Direct Synthesis of N-Unsubstituted 4-Aryl-1,2,3-triazoles Mediated by Amberlyst-15

Article abstract of DOI:10.1055/s-0035-1560488

A highly efficient and effective method for the synthesis of N-unsubstituted 4-aryl-1,2,3-triazoles promoted by Amberlyst-15 is described. The promoter can be recycled and reused up to eight times without any reduction in its catalytic activity.

Full text of DOI:10.1055/s-0035-1560488

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2016, 48, 131–135
paper
131
H. Zhang et al.
Paper
Synthesis
Direct Synthesis of N-Unsubstituted 4-Aryl-1,2,3-triazoles Mediated
by Amberlyst-15
Hui Zhang1
Dao-Qing Dong1
recycle
Zu-Li Wang*
N
N
College of Chemistry and Pharmaceutical Sciences,
Qingdao Agricultural University, Qingdao, 266109,
P. R. of China
NO2
NH
Amberlyst-15
DMF, 50 °C
R
NaN3
+
R
wangzulichem@163.com
up to 95% yield
Received: 06.08.2015
Accepted after revision: 14.09.2015
Published online: 28.09.2015
screening experiments, the effects of various solvents and
different temperatures on the yields of the model reaction
were examined. To our delight, a high yield (95%) of the de-
sired product was obtained when the reaction was con-
ducted in N,N-dimethylformamide (Table 1, entry 2). The
use of dimethyl sulfoxide as the solvent led to a slower re-
action and a lower yield (Table 1, entry 1). Poor yields of the
desired product were obtained when the reactions were
performed in acetonitrile, ethanol and tetrahydrofuran (Ta-
ble 1, entries 3–5). Only a trace amount of the desired prod-
DOI: 10.1055/s-0035-1560488; Art ID: ss-2015-h0467-op
Abstract A highly efficient and effective method for the synthesis of
N-unsubstituted 4-aryl-1,2,3-triazoles promoted by Amberlyst-15 is de-
scribed. The promoter can be recycled and reused up to eight times
without any reduction in its catalytic activity.
Key words N-unsubstituted 1,2,3-triazoles, Amberlyst-15, 1,3-dipolar
cycloadditions
Table 1 Optimization of the Reaction Conditionsa
The synthesis of 1,2,3-trizoles has received significant
attention in recent years due to their wide applications in
organic synthesis, biology and materials science.2 At pres-
ent, N1-substituted 1,2,3-triazoles can be readily obtained
via Huisgen azide–alkyne 1,3-dipolar cycloadditions (AACs),3
transition-metal-catalyzed azide–alkyne cycloadditions,4
organocatalyzed azide–ketone cycloadditions,5 etc.6 How-
ever, the preparation of N-unsubstituted 4-aryl-1,2,3-tri-
azoles is still a challenging task. At present, only a few
methods can be used to synthesize N-unsubstituted 4-aryl-
1,2,3-triazoles: copper(I)-mediated azide–alkyne cycload-
ditions,7 reactions between alkenyl bromides and sodium
azide,8 and 1,3-dipolar cycloadditions of nitroolefins and
sodium azide.9 Therefore, the development of more versa-
tile and practical methods for the synthesis of N-unsubsti-
tuted 4-aryl-1,2,3-triazoles are still desirable. In continua-
tion of our previous studies on developing improved meth-
odologies for organic reactions, herein, we report an
efficient and ecofriendly method for the synthesis of N-un-
substituted 4-aryl-1,2,3-triazoles mediated by Amberlyst-
15.
N
N
NO2
+
NH
Amberlyst-15
solvent
NaN3
2a
1a
3a
Entry
Solvent
Temp (°C)
Yield (%)b
1
2
DMSO
DMF
50
50
50
50
50
50
30
50
50
50
79
95
11
30
8
3
MeCN
EtOH
THF
4
5
6
toluene
DMF
trace
65
96
89
10
7
8c
9d
10e
DMF
DMF
DMF
a Reaction conditions: 1a (0.2 mmol), 2a (0.3 mmol), Amberlyst-15 (30
mg), solvent (2 mL), under air.
At the beginning of our studies, we attempted to opti-
mize the reaction conditions for the Amberlyst-15-mediat-
ed 1,3-dipolar cycloaddition reaction by using nitroolefin
1a with sodium azide (2a) as a model system. In our initial
b Yield of isolated product.
c Amberlyst-15 (40 mg) was used.
d Amberlyst-15 (20 mg) was used.
e No catalyst was used.
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132
H. Zhang et al.
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Synthesis
uct was isolated when the reaction was carried out in tolu-
ene (Table 1, entry 6). The reaction temperature also played
an important role in this system. The yield of the reaction
decreased significantly when it was carried out at 30 °C (Ta-
ble 1, entry 7). There was no significant improvement in the
yield when the amount of the catalyst was increased (Table
1, entry 8). However, the yield decreased slightly (89%)
when the amount of the catalyst was reduced (Table 1, en-
try 9). Only a 10% yield of the desired product was obtained
when no catalyst was employed (Table 1, entry 10).
After optimizing the reaction conditions, a range of ni-
troolefins was used to investigate the scope of the reaction
(Figure 1). Generally speaking, there was no apparent dif-
ference in the product yield when using different nitroole-
fins. All of the examined nitroolefins were excellent sub-
strates regardless of the presence of electron-donating
(3d,i,n,p) or electron-withdrawing groups (3c,f–h,j,k,m,q)
on the benzene rings. It is worth mentioning that heterocy-
clic-substituted nitroolefin 3r was also a good substrate for
this reaction, affording the desired product in 80% yield.
Additionally, steric hindrance had little effect on this sys-
tem. Nitroolefins with substituents at ortho-, meta- and
para-positions of the benzene ring all reacted smoothly
with sodium azide to afford the corresponding products in
good to excellent yields (3b,e,l,o). Unfortunately, alkyl-sub-
stituted and disubstituted nitroolefins were not suitable
substrates for this reaction.
N
N
N
N
N
N
N
N
NH
NH
NH
NH
NH
Br
O2N
3a, 95%
3b, 90%
3e, 91%
3c, 94%
N
N
N
N
NH
NC
OMe
Cl
3d, 90%
3g, 87%
3f, 88%
N
N
N
N
N
NO2
N
NH
NH
NH
MeO
F
3h, 89%
3i, 96%
N
N
N
N
N
N
Br
NH
NH
NH
F3C
NC
3j, 90%
3l, 93%
CF3
3k, 90%
N
N
N
N
Cl
N
N
Cl
NH
NH
NH
Cl
Excellent results were also obtained when this method
was performed on gram scale (Scheme 1). This indicates
that this reaction may have good synthetic utility in indus-
try.
3m, 94%
3n, 92%
3o, 95%
N
N
N
N
N
N
Finally, the recycling of the Amberlyst-15 catalyst was
investigated in the reaction between nitrostyrene 1a and
sodium azide (Table 2). After the reaction was complete, the
solution was filtered under vacuum using a sintered glass
funnel and the Amberlyst-15 was washed with dichloro-
NH
NH
NH
Cl
O
3p, 93%
3q, 85%
3r, 80%
Figure 1 1,3-Dipolar cycloadditions of nitroolefins with NaN3 for the
synthesis of N-unsubstituted 4-aryl-1,2,3-triazoles. Reaction conditions:
1 (0.2 mmol), 2 (0.3 mmol), Amberlyst-15 (30 mg), DMF (2 mL), under
air.
Table 2 Recycling of the Amberlyst-15 Catalysta
N
N
NO2
+
NH
Amberlyst-15
DMF
methane, ethanol, and hexane, respectively. The recovered
catalyst was dried and then reused directly without further
purification. The catalyst could be recovered and reused up
to eight times with no loss of its catalytic activity.
NaN3
1a
Entry
2a
3a
Yield (%)
Yield (%)
Entry
N
N
1
2
3
4
95
96
94
93
5
6
7
8
95
92
93
91
NH
NO2
Amberlyst-15
NaN3
2a
+
DMF, 50 °C
86%
1a
3a
1.247 g
Scheme 1 A gram-scale preparation of 4-phenyl-1H-1,2,3-triazole (3a)
10 mmol, 1.49 g 13 mmol, 0.845 g
a Reaction conditions: 1a (0.2 mmol), 2a (0.3 mmol), Amberlyst-15 (30
mg), DMF (2 mL), under air.
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In summary, a highly efficient method for the synthesis
of N-unsubstituted 4-aryl-1,2,3-triazoles has been de-
scribed. A wide range of functional groups is tolerated us-
ing this system, and good to excellent yields of the products
were obtained. Furthermore, the catalyst could be recov-
ered by simple filtration and reused up to eight times with-
out any significant decrease in its catalytic activity. Further
investigations and mechanistic studies are ongoing in our
laboratory in order to identify more effective and economic
systems for the synthesis of 1,2,3-triazoles.
4-(3-Bromophenyl)-1H-1,2,3-triazole (3b)9
Yield: 40.3 mg (90%); white solid.
1H NMR (500 MHz, CDCl3): δ = 7.99 (d, J = 10.0 Hz, 2 H), 7.76 (d, J = 8.0
Hz, 1 H), 7.51 (d, J = 8.0 Hz, 1 H), 7.33 (t, J = 8.0 Hz, 1 H).
13C NMR (126 MHz, CDCl3): δ = 131.99, 131.70, 130.51, 129.14,
124.67, 123.09.
LC–MS (ESI): m/z = 221.89 [M – H]+.
4-(3-Nitrophenyl)-1H-1,2,3-triazole (3c)9
Yield: 35.7 mg (94%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.69–8.66 (m, 1 H), 8.63 (s, 1 H),
8.33 (d, J = 8.0 Hz, 1 H), 8.21 (dd, J = 8.0, 1.5 Hz, 1 H), 7.77 (t, J = 8.0 Hz,
1 H).
13C NMR (126 MHz, DMSO-d6): δ = 148.86, 144.20, 132.75, 132.20,
131.04, 129.11, 123.03, 120.19.
All major chemicals and solvents were obtained from commercial
sources and were used without further purification. Column chroma-
tography was performed using Shenghai silica gel (200–300 mesh).
Petroleum ether (PE) refers to the fraction boiling in the 60–90 °C
range. Melting points were determined using an X4/X4A digital
display microscopic melting point detector apparatus. IR spectra were
recorded on a Nicolet IR200 spectrophotometer. 1H NMR (500 MHz)
and 13C NMR (126 MHz) spectra were recorded using a JOEL JNM-ECA
500 spectrometer. 1H NMR chemical shifts (δ) are given in ppm rela-
tive to TMS (δ = 0.0). 13C NMR chemical shifts are reported in parts
per million (ppm) relative to TMS with the solvent as the internal
standard. 1H NMR data are reported as follows: chemical shift, multi-
plicity (s = singlet, d = doublet, dd = doublet of doublets, t = triplet,
m = multiplet), coupling constant, integration. LC–MS (ESI) were ob-
tained using an Agilent 1290 Infinity/6460 UHPLC/MS/MS instru-
ment. GC–MS (EI) analysis was performed using an Agilent
5975B/6890N GC/MS instrument. High-resolution mass spectra were
recorded on a Thermo exactive mass spectrometer.
LC–MS (ESI): m/z = 189.00 [M – H]+.
4-(2-Methoxyphenyl)-1H-1,2,3-triazole (3d)9
Yield: 31.5 mg (90%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.19 (s, 1 H), 7.99 (s, 1 H), 7.35 (t,
J = 7.5 Hz, 1 H), 7.14 (d, J = 8.5 Hz, 1 H), 7.05 (t, J = 7.5 Hz, 1 H), 3.91 (s,
3 H).
13C NMR (126 MHz, DMSO-d6): δ = 156.31, 129.72, 127.87, 121.14,
112.16, 55.93.
LC–MS (ESI): m/z = 174.00 [M – H]+.
4-(4-Chlorophenyl)-1H-1,2,3-triazole (3e)9
Yield: 32.6 mg (91%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.40 (s, 1 H), 8.01–7.82 (m, 2 H),
7.67–7.40 (m, 2 H).
N-Unsubstituted 4-Aryl-1,2,3-triazoles; General Procedure
A 25 mL Schlenk tube equipped with a magnetic stir bar was charged
with the nitroolefin (0.2 mmol), NaN3 (0.3 mmol), DMF (2 mL) and
Amberlyst-15 (30 mg). The tube was sealed and heated at 50 °C in air
for 1–3 h. After completion of the reaction (as indicated by TLC), the
resulting solution was extracted with EtOAc (3 × 10 mL). The com-
bined organic layer was dried over anhydrous Na2SO4, filtered, and
concentrated under vacuum. The residue was chromatographed on a
silica gel column (PE–EtOAc) to give the pure product.
13C NMR (126 MHz, DMSO-d6): δ = 133.11, 130.48, 129.34, 127.66.
LC–MS (ESI): m/z = 177.96 [M – H]+.
3-(1H-1,2,3-Triazol-4-yl)benzonitrile (3f)9
Yield: 30.0 mg (88%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.50 (d, J = 5.0 Hz, 1 H), 8.30 (d,
J = 7.5 Hz, 1 H), 8.21 (t, J = 7.5 Hz, 1 H), 7.89–7.73 (m, 1 H), 7.67 (dd,
J = 16.5, 8.5 Hz, 1 H).
13C NMR (126 MHz, DMSO-d6): δ = 144.40, 132.21, 131.99, 130.73,
130.43, 129.30, 119.04, 112.56.
The procedure for the large-scale synthesis was the same as that de-
scribed above. A 250 mL Schlenk tube equipped with a magnetic stir
bar was charged with the nitroolefin (10 mmol), NaN3 (13 mmol),
DMF (100 mL) and Amberlyst-15 (1.5 g). The tube was sealed and
heated at 50 °C in air. After completion of the reaction (as indicated
by TLC), the resulting solution was extracted with EtOAc. The organic
layer was dried over anhydrous Na2SO4, and concentrated under vac-
uum. The residue was chromatographed on a silica gel column (PE–
EtOAc) to give the pure product.
LC–MS (ESI): m/z = 169.00 [M – H]+.
4-(4-Fluorophenyl)-1H-1,2,3-triazole (3g)9
Yield: 28.3 mg (87%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.34 (s, 1 H), 7.91 (dd, J = 7.5, 5.5
Hz, 2 H), 7.30 (t, J = 8.5 Hz, 2 H).
13C NMR (126 MHz, DMSO-d6): δ = 163.38, 161.43, 145.06, 128.06 (d,
JC–F = 8.2 Hz), 127.86, 116.28 (d, JC–F = 21.7 Hz).
LC–MS (ESI): m/z = 162.00 [M – H]+.
4-Phenyl-1H-1,2,3-triazole (3a)9
Yield: 27.5 mg (95%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 15.16 (s, 1 H), 8.67–8.06 (m, 1 H),
7.88 (d, J = 5.0 Hz, 2 H), 7.47 (s, 2 H), 7.37 (s, 1 H).
13C NMR (126 MHz, DMSO-d6): δ = 162.79, 130.99, 129.39, 128.59,
127.73, 126.04.
LC–MS (ESI): m/z = 144.00 [M – H]+.
4-(2-Nitrophenyl)-1H-1,2,3-triazole (3h)9
Yield: 33.8 mg (89%); white solid.
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1H NMR (500 MHz, DMSO-d6): δ = 8.26 (s, 1 H), 7.92 (d, J = 8.0 Hz, 1
H), 7.84 (dd, J = 7.5, 1.0 Hz, 1 H), 7.76 (dd, J = 14.5, 7.5 Hz, 1 H), 7.63 (t,
J = 7.5 Hz, 1 H).
13C NMR (126 MHz, DMSO-d6): δ = 146.27, 137.51, 129.50, 127.90,
125.57, 20.85.
LC–MS (ESI): m/z = 158.00 [M – H]+.
13C NMR (126 MHz, DMSO-d6): δ = 148.89, 132.95, 131.00, 129.99,
4-(2-Chlorophenyl)-1H-1,2,3-triazole (3o)9
124.34, 124.05.
LC–MS (ESI): m/z = 188.99 [M – H]+.
Yield: 34.1 mg (95%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.35 (s, 1 H), 7.91 (dd, J = 8.0, 1.5
Hz, 1 H), 7.61–7.50 (m, 1 H), 7.49–7.30 (m, 2 H).
4-(3-Methoxyphenyl)-1H-1,2,3-triazole (3i)9
Yield: 33.6 mg (96%); white solid.
1H NMR (500 MHz, CDCl3): δ = 7.92 (s, 1 H), 7.37–7.23 (m, 3 H), 6.86
(d, J = 8.0 Hz, 1 H), 3.79 (s, 3 H).
13C NMR (126 MHz, DMSO-d6): δ = 142.73, 131.38, 130.67, 130.14,
129.57, 127.96.
LC–MS (ESI): m/z = 177.97 [M – H]+.
13C NMR (126 MHz, CDCl3): δ = 160.09, 130.09, 118.63, 114.66,
111.41, 55.38.
LC–MS (ESI): m/z = 174.00 [M – H]+.
4-(3,4-Dimethylphenyl)-1H-1,2,3-triazole (3p)
Yield: 32.1 mg (93%); white solid; mp 167–168 °C.
IR (KBr): 3136, 1615, 1561, 1488, 1451, 1395, 888, 820 cm–1
1H NMR (500 MHz, DMSO-d6): δ = 8.24 (s, 1 H), 7.64 (s, 1 H), 7.57 (d,
J = 8.0 Hz, 1 H), 7.19 (d, J = 8.0 Hz, 1 H), 2.24 (d, J = 16.0 Hz, 6 H).
13C NMR (126 MHz, DMSO-d6): δ = 137.21, 136.76, 130.43, 128.15,
127.11, 123.49, 19.82, 19.58.
GC–MS (EI): m/z = 173.0 [M]+.
HRMS (ESI): m/z [M + H]+ calcd for C10H11N3: 174.10257; found:
.
4-(1H-1,2,3-Triazol-4-yl)benzonitrile (3j)9
Yield: 30.6 mg (90%); yellow solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.57 (s, 1 H), 8.16–8.01 (m, 2 H),
7.93 (dd, J = 8.0, 4.0 Hz, 2 H).
13C NMR (126 MHz, DMSO-d6): δ = 144.79, 135.57, 133.39, 126.56,
119.24, 110.79.
LC–MS (ESI): m/z = 169.00 [M – H]+.
174.10258.
4-[3,5-Bis(trifluoromethyl)phenyl]-1H-1,2,3-triazole (3k)7b
4-(3-Chlorophenyl)-1H-1,2,3-triazole (3q)
Yield: 50.6 mg (90%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.62 (s, 1 H), 8.44 (s, 2 H), 7.91 (s, 1
H).
13C NMR (126 MHz, DMSO-d6): δ = 143.54, 133.75, 131.85, 131.59,
131.32, 131.06, 126.85, 125.98, 124.68, 122.51, 121.24, 120.35.
LC–MS (ESI): m/z = 279.99 [M – H]+.
Yield: 30.5 mg (85%); white solid; mp 172–173 °C.
IR (KBr): 1602, 1569, 1462, 1447, 799 cm–1
.
1H NMR (500 MHz, DMSO-d6): δ = 8.44 (s, 1 H), 7.93 (t, J = 1.5 Hz, 1 H),
7.84 (d, J = 8.0 Hz, 1 H), 7.47 (t, J = 8.0 Hz, 1 H), 7.39 (dd, J = 7.5, 1.0 Hz,
1 H).
13C NMR (126 MHz, DMSO-d6): δ = 144.68, 134.26, 132.92, 131.06,
128.19, 125.62, 124.46.
GC–MS (EI): m/z = 178.9 [M]+.
HRMS (ESI): m/z [M + H]+ calcd for C8H6ClN3: 180.03230; found:
180.03224.
4-(2-Bromophenyl)-1H-1,2,3-triazole (3l)9
Yield: 41.6 mg (93%); white solid.
1H NMR (500 MHz, CDCl3): δ = 8.30 (s, 1 H), 7.83 (d, J = 7.5 Hz, 1 H),
7.76–7.63 (m, 1 H), 7.42 (dd, J = 14.0, 7.5 Hz, 1 H), 7.27 (dd, J = 11.5,
5.0 Hz, 1 H).
13C NMR (126 MHz, CDCl3): δ = 133.73, 131.02, 130.77, 129.98,
127.73, 121.93.
4-(Furan-2-yl)-1H-1,2,3-triazole (3r)9
Yield: 21.6 mg (80%); white solid.
1H NMR (500 MHz, CDCl3): δ = 7.89 (s, 1 H), 7.42 (d, J = 1.0 Hz, 1 H),
6.76 (d, J = 3.5 Hz, 1 H), 6.42 (dd, J = 3.5, 1.5 Hz, 1 H).
LC–MS (ESI): m/z = 221.90 [M – H]+.
13C NMR (126 MHz, CDCl3): δ = 145.26, 142.80, 139.24, 128.22,
111.61, 107.79.
LC–MS (ESI): m/z = 134.00 [M – H]+.
4-(2,4-Dichlorophenyl)-1H-1,2,3-triazole (3m)9
Yield: 40.2 mg (94%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 8.42 (s, 1 H), 7.97 (d, J = 8.5 Hz, 1
H), 7.76 (s, 1 H), 7.60–7.41 (m, 1 H).
13C NMR (126 MHz, DMSO-d6): δ = 141.97, 133.72, 132.17, 131.73,
130.14, 128.80, 128.24.
Acknowledgment
Financial support from the National Natural Science Foundation of
China (21402103), the research fund of Qingdao Agricultural Univer-
sity’s High-Level Person [631303], and the Scientific Research Foun-
dation of Shandong Province Outstanding Young Scientist Award
[BS2013YY024] are gratefully acknowledged. We thank Wen-Hui
Zhai, Da-An Song, Qing-Nan Li, Peng-Chao Jiang and Cui-Hua Cao for
preparing the Supporting Information and for their helpful discus-
sions.
LC–MS (ESI): m/z = 211.90 [M – H]+.
4-(p-Tolyl)-1H-1,2,3-triazole (3n)9
Yield: 29.2 mg (92%); white solid.
1H NMR (500 MHz, DMSO-d6): δ = 15.03 (s, 1 H), 8.27 (s, 1 H), 7.75 (d,
J = 8.0 Hz, 2 H), 7.27 (d, J = 8.0 Hz, 2 H), 2.33 (s, 3 H).
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Supporting Information
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Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0035-1560488.
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