Wheel-shaped copper containing polyoxotungstate as an efficient catalyst in the three-component synthesis of 1,2,3-triazoles

Article abstract of DOI:10.1039/c5ra25116h

Wheel-shaped polyoxotungstate [Cu₂₀Cl(OH)₂₄(H₂O)₁₂(P₈W₄₈O₁₈₄)]^25- (Cu₂₀ POM) was used as an efficient catalyst for the preparation of triazoles from the corresponding alkyl halides, sodium azide, and alkynes. In this click reaction, the three-component synthesis of 1,2,3-triazoles was performed under mild reaction conditions at room temperature and high to excellent yields were obtained. The isolation and purification processing of organic azides were avoided in this procedure, as they were prepared in situ.

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Wheel-Shaped Copper Containing Polyoxotungstate as an Efficient Catalyst
in Three-Component Synthesis of 1,2,3-Triazoles
Fariba Jalilian, Bahram Yadollahi*, Shahram Tangestaninejad, Hadi Amiri Rudbari
Department of Chemistry, University of Isfahan, Isfahan 81746ꢀ73441, Iran
Abstract: Wheelꢀshaped polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25– (Cu20 POM)
was used as an efficient catalyst for preparation of triazoles from the corresponding alkyl halides,
sodium azide, and alkynes. In this click reaction, threeꢀcomponent synthesis of 1,2,3ꢀtriazoles
was done under mild reaction conditions at room temperature and high to excellent yields were
obtained. The isolation or purification processing of organic azides were avoided in this
procedure, as they were prepared in situ.
Keywords: Wheelꢀshaped polyoxotungstate, catalyst, triazoles, organic azide, alkynes
*Corresponding Author. Tel: +98ꢀ31ꢀ37934934; fax: +98ꢀ31ꢀ36689732; eꢀmail: yadollahi@chem.ui.ac.ir,
yadollahi.b@gmail.com
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1. Introduction
"Click Chemistry", which proposed at first in 2001, is related to the reactions that exhibits high
yields, high regioꢀ and stereoꢀspecificity, and create only byꢀproducts that simply could be
removed1. The 1,3ꢀdipolar cycloadditions, nucleophilic ring opening reactions of epoxides and
aziridines, nonꢀaldol type carbonyl reactions such as formation of hydrazones and heterocycles,
additions to carbonꢀcarbon multiple bonds such as oxidative formation of epoxides and Michael
additions are examples of click reactions2, 3. Huisgen 1,3ꢀdipolar cycloaddition is an interesting
reaction for the preparation of 1,2,3ꢀtriazoles. Unfortunately, the nonꢀcatalyzed Huisgen 1,3ꢀ
dipolar cycloaddition of alkynes to azides requires elevated temperatures4 and by asymmetric
alkynes a mixture of two regioisomers are also produce5.
Copper(I) catalyzed triazole formation from azides and alkynes is an extraordinarily robust
reaction which could be performed under different conditions4, 6. In this regard, copper catalyzed
azide alkyne Huisgen cycloaddition (CuAAC) is one of the most powerful chemical reactions
within the click chemistry concept. CuAAC as a prototype click reaction has emerged as a green
methodology to connect diverse building blocks in chemical synthesis, functionalization of
proteins and nucleic acids, biological chemistry, materials science and drug discovery7ꢀ9.
Different copper(I) catalysts such as CuI, CuOTf·C H , and [Cu(CH3CN)4]PF6 have been
6
6
employed in the CuAAC reaction10, 11. 1,3ꢀDipolar cycloaddition of organic azides to alkynes by
a dicopperꢀsubstituted silicotungstate has also been reported. In this work, authors exhibited that
the reduced dicopper core plays an important role in the CuAAC reaction12.
In the most of reports, organic azides and alkynes are two main component in the synthesis of
1,2,3ꢀtriazoles13. Although organic azides are generally stable and safe, small organic azides
could be especially dangerous and difficult to handle14. In order to avoid the isolation or
2

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purification processing of organic azides in this type of cycloaddition reactions, different
methodologies have been delivered in the literature. The oneꢀpot synthesis of triazoles from
aromatic halides15, amines14, boronic acids16 or alkyl/allyl halides17 were performed by in situ
preparation of azides.
Polyoxometalates (POMs) are a distinctive class of wellꢀknown metal oxide inorganic molecular
clusters. Because of their widespread applications in various fields such as chemical, biological
and materials sciences, catalysis, and magnetism they attracted excessive considerations18ꢀ20. In
the last 20 years, POM chemistry has completely been changed and nowadays could be regarded
as a new type of nanochemistry and nanomaterials science21.
The discovery of [Mo154(NO)14O448H14(H2O)70]28– (Mo154), which is one of the first structures
based on nonꢀclassical POM units, was a turning point in giant POMs22, 23. Wheelꢀshaped
polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25– (Cu20 POM) is the first transitionꢀmetal
substituted derivative of [H7P8W48O184]33– (P8W48) in direct reaction by copper(II) ions24. The
P8W48 compound is a stable wheelꢀshaped precursor which is made by fusing four Dawsonꢀtype
P2W12 fragments25. The Cu20 POM cluster is the smallest type of macro ions showing the unique
blackberry selfꢀassembly behavior.
Herein, for the first time, oneꢀpot synthesis of 1,2,3ꢀtriazoles from alkyl halides, sodium azide
and alkynes in the presence of Cu20 POM as a highly efficient catalyst is reported (Scheme 1).
Scheme 1. Oneꢀpot synthesis of 1,2,3ꢀtriazoles in the presence of Cu20 POM
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2. Results and discussion
In this work, the catalytic role of some copper containing POMs in the CuAAC reaction for oneꢀ
pot synthesis of 1,2,3ꢀtriazoles from alkyl halides, sodium azide and alkynes are investigated.
Different Cu containing POMs were synthesized and characterized according to literatures26ꢀ30
and used in this cycloaddition reaction. As the starting point of our exploration, the reaction
between benzyl bromide and phenylacetylene was chose as a model reaction. In Table 1, the
catalytic effects of different copper containing POMs and CuI, as a simple copper (I) salt, in the
synthesis of 1,2,3ꢀtriazoles are shown. As it could be seen in Table 1, among different Cu
substituted POMs, Cu20 POM is the most effective catalyst (Table 1, entry 6). From this results,
Cu20 POM was selected as the best catalyst in this system. Various amount of Cu20 POM catalyst
was also checked and 10 ꢁmol was chose as optimal amount.
Table 1. The catalytic effect of different Cu containing POMs in the synthesis of 1,2,3ꢀtriazolesa
Entry Catalyst
Time (h)
Yields (%)b
1
2
3
4
5c
6
7
8
9
[γꢀH2SiW10O36Cu2(ꢀꢀ1,1ꢀN3)2]4–
4
2
2
2
4
1.5
2
2
55
60
65
[SiW9O37{Cu(H2O)}3]10–
[K3Cu3(NO3)(PW9O34)2]9–
[Cu4(PW9O34)2]10–
80
[Cu20Cl(OH)24(H2O)12(P8W48O184)]25–
[Cu20Cl(OH)24(H2O)12(P8W48O184)]25–
[H7P8W48O184]33–
<1
>98
<1
25
CuI
Without catalyst
2
<1
aReaction conditions: benzyl bromide (0.5 mmol), phenylacetylene (0.5 mmol), sodium azide
(0.5 mmol), sodium ascorbate (10 mol%) and catalyst (10 µmol), in water/tꢀBuOH (2:1; 3 mL) at
room temperature
bIsolated yields
cReaction in the absence of sodium ascorbate
In the presence of CuI at the same reaction conditions only 25% yields for the corresponding
1,2,3ꢀtriazoles was observed (Table 1, entry 8). The cycloaddition reaction in the absence of
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catalyst was not proceeded, thus the presence of catalyst is crucial (Table 1, entry 9). The same
[H7P8W48O184]33–,
of
result
was
also
obtained
for
as
the
precursor
[Cu20Cl(OH)24(H2O)12(P8W48O184)]25– catalyst, which stated on the catalytic effect of substituted
coppers in the reaction. In the presence of Cu(II) containing POM or in other words the absence
of sodium ascorbate, the cycloaddition reaction was rarely proceeded (Table 1, entry 5). As
mentioned above, it was reported that the CuAAC reactions catalyzed by copper(I) catalysts12.
So, copper(II) atoms in Cu20 POM and/or other POMs should be reduced to copper(I). In the
presence of Cu(II) containing POMs and sodium ascorbate (10 mol%) as reducing agent, the
Cu(I) catalysts were prepared and used in oneꢀpot cycloaddition of benzyl bromide,
phenylacetylene and sodium azide. By sodium ascorbate, as a reducing agent, the CuAAC
reaction was efficiently performed at room temperature to give the corresponding product in
98% yield.
By addition of sodium ascorbate to the catalytic system, the color of Cu20 POM solution has been
changed from blue to colorless (Figure 1) and the catalytic reaction was initiated after formation
of copper(I) containing POMs. This proposal could be supported by the fact that the absorption
band at 700 nm, which is assignable to the dꢀd transition of the copper(II) atoms in Cu20 POM, is
disappeared12 (Figure 1). Results were also indicated that almost all copper(II) atoms in POM
catalyst might be reduced to copper(I) species.
In the next step, the effect of different solvents in the cycloaddition reaction between benzyl
bromide and phenylacetylene in the presence of Cu20 POM as catalyst at room temperature was
studied. From the results in Table 2, among different solvents, a mixture of water and tꢀBuOH
was found to be the best (Table 2, entry 10) and the cycloaddition reaction in other solvents was
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performed in moderate to good yields. A key role for this solvent mixture was the high solubility
respect to both of the Cu(I) POM catalyst and substrates, and so increasing in the reaction rate.
Figure 1. UVꢀvis spectra of Cu20 POM solutions before (a) and after (b) addition of sodium
ascorbate
Table 2. Catalytic synthesis of 1,2,3ꢀtriazoles in different solventsa
Entry
Solvent
Yields (%)
1
2
MeCN
Me2SO
65
50
3
H2O
70
4
EtOH
60
5
iꢀPrOH
57
6
7
8
9
tꢀBuOH
<20
73
68
80
>98
H2O/EtOH (2:1)
H2O/MeCN (2:1)
H2O/Me2SO (2:1)
H2O/tꢀBuOH (2:1)
10
aReaction conditions: benzyl bromide (0.5 mmol), phenylacetylene (0.5 mmol), sodium azide
(0.5 mmol), sodium ascorbate (10 mol%), catalyst (10 µmol), and solvent (3 mL) at room
temperature in 2 h.
With the optimal reaction conditions in hand, phenylacetylene, benzyl bromide, sodium azide,
Cu20 POM catalyst and sodium ascorbate were suspended in a 2:1 mixture of water and tꢀBuOH
and after completion of the reaction, 1ꢀbenzylꢀ4ꢀphenylꢀ1Hꢀ1,2,3ꢀtriazole has been produced in
98% yield (Table 3, entry 1). The reaction scope was explored by testing other benzyl halides
with different substituents, as shown in Table 3. In this catalytic system different benzyl halides
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converted to the corresponding 1,2,3ꢀtriazole in excellent yields. The reaction of benzyl chloride
was completed within 2 h to give the desired product in 97% yield (Table 3, entry 2). Due to the
presence of strong electron withdrawing nitro group on the phenyl ring, a pꢀnitro benzyl bromide
(Table 3, entry 4) was shown to be less reactive than other benzyl halides. In this catalytic
cycloaddition reaction, the preparation of triazoles with aliphatic alkynes as well as aromatic
terminal ones were also performed (Table 3, entry 7–10).
Table 3. Oneꢀpot synthesis of 1,2,3ꢀtriazoles from benzyl halides, sodium azide, and alkynes in
the presence of Cu20 POM as catalysta
Entry
Benzyl halide
Alkyne
Time (h) Yields (%)b
1
Phenylacetylene
1.5
2
>98
97
2
3
Phenylacetylene
Phenylacetylene
1.45
3
98
90
96
4
5
Phenylacetylene
Phenylacetylene
2
6
Phenylacetylene
1ꢀOctyne
2
4
94
98
96
93
90
95
7
8
1ꢀOctyne
4
9c
10c
11d
1ꢀPentyne
4
1ꢀPentyne
4
Phenylacetylene
1.5
aReaction conditions: Benzyl halide (0.5 mmol), alkyne (0.5 mmol), sodium azide (0.5 mmol),
sodium ascorbate (10 mol%), Cu20 POM catalyst (10 µmol) in water/tꢀBuOH (2:1) at room
temperature
bIsolated yields
cExcess amount of 1ꢀpentyne was used
dData from recovered catalyst after run three
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Ultimately, the recovered catalyst was reused under the same reaction conditions for three times
and any significant loss of catalytic activity were not observed (Table 3, entry 11). The XRD
pattern of recovered catalyst after run three revealed that the structure of catalyst is preserved
(Figure S1).
Based on the previous discussions31 and the above mentioned results, a rationale mechanistic
pathway for the CuAAC reaction was envisaged (Figure 2). From above, it could be seen that the
presence of sodium ascorbate is crucial, because it reduces Cu(II) to Cu(I) in Cu20 POM. Also, in
this catalytic system the alkyne oxidative homocoupling products were not detected. So, It might
be deduced that the Cu(I) species reacts with alkynes to give copper acetylide. The 1,3ꢀdipolar
cyclization of the resulting Cu acetylide and an in situ prepared organic azide followed by the
protonation provides the triazole product and regenerates Cu(I) catalyst.
Figure 2. Plausible pathway for oneꢀpot synthesis of 1,2,3ꢀtriazoles by Cu20 POM as catalyst
3. Experimental
3.1 Materials and methods
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All chemicals were analytical grade, commercially available and used without further
purification. Different POMs were prepared according to literature and used in catalytic
reactions24ꢀ30. Infrared spectra (KBr pellets) were recorded on a FTIR Bruker Vector 22
instrument. UVꢀvis spectra were recorded on a Cary 100 UVꢀvis spectrophotometer (190ꢀ2700
nm). The elemental analysis was performed on a Leco, CHNSꢀ932 and a PerkinꢀElmer 7300 DV
1
elemental analyzer. HNMR spectra was obtained in CDCl3 on Bruker (400 MHz; 296 K) and
referenced to TMS (0.0 ppm) as external standard. Xꢀray diffraction data (XRD) were obtained
on a D8 Advanced Bruker using Cu Kα radiation (2θ = 10–80◦).
3.2. Synthesis of Cu20 POM
K12Li13[Cu20Cl(OH)24(H2O)12(P8W48O184)]·22H2O was prepared according to the literature24: A
sample of CuCl2·2H2O (0.60 mmol) was dissolved in a 1M LiCH3COO buffer solution (20 mL)
at pH 6.0, then K28Li5[H7P8W48O184]·92H2O (0.025 mmol) (synthesized according to literature)28
was added. This solution was heated to 80 °C for 1 h and after cooling to room temperature it
was filtered. The filtrate was allowed to evaporate at room temperature. After 1–2 days a blue
crystalline product started to appear. Evaporation was allowed to continue until the solution level
had approached the solid product, which was then collected by filtration and airꢀdried. Yield:
30%. IR: ῡ =1136(sh), 1121(s), 1080(s), 1017(m), 979(sh), 950(sh), 932(s), 913(sh), 830(sh),
753(s),
683(s),
570(sh),
525(w)
cmꢀ1.
Elemental
analysis
data
for
K12Li13[Cu20Cl(OH)24(H2O)12(P8W48O184)]: Calcd.: K: 3.2, Li: 0.6, W:59.2, Cu: 8.5, P: 1.7;
found: K: 3.35, Li: 0.71, W: 60.1, Cu: 8.3, P: 1.6 (Figures S1ꢀS5).
3.2. General procedure for the three-component synthesis of 1,2,3-triazoles
A 10 mL glass vessel was charged with Cu20POM catalyst (10 µmol), sodium ascorbate (10 mol
%), an alkyne (0.5 mmol), sodium azide (0.5 mmol), and an alkyl halide (0.5 mmol) in a mixture
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of water and tertꢀbutyl alcohol (2:1; 3 mL). The reaction vessel was stirred at room temperature
for 2–4h and the color of reaction mixture was changed from blue to yellow during the progress
of reaction. After completion of the reaction, colorless triazole product was precipitated (Figures
S6–S12). The products were quantitatively recovered by simple extraction with ethyl acetate (3 ×
2 mL). The organic layer was separated, dried over MgSO4 and concentrated under reduced
pressure to give the corresponding 1,2,3ꢀtriazole. Purification of the obtained triazoles were
accomplished by a recrystallization process (EtOAc:nꢀhexane). All of the products were known
and characterized by comparison their spectral data with authentic samples.
4. Conclusion
In this catalytic system a wheelꢀshaped Cu20 POM, [Cu20Cl(OH)24(H2O)12(P8W48O184)]25–, was
firstly reduced and used for oneꢀpot synthesis of 1,2,3ꢀtriazoles in CuAAC reaction. After
optimization of the reaction conditions, oneꢀpot synthesis of different 1,2,3ꢀtriazoles from
alkynes and in situ prepared organic azides were shown high to excellent yields under mild
reaction conditions. Moreover, this catalytic method avoids isolation and handling of potentially
unstable low molecular weight organic azides, and provides 1,2,3ꢀtriazole products in pure form.
Additionally, the triazoles products could be easily separated from the reaction mixture.
Acknowledgement
Support for this research by the University of Isfahan is acknowledged.
Supporting Information
Synthesis and characterization of the catalysts and spectral data for products are shown in
Supporting Information.
References
1.
T. V. Hansen, P. Wu, W. D. Sharpless and J. G. Lindberg, J. Chem. Edu., 2005, 82,
1833ꢀ1836.
10

Page 11 of 12
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View Article Online
DOI: 10.1039/C5RA25116H
2.
R. K. Iha, K. L. Wooley, A. M. Nyström, D. J. Burke, M. J. Kade and C. J. Hawker,
Chem. Rev., 2009, 109, 5620ꢀ5686.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
H. C. Kolb, M. Finn and K. B. Sharpless, Angew. Chem. Int. Ed., 2001, 40, 2004ꢀ2021.
L. Liang and D. Astruc, Coord. Chem. Rev., 2011, 255, 2933ꢀ2945.
P. Ji, J. H. Atherton and M. I. Page, Org. Biomol. Chem., 2012, 10, 7965ꢀ7969.
M. Meldal and C. W. Tornøe, Chem. Rev., 2008, 108, 2952ꢀ3015.
L. Jiang, Z. Wang, S.ꢀQ. Bai and T. A. Hor, Dalton Trans., 2013, 42, 9437ꢀ9443.
J.ꢀc. Meng, V. V. Fokin and M. Finn, Tetrahedron Lett., 2005, 46, 4543ꢀ4546.
A. Hashidzume, T. Nakamura and T. Sato, Polymer, 2013, 54, 3448ꢀ3451.
J. E. Hein and V. V. Fokin, Chem. Soc. Rev., 2010, 39, 1302ꢀ1315.
L. Zhu, V. M. Lynch and E. V. Anslyn, Tetrahedron, 2004, 60, 7267ꢀ7275.
K. Kamata, Y. Nakagawa, K. Yamaguchi and N. Mizuno, J. Am. Chem. Soc., 2008, 130,
15304ꢀ15310.
13.
V. D. Bock, H. Hiemstra and J. H. Van Maarseveen, Eur. J. Org. Chem., 2006, 2006, 51ꢀ
68.
14.
15.
16.
H. S. Beckmann and V. Wittmann, Org. Lett., 2007, 9, 1ꢀ4.
T. Miao and L. Wang, Synthesis, 2008, 363ꢀ368.
C.ꢀZ. Tao, X. Cui, J. Li, A.ꢀX. Liu, L. Liu and Q.ꢀX. Guo, Tetrahedron Lett., 2007, 48,
3525ꢀ3529.
17.
M. L. Kantam, V. S. Jaya, B. Sreedhar, M. M. Rao and B. Choudary, J. Mol. Catal.,
2006, 256, 273ꢀ277.
18.
19.
20.
M. L. Kistler, K. G. Patel and T. Liu, Langmuir, 2009, 25, 7328ꢀ7334.
R. Mekala, S. Supriya and S. K. Das, Inorg. Chem., 2013, 52, 9708ꢀ9710.
A. Rezaeifard, R. Haddad, M. Jafarpour and M. Hakimi, J. Am. Chem. Soc., 2013, 135,
10036ꢀ10039.
21.
22.
23.
A. Müller, Chem. Commun., 2003, 2003, 803ꢀ806.
A. Müller and C. Serain, Acc. Chem. Res., 2000, 33, 2ꢀ10.
A. Müller, E. Krickemeyer, H. Bögge, M. Schmidtmann, C. Beugholt, P. Kögerler and C.
Lu, Angew. Chem. Int. Ed., 1998, 37, 1220ꢀ1223.
24.
25.
S. S. Mal and U. Kortz, Angew. Chem. Int. Ed., 2005, 44, 3777ꢀ3780.
S. S. Mal, B. S. Bassil, M. Ibrahim, S. Nellutla, J. van Tol, N. S. Dalal, J. A. Fernández,
X. López, J. M. Poblet and R. N. Biboum, Inorg. Chem., 2009, 48, 11636ꢀ11645.
J. Liu, F. Ortéga, P. Sethuraman, D. E. Katsoulis, C. E. Costello and M. T. Pope, J.
Chem. Soc., Dalton Trans., 1992, 1901ꢀ1906.
26.
27.
K. Yamaguchi, K. Kamata, S. Yamaguchi, M. Kotani and N. Mizuno, J. Catal., 2008,
258, 121ꢀ130.
28.
29.
30.
R. Contant, Inorg. Synth., 1990, 27, 110ꢀ111.
R. G. Finke, M. W. Droege and P. J. Domaille, Inorg. Chem., 1987, 26, 3886ꢀ3896.
M. R. Farsani, B. Yadollahi, H. A. Rudbari, A. Amini, T. CaradocꢀDavis and J. R. Price,
Inorg. Chem. Commun., 2014, 43, 39ꢀ44.
31.
V. O. Rodionov, S. I. Presolski, D. Díaz Díaz, V. V. Fokin and M. Finn, J. Am. Chem.
Soc., 2007, 129, 12705ꢀ12712.
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Graphical abstract:
Wheel-Shaped Copper Containing Polyoxotungstate as an Efficient Catalyst in Three-
Component Synthesis of 1,2,3-Triazoles
Fariba Jalilian, Bahram Yadollahi*, Shahram Tangestaninejad, Hadi Amiri Rudbari
aDepartment of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran
The catalytic effect of Wheel-shaped polyoxotungstate [Cu20Cl(OH)24(H2O)12(P8W48O184)]25–
was investigated in preparation of triazoles from the corresponding alkyl halides, sodium azide,
and alkynes. This click reaction was done under mild reaction conditions at room temperature
and high to excellent yields were obtained.