Palladium-Catalyzed Nitration of Arenes by 1,2,3-Triazole-Directed C-H Activation

Article abstract of DOI:10.1055/s-0035-1561951

An efficient palladium-catalyzed regioselective nitration of 1,4-disubstituted 1,2,3-triazoles has been described with good functional group compatibility, using Pd(OAc)₂ as the catalyst and NaNO₂ as the nitration source, leading to

Full text of DOI:10.1055/s-0035-1561951

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2016, 48, A–G
paper
A
F. Zhao et al.
Paper
Synthesis
Palladium-Catalyzed Nitration of Arenes by 1,2,3-Triazole-Directed
C–H Activation
Fen Zhaoa
R2
R2
Pd(OAc)2 (10 mol%)
NaNO2 (1.5 equiv)
K2S2O8 (2.0 equiv)
Zhen Chena
Shaojun Huangb
Yubo Jiang*a
R1
R1
N
N
N
H
DMSO, 120 °C, 18 h
N
NO2
N
N
R1, R2 = H, CH3, OCH3,
halogen
a Faculty of Science, Kunming University of Science and
Technology, Kunming 650500, P. R. of China
ybjiang@kmust.edu.cn
b Research Center for Analysis and Measurement, Kunming
University of Science and Technology, Kunming 650093,
P. R. of China
Direct C–N bond formation
21 examples, yield up to 92%
Received: 09.01.2016
Accepted after revision: 26.02.2016
Published online: 06.04.2016
heterocycles as directing groups, and AgNO2 as nitro source.
From then on, NO2,11 MNO2,12 and t-BuONO13 were used as
nitro source in the direct ortho-nitration of aromatic C–H
bond. Additionally, a similar chelation-directed strategy
was explored in several copper-,14 and rhodium15-catalyzed
ortho-nitrations of aryl sp2 C–H bonds with various nitro
sources, respectively, using N-heterocycles as directing
groups.
DOI: 10.1055/s-0035-1561951; Art ID: ss-2016-h0015-op
Abstract An efficient palladium-catalyzed regioselective nitration of
1,4-disubstituted 1,2,3-triazoles has been described with good func-
tional group compatibility, using Pd(OAc)2 as the catalyst and NaNO2 as
the nitration source, leading to the synthesis of 1,2,3-triazoles contain-
ing nitro groups in good to excellent yields.
1,2,3-Triazoles are known to play a very important role
in organic chemistry as they are widely applied in various
fields including synthetic organic chemistry,16 biological
science,17 medicinal chemistry,18 and materials science.19 In
recent years, Kuang’s group20 achieved the Pd-catalyzed di-
rect C–H bond halogenation, arylation, alkoxylation, acyla-
tion, and acyloxylation of 2-monosubstituted 1,2,3-tri-
azoles, using the triazole ring as the directing group. At the
same time, transition-metal-catalyzed arylation of the C-4
or C-5 position of 1,4-disubstituted 1,2,3-triazoles were
also demonstrated.21 However, to the best of our knowl-
edge, there is still no report on the transition-metal-cata-
lyzed direct nitration of 1,2,3-triazoles. Herein, we report
on the first examples of palladium-catalyzed regioselective
nitration of arenes through 1,2,3-triazole-directed C–H ac-
tivation.
An initial investigation of the reaction conditions, in-
cluding catalyst (10% mol), oxidant, temperature, and sol-
vent, was conducted under dioxygen atmosphere, using the
nitration of 4-phenyl-1-(p-tolyl)-1H-1,2,3-triazole (1a) as a
model (Table 1). First, several palladium catalysts were
screened using NaNO2 (1.5 equiv) as a nitro source and
K2S2O8 (2 equiv) as an oxidant in DMSO at 120 °C for 18
hours. It was found that PdCl2, Pd2(dba)3, and PdCl2(PPh3)
showed low catalytic activity (Table 1, entries 1–3). Howev-
er, Pd(OAc)2 exhibited excellent efficiency to give the de-
Key words palladium, C–H activation, 1,4-disubstituted 1,2,3-tri-
azoles, nitration, regioselectivity
Transition-metal-catalyzed C–H bond functionaliza-
tions are effective, attractive, and ideal reactions, which en-
able the efficient construction of carbon–carbon or carbon–
heteroatom bonds as a highly atom-economical and direct
approach.1 The second-row transition metals, such as Ru,2
Rh,3 and Pd,4 have been considerably explored for this pur-
pose. Typically, C–H bond activation requires the combina-
tion of transition metals and directing groups to facilitate
regioselective C–H bond cleavage. Sulfoximine,5 pyridine,6
azo group,7 and carboxylic acids8 have been explored as ef-
fective directing groups (DGs) to assist selective C–H bond
functionalization and employed in a variety of reactions.
In the past decade, the area of transition-metal-cata-
lyzed chelation-assisted inert C–H bond functionalization
has witnessed great progress;9 thus, it has become a re-
markable strategy in the regioselective construction of a va-
riety of carbon–carbon or carbon–heteroatom bonds with
features of step-economics and green chemistry. With this
concept, a series of synthetic methods for nitroarenes (con-
structing C–N bond) have been developed. For example, in
2010, Liu’s group10 developed the palladium-catalyzed
ortho-specific nitration of aromatic C–H bonds by using N-
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

B
F. Zhao et al.
Paper
Synthesis
sired product 2a in 86% yield (entry 4). The reaction gave
inferior results when the catalyst loading were decreased to
5 mol% (entry 5). Increasing or decreasing the reaction tem-
perature did not favor the nitration (entries 6, 7). We then
examined the influence of oxidant including K2S2O8, AgOAc,
Cu(OAc)2, DDQ, and PhI(OAc)2, among which K2S2O8 was
found to be the most suitable oxidant (entry 4, entries 8–
11). However, control experiments (entry12) showed that
the reaction failed to give the desired product only in the
oxygen atmosphere without other oxidant. Finally, several
solvents were surveyed for the reaction, and it was found
that no target molecules were detected in DMF, MeOH (en-
tries 13,14). Additionally, other solvents, including TFA, tol-
uene, p-xylene, and DCE, showed low efficiency (entries
16–18). Thus, the optimized reaction conditions for the ni-
tration of 4-phenyl-1-(p-tolyl)-1H-1,2,3-triazole (1a) was
established as Pd(OAc)2 (10% mol), NaNO2 (1.5 equiv), and
K2S2O8 (2 equiv) in DMSO at 120 °C for 18 hours.
With the optimized reaction conditions in hand, we
turned our attention to investigate the scope of the sub-
strates. The results are summarized in Scheme 1. A series of
arenes carrying either an electron-donating substituent
such as methyl, methoxy (Scheme 1, 2a–i, u) or an electron-
withdrawing group (F, Cl, Br) (2j–r) proceeded smoothly.
Substrates bearing an electron-donating group at the para-
or ortho-position of the arenes of 1,2,3-triazoles all gave the
corresponding products in good to excellent yields (2a,b,e,f
and 2j vs 2l). However, substrates possessing electron-with-
drawing group (Br) at the arenes of C-1 and/or C-4 position
of 1,2,3-triazoles could deliver the desired products only in
somewhat lower yields (2l–n); the reason may be that halo-
gen (Br) may cause some side reactions. Additionally, sub-
strates substituted with Br group at the 2-position of C-1
aryl of 1,2,3-triazoles resulted in lower yield compared with
that at the 3-position (2l vs 2m). The reactions of arenes
carrying a group at the para-position could furnish ni-
troarenes in higher yields than the ortho-substituted ones
(2a vs 2b, 2e vs 2f, 2m vs 2n, and 2o vs 2p), which may be
owing to the steric hindrance of the latter. The molecules
with Br at the 2-position of C-1 aryl of 1,2,3-triazoles re-
sulted in lower yield than that with a Cl group (2m vs 2o);
the reason may be that bromine is more active and causes
more side reactions. Notably, substrates possessing an elec-
tron-withdrawing group (F) or an electron-donating (meth-
yl) at the ortho- position of C-4 arenes of 1,2,3-triazoles
could also deliver the desired products in good yields
(2q–u).
On the basis of the above experiments and previous re-
ports,12a a plausible mechanism for the palladium-catalyzed
nitration of 1,4-diphenyl-1H-1,2,3-triazole (1c) is proposed
in Scheme 2. First, selective coordination of electron-richer
N(3)22 in 1,2,3-triazole 1c to Pd(II) species followed by ortho
C–H activation forms the five-membered palladacycle A.
Then, addition of NO2 radicals (the radical may be generat-
ed from NaNO2 through an oxidation process) to the metal
center generates PdIV species B.12a Reductive elimination
from the PdIV center gives the target product 2c and regen-
erates the PdII catalyst.
In addition, some applications of the synthesized prod-
ucts were investigated. One of the most important process
is to transform the obtained nitroarenes to aromatic amine
molecules, which are versatile intermediates and precur-
sors in the preparation of dyes, pharmaceuticals, pigments,
agrochemicals, and polymers.23 According to reported
methods,24 some experiments were carried out to reduce
the nitroarenes by adding Fe, Zn, and NaBH4, respectively, to
the system as a reductant through a one-pot manipulation
when the nitration process was finished. However, the
product mixture was complex, as observed by TLC, and fur-
ther study is ongoing in our lab.
Table 1 Optimization of Reaction Conditionsa
catalyst
NaNO2 (1.5 equiv)
oxidant (2.0 equiv)
N
N
solvent, 18 h
N
NO2
N
N
N
1a
2a
Entry Catalyst
Oxidant
Temp (°C) Solvent
Yield (%)b
1
2
PdCl2
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
AgOAc
Cu(OAc)2
DDQ
120
120
120
120
120
110
130
120
120
120
120
120
120
120
120
120
120
120
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
35
40
22
86
72c
68
70
21
45
0
Pd2(dba)3
PdCl2(PPh3)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
PhI(OAc)2
O2
trace
0
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
K2S2O8
0
MeOH
TFA
0
38
21
18
23
toluene
p-xylene
DCE
a Reaction conditions (unless otherwise noted): compound 1a (0.2 mmol),
[Pd] (0.02 mmol), NaNO2 (0.3 mmol), oxidant (0.4 mmol) in DMSO (1.5
mL) at 120 °C for 18 h.
b Yield of isolated product after column chromatography.
c Pd(OAc)2 used: 5 mol%.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

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F. Zhao et al.
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Synthesis
R2
R2
Pd(OAc)2 (10 mol%)
NaNO2 (1.5 equiv)
K2S2O8 (2.0 equiv)
R1
R1
N
N
N
N
NO2
N
DMSO, 120 °C, 18 h
N
1
2
N
N
N
N
N
NO2
N
N
NO2
N
NO2
N
2b (80%)
2c (76%)
2a (86%)
MeO
N
N
N
N
NO2
N
N
NO2
N
N
NO2
N
2d (82%)
2e (92%)
2f (80%)
OMe
MeO
N
N
N
N
NO2
N
NO2
N
N
NO2
N
N
2g (82%)
2h (88%)
2i (86%)
Br
Br
Cl
N
N
N
N
NO2
N
N
NO2
N
NO2
N
N
2l (63%)
2j (72%)
2k (63%)
Br
Br
Cl
N
N
N
N
NO2
N
N
NO2
N
N
NO2
Br
N
2o (78%)
2m (65%)
2n (60%)
F
F
Cl
Cl
MeO
N
N
N
N
NO2
N
N
NO2
N
N
NO2
N
2q (85%)
2p (67%)
2r (73%)
Br
N
N
N
N
N
NO2
N
N
NO2
N
N
NO2
2t (72%)
2u (81%)
2s (71%)
Scheme 1 Palladium-catalyzed nitration of 1,4-disubstituted 1,2,3-triazoles. Reaction conditions: compound 1 (0.2 mmol), Pd(OAc)2 (0.02 mmol),
NaNO2 (0.3 mmol), K2S2O8(0.4 mmol) in DMSO (1.5 mL) at 120 °C for 18 h. Yield of isolated product after column chromatography.
In summary, we have described the palladium-cata-
lyzed nitration of arenes through 1,2,3-triazole-directed C–
H activation. The reaction allowed the nitration of a series
of 1,4-disubstituted 1,2,3-triazoles with either electron-
donating or electron-withdrawing groups directly and effi-
ciently. The present protocol showed high regio- and che-
moselectivity with good functional group tolerance, which
may provide an appealing approach for the synthesis of
valuable 1,2,3-triazoles derivatives with nitro group.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

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F. Zhao et al.
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Synthesis
1H NMR (400 MHz, CDCl3): δ = 8.18 (d, J = 7.8 Hz, 1 H), 8.02 (s, 1 H),
7.87 (d, J = 8.1 Hz, 1 H), 7.72 (t, J = 7.6 Hz, 1 H), 7.54 (t, J = 7.7 Hz, 1 H),
7.47–7.35 (m, 4 H), 2.28 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 148.2, 141.7, 136.0, 133.7, 132.6,
131.5, 131.1, 130.1, 129.0, 126.9, 125.9, 124.6, 124.4, 124.1, 17.8.
N
PdIIL2
NO2
N
N
N
N
N
2c
1c
L = OAc– or NO2
–
HRMS (ESI): m/z [M + H+] calcd for C15H13N4O2: 281.1033; found:
281.1035.
4-(2-Nitrophenyl)-1-phenyl-1H-1,2,3-triazole (2c)16f
Yellow solid; yield: 40 mg (76%); mp 82–83 °C.
N
N
N
PdII
L
N
IV
Pd
N
N
IR (KBr): 3435, 2961, 2826, 2359, 2068, 1604, 1462, 1381, 1262, 1097,
L
1036, 807, 674, 613, 552, 462 cm–1
.
A
O2N
NO2
1H NMR (400 MHz, CDCl3): δ = 8.25 (s, 1 H), 8.13 (d, J = 7.7 Hz, 1 H),
7.87 (d, J = 8.0 Hz, 1 H), 7.79 (d, J = 7.7 Hz, 2 H), 7.71 (t, J = 7.6 Hz, 1 H),
7.55 (q, J = 7.4 Hz, 3 H), 7.48 (t, J = 7.4 Hz, 1 H).
B
[O]
N2O4
NO2
NaNO2
HRMS (ESI): m/z [M + H+] calcd for C14H11N4O2: 267.0877; found:
Scheme 2 Proposed mechanism
267.0879.
1-(4-Methoxyphenyl)-4-(2-nitrophenyl)-1H-1,2,3-triazole (2d)
Yellow solid; yield: 49 mg (82%); mp 123–125 °C.
1H and 13C NMR spectra were recorded using Bruker AM-400 and
Bruker AM-300 spectrometers in CDCl3 with TMS as an internal stan-
dard. Mass spectra were obtained on a VG Auto Spec 3000 or a Fin-
nigan MAT 90 instrument. IR spectra were obtained with KBr plates
using a PerkinElmer Spectrum 1600 Series spectrometer. Melting
points were obtained using a Büchi melting point apparatus and are
uncorrected. Commercially obtained reagents were used without fur-
ther purification. All reactions were monitored by TLC with Huang-
haiGF 254 silica gel coated plates. Column chromatography was car-
ried out using 300–400 mesh silica gel at medium pressure.
IR (KBr): 3441, 3021, 1599, 1518, 1358, 1303, 1171, 1097, 1036, 806,
749, 706 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.27–8.02 (m, 2 H), 7.85 (d, J = 8.1 Hz, 1
H), 7.69 (dd, J = 12.3, 8.2 Hz, 3 H), 7.53 (t, J = 7.7 Hz, 1 H), 7.05 (d,
J = 8.5 Hz, 2 H), 3.88 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 159.9, 148.1, 142.4, 132.5, 131.0,
130.0, 129.0, 124.4, 124.0, 122.3, 121.1, 114.7, 55.6.
HRMS (ESI): m/z [M + H+] calcd for C15H13N4O3: 297.0982; found:
297.0985
Palladium-Catalyzed C–H Nitration of 1,4-Disubstituted 1,2,3-Tri-
azoles; Typical Procedure
4-(4-Methyl-2-nitrophenyl)-1-(p-tolyl)-1H-1,2,3-triazole (2e)
Light yellow solid; yield: 54 mg (92%); mp 138–140 °C.
1,4-Disubstituted 1,2,3-triazole 1 (0.2 mmol), Pd(OAc)2 (4.5 mg, 0.02
mmol), NaNO2 (21 mg, 0.3 mmol), K2S2O8 (108 mg, 0.4 mmol), and
DMSO (1.5 mL) were sequentially added to a 10 mL tube. Then the
tube was sealed and stirred at 120 °C for18 h. Upon completion, H2O
(15 mL) was added to the mixture and extracted with EtOAc (3 × 15
mL). The combined organic layers were washed with brine (3 × 5 mL),
dried (Na2SO4), and concentrated under reduced pressure to afford
the crude product. Purification by column chromatography on silica
gel afforded the desired product 2.
IR (KBr): 3137, 2918, 1617, 1523, 1361, 1232, 1109, 1034, 918, 808,
758 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.17 (s, 1 H), 8.00 (d, J = 8.0 Hz, 1 H),
7.65 (d, J = 8.6 Hz, 3 H), 7.50 (d, J = 8.0 Hz, 1 H), 7.34 (d, J = 7.9 Hz, 2
H), 2.46 (d, J = 18.3 Hz, 6 H).
13C NMR (100 MHz, CDCl3): δ = 148.0, 142.5, 139.8, 139.1, 134.4,
133.3, 130.9, 130.2, 124.3, 121.6, 120.8, 120.5, 21.1, 20.9.
HRMS (ESI): m/z [M + H+] calcd for C16H15N4O2: 295.1190; found:
295.1193.
4-(2-Nitrophenyl)-1-(p-tolyl)-1H-1,2,3-triazole (2a)
White solid; yield: 48 mg (86%); mp 128–130 °C.
IR (KBr): 3427, 2961, 1527, 1383, 1263, 1103, 1038, 753 cm–1
1H NMR (400 MHz, CDCl3): δ = 8.20 (s, 1 H), 8.12 (d, J = 7.8 Hz, 1 H),
7.85 (d, J = 8.1 Hz, 1 H), 7.73–7.62 (m, 3 H), 7.53 (t, J = 7.8 Hz, 1 H),
7.34 (d, J = 7.9 Hz, 2 H), 2.44 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 148.2, 142.4, 139.2, 134.3, 132.5,
131.1, 130.2, 129.0, 124.4, 124.0, 121.0, 120.5, 21.1.
HRMS (ESI): m/z [M + H+] calcd for C15H13N4O2: 281.1033; found:
281.1036.
4-(4-Methyl-2-nitrophenyl)-1-(o-tolyl)-1H-1,2,3-triazole (2f)
White solid; yield: 47 mg (80%); mp 105–107 °C.
.
IR (KBr): 3427, 3147, 2961, 2923, 1610, 1523, 1380, 1262, 1099, 1034,
807, 708, 672 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.05 (d, J = 8.0 Hz, 1 H), 7.98 (s, 1 H),
7.67 (s, 1 H), 7.52 (d, J = 7.8 Hz, 1 H), 7.49 – 7.30 (m, 4 H), 2.49 (s, 3 H),
2.27 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 148.0, 141.8, 139.8, 138.1, 136.1,
133.7, 133.4, 131.5, 130.9, 130.0, 126.8, 126.0, 124.4, 121.6, 20.9, 17.8.
HRMS (ESI): m/z [M + H+] calcd for C16H15N4O2: 295.1190; found:
295.1195.
4-(2-Nitrophenyl)-1-(o-tolyl)-1H-1,2,3-triazole (2b)
Light yellow solid; yield: 45 mg (80%); mp 60–62 °C.
IR (KBr): 3440, 3147, 3080, 2961, 1923, 2860, 1616, 1527, 1459, 1303,
4-(4-Methyl-2-nitrophenyl)-1-phenyl-1H-1,2,3-triazole (2g)
1261, 1099, 1035, 803, 765, 708 cm–1
.
Yellow solid; yield: 46 mg (82%); mp 138–140 °C.
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IR (KBr): 3446, 2963, 1615, 1517, 1384, 1346, 1262, 1095, 1030, 763
cm–1
HRMS (ESI): m/z [M + H+] calcd for C15H12ClN4O2: 315.0643; found:
315.0645.
.
1H NMR (400 MHz, CDCl3): δ = 8.24 (s, 1 H), 8.02 (d, J = 8.0 Hz, 1 H),
7.69 (s, 2 H), 7.68–7.30 (m, 5 H), 2.50 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 148.1, 141.9, 139.9, 134.5, 133.4,
1-(2-Bromophenyl)-4-(2-nitrophenyl)-1H-1,2,3-triazole (2l)
Yellow solid; yield: 43 mg (63%); mp 88–90 °C.
131.0, 130.8, 128.7, 127.7, 124.8, 124.4, 121.5, 20.9.
HRMS (ESI): m/z [M + H+] calcd for C15H13N4O2: 281.1033; found:
IR (KBr): 3435, 2926, 2827, 2359, 2068, 1604, 1462, 1382, 1261, 1098,
806, 673, 557, 462 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.23 (s, 1 H), 8.16 (d, J = 7.8 Hz, 1 H),
7.88 (d, J = 8.1 Hz, 1 H), 7.79 (d, J = 8.0 Hz, 1 H), 7.73 (t, J = 7.6 Hz, 1 H),
7.63 (d, J = 7.9 Hz, 1 H), 7.54 (dd, J = 16.6, 8.2 Hz, 2 H), 7.44 (t, J = 7.7
Hz, 1 H).
281.1030.
1-(4-Methoxyphenyl)-4-(4-methyl-2-nitrophenyl)-1H-1,2,3-tri-
azole (2h)
Light yellow solid; yield: 55 mg (88%); mp 165–167 °C.
13C NMR (100 MHz, CDCl3): δ = 148.2, 141.7, 136.1, 133.9, 132.6,
131.4, 131.2, 129.1, 128.5, 128.1, 125.1, 124.2, 124.1, 118.5.
HRMS (ESI): m/z [M + H+] calcd for C14H10BrN4O2: 344.9982; found:
344.9986.
IR (KBr): 3438, 2961, 1606, 1521, 1374, 1255, 1032, 700 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.12 (s, 1 H), 8.00 (d, J = 8.0 Hz, 1 H),
7.67 (d, J = 8.9 Hz, 3 H), 7.50 (d, J = 8.0 Hz, 1 H), 7.04 (d, J = 8.8 Hz, 2
H), 3.88 (s, 3 H), 2.48 (s, 3 H).
1-(3-Bromophenyl)-4-(2-nitrophenyl)-1H-1,2,3-triazole (2m)
White solid; yield: 45 mg (65%); mp 120–122 °C.
13C NMR (100 MHz, CDCl3): δ = 159.9, 148.0, 142.5, 139.8, 133.3,
130.9, 130.1, 124.3, 122.3, 121.6, 121.0, 114.7, 55.6, 20.9.
HRMS (ESI): m/z [M + H+] calcd for C16H15N4O3: 311.1139; found:
311.1137.
IR (KBr): 3427, 3141, 1590, 1526, 1463, 1373, 1232, 1097, 787, 746
cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.25 (s, 1 H), 8.10 (d, J = 7.8 Hz, 1 H),
7.99 (s, 1 H), 7.88 (d, J = 8.1 Hz, 1 H), 7.72 (dd, J = 15.5, 7.9 Hz, 2 H),
7.66–7.48 (m, 2 H), 7.43 (t, J = 8.0 Hz, 1 H).
13C NMR (100 MHz, CDCl3): δ = 148.1, 142.9, 137.5, 132.6, 132.0,
131.0, 131.1, 129.3, 124.2, 124.0, 123.7, 123.3, 120.9, 119.1.
4-(4-Methoxy-2-nitrophenyl)-1-(p-tolyl)-1H-1,2,3-triazole (2i)
Yellow solid; yield: 53 mg (86%); mp 164–166 °C.
IR (KBr): 3426, 2961, 1621, 1421, 1274, 1155, 1076, 932, 723, 656,
601 cm–1
.
HRMS (ESI): m/z [M + H+] calcd for C14H10BrN4O2: 344.9982; found:
344.9985.
1H NMR (400 MHz, CDCl3): δ = 8.14 (s, 1 H), 8.01 (d, J = 8.7 Hz, 1 H),
7.65 (d, J = 8.1 Hz, 2 H), 7.38–7.32 (m, 3 H), 7.23 (d, J = 8.7 Hz, 1 H),
3.92 (s, 3 H), 2.44 (s, 3 H).
4-(5-Bromo-2-nitrophenyl)-1-(2-bromophenyl)-1H-1,2,3-triazole
(2n)
13C NMR (100 MHz, CDCl3): δ = 159.7, 148.8, 139.1, 134.5, 132.3,
130.2, 120.5, 118.9, 116.8, 109.1, 55.9, 21.1.
HRMS (ESI): m/z [M + H+] calcd for C16H15N4O3: 311.1139; found:
311.1141.
Light yellow solid; yield: 51 mg (60%); mp 132–134 °C.
IR (KBr): 3436, 2926, 2830, 2359, 2068, 1837, 1605, 1513, 1461, 1382,
1262, 1095, 1031, 811, 754, 671, 558, 463 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.37 (s, 1 H), 8.27 (s, 1 H), 7.82–7.77
(m, 2 H), 7.67 (d, J = 8.7 Hz, 1 H), 7.62 (s, 1 H), 7.54 (t, J = 7.6 Hz, 1 H),
7.45 (t, J = 7.5 Hz, 1 H).
13C NMR (100 MHz, CDCl3): δ = 146.7, 140.5, 136.0, 134.1, 134.0,
132.1, 131.5, 128.6, 128.1, 127.4, 126.1, 125.7, 125.7, 118.6.
1-(2-Bromophenyl)-4-(4-methyl-2-nitrophenyl)-1H-1,2,3-triazole
(2j)
Light yellow solid; yield: 52 mg (72%); mp 138–139 °C.
IR (KBr): 3434, 2962, 1609, 1517, 1345, 1262, 1220, 1098, 1029, 806,
754 cm–1
.
HRMS (ESI): m/z [M + H+] calcd for C14H9Br2N4O2: 422.9087; found:
422.9089.
1H NMR (400 MHz, CDCl3): δ = 8.20 (s, 1 H), 8.03 (d, J = 7.9 Hz, 1 H),
7.79 (d, J = 8.0 Hz, 1 H), 7.69 (s, 1 H), 7.63 (d, J = 7.8 Hz, 1 H), 7.52 (d,
J = 5.9 Hz, 2 H), 7.43 (t, J = 7.7 Hz, 1 H), 2.50 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 148.0, 141.8, 139.9, 136.2, 133.9,
133.4, 131.3, 131.1, 128.5, 128.1, 124.9, 124.4, 121.5, 118.6, 21.0.
1-(4-Chlorophenyl)-4-(2-nitrophenyl)-1H-1,2,3-triazole (2o)16f
Light yellow solid; yield: 46 mg (78%); mp 107–109 °C.
HRMS (ESI): m/z [M + H+] calcd for C15H12BrN4O2: 359.0138; found:
359.0140.
IR (KBr): 3435, 2925, 2841, 2359, 1604, 1514, 1463, 1383, 1347, 1222,
1103, 1070, 1027, 856, 749, 702, 660, 516, 458 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.27 (s, 1 H), 8.15 (d, J = 7.7 Hz, 1 H),
7.88 (d, J = 8.0 Hz, 1 H), 7.77–7.66 (m, 2 H), 7.61 (d, J = 3.4 Hz, 1 H),
7.59–7.34 (m, 3 H).
1-(2-Chlorophenyl)-4-(4-methyl-2-nitrophenyl)-1H-1,2,3-triazole
(2k)
Light yellow solid; yield: 40 mg (63%); mp 143–145 °C.
HRMS (ESI): m/z [M + H+] calcd for C14H110ClN4O2: 301.0487; found:
301.0484.
IR (KBr): 3417, 3149, 2965, 1380, 1261, 1095, 1036, 868, 806, 682 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.22 (s, 1 H), 8.00 (d, J = 8.0 Hz, 1 H),
7.78 (d, J = 8.0 Hz, 2 H), 7.67 (s, 1 H), 7.58–7.49 (m, 3 H), 2.49 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 148.0, 142.7, 139.9, 136.7, 133.3,
1-(2-Chlorophenyl)-4-(2-nitrophenyl)-1H-1,2,3-triazole (2p)
Light yellow solid; yield: 40 mg (67%); mp 115–117 °C.
IR (KBr): 3435, 2926, 2724, 2359, 2068, 1837, 1603, 1384, 1263, 1097,
130.9, 130.7, 129.7, 129.4, 128.9, 124.4, 121.5, 120.8, 120.6, 20.9.
1036, 810, 674, 558, 468 cm–1
.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

F
F. Zhao et al.
Paper
Synthesis
1H NMR (400 MHz, CDCl3): δ = 8.23 (s, 1 H), 8.10 (d, J = 7.8 Hz, 1 H),
7.87 (d, J = 8.1 Hz, 1 H), 7.72 (dd, J = 17.3, 8.1 Hz, 3 H), 7.55 (t, J = 9.7
Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 148.1, 142.8, 135.1, 134.8, 132.6,
131.1, 129.9, 129.3, 128.9, 126.2, 124.1, 124.0, 121.8, 120.9.
4-(2-Methyl-6-nitrophenyl)-1-(p-tolyl)-1H-1,2,3-triazole (2u)
White solid; yield: 48 mg (81%); mp 104–106 °C.
IR (KBr): 3417, 3127, 2941, 2925, 1609, 1522, 1381, 1263, 1100, 1031,
802, 706, 662 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 7.94 (s, 1 H), 7.62 (dd, J = 18.1, 8.3 Hz, 3
H), 7.47 (d, J = 7.5 Hz, 1 H), 7.38 (t, J = 7.9 Hz, 1 H), 7.26 (d, J = 8.2 Hz, 2
H), 2.36 (s, 3 H), 2.27 (s, 3 H).
HRMS (ESI): m/z [M + H+] calcd for C14H10ClN4O2: 301.0487; found:
301.0489.
13C NMR (100 MHz, CDCl3): δ = 150.8, 141.5, 140.8, 139.0, 134.4,
134.1, 130.2, 129.2, 123.9, 121.3, 121.1, 120.4, 21.0, 20.7.
HRMS (ESI): m/z [M + H+] calcd for C16H15N4O2: 295.1190; found:
4-(2-Fluoro-6-nitrophenyl)-1-(p-tolyl)-1H-1,2,3-triazole (2q)
Light yellow solid; yield: 50 mg (85%); mp 158–160 °C.
IR (KBr): 3431, 3260, 2860, 1632, 1572, 1357, 1301, 1272, 1196, 1032,
295.1195.
728, 706 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.26 (s, 1 H), 7.68 (d, J = 8.1 Hz, 3 H),
7.53 (dd, J = 13.6, 8.0 Hz, 1 H), 7.44 (t, J = 8.8 Hz, 1 H), 7.34 (t, J = 8.8
Hz, 2 H), 2.44 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 139.2, 134.3, 130.3, 130.1, 130.0,
122.1, 122.0, 120.5, 120.1, 120.0, 119.6, 119.4, 21.1.
Acknowledgment
The authors would like to thank the National Natural Science Founda-
tion of China (No. 21262020 and 51464021) for the financial support.
HRMS (ESI): m/z [M + H+] calcd for C15H12FN4O2: 299.0939; found:
299.0936.
Supporting Information
Supporting information for this article is available online at
4-(2-Fluoro-6-nitrophenyl)-1-(4-methoxyphenyl)-1H-1,2,3-tri-
azole (2r)
http://dx.doi.org/10.1055/s-0035-1561951.
S
u
p
p
ortiInfogrmoaitn
S
u
p
p
o
nrtogI
f
rmoaitn
Light yellow solid; yield: 46 mg (73%); mp 155–157 °C.
IR (KBr): 3421, 3160, 2962, 1603, 1527, 1375, 1304, 1172, 1096, 1033,
References
738, 703 cm–1
.
1H NMR (400 MHz, CDCl3): δ = 8.21 (s, 1 H), 7.69 (dd, J = 14.5, 8.5 Hz, 3
H), 7.53 (dd, J = 13.8, 7.6 Hz, 1 H), 7.44 (t, J = 8.8 Hz, 1 H), 7.06 (d,
J = 8.4 Hz, 2 H), 3.89 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 160.0, 149.9, 136.3, 130.1, 130.0,
122.3, 122.2, 120.1, 120.0, 119.6, 119.4, 114.8, 55.6.
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HRMS (ESI): m/z [M + H+] calcd for C15H12FN4O3: 315.0888; found:
315.0886.
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1-(2-Chlorophenyl)-4-(2-methyl-6-nitrophenyl)-1H-1,2,3-triazole
(2s)
Light yellow solid; yield: 45 mg (71%); mp 140–142 °C.
IR (KBr): 3427, 3150, 2975, 1388, 1251, 1085, 1026, 865, 801, 662 cm–1
1H NMR (400 MHz, CDCl3): δ = 8.00 (s, 1 H), 7.80–7.61 (m, 2 H), 7.56–
7.48 (m, 2 H), 7.45–7.38 (m, 3 H), 2.29 (s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 150.8, 140.9, 140.8, 134.6, 134.2,
130.9, 130.7, 129.3, 128.6, 128.0, 127.8, 125.2, 123.8, 121.5, 20.7.
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315.0645.
.
1-(3-Bromophenyl)-4-(2-methyl-6-nitrophenyl)-1H-1,2,3-triazole
(2t)
Light yellow solid; yield: 52 mg (72%); mp 160–162 °C.
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cm–1
.
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1H NMR (400 MHz, CDCl3): δ = 7.99 (s, 1 H), 7.93 (t, J = 1.8 Hz, 1 H),
7.68 (dd, J = 11.6, 4.7 Hz, 2 H), 7.50 (dd, J = 16.0, 7.8 Hz, 2 H), 7.38 (dt,
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G

G
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2016, 48, A–G