Highly Efficient Cycloaddition Reaction of 1,3-Diynes with Sodium Azide: A New Way to 5-Substituted-4-acetylene-1H-1,2,3-triazoles

Article abstract of DOI:10.1002/jhet.1950

A cycloaddition reaction of a range of 1,3-diynes with sodium azide has been realized, which provided 5-substituted-4-acetylene-1H-1,2,3-triazoles in 75–99% yields. The chemical structures of the new compounds 3 are established by IR, NMR, Mass, and HRMS.

Full text of DOI:10.1002/jhet.1950

Month 2016
Highly Efficient Cycloaddition Reaction of 1,3-Diynes with Sodium
Azide: A New Way to 5-Substituted-4-acetylene-1H-1,2,3-triazoles
*
Jia-Liang Tang, Ling Ming, and Xiao-Ming Zhao
Department of Chemistry, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University,
Shanghai 200092, People’s Republic of China
*
E-mail: xmzhao08@mail.tongji.edu.cn
Additional Supporting Information may be found in the online version of this article.
Received October 21, 2012
DOI 10.1002/jhet.1950
Published online 00 Month 2016 in Wiley Online Library (wileyonlinelibrary.com).
A cycloaddition reaction of a range of 1,3-diynes with sodium azide has been realized, which provided 5-
substituted-4-acetylene-1H-1,2,3-triazoles in 75–99% yields. The chemical structures of the new compounds
3 are established by IR, NMR, Mass, and HRMS.
J. Heterocyclic Chem., 00, 00 (2016).
INTRODUCTION
was obtained when the reaction temperature was elevated to
50ꢀC (Table 1, entry 2). 13C NMR analysis of 3a revealed
that there are peaks at 146.3, 131.7, 95.8, and 78.7 ppm
in 13C NMR spectra, which are distributed to 1H-1,2,3-
triazole and acetylene, respectively. Consequently, compound
3a [8] was recognized as 5-phenyl-4-(phenylethynyl)-1H-
1,2,3-triazole by means of IR, NMR, MS, and HRMS. It is
noteworthy that 5-substituted 4-acetylene-1H-1,2,3-triazole
containing acetylene function can undergo further transforma-
tion. In all cases, the di-1H-1,2,3-triazole derivatives were suc-
cessfully suppressed and no 5,50-diphenyl-1H,10H-4,40-bi
(1,2,3-triazole) was observed. Encouraged by these outcomes,
a diversity of solvents such as THF, dioxane, Et3N, toluene,
CH3CN, and DMSO were screened, and the preliminary
results were summarized in Table 1. DMSO gave rise to
somewhat improvement in yield of 3a, whereas the remaining
solvents are ineffective (Table 1, entry 3–8). Variation of the
ratio of 1a/2 has a considerable influence on efficiency of this
reaction (Table 1, entries 8–11). Interestingly, 1a/2 in a ratio of
1/6 resulted in the highest yield (Table 1, entry 10). This reac-
tion was also performed at a range of 25 to 140ꢀC, the reaction
at 110ꢀC led to the best result (Table 1, entries 10, 12–15).
Therefore, the reaction conditions presented in entry 14 was
selected as a standard for further study.
Having established the optimized reaction conditions, we
further explored the scope of this reaction. As shown in
Table 2, 1,3-diynes 1a–h with either electron-donating groups
(e.g., 3-Me, 4-Me, 4-MeO, 4-pentyl, and 4-Ph) or electron-
withdrawing groups (e.g., 4-Br and 4-F) on the phenyl ring
produced the corresponding 5-substituted 4-acetylene-1H-
1,2,3-triazole 3a–h in good to excellent yields (75–99%). It is
noted that no di-1H-1,2,3-triazole derivative was observed in
all cases. The desired products N-unsubstituted 1,2,3-triazoles
may be applied in transition metal-mediated reactions.
Azide-alkyne Huisgen 1,3-dipolar cycloaddition, a rep-
resentative reaction of click chemistry [1], has received
great attention because of a wide range of applications in
the areas of drug discovery and material science in the past
decade [2]. In general, a combination of cupric sulfate
(CuSO4) and sodium ascorbate is employed as a precata-
lyst in the course of reactions, which generates cuprous
(Cu(I)) species as a catalyst [3]. Moreover, a combination
of cuprous and ligand can be directly used as the catalyst
in this type of reactions [4]. The azide-alkyne Huisgen
cycloadditon between an azide and a terminal or internal
alkyne were investigated [5]. Notably, copper-catalyzed
cycloaddition of a range of 1,3-diynes with sodium azide
(NaN3) is less investigated. To the best of our knowledge,
cycloaddition of 1,3-diynes with sodium azide (NaN3) is
not explored until now [6]. As a result, it is highly desirable
to develop an efficient methodology for the synthesis of
1H-1,2,3-triazoles. A number of methods were disclosed
to synthesize N-substituted 1,2,3-triazoles, few methods
for the preparation of N-unsubstituted 1,2,3-triazoles
were reported [7]. In this paper, we report a convenient
1,3-dipolar cycloaddition of a range of 1,3-diynes with
sodium azide (NaN3) to achieve 5-substituted-4-acetylene-
1H-1,2,3-triazoles.
RESULTS AND DISCUSSION
In our initial study, a model reaction between 1,4-
diphenylbuta-1,3-diyne (1a) and sodium azide (NaN3, 2)
in the absence of copper catalyst [3,4] was investigated.
This reaction (1a/2, 1/4) in DMF at room temperature was
carried out and, after 12 h, no desired product was observed
(Table 1, entry 1). To our delight, 20% yield of product 3a
© 2016 Wiley Periodicals, Inc.

J.-L. Tang, L. Ming, and X.-M. Zhao
Vol 000
Therefore, this reaction can be applied in a wide range of
organic synthesis [9]. 1-Methoxy-4-((4-pentylphenyl)buta-
1,3-diynyl)benzene 1i, a representative unsymmetrical 1,3-
diyne, was also explored under the identical conditions,
and it gave a mixture of two final compounds in a ratio
of 1:1 determined by and GC–MS, which are inseparable
by meansof silica gel column chromatography. On the
basis of analysis of GC–MS, 1H, and 13C NMR, we
deduced that two final products are 5-(4-methoxyphenyl)-
4-((4-pentylphenyl)ethynyl)-1H-1,2,3-triazole 3ia and 4-
((4-methoxyphenyl)ethynyl)-5-(4-pentylphenyl)-1H-1,2,
3-triazole 3ib, respectively.
Table 1
Optimizing reaction condition for the cycloaddition reaction of 1,4-
diphenylbuta-1,3-diyne 1a with NaN3 2.a
Using 1,4-diphenylbuta-1,3-diyne 1a as a substrate, the
synthesis of pyrazole 5a was investigated and a representa-
tive example was shown in Scheme 1. The cyclization reac-
tion of 1, 4-diphenylbuta-1,3-diyne 1a with hydrazine
hydrate 4 (85%) gave 5a [10] in 96% yield. Both 13C
1
Entry
Solvent
1a/2
T (ꢀC)
Yield b (%)
NMR and H NMR analysis of 5a indicated that there
appeared peaks at 148.9, 147.5, 101.9, and 33.0 ppm in 13C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
DMF
DMF
THF
Dioxane
Et3N
Toluene
CH3CN
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
1/4
1/4
1/4
1/4
1/4
1/4
1/4
1/4
1/2
1/6
1/8
1/6
1/6
1/6
1/6
rt
50
50
50
50
50
50
50
50
50
50
rt
—
20
—
—
—
—
—
27
24
33
33
10
95
99
99
1
NMR spectra and a single peak at 10.31ppm in H NMR
spectra, which are distributed to 1H-pyrazole and methylene
(CH2), respectively. As a result, the chemical structure of
5-benzyl-3-phenyl-1H-pyrazole 5a was established by 1H or
13C NMR. It is obvious that metal-free cyclization reaction
of 1,3-diynes with hydrazine hydrate 4 (85%) is economical
and green protocol compared with traditional methods for
the preparation of 5-benzyl-3-phenyl-1H-pyrazole that usu-
ally require the use of gold (Au) species as a catalyst [10b].
A possible mechanism for this reaction was proposed
as shown in Scheme 2. A hydroamination reaction of 1,3-
diyne 1a with hydrazine hydrate 4 (85%) at 80ꢀC undergoes
to provide a hydrazine-substituted enyne A [10e]. The isomer-
ization of A takes place to give a buta-2,3-dienylidene-hydra-
zine B [11], which is then transformed into pyrazole 4 by an
intramolecular hydroamination.
80
110
140
aReaction conditions: 1, 4-diphenylbuta-1,3-diyne 1a (0.2 mmol), NaN3 2
(0.4–1.6 mmol) in a range of solvents (2.0 mL) at appropriate temperature
under air atmosphere overnight.
bIsolated yield.
Table 2
The cycloaddition of various 1, 3-diynes 1 with NaN3 2.a
Scheme 1. Metal-free cyclization reaction of 1, 4-diphenylbuta-1,3-diyne
1a with hydrazine hydrate 4.
Scheme 2. Possible mechanism for the cyclization reaction of 1, 4-
diphenylbuta-1,3-diyne 1a with hydrazine hydrate 4.
Entry
R
Product 3
Yield b (%)
1
2
3
4
5
6
7
8
C6H5
3a
3b
3c
3d
3e
3f
99
90
99
99
99
95
75
87
3-MeC6H4
4-MeC6H4
4-MeOC6H4
4-pentylC6H4
4-BrC6H4
4-FC6H4
4-PhC6H4
3g
3h
aReaction conditions: 1,3-diynes 1a–h (0.2 mmol), NaN3 2 (1.2 mmol),
and 2.0 mL of DMSO at 110ꢀC for 18 h under air atmosphere.
bIsolated yield.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2016
Highly Efficient Cycloaddition Reaction of 1,3-Diynes with Sodium Azide: A New Way
to 5-Substituted-4-acetylene-1H-1,2,3-triazoles
618, 813, 1031, 1185, 1258, 1521, 1617, 2046, 2226, 2831, 2969,
3122; 1H NMR (400 MHz, CDCl3): d = 3.79 (s, 3H), 3.80 (s, 3H),
6.85 (d, J = 9.2Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 7.45
(d, J = 8.8Hz, 2H), 8.06 (d, J = 8.8 Hz, 2H); 13C NMR (100MHz,
CDCl3): d = 55.2, 55.3, 77.7, 95.6, 114.0, 114.2, 114.2, 121.3,
125.3, 128.1, 133.1, 144.7, 160.1, 160.1; EI-MS m/z 305 [M]+;
HRMS (EI) Anal. Calcd for C18H15N3O2 [M]+ 305.1164, Found
305.1163.
In summary, we have developed a practical approach for
the preparation of 4,5-disubstituted-1H-1,2,3-triazoles via
cycloaddition reaction of a range of 1,3-diynes (1) with so-
dium azide (2), providing 5-substituted-4-acetylene-1H-
1,2,3-triazoles (3) in good to excellent yields.
EXPERIMENTAL
5-(4-pentylphenyl)-4-(2-(4-pentylphenyl)ethynyl)-1H-1,2,3-
triazole (3e). Yield: 99%; IR (KBr): 538, 742, 845, 993, 1015,
1114, 1278, 1447, 1467, 1518, 2219, 2850, 2933, 2956, 3122;
1H NMR (400 MHz, CDCl3): d =0.90 (dd, J = 6.8, 6.0 Hz, 6H),
1.26–1.37 (m, 8H), 1.60–1.64 (m, 4H), 2.59–2.63 (m, 4H), 7.16
(d, J=8.0Hz, 2H), 7.26 (d, J= 8.4 Hz, 2H), 7.46 (d, J=8.0Hz, 2H),
8.05 (d, J = 8.0Hz, 2H); 13C NMR (100MHz, CDCl3): d = 14.0,
14.0, 22.5, 22.5, 30.9, 30.9, 31.4, 31.5, 35.8, 35.9, 78.4, 95.9,
119.3, 125.9, 126.1, 126.7, 128.5, 128.8, 131.6, 144.1, 144.3,
145.4; EI-MS m/z 385 [M]+; HRMS (EI) Anal. Calcd for
C26H31N3 [M]+ 385.2518, Found 385.2522.
Starting materials 1a–1h were prepared according to the litera-
ture procedure [12]. All melting points were uncorrected. The IR
spectra were recorded on KBr pellets on Nicolet AVATAR 360
1
FT-IR spectrophotometer (Markham, Ontario, Canada). H NMR,
13C NMR, and 19F NMR spectra were recorded on a Bruker Model
Avance III 400 MHz spectrometer in CDCl3 or DMSO-d6, using
TMS as the internal standard; and chemical shifts are given in d rela-
tive to the solvent peak. Mass spectra were measured with Agilent
5973N mass spectrometer. TLC was performed on silica gel GF 254.
General procedure for the preparation of 5-substituted-4-
acetylene-1H-1,2,3-triazoles (3) from 1,3-diynes (1) and
sodium azide (2). 1,3-Diynes (0.2 mmol) and NaN3 (1.2 mmol)
were added in DMSO (2 mL), and the reaction mixture was
stirred at 110ꢀC under air atmosphere for 18 h. After
completion of the reaction, monitoring by TLC, the mixture
was quenched with the addition of 20 mL brine, and then
extracted with ether (5 mL, three times), and the combined
organic layer was dried over Na2SO4. The solvent was
evaporated and the crude product was purified by silica gel
column chromatography to give 5-substituted-4-acetylene-1H-
1,2,3-triazole (3) as product.
5-(4-bromophenyl)-4-(2-(4-bromophenyl)ethynyl)-1H-1,2,3-
triazole (3f). Yield: 95%; mp 167–169ꢀC; IR (KBr): 515, 816,
1
1073, 1262, 1383, 1643, 2937; H NMR (400 MHz, DMSO-d6):
d = 7.61 (d, J = 8.4Hz, 2H), 7.69 (d, J = 8.8Hz, 2H), 7.78
(d, J = 8.8Hz, 2H), 8.01 (d, J = 8.4 Hz, 2H); 13C NMR (100MHz,
DMSO-d6): d = 80.6, 93.8, 120.4, 122.3, 123.0, 128.0, 128.2,
128.8, 131.6, 132.0, 132.1, 133.3; EI-MS m/z 403 [M+ + 3];
HRMS (EI) Anal. Calcd for C16H9Br2N3 [M]+ 400.9163, Found
400.9162.
5-(4-fluorophenyl)-4-(2-(4-fluorophenyl)ethynyl)-1H-1,2,3-
triazole (3g). Yield: 75%; mp 209–211ꢀC; IR (KBr): 528, 743,
832, 996, 1031, 1159, 1236, 1476, 1502, 1534, 1633, 2844, 2917;
1H NMR (400 MHz, DMSO-d6): d = 7.35 (t, J = 8.8Hz, 2H), 7.43
(t, J = 8.8Hz, 2H), 7.73 (dd, J = 8.8, 8.8Hz, 2H), 8.12 (dd, J = 8.8,
8.4 Hz, 2H); 19F NMR (376 MHz, DMSO-d6): d =ꢁ107.29,
ꢁ104.53; 13C NMR (100MHz, DMSO-d6): d = 79.9, 93.9, 116.0,
116.1, 116.2, 116.3, 117.7, 117.8, 128.4, 128.5, 133.8, 133.9,
161.1, 161.2, 163.6, 163.7; EI-MS m/z 281 [M]+; HRMS (EI)
Anal. Calcd for C16H9N3F2 [M]+ 281.0765, Found 281.0763.
5-(4-phenyl-phenyl)-4-(2-(4-phenyl-phenyl)ethynyl)-1H-1,2,3-
triazole (3h). Yield: 87%; mp 178–180ꢀC; IR (KBr): 502, 551,
695, 740, 765, 797, 839, 996, 1079, 1114, 1258, 1402, 1447, 1486,
1601, 1720, 1915, 2101, 2229, 2853, 2924, 2962, 3033; 1H NMR
(400 MHz, DMSO-d6): d = 7.41–7.45 (m, 2H), 7.52 (t, J = 7.6 Hz,
2H), 7.74–7.83 (m, 8H). 7.92 (d, J = 8.4 Hz, 4H), 8.24
(d, J = 8.4 Hz, 2H); 13C NMR (100 MHz, DMSO-d6): d = 120.3,
126.5, 126.6, 126.7, 126.7, 127.1, 127.2, 127.8, 128.0, 128.7,
129.0, 129.0, 131.8, 132.0, 139.0, 139.3, 140.6, 140.9; EI-MS m/
z 397 [M]+; HRMS (EI) Anal. Calcd for C28H19N3 [M]+
397.1579, Found 397.1578.
All of the products are new and have been characterized by IR,
1H NMR, 13C NMR, 19F NMR, MS, and HRMS.
5-phenyl-4-(2-phenylethynyl)-1H-1,2,3-triazole (3a). Yield:
99%; mp 113–114ꢀC; IR (KBr): 531, 688, 752, 775, 916, 983,
1021, 1236, 1444, 1499, 1604, 1947, 2222, 2847, 2921, 3154;
1H NMR (400 MHz, CDCl3): d = 7.30–7.45 (m, 4H), 7.48
(dd, J = 8.0, 6.8 Hz, 2H), 7.57 (dd, J = 7.6, 6.8 Hz, 2H), 8.15
(d, J = 7.6 Hz, 2H); 13C NMR (100 MHz, CDCl3): d = 78.7,
95.8, 122.0, 126.2, 126.8, 128.4, 128.8, 129.0, 129.1, 129.1,
131.7, 146.3; EI-MS m/z 245 [M]+; HRMS (EI) Anal. Calcd for
C16H11N3 [M]+ 245.0953. Found: 245.0948
5-m-tolyl-4-(2-m-tolylethynyl)-1H-1,2,3-triazole (3b). Yield:
90%; mp 97–98ꢀC; IR (KBr): 519, 621, 685, 781, 989, 1092,
1377, 1483, 1604, 1941, 2229, 2853, 2927, 3023, 3158;
1H NMR (400 MHz, CDCl3): d = 2.33 (s, 3H), 2.39 (s, 3H),
7.15–7.25 (m, 3H), 7.32–7.36 (m, 3H), 7.95 (d, J = 8.0 Hz, 2H),
7.98 (s, 1H); 13C NMR (100 MHz, CDCl3): d = 21.2, 21.4, 78.5,
96.0, 121.9, 123.9, 126.0, 127.5, 128.3, 128.7, 129.9, 129,
132.1, 138.1, 138.4, 145.8; EI-MS m/z 273 [M]+; HRMS (EI)
Anal. Calcd for C18H15N3 [M]+ 273.1266, Found 273.1270.
5-p-tolyl-4-(2-p-tolylethynyl)-1H-1,2,3-triazole (3c). Yield:
99%; mp 133–134ꢀC; IR (KBr): 522, 730, 810, 986, 1015,
1041, 1185, 1239, 1511, 1620, 1649, 1902, 2222, 2853, 2924,
General procedure for the preparation of 5-substituted-4-
acetylene-1H-1,2,3-triazoles (3ia and 3ib) from unsymmetrical
1,3-diynes (1i) and sodium azide (2). 1-Methoxy-4-((4-
pentylphenyl)buta-1,3-diynyl)benzene (0.2 mmol) and NaN3
(1.2 mmol) were added in DMSO (2 mL), and the reaction mixture
was stirred at 110ꢀC under air atmosphere for 72 h. After
completion of the reaction, monitoring by TLC, the mixture was
quenched with the addition of 20 mL brine, and then extracted with
ether (5 mL, three times) and the combined organic layer was dried
over Na2SO4. The solvent was evaporated, and the crude
product was purified by silica gel column chromatography to give
a mixture of 5-(4-methoxyphenyl)-4-((4-pentylphenyl)ethynyl)-
1H-1,2,3-triazole (3ia) and 4-((4-methoxyphenyl)ethynyl)-5-(4-
1
3039, 3186; H NMR (400 MHz, CDCl3): d = 2.37 (s, 6H), 7.15
(d, J = 8.0 Hz, 2H), 7.25 (d, J = 8.0 Hz, 2H), 7.43 (d, J = 8.0 Hz,
2H), 8.02 (d, J = 8.0 Hz, 2H); 13C NMR (100 MHz, CDCl3):
d = 21.3, 21.5, 78.3, 95.9, 119.1, 125.9, 126.7, 129.2, 129.5,
131.6, 139.1, 139.2, 145.8; EI-MS m/z 273 [M]+; HRMS (EI)
Anal. Calcd for C18H15N3 [M ]+ 273.1266, Found 273.1264.
5-(4-methoxyphenyl)-4-(2-(4-methoxyphenyl)ethynyl)-1H-
1,2,3-triazole (3d). Yield: 99%; mp 81–83ꢀC; IR (KBr): 531,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

J.-L. Tang, L. Ming, and X.-M. Zhao
Vol 000
pentylphenyl)-1H-1,2,3-triazole (3ib) in a ratio of 1:1 determined by
GC-MS. Both 3ia and 3ib are inseparable.
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5-(4-methoxyphenyl)-4-((4-pentylphenyl)ethynyl)-1H-1,2,3-
triazole (3ia) and 4-((4-methoxyphenyl)ethynyl)-5-(4-pentylphenyl)-
1H-1,2,3-triazole (3ib).
Overall yield of (3ia +3ib): 89%; 1H
NMR of (3ia +3ib) (400 MHz, CDCl3): d =0.90 (t, J=6.8Hz, 3H),
1.24–1.38 (m, 4H), 1.60–1.65 (m, 2H), 2.59–2.64 (m, 2H), 3.82
(s, 3H), 6.88 (d, J=8.4Hz, 1H), 6.98 (d, J= 8.8 Hz, 1H), 7.17
(d, J= 8.0 Hz, 1H), 7.27 (d, J= 8.4 Hz, 1H), 7.46–7.51 (m, 2H),
8.07 (t, J= 9.2 Hz, 2H); 13C NMR of (3ia +3ib) (100 MHz,
CDCl3): d = 14.0, 14.0, 22.5, 22.5, 30.9, 30.9, 31.4, 31.5, 35.8,
35.9, 55.3, 55.3, 77.2, 77.7, 78.4, 95.8, 114.1, 114.2, 114.3, 119.3,
121.4, 126.2, 126.6, 128.2, 128.5, 128.8, 131.6, 133.2, 144.1,
144.3, 145.4, 160.2, 160.2, 171.6.
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5-benzyl-3-phenyl-1H-pyrazole (5a).
1, 4-Diphenylbuta-
1,3-diyne 1a (40.4 mg, 0.2 mmol) and hydrazine hydrate (85%,
2 mL) were placed in a reaction tube, and the reaction mixture
was stirred at 80ꢀC under air atmosphere for 2 h. After
completion of the reaction, monitoring by TLC, the mixture was
quenched with the addition of 20 mL brine, and then extracted
with ether (5 mL, three times), and the combined organic layer
was dried over Na2SO4. The solvent was evaporated and the
crude product was purified by silica gel column chromatography
to give 5-benzyl-3-phenyl-1H-pyrazole 5a (44.9 mg, 96% yield).
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2012, 134, 194; (e) Liu, W.; Zhang, D. Z.; Zheng, S. C.; Yue, Y. S.;
Liu, D. G.; Zhao, X. M. Eur J Org Chem 2011, 2011, 6288.
[10] Compound 5a has been prepared from 1,3-diynes by a known
method, for details, see: a) Lavallo, V.; Frey, G. D.; Donnadieu, B.;
Soleihavoup, M.; Bertrand, G. Angew Chem Int Ed 2008, 47, 5224; b)
Kinjo, R.; Donnadieu, B.; Bertrand, G. Angew Chem Int Ed 2011, 50,
5560; c) Kramer, S.; Madsen, J. L. H.; Rottländer, M.; Skrydstrup, T.
Org Lett 2010, 12, 2758; d) Nun, P.; Dupuy, S.; Gaillard, S.; Poater, A.;
Cavallo, L.; Nolan, S. P. Catal Sci Technol 2011, 1, 58; Addition reactions
of amine with 1,3-diynes afforded the corresponding amino enynes, for
detail, see: e) Zheng, Q. W.; Hua, R. M. Tetrahedron Lett 2010, 51, 4512.
[11] (a) N-(but-1-en-3-ynyl)hydroxylamine, an analogue of hydrazine-
substituted enyne A, underwent an isomerization to form buta-2,3-dienal
oxime, for details, see: Wang, L. G.; Yu, X. Q.; Feng, X. J.; Bao, M. Org Lett
2012, 14, 2418; (b) Martn, R.; Rivero, M. R.; Buchwald, S. L. Angew Chem
Int Ed 2006, 46, 7079.
1
[10] mp 83–84ꢀC; H NMR (400 MHz, CDCl3): d 3.88 (s, 2H),
6.26 (s, 1H), 7.14–7.28 (m, 8H), 7.63 (d, J = 7.2 Hz, 2H), 10.3
(brs, 1H); 13C NMR (100 MHz, CDCl3): d 33.0, 101.9, 125.6,
126.4, 127.8, 128.5, 128.6, 128.6, 131.9, 138.6, 147.5, 148.9.
Acknowledgments. We gratefully acknowledge the NSFC
(21272175) and Pu Jiang program of Shanghai (2010–2013) for
generous financial support.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet