One-pot synthesis of 4,5-disubstituted 1,2,3-(NH)-triazoles using terminal acetylenes, carbon monoxide, aryl iodides, and sodium azide

Article abstract of DOI:10.1016/j.tetlet.2010.12.053

A one-pot method for the synthesis of 4,5-disubstituted-1,2,3-(NH)- triazoles via carbonylative Sonogashira reaction/1,3-dipolar cycloaddition of terminal acetylenes, carbon monoxide, aryl iodides, and sodium azide was developed. A series of new 4,5-disubstituted-1,2,3-(NH)-triazoles were prepared readily under mild conditions.

Full text of DOI:10.1016/j.tetlet.2010.12.053

Tetrahedron Letters 52 (2011) 980–982
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
One-pot synthesis of 4,5-disubstituted 1,2,3-(NH)-triazoles using terminal
acetylenes, carbon monoxide, aryl iodides, and sodium azide
⇑
Na Li, Dong Wang, Jihui Li, Weilin Shi, Chao Li, Baohua Chen
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, PR China
Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou 730000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A one-pot method for the synthesis of 4,5-disubstituted-1,2,3-(NH)-triazoles via carbonylative Sonogash-
ira reaction/1,3-dipolar cycloaddition of terminal acetylenes, carbon monoxide, aryl iodides, and sodium
azide was developed. A series of new 4,5-disubstituted-1,2,3-(NH)-triazoles were prepared readily under
mild conditions.
Received 11 October 2010
Revised 6 December 2010
Accepted 14 December 2010
Available online 21 December 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
4,5-Disubstituted 1,2,3-(NH)-triazoles
One-pot
Carbonylative
1,3-Dipolar cycloaddition
Atom economic
1,2,3-Triazoles are important nitrogen heteroarenes and have
been widely used in the pharmaceutical and agricultural indus-
tries.1 Numerous synthesis approaches for this kind of compounds
have been developed. Earlier, these compounds were typically pre-
pared by forming a mixture of 1,4-disubstituted- and 1,5-disubsti-
tuted-1,2,3-triazoles through thermal cycloaddition of azides and
alkynes.2 Recently, copper(I)-catalyzed Huisgen cycloaddition
reaction (CuAAC, often referred to as ‘click-chemistry’)3 offered a
route to synthesize 1,4-disubstituted-1,2,3-triazoles efficiently.
Especially, the Ru-catalyzed reaction of terminal alkynes with alkyl
azides was discovered to be an unique way to create 1,5-disubsti-
tuted-1,2,3-triazoles.4 However, these methods lack reactivities to-
ward unsubstituted azides (such as NaN3 and HN3) and internal
alkynes under mild conditions. It is inconvenient to prepare
4,5-disubstituted 1,2,3-(NH)-triazoles using above-mentioned
protocols5 and only a few other methods for the synthesis of 4,5-
disubstituted 1,2,3-(NH)-triazoles were developed.6 It is very nec-
essary to develop novel ways of synthesizing 4,5-disubstituted
1,2,3-(NH)-triazoles. Recently, we reported a new approach for
constructing 4,5-disubstituted 1,2,3-(NH)-triazoles based on Sono-
gashira coupling reaction.7 This method is efficient, but its imper-
fections include the requirements of copper catalyst, ultrasonic,
dry solvents, and inert atmosphere. In addition, carbonylative
cyclization is an efficient approach for synthesizing heterocycles
including indole derivatives,8 lactones,9 furan derivatives,10 quino-
line derivatives,11 and pyrrole derivatives.12 Based on our previous
work and by taking the advantages of one-pot multistep reactions
(such as minimizing waste, saving energy, and reducing operating
times),13 we report in this work an efficient, facile, and atom-eco-
nomic method to produce 4,5-disubstituted 1,2,3-(NH)-triazoles
via Pd-catalyzed carbonylative Sonogashira reaction and 1,3-dipo-
lar cycloaddition of terminal acetylenes, carbon monoxide, aryl io-
dides, and sodium azide.
In order to optimize the reaction conditions, 1-hexyne and iodo-
benzene were chosen as the test substrates. In this preliminary
experiment, 1-hexyne, carbon monoxide, iodobenzene, and so-
dium azide were added with different catalysts and base Et3N in
DMSO under the balloon pressure of CO. It was found that
PdCl2(PPh3)2 was more efficient than other catalysts such as
PdCl2/PPh3, Pd/C, PdCl2, and Pd(dba)2 (Table 1, entries 1–4). The
yields increased gradually with increasing the time of the second
step (Table 1, entries 5–7). When Et3N was replaced by other bases,
the yields decreased (Table 1, entries 8 and 9), and the even trace
product was obtained with Na2CO3 as base (Table 1, entry 10).
Thus, the optimal system for this reaction involves PdCl2(PPh3)2
(5 mol %), Et3N (4 equiv), and 36 h (the time of the second step).
We were encouraged by the above results to examine the reac-
tions with a broad range of substrates to determine the suitability
and scope of substrates.14,15 Various aryl iodides were investigated
via reacting with 1-hexyne, CO, and sodium azide.
The reaction conditions and results are summarized in Table 2.
Several electron-rich aryl iodides were suitable substrates for the
reaction, producing 4,5-disubstituted-1,2,3-(NH)-triazoles in good
⇑
Corresponding author. Tel.: +86 139 198 15840; fax: +86 931 891 2582.
E-mail address: chbh@lzu.edu.cn (B. Chen).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.12.053

N. Li et al. / Tetrahedron Letters 52 (2011) 980–982
981
Table 1
not affect the yields. In addition, the aliphatic terminal acetylenes
with longer chain can produce better yields (Table 3, entries 6–12).
Aromatic acetylenes containing electron-donating, electron-with-
drawing substituents, and heteroatom-containing were also exam-
ined and they can readily afford the corresponding 4,5-disutituted
1,2,3-trizoles under milder conditions (room temperature, 1 h) in
60–90% yields (Table 3, entries 13–18). So, the reaction conditions
are compatible with a variety of terminal acetylenes. The longer
chain aliphatic terminal acetylenes can promote the process and
the electronic properties of aromatic acetylenes do not affect the
yields.
The proposed mechanism for the involved reactions was shown
in Scheme 1. Firstly, the aryl palladium iodide species (I) was ob-
tained through the oxidative addition of aryl iodide to Pd(0), then,
the alkyne would react with the electron-deficient acylpalladium
(II) derived from the insertion of CO to (I).16 The carbonylative cou-
pling reaction product (IV) was obtained through (IIIA). Alterna-
tively, insertion of an arylalkyne to the acylpalladium species
giving (IIIB) followed by b-hydrogen elimination might be a plau-
sible pathway.17 Subsequent 1,3-dipolar cycloaddition reaction of
alkynyl ketones with sodium azide would lead to the formation
of the sodium salt of triazoles (V). The desired 4,5-disubstituted
1,2,3-(NH)-triazoles (VI) was obtained through acidating the so-
dium salt of triazoles.7
Effects of bases and catalystsa
O
1. cat., base, rt, 14h
2. NaN3, DMSO, 45 o
+
+
I
CO
C
N
N
(2a)
(1a)
Entry
N
H
(3a)
Catalyst (mol %)
Base
Timeb (h)
Yieldc (%)
1
2
3
4
5
6
7
8
9
PdCl2 (5)/PPh3 (10)
Pd/C (5)
PdCl2 (5)
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Et3N
Pyridine
tert-Butylamine
Na2CO3
36
36
36
36
12
24
36
36
36
36
78
Trace
Trace
Trace
74
78
82
36
60
Trace
Pd(dba)2 (5)
PdCl2(PPh3)2 (5)
PdCl2(PPh3)2 (5)
PdCl2(PPh3)2 (5)
PdCl2(PPh3)2 (5)
PdCl2(PPh3)2 (5)
PdCl2(PPh3)2 (5)
10
a
The reaction was carried out with iodobenzene (0.3 mmol) and base (4 equiv,
1.2 mmol) in the presence of catalyst under stirring for 10 min and then 1-hexyne
(0.45 mmol) was added. The mixture was stirred at room temperature for 14 h
under a balloon pressure of CO, then NaN3 (1.8 equiv, 0.54 mmol) and 1 mL DMSO
were added to the mixture and the reaction continued at 45 °C.
b
The time of the second step.
Isolated yields after column chromatography.
c
Interestingly, when the aryl iodides containing nitro group re-
acted with terminal acetylenes and NaN3 under CO atmosphere,
the carboxide-free 4,5-disubstituted-1,2,3-(NH)-triazoles were ob-
tained in 32–55% yields (Scheme 2), which could be attributed to
Sonogashira coupling of aryl iodides with terminal acetylenes. Be-
cause of the strong electrophilic property of nitro group, the car-
bonylative sonogashira reactions do not happen.18
In conclusion, an efficient reaction for the synthesis of 4,5-
disubstituted-1,2,3-(NH)-triazoles directly from terminal acety-
lenes, carbon monoxide, aryl iodides, and sodium azide was
to excellent yields (74–90%) as given in entries 2–6 (Table 2).
When electron-deficient aryl iodides were employed, the yields
were somewhat lower (Table 2, entries 7 and 8). Iodobenzenes
containing substituents at the 2-position gave poorer results, prob-
ably because of the steric influence (Table 2, entries 4 and 6). When
the procedure was applied to a-iodonaphthalene and b-iodonaph-
thalene, the corresponding 4,5-disubstituted-1,2,3-(NH)-triazoles
were obtained in good yield (82% and 80%, respectively, Table 2,
entries 9 and 10). The above results indicated that this reaction
was associated with the electronic properties and steric effect of
aryl iodides.
The substrate scope of terminal acetylenes was further investi-
gated. The results indicated that the reaction system can tolerate a
variety of terminal acetylenes. As shown in Table 3, 3,3-dimethyl-
1-butyne can react with various aryl iodides, and the yields were
consistent with those from 1-hexyne (Table 3, entries 1–5), indi-
cating that the branch chain of aliphatic terminal acetylene did
Table 3
Substrate scope of terminal acetylenesa
O
1. PdCl (PPh ) (5mol%)
2
3 2
R
2
R
1
Et N rt 14h
3
+
+ I R
2
R
CO
1
N
2. NaN , DMSO,
3
N
N
(1)
Entry R1
(2)
(4)
o
1-36h, rt-45
C
H
R2
Timeb (h) Product Yieldc (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
t-C4H9
3,4-(CH3)2C6H3 36
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
93
85
74
91
82
83
95
89
81
t-C4H9
t-C4H9
t-C4H9
t-C4H9
n-C8H17
n-C8H17
n-C8H17
n-C8H17
n-C8H17
n-C8H17
n-C8H17
Phenyl
4-CH3OC6H4
2-CH3OC6H4
4-CH3C6H4
4-C2H5OC6H4
Phenyl
36
36
36
36
36
Table 2
Substrate scope of aryl iodidesa
O
1. PdCl (PPh ) (5mol%)
2
3 2
R
Et N rt 14h
3
I
+
R
+
CO
3,4-(CH3)2C6H3 36
N
o
2. NaN , DMSO, 45
3
C
N
4-CH3OC6H4
2-CH3OC6H4
4-CH3C6H4
36
36
36
36
36
1
1
1
1
1
N
H
(2)
(3)
(1a)
98
86
90
Entry
R
Product
Yieldb (%)
4-C2H5OC6H4
1
2
3
4
5
6
7
8
9
Phenyl
3a
3b
3c
3d
3e
3f
3g
3h
3i
82
90
88
80
86
74
49
54
82
80
a
-Naphthyl
75d
60d
77d
90d
65d
88d
3,4-(CH3)2C6H3
4-CH3C6H4
2-CH3C6H4
4-CH3OC6H4
2- CH3OC6H4
4-ClC6H4
4-CH3C6H4
2-CH3C6H4
4-CH3OC6H4
4-CH3OC6H4
4-CH3OC6H4
Phenyl
Phenyl
4-FC6H4
Thiophen-3-yl
4-n-C5H11OC6H4 4-CH3OC6H4
1
4-BrC6H4
a
The reaction was carried out with aryl iodides (0.3 mmol) and Et3N (4 equiv,
a-Naphthyl
1.2 mmol) in the presence of PdCl2(PPh3)2 under stirring for 10 min and then ter-
minal acetylenes (0.45 mmol) were added. The mixture was stirred at room tem-
perature for 14 h under a balloon pressure of CO, then NaN3 (1.8 equiv, 0.54 mmol)
and 1 mL DMSO were added to the mixture and the reaction continued at 45 °C for
1–36 h.
10
b-Naphthyl
3j
a
The reaction was carried out with aryl iodides (0.3 mmol) and Et3N (4 equiv,
1.2 mmol) in the presence of PdCl2(PPh3)2 under stirring for 10 min and then 1-
hexyne (0.45 mmol) was added. The mixture was stirred at room temperature for
14 h under a balloon pressure of CO, then NaN3 (1.8 equiv, 0.54 mmol) and 1 mL
DMSO were added to the mixture and the reaction continued at 45 °C for 36 h.
b
The time of the second step.
Isolated yields after column chromatography.
The reaction temperature is room temperature.
c
b
d
Isolated yields after column chromatography.

982
N. Li et al. / Tetrahedron Letters 52 (2011) 980–982
2. (a) L’Abbe, G. Chem. Rev. 1969, 69, 345–363; (b) Lwowski, W. In 1,3-Dipolar
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Pearson, W. H., Eds.; Wiley: New York, 2002; p 623.
Aryl
I
Aryl Pd
I
Aryl
Pd
I
II
(
)
I
(
)
H
Et3N
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2021; (b) Rostovtsev, V. V.; Green, L. G.; Fokin, V. V.; Sharpless, K. B. Angew.
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J. C.; Burke, L. A. J. Org. Chem. 2008, 73, 1354–1364; (c) Tsai, C.-W.; Yang, S.-C.;
Liu, Y.-M.; Wu, M.-J. Tetrahedron 2009, 65, 8367–8372; (d) Jarowski, P. D.; Wu,
Y. L.; Schweizer, W. B.; Diederich, F. Org. Lett. 2008, 10, 3347–3350; (e) Kim, D.
K.; Kim, J.; Park, H. J. Bioorg. Med. Chem. Lett. 2004, 14, 2401–2405; (f) Trubulski,
E. J.; Benjamin, L.; Vitone, S.; Walser, A.; Fryer, R. I. J. Med. Chem. 1983, 26, 367–
372; (g) Yap, A. H.; Weinreb, S. M. Tetrahedron Lett. 2006, 47, 3035–3038; (h)
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3326; (c) Sengupta, S.; Duan, H. F.; Lu, W. B.; Petersen, J. L.; Shi, X. D. Org. Lett.
2008, 10, 1493–1496.
Pd(0)
O
C
O
O
C
R
Aryl
Aryl
C
Aryl
R
H
or
Pd
R
(
)
Pd
I
IV
H
(
)
IIIA
(
)
IIIB
NaN3
O
C
O
R
N
R
C
Aryl
Aryl
N
N
N
N
N
(
)
(
)
VI
V
Na
H
Scheme 1. Possible mechanism to synthesize 4,5-disubstituted 1,2,3-(NH)-
triazoles.
I
1. PdCl (PPh ) (5mol%),
NO
R
1
2
3 2
2
R
1
Et N, rt, 14h, CO
3
+
NO
2
o
N
7. Li, J. H.; Wang, D.; Zhang, Y. Q.; Li, J. T.; Chen, B. H. Org. Lett. 2009, 11, 3024–
3027.
8. (a) Gabriele, B.; Salerno, G.; Veltri, L.; Costa, M.; Massera, C. Eur. J. Org. Chem.
2001, 4607; (b) Kondo, Y.; Shiga, F.; Murata, N.; Sakamoto, T.; Yamanaka, H.
Tetrahedron 1994, 50, 11803.
9. (a) Murray, T. F.; Samsel, E. G.; Varma, V.; Norton, J. R. J. Am. Chem. Soc. 1981,
103, 7520–7528; (b) Murray, T. F.; Norton, J. R. J. Am. Chem. Soc. 1979, 101,
4107–4119.
2. NaN , DMSO, 45
C
3
N
N
(5)
(1)
(2)
H
5a: R = n-C H , 4-NO PhI, yield 53%
5b: R = n-C H , 2-NO PhI, yield 32%
1
4
9
2
1
4
9
2
5c: R = n-C H , 4-NO PhI, yield 55%
1
8
17
2
Scheme 2. Synthesis of carboxide-free 4,5-disutituted 1,2,3-trizoles.
10. (a) Kondo, Y.; Sakamoto, T.; Yamanaka, H. Heterocycles 1989, 29, 1013; (b) Nan,
Y.; Miao, H.; Yang, Z. Org. Lett. 2000, 2, 297; (c) Hu, Y.; Yang, Z. Org. Lett. 2001, 3,
1387–1390; (d) Arcadi, A.; Rossi, E. Tetrahedron Lett. 1996, 37, 6811.
11. (a) Cacchi, S.; Fabrizi, G.; Pace, P.; Marinellib, F. Synlett 1999, 620; (b) Dai, G.;
Larock, R. C. J. Org. Chem. 2002, 67, 7042–7047.
12. Arcadi, A.; Anacardio, R.; D’Anniballe, G.; Gentile, M. Synlett 1997, 1315.
13. (a) Kamijo, S.; Jin, T.; Yamamoto, Y. Tetrahedron Lett. 2004, 45, 689–691; (b)
Zhao, Y.-B.; Yan, Z.-Y.; Liang, Y.-M. Tetrahedron Lett. 2006, 47, 1545–1549.
14. Typical procedure for the preparation of 4,5-disubstituted-1,2,3-(NH)-triazoles
developed based on carbonylative Sonogashira reaction in one pot.
The procedure is suitable to many substrates. Different 4,5-disub-
stituted-N-unsubstituted 1,2,3-triazoles can be produced using
cheap and easily available starting materials. The developed meth-
od is atom economic and performed easily, making it possibly
acceptable for industrial-scale production.
(synthesis of 3a):
A round-bottom sidearm flask (10 mL) containing
PdCl2(PPh3)2 (0.015 mmol) was subjected to the Schlenk-line procedures of
evacuation and purging of CO for three cycles. Iodobenzene and 4 equiv Et3N
(1.2 mmol) were successively added, and the mixture was stirred at room
temperature for 10 min, then 1-hexyne (0.45 mmol) was added, continuously
stirred at room temperature for 14 h. Then NaN3 (35.1 mg, 0.54 mmol) and
1 mL DMSO were added to the mixture and the reaction continued at 45 °C for
36 h. Following, to the reaction mixture was added water (2 mL), 20% HCl
solution (1 mL) and extracted with ether (3 Â 10 mL). The combined organic
phases were washed with brine (2 Â 5 mL), dried over anhydrous MgSO4 and
concentrated in vacuo. The residue was subjected to flash column
chromatography with hexanes/EtOAc (5/1) as eluent to obtain the desired 3a
(56.33 mg, 82% yield). All products gave satisfactory spectroscopic and
analytical data.
Acknowledgments
We are grateful to the project sponsored by the Scientific
Research Foundation for the State Education Ministry (No.
107108) and the Project of the National Science Foundation of PR
China (No. J0730425).
Supplementary data
15. Spectroscopic data for representative examples: (5-butyl-2H-1,2,3-triazol-4-
yl)(3,4-dimethylphenyl)methanone (3b, Table 2, entry 2): mp: 71–73 °C. IR
(cmÀ1):3166.68, 2959.12, 1646.18, 1472.08, 1325.62, 1258.03, 1118.52. 1H
NMR (400 MHz, CDCl3): d 8.00 (d, J = 6.0 Hz, 2H), 7.25 (t, J = 8.0 Hz, 1H), 3.06 (t,
J = 7.8 Hz, 2H), 2.32 (d, J = 4.8 Hz, 6H), 1.64–1.78 (m, 2H), 1.31–1.40 (m, 2H),
0.88 (t, J = 7.4 Hz, 3H). 13C NMR (100 MHz, CDCl3): d 187.64, 147.40, 142.74,
142.08, 136.68, 135.17, 131.29, 129.56, 128.24, 30.62, 24.34, 22.35, 20.01,
19.71, 13.64. MS m/z: 257 (M+, 30%), 242 (100), 228 (11), 214 (16), 200 (55),
133 (45), 122 (46), 105 (48), 77 (48), 41 (51). Anal. Calcd for C15H19N3O: C,
70.01; H, 7.44; N, 16.33. Found: C, 70.05; H, 7.46; N, 16.38. (5-Butyl-2H-1,2,3-
triazol-4-yl)(4-methoxyphenyl)methanone (3e, Table 2, entry 5): IR (cmÀ1):
3171.25, 2931.41, 1598.72, 1467.64, 1260.70, 1151.33, 921.09. 1H NMR
(400 MHz, CDCl3): d 8.32 (d, J = 8.8 Hz, 2H), 6.98 (d, J = 8.8 Hz, 2H), 3.87 (s,
3H), 3.08 (t, J = 7.8 Hz, 2H), 1.70 (t, J = 7.4 Hz, 2H), 1.34–1.39 (m, 2H), 0.87–0.91
(m, 3H). 13C NMR (100 MHz, CDCl3): d 186.35, 163.65, 147.38, 142.17, 132.87,
130.10, 113.59, 55.44, 30.63, 24.39, 22.37, 13.66. MS m/z: 259 (M+, 21%), 216
(55), 186 (41), 135 (100). Anal. Calcd for C14H17N3O2: C, 64.85; H, 6.61; N,
16.20. Found: C, 64.87; H, 6.67; N, 16.23. See Supplementary data for spectral
data of all other compounds.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2010.12.053.
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