Nickel-catalyzed alkynylation of aryl iodides (Sonogashira Reaction) in water

Article abstract of DOI:10.1080/00397910802630187

The Sonogashira coupling of terminal acetylenes with aryl iodides, catalyzed by Ni-Cu, in the presence of sodium lauryl sulfate as the surfactant and cesium carbonate as the base, in water, leads to the formation of aryl alkyne products.

Full text of DOI:10.1080/00397910802630187

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Nickel-Catalyzed Alkynylation of Aryl
Iodides (Sonogashira Reaction) in Water
a
a
a
Mohammad Bakherad , Ali Keivanloo & Samira Mihanparast
a
Faculty of Chemistry , Shahrood University of Technology ,
Shahrood , Iran
Published online: 29 Dec 2009.
To cite this article: Mohammad Bakherad , Ali Keivanloo & Samira Mihanparast (2009) Nickel-
Catalyzed Alkynylation of Aryl Iodides (Sonogashira Reaction) in Water, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 40:2, 179-185, DOI:
10.1080/00397910802630187
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Synthetic Communications , 40: 179–185, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802630187
NICKEL-CATALYZED ALKYNYLATION OF ARYL IODIDES
SONOGASHIRA REACTION) IN WATER
(
Mohammad Bakherad, Ali Keivanloo, and Samira Mihanparast
Faculty of Chemistry, Shahrood University of Technology, Shahrood, Iran
The Sonogashira coupling of terminal acetylenes with aryl iodides, catalyzed by Ni-Cu, in
the presence of sodium lauryl sulfate as the surfactant and cesium carbonate as the base, in
water, leads to the formation of aryl alkyne products.
Keywords: Alkynylation; aryl iodide; nickel catalyst; Sonogashira reaction
INTRODUCTION
The palladium-catalyzed coupling reaction of aryl and vinyl halides with
terminal alkynes (Sonogashira reaction) is one of the most versatile tools in modern
[
1–4]
synthetic chemistry and has great potential for industrial applications.
The
original Sonogashira reaction was generally performed in the presence of large
amounts of palladium and copper(I) iodide as cocatalyst in organic solvents, which
were economically and environmentally malignant.
Compared with the most frequently used, expensive palladium catalysts [e.g.,
Pd(PPh ) , Pd(PPh ) Cl ], the nickel methods have an economic advantage and
hence remain attractive in large- or industrial-scale preparations.
3
4
3 2
2
In recent years, a variety of modifications have been developed for this reaction,
[
5]
[6]
[7]
[8]
including phase-transfer, aqueous, solventless, and copper-free versions and
[9]
[10]
the use of a variety of promoters and solvents. Particularly interesting are the reac-
[
11]
tions catalyzed only by Cu complexes without palladium. However, in most of the
catalytic processes, organic solvents are usually employed as the reaction media, often
creating a great deal of safety, health, and environmental issues as a result of their
flammability, toxicity, and volatility. From economic and environmental standpoints,
it is desirable to avoid any use of hazardous and expensive organic solvents. The use of
water or aqueous solution represents one of the most economically and environmen-
[
12]
tally viable alternatives to organic solvents for metal-catalyzed reactions.
Several examples of palladium-catalyzed Sonogashira reactions in aqueous
[
13]
media have been reported.
iodides with terminal alkynes catalyzed by Ni(PPh ) Cl in the presence of CuI,
Herein, we report the Sonogashira reaction of aryl
3
2
2
sodium lauryl sulfate, and cesium carbonate in water.
Received August 25, 2008.
Address correspondence to Mohammad Bakherad, Faculty of Chemistry, Shahrood University of
Technology, Shahrood, Post Code 3619995161, Iran. E-mail: m.bakherad@yahoo.com
1
79

180
M. BAKHERAD, A. KEIVANLOO, AND S. MIHANPARAST
RESULTS AND DISCUSSION
As a starting point for the development of the methodology and optimization
of the reaction conditions, we chose to study the coupling of iodobenzene with 1-
hexyne as the model reaction, and the effects of the base, surfactant, and catalyst
on the reaction were examined. First, several bases were screened for the reaction
in the presence of a catalytic amount of Ni(PPh ) Cl . As shown in Table 1, the reac-
3
2
2
tion is significantly influenced by the base employed. The reaction works very well
when inorganic bases such as K CO and Cs CO are used (entries 2 and 3 in
Table 1), with the best result obtained in the case of cesium carbonate as the base
2
3
2
3
(entry 3 in Table 1).
The influences of the amounts of surfactant and catalyst were investigated
using the reaction of iodobenzene with 1-hexyne. The results are shown in Table 2.
Increasing the amount of the nickel catalyst could shorten the reaction time but does
not increase the yield (entry 1). Low nickel concentration often prolonged the reac-
tion time and decreased the yield (entry 2). The use of surfactant is also critical for
the success of the reaction: without a surfactant=phase-transfer reagent, the yield
dropped from 85% to 20% (compare entries 3 and 7). We also found that despite
an increase in the amount of the surfactant, the reaction yield did not increase (entry
6). Low surfactant concentration often decreased the yield (entry 5). No reaction was
observed when Ni(II) alone was used as the catalyst (entry 4).
To examine the scope for this coupling reaction, a variety of terminal alkynes
were coupled with various aryl iodides in water in the presence of catalytic amounts
ꢀ
of Ni(PPh ) Cl , CuI, and sodium lauryl sulfate at 60 C. The experimental results are
3
2
2
summarized in Table 3. As shown in this table, the Sonogashira coupling reactions of
aryl iodides with a variety of terminal alkynes proceeded smoothly under mild
conditions, giving the corresponding coupling products in moderate to high yields.
a
Table 1. Effect of base on the Sonogashira reaction of iodobenzene with 1-hexyne in water
b
Yield (%)
Entry
Base
1
2
3
4
5
6
7
KOH
CO
CO
50
75
85
47
60
35
38
K
2
3
Cs
Et
DIEA
2
3
3
N
Pyrrolidine
Piperidine
a
Reaction conditions: iodobenzene (1.0 mmol), 1-hexyne (1.5 mmol), Ni(PPh
3
)
2
Cl
2
(0.01 mmol), CuI
ꢀ
(
0.02 mmol), sodium lauryl sulfate (0.07 mmol), base (2.0 mmol), and degassed water (5 mL) at 60 C for
h under Ar.
4
b
GC yields.

ALKYNYLATION OF ARYL IODIDES
181
Table 2. Effects of catalyst and surfactant on the Sonogashira reaction of iodobenzene with 1-hexyne in
a
water
b
Yield (%)
Entry
Ni(PPh
3
)
2
Cl
2
(mol %)
CuI (mol %)
Sodium lauryl sulfate (mol %)
c
1
2
3
4
5
6
7
2
4
1
7
7
82
d
0.5
1
72
2
7
85
NR
45
1
—
2
7
1
3
1
2
10
—
57
20
1
2
a
Reaction conditions: iodobenzene (1.0 mmol), 1-hexyne (1.50 mmol), Cs
ꢀ
2
CO
3
(2.0 mmol), and degassed
water (5 mL) at 60 C for 4 h under Ar.
b
GC yields.
Reaction time: 2 h.
c
d
Reaction time: 7 h.
The optimized catalyst system was quite general and tolerant of a range of
functional groups.
The aryl iodides with electron-withdrawing groups reacted with 2 to give the
desired products in high yields under the reaction conditions in a short reaction
a
Table 3. Sonogashira reactions of terminal alkynes with aryl iodides
1
R
2
R
b
Yield (%)
Entry
Time (h)
Product
1
2
3
4
5
6
7
8
9
H
n-C
n-C
Ph
Ph
Ph
Ph
Ph
Ph
4
H
9
9
4
3a
3b
3c
3d
3e
3f
85
92
80
85
82
82
74
72
81
70
4-NO
H
2
4
H
2
4.5
2.5
3.5
3.5
5
4-NO
2
3- NO
4-COCH
4-CH
2
3
3
3g
3h
3i
4-OCH
H
3
5
Me
Me
3
Si
Si
5
1
0
4-OCH
3
3
6
3j
a
Reaction conditions: 1 (1.0 mmol), 2 (1.5 mmol), Ni(PPh
3
)
(2.0 mmol), and degassed water (5 mL) at 60 C under Ar.
2
Cl
2
(0.01 mmol), CuI (0.02 mmol), sodium
ꢀ
lauryl sulfate (0.07 mmol), Cs
b
2
CO
3
GC yields.

182
M. BAKHERAD, A. KEIVANLOO, AND S. MIHANPARAST
time. In contrast, the methoxyl-substituted aryl iodide reacted with 2 to give the
desired products in moderate yields in a longer period of reaction time.
In summary, we have developed an efficient method via the nickel-catalyzed
Sonogashira coupling reaction of aryl iodides with terminal alkynes in water using
sodium lauryl sulfate as the surfactant under argon. The reaction is an inexpensive
alternative to the palladium-catalyzed process and results in good yields of the
desired product.
EXPERIMENTAL
General Procedure for the Sonogashira Coupling Reaction
A round-bottom flask with a reflux condenser was charged with aryl iodide
1.0 mmol), terminal acetylene (1.5 mmol), Ni(PPh ) Cl (0.01 mmol), CuI
3 2 2
0.02 mmol), sodium lauryl sulfate (0.07 mmol), and cesium carbonate (2.0 mmol),
(
(
and these ingredients were mixed under an argon atmosphere in 5 mL of water.
ꢀ
The mixture was heated at 60 C for 2–8 h. After completion of the reaction, the
resulting solution was concentrated in vacuo, and the crude product was subjected
to silica-gel column chromatography using CHCl –CH OH (98:2) as eluent to afford
the pure product (Table 3).
3
3
Data
[
14]
ꢁ1
1
-Phenyl-1-hexyne (3a). Colorless liquid. IR (neat): t (cm ) 3050, 2960,
1
2
7
0
1
875, 2232, 1598, 1499, 754, 690. H NMR (400 MHz, CDCl ): d 7.41–7.38 (m, 2H),
3
.32–7.26 (m, 3H), 2.40 (t, J ¼ 7.2 Hz, 2H), 1.62–1.56 (m, 2H), 1.51–1.47 (m, 2H),
1
3
.97 (t, J ¼ 7.2 Hz, 3H). C NMR (100 MHz, CDCl ): d 130.6, 126.2, 127.9,
3
24.2, 91.4, 80.6, 30.9, 21.0, 19.1, 13.8.
[
14]
ꢁ1
1
-(4-Nitrophenyl)-1-hexyne (4b). Yellow liquid. IR (neat): t (cm ) 3080,
1
2
936, 2873, 2234, 1594, 1520, 852. H NMR (400 MHz, CDCl ): d 8.16 (d,
3
J ¼ 8.8 Hz, 2H), 7.52 (d, J ¼ 8.8 Hz, 2H), 2.42 (t, J ¼ 7.2 Hz, 2H), 1.63–1.54 (m,
1
3
2
1
H), 1.50–1.46 (m, 2H), 0.96 (t, J ¼ 7.2 Hz, 3H). C NMR (100 MHz, CDCl ): d
3
46.5, 132.2, 130.9, 123.5, 96.6, 79.2, 30.5, 22.1, 19.2, 13.8.
ꢀ
[15]
Diphenyl acetylene (3c). Mp 59–60 C (lit. 60–61 C). IR (KBr): t (cm
ꢀ
ꢁ1
)
1
3
7
060, 1600, 1492, 756, 690. H NMR (400 MHz, CDCl ): d 7.55–7.51 (m, 4H),
3
1
3
.36–7.32 (m, 6H). C NMR (100 MHz, CDCl ): d 131.8, 128.2, 128.1, 123.3, 89.2.
3
[16]
ꢀ ꢀ
1
-(4-Nitrophenyl)phenylacetylene (3d). Mp 119–120 C (lit. 120–121 C).
1
ꢁ1
IR (KBr): t (cm ) 3084, 2221, 1592, 1515, 1495, 858, 767, 690. H NMR (400 MHz,
CDCl ): d 8.25 (d, J ¼ 8.8 Hz, 2H), 7.63 (d, J ¼ 8.8 Hz, 2H), 7.59–7.56 (m, 2H),
3
1
3
7
1
.40–7.36 (m, 3H). C NMR (100 MHz, CDCl ): d 146.8, 132.1, 131.9, 130.3,
29.5, 128.8, 124.1, 122.3, 94.7, 87.7.
3
ꢀ
[17]
ꢀ
1
-(3-Nitrophenyl)phenylacetylene (3e). Mp 70–71 C (lit.
ꢁ
69–70 C). IR
1
1
(
KBr): t (cm ) 3078, 2210, 1600, 1530, 1521, 1347, 810, 764, 696. H NMR
(
400 MHz, CDCl ): d 8.38 (s, 1H), 8.20–8.17 (m, 1H), 7.80 (d, J ¼ 7.6 Hz, 1H),
3

ALKYNYLATION OF ARYL IODIDES
183
1
3
7
.56–7.50 (m, 3H), 7.42–7.38 (m, 3H). C NMR (100 MHz, CDCl ): d 148.3, 137.1,
3
1
32.1, 129.6, 129.4, 128.2, 126.6, 124.9, 122.9, 122.3, 92.1, 87.0.
[16]
ꢀ ꢀ
1
-(4-Acetylphenyl)phenylacetylene (3f). Mp 94–95 C (lit. 95–96 C). IR
ꢁ
1
1
(
KBr): t (cm ) 3080, 2918, 2223, 1685, 1606, 1265, 835, 697. H NMR (400 MHz,
CDCl ): d 7.98 (d, J ¼ 8.0 Hz, 2H), 7.63 (d, J ¼ 8.0 Hz, 2H), 7.52 (d, J ¼ 2.4 Hz,
3
1
3
2
H), 7.40–7.37 (m, 3H), 2.60 (s, 3H). C NMR (100 MHz, CDCl ): d 197.7,
3
1
36.4, 131.9, 131.6, 128.7, 128.5, 128.2, 128.1, 122.6, 92.9, 88.8, 26.5.
ꢀ
[17]
ꢀ
73–74 C).
1
-(4-Methylphenyl)phenylacetylene (3g). Mp 73–74 C (lit.
ꢁ
1
1
IR (KBr): t (cm ) 3030, 2918, 2860, 2215, 1596, 1510, 818, 697. H NMR
(
3
1
400 MHz, CDCl ): d 7.55–7.52 (m, 2H), 7.42 (d, J ¼ 8.0 Hz, 2H), 7.36–7.29 (m,
3
1
3
H), 7.16 (d, J ¼ 8.0 Hz, 2H), 2.38 (s, 3H). C NMR (100 MHz, CDCl ): d 138.5,
3
31.6, 131.4, 129.2, 128.4, 128.1, 123.8, 120.1, 89.6, 88.7, 21.7.
[17]
ꢀ ꢀ
1
-(4-Methoxyphenyl)phenylacetylene (3h). Mp 59–60 C (lit. 58–59 C).
1
ꢁ
1
IR (KBr): t (cm ) 3025, 2212, 1604, 1500, 1240, 835, 750, 695. H NMR (400 MHz,
1
3
CDCl ): d 7.52–7.43 (m, 4H), 7.31–7.28 (m, 3H), 6.86–6.83 (m, 2H), 3.75 (s, 3H).
C
3
NMR (100 MHz, CDCl ): d 159.6, 133.0, 131.6, 128.3, 128.0, 123.4, 115.6, 113.9,
3
8
9.6, 88.1, 55.4.
[
18]
1
-Phenyl-2-(trimethylsilyl)acetylene (3i). Colorless liquid.
IR (neat): t
ꢁ
1
cm ) 3080, 2160, 1598, 1490, 1250, 860, 755, 690. H NMR (400 MHz, CDCl ):
d 7.47–7.44 (m, 2H), 7.31–7.29 (m, 3H), 0.27 (s, 9H). C NMR (100 MHz, CDCl3):
d 132.1, 128.4, 128.2, 123.0, 105.1, 94.2, 0.01.
1
(
3
1
3
[
18]
1
-(4-Methoxyphenyl)-2-(trimethylsilyl)acetylene (3j). Colorless liquid.
ꢁ
1
1
IR (neat): t (cm ) 2155, 1605, 1510, 1250, 835, 755, 700. H NMR (400 MHz, CDCl ):
3
1
3
d 7.43 (d, J ¼ 8.8 Hz, 2H), 6.80 (d, J ¼ 8.8 Hz, 2H), 3.80 (s, 3H), 0.25 (s, 9H). C NMR
(
100 MHz, CDCl ): d 159.6, 133.7, 115.1, 113.9, 105.4, 92.5, 55.2, 0.07.
3
ACKNOWLEDGMENTS
The authors thank the Research Council of Shahrood University of
Technology for the support of this work.
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