Copper coordinated-poly(α-amino acid) decorated on magnetite graphene oxide as an efficient heterogeneous magnetically recoverable catalyst for the selective synthesis of 5- and 1-substituted tetrazoles from various sources: A comparative study

Article abstract of DOI:10.1002/aoc.5273

In this work, poly(α-amino acid)-Cu(II) complex immobilized on magnetite graphene oxide (GO/Fe₃O₄?PAA-Cu-complex) was prepared via a multistep synthesis and employed as an efficient, heterogeneous, magnetically recyclable nanocatalyst for one-pot, three component synthesis of 5- and 1-substituted tetrazoles using different substrates including benzaldehydes, benzonitriles, and anilines in mild conditions. The different approaches were mechanically investigated and compared. The catalyst was fully characterized by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma (ICP), FE-SEM and TEM analyses. The magnetic nanocatalyst could be readily separated from the reaction mixture by an external magnet and reused for several times without significant loss of catalytic activity. Also, the spectroscopic analysis revealed the stability and durability of the catalyst. Finally, the chemoselectivity of the method was investigated by the various combinations of aldehyde, nitrile, and oxime.

Full text of DOI:10.1002/aoc.5273

Received: 21 February 2019
DOI: 10.1002/aoc.5273
Revised: 24 August 2019
Accepted: 11 September 2019
F U L L P A P E R
Copper coordinated-poly(α-amino acid) decorated on
magnetite graphene oxide as an efficient heterogeneous
magnetically recoverable catalyst for the selective synthesis
of 5- and 1-substituted tetrazoles from various sources: A
comparative study
Milad Kazemnejadi1
Mohammad A. Nasseri1
| Boshra Mahmoudi2 | Zeinab Sharafi3
|
| Ali Allahresani1 | Mohsen Esmaeilpour4
1Department of Chemistry, Faculty of
Sciences, University of Birjand,
Birjand, Iran
2Research Center, Sulaimani Polytechnic
University, Sulaimani, Iraq
3Razi Herbal Medicines Research Center,
Lorestan University of Medical Sciences,
Khorramabad, Iran
4Department of Chemistry, College of
Science, Shiraz University, Shiraz, Iran
In this work, poly(α-amino acid)-Cu(II) complex immobilized on magnetite
graphene oxide (GO/Fe3O4@PAA-Cu-complex) was prepared via a multistep
synthesis and employed as an efficient, heterogeneous, magnetically recycla-
ble nanocatalyst for one-pot, three component synthesis of 5- and 1-
substituted tetrazoles using different substrates including benzaldehydes,
benzonitriles, and anilines in mild conditions. The different approaches were
mechanically investigated and compared. The catalyst was fully character-
ized by Fourier transform infrared (FTIR), thermogravimetric analysis
(TGA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM),
energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma
(ICP), FE-SEM and TEM analyses. The magnetic nanocatalyst could be read-
ily separated from the reaction mixture by an external magnet and reused
for several times without significant loss of catalytic activity. Also, the spec-
troscopic analysis revealed the stability and durability of the catalyst. Finally,
the chemoselectivity of the method was investigated by the various combina-
tions of aldehyde, nitrile, and oxime.
Correspondence
Milad Kazemnejadi, Department of
Chemistry, Faculty of Sciences, University
of Birjand, Birjand 97175-615, Iran.
Email: miladkazemnejadi@birjand.ac.ir
Funding information
Research Council of University of Birjand
K E Y W O R D S
copper complex, graphene oxide, poly(α-amino acid), 5-substituted 1H-tetrazole, 1-substituted-
1H-1,2,3,4-tetrazoles
1 | INTRODUCTION
have been reported for tetrazole derivatives in agricul-
ture, photography,[4] and industry.[5] They are also effi-
Tetrazoles and their derivatives are one of the most
applicable N-heterocyclic compounds, which their
application has increased rapidly over the past few
years due to their unique biological properties such as:
antibiotic, antialergic, antifungal,[1] antihypertensive,
anticonvulsant agents, anti-inflammatory, anti-HIV
activities, etc.[2,3] Furthermore, widespread applications
cient ligand and widely used in coordination
chemistry.[6] In chemistry, tetrazoles are used for the
preparation of nitrogen-containing compounds for
design of therapeutic drugs, and isosteric substituent
for carboxylic acids.[2] In material science, they have
role in the production of explosive and rocket
propellants.[7]
Appl Organometal Chem. 2019;e5273.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
1 of 15
https://doi.org/10.1002/aoc.5273

2 of 15
KAZEMNEJADI ET AL.
Different approaches have been developed for the
interesting properties such as sheet structure, nano-size
dimension with high surface area, high thermal/ chemi-
cal stability and possibility of functionalization with
various organic compounds become as one of the most
suitable solid support for organic synthesis.[24–26] Fur-
ther improvement in heterogeneous catalysts lead to
preparation of magnetic nanoparticles that facilitates
the separation of catalyst by an external magnetic
field.[27] Fe3O4 nanoparticles are one of the most appli-
cable magnetic nanoparticles due to their widespread
applications in various fields of area such as catalyst
and biomedical applications.[28,29] Some advantages are
associated with them including low cost, high thermal
stability, non-toxic, chemical stability, strong magnetiza-
tion, and high crystalline structure, which conducted
them for magnetization of other solid supports. This is
a smart strategy for magnetization of solid supports, in
this case nano graphene oxide, which has been used
extensively in the last decades.[25,27]
preparation of tetrazole derivatives by different starting
materials including: aldehyde,[8] oxime,[9] nitrile,[10] and
amine.[11] Two main categories of tetrazoles are 5-
substituted-1H- and 1-substituted-1H-1,2,3,4-tetrazoles.
Two main routes have been developed for the preparation
of 1-substituted-1H-1,2,3,4-tetrazoles using (a) cycloaddi-
tion between isocyanide and hydrazoic acid, and (b) the
reaction of amines with orthoformate or orthocarboxylic
acid ester in the presence of an azide salt.[12,13] Various
catalytic systems have been developed for the preparation
of 1-substituted-1H-1,2,3,4-tetrazoles including: silica sul-
furic acid,[12] Brønsted acidic ionic liquids,[13]
Fe3O4@silica sulfonic acid,[14] Fe3O4@WO3-EAE-SO3H
(aminoethanesulfonic acid immobilized on epichlorohy-
drin
functionalized
Fe3O4@WO3),[15]
Fe3O4@Quindiol@Cu nanocatalyst,[16] silver oxide,[17]
and tributylmethylammonium chloride (TBMAC).[11]
Recently, Pharandeh and co-workers reported
a
isocyanide based synthesis of 1-substituted-1H-1,2,3,4-
tetrazoles under ultrasonic conditions.[18]
In this article, given the notable properties and inevi-
table application of tetrazole derivatives in various fields
of area, herein, in the development of sustainable chem-
istry, we have prepared Cu(II) complex of a synthetic
poly (α-amino acid) and then immobilized on GO/Fe3O4
NPs (as a nano-magnetic support) as an efficient magnet-
ically recoverable catalyst for the efficient transformation
of aldehyde, amine, nitrile and oxime to the
corresponding tetrazoles. Mild reaction conditions, low
catalyst amount, versatility of the catalyst toward a vari-
ety of substrates, applicable in various reaction condi-
tions, low metal leaching, preparation of the catalyst
from cheap and available starting materials, free of any
toxic/hazardous reagent, easy reuse and recovery without
any pre-activation, durability, high thermal stability and
high chemoselectivity are some advantages of the present
method, which makes it superior to previously reported
catalysts for efficient and reliable preparation of 5- and 1-
substituted tetrazoles from various sources. The main
objective of this paper is study on the preparation of
tetrazole ring through a various approaches based on the
used substrate as well as introduction of an efficient and
general method for preparation of a variety of 1- and 5-
substituted tetrazoles using different substrates. For each
On the other hand, the straightforward and facile
route for the preparation of 5-substitited-1H-tetrazoles
first developed by Hantzsch and Vagt through a [3+2]
cycloaddition of azide ion with nitriles as a main and
popular method.[9] This method involves high reaction
temperature, tedious work-up, expensive and toxic sol-
vent, that is not efficient from environmentally consider-
ations point of view. Thus, numerous efforts made by
scientists for finding more sustainable and economic
friendly alternative methods. The literature demonstrat-
ing various routes to reach 5-substituted-1H-tetrazoles.
Among recent advances can be point to: Pd-
SMTU@boehmite (SMTU= S-methylisothiourea),[19]
Ni(OH)2 NPs,[20] choline azide,[10] MCM-41@AMPD@Zn
(2-amino-2-methyl-1,3-propandioal),[21]
and
Sm@l-
MSN,[22] and Cu-MOF nanocatalyst (MOF=metal
organic framework).[23]
However, some impediments and drawbacks are still
associated with them such as: high reaction tempera-
ture, use of toxic solvents, long reaction times, expen-
sive and/or toxic catalyst and so on, which
development of a novel, safe, inexpensive and general
protocol for preparation of the various types of
tetrazoles is required.
transformation
discussed.
a
mechanism was proposed and
The preparation and development of a heteroge-
neous catalytic system is of great interest in organic
synthesis because of reusability, manipulation for a spe-
cific goal, and also from eco- and economic viewpoint.
So, various solid supports have been developed for this
goal including: carbon nanotube (CNT), zeolite,
2 | EXPERIMENTAL
2.1 | Materials and apparatus
graphene,
MCM-41,
KCC-1,
clay,
carbon,
All chemicals were obtained from Sigma and Fluca
supplier and used as received without further
etc.[15,16,19,21,23] Among them, graphene oxide with the

MAGNETITE CU COMPLEX OF POLY(α-AMINO ACID) FOR TETRAZOLES SYNTHESIS
3 of 15
purification. All the solvents were distilled and dried
before use. Progress of the reactions and purity of
products were monitored by thin layer chromatography
(TLC) on silica gel and/or gas chromatography (GC)
on a Shimadzu-14B gas chromatography equipped with
HP-1 capillary column and N2 as carrier gas. For GC
analyses, anisole was used as an internal standard.
Purification of imines and oximes was achieved by
recrystallization from ethanol. FTIR spectra were
obtained using a JASCO FT/IR 4600 spectrophotometer
using KBr pellet. The 1H NMR (250 MHz) and
13CNMR (62.9 MHz) spectra were recorded on a
Bruker Avance DPX-250 spectrometer in CDCl3 and
DMSO-d6 as solvent (ESI). Field emission scanning
electron microscopy (FE-SEM) images were obtained
on a TESCAN MIRA3. Transmission electron micros-
copy (TEM) images were taken on a Philips EM208
microscope and was operated at 100 kV. The presence
of the elements was detected by EDX spectroscopy
using field emission scanning electron microscope (FE-
SEM, JEOL 7600F), equipped with a spectrometer of
energy dispersion of X-ray from Oxford instruments.
Size distribution of the nanoparticles were measured by
dynamic light scattering (DLS) analysis on a HORIBA-
LB550 instrument. TGA of the samples have been per-
formed on a NETZSCH STA 409 PC/PG in nitrogen
atmosphere with a heating rate of 10 ꢀC /min in the
temperature ranges of 25-1000 ꢀC. The magnetic behav-
KOH solution. Poly(α-amino acid) 4, was filter off, drying
and isolated as a stable powder (mp > 400 ꢀC). Scheme 1
shows the preparation of PAA 4 via the multistep
reactions.
2.2.2 | Preparation of GO
Graphene oxide (GO) was prepared according to a modi-
fied Hummer's method from purified natural
graphite.[31,32]
2.2.3 | Preparation of GO/Fe3O4 hybrids
GO–Fe3O4 hybrid was prepared via a chemical co-precip-
itation method according to the slightly modified litera-
ture procedure.[33,34] GO/Fe3O4 NPs were prepared with
a mass ratio of 1: 5 (GO: FeSO4). This premium ratio pro-
vides a suitable response to a magnetic field for the read-
ily separation of the NPs.[26] In a typical process, GO (25
mg) was first sonicated in 150 ml deionized water for 10
min. The mixture was stirred and heated to 80 ꢀC in an
oil bath. Then, NH4OH 25% solution was added dropwise
to the mentioned solution until the pH adjusted to 11.
Then, FeSO4.7H2O (125 mg) along with sodium dodecyl
sulfate (SDS) was added into the aqueous dispersion GO
solution. The resulting mixture was stirred under N2
ior of the samples was conducted on Lake Shore
vibrating sample magnetometer (VSM) at room temper-
ature. ICP experiments were accomplished using VAR-
IAN VISTA-PRO CCD simultaneous ICP-OES
instrument.
atmosphere for 24
h
at 80ꢀC. The GO/Fe3O4
nanoparticles were collected by an external magnetic
field followed by washing with deionized water several
times in order to eliminate excess iron salts. Finally, the
product was separated by a simple external magnet, then
dried in vacuum (40 ꢀC) for 4 hr (Scheme 1).
2.2 | Methods
2.2.4 | Preparation of GO/Fe3O4@PAA-cu
2.2.1 | Preparation of PAA
complex
In order to preparation of poly(α-amino acid) (PAA),
firstly, poly salicylaldehyde (PSA) was prepared
according to a previously reported procedure.[28–30] PSA
For the preparation of Go/Fe3O4@PAA-Cu complex, 20
mg of GO/Fe3O4 in 50 ml of DMF was ultra-sonicated for
1 hr, and then 0.2 g of N,N'-dicyclohexylcarbodiimide
(1.0 mmol, DCC) and 4-dimethylaminopyridine (DMAP)
along with 0.5 g of PAA were added into the solution.
The resultant mixture was stirred for 8 hr at 80 ꢀC under
N2 atmosphere. Complexation of copper ions to GO/
Fe3O4@PAA was carried out by sonication of GO/
Fe3O4@PAA (1.0 g) in 20 ml EtOH followed by addition
of Cu(OAc)2.H2O (10 mg) to the solution. The product,
Go/Fe3O4@PAA-Cu complex (8), was separated using an
external magnetic field, and then washed with water for
several times until the pH reached to 7, then dried into
oven (60ꢀC).
ꢀ
(0.1 g, Mn=2226) was added to 20 ml of water, then
NaCN (0.5 g, 10 mmol) and NH4Cl (0.5 g, 10 mmol) were
added to the reaction mixture. The reaction was refluxed
at 50 ꢀC for 12 hr. The resultant orange product (mp >
ꢀ
ꢀ
400 C, Mn= 2400), poly(α-amino nitrile) 3, was isolated
by simple filtration followed by drying into oven (50 ꢀC)
for 5 hr. Poly(α-amino nitrile) was transformed to poly(α-
amino acid) by hydrolysis of nitrile groups; 0.2 g of 3 was
added to 15 ml of water and along with several drops of
H2SO4 refluxed at 80 ꢀC for 12. The reaction mixture was
cooled to room temperature and neutralized with 0.5 N

4 of 15
KAZEMNEJADI ET AL.
SCHEME 1 A schematic synthesis route for the preparation of GO/Fe3O4@PAA-Cu-complex (8)
2.2.5 | General procedure for catalytic
preparation of 5-substituted-1H tetrazoles
by GO-Fe3O4@PAA-Cu-complex form
aldehyde, nitrile or amine
EtOAc-hexane to afford the desired 1-substituted
tetrazole.
From nitriles: A mixture of nitrile (1.0 mmol) and
NaN3 (1.5 mmol) in the presence of 0.02 g (1.0 mol%) of
Fe3O4@PAA-Cu-Complex was stirred at 100ꢀC in PEG-
400. The reaction progress was monitored using TLC.
After completion of the reaction, the mixture was cooled
to room temperature and the catalyst was removed mag-
netically. The residue was treated by HCl (4N, 10 mL)
and the desired tetrazole product was extracted by ethyl
acetate (3 × 10 mL). The combined organic extracts were
dried over Na2SO4 and then the solvent was removed
under reduced pressure to give the desired tetrazole.
All the tetrazole products are known and character-
ized by spectral analysis or melting point then, compared
with the previously reported spectra.
From aldehyde: Aldehyde (1.0 mmol) and hydroxyl amine
hydrochloride (1.5 mmol) along with Fe3O4@PAA-Cu-
Complex (0.02 g, 1.0 mol%) was added to 3 ml of water.
The mixture was stirred for 30 min at 70 ꢀC, then
1.5 mmol NaN3 was added to the mixture. The reaction
progress was monitored by TLC according to aldehyde
consumption. Upon reaction completion, the mixture
was diluted by 15 ml of ethyl acetate and the catalyst was
separated by an external magnetic field. The organic
layer was washed with HCl (10 ml, 4N) and dried over
Na2SO4. The solvent was removed under reduced pres-
sure and the resultant crude product was purified by
flash chromatography.
From oxime: Preparation of nitrile from oxime was
performed as same as aldehyde.
3 | RESULTS AND DISCUSSION
3.1 | Catalyst characterization
From amine: In a dried 25 ml round bottom flask, a
mixture of amine (1.0 mmol), triethyl orthoformate (1.2
mmol), Fe3O4@PAA-Cu-Complex (0.02 g, 1.0 mol% Cu)
and NaN3 was heated at 100 ꢀC for a sufficient time
with vigorous stirring. After completion of the reaction,
the mixture was cooled to room temperature, and then
extracted with ethyl acetate (3 × 15 ml). The catalyst
was magnetically removed and the combined organic
layers, were dried over Na2SO4 and concentrated under
reduced pressure. The products were re-crystalized with
According to GPC analysis of the prepared poly(α-amino
nitrile), Mw = 2400, it could be calculated that the pre-
sent nitrile functions per mole of poly(α-amino nitrile) is
17/2400 = 7 mmol. So, assuming that all of the nitrile
groups are converted to acid; the poly(α-amino acid) con-
tain 7.0 mmol acid functions per gram of PAA.
FTIR spectra of 5-chloromethyl salicylaldehyde, 2, 3,
4, GO (5), 6, 7, 8 are shown in Figure 1. The characteristic

MAGNETITE CU COMPLEX OF POLY(α-AMINO ACID) FOR TETRAZOLES SYNTHESIS
5 of 15
FIGURE 1 FTIR spectra of (A) 5-chloromethyl salicylaldehyde, (B) poly salicylaldehyde (2), (C) poly(α-aminonitrile) (3), (D) poly(α-
amino acid) (4), (E) GO (5), (F) Fe3O4@GO (6), (G) Go/Fe3O4@PAA (7), (H) Go/Fe3O4@PAA-Cu(II) (8)
peaks at 725 cm-1, 1481 cm-1, and some series vibrations
at 2900-2950 cm-1 are related to C-Cl (Str.), C-H (Ali-
phatic, Bend.), and C-H (Aliphatic, Str.) vibrations,
groups of GO surface. The peak at 1626 cm-1 represents
C=C stretching vibrations for aromatic rings related to
the unoxidized graphene oxide.[36] Advent of a strong
absorption at 572 cm-1 at GO/Fe3O4 FTIR spectrum indi-
cates the Fe-O (Str.) vibration, confirming the incorpora-
tion of Fe3O4 NPs on the GO. Another characteristic
peak was the reduction of O-H bond intensity due to the
decoration of Fe3O4 on the graphene oxide (Figure 1F).
Figure 1G, shows the amide bond linkage in 7 at
1622 cm-1. A shoulder at 1635 cm-1 could be attributed to
free C=O carboxylic bonds. Also, vibrations about 1400
cm-1 represents the bending vibrations of methylene
groups in the polymer (Figure 1G). Reduction in intensity
of peaks at carboxylic region, confirmed the successful
coordination of copper cations through these functional
groups as indicated in Scheme 1 (Figure 1H). Further-
more, advent of a peak at 450 cm-1 shows the Cu-O bond
stretching vibration,[8] confirming the successful coordi-
nation of Cu.
respectively,
which
completely
confirmed
the
chloromethylation of salicylaldehyde (Figure 1A).[28–30]
The polymerization of 5-chloromethyl salicylaldehyde
causes to a large reduction of O-H stretching vibration
intensity at 3400 cm-1, confirming that the polymeriza-
tion takes place through the ether bond formation (Fig-
ure 1B).[29] The preparation of α-amino nitrile via the
Strecker synthesis was characterized by a strong peak at
2110 cm-1 related to CN groups (Figure 1C). Moreover,
two characteristic peaks at 3500 and 3550 cm-1 demon-
strating amino groups in 3. Elimination of the sharp peak
refer to nitrile at the spectrum of 4, confirmed clearly
their transformation to carboxylic acids (Figure 1D). This
intensity reduction along with a red shift of the amino
groups in FTIR spectrum of poly(α-amino acid), could be
related to the formation of COO- NH3+, that is character-
istic for the typical amino acids.[35] Figure 1E, shows the
FTIR spectrum of graphene oxide. A peak at 1735 cm-1
was assigned to the stretching vibration of C=O for car-
boxylic groups (Figure 1E). The intense bond at 3422 cm-
The magnetic property of the samples was studied by
VSM analysis. The samples give a suitable and satisfac-
tory response to the applied magnetic field (Figure 2A).
No hysteresis phenomenon was found for the samples,
1
is attributed to the stretching vibration of hydroxyl
which
is
characteristic
of
superparamagnetic

6 of 15
KAZEMNEJADI ET AL.
FIGURE 2 (A) VSM curves of (a) Fe3O4, (b) GO/Fe3O4, and (c) GO/Fe3O4@PAA-Cu(II). (B) TGA spectra of (a) GO/Fe3O4,
(b) GO/Fe3O4@PAA and (c) GO/Fe3O4@PAA-Cu(II)
nanoparticles. These results confirmed the incorporation
of Fe3O4 NPs on GO. For comparison, Fe3O4 NPs were
separately prepared and studied by VSM. The analyses
show 78 emu.g-1, 65 emu.g-1, and 35 emu.g-1 saturation
magnetization for Fe3O4, GO/Fe3O4, and GO/
Fe3O4@PAA-Cu(II) respectively (Figure 2A, a-c). The
results indicate a large decrease in magnetization for cat-
alyst 8, which represent the functionalization of GO in
each step (Figure 2A-c).
The morphology of the NPs was studied by FE-SEM
technique. As shown in Figure 3A,B, the images clearly
demonstrated the chemical deposition of Fe3O4 NPs on
GO framework. The results from TEM analysis, also, con-
firmed the preparation of GO/Fe3O4@PAA-Cu(II) hybrid
with an average size of 28 nm for the particles (Fig-
ure 3C). The results obtained from DLS analysis (Fig-
ure 3D), revealed that the main size distribution of the
NPs are in the range of 20-30 nm. The mean size of the
NPs was found to be 30 nm with a deviation of 10.2, in
agreement with the corresponding TEM image.
XRD patterns of GO, GO/Fe3O4 and GO/
Fe3O4@PAA-Cu is shown in Figure 4A. GO represents
an amorphous peak at 2θ=10.8 related to (001) plane,
that is characteristic for the graphene oxide.[26] Fig-
ure 4A-a, shows the XRD pattern of GO/Fe3O4 with six
characteristic peaks at 2θ = 30.3ꢀ, 35.5ꢀ, 43.2ꢀ, 53.8ꢀ,
57.5ꢀ, 62.9ꢀ, which were assigned to their indices (220),
(311), (440), (442), (511), and (440) respectively.[25,26]
These reflections were in agreement with the crystal
structure of Fe3O4 NPs (JCPDS no. 19-0629). As shown in
Figure 4A-b, the intensity of the peak at 10.8ꢀ is largely
reduced. This behavior suggests that the Fe2+ ions act as
a reducing agent for graphene oxide.[25,27] The crystal
structure of the catalyst 8, was also demonstrated the
peaks for Fe3O4 crystal structure as well as a new amor-
phous peak at 2θ = 11ꢀ. Compared to the GO/Fe3O4 XRD
pattern, this peak could be assigned to the amorphous
PAA, that is coated on the GO framework. Furthermore,
the results also proved that the functionalization of GO/
Fe3O4 with PAA doesn’t lead to phase change of
Fe3O4 NPs.
The samples were further characterized by TGA anal-
ysis. TGA spectrum of GO/Fe3O4 indicates three main
weight losses (Figure 2B-a). In the first stage, slow weight
loss takes place near 80ꢀC correspond to 9% weight loss
due to desorption of water.[24] Another weight loss occurs
around 220ꢀC with a mild slope, which last to 440ꢀC.
This 18% weight loss exhibited the vaporization and
decomposition of various functional groups (Figure 1A)
on GO framework (Figure 2B-a). Finally, decomposition
of –COO- groups provide a weight loss of 12% above
600ꢀC in agreement with the literature.[24,25] An
enhancement in the thermal stability of GO/Fe3O4@PAA
was observed, demonstrating the influence of the coated
PAA on GO/Fe3O4 hybrid. Again, the small weight loss is
due to the release of water on the GO/Fe3O4@PAA at
180ꢀC (10% weight loss). A main weight loss in the tem-
perature range of 550-820ꢀC represents the decomposi-
tion of PAA on the GO/Fe3O4 (Figure 2B-b). This weight
loss is equal to 40% and confirming the loading amount
of PAA on the NPs. Coordination of copper to GO/
Fe3O4@PAA-Cu(II) showed an enhance in its thermal
stability, which the overall weight loss was found to be
53% at 1000ꢀC (compared to GO/Fe3O4@PAA-Cu(II)
with 57% weight loss). This difference may be attributed
to the coordinated copper in the GO/Fe3O4@PAA-Cu(II)
(Figure 2B-c). Also, the peak refer to the decomposition
of polymer takes place in lower temperatures with a
milder slope, that could be attributed to the effect of coor-
dinated copper to PAA.
The presence of the elements in the catalyst 8 was
detected by EDX analysis. As shown in Figure 4B, the
elements C, O, N, Cu, and Fe were detected, confirming
the structure of 8.
The amount of Cu in Go/Fe3O4@PAA-Cu(II) was also
determined by ICP analysis which is 0.50 mmol g-1. This

MAGNETITE CU COMPLEX OF POLY(α-AMINO ACID) FOR TETRAZOLES SYNTHESIS
7 of 15
FIGURE 3 (A), (B) FE-SEM images, (C) TEM image, and (d) DLS analysis of GO/Fe3O4@PAA-Cu(II)
FIGURE 4 (A) XRD patterns of (a) GO, (b) Go/Fe3O4, (c) Go/Fe3O4@PAA-Cu. (B) EDX spectrum of Go/Fe3O4@PAA-Cu

8 of 15
KAZEMNEJADI ET AL.
amount was completely in agreement and consistence
with the results from TGA analyses (Figure 2B-c).
water as a green solvent, benzaldehyde was transformed
to the corresponding 5-phenyl-1H-tetrazole with 95%
yield for 2 hr. On the other hand, PEG was the best
choice in the case of benzonitrile with 98% yield. These
results proposed two different routes for transformation
of aldehyde and/or benzonitrile to the desired tetrazole
(Figure 5A). Preparation of 1-phenyl-1H-1,2,3,4-tetrazole
give 85% isolated yield in PEG at 120 ꢀC, while under sol-
vent-free conditions excellent yield (96%) was obtained.
So, preparation of the desired tetrazole by benzaldehyde,
benzonitriles and amines were performed under water,
PEG and solvent-free conditions, respectively. The results
were summarized in Figure 5A.
Temperature was another effective parameter on
the transformation of all substrates to the
corresponding tetrazoles. As shown in Figure 5B, the
highest possible efficiency was found for 5-phenyl-1H-
tertazole at 100 ꢀC in PEG. The reaction efficiency
remains constant at higher temperatures. 5-Phenyl-1H-
tertazole could be generated from benzaldehyde at
moderate temperature (70 ꢀC) in water. Preparation of
3.2 | Optimization of reaction
parameters
In order to find optimum conditions for each experiment,
we applied three model reactions of: (1) benzaldehyde,
NaN3, NH2OH.HCl, catalyst; (2) benzonitrile, NaN3, cata-
lyst; and (3) aniline, NaN3, triethyl orthoformate and cat-
alyst. All of reactions were performed in the presence of
the optimum amount 0.02 g of the catalyst. The highest
possible efficiency was obtained in this amount for all
cases (Table 1). No detectable progress was found for
values greater than 0.02 g for all of them and the efficien-
cies remain constant at higher amounts. In following,
effect of solvent and temperature over transformation of
benzaldehyde, benzonitrile, and aniline to the
corresponding tertazoles were investigated (Figure 5A).
Polyethylene glycol, DMSO, and DMF were found to be
an efficient solvent for all of the substrates; however, in
1-phenyl-1H-1,2,3,4-tetrazole
from
aniline
were
TABLE 1 Effect of catalyst amount on the transformation reactions of benzaldehyde, benzonitrile, and aniline to the corresponding
tetrazole catalyzed by Go/Fe3O4@PAA-Cu(II) complex
From benzaldehydea
From benzonitrilea,b
From anilinec
Entry
Cat. amount (g)
0.010
Time (h)
Yield (%)d
Time (h)
Yield (%)d
Time (h)
0.5
Yield (%)d
1
2
3
4
5
2
2
2
2
2
68
84
95
95
96
7
7
7
7
7
55
80
98
98
96
70
86
96
96
96
0.015
0.5
0.020
0.5
0.030
0.5
0.040
0.5
aReaction conditions: benzaldehyde (1.0 mmol), NaN3 (1.5 mmol), hydroxyl amine hydrochloride (1.5 mmol), catalyst, water (3 ml), 70ꢀC.
bReaction conditions: Nitrile (1.0 mmol), NaN3 (1.5 mmol), catalyst, PEG-400, 100ꢀC.
cReaction conditions: Amine (1.0 mmol), triethyl orthoformate (1.2 mmol), catalyst, NaN3 (1.5 mmol), 100 ꢀC.
dIsolated yield
FIGURE 5 Effect of (A) solvent and (B) temperature on the preparation of 1- and 5-substituted tetrazoles frombenzaldehyde (blue
columns), benzonitrile (orange columns) and aniline (grey columns) catalyzed byGo/Fe3O4@PAA-Cu(II) complex. Except noted, the
reactions were performed under reflux conditions (3 ml of each solvent was used) in the presence of 0.02 g catalyst

MAGNETITE CU COMPLEX OF POLY(α-AMINO ACID) FOR TETRAZOLES SYNTHESIS
9 of 15
performed at 100 ꢀC under solvent-free conditions.
Effectiveness decreases sharply at low temperatures for
all three reactions.
With optimum conditions in hand, a series of benzal-
dehydes, benzaldehyde oximes and benzonitriles were
subjected to preparation of 5-substituted-1H-tetrazoles in
the presence of Go/Fe3O4@PAA-Cu(II) complex as a cat-
alyst. The results were tabulated in Table 2. Aldehydes/
nitriles/ oximes bearing activating and/or deactivating
group afforded high to excellent yields; however, the
deactivating group delays the reaction (Table 2, entries
4,5), nevertheless they provide approximately similar effi-
ciency to the aldehydes bearing electron donating groups
(Table 2, entries 2,3). The lowest efficiency was obtained
for 5-benzyl-1H-Tetrazole (Table 2, entry 6). As a conclu-
sion, the reaction efficiencies in terms of time and iso-
lated yield were better for oximes/ aldehydes than
nitriles. The conversion of tetrazole from nitrile has a sig-
nificantly higher time than either oxime or aldehyde. As
the "Mechanism study" section will be discussed, these
TABLE 2 Go/Fe3O4@PAA-cu(II) complex-catalyzed preparation of 5-substituted 1H-tetrazole
From aldehydea From oximea,c
From nitriled
Time
(min)
Yield
(%)b
Time
(min)
Yield
(%)b
Time
(h)
Yield
(%)b
Mp.
(ꢀC)[Lit.]
Entry Product 9
1
9a 120
95
85
98
7
98
213-215[19]
2
3
4
5
6
9b
9c
90
95
77
92
95
66
75
96
80
92
97
75
4
98
95
93
95
70
230-233[21]
249-250[19]
255-258[20]
150
120
5
9d 120
85
7
9e 340
320
340
8
225[19]
9f
340
14
121-122[8]
aReaction conditions: Aldehyde (1.0 mmol), NaN3 (1.5 mmol), hydroxyl amine hydrochloride (1.5 mmol), catalyst (0.02 g, 1.0 mol%), water (3 ml), 70 ꢀC.
bIsolated yield
cAldoxime (1.0 mmol)
dReaction conditions: Nitrile (1.0 mmol), NaN3 (1.5 mmol), catalyst (0.02 g, 1.0 mol%), PEG-400, 100 ꢀC.

10 of 15
KAZEMNEJADI ET AL.
results suggest a different mechanism pathway from
oxime or aldehyde. In this point of view, the present
method, proposed a promising way for the preparation of
oximes form aldehydes. Nitriles afforded the
corresponding tetrazoles in much higher reaction times
than oxime or aldehyde. However, high reaction yields
were obtained in this case.
Encouraged by the good results obtained from the
preparation of 5-substituted-1H-tetrazoles, we then exam-
ined the versatility of the present method toward the
preparation of 1-substituted-1H-1,2,3,4-tetrazole from
amines. Table 3 shows the scope of this reaction with a
different spectrum of amines in the presence of triethyl
orthoformate and the catalyst. High to excellent yields
were achieved at low reaction times for 1-substituted-1H-
1,2,3,4-tetrazole derivatives in the presence of amines
bearing electron donating or electron withdrawing
groups. In this case, also, amines containing electron
donating groups (Table 3, entries 2,3) provide more effi-
ciency than the inactive amines (Table 3, entries 4,5).
Benzyl amine afforded the lowest efficiency (88% for 1h)
for 1-benzyl-1H-tetrazole.
3.3 | Mechanism study
For the Cu-catalyzed 1- and 5-substituted tetrazole syn-
thesis, various mechanisms have been proposed
according to a used substrate. It has been shown that
tetrazole could be directly formed through nitrile,[10] or
oxime intermediate[8] at two different mechanisms.[36]
Oxime could be directly transformed to tetrazole in
milder conditions than nitrile.[10,37–39] Underwent reac-
tion conditions, didn’t found any benzonitrile in the reac-
tion of benzaldehyde, NaN3, NH2OH.HCl in the presence
of the catalyst in water. On the other hand, we prepared
the benzonitrile form benzaldehyde oxime in CH3CN at
80 ꢀC for 20 min (Scheme 2). These results propose that
the preparation of 5-substituted-1H-tetrazole from oxime
crosses another route. Another support for this claim
TABLE 3 Go/Fe3O4@PAA-Cu(II) complex-catalyzed preparation of 1-substituted-1H-1,2,3,4-tetrazolesa
Entry
Substrate
Product 10
Time (min)
Yield (%)b
M.P. (ꢀC)[Lit.]
1
10a
10b
30
96
64-65[16]
2
30
94
114-115[16]
3
4
5
6
10c
10d
10e
10f
40
80
95
60
95
96
90
88
185-187[30]
157-158[16]
201-202[16]
130-132[30]
aReaction conditions: Amine (1.0 mmol), triethyl orthoformate (1.2 mmol), catalyst (0.02 g, 1.0 mol%), NaN3 (1.5 mmol), 100 ꢀC.
bIsolated yield

MAGNETITE CU COMPLEX OF POLY(α-AMINO ACID) FOR TETRAZOLES SYNTHESIS
11 of 15
SCHEME 2 Preparation of 1- and 5-substituted tetrazole catalyzed by GO/Fe3O4@PAA-Cu-complex
SCHEME 3 Preparation of Cu-catalyzed 5-substituted 1H-tetrazole through different sources and their most possible corresponding
mechanisms
comes from successful isolation of benzaldehyde oxime
in the presence of benzaldehyde, NH2OH.HCl and cata-
lyst in water in absence of NaN3. Scheme 3 represents the
general suggested mechanisms for these transformations.
Moreover, the results from solvent effect (Figure 5A),
proposed that interaction of the catalyst works better
with aldehyde and oxime through oxygen atom (than
nitrile) in water (Scheme 3).
between transformation of oxime and nitrile to tetrazole,
convinced us that oxime goes through another mecha-
nism to get tetrazole. In this point of view, transforma-
tion of oxime to nitrile followed by nitrile to tetrazole
takes place in harsher conditions than the corresponding
direct transformation of oxime to tetrazole (Scheme 2, 3).
A plausible mechanism in agreement with the litera-
ture,[8,28,39] was proposed, wherein, it was started with
activation of oxygen atom of oxime by Cu sites (Interme-
diate I) followed by a facile [3+2] cycloaddition between
Absence of any nitrile intermediate for transforma-
tion of oxime to tetrazole catalyzed by GO/Fe3O4@PAA-
Cu complex as well as being different reaction conditions
-
N3 ion and C=N bond in oxime. Finally, the desired 5-

12 of 15
KAZEMNEJADI ET AL.
TABLE 4 Chemoselectivity behavior of the catalyst 8 in the
presence of aldehyde, oxime or nitrile
substututed-1H-tetrazole is formed by remove of a water
molecule (Scheme 3a-II). The transformation of oxime to
nitrile takes place by a hydride shift after chelation of the
catalyst to the oxygen of oxime. Then the nitrogen is
deprotonated and gives the nitrile (Scheme 3b-III and
IV). The most acceptable mechanism for the preparation
of 1-substituted tetrazole from aniline was sketched in
Scheme 4d.[37–39] According to this mechanism, the cata-
lyst is linked to azide ion and orthoformate, to form inter-
mediate VII (Scheme 3d). The reaction is proceeding by
the nucleophilic attack of amine to the activated
orthoformate. As shown in Scheme 3d, the catalyst facili-
tates the cleavage of C-O bonds by activation of ethoxy
groups.[40] Then, the [3+2] cyclization with azide in
(VIII) along with elimination of ethanol produces inter-
mediate (IX). Elimination of another EtOH generates the
desired tetrazole product.
Note to presence of poly(α-amino acid) chains on
GO/Fe3O4 NPs, a series of H-bonding could be probable
between carboxylic acid and hydroxyl functional groups
(Scheme 4). In this way, the catalyst provides a suitable
medium for the possible interaction of the reactants that
are insoluble in water. Also, azide as well as hydroxyl
amine ions could be readily interact with the functional
groups present on the PAA chains, lead to raise of effec-
tive concentration and progress of the reaction. This phe-
nomenon is shown in Scheme 4, where GO/
Fe3O4@PAA-Cu-complex nanoparticles could be readily
close to each other by H-bonding.
Conversion (%)a
Entry
1c,d
2e
Sampleb
9a
9b
70
-
9e
15
0
MBzA+ NBzN
BzAO + NBzN
MBzA + BzAO
-
100
55
3f,g
30
-
aGC analysis. Internal standard: anisole
bDefinition: MBzA: 4-methoxybenzaldehyde; NBzN: 4-nitrobenzonitrile;
BzAO: benzaldehyde oxime
cReaction conditions: MBzA (1.0 mmol), NBzN (1.0 mmol), hydroxyl amine
hydrochloride (1.5 mmol), catalyst (0.02 g, 1.0 mol%), NaN3 (1.5 mmol), PEG
(3 ml).
d15% 4-MeO-benzaldehyde oxime was found.
eReaction conditions: BzAO (1.0 mmol), NBzN (1.0 mmol), catalyst (0.02 g,
1.0 mol%), NaN3 (1.5 mmol), PEG (3 ml).
fReaction conditions: MBzA (1.0 mmol), BzAO (1.0 mmol), hydroxyl amine
hydrochloride (1.5 mmol), catalyst (0.02 g, 1.0 mol%), NaN3 (1.5 mmol),
PEG (3 ml).
g10% 4-MeO-benzaldehyde oxime and benzaldehyde oxime was found.
oxime (Table 4). The catalyst was completely selective
toward preparation of 5-(4-methoxyphenyl)-1H-tetrazole
(9b) in a mixture of 4-methoxybenzaldehyde and 4-
nitrobenzonitrile. Some 4-MeO-benzaldehyde oxime was
detected in this mixture. In another experiment, benzal-
dehyde oxime was specifically transferred to 9a in the
presence of 4-nitrobenzonitrile. It shows the facile prepa-
ration of 5-subtituted-1H-tetrazole form oxime in compe-
tition with nitriles. Interesting results were obtained from
the mixture of 4-MeO-benzaldehyde and benzaldehyde
oxime. The products were spread in this combination,
which 60% and 30% conversion was obtained for 9a and
9b respectively. Moreover, 10% 4-MeO-benzaldehyde
oxime and benzaldehyde oxime were also detected in the
mixture. As a conclusion, oxime and/or aldehyde could
be efficiently transferred to its corresponding tetrazole
without interfere of nitrile. The results provide another
evidence for transformation of 5-substituted tetrazole in a
different route.
In order to chemoselectivity investigation of the pre-
sent method, we design three combinations of 4-methoxy
benzaldehyde, 4-nitrobenzonitrile and benzaldehyde
The recoverability of Go/Fe3O4@PAA-Cu was investi-
gated for the reaction of benzaldehyde with NaN3 in
water, the reaction of benzonitrile with NaN3 in PEG-
400, and the reaction of aniline with triethyl
orthoformate/ NaN3. The results were summarized in
Figure 6. As shown in the figure, there is not any change
in conversion for the first cycle (Figure 6). An insignifi-
cant loss in reaction conversion was observed in other 5th
cycles for all experiment. Just a perceptible increase in
time was seen for the recycles, especially in the case of
the reaction of aniline with triethyl orthoformate/ NaN3
(Figure 6, purple pyramids).
SCHEME 4 A possible reaction mechanism for
GO/Fe3O4@PAA-Cu-complex catalyzed preparation of
5-substituted-1H-tetrazole

MAGNETITE CU COMPLEX OF POLY(α-AMINO ACID) FOR TETRAZOLES SYNTHESIS
13 of 15
images of the recovered catalyst with as same morphol-
ogy and size as the corresponding fresh catalyst. The cata-
lyst remains its magnetic property even after 6th run. As
shown in Figure 7C, the saturation magnetization of the
recovered catalyst (33.5 emu.g-1) was as much as the fresh
ones. Finally, the FTIR spectrum of the recovered catalyst
confirmed its structure (Figure 7D).
In order to manifest the heterogeneous nature of the
catalyst, the hot filtration experiment was applied on the
reaction of benzonitrile with NaN3 catalyzed by GO/
Fe3O4@PAA-Cu-complex in PEG-400 at 100 ꢀC. The cat-
alyst was magnetically separated after 3 h of the reaction
time. The afforded tetrazole product in this time was
36%. The reaction was allowed to proceed for further 4 h
without the catalyst. There is not found any progress in
the reaction, which the conversion reached to 38 % after
this time. The results show that no metal leaching was
happened to promote any catalytic reaction in the
medium. In this way, for more elucidation, the leaching
amounts were measured on the aforementioned reaction
for six consecutive reaction cycles. The residue was ana-
lyzed by ICP to measure the Cu contents in the mixture
after separation of the catalyst from the mixture. Further-
more, Fe amount was also measured in each cycle to clar-
ify the stability of the catalyst. The results show an
insignificant metal leaching in each cycle. It is worth not-
ing that no iron leached to the solution (0 %, ICP
FIGURE 6 Recycling of the Go/Fe3O4@PAA-Cu for the
preparation of 5-phenyl-1H-tetrazole (from benzaldehyde and
benzonitrile) and 1-phenyl tetrazole (from aniline) through three
different approaches
To show durability of the catalyst, the recovered cata-
lyst after 6th run in the reaction of benzonitrile with
NaN3 catalyzed by GO/Fe3O4@PAA-Cu-complex in PEG-
400 at 100ꢀC, was separated magnetically, washed with
deionized water and ethanol, dried into oven and ana-
lyzed by SEM, TEM, VSM, and FTIR to show its mor-
phology, size, magnetic behavior and structure
respectively. Figure 7A,B, shown the SEM and TEM
FIGURE 7 (A) FE-SEM, (B) TEM images, (C) VSM curve, and (D) FTIR spectrum of the recovered Go/Fe3O4@PAACu after 6th run

14 of 15
KAZEMNEJADI ET AL.
analysis). Cu leached for 1th to 6th was as order of: 0.3%,
0.8%, 1.0%, 1.3%, 1.5%, 1.9% respectively. This indicates
that the catalyst is stable during reactions, which cannot
be found any deactivation in terms of leaching.
[7] D. Fischer, T. M. Klapötke, J. Stierstorfer, Angew Chem Int Ed
2015, 54, 10299.
[8] M. Kazemnejadi, A. R. Sardarian, RSC Adv 2016, 6, 91999.
[9] S. D. Guggilapu, S. K. Prajapti, A. Nagarsenkar, K. K. Gupta,
B. N. Babu, Synlett 2016, 27, 1241.
[10] J. A. Mehraban, K. Azizi, M. S. Jalali, A. Heydari, Che-
mistrySelect 2018, 3, 116.
4 | CONCLUSION
[11] K. Nagaraju, G. Lalitha, P. Singh, C. V. Rao, Heterocycl
Commun 2017, 23, 365.
[12] D. Habibi, H. Nabavi, M. Nasrollahzadeh, J Chem 2013, 2012.
[13] G. Aridoss, K. K. Laali, Eur J Org Chem 2011, 2011, 2827.
[14] H. Naeimi, S. Mohamadabadi, Dalton Trans 2014, 43, 12967.
[15] M. S. Ghasemzadeh, B. Akhlaghinia, Bull Chem Soc Jpn 2017,
90, 1119.
[16] D. Habibi, N. Pakravan, A. Arabi, Z. Kaboudvand, Appl
Organomet Chem 2018, 32, e3988.
[17] F. A. K. Khan, Z. Zaheer, J. N. Sangshetti, R. Z. Ahmed, Chem
Data Collect 2018, 15, 107.
[18] S. G. Pharande, M. A. Rentería-Gómez, R. Gámez-Montaño,
New J Chem 2018, 42, 11294.
[19] P. Moradi, A. Ghorbani-Choghamarani, Appl Organomet
Chem 2017, 31, e3602.
[20] M. Halder, M. M. Islam, P. Singh, A. Singha Roy, S. M. Islam,
K. Sen, ACS Omega 2018, 3, 8169.
[21] S. Molaei, T. Tamoradi, M. Ghadermazi, A. Ghorbani-
Choghamarani, Microporous and Mesoporous Mater 2018,
272, 241.
In this paper, we have reported a simple and selective
method for the transformation of a wide variety of alde-
hydes, amines and nitriles into the corresponding 1- and
5-substituted tetrazoles using GO/Fe3O4@PAA-Cu com-
plex as an efficient catalyst. The catalyst was studied from
various aspects including: FTIR, TGA, VSM, FE-SEM,
TEM, XRD, EDX, DLS and ICP analyses. High to excel-
lent yields were obtained for all approaches in various
conditions. It was suggested that aldehyde and oxime
could be transformed to 5-substituted-1H-tetrazoles via a
different milder approach than nitrile. The catalyst bear-
ing α-amino acid polar groups, provide a suitable
medium for the transformation of aldehyde and oxime
through a three-component click chemistry in water. The
recyclability of the catalyst was investigated for six con-
secutive recycles without any remarkable reactivity loss.
Also, an insignificant metal leaching was observed for
the catalyst during recycling. The durability and stability
of the catalyst was studied by some analytical methods
such as FTIR, FE-SEM, TEM and VSM analyses.
[22] P. K. Samanta, R. Biswas, T. Das, M. Nandi, B. Adhikary, R.
M. Richards, P. Biswas, J Porous Mater 2018. In press
[23] B. Salahshournia, H. Hamadi, V. Nobakht, Appl Organomet
Chem 2018, 32, e4416.
[24] X. Yang, X. Zhang, Y. Ma, Y. Huang, Y. Wang, Y. Chen, J
Mater Chem 2009, 19, 2710.
ACKNOWLEDGMENT
[25] M. Keshavarz, A. Zarei Ahmady, L. Vaccaro, M. Kardani, Mol-
ecules 2018, 23, 330.
[26] P. S. Teo, H. N. Lim, N. M. Huang, C. H. Chia, I. Harrison,
Ceram Int 2012, 38, 6411.
[27] S. Ghiami, M. A. Nasseri, A. Allahresani, M. Kazemnejadi,
React Kinet Mech Catal 2019, 126, 383.
[28] M. Kazemnejadi, A. Shakeri, M. Mohammadi, M. Tabefam, J
Iran Chem Soc 2017, 14, 1917.
Authors gratefully acknowledge the financial support of
this work by the Research Council of University of
Birjand.
ORCID
Milad Kazemnejadi https://orcid.org/0000-0002-5424-
9640
[29] M. Kazemnejadi, A. Shakeri, M. Nikookar, R. Shademani,
M. Mohammadi, R Soc Open Sci 2018, 5, 171541.
[30] M. Kazemnejadi, A. Shakeri, M. Nikookar, M. Mohammadi,
M. Esmaeilpour, Res Chem Intermediat 2017, 43, 6889.
[31] W. S. Hummers Jr., R. E. Offeman, J Am Chem Soc 1958, 80,
1339.
[32] X. Sun, Z. Liu, K. Welsher, J. T. Robinson, A. Goodwin,
S. Zaric, H. Dai, Nano Res 2008, 1, 203.
[33] Y. L. Dong, H. G. Zhang, Z. U. Rahman, L. Su, X. J. Chen,
J. Hu, X. G. Chen, Nanoscale 2012, 4, 3969.
[34] J. Shen, Y. Hu, M. Shi, N. Li, H. Ma, M. Ye, J Phys Chem C
2010, 114, 1498.
[35] P. Bilalis, L. A. Tziveleka, S. Varlas, H. Iatrou, Polym Chem
2016, 7, 1475.
[36] H. Tourani, M. R. Naimi-Jamal, M. G. Dekamin, Che-
mistrySelect 2018, 3, 8332.
[37] L. V. Myznikov, S. V. Vorona, T. V. Artamonova, Y.
E. Zevatskii, Russ J Gen Chem 2017, 87, 731.
Mohammad A. Nasseri https://orcid.org/0000-0002-
2371-6680
REFERENCES
[1] D. Varadaraji, S. S. Suban, V. R. Ramasamy, K. Kubendiran, J.
S. K. Raguraman, S. K. Nalilu, H. N. Pati, Org Commun 2010,
3, 45.
[2] M. A. Malik, S. A. Al-Thabaiti, M. A. Malik, Int J Mol Sci 2012,
13, 10880.
[3] B. C. May, A. D. Abell, J. Chem, Soc Perkin Trans 2002,
1(2), 172.
[4] M. L. Kantam, K. S. Kumar, K. P. Raja, J Mol Catal A: Chem
2006, 247, 186.
[5] L. Lang, H. Zhou, M. Xue, X. Wang, Z. Xu, Mater Lett 2013,
106, 443.
[6] L. M. T. Frija, A. Ismael, M. L. S. Cristiano, Molecules 2010, 15,
3757.

MAGNETITE CU COMPLEX OF POLY(α-AMINO ACID) FOR TETRAZOLES SYNTHESIS
15 of 15
[38] A. Rostami-Vartooni, M. Alizadeh, M. Bagherzadeh, Beilstein J
Nanotechnol 2015, 6, 2300.
[39] M. Esmaeilpour, A. R. Sardarian, H. Firouzabadi, Appl
Organomet Chem 2018, 32, e4300.
How to cite this article: Kazemnejadi M,
Mahmoudi B, Sharafi Z, Nasseri MA,
Allahresani A, Esmaeilpour M. Copper
coordinated-poly(α-amino acid) decorated on
magnetite graphene oxide as an efficient
heterogeneous magnetically recoverable catalyst
for the selective synthesis of 5- and 1-substituted
tetrazoles from various sources: A comparative
study. Appl Organometal Chem. 2019;e5273.
https://doi.org/10.1002/aoc.5273
[40] M. Esmaeilpour, J. Javidi, F. N. Dodeji, M. M. Abarghoui, J
Mol Catal A Chem 2014, 393, 18.
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.