An efficient synthesis of 1,4-disubstituted triazoles in water via CuCl2/Zn-catalyzed huisgen cycloaddition

Article abstract of DOI:10.1515/znb-2012-0308

An efficient method for the synthesis of 1,4-disubstituted triazoles in water at room temperature has been developed using CuCl₂/Zn as a catalyst system. Under the optimized conditions, a novel series of 1,4-disubstituted 1,2,3-triazoles were synthesized.

Full text of DOI:10.1515/znb-2012-0308

An Efficient Synthesis of 1,4-Disubstituted Triazoles in Water
via CuCl2/Zn-Catalyzed Huisgen Cycloaddition
Yuqin Jiang, Peng Zhang, Wei Li, Xiaojing Li, and Guiqing Xu
College of Chemistry and Environmental Science, Henan Normal University,
Xinxiang, 453007, P. R. China
Reprint requests to Dr. Gui Qing Xu. Fax: +86-373-3329023. E-mail: jiangyuqin@htu.cn
Z. Naturforsch. 2012, 67b, 226 – 230; received February 9, 2012
An efficient method for the synthesis of 1,4-disubstituted triazoles in water at room temperature
has been developed using CuCl2/Zn as a catalyst system. Under the optimized conditions, a novel
series of 1,4-disubstituted 1,2,3-triazoles were synthesized.
Key words: Huisgen Cycloaddition, CuCl2/Zn, 1,4-Disubstituted Triazole
Introduction
ciency. The CuAAC reaction catalyzed by these copper
nanoparticles was completed within 30 min [11]. Some
supported catalysts [12, 13] were also successfully ap-
plied. It is worth to mention that alumina-supported
copper nanopartiles, prepared by Kantam from cop-
per(II) acetylacetonate and aluminum isopropoxide
precursors using an aerogel protocol, were success-
fully applied in a three-component CuAAC reaction
among terminal alkynes, sodium azide and alkyl/allyl
halides [12]. The application of solution-state copper
nanoparticles is a useful way to avoid the aggrega-
tion of nanoparticles. For instance, Sarka used PVP-
stabilized copper nanoparticles in DMF or formamide
as a catalyst for the CuAAC reaction [14]. However,
the nanosized copper has limited application due to its
complicated and costly preparation.
Metallic copper could also be generated in situ in a
redox reaction between CuSO4 and Zn. The catalytic
activity effect of the CuSO4/Zn powder in the CuAAC
reaction led to a further study of this catalyst system.
In the work described in this paper, an efficient method
for 1,3-dipolar cycloadditions at relatively mild and en-
vironmentally friendly conditions is established. The
in situ generated copper from CuCl2/Zn powder in wa-
ter was directly used as a catalyst without a stabilizing
agent.
Triazoles are an important class of heterocyclic
compounds. In recent years 1,2,3-triazoles gained
more and more interest due to their diverse biolog-
ical activities and synthetic methodology [1 – 3]. An
efficient approach for constructing the 1,2,3-triazole
unit is the copper(I)-catalyzed azide-alkyne cycload-
dition (CuAAC) reaction, which was discovered inde-
pendently by the groups of Sharpless and Meldal [4, 5].
The sources of the copper(I) catalyst for a CuAAC
reaction usually are Cu(I) salts, or Cu(II) salts to-
gether with a reducing agent (often sodium ascorbate
or metallic copper). Furthermore, it was reported that
metallic copper can be an alternative source for the
CuAAC reaction. Using metallic copper as the cata-
lyst was attractive because of a much easier work-up
and purification. Unfortunately, the reaction times are
usually long when using metallic copper as the cata-
lyst [6, 7], except when physical techniques such as ul-
trasound irradiation are used [8]. In order to shorten the
reaction time, nanosized copper was used as the cata-
lyst. Orgueira successfully performed a CuAAC reac-
tion utilizing an activated nanosized copper powder as
the source of the catalytic species in the presence of
amine hydrochloride salts [9]. A CuAAC reaction re-
ported by Pacho´n was carried out in t-BuOH/H2O cat-
alyzed by copper nanoclusters, and it took 18 h to com-
plete the reaction [10]. In comparison with the nano-
sized copper mentioned above, copper nanoparticles
Results and Discussion
The CuAAC reaction between propargyl phenyl
prepared by mixing copper(II) chloride, lithium metal ether and benzyl azide was selected as a model reaction
and a catalytic amount of 4,4ꢀ-di-tert-butyl-biphenyl to optimize the reaction conditions (Scheme 1). For
(DTBB) in THF at r. t., showed a better catalytic effi- screening the suitable solvent, the model reaction cat-
c
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Y. Jiang et al. · Synthesis of 1,4-Disubstituted Triazoles
227
Scheme 1. Model reaction of cycloaddi-
tion for optimizing the reaction condi-
tions.
Table 1. Screening of solvents for the model reaction using Table 2. Screening of catalysts for the model reaction in wa-
CuSO4 (10 mol-%)/Fe powder (10 mol-%) as the catalyst ter for 60 min.a
system.a
Entry
Catalyst system (10 mol-%)
CuSO4/Fe
Time (min)
Yield (%)b
Entry
Solvent
H2O
Time (min)
150
Yield (%)b
1
2
3
4
5
6
7
60
60
60
60
60
60
60
60
42
75
29
90
9
34
17
70
CuSO4/Zn
CuCl2/Fe
CuCl2/Zn
Cu(OAc)2/Fe
Cu(OAc)2/Zn
CuBr2/Fe
1
2
3
4
5
6
7
8
82
21
60
10
57
38
11
30
15
H2O/DMF
H2O/DMSO
H2O/t-BuOH
H2O/EtOH
H2O/CHCl3
H2O/THF
H2O/CH3CN
DMF
150
150
150
150
150
150
150
150
8
CuBr2/Zn
a
Model reaction conditions: propargyl phenyl ether (1 mmol), ben-
zyl azide (1 mmol), solvent 6 mL, the equal volume mixed for co-
solvent; b isolated yield.
9
a
Model reaction conditions: propargyl phenyl ether (1 mmol), ben-
zyl azide (1 mmol), solvent 6 mL, the equal volume mixed for co-
solvent; b isolated yield.
alyzed by the CuSO4 (10 mol-%)/Fe powder (10 mol-
%) system was carried out in different solvents (includ-
ing water, pure organic solvents or their co-mixtures)
with vigorous magnetic stirring at r. t. for 150 min as
shown in Table 1. Among the tested solvents, the high-
est yield was obtained in water (82 %). The moder-
ate yield obtained in H2O-DMSO or H2O-EtOH at a
ratio of 1 : 1 (v/v) is 60 and 57 %, respectively. Al-
though propargyl phenyl ether and benzyl azide have
a good solubility in the tested organic solvents (such
as DMF, DMSO and t-BuOH), the yield was not more
than 15 %. The poor yield might be attributed to the
poor solubility of CuSO4 and Fe powder in organic
solvents, which hampered the generation of metallic
copper. The yield increases in the order: organic sol-
Fig. 1. Screening of catalyst loading for the model reaction
in water for 60 min.
vent, co-solvent, water. Thus water was selected as the copper(II) salt/Zn powder is better than that of the cop-
reaction solvent.
Different copper(II) salts (10 mol-%) together with
Zn or Fe powder (10 mol-%) shown in Table 2 were
per(II) salt/Fe powder, because Zn is more active than
Fe in the redox reaction.
In order to investigate the influence of smaller
screened for the catalytic efficiency of the model reac- amounts of the copper(II) salt/Zn powder on the model
tion. All the reactions were performed in water with reaction, the amounts of the CuCl2/Zn powder were
vigorous stirring for 60 min. Among the tested cat- reduced to 5, 1, 0.5, and 0.1 mol-%. As shown in
alytic systems, the best catalytic efficiency was ob- Fig. 1, the yield decreased from 90 to 2 % indicat-
served for the CuCl2/Zn powder. The 1,3-dipolar cy- ing that the catalytic efficiency of the catalyst system
cloaddition reaction catalyzed by this system was com- CuCl2/Zn powder decreased when lower catalyst load-
pleted within 60 min in 90 % yield (Table 2). In com- ing was used, and the reaction takes more time to be
parison to CuCl2/Zn powder, lower catalytic efficien- finished. When CuCl2 (5 mol-%)/Zn powder (5 mol-
cies were observed for other copper(II) salt/metallic %) was used as the catalyst, 2.5 h were needed to com-
powder catalysts, among which Cu(OAc)2/Fe powder plete the model reaction. Considering the catalytic effi-
showed the lowest (9 %) and CuCl2/Zn powder the ciency, CuCl2 (10 mol-%)/Zn powder (10 mol-%) was
highest (90 %) yield. The catalytic efficiency of the selected as the optimized catalyst.
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228
Y. Jiang et al. · Synthesis of 1,4-Disubstituted Triazoles
Scheme 2. Synthesis of compounds 1 – 8.
Table 3. Synthesis of 1,4-disubstituted 1,2,3-triazoles
(Scheme 2).
tra (HRMS) were performed on a MicrOTOF-Q II mass spec-
trometer with an ESI source (Waters, Manchester, UK). Sub-
stituted terminal alkynes were synthesized according to the
literature [15 – 19]. Benzyl azide [20] was also synthesized
according to previous reports.
Compd. R1
R2
R3
R4 R5
R6
n
Time Yield
(min) (%)
1
2
3
4
5
6
7
8
H
H
H
H
NH2
H
H
CH3 benzyl
H
NO2
H
H
H
H
H
NO2
H
H
NO2
H
NO2
H
NO2
H
1
0
0
0
0
0
1
0
90
80
50
75
80
75
85
60
83
80
90
87
84
82
85
88
CH3 phenyl CH3
C3H7 phenyl CF3
C3H7 phenyl CH3
General procedure for the synthesis of triazoles
H
phenyl CF3
A mixture of the organic azide (1.0 mmol), the termi-
nal alkyne (1.0 mmol) and CuCl2 (10 mol-%)/Zn powder
(10 mol-%) in water (6 mL) was vigorously stirred at r. t.
After completion of the reaction as indicated by TLC, the re-
action mixture was diluted with saturated aq. NH4Cl (20 mL)
and extracted with CH2Cl2 (3 × 10 mL). The combined or-
ganic layers were washed with brine (10 mL), dried over an-
hydrous Na2SO4 and filtered. The solvent of the filtrate was
removed in vacuo to give the pure product.
NO2 phenyl CH3
Cl
H
benzyl
phenyl CH3
H
OCH3
NO2
The optimized relative quantities of reactants, cata-
lyst and solvent are: organic azide (1.0 mmol), termi-
nal alkyne (1.0 mmol), CuCl2 (10 mol-%)/Zn powder
(10 mol-%) and water (6 mL).
A series of 1,4-disubstituted 1,2,3-triazole deriva-
tives were synthesized based on the optimized condi-
tions (Scheme 2, Table 3). As shown in Table 3, reac-
tions between substituted terminal alkynes and organic
azides, including benzyl azide and phenyl azide gave
1,4-disubstituted 1,2,3-triazoles in good yields.
In summary, an efficient protocol for the synthesis
of a series of 1,2,3-triazole derivatives was established
using CuCl2 (10 mol-%)/Zn powder (10 mol-%) as the
catalyst and water as the solvent.
1-(4-Nitrobenzyl)-4-(p-tolyl)-1,2,3-triazole (1)
◦
M. p. 145 – 147 C. – IR (KBr): ν (cm−1) = 3097, 3047,
2921, 2851, 1670, 1605, 1556, 1515, 1456, 1427, 1350, 820,
731. – 1H NMR (400 MHz, CDCl3): δ = 8.21 (d, J = 8.0 Hz,
2H, Ar-H), 7.74 (s, 1H, CH-H), 7.69 (d, J = 8.0 Hz, 2H, Ar-
H), 7.43 (d, J = 12.0 Hz, 2H, Ar-H), 7.22 (d, J = 8.0 Hz,
2H, Ar-H), 5.68 (s, 2H, CH2-H), 2.37 (s, 3H, CH3-H). –
13C NMR (100 MHz, CDCl3): δ = 148.6, 147.8, 142.0,
138.3, 129.6, 128.5, 127.3, 125.6, 124.2, 119.8, 53.0, 21.3. –
MS (ESI): m/z (%) = 295 (100) [M+H]+. – HRMS ((+)-
ESI):m/z = 295.1197 (calcd. 295.1195 for C16H15N4O2,
[M+H]+).
Experimental Section
General
All the chemicals were obtained from Tianjin Kermel
Chemical Reagent Co., Ltd. and were used as received. All
melting points were determined on a YUHUA X-3 melt-
1-(2-Methyl-5-nitrophenyl)-4-(p-tolyl)-1,2,3-triazole (2)
◦
M. p. 102 – 103 C. – IR (KBr): ν (cm−1) = 3135, 3117,
ing point apparatus and are uncorrected. IR spectra were 3065, 3030, 2980, 2921, 2859, 1633, 1600, 1521, 1440,
recorded on a Bio-rad FTS-40 spectrometer. 1H and 13C 1380, 1350, 810, 797, 739, 706. – 1H NMR (400 MHz,
spectra were recorded on a Bruker Avance 400 MHz spec- CDCl3): δ = 8.30 (s, 1H, Ar-H), 8.28 (d, J= 4.0 Hz, 1H, Ar-
trometer operating at 400.13 and 100.61 MHz, respectively. H), 8.02 (s, 1H, CH-H), 7.80 (d, J = 8.0 Hz, 2H, Ar-H), 7.60
NMR spectra were recorded in CDCl3 or [D6]DMSO at r. t. (d, J= 8.0 Hz, 1H, Ar-H), 7.28 (d, J = 8.0 Hz, 2H, Ar-H), 2.43
◦
(20 2 C). 1H and 13C chemical shifts are quoted in parts (s, 3H, CH3-H), 2.41 (s, 3H, CH3-H). – 13C NMR (100 MHz,
per million downfield from TMS. ESI MS were recorded on a CDCl3): δ = 148.2, 146.4, 141.6, 138.6, 136.8, 132.6, 129.7,
Bruker Esquire 3000 instrument. High-resolution mass spec- 126.9, 125.7, 124.2, 121.1, 120.7, 21.3, 18.6. – MS (ESI):
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Y. Jiang et al. · Synthesis of 1,4-Disubstituted Triazoles
229
m/z (%) = 295 (100) [M+H]+. – HRMS ((+)-ESI):m/z = 4-[(4-Nitrophenoxy)methyl]-1-(2-methyl-5-nitrophenyl)-
295.1197 (calcd. 295.1195 for C16H15N4O2, [M+H]+).
1,2,3-triazole (6)
M. p. 183 – 185 C. – IR (KBr): ν (cm−1) = 3156, 3120,
3085, 2927, 1610, 1594, 1530, 1510, 1498, 1470, 1383,
1345, 1112, 844, 819, 798, 750. – 1H NMR (400 MHz,
[D6]DMSO): δ = 8.85 (s, 1H, CH-H), 8.37 (d, J = 8.0 Hz,
2H, Ar-H), 8.26 (d, J = 12.0 Hz, 2H, Ar-H), 7.82 (d,
J = 8.0 Hz, 1H, Ar-H), 7.34 (d, J = 12.0 Hz, 2H, Ar-H),
5.46 (s, 2H, CH2-H), 2.32 (s, 3H, CH3-H). – 13C NMR
(100 MHz, [D6]DMSO): δ = 163.6, 146.5, 142.7, 141.8,
141.5, 136.8, 133.3, 127.3, 126.3, 124.8, 121.5, 115.8, 62.2,
18.4. – MS (ESI): m/z (%) = 356 (100) [M+H]+. – HRMS
((+)-ESI):m/z = 356.0997 (calcd. 356.0995 for C16H14N5O5,
[M+H]+).
◦
1-[2-(Trifluoromethyl)phenyl]-4-(4-propylphenyl)-1,2,3-tri-
azole (3)
M. p. 87 – 89 C. – IR (KBr): ν (cm−1) = 3125, 3103,
◦
2964, 2932, 2860, 1643, 1609, 1591, 1513, 1495, 1460,
1377, 1319, 835, 806, 767, 704. – 1H NMR (400 MHz,
CDCl3): δ = 8.02 (s, 1H, CH-H), 7.88 (d, J = 8.0 Hz, 1H,
Ar-H), 7.82 (d, J = 8.0 Hz, Ar-H), 7.76 (t, J = 8.0 Hz,
16.0 Hz, 1H, Ar-H), 7.69 (t, J = 8.0 Hz, 16.0 Hz, Ar-H),
7.61 (d, J = 8.0 Hz, 1H, Ar-H), 7.28 (d, J = 8.0 Hz, 2H,
Ar-H), 2.63 (t, J = 4.0 Hz, 12.0 Hz, 2H, CH2-H), 1.63 –
1.72 (m, 2H, CH2-H), 0.96 (t, J = 4.0 Hz, 12.0 Hz, 3H,
CH3-H). – 13C NMR (100 MHz, CDCl3): δ = 147.9, 143.2,
135.1, 134.9, 133.1, 130.4, 129.0, 128.9, 127.4, 127.3, 126.3,
125.8, 121.9, 37.8, 24.5, 13.8. – MS (ESI): m/z (%) = 332
(100) [M+H]+. – HRMS ((+)-ESI):m/z = 332.1378 (calcd.
332.1375 for C18H17N3O3, [M+H]+).
4-[(4-Chlorophenoxy)methyl]-1-(4-nitrobenzyl)-1,2,3-tri-
azole (7)
◦
M. p. 90 – 91 C. – IR (KBr): ν (cm−1) = 3112, 3062,
2960, 2897, 2870, 1624, 1609, 1594, 1580, 1532, 1490,
1462, 1433, 1350, 822, 723. – 1H NMR (400 MHz,
[D6]DMSO): δ = 8.37 (s, 1H, CH-H ), 8.25 (d, J = 8.0 Hz,
2H, Ar-H), 7.53 (d, J = 8.0 Hz, 2H, Ar-H), 7.34 (d, J =
8.0 Hz, 2H, Ar-H), 7.07 (d, J = 12.0 Hz, 2H, Ar-H), 5.81 (s,
2H, CH2-H), 5.16 (s, 2H, CH2-H). – 13C NMR (100 MHz,
[D6]DMSO):δ = 157.2, 147.6, 134.8, 143.3, 129.7, 129.4,
125.7, 125.1, 124.3, 116.9, 61.8, 52.4. – MS (ESI): m/z (%) =
345 (100) [M+H]+. – HRMS ((+)-ESI):m/z = 345.0752
(calcd. 345.0754 for C16H14ClN4O3, [M+H]+).
1-(2-Methyl-5-nitrophenyl)-4-(4-propylphenyl)-1,2,3-tri-
azole (4)
◦
M. p. 93 – 95 C. – IR (KBr): ν (cm−1) = 3111, 2957,
2930, 2868, 1600, 1539, 1523, 1498, 1450, 1434, 1379,
1350, 837, 797, 710. – 1H NMR (400 MHz, [D6]DMSO):
δ = 9.07 (s, 1H, CH-H), 8.42 (d, J = 4.0 Hz, 1H, Ar-H), 8.37
(dd, J = 4.0 Hz, 12.0 Hz, 1H, Ar-H), 7.85 (dd, J = 8.0 Hz,
32.0 Hz, 3H, Ar-H), 7.32 (d, J = 8.0 Hz, 2H, Ar-H), 2.60
(t, J = 8.0 Hz, 16.0 Hz, 2H, CH2-H), 2.40 (s, 3H, CH3-H),
1.58 – 1.68 (m, 2H, CH2-H), 0.92 (t, J = 8.0 Hz, 16.0 Hz, 3H,
CH3-H). – 13C NMR (100 MHz, [D6]DMSO): δ = 147.3,
146.5, 142.7, 141.6, 137.0, 133.3, 129.3, 128.0, 125.8, 124.5,
123.2, 121.2, 37.4, 24.4, 18.6, 14.0. – MS (ESI): m/z (%) =
323 (100) [M+H]+. – HRMS ((+)-ESI): m/z = 323.1511
(calcd. 323.1508 for C18H19N4O2, [M+H]+).
5-[(3-Methoxyphenoxy)methyl]-1-(2-methyl-5-nitrophenyl)-
1,2,3-triazole (8)
◦
M. p. 93 – 95 C. – IR (KBr): ν (cm−1) = 3157, 3086,
2966, 2943, 2875, 2838, 1670, 1610, 1596, 1526, 1494,
1456, 1439, 1376, 1351, 1153, 758, 741. – 1H NMR
(400 MHz, [D6]DMSO): δ = 8.78 (s, 1H, CH-H), 8.36
(d, J= 8.0 Hz, 2H, Ar-H), 7.81 (d, J = 8.0 Hz, 1H, Ar-
H), 7.22 (t, J = 8.0 Hz, 16.0Hz, 1H, Ar-H), 6.66 – 6.69
(m, 2H, Ar-H), 6.57 (d, J = 8.0 Hz, 1H, Ar-H), 5.25 (s,
2H, CH2-H), 3.75 (s, 3H, CH3-H), 2.32 (s, 3H, CH3-H). –
13C NMR (100 MHz, [D6]DMSO): δ = 160.9, 159.7, 146.5,
143.6, 141.7, 136.9, 133.2, 130.4, 126.8, 124.6, 121.4, 107.3,
107.1, 101.4, 61.4, 55.5, 18.4. – MS (ESI): m/z (%) = 341
(100) [M+H]+. – HRMS ((+)-ESI):m/z = 341.1253 (calcd.
341.1250 for C17H17N4O4, [M+H]+).
3-(1-(2-(Trifluoromethyl)phenyl)-1,2,3-triazol-4-yl)benz-
enamine (5)
◦
M. p. 146 – 147 C. – IR (KBr): ν (cm−1) = 3396, 3120,
3090, 3074, 3050, 2925, 2854, 1627, 1607, 1590, 1512,
1491, 1462, 1450, 1350, 1313, 1279, 1178, 793, 772, 696. –
1H NMR (400 MHz, [D6]DMSO): δ = 8.85 (s, 1H, CH-
H), 8.06 (d, J = 8.0 Hz, 1H, Ar-H), 7.96 (t, J = 8.0 Hz,
16.0 Hz, 1H, Ar-H), 7.88 (t, J = 8.0 Hz, 16.0 Hz, 1H,
Ar-H), 7.81 (d, J = 8.0 Hz, 1H, Ar-H), 7.20 (s, 1H, Ar-
H), 7.11 (t, J = 8.0 Hz, 16.0 Hz, 1H, Ar-H), 7.02 (d, J =
8.0 Hz, 1H, Ar-H), 6.57 (d, J = 8.0 Hz, 1H, Ar-H), 5.25(s,
2H, NH2). – 13C NMR (100 MHz, [D6]DMSO): δ = 149.6,
147.6, 134.8, 134.4, 131.6, 130.9, 129.9, 129.8, 127.9, 127.9,
Acknowledgement
The authors would like to thank the National Natural Sci-
124.1, 121.9, 114.4, 113.6, 111.0. – MS (ESI): m/z (%) = 305 ence Foundation of China (No. 21172058) and the Henan
(100) [M+H]+. – HRMS ((+)-ESI):m/z = 305.1011 (calcd. Normal University Scientific Research Foundation for Doc-
305.1014 for C15H12N4F3, [M+H]+).
tors (No. 01036500508) for their financial support.
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