Green and efficient Beckmann rearrangement by Cu(II) contained nano-silica triazine based dendrimer in water

Article abstract of DOI:10.1002/jccs.202000469

In this research, a Cu(II) contained nano-silica triazine based dendrimer was prepared, characterized, and utilized as a retrievable catalytic system (Cu(II)-TrDen@nSiO₂) for green formation of primary amides in water at room temperature. The structure of nanoparticles was fully characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetry analysis (TGA). The results revealed that the nanoparticles have spherical morphology and an average size of around 40 nm. The analysis also illustrated that the copper nanoparticles had been successfully loaded on the nitrogen-rich dendritic structure with a uniform distribution. The inductively coupled plasma analysis showed that about 0.67 mmol/g of Cu was loaded on the Cu(II)-TrDen@nSiO₂ support. Mild reaction conditions, excellent yields, environment-friendly synthesis, and easily prepared starting materials are the key features of the present method. The catalyst is easily removed from the reaction media using a simple filtration and can be re-used at least five times without any considerable loss of its catalytic activity.

Full text of DOI:10.1002/jccs.202000469

Received: 22 October 2020
DOI: 10.1002/jccs.202000469
Accepted: 14 December 2020
A R T I C L E
Green and efficient Beckmann rearrangement by Cu(II)
contained nano-silica triazine based dendrimer in water
Mohammad Hasan Bahreininejad | Farid Moeinpour
Department of Chemistry, Bandar Abbas
Abstract
Branch, Islamic Azad University, Bandar
Abbas, Iran
In this research, a Cu(II) contained nano-silica triazine based dendrimer was
prepared, characterized, and utilized as a retrievable catalytic system (Cu(II)-
TrDen@nSiO2) for green formation of primary amides in water at room
temperature. The structure of nanoparticles was fully characterized by using
scanning electron microscopy (SEM), transmission electron microscopy
(TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infra-
red spectroscopy (FT-IR), and thermogravimetry analysis (TGA). The results
revealed that the nanoparticles have spherical morphology and an average size
of around 40 nm. The analysis also illustrated that the copper nanoparticles
had been successfully loaded on the nitrogen-rich dendritic structure with a
uniform distribution. The inductively coupled plasma analysis showed that
about 0.67 mmol/g of Cu was loaded on the Cu(II)-TrDen@nSiO2 support.
Mild reaction conditions, excellent yields, environment-friendly synthesis, and
easily prepared starting materials are the key features of the present method.
The catalyst is easily removed from the reaction media using a simple filtration
and can be re-used at least five times without any considerable loss of its cata-
lytic activity.
Correspondence
Farid Moeinpour, Department of
Chemistry, Bandar Abbas Branch, Islamic
Azad University, Bandar Abbas
7915893144, Iran.
Email: fmoeinpour@iauba.ac.ir
Funding information
Islamic Azad University-Bandar Abbas
Branch
K E Y W O R D S
Beckmann rearrangement, Cu(II) immobilized catalyst, primary amides, triazine based
dendrimer
1 | INTRODUCTION
reactions.[3] Immobilizing the metal-comprising dendri-
mers on solid supports has practicable significance in the
Dendrimeric compounds are a new type of polymeric
materials with branches that all originate from one
nucleus and are described as macromolecules with a
three-dimensional branch structure. The synthesis and
characteristics have pointed out over the past years.[1] As
a consequence of their three-dimensional framework and
multiplex inner and outer functional groups, dendrimers
could be operating in a selective manner as proper hosts
for a large variety of ions and molecules.[2] Dendrimers
with metal ions combined into their core or on their sur-
face have discovered excellent usages in catalytic
catalytic scope due to their comfortable recovery capacity
and reutilization, along with their eco-friendly nature.
Due to these benefits, heterogeneous dendrimer-based
catalysts have been effectively used in several significant
organic reactions.[4] Among dendritic molecules, triazine-
based dendrimers have received much attention due to
the cost-effective and selective reactivity of the cyanuric
chloride as the relevant parent material.[5] Therefore, for
a great variety of catalytic usages, different generations of
triazine-based dendrimers could be synthesized by way of
a step by step functionalization.[6] The Beckmann
J Chin Chem Soc. 2021;1–9.
http://www.jccs.wiley-vch.de
© 2021 The Chemical Society Located in Taipei & Wiley-VCH GmbH
1

2
BAHREININEJAD AND MOEINPOUR
rearrangement is a typical pathway for the preparation of
amides by means of ketoximes or aldoximes.[7] This reac-
tion gives an easy route for the synthesis of ε-caprolac-
tam, which is a crucial intermediate in the fabricate of
resins and fibers.[8] The reaction was performed by
diverse procedures and catalysts.[9] Lately, the utilization
of metals is a desirable approach to attain primary amide
conversions.[10] Numerous catalysts such as Au/TiO2,[11]
CuO – ZnO/C,[12] KMnO4/NH3(l),[13] CuSO4Á5H2O,[14]
ZnCl2/K2CO3,[15] Al2O3/MeSO2Cl,[16] Cu2O,[17] RuCl
(PPh3)3,[18] CuCl2,[19] ZnO,[20] and Co(II)-porphyrin/
graphene oxide[21] have been utilized for primary amide
synthesis from aldoximes. In many cases, some of the
above methods at least suffer from problems such as high
catalyst loading, laborious reaction conditions, difficult
separation of catalyst or product from the reaction mix-
ture, time-consuming reaction protocol, and the manipu-
lation of costly and dangerous solvents and catalysts.
Accordingly, to overcome these limitations, the use of
high stability and catalytic efficiency, low cost and toxic-
ity, easy synthesis, and fast versatile surface func-
tionalization has expanded in recent years. In the wake
of our efforts in nano-catalysts synthesis,[22] in the pre-
sent report, the manufacturing of Cu(II)@ nano-silica
functionalized triazine dendrimer (Cu(II)-TrDen@nSiO2)
as an efficient catalytic system is discussed. Upon full
identification of catalyst structure, the catalyst has been
applied for the synthesis of various primary amides
through Beckmann rearrangement. The general reaction
is depicted in Scheme 1.
atoms in cyanuric chloride to provide CC1-nSiO2, which
then reacted with bis(3-aminopropyl)amine to produce
first generation (G1). The similar method was
implemented to raise the dendrimer generation,
CC2-nSiO2, and second-generation, G2 (Scheme 2). The
NH2 moieties on external margin of second generation-
dendrimer (G2) are proper to coordination with Cu(II).
Examination of the nano catalyst structure has been done
using FT-IR spectroscopy, TGA, TEM, SEM, EDX, and
ICP spectroscopy. The chemical structure of copper(II)
contained nano-dendrimers is confirmed by FT-IR spec-
troscopy. The FT-IR spectra of dendritic molecules is illus-
trated in various synthetic steps in Figure 1. The wide
peaks at 3,200–3,400 and 1,000–1,100 cm−1 are designated
to the hydroxyl (O-H) and Si-O-Si bonds in AmPr-nSiO2,
respectively (Figure 1a).[23] Furthermore, the specific
bands for aliphatic C-H bond emerge at around 1,481 and
2,992 cm−1. In the Fourier transform infrared spectra of
CC1-nSiO2, G1 and G2 (Figure 1b–d), apart from the afore-
mentioned
vibrations,
the
bands
located
at
1,580–1,603 cm−1 (C=N) is a worthy evidence for the exis-
tence of triazine segment on the surface of nano-SiO2.
TGA is a thermal decomposition method that
operates over time as the sample mass changes with tem-
perature change. Factors such as dehydration, drying,
desorption, dissolution, thermal degradation, and solid–
solid reactions lead to weight loss of the sample. TGA
plots of AmPr-nSiO2 and G2 and two-step thermal
decomposition are depicted in Figure 2. In the first stage,
the main weight reduction is referred to the physical
removal of water and in the second stage due to the loss
of organic parts on the surface.
2 | RESULTS AND DISCUSSION
The morphological structure of the surface of TrDen-
nSiO2 and Cu(II)-TrDen@nSiO2 was investigated by
SEM. (Figure 3a,b). The morphologic structure and size
of TrDen-nSiO2 and Cu(II)-TrDen@nSiO2 could be
expressively seen from SEM pictures. As evidenced, the
Cu(II)-TrDen@nSiO2 particles are globular. The EDX
outcomes, received from SEM study of TrDen-nSiO2 and
Cu(II)-TrDen@nSiO2, are displayed in Figure 3c,d,
respectively. Their collation indicates that Cu(II) has
been inserted into the TrDen-nSiO2 (Figure 3d).
The TEM images were used to explore the morphol-
ogy and size of the nano catalyst (Figure 4). It is dis-
played that the dimmer area in Cu(II)-TrDen@nSiO2
image, is related to Cu(II) whereas the uncolored parts
are silica, this is caused by the greater electron density of
Cu(II) in comparison to nano-silica.[25] In addition, the
TEM image of the nano catalyst depicts that the average
nanoparticles size is around 40 nm.
Scheme 2 depicts the synthetic procedure for Cu(II)-
TrDen@nSiO2 nanoparticles in accord with literature.[23]
In order to formation of Cu(II)-TrDen@nSiO2, nano-sil-
ica, which was activated by HCl was reacted with APTES
(3-aminopropyltriethoxysilane) in accord with the litera-
ture[24] to prepare the aminopropylated nano-silica
(AmPr-nSiO2) required for growth of dendrimer mole-
cules. Reacting of CC (cyanuric chloride) with
aminopropylated nano-silica (AmPr-nSiO2) was per-
formed at ambient temperature to replace one of the Cl
The concentration of copper in Cu(II)-TrDen@nSiO2
was 0.67 mmol/g, which was determined using induc-
tively coupled plasma analysis.
SCHEME 1 Overall reaction for the synthesis of primary
benzamides

BAHREININEJAD AND MOEINPOUR
3
SCHEME 2 Synthetic manner for the Cu(II)-TrDen@nSiO2
(Table 1). The findings depicted that the reaction did
not proceed without nano-catalyst in some non-polar
and polar solvents and solvent-less state, even after
24 hr (entries 1–7). When there is nano-catalyst, the
prime outcomes were attained in water and EtOH
(entries 8–15). Enhancement of the nano-catalyst load-
ing to 0.1 g improved the reaction efficacy (entries
15–16). Increasing the amount of catalyst more than this
did not increase the efficiency of the reaction (entry 17).
In conclusion, the highest performance was attained
when the sample reaction was carried out in H2O with
0.1 g of nano-catalyst at ambient temperature (entry 16).
To illustrate the function of copper in the reaction pro-
gression, the operation of other parts of the nano-
catalyst like nSiO2 and TrDen@nSiO2 was also checked
under optimal conditions. The findings are depicted in
Table 1 (entries 18–20). As one can see, no proceeding
was observed in the sample reaction when applying the
other parts of nano-catalyst in the lack of copper, con-
firming that the copper existing is indispensable for the
reaction. In addition, the sample reaction was con-
ducted by Cu(OAc)2 (copper acetate) for 1 hr at opti-
mized conditions, 4-chlorobenzamide was achieved in
25% yield (entry 20). The finding displays that Cu(OAc)2
FIGURE 1 FT-IR spectrum of: (a) AmPr-nSiO2, (b) CC1-nSiO2,
(c) G1, and (d) G2
With the nano catalyst in hands, attention was
focused on its catalytic activity in the synthesis of pri-
mary amides through Beckmann rearrangement. To
achieve this goal, the 4-chlorobenzaldoxime was
selected as a model to investigate substrate the effect of
solvent polarity and reaction temperature on the yield
and time of reaction. In the initial phase, we conducted
the above Beckmann rearrangement in the absence and
presence of varied loadings of the nano-catalyst

4
BAHREININEJAD AND MOEINPOUR
FIGURE 2 TGA plot of: (a) AmPr-nSiO2 and (b) G2
FIGURE 3 SEM images of: (a) TrDen-nSiO2, (b) Cu(II)-TrDen@nSiO2. EDX spectrum of: (c) TrDen-nSiO2 and (d) Cu(II)-TrDen@nSiO2
showed insignificant function under optimized condi-
tions, compared to Cu(II)-TrDen@nSiO2.
To investigate the generality of the reaction in the
presence of the nano catalyst, we studied the reaction
of other kinds of reactants. The results shown in
Table 2, indicate that the electronic nature of the
substituents on the aromatic aldoximes had no obvi-
ous influence on the ultimate effectiveness of the
reaction and all corresponding products were
obtained in good to excellent yields. All synthesized
products were known compounds and were recog-
nized by comparing spectroscopic data (1H-NMR and

BAHREININEJAD AND MOEINPOUR
5
FT-IR) and their melting points with those reported
in the literature.
aldoxime. In the second stage, Cu – nitrile intermediate
reacts rapidly with another aldoxime molecule and
finally, a nitrile molecule has been removed to produce
desirable primary amide.
Reproducibility of the catalyst was examined by
implementing repetitive courses of the model reaction on
the same batch of the nano catalyst. For the purpose of
restoring the catalyst, after each run, it was isolated by
filtration, washed with EtOAc (ethyl acetate), desiccated,
and reused in the next course. The findings indicate that
the catalyst can be retrieved five courses without any
notable failure in catalytic operation (Figure 5).
In line with literature,[32] a probable mechanism for
the primary amides synthesis by Cu(II)-TrDen@nSiO2 is
indicated in Scheme 3. At first, aldoxime is coordinated
to Cu of the nano-catalyst. This interaction facilitates the
copper-nitrile complex formation by dehydration of
To investigate the copper leakage, ICP examination of
the regenerated nano catalyst was also conducted. In line
with the achieved data, no appreciable abatement was
observed in the Cu concentration. The Cu loading in the
freshly prepared nano catalyst and the recycled one was 0.67
and 0.64 mmol/g, respectively, which disclosed the dosage
of leaked Cu for this nano catalyst is negligible. The
retrieved sample was also identified by using TEM analysis,
which confirmed that no structural alterations were detected
on the recycled catalyst (Figure 6). The hot filtration test
was carried out for the analysis of heterogeneous character
FIGURE 4 TEM image of synthesized nano-catalyst (Cu(II)-
TrDen@nSiO2)
TABLE 1 Optimization of solvent, temperature, and nano-catalyst dosagea
Entry
1
Condition
Catalyst (g)
—
Temp. (ꢀC)
Time (hr)
Yieldb (%)
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Trace
15
Toluene
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
70
rt
rt
rt
rt
rt
rt
rt
rt
24
24
24
24
24
24
24
5
2
CH2Cl2
—
3
EtOH
—
4
n-hexane
—
5
CH3CN
—
6
Solvent-free
—
7
H2O
—
8
Toluene (cu(II)-TD@ nSiO2)
n-hexane(cu(II)-TD@nSiO2)
CH3CN (cu(II)-TD@ nSiO2)
Solvent-free(cu(II)-TD@nSiO2)
Solvent-free (cu(II)-TD@ nSiO2)
CH2Cl2 (cu(II)-TD@ nSiO2)
EtOH (cu(II)-TD@ nSiO2)
H2O (cu(II)-TD@ nSiO2)
H2O (cu(II)-TD@ nSiO2)
H2O (cu(II)-TD@ nSiO2)
H2O (nSiO2)
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.10
0.15
0.10
0.10
0.10
9
5
10
11
12
13
14
15
16
17
18
19
20
5
5
Trace
20
5
5
Trace
30
5
5
60
0.6
0.6
1.0
1.0
1.0
98
98
None
None
25
H2O (TD@nSiO2)
H2O (cu(OAc)2)
aReaction conditions: 4-chlorobenzaldoxime (1.0 mmol), catalyst (0.05–0.15 g), and water.
bIsolated yields.

6
BAHREININEJAD AND MOEINPOUR
TABLE 2 Synthesis of primary benzamides derivatives in the presence of catalysta
Time
(hr)
Yieldb
(%)
1H NMR, δc
CONH (lit.)
Entry Ar
M.P. (ꢀC) (lit.)
IR (KBr) (lit.)
1
C6H5
0.50
0.60
0.67
0.60
0.60
1.00
0.50
0.65
0.90
0.80
0.75
1.00
1.00
96
98
95
95
92
95
98
91
93
90
94
91
95
97
126–127 (128–130)[26] 3,342, 3,169 (NH2), 1,670 (C=O) (3,343,
6.24 (6.26)[27]
6.97 (7.5)[29]
8.00 (7.80)[27]
8.12 (8.00)[21]
6.50 (7.51)[29]
6.61 (6.51)[27]
8.20 (8.25)[21]
7.55 (7.50)[32]
6.45 (7.01)[29]
6.21 (7.01)[20]
7.61 (7.62)[21]
6.5 (7.60)[20]
7.20 (6.61)[20]
8.00 (7.91)[32]
3,168, 1,671)[27]
2
4-ClC6H4
171–172 (175–178)[28] 3,334, 3,225 (NH2), 1,662
(C=O) (3,333, 3,226, 1,667)[29]
3
4-BrC6H4
191–192 (191–192)[30] 3,364, 3,174 (NH2), 1,656 (C=O) (3,360,
3,170, 1,660)[27]
4
4-NO2C6H4
4-MeC6H4
2-ClC6H4
199–200 (198–200)[31] 3,418, 3,316 (NH2), 1,662 (C=O) (3,400,
3,310, 1,660)[21]
5
153–157 (154–156)[12] 3,343, 3,166 (NH2), 1,670 (C=O) (3,343,
3,168, 1,671)[27]
6
138–140 (139–141)[28] 3,360, 3,179 (NH2), 1,651 (C=O) (3,340,
3,140, 1,640)[27]
7
4-CNC6H4
4-OMeC6H4
3-OHC6H4
2-OHC6H4
3,4-(cl)2C6H3
3-ClC6H4
221–223 (222–224)[13] 3,443, 3,174 (NH2), 1,700 (C=O), (3,444,
3,175, 1,700)[32]
8
163–165 (165–167)[28] 3,391, 3,169 (NH2), 1,647 (C=O) (3,390,
3,160, 1,650)[32]
9
169–171 (170–171)[16] 3,402, 3,245(NH2), 1,652 (C=O) (3,361,
3,182, 1,550)[29]
10
11
12
13
14
138–140 (140–142)[20] 3,422,3,215 (NH2), 1,688
(C=O) (3,397, 3,191, 1,653)[20]
137–139 (138–139)[32] 3,358, 3,170 (NH2), 1,657 (C=O) (3,350,
3,160, 1,660)[21]
131–132 (132–134)[28] 3,354, 3,173 (NH2), 1,659 (C=O) (3,361,
3,182, 1,550)[20]
3-MeC6H4
93–94 (94–95)[30]
3,342, 3,165 (NH2), 1,669 (C=O) (3,377,
3,197, 1,651)[20]
2-Thiophenyl 1.10
140–141 (140–142)[32] 3,360, 3,171 (NH2), 1,650 (C=O) (3,364,
3,173, 1,651)[32]
aReaction conditions: aldoxime (1 mmol), catalyst (0.1 g), water (10 ml) at room temperature.
bIsolated yields.
cSolvent: DMSO - d6 – TMS.
SCHEME 3 A plausible catalytic
mechanism for the preparation of primary
amides
of Cu(II)-TrDen@nSiO2 catalyst under optimized conditions.
Therefore, a mixture of Cu(II)-TrDen@nSiO2 (100 mg),
4-chlorobenzaldoxime (1 mmol), and H2O (10 ml) was
stirred at ambient temperature for 18 min. After around 50%
product formation, the Cu(II)-TrDen@nSiO2 catalyst was
removed from the reaction mixture and afterward the

BAHREININEJAD AND MOEINPOUR
7
reaction was proceeded without catalyst for another 18 min.
The insignificant final product was found which was con-
trolled by thin layer chromatography (TLC). These
consequences confirmed that the reaction really catalyzed
on surface active sites of Cu(II)-TrDen@nSiO2.
To corroborate the privilege of this project, utilization of
Cu(II)-TrDen@nSiO2 in producing of 4-chlorobenzamide
toward other early recorded catalysts are given in Table 3.
In conformity with the findings, the presented catalyst dis-
plays more convenient performance under environmental
friendliness and economic conditions.
3 | EXPERIMENTAL
3.1 | General information
All materials and solvents were acquired from Sigma.
Aldoximes were synthesized according to literature.[32] The
morphology of the nano catalyst was investigated with trans-
mission electron microscopy using a LEO 912AB (120 kV)
instrument. IR spectra were taken on a Nicolet spectrometer
(Magna 550) in the films on KBr pellets. Scanning electron
microscopy (SEM) picture was taken by MIRA III, TESCAN.
The energy dispersive X-ray (EDX) was performed with
133 eV resolution (model 7,353, Oxford Instruments, UK).
TGA analysis was performed under a nitrogen atmosphere
with a Netzsch-TGA 209 F1 thermogravimetric analyzer.
Inductively coupled plasma analysis (ICP) was used to deter-
mine the amount of Cu loaded on the support by a Varian
VISTA-PRO. A Bruker (DRX-300Avance) NMR was used to
FIGURE 5 Reutilization of the catalyst for the sample reaction
1
record the H NMR spectra in DMSO-d6 at room tempera-
ture. The melting points measurement was performed on an
Electrothermal Type 9100 device.
3.2 | Aminopropylated nano-silica
(AmPr-nSiO2) preparation method
A total of 10 g of mesoporous silica powder was poured
into a beaker and 6 M HCl solution (80 ml) was added,
FIGURE 6 TEM image of retrieved nano-catalyst (Cu(II)-
TrDen@nSiO2)
TABLE 3 Comparability of Cu(II)-TrDen@nSiO2 nano-catalyst with different heterogeneous catalytic systems in preparation of
4-chlorobenzamide
Entry
Catalyst
Solvent
H2O
Temp. (ꢀC)
Time (min)
Yield (%)a
Ref.
[33]
1
2
3
4
5
6
7
Cu(II)/metformin/graphene oxide
Fe3O4@SiO2-Lig-cu
ZnO
100
80
45
60
96
95
86
90
88
97
98
PEG
[32]
Solvent-free
Toluene
Heptane
H2O
140
80
60
[20]
GO-CoPPh
100
1,080
10
[21]
ZnCl2
100
110
RT
[34]
Ru complex
[35]
Cu(II)-TrDen@nSiO2
H2O
36
This study
aIsolated yields.

8
BAHREININEJAD AND MOEINPOUR
when completely dissolved, transferred to a round bot-
tom balloon, and refluxed at 120ꢀC for 24 hr. Afterward
the solution was filtered and neutralized with distilled
water. The precipitate was then dried at 50ꢀC. After that,
3 g of activated nano-silica powder was refluxed with
8 ml of 3-APTES in dry toluene for 7 hr. Then, the
reacting mixture was separated by filtration and the
resultant material was extracted by toluene by Soxhelet
system and vacuum dried at 110ꢀC.[24,36]
dried to be ready to react again. Then the reaction
mixture was extracted with ethyl acetate (3 × 10 ml).
The combined organic layers were dried over Na2SO4
and the solvent was evaporated under reduced pressure.
The desired primary benzamide was recrystallized in
ethanol.
4 | CONCLUSIONS
We have effectually prepared a copper comprised triazine
based dendritic catalyst as a very consistent and retriev-
able nano catalyst for the proficient preparation of pri-
mary amides through Beckman rearrangement in water
at room temperature. The presented reaction, in which
the prepared Cu(II)-TrDen@nSiO2 as a retrievable cata-
lyst, in line with the philosophy of green chemistry by
reason of the following features: low toxic effect, facile
catalyst preparation, high lifetime, reproducibility, short-
ened times, and excellent yields. Above them all, the cat-
alyst could be retrieved five times without any notable
decrement in its efficiency. Hence, it could be advanta-
geous in relevant industries.
3.3 | Triazine dendritic polymer
immobilized on nano-silica (TrDen@nSiO2
or G2) synthetic procedure
At this stage, 1.85 g cyanuric chloride, then 1.7 ml of
diisopropyl ethylamine (DIPEA) were added to 10 ml tet-
rahydrofuran. Then 2 g of the powder of the preceding
step (AmPr-nSiO2) was added to this solution and agi-
tated on a night at ambient temperature. The resultant
solid (CC1-nSiO2) was filtered off and rinsed with hot tet-
rahydrofuran, extracted by Soxhelet apparatus, and vac-
uum dried at 50ꢀC.[23] Afterward, 1 g of the powder
obtained in the previous step (CC1-nSiO2) was added to
a solution of 15 ml DMF, 1 ml bis(3-aminopropylamine),
and 1.4 ml DIPEA. The resultant mixture was agitated
for 16 hr at 80ꢀC. Afterward, the derived precipitate
(G1) was filtered, rinsed with boiling C2H5OH in
soxhelet, and afterward desiccated at 55ꢀC. The G2 was
made in accordance with the aforementioned method for
the synthesis of first generation.[37]
ACKNOWLEDGMENTS
This work is financially assisted by the Islamic Azad
University-Bandar Abbas Branch. The authors are grate-
ful for that.
ORCID
Farid Moeinpour https://orcid.org/0000-0003-2380-
993X
3.4 | Synthesis of Cu(II)-TrDen@nSiO2
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How to cite this article: Bahreininejad MH,
Moeinpour F. Green and efficient Beckmann
rearrangement by Cu(II) contained nano-silica
triazine based dendrimer in water. J Chin Chem
Soc. 2021;1–9. https://doi.org/10.1002/jccs.
202000469