N-Heterocyclic carbene–copper complex supported on ionic liquid-modified graphene oxide: versatile catalyst for synthesis of (i) 1,2,3-triazole and (ii) propargylamine derivatives

Article abstract of DOI:10.1007/s13738-018-1435-7

A N-heterocyclic carbene–copper complex grafted on graphene oxide with an ionic liquid framework was prepared. The synthesis of (i) 1,2,3-triazole derivatives by ‘Click reaction’ and (ii) propargylamine derivatives by ‘A³ coupling reaction’ in

Full text of DOI:10.1007/s13738-018-1435-7

Journal of the Iranian Chemical Society
https://doi.org/10.1007/s13738-018-1435-7
ORIGINAL PAPER
N-Heterocyclic carbene–copper complex supported on ionic liquid-
modified graphene oxide: versatile catalyst for synthesis of (i)
1,2,3-triazole and (ii) propargylamine derivatives
Minoo Dabiri1 · Seyed Iman Alavioon · Siyavash Kazemi Movahed
1
1
Received: 27 July 2017 / Accepted: 22 June 2018
©
Iranian Chemical Society 2018
Abstract
A N-heterocyclic carbene–copper complex grafted on graphene oxide with an ionic liquid framework was prepared. The
3
synthesis of (i) 1,2,3-triazole derivatives by ‘Click reaction’ and (ii) propargylamine derivatives by ‘A coupling reaction’
in aqueous media by this new catalyst were all successfully accomplished. The catalyst is characterized using infrared
spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetric analysis and energy dispersive X-ray
spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental analysis. The catalyst is
reused in the ten reaction cycles without considerable loss of catalytic activity.
Electronic supplementary material The online version of this
article (https://doi.org/10.1007/s13738-018-1435-7) contains
supplementary material, which is available to authorized users.
Extended author information available on the last page of the article
Vol.:(0
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Journal of the Iranian Chemical Society
Graphical abstract
Keywords Graphene · Carbene ligands · Heterogeneous catalysis · Copper
Introduction
carboxylation and carbonylations, carbene and nitrene
transfer reagents, and so forth [9].
Since the initial study of a metal coordinated by an
Recycling is becoming significantly more important
nowadays as environmental harms increase and resources
are becoming scarcer. Chemists continue to develop new
catalysts that are more efficient, robust and devise novel
methods to recover and recycle them. Towards this purpose,
the immobilization of well-known catalysts onto the sup-
ports often facilitates the recycling of catalysts. As described
above, organometallic NHC complexes have shown high
performances in several reactions, demonstrating their utility
in the synthesis of complex molecules that have applications
ranging from drug precursors to polymers. These impor-
tant applications make the NHC ligand a perfect nominee
to be supported. However, it must be demonstrated that the
catalytic activity of the supported NHC complexes does not
change with the nature of the support. Over the last decade,
NHCs have been grafted onto different supports such as car-
bon, magnetic particles, polymer, silica, etc. [10].
N-heterocyclic carbene (NHC) by Öfele and Wanzlick in
1
968 and the breakthrough and isolation of the first sta-
ble nitrogen heterocyclic carbene by Arduengo in 1991,
NHCs have become ubiquitous in the chemical literature,
particularly as ligands for metal complexes [1]. Compared
with phosphine ligands, NHCs have strong σ-donor and
low π-acceptor ability while they can make stronger bonds
with almost all metals [2, 3]. Coinage metal-NHCs are
widely studied for their interesting structural properties
and many applications [4]. Despite being the least stable
among the coinage metal–NHC complexes, investigations
on Cu(I)- and Cu(II)-NHCs have increased substantially.
These are primarily due to their potential as catalysts in
many organic transformations. Copper catalysts with a
tunable NHC ligand enable improved reactivity and reac-
tion selectivity [6–8]. Their catalytic applications have
been reported in various organic transformations, includ-
ing hydrosilylation reactions, conjugate addition, [3 + 2]
cycloaddition of azides and alkynes, allylic substitutions,
2
Recently, graphene, a single layer of sp carbon atoms
bonded in a hexagonal lattice, has attracted considerable
attention from scientists all over the world. Unlike other
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Journal of the Iranian Chemical Society
materials, including inorganic solids or organic polymers,
graphene has a distinctive two-dimensional structure and
intriguing properties, including impressive mechanical
strength and exceptional electronic and optical properties
Preparation of IL
The N-3-(3-trimethoxysilyl propyl)-3-methyl imidazolium
1
chloride (IL) was prepared by Yang procedures [17]. H-
[
11, 12]. These properties make graphene a promising sup-
NMR (300 MHz, DMSO-d ): δ=10.29 (s, 1H), 7.63 (s, 1H),
6
port for N-heterocyclic carbene in heterogeneous catalysis.
Herein, we show an efficient method for the synthesis
of a supported copper catalyst covalently anchored onto
graphene oxide (GO). A copper complex (NHC–Cu), an
excellent catalyst for the synthesis of propargylamines
and triazoles [9, 13–15], is covalently anchored onto the
planar GO surface. This procedure involved the silylation
of the GO with the IL and subsequently the formation
of Cu–NHC through the reaction of GO-IL with CuI in
the presence of t-BuONa as base (Scheme 1). The cata-
lytic performance of the supported catalyst (NHC–Cu/
GO-IL) is investigated for the synthesis of triazoles and
propargylamines.
7.33 (s, 1H), 4.13 (t, J=7.2 Hz, 2H), 3.93 (s, 3H), 3.34 (s,
1
3
9H), 1.86–1.76 (m, 2 h), 0.43 (t, J=8.0 Hz, 2H); C-NMR
(75 MHz, DMSO-d ): δ = 137.24, 124.06, 122.65, 51.32,
6
50.58, 36.16, 23.87, 5.83.
Preparation of GO‑IL
The GO (0.20 g) was ultrasonically dispersed in 100 mL of
ethanol. Then, IL (2 mmol) was added to the GO suspension
under stirring and refluxed for 12 h. The yielded suspension
was centrifuged and washed with ethanol for several times
to get a purified GO-IL.
Preparation of NHC–Cu/GO‑IL
The GO-IL (0.10 g) was ultrasonically dispersed in 50 mL
Experimental
of tetrahydrofuran. Then, CuI (0.022 mmol) and t-BuONa
(
1 mmol) were added to the GO suspension under stirring
Preparation of GO
at room temperature for 24 h. The yielded suspension was
centrifuged and washed with acetonitrile for several times to
get a purified NHC–Cu/GO-IL. The loading of imidazolium
The GO was prepared by Hummers’ method [16].
Scheme 1 Illustration of synthetic methodology of NHC–Cu/GO-IL
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Journal of the Iranian Chemical Society
and imidazol-2-ylidene–Cu complex was determined to be
Transmission electron microscopy characterization of
NHC–Cu/GO-IL composite was performed using a trans-
mission electron microscope Philips CM-30 with an accel-
−
1
1
.14 mmol g by means of the nitrogen content obtained
from the elementary analysis (CHN). The copper content
−
1
1
of the catalyst was found to be 0.69 mmol g based on
AA analysis. This means that 60.52% of the imidazolium
groups in the graphene oxide support participated in the for-
mation of Cu complex. The low loading of Cu implies that
the majority of t-BuONa may be deactivated by hydroxyl
groups on the surface layer of the graphene oxide support.
erating voltage of 150 kV. H-NMR spectra were recorded
on a BRUKERDRX-300AVANCE spectrometer. X-ray
photoelectron spectroscopy (XPS) analysis of NHC–Cu/
GO-IL composite was performed using a Thermo Scientific,
ESCALAB 250Xi with Mg X-ray resource. NMR spectra
were obtained in DMSO-d using TMS as the internal stand-
6
ard. Melting points of products were measured on an Elec-
trothermal 9100 apparatus and are uncorrected. The con-
centration of copper was estimated using Shimadzu AA-680
flame atomic absorption spectrophotometer and inductively
coupled plasma optical emission spectrometer (ICP-OES)
Varian Vista PRO Radial. The thermal stability of the GO,
GO-IL and NHC–Cu/GO-IL composites were determined
using a thermogravimetric analyzer (TGA/DTA BAHR:
General procedure for the 1,3‑dipolar cycloaddition
A mixture of aryl azide (1.0 mmol), aryl acetylene
(
1.0 mmol) and Cu–NHC/GO-IL (1 mol% of Cu) in mixture
EtOH:H O (1:1, 2 mL) as the solvent was heated at 70 °C for
2
1
h. After completion of the reaction (TLC), the heterogene-
ous mixture was cooled to room temperature, and the ethyl
acetate was added to the flask, and the catalyst was separated
by centrifugation. The products were extracted with ethyl
acetate–water mixture. The combined organic layers were
−
1
STA 503) under argon and a heating rate of 10 °C min .
Elemental analysis of NHC–Cu/GO-IL nanocomposite was
performed using a Heraeus CHN-O Rapid analyzer.
All of the products are known compounds and were
reported previously [18–24].
dried over MgSO and concentrated under reduced pressure
4
to give the corresponding 1,2,3-triazole. Obtained triazole
was purified by recrystallization from ethanol.
3
General procedure for the A coupling
A mixture of aldehyde (1.0 mmol), secondary amine
(
1.2 mmol), ethynylbenzene (1.3 mmol), and Cu–NHC/
1
-(4-Bromophenyl)-4-phenyl-1H-1,2,3-triazole; white
GO-IL composite (1 mol% of Cu) in H O (3 mL) was
2
1
solid, mp: 232–234 °C (lit. [18], mp: 239–241 °C). H-NMR
refluxed for 4 h. After completion of the reaction (TLC),
the heterogeneous mixture was cooled to room temperature,
and the catalyst was separated by centrifugation. The prod-
ucts were extracted with ethyl acetate–water mixture. The
(
300 MHz, DMSO-d ) δ 9.34 (s, 1H), 8.02–7.93 (m, 4H),
6
7
.73 (d, J=8.3 Hz, 2H), 7.54–7.37 (m, 3H).
combined organic layers were dried over MgSO and con-
4
centrated under reduced pressure to give the corresponding
propargylamine. Obtained propargylamine was purified by
thin layer chromatography (SiO , ethyl acetate, and n-hex-
2
ane) to yield pure product.
1
-(3-Nitrophenyl)-4-phenyl-1H-1,2,3-triazole; yellow
The catalysts were recovered by centrifugation and
washed thoroughly with acetone and deionized water and
dried in the air.
1
solid, mp: 196–198 °C (lit. [19], mp: 197–199 °C). H-NMR
(
300 MHz, DMSO-d ) δ 9.57 (s, 1H), 8.79 (d, J =2.3 Hz,
6
1
8
1
H), 8.46 (d, J = 8.1 Hz, 1H), 8.36 (d, J = 8.2 Hz, 1H),
.01–7.88 (m, 3H), 7.53 (t, J =7.6 Hz, 2H), 7.53–7.39 (m,
H).
Characterization
All chemicals were purchased from commercial suppliers,
and all solvents were purified and dried using standard pro-
cedures. IR spectra were recorded on a Bomem MB-Series
FT-IR spectrophotometer. Raman spectra of GO, GO-IL,
and NHC–Cu/GO-IL composites were recorded on a Bruker
SENTERR (2009) with an excitation beam wavelength at
1,4-Diphenyl-1H-1,2,3-triazole; yellow solid, mp:
1
7
85 nm. Scanning electron microscopy and EDX map-
183–185 °C (lit. [18], mp: 184–185 °C). H-NMR
ping characterizations of NHC–Cu/GO-IL composite were
performed using an electron microscopy Hitachi SU3500.
(300 MHz, DMSO-d ) δ 9.35 (s, 1H), 8.05–7.90 (m, 4H),
6
7.73 (d, J=8.8 Hz, 2H), 7.53–7.37 (m, 4H).
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Journal of the Iranian Chemical Society
(
300 MHz, CDCl ), δ 9.35 (s, 1H), 8.02–7.94 (m, 4H),
3
7
.73 (d, J = 8.3 Hz, 2H), 7.52 (t, J = 7.5 Hz, 2H), 7.40 (t,
J=7.4 Hz, 1H).
1
-(4-Chlorophenyl)-4-(4-(trif luoromethyl)
phenyl)-1H-1,2,3-triazole; white solid, mp: 197–199 °C.
1
(
(
lit. [21], mp: 194–196 °C). H-NMR (300 MHz, CDCl ), δ
3
ppm): 9.54 (s, 1H), 8.16 (d, J=8.1 Hz, 2H), 8.06–7.97 (m,
2
H), 7.91–7.83 (m, 2H), 7.82–7.69 (m, 2H).
Fig. 1 Raman spectra of GO, GO-IL, and NHC–Cu/GO-IL compos-
ites
1
-(4-Chlorophenyl)-4-(p-tolyl)-1H-1,2,3-triazole; white
1
solid, mp: 243–245 °C (lit. [22], mp: 244–246 °C). H-NMR
(
300 MHz, CDCl ) δ 9.25 (s, 1H), 7.99 (d, J=8.5 Hz, 2H),
3
7
.83 (d, J=7.7 Hz, 2H), 7.71 (d, J=8.5 Hz, 2H), 7.31 (d,
J=7.8 Hz, 2H), 2.36 (s, 3H).
1
-(4-Chlorophenyl)-4-phenyl-1H-1,2,3-triazole; white
1
solid, mp: 236–238 °C (lit. [20], mp: 237–238 °C). H-NMR
Fig. 2 FT-IR spectra of GO,
GO-IL and NHC–Cu/GO-IL
composites
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Journal of the Iranian Chemical Society
4
-(1-(4-Chlorophenyl)-3-phenylprop-2-yn-1-yl)morpho-
1
line; yellow oil [22], H-NMR (300 MHz, CDCl ) δ 7.65 (d,
3
J=7.6 Hz, 2H), 7.57–7.49 (m, 2H), 7.44–7.31 (m, 5H), 4.82
(
s, 1H), 3.80–3.70 (m, 4H), 2.66 (t, J=4.7 Hz, 4H).
Fig. 3 SEM images of NHC–Cu/GO-IL
Fig. 4 SEM images of a NHC–
Cu/GO-IL, and the correspond-
ing quantitative EDS elemental
mapping of b Cu, c N and d Si
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Journal of the Iranian Chemical Society
4
-(1,3-Diphenylprop-2-yn-1-yl)morpholine; yellow oil
1
[
22], H-NMR (300 MHz, CDCl ) δ 7.60 (d, J = 8.3 Hz,
3
2
3
H), 7.55–7.52 (m, 2H), 7.42–7.28 (m, 6H), 4.78 (s, 1H),
.82–3.72 (m, 4H), 2.63 (t, J=4.7 Hz, 4H).
4
-(1-(4-Nitrophenyl)-3-phenylprop-2-yn-1-yl)mor-
1
pholine; yellow oil [23], H-NMR (300 MHz, CDCl ) δ
3
8
2
2
.30–8.20 (m, 2H), 7.88 (d, J=8.4 Hz, 2H), 7.59–7.50 (m,
H), 7.40–7.37 (m, 3H), 4.90 (s, 1H), 3.80–3.73 (m, 4H),
.67 (d, J=8.7 Hz, 4H).
Fig. 5 TEM image of NHC–Cu/GO-IL composite
4
-(3-Phenyl-1-(p-tolyl)prop-2-yn-1-yl)morpholine; yel-
1
low oil [24], H-NMR (300 MHz, CDCl ) δ 7.54–7.51 (m,
3
5
1
H), 7.39–7.33 (m, 3H), 7.19 (d, J= 7.6 Hz, 2H), 4.77 (s,
H), 3.77–3.73 (m, 4H), 2.67–2.63 (m, 4H). 2.38 (s, 3).
Fig. 6 TGA plots of GO, GO-IL, and the NHC–Cu/GO-IL composites
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Journal of the Iranian Chemical Society
Fig. 7 a Full range XPS spectrum of NHC–Cu/GO-IL composite; the core level regions’ XPS spectra of b Si 2p, c N 1s, d Cu 2p
Results and discussion
The GO-IL spectrum exhibits three new peaks around 748,
−
1
1
060 and 1573 cm , compared to the GO spectrum. These
Raman spectroscopy is a very useful tool for investigat-
ing the electronic and phonon structure of graphene-based
materials. The Raman spectra of the prepared GO, GO-IL,
and NHC–Cu/GO-IL (Fig. 1) show an obvious and step-
by-step blue shift of the G band from 1584.77 to 1587.60
peaks corresponded to the stretching vibrations of Si–O–C,
Si–O and the ring vibration of the imidazole, respectively,
and provide direct evidence for the successful silylanization
of the GO [17, 29]. The vibrational mode of C–N stretching
−
1
(1290 cm ) in the NHC ring is apparent after the formation
of the NHC–Cu complex on GO-IL in FT-IR spectrum of
NHC–Cu/GO-IL [30].
−
1
and 1594.11 cm , probably due to the gradual increase in
compressive local tension induced by the attached IL and
NHC–Cu on the surface of GO [25–27].
The microstructure and morphology of the composite are
characterized using scanning electron microscopy (SEM)
and transmission electron microscopy (TEM). A SEM image
of the NHC–Cu/GO-IL displays two-dimensional structures
with a rumpling feature (Fig. 3). Additionally, the density
and dispersion of NHC–Cu and IL groups on the NHC–Cu/
GO-IL composite were evaluated by energy dispersive X-ray
spectroscopy (EDS) mapping (Fig. 4). As it can be seen in
The FT-IR spectra of the GO, GO-IL, and NHC–Cu/
GO-IL composites are shown in (Fig. 2). The spectrum of
the GO and the characteristic bands at 1043, 1224, 1398,
−
1
1
647 and 1731 cm correspond to the C–O–C stretching
vibrations, the C–OH stretching peak, the O–H deformation
of the C–OH groups, the C=C stretching mode and the C=O
stretching vibrations of the CO H group, respectively [28].
2
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Journal of the Iranian Chemical Society
Table 1 Screening of the reaction condition
Entry
Solvent
Temp. (°C)
Yielda
1
2
3
4
5
6
7
MeOH
MeCN
CHCl3
EtOH
Reflux
Reflux
Reflux
70
70
70
60
70
70
89
78
69
86
77
93
84
62
H O
2
EtOH:H O (1:1)
EtOH:H O (1:1)
EtOH:H O (1:1)
EtOH:H O (1:1)
2
2
b
8
9
2
c
d
36
2
Fig. 8 SEM image of NHC–Cu/GO-IL composite after ten cycles
Ethynylbenzene (1 mmol), azidobenzene (1 mmol), solvent (2 mL),
1
h, Cu–NHC/GO-IL (1 mol% of Cu)
a
b
c
d
Thermogravimetric analysis (TGA) is further used
to study the thermal behavior and stability of the
NHC–Cu/GO-IL composite. TGA plots of the GO, GO-IL,
and NHC–Cu/GO-IL composites are presented in Fig. 6. It
can be observed that GO is thermally unstable and it is one
significant drop in mass at around 160–330 °C. The is due
to decomposition of the labile oxygen-containing functional
groups [31]. Compared with the curve of GO, the weight
loss of GO-IL below 300 °C is much less, indicating that the
main oxygen-containing functional group (hydroxyl group)
of GO has been reacted after reacting with IL. In contrast,
the NHC–Cu/GO-IL composite showed good thermal dura-
bility. The total weight lost was only 13% at temperatures
below 200 °C.
Isolated yield
Cu–NHC/GO-IL (0.5 mol% of Cu)
GO-IL (0.05 g)
Two 1,4- and 1,5-regioisomers (~1:1)
Table 2 1,3-Dipolar cycloaddition of aryl azides and terminal
alkynes catalyzed by Cu–NHC/GO-IL composite
Entry
R1
R2
Yielda
The electronic properties of the NHC–Cu/GO-IL com-
posite were probed by X-ray photoelectron spectroscopy
1
2
3
4
5
6
7
8
H
4-NO2
4-Cl
4-Cl
4-Cl
4-Br
3-NO2
4-CH3
H
H
4-CH3
4-CF3
H
H
H
H
93
99
94
90
96
94
89
92
(
XPS) analysis (Fig. 7). The peaks corresponding to C 1s,
Cl 2s, Cu 2p, N 1s, I 3d, O 1s, and Si 2p and 2s are observed
in the XPS full spectrum. The Si 2p core level region could
be split into two peaks. The first one at 101.57 eV is attrib-
uted to Si–O–C bonds, while the other one at 102.96 eV
corresponds to the silicon participant from the siloxane net-
work (Si–O–Si) resulting from the condensation of silane
molecules [27]. The N 1s could be divided into two peaks,
Aryl azide, (1.0 mmol), terminal alkyne (1.0 mmol), EtOH:H O (1:1,
2
2
mL), Cu–NHC/GO-IL (1 mol% of Cu), 1 h
2
one peak at 399.59 eV ascribed to sp nitrogen in the aro-
a
Isolated yield
matic ring of the NHC–Cu(I) complex and another peak at
4
01.20 eV attributed to the quaternary nitrogen of the IL
[
32]. Cu 2p shows the peaks 932.05 and 951.64 eV which
1
+
Fig. 4b–d, rather than only being located on the edges of the
graphene sheets, the elements such as copper, nitrogen, and
silicon are found to be uniformly dispersed on the whole sur-
face of the NHC–Cu/GO-IL composite, indicating the homo-
geneous distribution of the NHC–Cu and the IL groups.
The TEM image of NHC–Cu/GO-IL composite possesses
similar wrinkled sheet morphology (Fig. 5).
can be attributed to the binding energy of Cu 2p and
3/2
1
+
Cu 2p , respectively. The formation of the NHC–Cu
1
/2
1
+
complex was confirmed by the binding energy Cu 2p
3
/2
value that shifted negatively by 0.3 eV than this value for the
CuI (932.35) [33]. This result may be attributed to the strong
electron-donating effect of the NHC ligand.
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Journal of the Iranian Chemical Society
Table 3 Reusability of the Cu–NHC/GO-IL composite in 1,3- dipolar Huisgen cycloaddition between of ethynylbenzene with azidobenzene
Reaction cycle
1st
93
2nd
93
3rd
93
4th
92
5th
91
6th
91
7th
90
8th
90
9th
89
10th
89
a
Yield (%)
Ethynylbenzene (4 mmol), azidobenzene (4 mmol), EtOH:H O (1:1, 12 mL), 1 h, Cu–NHC/GO-IL (1 mol% of Cu)
2
a
Isolated yield
3
Table 4 Cu–NHC/GO-IL composite catalyzed A -coupling reaction
To optimize the reaction conditions, ethynylbenzene
and azidobenzene were tested as model substrates in vari-
ous solvents (Table 1). The results show both reaction sol-
vent and temperature significantly influencing the product
yield. For comparison, the model reaction was conducted
in GO-IL as a catalyst, which cycloaddition products were
isolated without regioselectivity (Table 1, entry 9).
R1
R2
a
Entry
Yield (%)
2
1
2
3
4
5
6
7
8
9
Ph
Morpholine
Morpholine
Morpholine
Morpholine
Piperidine
Pyrrolidine
Morpholine
Piperidine
97
97
99
75
99
82
78
88
81
4-Cl-Ph
4-NO -C H
4
4-Me-C H
Ph
Ph
n-C H
n-C H
n-C H
With the optimized conditions in hand, the scope of the
reaction was explored by reacting various terminal alkynes
and aryl azides in the mixture of ethanol and water as solvent
at 70 °C, using Cu–NHC/GO-IL composite (1 mol% of Cu)
2
6
6
4
(
Table 2). Aryl ethynyl bearing electron-donating (p-CH )
3
3
7
7
7
and electron-withdrawing (p-CF ) groups reacted well and
3
3
giving good yields (Table 2, entries 3–4). The electron-
Pyrrolidine
3
withdrawing groups (p-Cl and p-NO ) were more reactive
2
than the electron-donating groups (p-CH ) (Table 2, entries
3
Aldehyde (1.0 mmol), secondary amine (1.2 mmol), ethynylben-
2
, 4 and 8).
zene (1.3 mmol), Cu–NHC/GO-IL composite (1 mol% of Cu), H O
2
(
3 mL), 100 °C and 4 h
Isolated yield
The reusability of Cu–NHC/GO-IL composite was tested
a
in Huisgen 1,3-dipolar cycloaddition of ethynylbenzene with
azidobenzene. It was found that the retrieval can be success-
fully achieved in ten successive reaction runs (Table 3). The
SEM image of recycled Cu–NHC/GO-IL composite after
ten cycles shows no change in morphology (Fig. 8). The
possibility of Cu leakage from the catalyst to the medium
during the reaction was investigated. The leaching copper of
After careful investigation of the NHC–Cu/GO-IL com-
posite preparation, it was tested for catalyzing two different
kinds of organic reactions (i) Huisgen 1,3-dipolar cycloaddi-
3
tion for the synthesis of 1,2,3-triazoles, and (ii) A -coupling
reaction.
3
Table 5 Reusability of the Cu–NHC/GO-IL composite in the A -coupling reaction of benzaldehyde, ethynylbenzene, and morpholine
Reaction cycle
1st
97
2nd
97
3rd
95
4th
93
5th
93
6th
90
7th
90
8th
89
9th
89
10th
87
a
Yield (%)
Benzaldehyde (4.0 mmol), morpholine (4.8 mmol), ethynylbenzene (5.2 mmol), Cu–NHC/GO-IL composite (1 mol% of Cu), H O (12 mL),
2
1
00 °C and 4 h
a
Isolated yield
Table 6 Comparison of
Catalyst
Condition
Yield (%)
Time (h)
References
efficiency of various copper
3
catalysts in the A -coupling
Cu–NHC/GO-IL (1 mol%)
CuFAP (12.5 mol%)
H O, 100 °C
97
70
54
65
90
98
4
6
16
8
15
1.5
This work
2
reaction of ethynylbenzene,
MeCN, reflux
34
35
36
22
37
morpholine, and benzaldehyde
Si(CH ) SO CuCl (5 mol%)
H O, 100 °C
2
3
3
2
Nano CuO (10 mol%)
PhCH , 90 °C
3
II
Cu —4 Å (10 mol%)
PhCH , 110 °C
3
MNPs@BiimCu(I) (1.7 mol%)
H O, 100 °C
2
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Journal of the Iranian Chemical Society
catalyst after ten consecutive runs was examined and AAS
results indicated 2.1% of copper leaching after the ten runs.
Inspired by the high activity and stability of Cu–NHC/
Acknowledgements We gratefully acknowledge financial support from
the Research Council of Shahid Beheshti University.
3
Compliance with ethical standards
GO-IL composite, the A coupling reaction was further used
as another model reaction to study further the performance
of Cu–NHC/GO-IL catalyst. The coupling between ethy-
nylbenzene, morpholine, and benzaldehyde was chosen as
Conflict of interest The authors declare no competing financial inter-
est.
a model reaction in H O as solvent at 100 °C and with a
2
catalyst loading of 1 mol% of Cu. Under this condition, the
References
3
A coupling reaction proceeds well, affording the excellent
yield (97%) of the corresponding propargylamine.
1
.
E. Levin, E. Ivry, C.E. Diesendruck, N.G. Lemcoff, Chem. Rev.
115, 4607 (2015)
3
The scope and limitation of A coupling reaction were
2
3
4
.
.
.
E. Hahn, M.C. Jahnke, Angew. Chem. Int. Ed. 47, 3122 (2008)
K.H. Shaughnessy, Chem. Rev. 109, 643 (2009)
J.C.Y. Lin, R.T.W. Huang, C.S. Lee, A. Bhattacharyya, W.S.
Hwang, I.J.B. Lin, Chem. Rev. 109, 3561 (2009)
studied with various types of aldehydes, secondary amines,
and ethynylbenzene. (Table 4). It can be seen from Table 4
3
that the A coupling reaction with most substrates pre-
ceded in good yields. The benzaldehyde-bearing electron-
5. S. Diez-Gonzalez, S.P. Nolan, Aldrichimica Acta 41, 43 (2008)
6
.
S. Gaillard, C.S.J. Cazin, S.P. Nolan, Acc. Chem. Res. 45, 778
withdrawing groups (p-Cl and p-NO ) led to higher yield
2
(2012)
compared to the benzaldehyde-bearing electron-donating
group (p-Me) (Table 4, entries 2–4). Furthermore, the other
secondary amines such as piperidine and pyrrolidine were
7
.
.
S. Gaillard, S.P. Nolan, Acc. Chem. Res. 41, 349 (2008)
S.P. Nolan, Acc. Chem. Res. 44, 91 (2011)
8
9. J.D. Egbert, C.S.J. Cazin, S.P. Nolan, Catal. Sci. Technol. 3, 912
3
(2013)
used in A coupling with ethynylbenzene and benzaldehyde
1
1
1
0. W.J. Sommer, M. Weck, Coord. Chem. Rev. 251, 860 (2007)
1. Y. Zhu, D.K. James, J.M. Tour, Adv. Mater. 24, 4924 (2012)
2. X. Huang, X. Qi, F. Boey, H. Zhang, Chem. Soc. Rev. 41, 666 (2012)
(
Table 4, entries 5 and 6). We used aliphatic aldehyde and
phenylacetylene as model substrates and examined various
3
secondary amines in the A -coupling reaction (Table 4,
13. M.-T. Chen, O. Navarro, Synlett 24, 1190 (2013)
1
4. S. Diez-Gonzalez, A. Correa, L. Cavallo, S.P. Nolan, Alkynes Chem.
Eur. J. 12, 7558 (2006)
entries 7–9).
The reusability of Cu–NHC/GO-IL composite was exam-
1
5. A. Shaygan Nia, S. Rana, D. Döhler, F. Jirsa, A. Meister, L. Guad-
agno, E. Koslowski, M. Bron, W.H. Binder, Chem. Eur. J. 21, 10763
(2015)
3
ined in A coupling between ethynylbenzene, morpholine,
and benzaldehyde. It was found that the recovery can be suc-
cessfully achieved in ten consecutive reaction runs (Table 5).
Table 6 provides a comparison of the present method with
another reported copper heterogeneous catalytic systems in
16. N.I. Kovtyukhova, P.J. Olliver, B.R. Martin, T.E. Mallouk, S.A.
Chizhik, E.V. Buzaneva, A.D. Gorchinsky, Chem. Mater. 11, 771
(1999)
1
7. H. Yang, X. Han, G. Li, Y. Wang, Green Chem. 11, 1184 (2009)
3
the A -coupling reaction of ethynylbenzene, morpholine,
18. H.-W. Bai, Z.-J. Cai, S.-Y. Wang, S.-J. Ji, Org. Lett. 17, 2898 (2015)
1
2
2
2
2
9. A.S. Kumar, M.A. Reddy, M. Knorn, O. Reiser, B. Sreedhar, Eur. J.
and benzaldehyde. Our method is simple, high effective, and
3
Org. Chem. 2013, 4674 (2013)
less time-consuming for the A -coupling reaction.
0. D. Wang, N. Li, M. Zhao, W. Shi, C. Ma, B. Chen, Green Chem. 12,
2120 (2010)
1. M. Dabiri, M. Kasmaei, P. Salari, S.K. Movahed, RSC Adv. 6, 57019
(2016)
Conclusions
2. A. Fodor, Á Kiss, N. Debreczeni, Z. Hell, I. Gresits, Org. Biomol.
Chem. 8, 4575 (2010)
We have demonstrated for the first time that an ionic liq-
uid supported on graphene by grafting a N-heterocyclic
carbene–copper complex on the surface of graphene oxide
modified with ionic liquid is an effective and powerful
support for the immobilization and stabilization of the
copper complex. The as-prepared Cu–NHC/GO-IL com-
posite exhibited a high catalytic activity for the Huisgen
3. H. Naeimi, M. Moradian, Appl. Organomet. Chem. 27, 300 (2013)
24. H. Naeimi, M. Moradian, Asymmetry 25, 429 (2014)
2
5. A. Jorio, M.S. Dresselhaus, R. Saito, G.F. Dresselhaus, Raman Spec-
troscopy in Graphene Related Systems (Wiley-VCH, Berlin, 2011)
6. Q. Zhao, D. Chen, Y. Li, G. Zhang, F. Zhang, X. Fan, Nanoscale 5,
2
882 (2013)
27. S.K. Movahed, N.F. Lehi, M. Dabiri, RSC Adv. 4, 42155 (2014)
28. H.T. Hu, X.B. Wang, F.M. Liu, J.C. Wang, C.H. Xu, Synth. Met.
161, 404 (2011)
1
,3-dipolar cycloaddition of aryl azides and terminal
29. S. Hou, S. Su, M.L. Kasner, P. Shah, K. Patel, C.J. Madarang, Chem.
3
alkynes and the A -coupling reaction of the aldehyde,
alkyne, and the secondary amine in water. Furthermore,
the catalyst was chemically stable and could be recycled
for at least ten times in the corresponding reaction without
the reduction in the catalytic activity.
Phys. Lett. 501, 68 (2010)
30. J.H. Park, F. Raza, S.-J. Jeon, H.-I. Kim, T.W. Kang, D. Yim, J.-H.
Kim, Tetrahedron Lett. 55, 3426 (2014)
3
3
3
0. S.K. Movahed, M. Shariatipour, M. Dabiri, RSC Adv. 5, 33423
(
2015)
1. S.K. Movahed, R. Esmatpoursalmani, A. Bazgir, RSC Adv. 4, 14586
2014)
2. R.P. Vasquez, Surf. Sci. Spectra 2, 149 (1993)
(
1
3

Journal of the Iranian Chemical Society
3
3. B.M. Choudary, C. Sridhar, M.L. Kantam, B. Sreedhar, Tetrahedron
Lett. 45, 7319 (2004)
35. M.L. Kantam, S. Laha, J. Yadav, S. Bhargava, Tetrahedron Lett. 49,
3083 (2008)
34. B. Sreedhar, P.S. Reddy, C.S.V. Krishna, P.V. Babu, Tetrahedron
Lett. 48, 7882 (2007)
36. M. Tajbakhsh, M. Farhang, S.M. Baghbanian, R. Hosseinzadeh,
M. Tajbakhsh, New J. Chem. 39, 1827 (2015)
Affiliations
Minoo Dabiri1 · Seyed Iman Alavioon · Siyavash Kazemi Movahed
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*
Minoo Dabiri
Faculty of Chemistry, Shahid Beheshti University,
Tehran 1983969411, Islamic Republic of Iran
m-dabiri@sbu.ac.ir
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