CuSO4 nanoparticles loaded onto poly (toluenesulfonic acid-formaldehyde)/polyethyleneimine composites: An efficient retrievable catalyst for A3/decarboxylative A3 reactions

Article abstract of DOI:10.1002/aoc.6167

Using polymeric composite incorporated transition metal nanoparticles to promote various organic reactions has been found as one of the most powerful strategies in organic synthesis. In this paper, CuSO₄ nanoparticles (CuSO₄ NPs) anc

Full text of DOI:10.1002/aoc.6167

Received: 9 June 2020
DOI: 10.1002/aoc.6167
Revised: 1 January 2021
Accepted: 3 January 2021
F U L L P A P E R
CuSO4 nanoparticles loaded onto poly (toluenesulfonic acid-
formaldehyde)/polyethyleneimine composites: An efficient
retrievable catalyst for A3/decarboxylative A3 reactions
Wei Jiang1 | Jinxi Xu1 | Wei Sun1 | Yiqun Li1,2
1Department of Chemistry, Jinan
Using polymeric composite incorporated transition metal nanoparticles to pro-
mote various organic reactions has been found as one of the most powerful
strategies in organic synthesis. In this paper, CuSO4 nanoparticles (CuSO4
NPs) anchored on the surface of polymeric composites comprising of water-
insoluble acidic poly (toluenesulfonic acid-formaldehyde) (PTSAF) and
water-soluble basic polyethyleneimine (PEI) to form the desired PEI/PTSAF-
supported CuSO4 NPs catalyst (CuSO4NPs@PEI/PTSAF) have been fabricated.
Characterization of the as-synthesized catalyst by inductively coupled plasma
(ICP), Fourier transform infrared (FTIR), X-Ray diffraction (XRD), scanning
electron microscopy (SEM), energy-dispersive spectroscopy (EDX) and elemen-
tal mapping analysis, transmission electron microscopy (TEM), and therm-
ogravity analysis (TGA) demonstrated successful immobilization of the CuSO4
NPs on the PEI/PTSAF composite. This novel catalyst was highly active in the
one-pot A3 and decarboxylative A3 coupling reactions toward generating
corresponding propargylamines in good to excellent yields under solvent-free
reaction. The nature of the well distribution of CuSO4 NPs coordinated with
PEI ligand in the CuSO4NPs@PEI/PTSAF composite leads to superior catalytic
activity. The present methodology offers several advantages such as high cata-
lytic activity, good to excellent yields, short reaction times, simple operations,
compatibility of broad scope of substrates, and environmental friendliness.
More importantly, the catalyst can be easily recovered from the reaction mix-
ture by a simple filtration and still exhibits remarkable reusability with only
marginal loss of its performance after five consecutive runs.
University, Guangzhou, 510632, China
2CAS Key Laboratory of Synthetic
Chemistry of Natural Substances,
Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai,
200032, China
Correspondence
Yiqun Li, Department of Chemistry, Jinan
University, Guangzhou 510632, China.
Email: tlyq@jnu.edu.cn
Funding information
Natural Science Foundation of
Guangdong Province, Grant/Award
Number: 2020A1515010399
K E Y W O R D S
A3 reaction, copper sulfate nanoparticles, decarboxylative A3 reaction, poly (toluenesulfonic
acid-formaldehyde), polyethyleneimine
Wei Jiang and Jinxi Xu contributed equally to this work.
Appl Organomet Chem. 2021;35:e6167.
wileyonlinelibrary.com/journal/aoc
© 2021 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.6167

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JIANG ET AL.
1 | INTRODUCTION
comparing with their catalyst parent. Moreover, multi-
step synthetic approaches are necessary to achieve the
ligand-functionalized support materials and significant
structural perturbations to the parent metal catalyst are
generally unavoidable in such circumstances. For the
reason of practicality, simple and efficient alternative
strategies that surmounted these obstacles for the
immobilization of metal catalyst are therefore highly
desirable. More recently, metal catalysts immobilized on
ligand tethered to the support material via ionic bond
have emerged as an attractive alternative with their
powers being well-demonstrated in catalysis since com-
plicated functionalization of the solid matrix is generally
minimized. Moreover, the ionic bonding strategy is also
quite facile, thus allowing fine tuning of the structure
of support material, coordination of ligand, catalytic
activity of catalyst parent, and their combination.[33,34]
Taking advantage of the ionic bonding principle, the
solid acid/base interaction strategy has been proven to
be one of the most efficient ionic bonding approaches
for anchoring catalysts onto solid supports with excel-
lent catalytic activity and reusability. To obtain uniform
and homogenous dispersion of metal salt nanoparticles,
many efforts have been made to develop base as a
ligand utilized in designing of novel catalyst.
In recent years, introduction of polyethyleneimine
(PEI) onto acidic solid materials has overwhelmingly
impact on organometallic chemistry due to their unique
properties. PEI is an amorphous, water-miscible
branched polymer with repeating units of primary, sec-
ondary, and tertiary amine moieties.[35,36] The PEI plays
as a strong donor of electron pair and thus effectively
enhances the electron density at the center of transit
metal and thus accelerate the catalysis. Poly
(toluenesulfonic acid-formaldehyde) (PTSAF) is a novel
water-immiscible strong acidic resin synthesized by the
copolymerization of p-toluenesulfonic acid and parafor-
maldehyde in the presence of catalytic amount of sulfuric
acid.[37] PTSAF is an inexpensive polymer possessing
comparable acidity and cation exchange property. Thus,
PEI can conveniently interact with PTSAF via a very
strong ionic bonding interaction between acidic sulfonic
groups and basic amino groups. Based on these proper-
ties of PEI and PTSAF, tethering of PEI ligands onto
PTSAF material via ionic bond is particularly well suited
for hosting metal salt nanoparticles for the following rea-
sons: (1) the basic PEI can facilitate strong acid/base
interaction with acidic PTSAF, (2) water-insoluble
PTSAF serves as the vertebration, and water-soluble N-
rich PEI providing the lone pair electrons as coordinating
sites for chelation of transition metal species as the
ligand, and (3) the catalytic transition metal species are
coordinated by branched PEI chain and therefore fine
Recently, great effort has been made to the transition
metal-catalyzed one-pot multicomponent reaction of
aldehyde, amine, and alkyne (commonly named A3 reac-
tion) as well as aldehyde/phenylglyoxylic acid, amine,
and phenylpropiolic acid (i.e., decarboxylative A3 reac-
tion) due to the main product propargylamine that is the
key and versatile intermediate in the synthesis of many
biologically active nitrogen-containing compounds.[1]
Therefore, it is necessary to explore an efficient homoge-
neous and heterogeneous catalysis to promote these
three-component couplings. Despite of high activity of
homogenous catalysis, some disadvantages such as mois-
ture sensitivity, tedious isolation, and reuse of metal cata-
lysts which severely contaminate the final product are
frequently difficultly addressed. Moreover, aggregation
and precipitation of the metal catalyst occur at times,
which make the catalyst tend to lose its activity,[2,3] while
heterogeneous catalysis has salient features such as easy
recovery
and
good
recyclability.
Therefore,
heterogenization of homogenous catalyst on a suitable
carrier is a more efficient way to tackle these obstacles of
homogeneous catalysis which makes it practical for the
synthesis of diversely molecules with pharmaceutical and
biochemical applications in laboratorial and industrial
scales.[4–10] In order to achieve this purpose, heteroge-
neous catalysis has drawn much more focus. Among the
heterogeneous catalysts, because copper catalysts are low
cost, readily available, and high active, some hetero-
genized copper salts and its complexes were successfully
used to catalyze A3 and decarboxylative A3 couplings.
These reported heterogeneous copper catalysts include
CuII@PAA/PVC mesoporous fibers,[11] polymer beads
decorated with dendrimer supported Cu (II),[12]
malachite,[13] Cu0NPs@CMC,[14] Fe3O4@SiO2-Se-T/
CuI,[15] fiber-polyquaterniums@Cu(I),[16] PS-PEG-BPy-
Cu0@HAP@γ-Fe2O3,
chit@copper,[19]
(II) amine-imine
[17]
[18]
CuBr2,
polymer-supported
copper
complexes,[20]
Cu-MOF-74,[21]
Cu
(II)-
hydromagnesite,[22] CMC-CuII,[23] Cu@PMO-IL,[24] GO-
CuCl2,
Cu0-Mont,[26] CuSBA-15,[27] Cu/Al/oxide
[25]
mesoporous sponges,[28] Cu-MOFs,[29] Cu (OH) x–
Fe3O4,[30] copper thin films, and [31] CuO NPs,[32]
.
Generally, heterogenization is frequently achieved
by immobilization of metal catalyst on both solid inor-
ganic materials (SiO2, Fe3O4, NaY, graphene, and car-
bon nanotube) and organic materials (polystyrene,
polyethylene, PEG, etc.)[4–6] which covalently tether the
ligand. Although excellent catalytic performance has
been achieved in some cases, most of ligand-
functionalized heterogenous catalysts demonstrated
decreased catalytic performance and selectivity

JIANG ET AL.
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tuning their performance and preventing them leaching
out from the support into solvent.
2.2 | Preparation of CuSO4NPs@PEI/
PTSAF catalyst
Although many works on A3 and decarboxylative A3
coupling reactions have been reported, as far as we
observed, there have not reports using this PTSAF/PEI
acid/base composite to immobilize the nanoparticles of
transition metal salts and their catalytic application in A3
and decarboxylative A3 reactions. We envisage that the
heterogenization of transition metal salts on this type of
composite by combination of “two worlds” of distinct
acidic and basic polymers is a powerful strategy to accel-
erate organic reactions efficiently in one-pot catalysis.
Herein, we have developed an efficient protocol for inte-
gration of acidic PTSAF as a support and basic PEI as a
ligand to support CuSO4NPs for the fabrication of a
highly active catalyst for A3 and decarboxylative A3
reaction (Figure 1).
Initially, the mixture of p-toluenesulfonic acid (10 g),
paraformaldehyde (2 g), and sulfuric acid (0.2 g) was
heated at 110ꢀC with constant stirring for 48 h to form
black solid. The resulted black solid (named PTSAF) was
filtered and washed thoroughly with deionized water
until the filtrate reached neutral. Subsequently, the
obtained PTSAF was dried at 120ꢀC in an oven overnight.
Next, the grinded PTSAF powders were soaked in 20 ml
of 50% PEI solution at room temperature for 48 h and
then filtered and washed with a plenty of deionized water
in order to remove excess PEI from the PTSAF surface.
Furthermore, the as-prepared PEI/PTSAF composite
material was immersed into 200 ml 0.1 mol/L sodium
carbonate solution for 12 h. After that, the treated
PEI/PTSAF materials were washed thoroughly with
deionized water and ethanol then dried at 60ꢀC till a con-
stant weight. Finally, PEI/PTSAF black power (1 g) was
soaked in the already-prepared 100 ml 2% CuSO4 solution
and gently agitated at room temperature for 24 h. The
obtained CuSO4NPs@PEI/PTSAF catalyst was filtered
out and washed repeatedly with deionized water and
then dried at 40ꢀC to constant weight. The Cu content in
catalyst determined by ICP is 0.6575 mmol/g.
2 | EXPERIMENTAL
2.1 | General considerations
All chemicals and solvents were analytical grade and used
as received. Scanning electron microscopy (SEM) and
energy-dispersive spectroscopy (EDX) were conducted
with a Zeiss Sigma 500 instrument. X-ray photoelectron
spectroscopy (XPS) was carried out on a Thermo Fisher
Scientific K-Alpha instrument. X-Ray diffraction (XRD)
was performed on a Bruker D8. Thermogravimetric analy-
sis (TGA) was performed on a Netzsch STA449 under a
2.3 | General procedure for the A3 and
decarboxylative A3 reactions
nitrogen atmosphere from 30ꢀC to 800ꢀC in
a
Aldehyde/phenylglyoxylic acid (1.0 mmol), amine
(1.2 mmol), terminal alkyne/phenylpropiolic acid
(1.5 mmol), and catalytic amount of CuSO4NPs@PEI/
PTSAF (1.5 mol% Cu) were charged into a sealed vessel.
The mixture was stirred at 100ꢀC for specific time indi-
cated by thin-layer chromatography (TLC) to the end of
reaction. The CuSO4NPs@PEI/PTSAF was filtered and
washed with enough AcOEt (15 ml × 3), and the organic
phase was combined and washed with brine (5 ml × 3)
and dried over anhydrous Na2SO4. Then the solvent was
evaporated in vacuum, and the residue was purified by
preparative thin-layer chromatography (PTLC) to afford
the corresponding propargylamine.
50 ml min−1 N2 flow and a ramp rate of 10ꢀC min−1. The
elemental copper content of the catalyst was determined
by inductively coupled plasma atomic emission spectrom-
etry (ICP-AES) using X Series 2 instrument. Gas
chromatography (GC) was performed on a Shimadzu
GCMS-QP2020. Fourier transform infrared spectra (FTIR)
were collected on a Nicolet 6700 spectrophotometer in
KBr pellet within the spectral range of 4,000–400 cm−1 at
1
2 cm−1 resolution and 32 scans. H NMR and 13C NMR
spectra were recorded on a Bruker-300 Avance Spectrome-
ter with CDCl3 as solvent using TMS as an internal stan-
dard at 300 and 75 MHz, respectively.
FIGURE 1 CuSO4NPs@PEI/PTSAF-catalyzed the
A3 and decarboxylative A3 for the synthesis of
propargylamines

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JIANG ET AL.
3 | RESULTS AND DISCUSSION
characteristic N–H.[36,38,39] When CuSO4 immobilized on
PTSAF, the electron cloud density of the nitrogen atoms
on PEI of the PEI/PTSAF decreases, and the N–H absorp-
tion peaks move to lower wave number from 1,454 to
1,443 cm−1 (curve b), respectively.
3.1 | Preparation and characterization of
catalyst
Firstly, we adopted a facile method to prepare an insolu-
ble acidic PTSAF by copolymerization of toluenesulfonic
acid and formaldehyde according to previous reported
procedures.[37] Subsequently, the water-soluble basic PEI
was grafted onto PTSAF matrix via ionic bond by acid/
base reaction. Finally, CuSO4NPs@PEI/PTSAF catalysts
were synthesized by the treatment of CuSO4 solution
with PEI/PTSAF composite materials. The synthetic
routes have been outlined in Scheme 1.
The obtained CuSO4NPs@PEI/PTSAF catalyst was
fully characterized with various analysis techniques such
as inductively coupled plasma (ICP), FTIR spectroscopy,
XRD, SEM, energy dispersive X-ray (EDX) mapping anal-
ysis, transmission electron microscopy (TEM), and
thermogravity analysis (TGA).
The FTIR spectra of PEI/PTSAF and CuS-
O4NPs@PEI/PTSAF are shown in Figure 2. As shown in
Figure 2, the stretching peak at 3,427 cm−1 together with
bending peak at 1,454 cm−1 (curve a) is attributed to
FIGURE 2 Fourier transform infrared (FTIR) spectra of
polyethyleneimine (PEI)/poly (toluenesulfonic acid-formaldehyde)
(PTSAF) (a) and CuSO4NPs@PEI/PTSAF (b)
SCHEME 1 Schematic process for preparation of CuSO4NPs@PEI/PTSAF catalyst

JIANG ET AL.
5 of 16
The XRD patterns of PTSAF (curve a), PTSAF/PEI
the catalyst facilitates better mass transfer and enlarges
its interaction area with reaction substrates.
(curve b), CuSO4NPs@PEI/PTSAF (curve c), and CuS-
O4Á5H2O (curve d) are shown in Figure 3. One broad
peak (2θ = 19ꢀ) is present in PTSAF, PTSAF/PEI, and
CuSO4NPs@PEI/PTSAF, respectively. By comparison
with CuSO4Á5H2O (curve d), no diffraction peaks of CuS-
O4Á5H2O were found in these samples. This fact may be
due to the very small size and nanocrystalline nature of
the CuSO4 with lower weight percentage or high disper-
sion in amorphous nanoform in catalyst structure.
The XPS was used to confirm the oxidation state of
elements presented in the as-synthesized catalyst. The
full spectra and fitting curves of high-resolution spectra
are presented in Figure 4. The survey profiles for Cu2p,
S2p, O1s, N1s, and C1s of the CuSO4NPs@PEI/PTSAF are
plotted in Figure 4(a). The Cu2p peak shown in Figure 4
(b) shows four components at 962.5, 953.4, 942.7, and
The SEM images and corresponding elemental maps
for the prepared CuSO4NPs@PEI/PTSAF catalyst are
presented in Figure 6. These images clearly showed that
the C, O, N, S, and Cu elements were finely dispersed
throughout the catalyst in a homogeneous manner. These
results demonstrated that CuSO4 was immobilized on the
PEI/PTSAF surface.
The EDX analysis provides local elemental informa-
tion for the catalyst. The EDX of the CuSO4NPs@PEI/
PTSAF associated with SEM analysis is shown in
Figure 7. The EDX indicated that the obtained catalyst
was composed of nonmetallic elements N, O, and S, and
metallic element Cu. The observation of Cu and S ele-
ment in EDX analysis proved the successful introduction
of CuSO4 on PEI/PTSAF surface.
933.7 eV which can be attributed to Cu (II) in
In order to have an insight into the morphology of
the catalyst, the TEM images of CuSO4NPs@PEI/PTSAF
were recorded varied from 10 nm to 1 μm (Figure 8),
showing the formation of quasi-spherical nanoparticles
(Figure 8(a)). The particle size histogram (Figure 8(f))
shows that the average particle size of CuSO4 located in
the catalyst is approximately 1.21 nm in diameter,
respectively.
The TGA was conducted in nitrogen atmosphere
varying from 25ꢀC to 800ꢀC. As can be seen from the plot
in Figure 9, there are two-step thermal decomposition.
The incipient weight loss laid in the range of 25ꢀC to
100ꢀC was attributed to the removal of loosely physically
adsorbed water. Then the main weight loss in the range
of 275ꢀC to 500ꢀC is assigned to the decomposition of PEI
and PTSAF. In addition, the plot presented higher ash
content, which attributed to the copper residue. The TGA
results indicated that CuSO4NPs@PEI/PTSAF is suffi-
ciently stable from room temperature to 250ꢀC and thus
can be performed under our thermal conditions.
[40,41]
CuSO4.
The sulfur peaks shown in Figure 4
(c) contain two components at 169.2 and 167.8 eV which
match the reported values of the binding energies of sul-
[42,43]
fur from CuSO4 and CuSO3,
respectively. The peaks
at 286.6 and 284.9 eV in Figure 4(d) were assigned to the
C–N and C–C bonds in PEI. The binding energies at
401.8 and 399.8 eV in Figure 4(e) were attributed to the
+
N–H bond in –NH3 and –NH2 groups of PEI, corre-
spondingly. These results suggest that CuSO4 were suc-
cessfully loaded on the PEI/PTSAF surface.
The SEM images of CuSO4NPs@PEI/PTSAF shown
in Figure 5 were recorded at low (2 μm) and high magni-
fications (100 nm) for easy clarity and comparison. The
rough surface can be observed for CuSO4NPs@PEI/
PTSAF catalyst in Figure 5(a)–5(d). The rough surface of
3.2 | Performance of catalyst for the A3
and decarboxylative A3 reactions
To evaluate the catalytic activity of CuSO4NPs@PEI/
PTSAF, the reaction of benzaldehyde (1a), morpholine
(2a), and phenylacetylene (3a) was chosen as a model.
The reaction temperatures, various solvents, and different
loading of catalyst were symmetrically investigated. The
results are listed in Table 1. In order to establish the
CuSO4 NPs in the catalyst plays the key role in the reac-
tion, the model reaction was performed at 100ꢀC in the
absence of catalyst, and in the presence of 1.5 mol% of
PTSAF, PEI, PEI/PTSAF, CuII@PTSAF, PEI-CuSO4 and
CuSO4NPs@PEI/PTSAF under solvent-free condition,
FIGURE 3 X-Ray diffraction (XRD) of PTSAF (a), PEI/PTSAF
(b), CuSO4NPs@PEI/PTSAF (c), and CuSO4Á5H2O (d)

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JIANG ET AL.
FIGURE 4 The X-ray photoelectron spectroscopy (XPS) and spectra scan of element survey (a), Cu2p (b), S2p (c), C1s (d), and N1s (e)
FIGURE 5 The scanning electron microscopy (SEM) imagines of CuSO4NPs@PEI/PTSAF (a in 100 nm, b in 200 nm, c in 500 nm, and
d in 2um)

JIANG ET AL.
7 of 16
FIGURE 6 The scanning electron microscopy (SEM) mapping imagines of CuSO4NPs@PEI/PTSAF show the presence of C, N, O, S, Cu
element in the catalyst
FIGURE 7 Energy-dispersive spectroscopy
(EDX) element analysis of CuSO4NPs@PEI/
PTSAF
the product yields ranged from 0% and up to 90%
(Table 1, entries 2–8). Further increasing the dose of cata-
lyst from 1.5 to 2 even up to 3 mol%, no significant eleva-
tion in the reaction yield was observed (Table 1, entries
9–10). On the other hand, decreasing the amount of cata-
lyst reduced the yield of the product (Table 1, entries
11–13). These results suggested that the catalyst is
essential for this A3 model reaction and the catalytically
active species is Cu (II), and 1.5 mol % of Cu is the opti-
mal amount for the model reaction. Then the tempera-
ture effect on the model was investigated. Increasing the
temperature from 100ꢀC to 120ꢀC has no apparent impact
on the product yields (Table 1, entries 14–15). On the
contrary, decreasing the reaction temperature from

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JIANG ET AL.
FIGURE 8 The transmission electron microscopy (TEM) imagines of CuSO4NPs@PEI/PTSAF (a in 10 nm, b in 20 nm, c in 100 nm, d in
200 nm, and e in 1 μm) and the diameter analysis of CuSO4NPs (f) calculation based on image (b)
EtOH, CH3CN, DMF, and DMSO (Table 1, entries 1 and
19–24). Gratifyingly, the highest yields were obtained
when the reaction was conducted under the neat condi-
tion and in toluene. From the viewpoint of green chemis-
try, we will conduct the A3 and decarboxylative A3
reactions in the succeeding work under the solvent-free
condition.
With the optimal condition in hand, the scope of the
reactions using various carbonyl compounds/phe-
nylglyoxylic acids, amines, and alkynes/phenylpropiolic
acids was explored, and the results are summarized in
Table 2. In the cases of A3 coupling, aryl aldehydes with
electron-withdrawing or electron-donating substituents
afforded moderate to excellent yields when it reacted
with morpholine and phenylacetylene (Table 2, entries
FIGURE 9 The thermogravity analysis (TGA) curves of
1–9). The heterocyclic 2-thiophene formaldehyde with
morpholine and phenylacetylene also underwent effi-
CuSO4NPs@PEI/PTSAF
ciently and afford the corresponding product in excellent
yield (Table 2, entry 10). Interestingly, the reaction
100ꢀC to room temperature had considerable negative
influence on the model reaction (Table 1, entries 16–18).
The effect of the solvent was also examined. The model
reaction was carried out under solvent-free condition as
well as in the different solvents such as toluene, THF,
between aliphatic aldehyde and morpholine with
phenylacetylene formed the desired product in good
yields due to their higher reactivity (Table 2, entry 11).
Notably, the phenylacetylene bearing either electron-
donating or electron-withdrawing groups on the aromatic

JIANG ET AL.
9 of 16
TABLE 1 Optimization of reaction conditions
Entry
1
Solvent
Temp. (ꢀC)
100
100
100
100
100
100
100
100
100
100
100
100
100
110
120
80
Catalyst (mol%)
Time (h)
Yielda (%)
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Solvent-free
Toluene
none
4
N.P.b
N.P.
N.P.
N.P.
66
2
PTSAF/PEI (1.5)
4
3
PEI (1.5)
4
4
PTSAF (1.5)
4
5
CuSO4Á5H2O (1.5)
8
6
CuII@PTSAF (1.5)
4
56
7
PEI-CuSO4 (1.5)
6
22
8
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (2.0)
CuSO4NPs@PEI/PTSAF (3.0)
CuSO4NPs@PEI/PTSAF (1.2)
CuSO4NPs@PEI/PTSAF (0.8)
CuSO4NPs@PEI/PTSAF (0.4)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
CuSO4NPs@PEI/PTSAF (1.5)
4
92
9
4
93
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
4
96
4
86
4
84
4
73
4
91
12
12
12
12
12
12
12
12
12
12
96
17
60
Trace
N.P.
92
r.t.
120
80
THF
46
C2H5OH
80
27
CH3CN
80
27
DMF
120
120
44
DMSO
62
Note: Reaction conditions: benzaldehyde (1.0 mmol), morpholine (1.2 mmol), phenylacetylene (1.5 mmol)), catalytic amount of catalyst in a sealed vial.
aIsolated yields.
bN.P. refers to no product.
ring are readily coupled with carbonyl compounds and
amines in moderate to excellent yields (Table 2, entries
14–16 and 20–21). Various amines also proceeded
smoothly in A3 coupling reaction and generated the
corresponding products in good to excellent yields.
Among the amines, alicyclic amine such as morpholine
gave good yields of corresponding products, whereas
moderate yields were observed as acyclic dialkylamines
were used (Table 2, entries 17–18). These successful
results encouraged us to extend the present catalytic
approach to a wide variety of substrates. Then we
turned our attention toward decarboxylative A3 reac-
tion. We further expanded the substrates to phe-
nylglyoxylic
phenylpropiolic acid as a phenylacetylene surrogate.
The substrate of phenylglyoxylic acids and
acids
as
aldehyde
sources
and

10 of 16
JIANG ET AL.
TABLE 2 CuSO4NPs@PEI/PTSAF-catalyzed synthesizing of propargylamines through A3 reaction
Entry
Aldehyde
Amine
Alkyne
Time (h)
Product
4a
Yielda (%)
1
6
96
2
3
4
5
6
7
6
6
6
6
6
6
4b
4c
4d
4e
4f
87
97
85
94
62
80
4g
(Continues)

JIANG ET AL.
11 of 16
TABLE 2 (Continued)
Entry
Aldehyde
Amine
Alkyne
Time (h)
Product
4h
Yielda (%)
8
6
92
83
85
99
99
85
84
9
6
6
4
4
4
4
4i
4j
10
11
12
13
14
4k
4l
4m
4n
(Continues)

12 of 16
JIANG ET AL.
TABLE 2 (Continued)
Entry
Aldehyde
Amine
Alkyne
Time (h)
Product
4o
Yielda (%)
15
4
80
16
4
4p
83
17
18
19
4
4
4q
4r
4a
92
86
68
12
20
21
12
12
4l
74
72
4n
(Continues)

JIANG ET AL.
13 of 16
TABLE 2 (Continued)
Entry
Aldehyde
Amine
Alkyne
Time (h)
Product
4a
Yielda (%)
22
12
60
63
80
23
24
12
12
4b
4f
Note: Reaction conditions: aldehyde/phenylglyoxylic acid (1.0 mmol), amine (1.2 mmol), alkyne/phenylpropiolic acid (1.5 mmol), CuSO4NPs@PEI/PTSAF
(1.5 mol %), solvent-free, 4–12 h, 100ꢀC.
aIsolated yields.
phenylpropiolic acid reacted well under the optimal
condition to afford the corresponding products in excel-
lent yields (Table 2, entries 19–24).
3.3 | Recycling of catalyst for the A3
model reaction
In order to clarify the reusabilities of CuSO4NPs@PEI/
PTSAF catalyst in A3 couplings, the model reaction of p-
chlorobenzaldehyde, morpholine, and phenylacetylene
was evaluated under the optimal reaction condition.
Upon the completion of the reaction, the CuS-
O4NPs@PEI/PTSAF catalyst was recollected conve-
niently by filtration and reused directly in the subsequent
run without any further treatment. The results as shown
in Figure 10 indicated that the CuSO4NPs@PEI/PTSAF
FIGURE 10 Recycling of catalyst in the A3 model reaction

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JIANG ET AL.
FIGURE 11 The transmission electron microscopy (TEM) images of the used catalyst at different magnification (a–d), the X-ray
photoelectron spectroscopy (XPS) of the used catalyst (e), the diameter analysis of used catalyst based on image b (f), the X-Ray diffraction
(XRD) pattern of the used catalyst (g), and Fourier transform infrared (FTIR) of used catalyst (h)
catalyst can be used for at least five consecutive runs suc-
cessfully with slight decreasing its catalytic performance.
Furthermore, the XPS, TEM, XRD, and FTIR
(Figure 11) of the recovered catalyst after five runs show
that the morphology, chemical, and oxidation state of the
catalyst have no significant changes and the particle sizes
slightly increased from 1.21 to 3.04 nm in diameter.
These findings indicated that the catalyst was intact after
multiple reusages. These findings not only explained the
excellent recycle results but also furtherly confirmed the
excellent stability of this composite catalyst.
3.4 | Comparison with other reported
copper catalysts
Finally, to demonstrate the worthiness and efficiency of
the CuSO4NPs@PEI/PTSAF catalyst in the synthesis of
propargylamine derivatives, it has been compared with
other previously published copper catalysts using the A3
model reaction. The comparative results presented in
Table 3 clearly demonstrate that the present catalyst
indeed has superior catalytic performance in terms of low
catalyst loading, short reaction time, and excellent yield.

JIANG ET AL.
15 of 16
TABLE 3 Comparison of the present catalyst with previous reported copper catalysts in A3 model reaction
Entry
Catalyst (dose)
Reaction conditions
Yield (%)
Ref
[12]
1
polymer beads decorated with dendrimer supported Cu
(II) (1 mol%)
1,4-dioxane, 90ꢀC, 9 h
87
[14]
[16]
[19]
[20]
2
3
4
5
Cu0NPs@CMC (7.5 mol%)
fiber-polyquaterniums@Cu(I) (2 mol%)
chit@CuI (1.1 mol%)
Neat, 120ꢀC, 12 h
80
94
83
91
Toluene, 100ꢀC, 6 h
Neat, 140ꢀC, under N2, 0.75 h
1,4-dioxane, 80ꢀC, 24 h
polymer-supported copper (II) mine-imine complexes
(1 mol%)
[23]
[28]
[32]
6
7
8
9
CMC-CuII (5 mol%)
Neat, 120ꢀC, 15 h
Toluene, 100ꢀC, 22 h
Toluene, 90ꢀC, 7 h
Neat, 100ꢀC, 6 h
81
94
80
96
Cu/Al/oxide mesoporous sponges (12 mol%)
CuO NPs (8 mol%)
CuSO4NPs@PEI/PTSAF
This work
In addition, solvent-free condition and easy separation
and recycling of catalyst are some obvious benefits with
respect to the other methods.
CONFLICT OF INTEREST
The authors declare no competing financial interest.
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How to cite this article: Jiang W, Xu J, Sun W,
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https://doi.org/10.1002/aoc.6167
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