Heterogeneous azide–alkyne cycloaddition in the presence of a copper catalyst supported on an ionic liquid polymer/silica hybrid material

Article abstract of DOI:10.1002/aoc.4343

Heterogeneous copper catalysts were prepared by the deposition of CuI on a hybrid material consisting of silica and a polymer with imidazolium moieties. The solid materials were characterised using solid-phase NMR, Fourier transform infrared, Raman and X-

Full text of DOI:10.1002/aoc.4343

Received: 5 August 2017
DOI: 10.1002/aoc.4343
Revised: 9 February 2018
Accepted: 12 February 2018
F U L L P A P E R
Heterogeneous azide–alkyne cycloaddition in the presence
of a copper catalyst supported on an ionic liquid polymer/
silica hybrid material
Klaudia Fehér1 | Enikő Nagy1 | Péter Szabó2† | Tatjána Juzsakova3 | Dávid Srankó4 |
Ágnes Gömöry5 | László Kollár6 | Rita Skoda‐Földes1
1 Department of Organic Chemistry, University of Pannonia, Institute of Chemistry, Egyetem u. 10 (PO Box 158), H‐8200 Veszprém, Hungary
2 Department of Analytical Chemistry, University of Pannonia, Institute of Chemistry, Egyetem u. 10 (PO Box 158), H‐8200 Veszprém, Hungary
3 University of Pannonia, Institute of Environmental Engineering, Egyetem u. 10 (PO Box 158), H‐8200 Veszprém, Hungary
4 Department of Surface Chemistry and Catalysis, Hungarian Academy of Sciences, Centre for Energy Research, PO Box 49, H‐1525, Budapest 114,
Hungary
5 Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, H‐1117 Budapest, Hungary
6 Department of Inorganic Chemistry and MTA‐PTE Research Group for Selective Chemical Syntheses, University of Pécs, Ifjúság u. 6 (PO Box 266), H‐
7624 Pécs, Hungary
Correspondence
Heterogeneous copper catalysts were prepared by the deposition of CuI on a
hybrid material consisting of silica and a polymer with imidazolium moieties.
The solid materials were characterised using solid‐phase NMR, Fourier trans-
form infrared, Raman and X‐ray photoelectron spectroscopies and Brunauer–
Emmett–Teller measurements. The formation of copper–carbene complexes
was proved from Raman spectra and the results were supported by density
functional theory calculations. The catalyst could be recycled efficiently with
low loss of copper. Metal leaching was proved to be facilitated by the use of con-
ditions typical for a homogeneous system (the presence of a polar solvent or the
addition of a tertiary amine). Besides simple model reactions, the best catalyst
was found to be suitable for the synthesis of triazoles of more elaborate struc-
ture, such as ferrocene or steroid derivatives.
Rita Skoda‐Földes, University of
Pannonia, Institute of Chemistry,
Department of Organic Chemistry,
Egyetem u. 10 (PO Box 158), H‐8200
Veszprém, Hungary.
Email: skodane@almos.uni‐pannon.hu
Present Address
†Applied Physics, Division of Materials
Science, Department of Engineering
Science and Mathematics, Luleå
University of Technology, 97187 Luleå,
Sweden
Funding information
European Union ‐ European Regional
Development Fund, Grant/Award
Number: GINOP‐2.3.2‐15‐2016‐00049;
National Research, Development and
Innovation Office, Grant/Award Num-
bers: OTKA K120014 and OTKA
K105632; New National Excellence
Program of the Ministry of Human
Capacities, Grant/Award Number:
ÚNKP‐16‐2‐II
KEYWORDS
CuAAC reaction, DFT calculations, Raman spectroscopy, recyclability, triazole
1 | INTRODUCTION
in 2002 and there is still intense ongoing research involv-
ing the improvement of the methodology.
Copper‐catalysed azide–alkyne cycloaddition (CuAAC)
has been one of the most widely used catalytic reactions
in organic synthesis. It was reported independently by
Sharpless and co‐workers[1] and Meldal and co‐workers[2]
The popularity of the CuAAC reaction, the most
widely used representative of the so‐called ‘click’
reactions[3] is mainly due to its robustness, selectivity,
functional group tolerance and biocompatibility that
Appl Organometal Chem. 2018;e4343.
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Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4343

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FEHÉR ET AL.
make it a versatile tool in medicinal chemistry,[4]
bioconjugation[5] and supramolecular chemistry.[6]
such as
a
tetradentate Schiff base ligand,[34]
tris(benzyltriazolylmethyl)amine,[28] (benzimidazoylmethyl)
‐bis(pyridylmethyl)amine[31] and dimethylaminomethyl
groups,[27] as well as quaternary ammonium[29] or
imidazolium ions.[35] At the same time, these catalysts
were evaluated mainly in the cycloaddition reactions of
azides and alkynes with simple aliphatic and aromatic
moieties, with the exception of some carbohydrates[29,36]
and a single example for a steroid derivative.[17]
Under homogeneous conditions, a great variety of cop-
per precursors have been used. The possibilities include
the application of Cu(I) compounds together with a
stabilising ligand or Cu(II) salts in the presence of a reduc-
ing agent to obtain the catalytically active Cu(I) species.[7]
One of the main limitations of homogeneous CuAAC
reactions is the presence of a significant amount of toxic
copper complexes in the end products. Therefore, various
strategies for catalyst removal have been reported.[8] The
advantage of these methods lies not only in obtaining
products with higher purity but also in offering the possi-
bility of catalyst recirculation. The application of ionic liq-
uids as solvents combines the benefits of homogeneous
and heterogeneous reactions. A homogeneous reaction
takes place in the ionic liquid phase but the products
can easily be isolated via extraction and the solvent/cata-
lyst mixture can be recycled.[9] However, this methodol-
ogy has some drawbacks, such as the relatively high
price of the ionic liquids or difficulties in their handling
due to their high viscosity. Another solution is the use of
copper nanostructures[10] that usually have high catalytic
activity but can be recovered only by centrifugation[11,12]
or by the deposition of the active species on magnetic
nanoparticles,[13,14] facilitating separation by the use of
an external magnet. Still, in some cases, efficient recircu-
lation of the catalyst can be achieved only under strictly
inert conditions (in a glovebox) that should be used to
avoid facile oxidation of Cu(I).[13] Excellent results can
be obtained by coating the magnetic nanoparticles with
stabilising ligands, such as 1,3‐di(adamantyl)imidazole,
which ensures small loss of copper (3% of the original
load) and high activity retained in nine cycles.[15]
Besides some rare examples of special copper com-
plexes, e.g. Cu(I)(tris(2‐dioctadecylaminoethyl)amine)Br
that shows unusual solubility‐based thermomorphic prop-
erties in polar solvents that allows recovery of the active
form by simple filtration,[16] the most prevailing solution
for effective catalyst recycling is the immobilisation of
the active species on a solid support, such as char-
coal,[17,18] graphene oxide,[19] alumina,[20] clays[21,22] or
organic/inorganic hybrid materials.[23,24] Among them,
SiO2 with grafted imidazolium cations[24] was proved to
be an excellent support, resulting in a stable catalyst that
could be used several times under solvent‐free conditions.
Biopolymers, such as chitosan,[25,26] and synthetic poly-
mers decorated with suitable ligands to stabilise the cop-
per catalyst[27–35] are also suitable supports. However, a
noticeable decrease of catalytic activity was observed after
the third or fourth run in many cases.[18,21–23,26,32]
Excellent results in catalyst recycling were reported
with polymers incorporating special organic moieties,
As part of our ongoing interest in the functionalisation
of ferrocene[37] and steroid derivatives[38,39] using click
chemistry, we wanted to explore the possibility of using
immobilised copper catalysts for the CuAAC reactions of
such compounds. Ferrocenetriazole derivatives were
proved to be electrochemically detectable receptors for
anions, cations and ion pairs.[40] Steroids bearing triazolyl
moieties often exert biological activity that renders them
interesting targets in pharmaceutical chemistry.[41]
In the present paper, we report the application of an
inorganic/organic hybrid material composed of silica
and a polymer of 1‐methyl‐3‐(4‐vinylbenzyl)imidazolium
chloride as an excellent support for CuAAc reactions of
simple alkynes and azides. The performance of the cata-
lyst in cycloadditions of ferrocene and steroid derivatives
was found to depend strongly on the steric properties of
the starting materials.
2 | EXPERIMENTAL
1H NMR and 13C NMR spectra were recorded in CDCl3,
deuterated dimethylsulfoxide (DMSO‐d6) and D2O with a
Bruker Avance III 500 spectrometer at 500 and
125.7 MHz, respectively. GC–MS analysis was carried out
with a Shimadzu GC–MS‐QP2010SE instrument. High‐
resolution mass spectra of 17α‐(1‐benzyl‐1H‐1,2,3‐triazol‐
4‐yl)estradiol (7ad) and 17α‐(1‐ferrocenylmethyl‐1H‐
1,2,3‐triazol‐4‐yl)estradiol (7bd) were obtained using a Q‐
TOF Premier mass spectrometer (Waters Corporation, Mil-
ford, MA, USA) in positive electrospray ionisation mode.
Fourier transform infrared (FT‐IR) spectra of cycload-
dition products were obtained using a Thermo Nicolet
Avatar 330 FT‐IR instrument. Samples were prepared as
KBr pellets. Elemental analyses were conducted with a
1108 Carlo Erba apparatus. Copper content of the catalysts
and metal leaching values were determined using induc-
tively coupled plasma atomic emission spectroscopy
(ICP‐AES). Conversions were calculated from GC mea-
surements carried out with a Hewlett Packard (HP4890D)
gas chromatograph using ferrocene as internal standard.
FT‐IR spectra for the surface analysis of catalysts were
measured using a Bruker Vertex 70 spectrometer with a
Bruker Platinum ATR adapter without sample

FEHÉR ET AL.
3 of 13
preparation. The spectra were recorded at a resolution of
2 cm−1 with a room temperature DTGS detector and 1024
scans were co‐added. Raman spectra were obtained with
a Bruker SENTERRA Raman microscope. The laser source
was a green semiconductor laser (532 nm) with a maxi-
mum power of 10 mW. For the microscope, a 20× objective
was used. The Raman signal was collected with a
thermoelectrically cooled charge‐coupled device detector
and recorded for typically 20 scans. A typical integration
time for recording the Raman spectra was 30 s on average.
The spectral resolution was 4 cm−1. Density functional the-
ory (DFT) with B3LYP and PBE0 functional and
LANL2DZ basis set was used for geometry optimisation
and frequency analysis of [Cu(DMim)]I (DMim = N,N′‐
dimethylimidazol‐2‐ylidene), used as a model for the vibra-
tional analysis of Cu–carbenes on the ground‐state (singlet
spin state) potential energy surface. All calculations were
performed using the Gaussian 09 program.
Surface composition of fresh and spent catalysts was
determined using X‐ray photoelectron spectroscopy
(XPS) performed with a KRATOS XSAM 800 XPS
machine equipped with an atmospheric reaction cham-
ber. Al Kα characteristic X ray line, 40 eV pass energy
(energy steps of 0.1 eV) and FAT mode were applied for
recording the XPS lines of Cu 2p, Cu LMM, O 1 s, N 1 s,
C 1 s and Si 2p. C 1 s binding energy at 284.8 eV was used
as reference for charge compensation. The surface con-
centrations of the elements were calculated from the inte-
gral intensities of the XPS lines using sensitivity factors
given by the instrument manufacturer.
The specific surface area, pore volume and pore size
distribution in micropore (1.7–2 nm), mesopore (2–
50 nm) and macropore (50–100 nm) diameter ranges of
silica and support 4 were determined using nitrogen
adsorption/desorption at −196 °C measured with a
Micromeritics ASAP 2000‐type instrument on samples
previously outgassed overnight in vacuum at 60 °C. The
surface areas of the samples (SBET) were determined using
the Brunauer–Emmett–Teller (BET) method from the
nitrogen adsorption isotherm. The pore volume values
were calculated from the nitrogen desorption isotherms
using the Barrett–Joyner–Halenda (BJH) theory.
formed as a yellow viscous liquid (yield: 94%). Its NMR
data corresponded well to those reported in the
literature.[42]
1H NMR (D2O, δ, ppm): 8.65 (s, 1H); 7.45 (d,
J = 7.9 Hz, 2H); 7.36 (brs, 1H); 7.34 (brs, 1H); 7.29 (d,
J = 7.9 Hz, 2H); 6.69 (dd, J = 11.0 Hz, 17.5 Hz, 1H); 5.79
(d, J = 17.5 Hz, 1H), 5.28 (s, 2H, CH2); 5.27 (d,
J = 11.0 Hz, 1H); 3.78 (s, 3H, CH3). 13C NMR (D2O, δ,
ppm): 138.4; 135.9 (2C); 133.2; 129.0; 127.0; 123.8; 122.3;
115.5; 52.6; 35.8.
2.2 | Preparation of Support 4
Ionic liquid monomer 3 (400 mg), silica (1.00 g, particle
size 60–200 μm, pre‐treated by heating for 8 h at
220 °C), dichloromethane (5 ml) and
5 mg of
azobisisobutyronitrile were refluxed under an inert
atmosphere at 60 °C for 5 h. The solvent was removed
in vacuo. Then 8 ml of acetonitrile was added, the mix-
ture was refluxed for 5 h and then the solvent was
removed. This procedure was repeated five times and
then the solid phase was filtered and dried under
reduced pressure to afford 1.2 g of support 4 as an off‐
white powder.
2.3 | Preparation of Catalysts CAT‐1–CAT‐4
CAT‐1: a mixture of 4 (120 mg), CuI (0.14 mmol, 26 mg)
and 4 ml of acetonitrile–dimethylformamide (1,1) was
stirred under inert atmosphere for 24 h. The solid material
was filtered off under an inert atmosphere, washed with
acetone, methanol, tetrahydrofuran (THF) and diethyl
ether, and dried under reduced pressure. The catalyst
was obtained as a pale green solid.
CAT‐2–CAT‐4: a mixture of 4 (120 mg), CuI (0.2 mmol,
38 mg for CAT‐2, 0.1 mmol, 19 mg for CAT‐3, 0.05 mmol,
10 mg for CAT‐4), tBuOK (0.2 mmol, 22.4 mg) and THF
(1 ml) was stirred under an inert atmosphere for 4 h.
The solid material was filtered off under inert atmo-
sphere, washed with cold methanol, acetone–methanol
(1,1) and acetone, and dried under reduced pressure. Each
catalyst was obtained as a pale green solid.
2.1 | Preparation of 1‐Methyl‐3‐(4‐
vinylbenzyl)‐1H‐imidazolium Chloride
(3)[42]
2.4 | General Procedure for CuAAC
A mixture of catalyst (with 0.01 mmol Cu content),
0.1 mmol of alkyne and 0.1 mmol of azide was stirred in
CH2Cl2 (1 ml) at room temperature under inert atmo-
sphere until total conversion of the starting material could
be detected by GC. The catalyst was allowed to settle and
then the solution was removed using a syringe. The
catalyst was reused without any treatment; a new portion
of the reactants and the solvent were added. The
In a Schlenk tube, 1‐methylimidazole (1; 1.7 mmol, 135.5
μl), 4‐vinylbenzyl chloride (2; 1.75 mmol, 246.6 μl) and
dichloromethane (10 ml) were refluxed under inert
atmosphere at 60 °C for 5 h. The solvent was evaporated
under reduced pressure. The product was washed with
diethyl ether and dried in vacuo. Ionic liquid 3 was

4 of 13
FEHÉR ET AL.
cycloaddition was carried out in 3–10 consecutive runs.
The products were purified by column chromatography
(silica; eluent: toluene–EtOAc).
1.2 Hz, 1H); 5.33 (s, 2H); 4.31 (t, J = 1.7 Hz, 2H); 4.23
(t, J = 1.7 Hz, 2H); 4.20 (s, 5H). 13C NMR (CDCl3, δ,
ppm): 147.7; 130.7; 128.8; 128.1; 125.7; 118.9; 80.8; 69.1;
69.0 (7C); 50.1. FT‐IR (KBr, cm−1): 1462; 1332; 1221;
1103; 1070; 1050; 817; 764; 690. MS (m/z/rel.int.): 343
(M+)/43; 281/11; 253/11; 209/12; 208/16; 200/16; 199/95;
133/12; 121/100; 119/10; 96/17; 89/14; 73/13; 56/42; 44/
21. Anal. Calcd for C19H17FeN3 (%): C, 66.49; H, 4.99; N,
12.24. Found (%): C, 66.61; H, 5.05; N, 12.37. Yellow solid;
m.p. 178–182 °C; yield 52%.
Methyl 1‐ferrocenylmethyl‐1H‐1,2,3‐triazole‐4‐carbox-
ylate (7bb). 1H NMR (CDCl3, δ, ppm): 7.96 (s, 1H); 5.34 (s,
2H); 4.27 (s, 2H); 4.24 (s, 2H); 4.19 (s, 5H); 3.91 (s, 3H,
―OCH3). 13C NMR (CDCl3, δ, ppm): 161.2; 139.8; 126.8;
79.8; 69.4; 69.0; 69.0; 52.1; 50.5. FT‐IR (KBr, cm−1):
1724; 1536; 1454; 1430; 1336; 1225; 1046; 1017; 776; 715;
694. MS (m/z/rel.int.): 325 (M+)/6; 281/13; 253/10; 209/
13; 208/17; 199/16; 191/9; 133/14; 121/15; 96/22; 73/22;
44/100. Anal. Calcd for C15H15FeN3O2 (%): C, 55.41; H,
4.65; N, 12.92. Found (%): C, 55.32; H, 4.81; N, 12.71. Yel-
low solid; m.p. 169–171 °C; yield 93%.
(1‐Ferrocenylmethyl‐1H‐1,2,3‐triazol‐4‐yl)methyl ace-
tate (7BC). 1H NMR (CDCl3, δ, ppm): 7.49 (s, 1H); 5.27 (s,
2H); 5.15 (s, 2H); 4.27 (t, J = 1.6 Hz, 2H); 4.21 (t,
J = 1.6 Hz, 2H); 4.17 (s, 5H); 2.03 (s, 3H). 13C NMR (CDCl3,
δ, ppm): 170.9; 142.7; 123.0; 80.6; 69.1; 69.0; 69.0; 57.6;
50.1; 20.9. FT‐IR (KBr, cm−1): 1736; 1446; 1368; 1230;
1050; 813; 792. MS (m/z/rel.int.): 339 (M+)/25; 281/16;
208/16; 199/42; 191/9; 133/10; 121/42; 96/16; 73/20; 56/
17; 44/100; 43/16. Anal. Calcd for C16H17FeN3O2 (%): C,
56.66; H, 5.05; N, 12.39. Found (%): C, 56.77; H, 4.92; N,
12.55. Yellow solid; m.p. 74–76 °C; yield 92%.
17α‐(1‐Ferrocenylmethyl‐1H‐1,2,3‐triazol‐4‐yl)estra-
diol (7bd). 1H NMR (DMSO‐d6, δ, ppm): 9.02 (s, 1H); 7.83
(s, 1H); 6.95 (d, J = 8.5 Hz, 1H); 6.47 (dd, J = 8.5 Hz,
2.3 Hz, 1H); 6.41 (d, J = 2.3 Hz, 1H); 5.28 (s, 2H); 5.12
(s, 1H); 4.35 (s, 1H); 4.32 (s, 1H); 4.18 (s, 7H); 0.59–2.76
(m, 15H, ring protons); 0.91 (s, 3H). 13C NMR (DMSO‐
d6, δ, ppm): 155.4; 154.6; 137.6; 130.8; 126.4; 122.7;
115.4; 113.1; 83.3; 81.6; 69.1; 69.0; 69.0; 68.7; 49.2; 48.0;
47.1; 43.7; 39.8; 37.7; 33.1; 29.7; 27.7; 26.5; 24.0;14.9. FT‐
IR (KBr, cm−1): 1609; 1503; 1442; 1287; 1234; 1053; 813.
HRMS calculated for C31H35N3O2Fe 537.2079, found
537.2076. Yellow solid; m.p. 231–236 °C; yield 26%.
17α‐Hydroxy‐16β‐(4‐phenyl‐1,2,3‐triazol‐1‐yl)‐5α‐
2.5 | Characterisation of Products
1‐Benzyl‐4‐phenyl‐1H‐1,2,3‐triazole (7aa).[43] 1H NMR
(CDCl3, δ, ppm): 7.80 (dd, J = 8.5 Hz, 1.3 Hz, 2H); 7.66 (s,
1H); 7.41–7.36 (m, 5H); 7.33–7.30 (m, 3H); 5.57 (s, 2H,
―CH2). 13C NMR (CDCl3, δ, ppm): 148.2; 134.7; 130.6;
129.2; 128.8; 128.8; 128.2; 128.1; 125.7; 119.5; 54.2. FT‐IR
(KBr, cm−1): 1467; 1454; 1356; 1217; 1070; 1041; 764; 727;
690. MS (m/z/rel.int.): 235 (M+)/7; 206/19; 116/49; 91/52;
89/16; 65/13; 44/100; 39/11. Anal. Calcd for C15H13N3
(%): C, 76.57; H, 5.57; N, 17.86. Found (%): C, 76.91; H,
5.42; N, 17.91. White solid; m.p. 124–127 °C; yield 99%.
Methyl
1‐benzyl‐1H‐1,2,3‐triazole‐4‐carboxylate
(7ab).[43] 1H NMR (CDCl3, δ, ppm): 7.97 (s, 1H); 7.42–
7.36 (m, 3H); 7.31–7.27 (m, 2H); 5.57 (s, 2H); 3.92 (s,
3H). 13C NMR (CDCl3, δ, ppm): 161.1; 140.3; 133.7;
129.3; 129.2; 128.3; 127.3; 54.5; 52.2. FT‐IR (KBr, cm−1):
1723; 1536; 1454; 1430; 1336; 1225; 1045; 1017; 776; 715;
694. MS (m/z/rel.int.): 217 (M+)/1; 174/14; 130/21; 91/
100; 65/19. Anal. Calcd for C11H11N3O2 (%): C, 60.82; H,
5.10; N, 19.34. Found (%): C, 60.71; H, 5.32; N, 19.45.
White solid; m.p. 99–102 °C; yield 78%.
(1‐Benzyl‐1H‐1,2,3‐triazol‐4‐yl)methyl
acetate
(7 ac).[44] 1H NMR (CDCl3, δ, ppm): 7.51 (s, 1H); 7.37–
7.33 (m, 3H); 7.27–7.26 (m, 2H); 5.50 (s, 2H); 5.16 (s,
2H); 2.03 (s, 3H). 13C NMR (CDCl3, δ, ppm): 170.8;
143.2; 134.4; 129.1; 128.9; 128.2; 123.6; 57.6; 54.2; 20.9.
FT‐IR (KBr, cm−1): 1740; 1454; 1433; 1225; 1053; 1033;
760; 719. MS (m/z/rel.int.): 231 (M+)/2; 188/11; 92/13;
91/100; 65/25; 43/58; 39/12. Anal. Calcd for C12H13N3O2
(%): C, 62.33; H, 5.67; N, 18.17. Found (%): C, 62.41; H,
5.83; N, 18.22. Colourless oil; yield 71%.
17α‐(1‐Benzyl‐1H‐1,2,3‐triazol‐4‐yl)estradiol (7ad).[45]
1H NMR (DMSO‐d6, δ, ppm): 8.97 (s, 1H); 7.89 (s, 1H);
7.40–7.37 (m, 2H); 7.35–7.31 (m, 3H); 6.96 (d, J = 8.5 Hz,
1H); 6.47 (dd, J = 8.5 Hz, 2.3 Hz, 1H); 6.42 (d, J = 2.3 Hz,
1H); 5.59 (d, J = 15.0 Hz, 1H); 5.56 (d, J = 15.0 Hz, 1H);
5.11 (s, 1H); 0.57–2.78 (m, 15 H, ring protons), 0.92 (s,
3H). 13C NMR (DMSO‐d6, δ, ppm): 155.4; 154.9; 137.6;
136.8; 130.9; 129.2; 128.5; 128.3; 126.5; 123.3; 115.4;
113.1; 81.6; 53.1; 48.1; 47.2; 43.7; 39.8; 37.7; 33.1; 29.7;
27.7; 26.5; 24.0; 14.8. FT‐IR (KBr, cm−1): 1605; 1495;
1454; 1442; 1221; 1062; 1013; 866; 715. HRMS calculated
for C27H32N3O2 430.2495 ([M + H]+), found 430.2496.
White solid; m.p. 218–219 °C; yield 56%.
androstane (7ca).[39] 1H NMR (CDCl3, δ, ppm): 7.81–7.80
(m, 3H); 7.40 (t, J = 7.4 Hz, 2H); 7.32 (t, J = 7.4 Hz, 1H);
4.63 (t, J = 8.8 Hz, 1H); 4.06 (brs, 1H); 2.78–2.98 (brs, 1H);
0.74–2.46 (m, 22 H); 0.93 (s, 3H, 18‐H3); 0.81 (s, 3H, 19‐
H3). 13C NMR (CDCl3, δ, ppm): 147.5; 130.6; 128.8;
128.1; 125.7; 119.6; 85.4; 70.2; 54.2; 49.4; 46.9; 44.5; 38.7;
36.4; 35.0; 32.7; 32.4; 31.9; 29.0; 28.9; 26.8; 22.2; 20.0;
18.0; 12.2. FT‐IR (KBr, cm−1): 3423; 2917; 2848; 1458;
1‐Ferrocenylmethyl‐4‐phenyl‐1H‐1,2,3‐triazole (7ba).
1H NMR (CDCl3, δ, ppm): 7.79 (dd, J = 8.3 Hz, 1.4 Hz,
2H); 7.64 (s, 1H); 7.41–7.38 (m, 2H); 7.30 (tt, J = 7.4 Hz,

FEHÉR ET AL.
5 of 13
1385; 1225; 1074; 1053; 976; 764; 686. MS (m/z/rel.int.):
419 (M+)/15; 391/11; 376/12; 173/19; 161/9; 148/12; 147/
10; 146/22; 145/100; 144/18; 119/11; 117/14; 116/9; 109/
24; 108/13; 107/10; 105/15; 104/25; 102/19; 95/20; 93/18;
91/20; 81/23; 79/19; 77/9; 67/29; 55/32; 44/17; 43/15; 41/
19. Anal. Calcd for C27H37N3O (%): C, 77.29; H, 8.89; N,
10.01. Found (%): C, 77.12; H, 9.01; N, 10.13. White solid;
m.p: 232–234 °C; yield 46%.
3 | RESULTS AND DISCUSSION
3.1 | Preparation and Characterisation of
Catalysts
As polymers incorporating quaternary ammonium[29]
and imidazolium ions[35] had been found to stabilise
copper catalysts efficiently, copper was deposited on a
support (4) obtained by the radical polymerisation of 3,
prepared by the reaction of 1 and 2 (Scheme 1).[42]
During the first catalytic experiments, we encountered
difficulties in the separation of the catalyst that could
be recovered only by centrifugation. To solve this
problem, polymerisation was carried out in the presence
of silica gel. The process led to a solid material that could
be removed from the reaction mixture by simple filtration
or decantation. The solid material was characterised
using 13C CP MAS NMR and FT‐IR spectroscopies. The
13C CP MAS NMR spectrum (Figure 1) shows the
presence of saturated carbon atoms in the region of
36–52 ppm and signals corresponding to carbon atoms
of the phenyl and imidazolium rings between 124 and
146 ppm.
The values of the specific surface area (SBET) and pore
volumes of silica and support 4 were determined from the
experimental data of their nitrogen adsorption/desorption
isotherms (Table 1). The silica used was a mesoporous
material with pore size between 2 and 10 nm. This struc-
ture was preserved in support 4. Although the BET surface
area and total pore volume of the hybrid material 4 are
lower than those of the original silica support due to depo-
sition of the modifying material, no considerable change
was observed in the average pore diameter after the poly-
merisation reaction.
17α‐Hydroxy‐16β‐(4‐(methoxycarbonyl)‐1H‐1,2,3‐
triazol‐1‐yl)‐5α‐androstane (7cb).[39] 1H NMR (CDCl3, δ,
ppm): 8.21 (s, 1H); 4.69 (t, J = 9.1 Hz, 1H); 4.06 (brs, 1H);
3.93 (s, 3H); 3.04–3.31 (brs, 1H); 0.73–2.46 (m, 22 H, ring
protons); 0.89 (s, 3H, 18‐H3); 0.81 (s, 3H, 19‐H3). 13C
NMR (CDCl3, δ, ppm): 161.2; 139.5; 127.3; 85.2; 70.4; 54.1;
52.1; 49.3; 46.9; 44.6; 38.6; 36.3; 34.9; 32.7; 32.3; 31.7; 28.9;
28.7; 26.7; 22.1; 19.9; 17.9; 12.1. FT‐IR (KBr, cm−1): 3391;
2921; 2852; 1723; 1532; 1442; 1377; 1230; 1070; 1050;
817; 776. MS (m/z/rel.int.): 401 (M+)/2; 358/11; 315/20;
314/73; 281/11; 275/14; 274/67; 259/27; 218/16; 203/18;
175/15; 161/10; 155/18; 154/13; 149/11; 148/24; 147/14;
135/16; 133/13; 128/50; 127/100; 122/12; 121/17; 119/13;
116/11; 110/16; 109/45; 108/30; 107/22; 105/20; 97/18; 96/
69; 95/60; 94/15; 93/34; 91/30; 83/23; 82/13; 81/44; 80/12;
79/36; 77/15; 69/21; 68/25; 67/60; 57/10; 55/64; 54/9; 53/
22; 44/27; 43/27; 41/45. Anal. Calcd for C23H35N3O3
(%): C, 68.80; H, 8.79; N, 10.46. Found (%): C, 68.85; H,
8.57; N, 10.59. White solid; m.p. 182–188 °C; yield 79%.
16β‐(4‐(Acetoxymethyl)‐1H‐1,2,3‐triazol‐1‐yl)‐17α‐
hydroxy‐5α‐androstane (7 cc).[39] 1H NMR (CDCl3, δ,
ppm): 7.66 (s, 1H); 5.19 (s, 2H); 4.59 (ddd, J = 8.4 Hz,
7.2 Hz, 0.8 Hz, 1H); 4.02 (d, J = 0.8 Hz, 1H); 2.44–2.59
(brs, 1H); 0.73–2.44 (m, 22 H); 2.06 (s, 3H); 0.90 (s, 3H,
18‐H3); 0.80 (s, 3H, 19‐H3). 13C NMR (CDCl3, δ, ppm):
171.0; 142.6; 123.6; 85.3; 70.0; 57.7; 54.2; 49.3; 47.0; 44.5;
38.7; 36.4; 35.0; 32.8; 32.4; 31.9; 29.0; 28.8; 26.7; 22.1; 20.9;
20.0; 18.0; 12.2. FT‐IR (KBr, cm−1): 3440; 2917; 2852;
1740; 1458; 1442; 1385; 1274; 1237; 1057; 1033; 829. MS
(m/z/rel.int.): 415 (M+)/2; 328/12; 327/28; 312/9; 284/20;
169/11; 148/10; 142/22; 135/12; 121/12; 110/12; 109/34;
108/14; 107/14; 105/16; 98/14; 96/13; 95/28; 93/28; 91/21;
84/12; 83/14; 82/35; 81/85; 80/49; 79/29; 77/10; 73/11; 70/
10; 69/21; 68/31; 67/52; 57/13; 56/15; 55/58; 54/18; 53/14;
43/100; 41/40; 39/10. Anal. Calcd for C24H37N3O3 (%): C,
69.37; H, 8.97; N, 10.11. Found (%): C, 69.12; H, 8.78; N,
10.01. White solid; m.p. 131–134 °C; yield 73%.
Copper was immobilised on the surface of support 4
using CuI as the precursor. The catalysts were obtained
in the absence (CAT‐1) and in the presence of tBuOK
(CAT‐2–CAT‐4; Table 2). This base had been used before
during the preparation of similar catalysts to facilitate
carbene formation from the imidazolium ion,[24,46] which
might act as a ligand to form copper–N‐heterocyclic
carbene complexes. The copper content of the catalysts
was determined by ICP‐AES. In the presence of tBuOK,
a higher amount of copper could be immobilised under
identical conditions (Table 2; CAT‐1 and CAT‐2), so two
SCHEME 1 Preparation of organic/
inorganic hybrid support (4)

6 of 13
FEHÉR ET AL.
change when compared to the spectrum of the silica/
polymer hybrid material. As an example, the 13C CP
MAS NMR spectrum of CAT‐2 is presented in Figure 1.
Poly(1‐methyl‐3‐(4‐vinylbenzyl)imidazolium chloride)
(Pol), support 4 and CAT‐1, obtained from CuI without
the addition of tBuOK, as well as the catalyst with the
lowest copper content (CAT‐4) gave very similar FT‐IR
spectra (Figure 2). At the same time, a considerable
broadening of bands could be observed in case of CAT‐2,
and a splitting of some of the bands corresponding to
the imidazolium moiety (at 1450 and 1420 cm−1) could
be detected in the spectrum of CAT‐3.
Surface composition of CAT‐2 and CAT‐3 was
determined using XPS measurements (Tables 3 and 4).
(The survey scans of the samples before and after the cat-
alytic reaction are shown in Figure S2.) Strong lines
related to oxygen, carbon and silicon are present in the
spectra with weaker signs of copper, nitrogen, iodine
and potassium.
The binding energy of the Si 2p peak was assigned to
oxides (CAT‐2: Si 2p3/2 = 103.5 eV; CAT‐3: Si 2p3/2 = 102.9 eV).
FIGURE 1 13C CP MAS NMR spectra of support 4 (above) and
CAT‐2 (below) (* indicates a rotational sideband)
TABLE 1 Surface area (SBET), pore volume (V) and average pore
diameter (D) of silica and support 4
SBET (m2 g−1
)
V (cm3 g−1
)
D (nm)a
Silica
507
291
0.7162
0.4267
4.66
4.59
Support 4
aBJH desorption average pore diameter.
TABLE 2 Preparation of catalysts CAT‐1–CAT‐4a
Catalyst
CuI (mmol)
tBuOK
Cu content (mol%)b
CAT‐1c
CAT‐2d
CAT‐3d
CAT‐4d
0.2
−
+
+
+
3.5
10.3
3.1
0.2
0.1
0.05
1.2
aReaction conditions: 120 mg support (4), CuI, 24 h, room temperature.
bDetermined by ICP.
cSolvent: CH3CN–dimethylformamide (1:1) (4 ml).
dSolvent: THF (1 ml), tBuOK (0.2 mmol).
catalysts with lower copper content (CAT‐3 and CAT‐4)
were also prepared.
FIGURE 2 FT‐IR spectra of support 4 and fresh and spent
catalysts (Pol: poly(1‐methyl‐3‐(4‐vinylbenzyl)imidazolium
chloride) prepared in the absence of silica)
Except for some broadening of the signals, the 13C CP
MAS NMR spectra of the catalysts did not show any

FEHÉR ET AL.
7 of 13
TABLE 3 XPS surface composition of CAT‐2
Binding energy (eV)
Surface concentration (at.%)
Element/component
peak
Fresh
Spent
Chemical state
Fresh
Spent
Cu 2p
932.5
933.8
619.1
530.6
532.8
400.8
284.8
283.0
286.4
292.9
103.5
932.6
933.8
619.5
530.8
533.1
401.4
284.8
283.2
286.4
292.9
103.5
Cu(I)
1.6
1.5
Cu(II)
10.5
1.1
6.0
I 3d
I−
0.9
O 1 s
Cu2O, CuO, O=C
SiO2 (C–OH (aliphatic))
Organic nitrogen species
C–C, C–H
15.6
33.3
3.6
9.1
39.5
4.0
N 1 s
C 1 s
15.9
3.7
15.9
3.0
C–Cu (C–O–Cu)
C–O, C–N, C=N
K+
1.3
6.1
K 2p
Si 2p
0.7
0.6
SiO2
12.6
13.2
TABLE 4 XPS surface composition of CAT‐3
Binding energy (eV)
Surface concentration (at.%)
Element/component
peak
Fresh
Spent
Chemical state
Fresh
Spent
Cu 2p
932.9
934.0
619.1
530.6
532.5
400.6
284.8
282.5
286.5
293.3
102.9
932.9
934.0
619.0
530.1
532.6
400.7
284.8
282.9
286.3
293.2
103.2
Cu(I)
0.2
0.3
Cu(II)
3.9
2.3
I 3d
I−
0.2
0.1
O 1 s
Cu2O, CuO, O=C
SiO2 (C–OH (aliphatic))
Organic nitrogen species
C–C, C–H
9.0
4.6
48.4
2.9
49.8
2.9
N 1 s
C 1 s
14.0
0.3
14.2
1.1
C–Cu (C–O–Cu)
C–O, C–N, C=N
K+
3.2
5.1
K 2p
Si 2p
1.0
0.9
SiO2
17.0
18.7
The surface modification did not cause major changes
in chemical states.[46] The dominant part of the copper
content was determined as Cu(II) chemical state by the
position of the Cu 2p line at 933.8 eV and the presence
of the characteristic ‘shake up’ satellite structure. The
minor part of the copper can be either in Cu(0) or Cu(I)
chemical state according to the line position at ca
932.5 eV.[47] Considerable amount of oxygen can be
assigned to the SiO2 phase with the O 1 s binding energy
at ca 532.8 eV.[48] The spectral line appearing at lower
binding energy of ca 530.6 eV is typical of C―O or oxygen
in CuO state (ca 530.6 eV) but it can also be a mixture of
oxygen in both Cu2O and CuO states.[49] The lines
appearing at ca 619.1 eV are assigned to I 3d and therefore
to the presence of iodine (ca 1 at.%).[47] It is assumed that
in spite of the inert conditions, some oxygen might have
remained in the pores of silica gel that could not be
removed completely. A small amount of potassium can
be detected as well. While there seems to be a correlation
between the amount of iodine and the Cu(I) ratio in the
CAT‐2 and CAT‐3 samples (i.e. less copper and less
iodine), there is no significant change in the amount of
potassium with different copper loading. Due to the pres-
ence of the polymeric phase, there is a significant carbon
content of the samples. The peak at 284.8 eV can be
assigned to C―C/C―H bonds, while the peak at
286.4 eV is typical for carbon in C―O as well as for
C―N and C―N bonds.[50–52] The peak appearing at ca
283 eV can be related to the formation of C―Cu
(or C―O―Cu bonds by analogy with C―O―Ag in

8 of 13
FEHÉR ET AL.
metal–polymer composite[53]). There is also a correlation
between the strength of the line at 283 eV and the copper
content of the samples, i.e. the smaller the copper content
the weaker the line appearing at 283 eV. Nitrogen content
was detected at peak energies that are typical for an
organic environment. The peak at ca 400.8 eV is assigned
to N 1 s in organic nitrogen species.[54]
Although the formation of copper–N‐heterocyclic
carbene complexes could not be proved by 13C NMR spec-
troscopy, possibly because of a low concentration in the
sample, Raman measurements (Figure 3; Table 5)
together with DFT calculations (Table 5) supported the
presence of such species in the case of CAT‐2. Upon com-
paring the spectra of CuI and CAT‐2, considerable differ-
ences can be observed in the frequencies of Cu―I
stretching (118 cm−1 for CuI and 138 cm−1 for CAT‐2)
and Cu―I bending (73 cm−1 for CuI and 89 cm−1 for
CAT‐2) indicating complexation.
An appreciable change can be detected in the frequen-
cies involving vibrations of the imidazole moiety. (For
comparison, Figure 3 includes the Raman spectra of the
polymeric support and 1‐methylimidazole.) Good agree-
ment can be observed between the experimental data for
CAT‐2 and the calculated frequencies of a [Cu(DMim)]I
complex. (Table 5 presents only the vibrations in which
Cu is involved.) The most prominent peaks in the spec-
trum of CAT‐2 correspond to Cu―C (Cu–carbene)
stretching (above 1000 cm−1) and Cu―C (Cu–carbene)
bending (below 1000 cm−1).
TABLE 5 Experimental data obtained for CAT‐2 sample and
calculated frequencies of Raman‐active modes of [Cu(DMim)]I
Frequency (cm−1
)
Raman‐
active
modea
Calculated for [Cu(DMim)]I
Experimental
(CAT‐2)
(B3LYP)
(PBE0)
ν1 (C)
ν2 (B)
ν3 (A)
ν4 (B)
ν5 (B)
ν6 (B)
ν7 (B)
ν8 (B)
ν9 (A)
ν10 (A)
ν11 (A)
ν12 (A)
138
145
147
276
270
274
310
355
362
471
453
459
634
611
627
685
672
669
797
747
764
970
1018
1114
1152
1348
1391
1035
1121
1168
1382
1426
1020
1166
1292
1420
aA: [Cu–imidazole] stretching; B: [Cu–imidazole] bending; C: [Cu–iodine]
stretching.
3.2 | Catalytic Reactions
The catalysts were evaluated in the cycloaddition reaction
of phenylacetylene (5a) with benzyl azide (6a) (Scheme 2).
Reaction times required for quantitative conversion of
substrate 5a were estimated by GC. The results are
summarised in Table 6.
Catalysts CAT‐1 and CAT‐2 showed similar catalytic
activity under identical conditions (Table 6, entries 1–4).
In the absence of the base, much longer reactions were
necessary to achieve total conversion, but copper leaching
decreased considerably. (Although the exact amount of
copper in the filtrate was not determined in the first
experiment (entry 1), the green colour of the reaction mix-
ture clearly indicated a considerable loss of the metal.) As
acetonitrile is a strongly coordinating solvent and may
facilitate the loss of copper,[28] the possibility of using
other reaction media was also taken into account. How-
ever, much lower conversion could be achieved in ethanol
or THF, with conversions of 50 and 90%, respectively,
FIGURE 3 Raman spectra of poly(1‐methyl‐3‐(4‐vinylbenzyl)
imidazolium chloride) (Pol), CuI, 1‐methylimidazole (Mim) and
CAT‐2
SCHEME 2 Azide–alkyne cycloaddition of phenylacetylene (5a)
with benzyl azide (6a)

FEHÉR ET AL.
9 of 13
TABLE 6 Efficiency of catalysts in cycloaddition of phenylacetylene (5a) with benzyl azide (6a)a
Entry
Catalyst
Solvent
Base
Reaction time required for quantitative conversion (h)
Cu leaching (%)b
1
CAT‐1
CAT‐1
CAT‐2
CAT‐2
CAT‐2
CAT‐2
CAT‐2
CAT‐3
CH3CN
CH3CN
CH3CN
CH3CN
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
+
−
+
−
−
−
−
−
14
48
17
48
96
72
7
n.d.
8.7
2
3
8.2
4
4.3
5
0.8
6c
7d
8
3.7
11.5
<0.14
24
aReaction conditions 0.1 mmol 5a, 0.1 mmol 6a, base (0.1 mmol DIPEA), catalyst (with 0.01 mmol Cu content), 1 ml solvent, room temperature.
bmol% of the original load of Cu, determined by ICP.
c0.1 mmol 5a, 0.1 mmol 6a, catalyst (with 0.02 mmol Cu content), 1 ml solvent, room temperature.
dReflux.
after five days. A slow reaction took place also in dichloro-
methane with a total conversion only after four days
(entry 5), but the amount of leached copper decreased
noticeably.
An increase in the copper‐to‐substrate ratio (entry 6)
and especially the use of a higher temperature (entry 7)
led to a decrease in the necessary reaction time, but it
was accompanied by a higher loss of copper. Both changes
in the reaction conditions may lead to a higher concentra-
tion of copper nanoparticles in the liquid phase that may
result in enhanced aggregation that might prevent resorp-
tion of the metal particles on the surface and lead to
higher degree of leaching.
To achieve a better stabilisation of copper, a catalyst
with a lower copper‐to‐support ratio was prepared
(Table 2, CAT‐3). In the presence of CAT‐3, the starting
materials were fully converted to the product (7a) in
24 h. Besides, copper leaching was below the detection
limit (Table 6, entry 8). A further reduction in the amount
of immobilised Cu (CAT‐4, Table 2) led to a dramatic
decrease in catalytic activity resulting in only 51% conver-
sion after 120 h.
FT‐IR spectra (Figure 2) and surface composition of
spent catalysts (CAT‐2, obtained from an experiment car-
ried out according to Table 6, entry 5 (Table 3); CAT‐3,
obtained from an experiment carried out according to
Table 6, entry 8 (Table 4)) were compared to the data for
the freshly prepared ones. In the case of CAT‐3, there is
no change in the FT‐IR spectrum after the catalytic reac-
tion, but the presence of some triazole product can be
detected in the spectrum of spent CAT‐2. It is assumed
that because of the higher copper content of this catalyst
some Cu–triazole complexes might be formed. An
increase in the amount of surface nitrogen species could
be detected also by XPS (Table 3). Interestingly, a
considerable decrease in the surface concentration of
Cu(II) could be noticed in the case of both catalysts. At
the same time, ICP‐AES data showed no change in the
copper content of spent CAT‐3 catalyst, indicating a rear-
rangement of the surface of the catalyst during the reac-
tion. It should also be noted that the surface
concentration of Cu(I) did not change considerably dur-
ing the reaction with CAT‐2 (Table 3) and even an
increase could be observed in the case of CAT‐3
(Table 4).
Presumably, the hard Pearson acid Cu(II) is able to
enter the pores of silica (characterised as O‐rich hard
Pearson base ‘ligand surroundings’), while the soft Pear-
son acid Cu(I) is not. Cu(II) is expected to form more sta-
ble complexes with ‘hard’ silica than the ‘soft’ Cu(I).
To obtain information about the homogeneous or het-
erogeneous nature of the leached species, mercury poising
tests were carried out for some reactions of CAT‐2 and
CAT‐3 (Table 7). The catalytic mixtures were filtered after
a couple of hours. One half of the mixture was stirred fur-
ther and the other was treated similarly but in the pres-
ence of mercury. These experiments support the
previous observation that both acetonitrile and N,N‐
diisopropylethylamine (DIPEA) facilitate the loss of
metal. A marked increase in the conversion after the
removal of the heterogeneous catalyst was observed in
the absence of mercury (Table 7, entry 1), and some
further reaction could be detected even in its presence
(entry 2) showing that mainly copper nanoparticles but
also some complexes have leached into the solution. Sim-
ilar experiments with CAT‐3 in CH2Cl2 (entries 5 and 6)
showed almost no conversion in the absence of the
solid catalyst. These results are in accordance with the
leaching data obtained by ICP measurements (Table 6,
entries 2, 3 and 8).

10 of 13
FEHÉR ET AL.
TABLE 7 Mercury poisoning testsa
First step
Second step
Entry
Catalyst
Solvent
Base
Reaction time (h)
Yield of 7aa (%)b
Hg
Reaction time (h)
Yield of 7aa (%)b
1
2
3
4
5
6
CAT‐2
CH3CN
DIPEA
2
5
5
37
−
+
−
+
−
+
22
22
21
21
19
19
99
47
51
37
35
35
CAT‐2
CAT‐3
CH3CN
CH2Cl2
−
−
17
35
aReaction conditions: 0.1 mmol 5a, 0.1 mmol 6a, catalyst (with 0.01 mmol Cu content), 1 ml solvent, room temperature.
bDetermined by GC.
The recyclability of CAT‐3 was also tested in the
model reaction. The progress of triazole formation was
followed by GC using fresh and spent catalysts
(Figure 4). The results show that even a slight increase
in the reaction rate can be observed after the reuse of
the catalyst.
During further recycling tests, some decrease in the
catalytic activity was observed only after the seventh run
(Figure 5) and somewhat longer reaction time had to be
used to achieve total conversion in cycles 8–10. A total
loss of 8% of the original load of copper was detected in
the 10 cycles. The low level of copper leaching is in accor-
dance with the hot filtration and mercury poisoning tests
(Table 7, entries 5 and 6).
It should be mentioned that the activity of CAT‐3 was
FIGURE 5 Recycling experiments with CAT‐3: reaction time
necessary for total conversion (reaction conditions: 0.1 mmol 5a,
0.1 mmol 6a, CAT‐3 (with 0.01 mmol Cu content), 1 ml CH2Cl2,
room temperature)
also evaluated in the presence of sodium ascorbate (in a
CH2Cl2–water (1,1) solvent mixture) to reduce surface‐
bonded Cu(II) to Cu(I). In a 20 h reaction, 80% conversion
was achieved, which is considerably lower than that
obtained under the standard conditions (95% after 20 h).
3.3 | Synthesis of Other 1,4‐Disubstituted
1,2,3‐Triazoles
Based on the experiments discussed above, CAT‐3 was
chosen to carry out CuAAC reactions of other substrates
(Scheme 3) involving simple azides and alkynes, as well
as ferrocene and steroid derivatives.
Three consecutive runs were carried out in each case.
The reactions were followed by GC (Table 8, entries 1–3)
and TLC measurements (entries 4–11). The products were
purified by column chromatography. Good recyclability of
the catalyst was observed in each case. At the same time,
bulky substituents on either the alkyne or the azide com-
ponents were found to retard the reaction, so triazoles
7ad, 7ba, 7bd and 7ca could be produced in moderate
yields. It should be mentioned however, that from the
series of compounds derived from azide 5c, only triazole
7ca was isolated in lower yield compared to the results
obtained under homogeneous conditions.[39]
FIGURE 4 Triazole formation in the reaction of 5a and 6a in the
presence of fresh and spent CAT‐3 catalyst (reaction conditions:
0.1 mmol 5a, 0.1 mmol 6a, CAT‐3 (with 0.01 mmol Cu content),
1 ml of CH2Cl2, room temperature)

FEHÉR ET AL.
11 of 13
SCHEME 3 Azide–alkyne
cycloaddition of various substrates
TABLE 8 Azide–alkyne cycloaddition of various substratesa
Yield (%)b
Run 1
Entry
Azide
Alkyne
Product
Run 2
Run 3
1
5a
5a
5a
5a
5b
5b
5b
5b
5c
5c
5c
6a
6b
6c
6d
6a
6b
6c
6d
6a
6b
6c
7aa
7ab
7ac
7ad
7ba
7bb
7bc
7bd
7ca
7cb
7cc
99 (100)
78 (85)
71 (84)
56
98 (100)
70 (77)
76 (88)
41
99 (100)
80 (90)
78 (89)
48
2
3
4
5
52
50
55
6
93
91
87
7
92
96
93
8
26
24
24
9
46
45
51
10
11
79
76
70
73
70
73
aReaction conditions: CAT‐3 (10 mol% Cu), azide (0.2 mmol), alkyne (0.2 mmol), CH2Cl2 (2 ml), room temperature, 24 h.
bIsolated yields after column chromatography. GC yields are in parentheses.
core or a ferrocene moiety. At the same time, steric hin-
drance of these groups retarded cycloaddition considerably.
4 | CONCLUSIONS
An organic/inorganic hybrid material comprising a silica
support and a polymer with imidazolium moieties was
prepared for the immobilisation of a copper catalyst. The
reaction conditions generally used for homogeneous
reactions, such as the application of a polar solvent and the
addition of a base, accelerated the reaction but also resulted
in a higher loss of copper. Filtration and mercury poisoning
tests showed that under these conditions both catalytically
active copper complexes and nanoparticles were present in
the liquid phase. By the use of a less polar solvent (CH2Cl2)
and in the absence of an amine, the copper loss could be
reduced considerably. The catalyst was proved to be
recyclable without any loss of catalytic activity during seven
consecutive runs in the reaction of phenylacetylene and
benzyl azide and could be reused with good results in at least
three further cycles. Recyclability was proved during the
synthesis of various other triazoles, including azide and
alkyne molecules with bulky substituents, such as a steroid
ACKNOWLEDGEMENTS
This work was supported by the National Research, Devel-
opment and Innovation Office (OTKA K105632, OTKA
K120014) and European Union ‐ European Regional Devel-
opment Fund (GINOP‐2.3.2‐15‐2016‐00049 grant). E.N. is
grateful for the support of ÚNKP‐16‐2‐II, New National
Excellence Program of the Ministry of Human Capacities.
ORCID
Rita Skoda‐Földes http://orcid.org/0000-0002-9810-1509
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