Preparation and characterization of copper/polysulfonamide complex immobilized on geraphene oxide as a novel catalyst for the synthesis of pyrimido[1,2-a]benzimidazoles

Article abstract of DOI:10.1002/aoc.5918

Copper–polysulfonamide complex immobilized on geraphene oxide as a novel heterogeneous catalyst (GO@PSA-Cu) was synthesized and the structure and morphology of catalyst were characterized with various analytical techniques such as Fourier-transform infrar

Full text of DOI:10.1002/aoc.5918

Received: 21 April 2020
DOI: 10.1002/aoc.5918
Revised: 12 June 2020
Accepted: 14 June 2020
F U L L P A P E R
Preparation and characterization of
copper/polysulfonamide complex immobilized on
geraphene oxide as a novel catalyst for the synthesis of
pyrimido[1,2-a]benzimidazoles
Nayereh Shekarlab | Ramin Ghorbani-Vaghei
| Sedigheh Alavinia
Department of Organic Chemistry,
Copper–polysulfonamide complex immobilized on geraphene oxide as a novel
heterogeneous catalyst (GO@PSA-Cu) was synthesized and the structure and
morphology of catalyst were characterized with various analytical techniques
such as Fourier-transform infrared spectroscopy, scanning electron micros-
copy, energy-dispersive X-ray, N2 isotherms, elemental mapping, inductively
coupled plasma–MS, and thermogravimetric analysis. The GO@PSA-Cu cata-
lyst demonstrated good to excellent yields for the synthesis new derivatives
of pyrimido[1,2-a]benzimidazoles via one-pot three-component condensation
reaction of various aromatic aldehydes, 2-aminobenzimidazole, and ethyl
acetoacetate in ethanol. The method presented herein has several prominent
advantages such as cost-effectiveness, operational simplicity, short reaction times,
high yields, and reusability of the catalyst even after six consecutive runs.
Faculty of Chemistry, Bu-Ali Sina
University, Hamedan, 6517838683, Iran
Correspondence
Ramin Ghorbani-Vaghei, Department of
Organic Chemistry, Faculty of Chemistry,
Bu-Ali Sina University, Hamedan
6517838683, Iran.
Email: rgvaghei@yahoo.com
K E Y W O R D S
copper, geraphene oxide, heterogeneous, pyrimido[1,2-a]benzimidazoles, sulfonamide
1 | INTRODUCTION
molecular-level dispersions. It is worth noting that
separation, purification, and reusability of homogeneous
Multiple component reactions (MCRs) can synthesize
complex molecules in one pot with good atom economy,
high selectivity, high yields, and providing a quick access
to new organic molecules. MCRs offer remarkable advan-
tages such as convergence; operational simplicity; and
reduction in the number of workups, extraction and puri-
fication processes. In this sense, the synthesis of the com-
pounds can be achieved with less waste, time, and cost
without the isolation of intermediates. Recently, studies
on MCRs have emphasized their significant applications
in organic and medicinal chemistry. In MCRs, the
required activation energy will be altered by the cata-
lyst.[1,2] In this sense, it is worth mentioning that homo-
geneous catalysts show greater catalytic activity in
comparison to the heterogeneous catalysts due to their
catalysts have been considered as time-consuming pro-
cesses.[3] However, when considering heterogeneous cat-
alysts, one can point to their easy separation and
consecutive reusability, which are economical. Undesir-
ably, the applicability of heterogeneous catalysts is hin-
dered by the lack of catalytic activity and selectivity
toward desired products.[4] In this regard, low cost, high
catalytic activity, high stability, easy recovery, and excel-
lent reusability are the most fundamental features for
designing new catalysts. Accordingly, it is very significant
to design a new catalyst with excellent catalytic activity—
just like that of the homogeneous catalysts—and also
with easy recyclability—like the heterogeneous ones.
During recent years, researchers have paid significant
attention to the novel fabricated composite structures
Appl Organomet Chem. 2020;e5918.
wileyonlinelibrary.com/journal/aoc
© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5918

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SHEKARLAB ET AL.
which apply geraphene oxide (GO) and polymers. In this
sense, GO supports as compared with other supports can
be regarded as excellent candidates to design catalysts.
The most significant advantages of the GO are as follows:
they possess many active sites and pores; have high sta-
bility with good selectivity; contain abundant oxygen
functional groups; and also, they are reusable, economic,
and ecofriendly.
Researchers have paid great attention to the GO
which can be applied to immobilize polymers.[5]
Ligands having sulfonamide groups are excellent in
the stabilization of metal species.[6] In this work,
our goal has been to synthesize a novel geraphene
oxide@polysulfonamide composite as a substrate for
the stabilization of copper (GO@PSA-Cu). The van der
Waals interaction between Cu and GO@PSA is very
important in the stabilization of Cu species. The devel-
opment of organic–inorganic nanocomposite with high
loading and a good surface area can provide interest-
ing applications as catalyst for the synthesis of hetero-
cyclic compounds.
aldehydes, and 2-amino-1H-benzimidazole is a well-
known technique for the preparation of pyrimido[1,2-a]
benzimidazoles. These methods employed diverse
catalysts such as silica-supported sulfuric acid,[8]
poly(vinylpyrrolidonium)perchlorate,[9] L-proline,[10] mag-
nesium oxide,[11] and N,N,N0,N0-tetrabromobenzene-
1,3-disulfonamide (TBBDA).[12] Many of the recent
reported protocols have interesting merits, but some suffer
from one or more disadvantages such as harsh reaction
conditions, tedious workup procedures, long reaction
times, and emission of hazardous materials into environ-
ment. Therefore, there remains room to develop greener,
milder, and simpler protocols based on application of
retrievable catalysts or green solvents to avoid the emis-
sion of hazardous substances into environment and run
the synthesis of pyrimido[1,2-a]benzimidazole ring sys-
tems efficiently.
In continuation of our interest in exploring cata-
lytic methodologies,[13] we have synthesized Cu–PSA
complex immobilized on GO and then investigated its
performance as a novel acidic nanocatalyst for the syn-
thesis of pyrimido[1,2-a]benzimidazoles. To the best of
our knowledge, there are no reports on the use of Cu–
PSA complex immobilized on GO as a catalyst for the
synthesis of pyrimido[1,2-a]benzimidazoles via MCRs
(Figure 1).
Of these heterocyclic compounds, pyrimido[1,2-a]
benzimidazoles have attracted immense attention because
of their valuable pharmacological properties and
clinical applications.[7] The one-pot three-component
condensation reaction between β-dicarbonyl compounds,
FIGURE 1 One-pot synthesis of pyrimido[1,2-a]benzimidazole derivatives in the presence of GO@PSA-Cu. GO, geraphene oxide; PSA,
polysulfonamide

SHEKARLAB ET AL.
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FIGURE 2 Fourier-transform infrared of (a) geraphene oxide
(GO), (b) GO@PSA, (c) GO@PSA-Cu. GO, geraphene oxide; PSA,
polysulfonamide
2 | EXPERIMENTAL
FIGURE 3 Field emission scanning electron microscopy
image of the synthesized catalyst
2.1 | Materials and methods
All commercially available chemicals were obtained from
Merck and FLUKA companies, and used without further
purification otherwise stated. Nuclear magnetic reso-
nance (NMR) spectra were recorded in CDCl3 on Bruker
AVANCE spectrometers 400 MHz for 1H NMR and
100 MHz for 13C NMR using tetramethylsilane as an
internal standard; chemical shifts were expressed in parts
per million (ppm). Infrared (IR) spectroscopy was con-
ducted on a Perkin Elmer GX Fourier-transform infrared
(FT-IR) spectrometer. Mass spectra were recorded on a
Shimadzu QP 1100 BX mass spectrometer. Melting points
were determined on a Stuart Scientific SMP3 apparatus.
Thermo-gravimetric analysis (TGA) was performed on a
PYRIS Diamond instrument (London, UK). Energy-
dispersive X-ray analysis of the prepared catalyst was
performed on an field emission scanning electron micros-
copy (FESEM; SIGMA, Zeiss, Germany) instrument.
Scanning electron microscopy (SEM) was performed on
with China KYKY- EM3200 instrument operated at
30-kV accelerating voltage. Prior to the surface area anal-
ꢀ
ysis, the samples were activated in high vacuum at 80 C
for 12 h. Adsorption and desorption measurements were
FIGURE 4 Thermogravimetric analysis
curve of the synthesized GO@PSA-Cu
nanocomposite. GO, geraphene oxide; PSA,
polysulfonamide

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SHEKARLAB ET AL.
FIGURE 5 N2 adsorption–desorption
isotherms of GO@PSA-Cu. GO, geraphene
oxide; PSA, polysulfonamide
performed on a Micromeritics TriStar 3020 version 3.02
(N2) system and measured at 77 K. The data were ana-
lyzed using the TriStar II 3020 version 1.03 software
(Micromeritics, Norcross, GA, USA). Wavelength-
dispersive X-ray spectroscopy (WDX) was performed
using a TESCAN MIRA3.
2.3 | General procedure for the synthesis
of pyrimido[1,2-a]benzimidazole using
GO@PSA-Cu
To a 5-mL flask, various aldehydes (1.0 mmol), ethyl
acetoacetate (1 mmol, 0.130 g), 1H-benzimidazole-
2-amine (1 mmol, 0133 g), GO@PSA-Cu (0.05 g), and
EtOH (2 mL) were added and the reaction was stirred
2.2 | Synthesis of geraphene
oxide@polysulfonamide-Cu (GO@PSA-Cu)
In this research, GO was prepared from graphite powder
using a modified Hummer’s method.[14] Then, 1 g of
polybenzene-1,3-disulfonylamide and CH3CN (20 mL)
were slowly added to the GO (1 g) and magnetically
stirred at 60 ꢀC. After completion of the reaction, the
obtained black GO@PSA were separated from the reac-
tion medium by centrifusion, and then washed with
CH3CN three times. The obtained GO@PSA were dried
for 120 min at 90 ꢀC. To prepare the GO@PSA–Cu
nanosheet, the obtained GO@PSA (1 g) was dispersed in
50 mL EtOH by sonication for 30 min, and then 0.5 g of
Cu(OAc)2 was added to the aforesaid mixture. A brown
suspension was formed that was refluxed with vigorous
stirring for 24 h. The catalyst (GO@PSA-Cu) was
separated from the solution by centrifusion, washed
with deionized water several times, and dried in an
oven overnight.
FIGURE 6 Energy-dispersive X-ray spectrum of the
GO@PSA-Cu nanocomposite. GO, geraphene oxide; PSA,
polysulfonamide

SHEKARLAB ET AL.
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FIGURE 7 Elemental mapping of the GO@PSA-Cu nanocomposite. GO, geraphene oxide; PSA, polysulfonamide
for an appropriate reaction time under reflux condi-
tion. The progress of the reactions was monitored by
thin-layer chromatography (n-hexan:EtOAc) (10:4).
After completion of the reaction, the resulting mixture
was filtered and the catalyst was separated from the
product via centrifusion. The catalyst was washed with
hot distilled H2O (5 mL) and EtOH (3 mL) two times.
The crude products were collected and recrystallized
from EtOH if necessary.
Ethyl 4-(3-bromophenyl)-1,4-dihydro-2-methylpyrimido
[1,2-a]benzimidazole-3-carboxylate (4e): melting point:
289–291 ꢀC.[12] Light solid. IR (KBr): 3237, 1697, 1656,
1619, 1572, 1262, 1091, 731. 1H-NMR (400 MHz): 1.17
(t, J = 7.2 Hz, Me); 2.47 (s, CH3); 4.05 (q, J = 7.2 Hz, CH2);
6.47 (s, CH); 6.98–7.62 (m, 8 ArH); 10.76 (s, NH). 13C-NMR
(100 MHz): 14.5; 19.1; 55.7; 59.9; 97.7; 110.3; 117.3; 120.8;
121.9; 122.4; 126.5; 130.4; 131.1; 131.2; 131.8; 142.7; 145.1;
145.8; 147.5; 165.4. Anal. Calc: C 58.26, H 4.40, N 10.19;
found: C 57.80, H 4.08, N 10.02. All products were charac-
terized on the basis of their spectroscopic data including 1H
NMR, 13C NMR, and CHN that are given in the supporting
information (Figures S1-S30).
3 | RESULTS AND DISCUSSIONS
Cu–PSA complex supported on GO was prepared in three
steps. At first, GO was synthesized using a modified Hum-
mer’s method.[14] Next, polybenzene-1,3-disulfonylamide
was synthesized based on our previous work.[15] The method
is based on the modification of GO by the chemical and
physical interaction of polybenzene-1,3-disulfonylamide with
surface functional groups on the GO. Finally, the GO@PSA
was coordinated with Cu(OAc)2 to generate Cu–PSA
complex supported on GO. The synthesis steps of GO@PSA-
Cu are depicted in Figure 1. The GO@PSA-Cu was charac-
terized by various techniques such as FT-IR, TGA, FESEM,
WDX, EDS, and N2 adsorption–desorption. The FT-IR
spectra of GO, GO@PSA, and GO@PSA-Cu are illustrated
in Figure 2a–c. Wave numbers of the C–O–C bonds appear
at 1047 cm−1. The adsorption bands at 1613 and 1721 cm−1
were attributed to the C=C and C=O groups and the band
at 3383 cm−1 corresponded to the broad OH groups on the
surface of GO. In addition, in the FT-IR spectrum of GO, an
adsorption band appears at 1047 cm−1 that is assigned to the
C–O–C groups (Figure 2a). After grafting PSA, the peaks at

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SHEKARLAB ET AL.
analysis, pore volume and pore diameter were 0.05 cm3/g
and 20.80 nm, respectively.
TABLE 1 Optimizing the reaction conditions for the synthesis
of 4a using GO@PSA-Cu as the catalysta
The EDS analysis of the synthesized catalyst is shown
in Figure 6. As can be seen, the structure of the catalyst
GO@PSA-Cu is composed of the expected elements,
including oxygen, sulfur, nitrogen, carbon, and copper,
which indicates that Cu has been correctly grafted to
GO@PSA. Elemental mapping analysis suggested the
homogeneous distribution of all elements (Figure 7). The
concentration of copper in GO@PSA-Cu (8.17 wt%) was
determined by inductively coupled plasma–optical emis-
sion spectrometry.
Catalyst
Entry loading (g)
Time
(min)
Yieldb
(%)
Conditions
1
2
3
4
5
6
0.05
0.05
0.05
0.05
0.05
0.05
EtOH (reflux)
CH3CN (reflux)
CH3Cl (reflux)
10
10
10
95
88
78
68
45
50
Toluene (reflux) 10
H2O (reflux)
10
10
Solvent free
(100 ꢀC)
7
8
0.05
0.05
Solvent free
(80 ꢀC)
10
30
45
55
3.1 | Catalytic activity
EtOH (room
temperature)
We next investigated the catalytic effect of GO@PSA-Cu
9
0.01
0.03
0.07
0.05
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)c
10
10
10
10
61
81
95
30
nanocomposite
on
the
synthesis
of
ethyl
10
11
12
4-(4-chlorophenyl)-2-methyl-1,4-dihydrobenzo[4,5]imidazo
[1,2-a]pyrimidine-3-carboxylate 4a as a model compound
(Table 1). First, the reaction was carried out by refluxing
the reaction mixture in different solvents such as EtOH,
H2O, CHCl3, CH3CN, and toluene (Table 1, Entries 1–5);
under solvent-free conditions (Table 1, Entries 6 and 7),
and at room temperature (Table 1, Entry 8). The experi-
mental results in Table 1 revealed that refluxing in EtOH
presented the optimum values of reaction variables
(Table 1, Entry 1), whereas using H2O, CHCl3, CH3CN,
and toluene as solvent resulted in reduced yields. A study
of the catalyst content (Table 1, Entries 9–11) showed that
50 mg of catalyst is the optimal value for this reaction
(Table 1, Entry 1); importantly, catalyst content less than
50 mg resulted in a low reaction yield (Table 1, Entries
9 and 10), and the yield of the product did not increase by
increasing the catalyst content to more than 50 mg
(Table 1, Entry 11). Further increasing the temperature to
100 ꢀC did not have a significant effect on the yield (Entry
6). We also observed that the product yield was decreased
in the presence of GO@PSA in comparison with
GO@PSA-Cu (Table 1, Entry 12).
These results motivated us to examine the generality
of this approach for different aromatic aldehydes and ani-
lines under optimized conditions. According to Table 2, a
broad substrate scope is observed for both electron-
donating and electron-withdrawing substituents and
aliphatic aldehydes. Different types of aldehydes such as
p-Cl, m-Br, m-methoxy, o-methoxy, m-Cl, p-methoxy,
2,4-Cl2, 2,3-Cl2, 3,4,5-(MeO)3, anthracen-9-yl, or aliphatic
groups such as hexanaldehyde and propanaldehyde were
used to synthesize diverse structurally functionalized
pyrimido[1,2-a]benzimidazole derivatives. These results
indicate that different types of aldehydes efficiently par-
ticipated in the studied reactions, which lead to the
aReaction condition: p-chlorobenzaldehyde (1 mmol), ethyl
acetoacetate (1 mmol), 1H-benzimidazole-2-amine (1 mmol),
GO@PSA-Cu (0. 05 g), and EtOH (2 mL) were stirred under reflux
condition.
bIsolated yield.
cp-Chlorobenzaldehyde (1 mmol), ethyl acetoacetate (1 mmol),
1H-benzimidazole-2-amine (1 mmol), GO@PSA (0.05 g), and EtOH
(2 mL) was stirred under reflux condition.
1168 and 1334 cm−1 can be assigned to the S=O stretching
vibrations (Figure 2b). In addition, when copper coordinates
with PSA, the S=O bonds shift to lower wave numbers
(1148 and 1312 cm−1; Figure 2b vs 2c).
Morphological characterizations of GO@PSA-Cu
were investigated with the FESEM technique. FESEM
images show that the particles are corrugated sheets with
an average diameter of about 33–40 nm (Figure 3).
The thermal behavior of GO@PSA-Cu was studied
by TGA with a heating rate of 10 ꢀC min−1 within a
temperature range of 0–400 C (Figure 4). The composi-
tion ratio of the catalyst can be calculated from the
residual mass percentage. As shown in Figure 4, the
first weight loss stage at almost 100 C was assigned to
the evaporation of adsorbed water molecules. The
second weight loss at 250–400 C can be attributed to
the removal of functional groups on the grafted poly-
mer. According to the obtained results, PSA-Cu is well
connected to the GO nanoparticles.
The Brunauer–Emmett–Teller (BET) surface areas
were determined by N2 adsorption (Figure 5). The surface
areas for GO@PSA-Cu were found to be 50 m2/g. Fur-
thermore, according to Barrett–Joyner–Halenda (BJH)
ꢀ
ꢀ
ꢀ

SHEKARLAB ET AL.
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TABLE 2 Synthesis of pyrimido[1,2-a]benzimidazoles using GO@PSA-Cu as catalysta
Compound
4a
Product
Time (min)
Yield (%)b
MP (ꢀC)
10
95
302–303[12]
250–252[12]
300–302[12]
4b
4c
10
12
92
95
4d
12
90
289–290[12]
4e
4f
20
30
95
91
266–268[12]
211–212[12]
4g
30
90
265–269[12]
4h
4i
25
35
93
90
223–225[12]
198–199[12]
(Continues)

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SHEKARLAB ET AL.
TABLE 2 (Continued)
Compound
4j
Product
Time (min)
Yield (%)b
MP (ꢀC)
45
90
295–298[12]
4k
4l
60
60
91
93
157–158[12]
180–182[12]
aReaction condition: benzaldehyde derivatives (1 mmol), ethyl acetoacetate (1 mmol), 1H-benzimidazole-2-amine (1 mmol), GO@PSA-Cu (0.
05 g), and EtOH (2 mL) were stirred under reflux condition.
bIsolated yield.
formation of desired products at acceptable times with
good to excellent yields. In addition, the nature and elec-
tronic properties of the substituents had negligible effect
on the velocity and reaction yields. All products were
fully characterized on the basis of their SPECTRONIC
data including FT-IR, 1H NMR, 13C NMR, and CHN.
In the next step, the reusability of GO@PSA-Cu was
also evaluated in the synthesis of 4a under the optimized
reaction conditions. For this purpose, after the comple-
tion of the reaction, the mixture was filtered ofꢀf. Then the
solvent was removed under vacuum up to 70 C and the
obtained catalyst was washed with ethanol for better
purification and dried. These results show that, even after
six sequential runs, the catalytic activity of the catalyst
remained approximately unchanged in the preparation of
4a (95%, 95%, 93%, 91%, 89%, 88%; Figure 8).
The filtration test for the reaction between
3-methoxybenzaldehyde, ethyl acetoacetate, and
1H-benzimidazole-2-amine using GO@PSA-Cu as a cata-
lyst was performed to investigate the leaching of copper
during the reaction. A catalytic run was started as for a
standard reaction, and after 15 min (the reaction was
completed in 30 min), corresponding to 50% conversion,
the mixing of reaction mixtures was stopped and the
contents were centrifuged to obtain afford a clear filtrate.
Then, the mixture without the solid catalyst was
subjected to a standard catalytic run for another 15 min,
but no significant conversion occurred. The results
FIGURE 9 Reaction between 3-methoxybenzaldehyde, ethyl
acetoacetate and 1H-benzimidazole-2-amine over GO@PSA-Cu:
(a) Hot filtration test; (b) normal reaction. GO, geraphene oxide;
PSA, polysulfonamide
FIGURE 8 Recyclability of the GO@PSA-Cu nanocomposite.
GO, geraphene oxide; PSA, polysulfonamide

SHEKARLAB ET AL.
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SCHEME 1 One-pot synthesis of pyrimido[1,2-a]benzimidazole derivatives in the presence of GO@PSA-Cu
TABLE 3 Comparison of the present methodology with other reported catalysts for the synthesis of ethyl
4-(4-methoxyphenyl)-2-methyl-1,4-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carboxylate (4 h)
Entry
Catalyst
Condition
Time
Yield (%)
Reference
1
GO@PSA-Cu (3.5 mol%)
EtOH, reflux
25 min
93
This work
[16]
2
1,1,3,3-N,N,N0,N0-tetramethylguanidinium
100 ꢀC
5 h
67
trifluoroacetate (30 mol%)
[10]
[17]
[18]
3
4
5
L-Proline (20 mol%)
H2O, reflux
H2O, reflux
90 ꢀC
2.5 h
3 h
88
85
73
Thiamine hydrochloride (5 mol%)
α-Zirconium sulfophenylphosphonate (12 mol%)
20 h
GO, geraphene oxide; PSA, polysulfonamide.
were compared with those of a standard catalytic run.
Figure 9 clearly shows that after the removal of the
heterogeneous catalyst, slow progression of the reaction
occurred. This indicates that the prepared catalyst is
stable and the leaching of copper species from the solid
support is low.
The proposed mechanism of this reaction is shown in
Scheme 1. According to this mechanism, at first, the
carbonyl group of aldehyde 1 is activated with the copper
species of the catalyst to make intermediate a. The
Michael addition of 3 to the Knoevenagel product
followed by cyclization and tautomerization generated
the corresponding product.[12]
4 | CONCLUSIONS
In conclusion, a novel and efficient complex (GO@PSA-Cu)
has been developed as a highly active and recoverable
heterogeneous catalyst for the synthesis of pyrimido
[1,2-a]benzimidazoles via a multicomponent reaction
of various benzaldehydes, ethyl acetoacetates, and
1H-benzimidazoles. The method offered several advan-
tages, including excellent yields, recyclability of
the catalyst, short reaction times, easy purification, and
simple procedure.
ACKNOWLEDGEMENTS
The efficiency of GO@PSA-Cu for the synthesis
of 4-(4-methoxyphenyl)-2-methyl-1,4-dihydrobenzo[4,5]
imidazo[1,2-a]pyrimidine-3-carboxylate (4 h) was com-
pared with some other related reports (Table 3). In this
work, using GO@PSA-Cu as a recyclable catalyst remark-
ably enhanced the product yield and shortened the
reaction time.
We thank Bu-Ali Sina University, Center of Excellence in
Development of Environmentally Friendly Methods
for Chemical Synthesis (CEDEFMCS) for the financial
support of this study.
Shekarlab. N, Ghorbani-Vaghei. R, Alavinia. S, Prepa-
ration and characterization of copper/polysulfonamide
complex immobilized on geraphene oxide as a novel

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SHEKARLAB ET AL.
[13] a) R. Ghorbani-Vaghei, S. Alavinia, N. Sarmast, Appl.
Organomet. Chem. 2018, 32, e4038; b) R. Ghorbani-Vaghei,
S. Alavinia, Z. Merati, V. Izadkhah, Appl. Organomet. Chem.
2018, 32, e4127; c) A. Kharazmi, R. Ghorbani-Vaghei,
S. Alavinia, ChemistrySelect 2020, 5, 1; d) A. Fatehi,
R. Ghorbani-Vaghei, S. Alavinia, J. Mahmoodi, Che-
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K. Derakhshandeh, R. Haddadi, A. R. Nouriand, R. Ghorbani-
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C. H. Voon, Procedia. Eng. 2017, 184, 469.
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[16] A. Shaabani, A. Rahmati, S. Naderi, Bioorg. Med. Chem. Lett.
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catalyst for the synthesis of pyrimido[1,2-a]benzimid-
azoles. Appl Organometal Chem. 2020, AOC-20-0608.
CONFLICTS OF INTEREST
The authors have no conflict of interest to declare.
ORCID
Ramin Ghorbani-Vaghei https://orcid.org/0000-0001-
8322-6299
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GO, geraphene oxide; PSA, polysulfonamide.
GO, geraphene oxide; PSA, polysulfonamide.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
How to cite this article: Shekarlab N, Ghorbani-
Vaghei R, Alavinia S. Preparation and
characterization of copper/polysulfonamide
complex immobilized on geraphene oxide as a
novel catalyst for the synthesis of pyrimido[1,2-a]
benzimidazoles. Appl Organomet Chem. 2020;
e5918. https://doi.org/10.1002/aoc.5918
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