Synthesis of phenyl azides bearing (E)-2-halovinyl group

Article abstract of DOI:10.1007/s11164-011-0323-x

Aseries of phenyl azides bearing (E)-2-halovinyl groups were synthesized in high yields by treatment of (E)-3-(4-azidophenyl)- and (E)-3-(2-azidophenyl) acrylic acid with N-halosuccinimide in the presence of LiOAc. (E)-4-(2-bromovinyl) phenyl azide, one o

Full text of DOI:10.1007/s11164-011-0323-x

Res Chem Intermed (2012) 38:37–44
DOI 10.1007/s11164-011-0323-x
Synthesis of phenyl azides bearing (E)-2-halovinyl
group
•
Wensheng Zhang Chunxiang Kuang Qing Yang
•
Received: 8 March 2011 / Accepted: 5 May 2011 / Published online: 17 May 2011
Ó Springer Science+Business Media B.V. 2011
Abstract A series of phenyl azides bearing (E)-2-halovinyl groups were synthesized
in high yields by treatment of (E)-3-(4-azidophenyl)- and (E)-3-(2-azidophe-
nyl)acrylic acid with N-halosuccinimide in the presence of LiOAc. (E)-4-(2-bromo-
vinyl) phenyl azide, one of the synthesized intermediates, was selected to transform to
a diverse range of phenyl-1, 2, 3-triazoles bearing (E)-4-(2-bromovinyl) groups by
Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction.
Keywords Azide Á (E)-vinyl halide Á N-halosuccinimide Á 1,2,3-Triazole Á
1,3-Dipolar cycloaddition
Introduction
Aromatic azides are versatile synthetic intermediates in organic and bioorganic
chemistry [1–3], with their use as photo affinity labeling reagents for biomolecules
being particularly important [4]. 1,2,3-triazoles have found widespread applications
in pharmaceuticals and agrochemicals [5]. The discovery of Cu (I)-catalyzed 1,3-
dipolar cycloaddition of azides and terminal alkynes [6, 7] has further triggered the
use of 1,2,3-triazoles in bioconjungation, drug discovery [8], material science [9–13],
and combinatorial chemistry [14–17]. In addition, a number of compounds containing
W. Zhang (&)
Department of Chemistry, Jiaozuo Teachers’ College, Shanyang Road 998, Henan Jiaozuo 450001,
China
e-mail: tongjizws@163.com
C. Kuang (&)
Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China
e-mail: kuangcx@tongji.edu.cn
Q. Yang
School of Life Science, Fudan University, Handan Road 220, Shanghai 200433, China
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W. Zhang et al.
1,2,3-triazoles have shown a broad spectrum of biological activities such as
antibacterial [18], herbicidal and fungicidal [19], anti-allergic [20], and anti-HIV
[21].
Meanwhile, (E)-vinyl halides are extremely useful building blocks in organic
synthesis as precursors of vinyl anions [22], and as coupling components in
transition metal-catalyzed coupling reactions [23, 24], which stimulated a demand
for readily accessible 1,2,3-triazoles bearing (E)-halovinyl groups, and, conse-
quently, a need for reliable and efficient methods for the synthesis of phenyl azides
bearing (E)-halovinyl groups.
In this article, we developed a facile method for the stereoselective synthesis of
phenyl azides bearing (E)-halovinyl group 2 from easily available (E)-3-(4-
azidophenyl)- and (E)-3-(2-azidophenyl)acrylic acid 1 (Scheme 1). In addition,
phenyl-1, 2, 3-triazoles bearing (E)-bromovinyl group 3 were synthesized in high
yields by Cu(I)-catalyzed 1,3-dipolar cycloaddition of the corresponding azides 2a
and terminal alkynes.
We first investigated the reaction between 1a and NBS. The reaction carried out
in MeCN–H2O (9:1 v/v) catalyzed by LiOAc smoothly afforded 2a in 96% yield
(Table 1, entry 1). While MeCN–H2O (9:1 v/v) turned out to be the most effective
solvent for the stereocontrolled preparation of (E)-arylvinyl halides 2, addition of
NBS in MeCN dropwise to the reaction system was also essential for the reaction
efficiency. As shown in Table 1, treatment of 1b with NBS using the same
conditions as that for 1a also gave 2b in high yield (entry 2). The reaction for 1a or
1b with NBS could be carried out under ambient temperature, and 2a and 2b were
realized in high yields for only 10 min after the addition of NBS, thus not requiring
microwave conditions as the procedure in the literature indicates [25]. However, the
reaction for 1a with NIS/NCS needed a thermal condition of 80 °C for 1 h to afford
O
X
COOH
LiOAc
N3
N3
N X
+
MeCN-H2O (9:1 v/v)
rt or 80 oC
O
2a, 4-N3, X=Br
1a, 4-N3
1b, 2-N3
2b, 2-N3, X=Br
2c, 4-N3, X=I
2d, 4-N3, X=Cl
X=Br; I or Cl
Br
R
CuI sodium ascorbate
N
2a
N
N
R
DMSO
rt
R = aryl or alkyl
3a-e
Scheme 1 Synthesis of phenyl azides bearing (E)-2-halovinyl group and its transformation to phenyl-1,
2, 3-triazoles bearing (E)-bromovinyl groups
123

Synthesis of phenyl azides
39
Table 1 Synthesis of phenyl azides bearing (E)-2-halovinyl group
Entry
1
Substrate 1
NXS
NBS
Conditiona
Product 2b
Yieldc (%)
96
1a
A
2a
2b
2c
2d
Br
N3
2
3
4
1b
1a
1a
NBS
NIS
A
B
B
93
90
91
Br
N3
I
N3
NCS
Cl
N3
NXS N-halosuccinimide
a
Condition A 1 (1.1 mmol), LiOAc (0.2 mmol), MeCN–H2O (10 mL, 9:1 v/v), NBS (1 mmol) in MeCN
(5 mL), rt, 10 min; Condition B 1 (1.1 mmol), LiOAc (0.2 mmol), MeCN–H2O (10 mL, 9:1 v/v), NIS or
NCS (1 mmol) in MeCN (5 mL), 80 °C, 1 h
b
E/Z [ 99/1, determined by 1H NMR analysis
c
Isolated yields based on N-halosuccinimide
2c and 2d in satisfactory yields (entries 3–4). The results are summarized in
Table 1.
The reaction between 1 and NXS (X = Cl, Br, I) proceeded smoothly due to the
existence of the N3- group in the para- or ortho-position. Attempts to use NaOAc
rather than LiOAc as the catalyst decreased the yields of the compounds 2. Proposed
reaction pathways of the present halode carboxylation are shown in Scheme 2.
Reaction of lithium carboxylate of 1 with NBS gives bromonium ion A, which is
immediately converted to zwitterions B. Zwitterions B would eliminate carbon
dioxide to give (E)-b-arylvinyl bromide 2.
The Cu (I)-catalyzed 1, 3-dipolar cycloaddition reaction of 2a and terminal
alkynes were next surveyed. The reaction carried out in DMSO at ambient
temperature under nitrogen atmosphere for 12 h afforded 3a–3e in a yield of
85–95% (Table 2).
Experimental
Melting points were recorded using a Kru¨ss Optronic KSPII melting-point meters
and were uncorrected. IR spectra were performed on a Nexus FT-IR spectropho-
1
tometer. H NMR and 13C NMR spectra were recorded using a Bruker AM-500
123

40
W. Zhang et al.
O
N X
COOLi
COOH
LiOAc
O
N3
N3
X=Br; I or Cl
1
COO
Br
COO
H
X
- CO2
N3
+
X
N3
N3
H
2
B
A
Scheme 2
Table 2 Transformation of (E)-4-(2-bromovinyl) phenyl azide to phenyl-1, 2, 3-triazoles bearing (E)-
bromovinyl group
Entry
1
Alkynes
Product 3a, b
Yieldc (%)
95
3a
3b
3c
3d
3e
EtO2C
Br
Br
Br
Br
N
N
EtO2C
N
2
3
4
5
89
87
88
85
HOH C
2
N
HO H2C
N
N
n-C5H11
N
n-C5H11
N
N
N
N
N
Br
Br
Br
N
N
N
a
Reaction condition: 2a (1 mmol), alkynes (1.05 mmol), DMSO (5 mL), sodium ascorbate (0.15 mmol),
CuI (0.15 mmol), N2, rt, 12 h
b
E/Z [ 99/1, determined by 1H NMR analysis
c
Isolated yields based on 2a
123

Synthesis of phenyl azides
41
spectrometer in CDCl3 with SiMe4 as an internal standard. Elemental analyses were
performed with a Perkin-Elmer 2400 CHNS elemental analyzer. Commercially
obtained reagents were used without further purification. All reactions were
monitored by TLC with HuanghaiGF 254 silica gel-coated plates. Column
chromatography was carried out using 300–400 mesh silica gel at medium pressure.
Preparation of compounds 1
Zinc powder (3.900 g, 60 mmol) was added to 100 mL of stirred HOAc-H2O (9:1
v/v) suspension of 3-(4- or 2-nitrophenyl)acrylic acid (5.790 g, 30 mmol), which
was prepared from 4- or 2-nitrobenzaldehyde according to a conventional synthetic
route [26]. The reaction system was stirred at ambient temperature for 0.5 h and
filtered. The filtrate was cooled to 0 °C in an ice bath. A solution of sodium nitrite
(2.484 g, 36 mmol) in 20 mL of water was added dropwise to the reaction system.
The mixture was stirred at 0 °C for 10 min. Sodium azide (2.340 g, 36 mmol) in
20 mL water was added dropwise to the reaction system. After the reaction
completed, the solvent was evaporated. The combined organic layers were washed
with brine (100 9 2 mL) and cooled water (100 mL), and dried over anhydrous
Na2SO4. Evaporation of the solvent gave a crude product, which was recrystallized
from EtOAc-hexane to yield 1a or 1b as a brown solid (90%), 1a: mp
197.3–197.5 °C (lit. 195–196 °C); 1b: mp 185.5–186.1 °C (lit. 186 °C) [27].
General procedure for the synthesis of phenyl azides bearing (E)-vinyl halide
group 2
N-halosuccinimide (1 mmol) in MeCN (5 mL was added dropwise to a stirred
MeCN–H2O (10 mL, 9:1 v/v) suspension of 1 (1.1 mmol) and LiOAc (0.2 mmol).
After the addition of N-halosuccinimide was completed, the reaction mixture was
stirred at ambient temperature for 10 min (for NBS) or at 80 °C for 1 h (for NIS and
NCS). The solvent was then evaporated. EtOAc (30 mL) was added to the residue
and filtered. The filtrate was washed with brine (30 9 2 mL) and cooled water
(30 mL), and dried over anhydrous Na2SO4. Evaporation of the solvent gave the
crude product, which was subjected to column chromatography (silica gel,
petroleum ether) to afford product 2a–d.
(E)-1-azido-4-(2-bromovinyl)benzene (2a). Red liquid. Found (%): C, 42.99; H,
2.77; N, 18.69; Br, 35.55. C8H6BrN3. Calculated (%): C, 42.88; H, 2.70; N, 18.75;
1
Br, 35.66. H NMR (500 MHz, CDCl3), d: 6.66 (d, 1H, =CH–Br, J = 14.0 Hz);
6.91 (d, 2H, Ar, J = 8.5 Hz); 6.99 (d, 1H, Ar–CH= , J = 14.0 Hz); 7.21 (d, 2H, Ar,
J = 8.5 Hz). 13C NMR (125 MHz, CDCl3), d: 105.28, 118.38, 126.45, 131.77,
135.09, 138.86.
(E)-1-azido-2-(2-bromovinyl)benzene (2b). Red liquid. Found (%): C, 42.92; H,
2.72; N, 18.67; Br, 35.69. C8H6BrN3. Calculated (%): C, 42.88; H, 2.70; N, 18.75;
1
Br, 35.66. H NMR (500 MHz, CDCl3), d: 6.86 (d, 1H, =CH–Br, J = 14.0 Hz),
7.08–7.05 (m, 2H, Ar), 7.30 (d, 1H, Ar–CH= , J = 14.0 Hz), 7.32–7.34 (m, 2H,
Ar). 13C NMR (125 MHz, CDCl3), d: 107.76, 117.64, 123.94, 126.39, 128.35,
131.31, 135.86.
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W. Zhang et al.
(E)-1-azido-4-(2-iodovinyl)benzene (2c). Purple liquid. Found (%): C, 35.39; H,
2.16; N, 15.69; I, 46.76. C8H6IN3. Calculated (%): C, 35.45; H, 2.23; N, 15.50; I,
46.82. 1H NMR (500 MHz, CDCl3), d: 6.78 (d, 1H, =CH–I, J = 15.0 Hz), 6.96 (d,
2H, Ar, J = 8.5 Hz), 7.27 (d, 2H, Ar, J = 8.5 Hz), 7.37 (d, 1H,Ar=CH–,
J = 15.0 Hz). 13C NMR (125 MHz, CDCl3), d: 76.23, 119.27, 127.34, 134.57,
139.93, 143.81.
(E)-1-azido-4-(2-chlorovinyl)benzene (2d). Yellow liquid. Found (%): C, 53.65;
H, 3.29; N, 23.31; Cl, 19.76. C8H6ClN3. Calculated (%): C, 53.50; H, 3.37; N,
23.40; Cl, 19.74. 1H NMR (500 MHz, CDCl3), d: 6.59 (d, 1H, =CH–Cl,
J = 14.0 Hz), 6.77 (d, 1H, Ar–CH= , J = 14.0 Hz), 6.96 (d, 2H, Ar,
J = 8.5 Hz), 7.21 (d, 2H, Ar, J = 8.5 Hz). 13C NMR (125 MHz, CDCl3), d:
118.50, 119.36, 127.44, 131.68, 132.22, 139.71.
General procedure for the synthesis of compounds 3
Alkynes (1.05 mmol), sodium ascorbate (0.15 mmol) and CuI (0.15 mmol) were
added to a stirred DMSO (5 mL) solution of 2 (1 mmol). The reaction mixture was
stirred at ambient temperature under nitrogen atmosphere for 12 h. The solvent was
evaporated. EtOAc (30 mL) was added to the residue and filtered. The filtrate was
washed with brine (30 9 2 mL) and cooled water (30 mL), and dried over
anhydrous Na2SO4. Evaporation of the solvent gave the crude product, which was
subjected to column chromatography (silica gel, EtOAc/petroleum ether) to afford
product 3a–3e.
(E)-1-(4-(2-Bromovinyl)phenyl)-1,2,3-triazole-4-carboxylic acid ethyl ester (3a).
Light yellow solid. mp 179.2–179.6 °C. Found (%): C, 48.44; H, 3.73; N, 13.02; Br,
24.83. C13H12BrN3O2. Calculated (%): C, 48.47; H, 3.75; N, 13.04; Br, 24.80. H
1
NMR (500 MHz, CDCl3), d: 1.37 (t, 3H, –CH3, J = 7.0 Hz), 4.40 (q, 2H, –CH2–,
J = 7.0 Hz), 6.84 (d, 1H, =CH–Br, J = 14.0 Hz), 7.09 (d, 1H, Ar–CH= ,
J = 14.0 Hz), 7.42 (d, 2H, Ar, J = 8.5 Hz), 7.67 (d, 2H, Ar, J = 8.5 Hz), 8.44
(s, 1H, –N=N–CH=). 13C NMR (125 MHz, CDCl3), d: 14.31, 61.55, 108.89, 121.06,
125.21, 127.46, 135.56, 135.79, 137.15, 140.97, 160.53.
(E)-(1-(4-(2-Bromovinyl)phenyl)-1,2,3-triazol-4-yl)methanol (3b). White solid.
mp 166.8–167.2 °C. Found (%): C, 47.11; H, 3.57; N, 15.01; Br, 28.56.
C11H10BrN3O. Calculated (%): C, 47.16; H, 3.60; N, 15.00; Br, 28.52. H NMR
1
(300 MHz, DMSO-d6), d: 4.71 (s, 2H, –CH2–), 7.11 (d, 1H, =CH–Br,
J = 14.0 Hz), 7.18 (d, 1H, Ar–CH= , J = 14.0 Hz), 7.56 (d, 2H, Ar,
J = 9.0 Hz), 7.82 (d, 2H, Ar, J = 9.0 Hz), 8.40 (s, 1H, –N=N–CH=). 13C NMR
(125 MHz, CDCl3), d: 55.62, 108.69, 120.30, 120.44, 127.55, 135.78, 135.85,
136.53, 149.49.
(E)-1-(4-(2-Bromovinyl)phenyl)-4-pentyl-1,2,3-triazole (3c). White solid. mp
99.6–100.1 °C. Found (%): C, 56.22; H, 5.65; N, 13.09; Br, 24.99. C15H18BrN3.
Calculated (%): C, 56.26; H, 5.67; N, 13.12; Br, 24.95. 1H NMR (300 MHz,
DMSO-d6), d: 0.91 (t, 3H, –CH3, J = 7.0 Hz), 1.24–1.26 (m, 2H, CH3–CH2–),
1.23–1.40 (m, 4H, –(CH2)2–), 1.72–1.77 (m, 2H, –CH2–), 2.79 (t, 2H, –CH2–,
J = 8.0 Hz), 6.86 (d, 1H, =CH–Br, J = 14.0 Hz), 7.17 (d, 1H, Ar–CH= ,
J = 14.0 Hz), 7.43 (d, 2H, Ar, J = 8.5 Hz), 7.70 (d, 2H, Ar, J = 8.5 Hz), 7.71
123

Synthesis of phenyl azides
43
(s, 1H, –N=N–CH=). 13C NMR (125 MHz, CDCl3): d 13.95, 22.39, 25.60, 29.03,
31.04, 107.96, 118.47, 120.52, 127.24, 135.81, 135.98, 136.76, 149.34.
(E)-1-(4-(2-Bromovinyl)phenyl)-4-phenyl-1,2,3-triazole (3d). Yellow solid. mp
215.4–216.0 °C. Found (%): C, 58.89; H, 3.70; N, 12.85; Br, 24.56. C16H12BrN3.
Calculated (%): C, 58.91; H, 3.71; N, 12.88; Br, 24.50. 1H NMR (500 MHz,
CDCl3), d: 6.90 (d, 1H, =CH–Br, J = 14.0 Hz), 7.16 (d, 1H, Ar–CH= ,
J = 14.0 Hz), 7.37–7.49 (m, 5H, Ar), 7.78 (d, 2H, Ar, J = 8.5 Hz), 7.91 (d, 2H,
Ar, J = 8.5 Hz), 8.19 (s, 1H, –N=N–CH=). 13C NMR (125 MHz, CDCl3), d:
108.28, 117.25, 120.73, 125.90, 127.38, 128.53, 128.95, 130.89, 135.79, 136.41,
136.57, 146.62.
(E)-4-(4-Bromophenyl)-1-(4-(2-bromovinyl)phenyl)-1,2,3-triazole (3e). Yellow
solid. mp 206.3–206.9 °C. Found (%): C, 47.40; H, 2.72; N, 10.33; Br, 39.56.
C16H11Br2N3. Calculated (%): C, 47.44; H, 2.74; N, 10.37; Br, 39.45. H NMR
1
(300 MHz, DMSO-d6), d: 7.32 (d, 1H, =CH–Br, J = 14.0 Hz), 7.46 (d, 1H, Ar–
CH= , J = 14.0 Hz), 7.72 (d, 2H, Ar, J = 8.1 Hz), 7.75 (d, 2H, Ar, J = 8.1 Hz),
7.90 (d, 2H, Ar, J = 8.5 Hz), 7.94 (d, 2H, Ar, J = 8.5 Hz), 9.38 (s, 1H, –N=N–
CH=). 13C NMR (125 MHz, CDCl3), d: 109.41, 120.33, 121.63, 127.53, 127.85,
128.88, 129.81, 131.49, 132.09, 136.18, 136.37, 146.75.
Conclusion
In conclusion, we developed a facile method for the synthesis of phenyl azides
bearing (E)-halovinyl group by treatment of easily available (E)-3-(4-azidophenyl)-
and (E)-3-(2-azidophenyl)-acrylic acid with N-halosuccinimide (NBS, NIS, and
NCS) under mild condition in high yields. Furthermore, a diverse range of phenyl-1,
2, 3-triazoles bearing (E)-bromovinyl group were synthesized by Cu(I)-catalyzed
1,3-dipolar cycloaddition of (E)-4-(2-bromovinyl) phenyl azide and alkyl or aryl
terminal alkynes. The synthetic applications of these compounds were in progress in
our laboratory.
Acknowledgments This study was supported by Natural Science Foundation of China (No. 30873153),
Program for Science and Technology Innovation Talents in Universities of He’nan Province (No.
2011HASTIT032) and Foundation of He’nan Educational Committee (No. 2009C150001, No.
2011C150001).
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