D. Reneker, Rev. Mater. Sci. 1997, 27, 175.
4. S. Dı´ezꢀGonza´lez, Catal. Sci. Technol., 2011, 1, 166.
5. M. Chtchigrovsky, A. Primo, P. Gonzalez, K. Molvinger, M. Robitzer, F. Quignard and
F. Taran, Angew. Chem., 2009, 121, 6030.
1
1
1
6. Y. Wang, J. Liu and C. Xia, Adv. Synth. Catal., 2011, 353, 1534.
7. J. Albadi, M. Keshavarz, F. Shirini and M. Vafaieꢀnezhad, Catal. Commun., 2012, 27, 17.
8. (a) R. B. Nasir Baig and R. S. Varma, Green Chem., 2012, 14, 625; (b) B. Dervauxa and
F. E. Du Prez, Chem. Sci., 2012, 3, 959; (c) A. MegiaꢀFernandez, M. OrtegaꢀMun˜oz, J.
Lopez Jaramillo, F. HernandezꢀMateo and F. Santoyoꢀ Gonzalez, Adv. Synth. Catal., 2010,
3
1
2
2
52, 3306.
9. Y. M. A. Yamada, S. M. Sarkar and Y. Uozumi, J. Am. Chem. Soc., 2012, 134, 9285.
0. X. Xiong and L. Cai, Catal. Sci. Technol., 2013, 3, 1301.
1. C. S. Radatz, L. d. A. Soares, E. f. R. Vieira, D. Alves, D. Russowsky and P. H.
Schneider, New J. Chem., 2014, 38, 1410.
22. F. Alonso, Y. Moglie, G. Radivoy and M. Yus, Adv. Synth. Catal., 2010, 352, 3208.
23. M. Keshavarz, N. Iravani, A. Ghaedi, A. Zarei Ahmady, M. VafaeiꢀNezhad and S. Karimi
Springer Plus 2013, 2, 64.
1
8

Page 19 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
2
H C
HO
OH
HO
OH
HO
HO
OH
OH
HO
4
OH
HO
HO
OH
CH
CH
3
H
3
3
C
C
H2
C
O
C
CH3 H C
H
3
O
4
H
3
C
H
NaOH
HC
H
H
3
CH
3
3
H C
OH
HO
OH
H
2
C
HO
OH
n
1
2
Scheme 1: Synthesis of calix[4]resorcinarene 1 and the 3Dꢀnetwork polymer 2
H N
2
NH
2
HO
H C
OH
2
Si
O
HO
OH
OH
CH
2
O
NH2
Si
HO
OH
OH
CH
3
H
3
C
O
OH
O
H2
C
CH
3
3
H C
H
C
2
Si
CH3 H C
O
3
O
HO
O
CH3 H C
3
HO
CH3
CH3
CH3
OH
HO
OH
Si
H
2
C
O
O
n
H C
OH
2
Si
n
HO
2
H N
2
NH2
3
Scheme 2: Synthesis of amine functionalized polymer 3
Table 1: Optimization of reaction conditions in the preparation of novel amine functionalized polymer 3
Entry
Solvent
water/ethanol
toluene
water/ethanol
water/ethanol
water/ethanol
APTES (mmol)
(wt%) N
2.32
1.03
3.82
4.95
1
2
3
4
5
8
8
15
18
20
4.97
1
9

RSC Advances
Page 20 of 25
View Article Online
DOI: 10.1039/C6RA05234G
(
a)
(
b)
Fig. 1: AFM images (1.0 ꢁm × 1.0 ꢁm) of amine functionalized polymer 3, (a) 2D and (b) 3D height and phase
plots
6
nm
6.45
48.41
nm
55.01
nm
Fig. 2: Image profile (the analysis of the height along a linear path) of amine functionalized polymer 3
2
0

Page 21 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
Fig. 3: SEM image of amine functionalized polymer 3
Fig. 4: TGA profile of amine functionalized polymer 3
2
1

RSC Advances
Page 22 of 25
View Article Online
DOI: 10.1039/C6RA05234G
H N
2
NH2
NH
H
N
NH
HO
OH
Si
O
OH
CH
2
NH
O
OH
Si
Si
HO
O
Si
NH2
OH
Si
O
O
O
OH
O
NH2
O
O
OH
CH3
H C
3
O
H2
C
CuI
DMF
NH
OH
Si
OH
NH
O
OH
O
CH
3
H
3
C
Si
O
HO
O
Si
O
HO
O
OH
O
Si
Si
O
O
O
Si
O
OH
OH
O
2
H C
Si
O
n
HO
OH
H N
2
4
NH2
3
Scheme 3: Synthesis of 3Dꢀnetwork polymerꢀsupported Cu(I) catalyst 4
1000
SiKα
9
8
7
6
5
4
3
2
1
00
00
00
00
00 C Kα
00 N Kα
00
00
O Kα
00
CuLα
CuKα CuKβ
keV
0
0
5
10
Elt Line
Int
Error
K
Kr
W%
A%
66.70
8.78
C
N
Kα 37.3 3.5638 0.5781 0.1990 57.55
Kα 1.3 3.5638 0.0266 0.0092 8.84
O
Si
Cu
Kα 14.0 3.5638 0.1079 0.0372 21.45
Kα 97.0 3.0805 0.2745 0.0945 11.55
18.66
5.72
0.14
Kα
0.5 0.1736 0.0128 0.0044
0.62
1.0000 0.3442 100.00 100.00
Fig. 5: EDS analysis of 3Dꢀnetwork polymerꢀsupported Cu(I) catalyst 4
2
2

Page 23 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
Table 2: Optimization of experimental conditions for the synthesis of 1,2,3ꢀtriazole derivatives in water
Entry Catalyst
Catalyst amount/mmol
Temperature/°C
r.t
Time/min
180
40
Yield%
1
2
3
4
5
6
7
4
4
4
4
4
0.05
0.05
0.05
0.025
0.075
ꢀ
80
86
97
70
82
60
reflux
reflux
reflux
reflux
reflux
5
180
180
180
180
ꢀ
negligible
78
CuI
0.05
Table 3: Conversion of various alkyl/aryl halides 5, sodium azide and Alkynes 6 into the corresponding 1,2,3ꢀ
triazoles 7 in the presence of catalyst 4 in water
N
Catalyst 4 (5 mol%)
N
N
R2
R1X
2
NaN
R C CH
3
R1
H O
2
5
6
7
Entry Substrate (
5)
Substrate (
6
)
Product (
7)
Time/min Yield%
m.p./°C
CH Br
C
C
C
C
CH
CH
CH
CH
N
A
B
C
D
E
2
N
N
5
5
97
94
85
88
80
126ꢀ128
Ph
Ph
CH Cl
N
2
N
N
127ꢀ129
142ꢀ145
95ꢀ97
CH
2
Br
Br
N
N
10
5
N
Ph
N
Br
H
3
C
2
CH Cl
N
Ph
N
3
H C
Cl
C
C
CH
CH
Cl
N
30
116ꢀ117
N
2
CH Br
Ph
N
Cl
Cl
CH
2
Br
O N
2
F
N
5
90
142ꢀ145
N
Ph
N
2
O N
2
3

RSC Advances
Page 24 of 25
View Article Online
DOI: 10.1039/C6RA05234G
97
96
95
95
94
100
100%
8
6
4
2
80
0%
60
0%
0 %4 0
0%
20
0
%
0
1
2
3
4
5
1
2
3
4
5
No. of cycles
Fig. 6: Recyclability of catalyst 4
Table 4: The comparison of catalyst 4 with reported catalysts in the synthesis of triazoles
Catalyst
Time Temperature Yield Ref.
(
h)
(°C)
%
Functionalized chitosan/Cu
Crossꢀlinked polymeric ionic liquid/Cu 48
12
70
r.t.
100
120 MW
55
50
80 MW
70
70
r.t.
99
98
89
99
99
94
96
98
98
87
97
[15]
[16]
[17]
[18]
[19]
[19]
[20]
[21]
[22]
[23]
Present
work
Poly(4ꢀvinyl pyridine)/Cu
Nano ferrite–glutathioneꢀcopper
Poly(NIPAM/Im)/Cu
Poly(NIPAM/Im)/Cu
MNPꢀCuBr
CuNPs/Magsilica
Cu NP/activated carbon
A21/CuI
0.4
0.17
1.5
31
0.3
1
3
8
0.08
4
100
2
4

Page 25 of 25
RSC Advances
View Article Online
DOI: 10.1039/C6RA05234G
Graphical Abstract
Copper-loaded Hypercrosslinked Polymer Decorated with
Pendant Amine Groups: A Green and Retrievable Catalytic
System for Quick [3+2] Huisgen Cycloaddition in Water
Arash Mouradzadegun*, Mahsa Mostafavi
Department of Chemistry, Faculty of Science, Shahid Chamran University, Ahvaz, Iran
*
Corresponding author: Fax +98(61)33337009; Tel +98(61)33331042
E-mail: arash_m@scu.ac.ir
Cu
NH
H
N
NH
Cu
NH
OH
Si
HO
O
Si
OH
O
O
NH
2
NH
2
Si
O
O
O
OH
Cu
NH
OH
Cu
Si
OH
OH
NH
O
O
Si
O
O
O
Si
O
HO
O
Si
Cu
O
Si
O
OH
Cu
OH
O
O
1
R X
N
N
R2
NaN3
H O
2
N
R1
2
R C CH