Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the Multicomponent and Click Synthesis of 1,4-Disubstituted 1,2,3-Triazoles via Huisgen 1,3-Dipolar Cycloaddition

Article abstract of DOI:10.1007/s10562-021-03772-9

In this paper, we report a novel magnetically separable silica coated copper nano-magnetite NHC-benzimi@Cu complex as heterogeneous catalyst for the multicomponent click reaction via Huisgen 1,3-dipolar cycloaddition reaction of alkyl or aryl halide, sodi

Full text of DOI:10.1007/s10562-021-03772-9

Catalysis Letters
https://doi.org/10.1007/s10562-021-03772-9
Supported NHC‑Benzimi@Cu Complex as a Magnetically Separable
and Reusable Catalyst for the Multicomponent and Click Synthesis
of 1,4‑Disubstituted 1,2,3‑Triazoles via Huisgen 1,3‑Dipolar
Cycloaddition
Arvind Pawar1,3 · Shivanand Gajare2 · Ashutosh Jagdale1 · Sandip Patil1 · Wilson Chandane2 · Gajanan Rashinkar2 ·
Suresh Patil1
Received: 15 June 2021 / Accepted: 10 August 2021
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2021
Abstract
In this paper, we report a novel magnetically separable silica coated copper nano-magnetite NHC-benzimi@Cu complex as
heterogeneous catalyst for the multicomponent click reaction via Huisgen 1,3-dipolar cycloaddition reaction of alkyl or aryl
halide, sodium azide and terminal alkyne, which afords various1,4-disubstituted 1,2,3-triazoles. The multistep prepared
nano catalyst has been characterized by various spectroscopic methods such as FT-IR, TGA, EDX, XRD, TEM and VSM.
The heterogeneous nano catalyst structures coated on the copper surface are responsible for the excellent catalyst perfor-
mances in the reaction. The reusability of the catalyst makes the present protocol more fascinating from an environmental
and economic point of view.
Graphic Abstract
Keywords Magnetically retrievable nanocatalyst · Click reaction · Copper iodide · 1,2,3-triazoles · Reusability
Extended author information available on the last page of the article
Vol.:(0123456789)
1 3

A. Pawar et al.
their capacity to impact diferent C–C, C–N and C–O bond
developments in multicomponent reactions.
1 Introduction
In addition they have remarkable properties such as high
activity and selectivity with increased stability towards air
and moisture, superior catalytic activities, ability to form
stable metal complexes, adjustment of electronic and steric
parameters, ease of access to their azolium salt precursors
and tailor made performance for specifc catalytic reactions
[22–24]. In spite of these properties NHC-TM complexes
have revealed the problem of contamination and recycling of
catalyst during organic transformation due to their homoge-
neous nature [25]. To overcome these problems by replacing
homogeneous NHC-complexes with heterogeneous NHC-
complexes with high area support material this gives realm
from environmental pollution and economically favorable
[26]. Numbers of supporting materials have been reported
with NHC-metal complexes for variety of catalytic reaction
in the organic synthesis [27–29]. However, despite tremen-
dous advances, there is considerable scope for the further
development especially by using magnetic nanoparticles
(MNPs) as a support in order to conclude the aim of sus-
tainable and environmentally benign processes.
In recent scenario, the design of a process that minimizes
the use, the generation of hazardous substance and reduces
environmental impact is a very essential goal in chemistry.
The use of benign solvents (e.g. water and ionic liquids) and
highly efcient, economic and recoverable catalyst with null
toxicity is essential. A signifcant improvement in catalytic
activity can be achieved by synthesizing a nano metal cata-
lyst [1, 2]. In spite of having advantages such as enhanced
activity and cost efectiveness, most of the times the separa-
tion of nano catalyst becomes valuable due to need of fltra-
tion, solvent fltration or centrifugation of the fnal reaction
mixture. In many cases, product and catalyst are insoluble
in same solvent, which leads to complexity in work-up. To
overcome this problem metal nano particles have been ef-
ciently employed as catalyst in order to recover them by
external magnet [3].
Magnetic nano particles usually consist of core shell
structure of iron oxide these prevents the aggregation. For
this purpose silica is used because of its stability and cata-
lyst functionalized very easily (applied chemistry Nadar
ma). From last decade the synthesis of 1,2,3-trizoles has
been great interest due to their multifarious applications in
pharmaceutical, agrochemicals, corrosion inhibiters etc. [4].
They are found to exhibit wide range of bioactivities such
as antiviral [5], anti HIV activity [6], anti-microbial activ-
ity [7].Triazole bridged dendrimers have also been success-
fully applied as photosensitizer in dye sensitized solar cells
(DSSC’s) [8] also in various important chemical processes
[9]. They have also been evaluated as a novel type of acetyl
cholinesterase inhibitors to cure Alzheimer’s disease [10],
to synthesize potential biological agents [11] as well as to
develop anticancer drugs [12].
MNPs have captivated their attention in the feld of catal-
ysis due to their technology and chemical application [30,
31]. In recent years, eforts of the scientifc community have
been directed towards the synthesis of superparamagnetic
nanoparticles for the design of magnetically retrievable
nanocatalytic systems owing to their exceptional physico-
chemical properties and rapid response to the applied mag-
netic feld. Amongst, Fe3O4 MNPs are robust, inexpensive,
easy to prepare, non-toxic, magnetically recoverable and can
be reused multiple times for several reaction cycles. Con-
sequently, they have emerged as the viable alternatives to
existing solid-supported heterogeneous catalysts [32]. In
addition, their high surface region, superparamagnetism,
simple surface change by appropriate functionalities and
facile retrievability by external magnet has added demand-
ing adaptability for such materials in task explicit catalytic
systems [33, 34]. Owing to these properties, they are widely
used in synthetic chemistry [35]. Despite remarkable pro-
gress, research toward applications of Fe3O4 MNPs in the
synthesis of magnetically retrievable NHCs is still in its
infancy and therefore warrants immediate attention.
Herein, we report a simple and efcient synthesis of a
nano-ferrite-supported, magnetically recyclable, inexpen-
sive Cu catalyst and its application in Huisgen 1,3-dipolar
cycloaddition reaction to synthesize 1,2,3-triazoles via one
of the dominant click reaction.
From the last decades, N-heterocyclic carbenes (NHCs)
have been attracted to researchers as powerful weapon
as ligand in organic chemistry and transition metal (TM)
catalysis with beyond number of applications in commer-
cially important processes [13–16]. NHCs are easily avail-
able, coordinative unsaturation, electron–rich and typical
σ–donors, moderate π–acceptors, which sterically request-
ing structure for complexation with the transition metals.
A huge nature of NHC‐TM structure is their unremarkable
unfaltering quality that is habitually referred to as one of the
fundamental advances of these ligands over their phosphine
accomplices [17–21]. They are a malleable class of sub-
ordinate ligands that have gathered huge consideration for
Based on aforementioned discussion and in continuation
of our studies related to heterogeneous catalysis and multi-
component reaction [36–40], we report herein preparation of
magnetic separable nanoparticles decorated N-heterocyclic
carbene complex with copper and its application in the syn-
thesis of 1,4-disubstituted 1,2,3-trizoles (Scheme 1).
1 3

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the…
Scheme 1 Synthesis of 1,4-disubstituted 1,2,3-triazoles by using nano-magnetite NHC-benzimi@Cu (6)
for 1 h. The black nano magnetite was separated magneti-
2 Experimental
cally from the aqueous solution and were washed with etha-
nol and dried in an oven at 60 °C. In order to synthesize
silica-coated withnano magnetite, nano magnetite (1.0 g)
were initially dispersed in 80 mL 4:1 ethanol/water solution
and the pH=10 of the solution was adjusted by addition of
conc. ammonium hydroxide (12 ml).
2.1 General Remarks
All reactions are carried out under air atmosphere in dried
glassware conditions. FT‐IR data spectra are measured with
a Perkin-Elmer one FT‐IR spectrophotometer. The samples
were examined as KBr discs (~5% w/w). The thermogravi-
metric analysis (TGA) curves were obtained using instru-
ment SDT Q600 V20.9 Build 20 in the presence of static
air at linear heating rate of 10 °C min−1 from 25 to 1000 °C.
Elemental analyses were carried out in a Perkin-Elmer 2400,
Series II, CHNS/O analyzer and using an energy‐disper-
sive X‐ray spectroscopic facility (Hitachi S 4800, Japan).
Raman spectroscopy is done by using a Bruker: RFS 27
spectrometer.1H NMR and 13C NMR spectra were recorded
with a Bruker Avance (300 MHz for 1H NMR and 75 MHz
for 13C NMR) spectrometer using CDCl3 solvent and tetra-
methylsilane as an internal standard. The chemical shifts
were denoted in parts per million (ppm) and coupling con-
stants are denoted in hertz (Hz). Mass spectra are recorded
with a Shimadzu QP2010 gas chromatography-mass spec-
trometry (GC–MS). X-ray powder difraction (XRD) was
taken by using a Bruker D2 Phaser. Magnetic measurements
were performed on Lakeshore magnetometer, USA, Model
7407. The materials are considered by using a PHILIPS CM
200 model with 20–200 kV accelerating voltages. Melting
points are determined using MEL‐TEMP capillary melting
point apparatus and are uncorrected. Fe3O4 MNPs (1) [41],
silica coated Fe3O4 MNPs (2) [42] and all other chemicals
were obtained from local suppliers and used without further
purifcation.
Then, 0.5 mL tetraethylorthosilicate (TEOS) was added
subsequently. The mixture was stirred vigorously at 40 °C
for 12 h. The resultant product was washed three times
with ethanol and dried in a vacuum. A mixture of silica
coated nano magnetite (2) (10 g) and (3-chloropropyl) tri-
ethoxysilane (20 mL, 100 mmol) in dry xylene (100 mL)
was refuxed in an oil bath. After 24 h, the reaction mixture
was cooled, product was isolated by magnetic separation
and washed with xylene (4×25 mL), methanol (4×25 mL),
deionised water (4 × 25 mL) and dried under a vacuum at
60 °C and for 12 h to aford 3-chloropropyl modifed nano
magnetite (3). FTIR (KBr, thin flm): υ=3408, 2925, 1099,
797, 699, 633, 583 cm−1.
2.3 Preparation of [Nano‑Magnetite‑Benzimi]Cl (5)
A mixture of 3 (10.0 g) and benzimidazole (4) (6 g,
18 mmol) in dimethylformamide (50 mL) was heated at
80 °C in an oil bath. After 72 h, the solid was separated
by magnet, washed with MeOH and CH2Cl2 and dried
under vacuum at 50 °C for 24 h to obtain [Nano magnetite-
benzimi]Cl (5).IR (KBr, thin flm): υ= 3428, 2925, 2860,
1654, 1642, 1457, 1387, 1093, 585 cm−1. CHNS elemental
analysis observed: %C 13.42, %H 0.36, % N 4.78. Loading
of 0.36 mmol functional group per gram of 5 (Scheme 2).
2.4 Preparation of Nano‑Magnetite NHC‑Benzimi@
Cu (6)
2.2 Preparation of 3‑Chloropropyl Modifed Nano
Magnetite (3)
A mixture of 5 (10.0 g), copper iodide (1.9 g, 10 mmol) and
NaOtBu (0.096 g, 10 mmol) in THF (50 mL) was heated at
100 °C in an oil bath for 6 h. Afterwards, the mixture was
separated by magnet. Washed with the THF and dried under
vacuum at 50 °C for 24 h to obtain nano-magnetite NHC-
benzimi@Cu (6). FT‐IR (KBr, thin flm): υ =3406, 2893,
Magneticnano magnetitewere synthesized by co-precipita-
tion method briefy, a mixture of FeCl3.6H2O (10 mmol)
and FeCl2.4H2O (5 mmol) salts were dissolved in 200 mL
water An aqueous ammonia solution (28% w/w, 30 mL) was
added until the pH=11. The resulting black dispersion was
mixed vigorously for 1 h at room temperature and refuxed
1 3

A. Pawar et al.
2828, 1632, 1444, 1320, 1075, 586 cm−1; Elemental analysis
observed: %C 13.42, % O 45.51, % Fe 14.30, % Si 19.25, %
N 4.78, % Cu 1.41, % I 0.97.
2.5 General Method for Synthesis
of 1,4‑Disubstituted 1,2,3‑Triazoles
In a 50 mL round bottom fask alkyl/aryl halide (1.0 mmol),
sodium azide (1.1 mmol), alkyne (1.0 mmol), nano-mag-
netite NHC-benzimi@Cu (6) (40 mg) was added to above
solution and stirred in 5 mL ethanol at 80 °C. The reaction
was monitored by thin layer chromatography (TLC) using
aluminium backed silica gel 60 (F254) plates. The comple-
tion of the reaction, the catalyst was separated magnetically
using bar magnet. Finally, the solid obtained was extracted
with ethyl acetate and dried over anhydrous Na2SO4 the sol-
vent was removed under reduced pressure then the product
was purifed by silica gel column chromatography.
3 Results and Discussion
The preparation of nano-magnetite complex with copper is
outlined in (Scheme 1). Initially, nano magnetite (1) was
synthesized by co-precipitations method and coated with
silica layer by using TEOS (tetraethyl ortho silicate) aforded
silica coated nano magnetite (2) through sol–gel method [41,
42] which on further treatment with (3‐chloropropyl)trieth-
oxysilane aforded 3-chloropropyl modifed nano magnet-
ite (3). The synthetically fertile chloro group in 3 allowed
attachment of ionic liquid like group on the surface of nano
magnetite through quaternization with benzimidazole (4) to
yield azolium salt precursor acronymed as [nano-magnetite-
benzimi] Cl (5). Finally, the complexation of 5 with copper
iodide by using NaOtBu as base aforded nano-magnetite
NHC-benzimi@Cu (6).
Fourier transform infrared (FT‐IR) spectroscopy was
employed to monitor reactions involved in the preparation of
nano-magnetite NHC-benzimi@Cu (6). The FT-IR spectrum
of nano magnetite (1) displayed Fe–O stretching band at
583 cm−1.The formation of silica coated nano magnetite (2)
was confrmed by FT-IR peaks at 796, 959 and 1099 cm−1
attributed to Si–O–Si symmetric, Si–O symmetric and
Si–O–Si asymmetric stretching modes respectively [43].
Scheme 2 Preparation of nano-magnetite NHC-benzimi@Cu (6)
1 3

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the…
prominent peaks at 1654 cm−1 (C=N stretching vibration),
1642 cm−1(C=C stretching vibration) and 1387 cm−1 (C–N
stretching) suggesting the formation of 5 (Fig. 1d) [45].
Finally, the formation of 6 was confrmed by a strong
intense band of N–C–N strengthening in the range
1340–1500 cm−1 as a result coordination of NHC carbon
ligand with copper metal ion as well as shifting of the char-
acteristic IR absorption peaks to lower frequency values
(Fig. 1e) [46, 47].
The thermal stability profles of bare nano magnetite
(1) and nano-magnetite NHC-benzimi@Cu (6) were inves-
tigated by TGA analysis over the temperature range of
25–1000 °C at a heating rate of 10 °C min−1. (Fig. 2). In
both cases, initial weight loss of 3.68% up to 102 °C and
4.96% up to 111 °C respectively for 1 and 6 is due to evapo-
ration of physically adsorbed water. TGA curve of bare nano
magnetite (1) displayed no signifcant weight loss from 111
to 800 °C which indicates that presence of only iron oxides
and no any organic moiety attached on the surface of nano
magnetite. In TGA curve of 6, the second weight loss was
observed 8.79% in the range of 102–502 °C attributed to loss
of surface bound organic scafolds by thermal decomposition
such as (3-chrolopropyl) triethoxy silane and benzimidazole.
The steep weight loss of 15.67% at 700 °C displayed ther-
mal decomposition of copper iodide and major weight loss
ascribed to residual silica and metallic oxides which possess
high thermal stability.
Fig. 1 FT-IR spectra of (c) 3-Chloropropyl modifed MNPs (3); (d)
[Nano-magnetite-benzimi]Cl(5); (e) nano-magnetite NHC-benzimi@
Cu (6); (f) Reusednano-magnetite NHC-benzimi@Cu(6)
The presence of copper in its respective energy position
suggests the formation of complex 6. The EDX analysis
inform loading of 0.22 mmol of Cu per gram of 6 (Fig. 3).
The crystalline material structure and retention of nano-
magnetite (1) in nano-magnetite NHC-benzimi@Cu (6) was
investigated by X-ray difraction (XRD) analysis. The well
indexing of all the peaks in a difractogram to the JCPDS
card No. 86–1339 agreed retention of single-phase inverse
spinel structure of Fe3O4 nano core with high phase purity
and crystallinity (Fig. 4).
The characteristic peaks are at 2θ values of 30.12°,
35.25°, 44.07°, 57.61°, 62.37°, 71.03° and 87.13° are being
assigned to the (2 2 0), (3 1 1), (4 0 0), (5 5 1), (4 4 0), (6 2
0) and (6 4 2) crystallographic planes of Fe3O4 nano core
were observed in the XRD pattern. The most intense peak
was observed for (3 1 1) plane are at 2θ value 35.25°. The
broad peaks are at 2θ from 21° to 32° of the XRD pattern
are assigned to the silica phase.
Fig. 2 TGA curves of bare nano magnetite (1) and nano-magnetite
NHC-benzimi@Cu (6)
The FT-IR spectrum of 3-chloropropyl nano magnet-
ite (3) displayed characteristic peaks at 3408 cm−1 (O–H
stretching), 2925 cm−1 (C–H stretching vibration of propyl
group), 1099 cm−1 (Si–O stretching) (Fig. 1c) [44]. The qua-
ternization of 3 with 4 was realized by appearance of three
The crystallite size calculated with respect to the most
intense peak by using the Scherrer equation was found to
1 3

A. Pawar et al.
Fig. 3 EDX spectrum of nano-
magnetite NHC-benzimi@
Cu(6)
by the grey shell (Fig. 5a, b) [48]. The average nanoparticle
size of 6 is found to be 10 nm with a lattice fringe width dis-
tance of d(311)=2.5182 Å, which reveals formation of the
perfect crystal structure (Fig. 5c). The selected area of elec-
tron difraction (SAED) patterns are exhibited four strong
difraction rings which were assigned to the (3 1 1), (4 0 0),
(3 3 1) and (4 2 2) bright dotted with ring pattern persuade
the polycrystalline nature of nano magnetite (1) (Fig. 5d).
The magnetic properties of nano-magnetite (1) and nano-
magnetite NHC-benzimi@Cu (6) were evaluated by mag-
netic hysteresis loops at room temperature using vibrating
sample magnetometer (VSM) shown in Fig. 6. The satura-
tion magnetization (Ms) 1 and 6 were found to be 53 emug-1
(Fig. 6a) and 30 emug-1 (Fig. 6b) respectively. The satura-
tion magnetization value of 6 exhibited as comparatively
low. This quenching of Ms value is ascribed due to surface
functionalization. However, magnetization exhibited by 6
was sufcient to enough for the efective separation by the
external magnet.
After this initial success in the synthesis of the designed
nano-magnetite NHC-benzimi@Cu (6) catalyst, we focused
our attention towards exploring its catalytic activity in
the click reaction. Initially a model reaction for Huisgen
1,3-dipolar cycloaddition of benzyl chloride, phenylacety-
lene and sodium azide. Product was obtained in the extent
yield with the 40 mg of catalyst at 800C in ethanol (Table 1
entry 7). No signifcant change in the reaction time and yield
of product was observed even though increasing catalytic
loading up to 50 mg (in Table 1 entry 6). When catalytic
loading was reduced to 20 and 10 mg (Table 2 entry 3–5)
Fig. 4 XRD of nano-magnetite NHC-benzimi@Cu(6) (black); XRD
of reused nano-magnetite NHC-benzimi@Cu (6) (blue)
be 51.6 nm. The XRD analysis is revealed preservation of
crystallographic structure of nano-magnetite (1) in 6 even
after the multi-step functionalization.
The surface morphology of the nano-magnetite NHC-
benzimi@Cu (6) was studied by the transmission electron
microscopy (TEM). The TEM micrographs show granules
with spherical shapes and non-smooth surfaces. Now, TEM
images show embedded dark Fe3O4 nano cores surrounded
1 3

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the…
Fig. 5 TEM images of a, b nano-magnetite NHC-benzimi@Cu (6); c nanoparticle shows lattice fringe width; d, e reused nano-magnetite NHC-
benzimi@Cu(6); f SAED pattern of nano-magnetite NHC-benzimi@Cu (6)
increases in the time completion for reaction and decreases
in the product was observed.
Further the screening of solvent was carried out to gives
standard reaction condition. It was observed that the very
excellent yield of 1,2,3-trizoles was obtained in ethanol up
to 94% (Table 2 entry 5) of the yield within a very short
time duration.
While screening of the catalyst, we investigated the sol-
vent efect according to the green chemistry principle. In
water, very poor yield of product was observed and pro-
gress of the reaction was observed by (TLC) which did not
indicate any appreciable progress in the reaction. After we
carried the reaction in the interval of 10 °C temperatures
but still there is no progress in the reaction and we got less
amount of product. Hence we carried the reaction by chang-
ing solvent and temperature. However, the reaction was car-
ried out under refux condition at 80 °C by using ethanol as
a solvent it is noticed that 94% yield of 1,2,3-trizoles was
obtained.
With the optimuml reaction conditions in hands, the
scope and generality of the methodology was evaluated by
the reaction using with terminal alkynes and NaN3 under
optimized reaction conditions and observed that all reactions
proceeds smoothly furnishing desired product in good yields
(Table 3, entries a–j). The results are summarized in Table 3.
In all the cases, reactions proceeded smoothly afording to
the desired 1, 2, 3-trizoles sin a good to excellent yields.
1 3

A. Pawar et al.
(Table 3, entry a, b, c, f) and reactions were clean high yield-
ing without generation of any side product.
The plausible mechanism of the click reaction has been
represented in Scheme 3. Initially, the Cu (I) in the catalyst
is treated with NaN3. Nucleophilic attack of benzyl chloride
and then the attack of phenyl acetylene provides six mem-
bered ring which becomes fve membered after the removal
of Cu (I). This results in formation of desired product.
To ascertain whether the reactions are truly heteroge-
neous, leaching studies were performed by analyzing the
reaction fltrate after the recovery of nano-magnetite NHC-
benzimi@Cu (6) by using the atomic absorption spectros-
copy (AAS). Further, the hot fltration test was carried out to
confrm the heterogeneous nature of nano-magnetite NHC-
benzimi@Cu (6) by using the model reaction. In this test,
a mixture of 6 (40 mg), benzyl Chloride (7a; 1.0 mmol),
sodium azide (8; 1.1 mmol) phenylacetylene (9a; 1.0 mmol),
sodium ascrobate in ethanol (5 mL) was refuxed at 80 °C.
The 6 was separated from the hot reaction mixture when
50% conversion was accomplished (GC). The reaction was
continued with the fltrate for further 6 h. There was no
increase in the yield of the product beyond 50%. In addition,
inductively coupled plasma atomic emission spectroscopic
(ICP-AES) analysis of fltrate shows absence of copper con-
frming the heterogeneous nature of 6.
From the green chemistry point of view, recovery and
recyclability of the supported catalyst is an unavoidable
parameter for industrial and commercial scale that must be
tackled for any catalytic process. Thus, the recovery and
reusability of nano-magnetite NHC-benzimi@Cu (6) inves-
tigated by employing model reaction (Fig. 7).
In brief, after reaction was completed, the 6 was isolated
from the reaction mixture by the magnet. The complex 6
was washed with a copious amount ethanol to remove the
Fig. 6 a Magnetic curve (VSM) of bare nano-magnetite (1). b Mag-
netic curve (VSM) of nano-magnetite NHC-benzimi@Cu (6)
1 3

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the…
Table 1 Optimization of catalyst loading in synthesis of 1,4-disubstituted 1,2,3-trizoles
Entry
Catalyst
Amount of catalyst (mg)
Time (min)
Yielda (%)
TON
TOF (h−1
)
A
B
C
D
E
F
G
H
I
Nano-magnetite (1)
200
200
10
15
20
30
40 (10 mol%)
50
100
200
2880
2880
110
80
50
30
20
19
18
17
–
–
–
–
–
–
[Nano-magnetite-benzimi]Cl (5)
Nano-magnetite NHC-benzimi@Cu (6)
48
50
60
75
94
94
95
95
21,818
16,380
16,450
10,330
8540
4270
3450
3430
11,990
11,050
10,130
9570
10,200
5655
5560
4590
(6)
(6)
(6)
(6)
(6)
(6)
(6)
J
Present works are highlited in bold
Reaction condition: reaction between benzyl chloride (1 mmol), sodium azide (1.1 mmol), phenyl acetylene (1 mmol) solvent: ethanol, catalyst
aIsolated yields after column chromatography
Table 2 Optimization of solvent in synthesis of 1,4-disbstitued 1,2,3-trizoles
Entry
Solvent
Time (min)
Yielda (%)
TON
TOF (h−1
)
1
2
3
4
5
6
7
8
Dichloromethane
DMF
THF
30
36
30
30
20
30
30
30
35
80
60
35
94
60
45
40
3181
6454
8545
3636
5000
5454
4090
3636
66
1490
10,295
993
1250
1394
846
Water
Ethanol
Methanol
Toluene
1,4-Dioxane
389
Present works are highlited in bold
Reaction condition: reaction between benzyl chloride (1 mmol), sodium azide (1.1 mmol), phenyl acetylene (1 mmol) solvent: ethanol, Catalyst,
Temp: 80 °C
aIsolated yields after column chromatography
1 3

A. Pawar et al.
Table 3 Nano-magnetite NHC-benzimi@Cu (6) catalyzed synthesis of 1,4-disbstitued 1,2,3-trizoles
Entry
a
Alkyl halides/aryl halides
(7)
Terminal acetylenes
(9)
Product
(10)
Time
Yielda
(%)
(minute)
20
94
N
N
Cl
Br
Br
N
b
c
d
20
9
N
N
N
20
25
91
81
N N
N
OCH
F
3
Br
N
N
N
OCH
3
OCH
F
3
OCH
3
e
f
30
30
83
90
OCH
F
3
Br
N
N
N
OCH
3
CH
F
3
CH
3
O
O
Cl
N N
O
O
N
F
F
1 3

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the…
Table 3 (continued)
Entry
Alkyl halides/aryl halides
(7)
Terminal acetylenes
(9)
Product
(10)
Time
Yielda
(%)
(minute)
g
40
88
N
N
Br
N
F
F
h
30
90
CN
Br
N N
N
NC
F
F
i
j
30
34
86
87
CN
Br
N N
N
N
NC
N
Br
N N
N
N
N
Reaction condition: reaction between benzyl chloride (1 mmol), sodium azide (1.1 mmol), phenyl acetylene (1 mmol) solvent: ethanol, catalyst
aIsolated yields after column chromatography
organics wedded in the catalyst sites and dried under a
vacuum at room temperature. The amounts of necessary
reactants were recalculated on the basis of recovered cata-
lyst and recovered catalyst could be reused for 12 times
without signifcant decrease in the yield of the products.
Further, the stability of the recycled catalyst was studied by
FT-IR spectroscopy, EDX, XRD and TEM analysis of 6. It
is noteworthy to mention that, the FT-IR (Fig. 1f) spectrum
of reused 6 still retain the prominent peak patterns of the
6. The EDX mapping of the 6 after twelve catalytic cycles
confrms the integrity of the recycled catalyst. Moreover
TEM analysis of fresh (Fig. 5 a–c) and reused 6 (Fig. 5 d,
e) designates that the morphology is preserved even after
12 successive runs.
To demonstrate the importance of nano-magnetite NHC-
benzimi@Cu (6) in comparison with other reported meth-
ods, we have summarized previous report for synthesis of
1,2,3-trizoles in Table 4. The comparison of the results
clearly persuades that the 6 is asuperior catalyst in terms
of the catalyst loading and the reaction time as compared
to the reported catalyst. Apart from the listed catalyst in
Table no. 4, we found that silica, carbon and magnetic
1 3

A. Pawar et al.
Scheme 3 Plausible mechanism for the nano-magnetite NHC-benzimi@Cu (6) catalyzed synthesis of 1,4-disubstituted 1,2,3-trizoles
materials-supported copper species as efcient heteroge-
neous nanocatalysts in “click” reactions have been also
reported with yield 60–98%. However, our catalyst nano-
magnetite NHC-benzimi@Cu (6) demonstrate good ef-
ciency compared with other literature survey [49–62].
4 Conclusion
We have refned a highly selective, economical, efcient
and ecologically clean procedure for one pot multicompo-
nent synthesis of 1,4-disubstituted 1,2,3-triazoles by click
reaction. The reactions were achieved under relatively mild
experimental conditions with high yield and easy recovery
of catalyst. The reusability without any appreciable loss of
activity, ease of work-up short reaction time, magnetically
separable and efcient recyclability of the catalyst make it a
favorable protocol for the reaction.
Fig. 7 Reusability of nano-magnetite NHC-benzimi@Cu (6) in the
synthesis of 1,4 disubstituted 1,2,3 –triazoles
1 3

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the…
Table 4 Comparison of diferent catalyst for synthesis of 10
Sr. No.
Catalyst
Quantity
Temp (°C )
Solvent
Time (min)
Yield %
Ref.
1
Nano-magnetite
40 mg
80
Ethanol
20
94
Present work
NHC-benzimi@Cu
(10 mol%)
2
3
4
CuNPs/activated carbon
CuFe2O4 NPs
10 mg
10 mol %
5 mol %
70
RT
80
Water
Water
Water
180
60
480
93
95
98
49
50
51
CuBr on grapheme
Oxide/Fe3O4benzyle chloride
5
6
CuFe2O4
12 mg
25 mg
70
70
Water
Water
240
20
84
94
52
53
Fe3O4@
SiO2-cafeine–CuI
7
8
9
10
11
12
13
14
15
Cu
[Cu(NHC)]
0.5 mol %
0.5 mol %
40 mg
40 mg
5 mol%
10 mg
1 mol%
20 mg
1 mol%
80
RT
80
RT
80
45
RT
75
25
Water
Water
Ethanol
Methanol
Water
Water
Water
Choline azide
water
6 h
2 h
20 min
480
480
80
90
25
60
96
90
96
75
90
97
95
90
98
54
55
3
56
57
58
59
60
61
Cu-ACP-Am-Fe3O4@SiO2
Cu NPs
GO/Fe3O4–CuBr
GO/Fe3O4–CuO
SBA-15/Thioamide-Cu(I)
Fe3O4@LDH@cysteine–Cu(I)
Cu(II)@Silica
Present works are highlited in bold
Reaction condition: reaction between benzyl chloride (1 mmol), sodium azide (1.1 mmol), phenyl acetylene (1 mmol) solvent: ethanol, catalyst,
temp: 80 °C
6. Kelley JL, Koble CS, Davis RG, McLean EW, Soroko FE, Cooper
BR (1995) 1-(Fluorobenzyl)-4-amino-1H-1,2,3-triazolo[4,5-c]pyri-
dines: synthesis and anticonvulsant activity. J Med Chem 38:4131
7. Micetich RG, Maiti SN, Spevak P, Hall TW, Yamabe S, Ishida N,
Tanaka M, Yamazaki T, Nakai A, Ogawa K (1987) Synthesis and
.beta.-lactamase inhibitory properties of 2.beta.-[(1,2,3-triazol-
1-yl)methyl]-2.alpha.-methylpenam-3.alpha.-carboxylic acid
1,1-dioxide and related triazolyl derivatives. J Med Chem 30:1469
8. Saravanana V, Ganesan S, Rajakumar P (2020) Synthesis and
DSSC application of BODIPY decorated triazole bridged and ben-
zene nucleus cored conjugated dendrimers. RSC Adv 10:18390
9. Shiri P, Amani AM (2021) A brief overview of catalytic applica-
tions of dendrimers containing 1,4-disubstituted-1,2,3-triazoles.
Monatsh Chem 152:367
Supplementary Information The online version contains supplemen-
tary material available at https://doi.org/10.1007/s10562-021-03772-9.
Acknowledgements We gratefully acknowledge Indian Institute of
Bombay (IITB), North-Eastern Hill University Shillong (NEHU),
Indian Institute of Technology, Madras (IITM) for providing spectral
facilities and Central Facility Centre (CFC) Shivaji University Kol-
hapur for providing quantitative spectral analysis.
Declarations
Conflict of interest The authors declare no confict of interest.
10. Le-Nhat-Thuya G, Nguyen Thib N, Pham-Thed H, Dang Thia TA,
Nguyen TH, Nguyen Thia TH, Nguyen HS, Nguyen TV (2020)
Synthesis and biological evaluation of novel quinazoline-triazole
hybrid compounds with potential use in Alzheimer’s disease.
Bioorg Med Chem Lett 30:127404
References
1. Anil Kumar BSP, Reddy KHV, Madhav B, Ramesh K, Nageswar
YVD (2012) Magnetically separable CuFe2O4 nano particles cata-
lyzed multicomponent synthesis of 1,4-disubstituted 1,2,3-tria-
zoles in tap water using ‘click chemistry. Tetahedron Lett 53:4595
2. Singh MS, Chowdhury S, Koley S (2016) Advances of azide-
alkyne cycloaddition-click chemistry over therecent decade. Tet-
rahedron 72:5257
11. Shiri P (2021) Novel hybrid molecules based on triazole-β-lactam
as potential biological agents. Mini Rev Med Chem 21:536
12. Mashayekh K, Shiri P (2019) An overview of recent advances in
the applications of click chemistry in the synthesis of bioconju-
gates with anticancer activities. Chem Select 4:13459
13. Sau SC, Hota PK, Mandal SK, Soleilhavoup M, Bertrand G (2020)
Stable abnormal N-heterocyclic carbenes and their applications.
Chem Soc Rev 49:1233
3. Vibhute SP, Mhaldar PM, Korade SN, Gaikwad DS, Shejawal RV,
Pore DM (2018) Synthesis of magnetically separable catalyst Cu-
ACP-Am-Fe3O4@SiO2 for Huisgen 1,3-dipolar cycloaddition.
Tetahedron Lett 59:3643
14. Flanigan DM, Romanov-Michailidis F, White NA, Rovis T (2015)
Organocatalytic reactions enabled by N-heterocyclic carbenes.
Chem Rev 15:9307
4. Heravi MM, Zadsirjan V, Dehghani M, Ahmadi T (2018) Towards
click chemistry: multicomponent reactions via combinations of
name reactions. Tetrahedron 74:3391
15. Cao J, Yu M, Li H, Wang L, Zhu X, Wang G, Shi Y, Cao C (2015)
Synthesis of cyclic di- and trithiocarbonates from epoxides and
carbon disulfde catalyzed by N-heterocyclic carbine. Res Chem
Intermed 41:5323
5. Buckle DR, Outred DJ, Rockell CJM, Smith H, Spicer BA
(1983) Studies on v-triazoles. 7. Antiallergic 9-oxo-1H,9H-
benzopyrano[2,3-d]-v-triazoles. J Med Chem 26:251
1 3

A. Pawar et al.
16. Diaz-Velazquez H, Verpoor F (2012) N-heterocyclic carbene tran-
sition metal complexes for catalysis in aqueous media. Chem Soc
Rev 41:7032
37. Khanapure S, Jagadale M, Salunkhe R, Rashinkar G (2016) Zir-
conocene dichloride catalyzed multi-component synthesis of
1-amidoalkyl-2-naphthols at ambient temperature. Res Chem
Intermed 42:2075
17. Herrmann WA (2002) N-heterocyclic carbenes: a new concept in
organometallic catalysis. Angew Chem Int Ed 41:1290
18. Hopkinson MN, Richter C, Schedler M, Glorius F (2014) An over-
view of N-heterocyclic carbenes. Nature 510:485
38. Patil SS, Pawar PB, Jadhav SD, Deshmukh MB (2013) An ef-
cient one-pot multicomponent synthesis of dihydropyridines by
using succinic acid as mild organocatalyst. Asian J Chem 25:9442
39. Patil SS, Jadhav SD, Deshmukh MB (2011) Natural acid catalyzed
multi-component reactions as a green approach. Arch Appl Sci
Res 3:203
19. Janssen-Muller D, Schlepphorst C, Glorius F (2017) Privileged
chiral N-heterocyclic carbene ligands for asymmetric transition-
metal catalysis. Chem Soc Rev 46:4845
20. Diez-Gonzalez S, Nolan SP (2017) Stereoelectronic parameters
associated with N-heterocyclic carbene (NHC) ligands: a quest
for understanding. Coord Chem Rev 251:874
40. Patil A, Mane A, Kamat S, Lohar T, Salunkhe R (2019) Aqueous
hydrotropic solution: green reaction medium for synthesis of pyri-
dopyrimidinecarbonitrile and spiro-oxindoledihydroquinazolinone
derivatives. Res Chem Intermed 45:3441
21. Huynh HV (2018) Electronic properties of N-heterocyclic car-
benes and their experimental determination. Chem Rev 118:9457
22. Sommer WJ, Weck M (2007) Supported N-heterocyclic carbene
complexes in catalysis. Coord Chem Rev 251:860
41. Zhao X, Shi Y, Wang T, Cai Y, Jiang G (2008) Preparation of
silica-magnetite nanoparticle mixed hemimicelle sorbents for
extraction of several typical phenolic compounds from environ-
mental water samples. J Chomatogr A 1188:140
23. Huang HJ, Lee WC, Yap GPA, Ong TG (2014) Synthesis and
characterization of amino-NHC coinage metal complexes and
application for C–H activation of cafeine. J Organomet Chem
761:64
42. Liu Q, Xu Z, Finch JA, Egerton R (1998) A novel two-step silica-
coating process for engineering magnetic nanocomposites. Chem
Mater 10:3936
24. Dorta R, Stevens ED, Scott NM, Costabile C, Cavallo L, Hof CD,
Nolan PS (2005) Steric and electronic properties of N-heterocy-
clic carbenes (NHC): a detailed study on their interaction with
Ni(CO)4. J Am Chem Soc 127:2485
43. Kooti M, Afshari M (2012) Phosphotungstic acid supported on
magnetic nanoparticles as an efcient reusable catalyst for epoxi-
dation of alkenes. Mater Res Bull 47:3473
44. Zolfgol MA, Ayazi-Nasrabadi R (2016) Synthesis of the frst
magnetic nanoparticles with a thiourea dioxide-based sulfonic
acid tag: application in the one-pot synthesis of 1,1,3-tri(1H-
indol-3-yl) alkanes under mild and green conditions. RSC Adv
6:69595
25. Guisado-Barrios G, Boufard J, Donnadieu B, Bertrand G (2010)
Crystalline 1H–1,2,3-triazol-5-ylidenes: new stable mesoionic
carbenes (MICs). Angew Chem Int Ed 49:4759
26. Cazin CSJ (2009) Recent advances in the design and use of immo-
bilised N-heterocyclic carbene ligands for transition-metal cataly-
sis. Chim CR 12:1173
45. Salamatmanesh A, Miraki MK, Yazdani E, Heydari A (2018)
Copper(I)–cafeine complex immobilized on silica-coated mag-
netite nanoparticles: a recyclable and eco-friendly catalyst for
click chemistry from organic halides and epoxides. Catal Lett
148:3257
27. Zhong R, Lindhorst AC, Groche FJ, Kuhn F (2017) Immobiliza-
tion of N-heterocyclic carbene compounds: a synthetic perspec-
tive. Chem Rev 117:1970
28. Gajare S, Patil A, Hangirgekar S, Dhanmane S, Rashinkar G
(2020) Green synthesis of quinolines via A3-coupling by using
graphene oxide-supported Brønsted acidic ionic liquid. Res Chem
Intermed 46:2417
46. Pellei M, Gandin V, Marzano C, Marinelli M, Bello FD, Santini
C (2018) The frst water-soluble copper(I) complexes bearing
sulfonated imidazole- and benzimidazole-derived N-heterocyclic
carbenes: synthesis and anticancer studies. Appl Organomet Chem
32:4185
29. Jagadale M, Khanapure S, Salunkhe R, Rajmane M, Rashinkar
G (2016) Sustainable synthesis of sulfonamides using supported
ionic liquid phase catalyst containing Keggin-type anion. Appl
Organomet Chem 30:25
47. Miraki MK, Aref M, Salamatmanesh A, Yazdani E, Heydari A
(2018) Magnetic nanoparticle-supported Cu–NHC complex as an
efcient and recoverable catalyst for nitrile hydration. Catal Lett
148:3378
30. Hajipour AR, Tadayoni NS, Khorsandi Z (2016) Magnetic iron
oxide nanoparticles–N-heterocyclic carbene–palladium(II): a
new, efcient and robust recyclable catalyst for Mizoroki–Heck
and Suzuki–Miyaura coupling reactions. Appl Organomet Chem
30:590
48. Ying A, Hou H, Liu S, Chen G, Yang J, Xu S (2016) Ionic modi-
fed TBD supported on magnetic nanoparticles: a highly efcient
and recoverable catalyst for organic transformations. Sustain ASC
Chem Eng 4:625
31. NasirBaig RB, Varma RS (2013) Magnetically retrievable cata-
lysts for organic synthesis. Chem Commun 49:752
49. Ghosh S, Badruddoza AZM, Uddin MS, Hidajat K (2011)
Adsorption of chiral aromatic amino acids onto carboxymethyl-β-
cyclodextrin bonded Fe3O4/SiO2 core–shell nanoparticles. Colloid
J Interface Sci 354:483
32. Sharma PK, Dutta S, Sharma S, Zboril R, Varma RS, Gawande
MB (2016) Fe3O4 (iron oxide)-supported nanocatalysts: synthe-
sis, characterization and applications in coupling reactions. Green
Chem 18:3184
50. Kim J, Stahl S (2015) Cu-catalyzed aerobic oxidative three-com-
ponent coupling route to N-sulfonyl amidines via an ynamine
intermediate. J Org Chem 80:2448
33. Wang P, Kong AG, Wang WJ, Zhu HY, Shan YK (2010) Facile
preparation of ionic liquid functionalized magnetic nano-solid
acid catalysts for acetalization reaction. Catal Lett 135:159
34. Yuan J, Xu Y, Muller AHE (2011) One-dimensional magnetic
inorganic–organic hybrid nanomaterials. Chem Soc Rev 40:640
35. Gawande MB, Branco PS, Varma RS (2013) Nano-magnetite
(Fe3O4) as a support for recyclable catalysts in the development
of sustainable methodologies. Chem Soc Rev 42:3371
36. Kurane R, Jadhav J, Khanapure S, Salunkhe R, Rashinkar G
(2013) Synergistic catalysis by an aerogel supported ionic liquid
phase (ASILP) in the synthesis of 1,5-benzodiazepines. Green
Chem 15:1849
51. Jagadale M, Bhange P, Salunkhe R, Bhange D, Rajmane M,
Rashinkar G (2016) One-pot multicomponent synthesis of N-sul-
fonyl amidines using magnetic separable nanoparticles-decorated
N-heterocyclic carbene complex with copper. Appl Catal A
211:95
52. Kim SH, Park SH, Choi JH, Chang S (2011) Sulfonyl and phos-
phorylazides: going further beyond the click realm of alkyl and
aryl azides. Chem Asian J 6:2618
53. Bae I, Han H, Chang S (2005) Highly efcient one-pot synthesis
of N-sulfonylamidines by Cu-catalyzed three-component coupling
of sulfonyl azide, alkyne, and amine. J Am Chem Soc 27:2038
1 3

Supported NHC-Benzimi@Cu Complex as a Magnetically Separable and Reusable Catalyst for the…
54. Yang T, Cui H, Zhang C, Zhang L, Su CY (2013) Porous metal-
organic framework catalyzing the three-component coupling of
sulfonyl azide, alkyne, and amine. Inorg Chem 52:9053
55. Hwang SJ, Cho SH, Chang SB (2008) Evaluation of catalytic
activity of copper salts and their removal processes in the three-
component coupling reactions. Pure Appl Chem 80:873
56. Tasca E, Sorella GL, Sperni L, Strukul G, Scarso A (2015) Micel-
lar promoted multi-component synthesis of 1,2,3-triazoles in
water at room temperature. Green Chem 17:1414
59. Pourhassan F, Eshghi H (2020) Novel hybrid thioamide ligand
supported copper nanoparticles on SBA-15: a copper rich robust
nanoreactor for green synthesis of triazoles and tetrazoles in water
medium. Catal Lett 150:1287
60. Pazoki F, Salamatmanesh A, Bagheri S, Heydari A (2020) Synthe-
sis and characterization of copper(i)-cysteine complex supported
on magnetic layered double hydroxide as an efcient and recyclable
catalyst system for click chemistry using choline azide as reagent
and reaction medium. Catal Lett 150:1186
57. Xiong X, Chen H, Tang Z, Jiang Y (2014) Supported CuBr on
graphene oxide/Fe3O4: a highly efcient, magnetically separable
catalyst for the multi-gram scale synthesis of 1,2,3-triazoles. RSC
Adv 4:9830
61. Sharghi H, Shiri P, Aberi M (2017) Five-membered N-hetero-
cycles synthesis catalyzed by nanosilica supported copper(II)–
2-imino-1,2-diphenylethan-1-ol complex. Catal Lett 147:2844
62. Shiri P, Aboonajmi J (2020) A systematic review on silica- carbon
and magnetic materials-supported copper species as efcient hetero-
geneous nanocatalysts in “click” reactions n. J Org Chem 16:551
58. Jain Y, Kumari M, Singh RP, Kumar D, Gupta R (2019) Sono-
chemical decoration of graphene oxide with magnetic Fe3O4@
CuO nanocomposite for efcient click synthesis of coumarin-
sugar based bioconjugates and their cytotoxic activity. Catal Lett
150:1142
Publisher's Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
Authors and Afliations
Arvind Pawar1,3 · Shivanand Gajare2 · Ashutosh Jagdale1 · Sandip Patil1 · Wilson Chandane2 · Gajanan Rashinkar2 ·
Suresh Patil1
2
* Suresh Patil
sanyujapatil@yahoo.com
Department of Chemistry, Shivaji University, Kolhapur,
M. S. 416004, India
3
Department of Chemistry, Shikshanmaharshi Dr.Bapuji
Salunkhe College, Miraj, M. S. 416412, India
1
Department of Chemistry, Padmabhushan Dr. Vasantraodada
Patil College, Dist. Sangli., Tasgaon, M. S. 416312, India
1 3