Gold(I) iodide catalyzed sonogashira reactions

Article abstract of DOI:10.1002/ejoc.200800765

Gold(I) iodide catalyzed Sonogashira reactions have been developed. Terminal alkynes reacted with aryl iodides and bromides smoothly in the presence of AuI (1 mol-%) and dppf (1 mol-%) in toluene to generate the corresponding cross-coupling products in good to excellent yields. Furthermore, aromatic terminal alkynes could also react with 2-iodoaniline to form substituted indoles in excellent yields through a coupling-cyclization reaction sequence under the present reaction conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.

Full text of DOI:10.1002/ejoc.200800765

FULL PAPER
DOI: 10.1002/ejoc.200800765
Gold(I) Iodide Catalyzed Sonogashira Reactions
Pinhua Li,[a] Lei Wang,*[a,b] Min Wang,[a] and Feng You[a]
Keywords: C–C coupling / Gold / Alkynes / Nitrogen heterocycles
Gold(I) iodide catalyzed Sonogashira reactions have been
developed. Terminal alkynes reacted with aryl iodides and
bromides smoothly in the presence of AuI (1 mol-%) and
dppf (1 mol-%) in toluene to generate the corresponding
cross-coupling products in good to excellent yields. Further-
more, aromatic terminal alkynes could also react with 2-
iodoaniline to form substituted indoles in excellent yields
through a coupling–cyclization reaction sequence under the
present reaction conditions.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
with a Schiff base and triphenylphosphane ligands, and
only four examples (only aryl iodides and aromatic terminal
alkynes) were carried out in low yields when they used the
AuI–Schiff base–PPh3 complex as a catalyst for the Sono-
gashira reactions.[14] In addition, these kinds of catalyst
systems suffer from drawbacks, as they require tedious
multistep syntheses. It is desirable to develop a more simple
and practical in situ Au/ligand catalyst systems for the
Sonogashira reactions.
Herein, we report gold(I) iodide catalyzed Sonogashira
reactions of terminal alkynes with aryl iodides and bro-
mides, which generated the corresponding cross-coupling
products in good to excellent yields in the presence of AuI
(1 mol-%) and dppf (1 mol-%) in toluene. Furthermore, ter-
minal alkynes could also react with 2-iodoaniline to form
the substituted indoles through a cross-coupling–cyclization
reaction sequence in excellent yields under the present reac-
tion conditions (Scheme 1).
Introduction
Gold (and its complexes) catalyzed organic transforma-
tions have been a focus of attention in recent years.[1] Gold-
mediated organic transformations, such as oxidation of
CO,[2] oxidation of alcohols,[3] direct arene functionaliza-
tion,[4] and carbene insertion into benzene and O–H and
N–H bonds,[5] have been developed recently. Both gold(I)
and gold(III) species also show unique activities in mediat-
ing reactions involving alkynes,[6] alkenes,[7] and allenes.[8]
To the best of our knowledge, gold-catalyzed direct carbon–
carbon and carbon–heteroatom bond coupling reactions
have been less explored. In 2003, Li and his coworkers re-
ported gold(I)-catalyzed three-component coupling reac-
tions of aldehydes, alkynes, and amines.[9] Corma and his
coworkers developed Au/CeO2 and AuIII Schiff base com-
plex catalyzed homocouplings of phenylboronic acid in
2005,[10] and Corma and his group also developed NHC–
gold(I) complexes for the Suzuki reaction in 2006.[11] Sono-
gashira reactions, that is, the palladium complex/CuI-cata-
lyzed cross-coupling reactions of terminal alkynes with aryl
and alkenyl halides, have been widely investigated in the
past decades.[12] Palladium, copper, nickel, ruthenium, and
indium have been used to catalyze the reactions indepen-
dently, whereas little attention has been paid to the catalytic
activities of silver and gold in Sonogashira reactions. Our
group successfully developed silver(I) iodide catalyzed
Sonogashira reactions,[13] but coincidentally, while that
manuscript was being prepared, a similar strategy appeared.
Corma and coworkers also developed gold-catalyzed Sono-
Scheme 1.
gashira reactions. They prepared AuI and AuIII complexes Results and Discussion
Our initial investigation was directed towards exploring
[a] Department of Chemistry, Huaibei Coal Teachers College,
Huaibei, Anhui 235000, P. R. China
the reaction conditions for the cross coupling of p-iodoani-
sole with phenylacetylene catalyzed by gold(I). At first, the
effect of several different solvents on the reaction catalyzed
by gold(I) iodide was examined, and a significant solvent
effect was observed (Table 1). When the reactions were con-
Fax: +86-561-3090-518
E-mail: leiwang@hbcnc.edu.cn
[b] State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, P. R. China
5946
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 5946–5951

Gold(I) Iodide Catalyzed Sonogashira Reactions
ducted in toluene and xylene, good yields of the products Table 2. Effect of ligands on the Sonogashira reaction.[a]
were obtained. The use of dioxane, ethanol, acetonitrile,
and water as solvents resulted in middle yields of the prod-
ucts. It is worth noting that no desired cross-coupling prod-
uct was observed when the reactions were performed in
DMF and DMSO (Table 1, Entries 1–12).
Entry
Ligand (amount)
Yield[b] [%]
Table 1. Effect of solvents on the Sonogashira reaction.[a]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
–
0
Ͻ10
Ͻ10
Ͻ10
70
64
66
79
73
96
96
68
0
P(OPh)3 (2 mol-%)
P(OMe)3 (2 mol-%)
P(nBu)3 (2 mol-%)
PPh3 (2 mol-%)
P(o-tolyl)3 (2 mol-%)
(p-tolyl)PPh2 (2 mol-%)
binap (1 mol-%)
En-
try
Temperature [°C]
Yield[b] [%]
bisbenzodioxanphos (1 mol-%)
dppf (1 mol-%)
Solvent
dppf (2 mol-%)
dppf (0.5 mol-%)
N,N-dimethylglycine (1 mol-%)
1,10-phenanthroline (1 mol-%)
α,α-bipyridine (1 mol-%)
8-hydroxyquinoline (1 mol-%)
dabco (1 mol-%)
1
2
3
4
5
6
7
8
9
C2H5OH
CH3CN
THF
acetone
dioxane
DMF
78
80
70
52
50
Ͻ10
Ͻ10
50
0
0
0
0
0
60
100
130
130
100
120
130
90
DMSO
H2O
DMSO/H2O (1:1)
toluene
0
61
0
96
25
96
[a] Phenylacetylene (102 mg, 1.0 mmol), p-iodoanisole (234 mg,
1.0 mmol), AuI (3.2 mg, 0.01 mmol), K2CO3 (276 mg, 2.0 mmol),
and ligand (amount indicated) in toluene (2 mL) at 130 °C for 24 h.
[b] Isolated yields.
10
11
12
toluene
xylene
130
[a] Phenylacetylene (102 mg, 1.0 mmol), p-iodoanisole (234 mg,
1.0 mmol), AuI (3.2 mg, 0.01 mmol), dppf (5.5 mg, 0.01 mmol),
K2CO3 (276 mg, 2.0 mmol) in solvent (2 mL) at the temperature
indicated for 24 h. [b] Isolated yields.
and KOAc were substantially less effective. However, pyr-
idine, triethylamine, and piperidine were no longer the effec-
tive bases in this catalytic system (Table 3, Entries 1–11).
Table 3. Effect of bases on the Sonogashira reaction.[a]
We then turned our attention to investigate the ligand
effects on the reactions. No reaction occurred in the absence
of any ligand (Table 2, Entry 1). Among the ligands tested,
1,1Ј-bis(diphenylphosphanyl)ferrocene (dppf) proved to be
the best of choice, whereas the other phosphane ligands,
such as triphenylphosphane (PPh3), tris(2-tolyl)phosphane
[b]
Entry
Base
Yield [%]
[P(o-tolyl)3],
p-tolyldiphenylphosphane
(p-tolylPPh2),
1
2
3
4
5
6
7
8
9
K2CO3
Na2CO3
Cs2CO3
K3PO4
KF
KOAc
96
90
92
82
68
59
Ͻ10
65
Ͻ5
Ͻ5
Ͻ5
2,3,2Ј,3Ј-tetrahydro-5,5Ј-bis(1,4-benzodioxin)-6,6Ј-diylbis-
(diphenylphosphane) (Bisbenzodioxanphos), and 2,2Ј-
bis(diphenylphosphanyl)-1,1-binaphthalene (binap) were in-
ferior (Table 2, Entries 5–12). The experimental results also
indicated that when P(OMe)3, P(OPh)3, and P(nBu)3 were
used as the ligand, yields of less than 10% were obtained
(Table 2, Entries 2–4). However, when N,N-dimethylglycine,
1,4-diazabicyclo[2.2.2]octane (dabco), α,α-bipyridine, 1,10-
phenanthroline, and 8-hydroxyquinoline were employed in-
stead of dppf, respectively for the above-mentioned reac-
tion, no cross-coupling product was isolated (Table 2, En-
tries 13–17). The results also showed that when the mol ra-
tio of dppf to AuI was less than 1:1, the reaction was not
complete, whereas ratios equal to or more than 1:1 provided
satisfactory results (Table 2, Entries 10–12).
KOH
tBuOK
pyridine
triethylamine
piperidine
10
11
[a] Phenylacetylene (102 mg, 1.0 mmol), p-iodoanisole (234 mg,
1.0 mmol), AuI (3.2 mg, 0.01 mmol), dppf (5.5 mg, 0.01 mmol),
base (2.0 mmol) in toluene (2 mL) at 130 °C for 24 h. [b] Isolated
yields.
Finally, the catalytic activity of gold salts for the reac-
tions was explored. According to our experimental results,
Also, the effect of several different bases on the Sonoga- AuIII, AuI, and Au0 were all effective catalysts for Sonoga-
shira reactions catalyzed by gold(I) iodide was investigated. shira reactions in the presence of dppf, and AuI was the
With regard to other reaction conditions, K2CO3 was found best of choice, which did not agree with the literature[14]
to act as an excellent base. Na2CO3, Cs2CO3, K3PO4, KF, (Table 4, Entries 1–15). It is worth noting that homocoup-
and tBuOK were also effective. Other bases, such as KOH ling of the terminal alkynes did not occurred with the use
Eur. J. Org. Chem. 2008, 5946–5951
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5947

P. Li, L. Wang, M. Wang, F. You
FULL PAPER
of our procedure. Recently, iron species also showed high ditions, and the results are summarized in Table 5. Electron-
activities in mediating reactions involving alkynes and al- neutral, electron-rich, and electron-poor aryl iodides re-
kenes.[15] We wondered whether iron had any catalytic ac- acted with phenylacetylene very well to generate the corre-
tivity in the Sonogashira reaction. However, no desired sponding cross-coupling products in excellent yields
product was isolated when FeIII, FeII, or Fe (nanosized (Table 5, Entries 1–4, 6–7, 9, and 11–13), whereas the cross
powder) was added to the reactions instead of gold coupling did not tolerate ortho-substituted aryl iodides
(Table 4, Entry 12–14). In addition, no desired product was (Table 5, Entries 5, 8, and 10). Regardless of their electronic
isolated in the absence of a gold source (Table 4, Entry 15). character, both aromatic terminal alkynes and aliphatic ter-
We also investigated the effect of the amount of AuI. The minal alkynes coupled with iodobenzene smoothly to pro-
experimental data indicated that the reaction was not com- duce the desired products in excellent yields (Table 5, En-
plete when the amount of AuI was less than 1 mol-% at tries 3 and 14–21). Activated aryl bromides also reacted
130 °C for 24 h. When the reaction was carried out under with phenylacetylene to provide the corresponding products
microwave irradiation by using a 650-W microwave oven in excellent yields (Table 5, Entries 22–27), but electron-rich
(Sanle WP 650D at 2450 MHz) at 50% power for 0.5 h, aryl bromides, such as p-bromoanisole, only afforded the
91% yield of the cross-coupling product was isolated product in poor yield (35%; Table 5, Entry 28).
(Table 4, Entry 11). Fortunately, excellent yield of the de-
Table 5. AuI-catalyzed Sonogashira reactions.[a]
sired product was observed with 0.5 mol-% of AuI when the
reaction time was prolonged (Table 4, Entry 9).
Table 4. Effect of gold and iron sources on the Sonogashira reac-
tion.[a]
Entry
Alkyne
Organic halide
Yield[b] [%]
1
2
3
4
5
6
7
8
C6H5CϵCH
C6H5CϵCH
p-CH3OC6H4I
p-CH3C6H4I
C6H5I
m-CH3C6H4I
o-CH3C6H4I
p-CF3C6H4I
m-CF3C6H4I
o-CF3C6H4I
p-FC6H4I
96
98
99
92
35
99
91
42
99
45
99
91
99
78
92[c]
82[c]
97
98
99
99
95
91
79
92
81
94
93
35[c]
C6H5CϵCH
C6H5CϵCH
C6H5CϵCH
Entry
Gold or iron source (amount)
Yield[b][%]
C6H5CϵCH
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
AuCl3 (1 mol-%)
HAuCl4 (1 mol-%)
AuCl (1 mol-%)
90
75
95
55
20
96
96
84
96[d]
72[e]
91[f]
0
C6H5CϵCH
C6H5CϵCH
9
C6H5CϵCH
[c]
Au0 colloid (1 mol-%)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
C6H5CϵCH
o-FC6H4I
[c]
Au0 on PVP (1 mol-%)
C6H5CϵCH
p-NO2C6H4I
m-NO2C6H4I
p-CH3COC6H4I
C6H5I
AuI (1 mol-%)
AuI (2 mol-%)
AuI (0.5 mol-%)
AuI (0.5 mol-%)
AuI (1 mol-%)
AuI (1 mol-%)
FeCl3 (1 mol-%)
FeCl2 (1 mol-%)
nanosized Fe0 (1 mol-%)
–
C6H5CϵCH
C6H5CϵCH
n-C8H17CϵCH
n-C8H17CϵCH
n-C6H13CϵCH
p-CH3C6H4CϵCH
p-BrC6H4CϵCH
p-ClC6H4CϵCH
p-FC6H4CϵCH
p-C6H4C6H4CϵCH
C6H5CϵCH
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
0
0
0
2-bromopyridine
3-bromopyridine
p-NO2C6H4Br
m-NO2C6H4Br
p-CNC6H4Br
p-CH3COC6H4Br
p-CH3OC6H4Br
[a] Phenylacetylene (102 mg, 1.0 mmol), p-iodoanisole (234 mg,
1.0 mmol), gold or iron source (amount indicated), dppf (5.5 mg,
0.01 mmol), K2CO3 (276 mg, 2.0 mmol) in toluene (2 mL) at
130 °C for 24 h. [b] Isolated yields. [c] It was prepared according to
the literature.[3b] [d] Reaction time was 48 h. [e] Reaction time was
12 h. [f] The reaction was carried out under microwave irradiation
by using a 650-W microwave oven (Sanle WP 650D at 2450 MHz)
at 50% power for 0.5 h.
C6H5CϵCH
C6H5CϵCH
C6H5CϵCH
C6H5CϵCH
C6H5CϵCH
C6H5CϵCH
[a] Alkyne (1.0 mmol), organic halide (1.0 mmol), AuI (3.2 mg,
0.01 mmol), dppf (5.5 mg, 0.01 mmol), K2CO3 (276 mg, 2.0 mmol)
in toluene (2 mL) at 130 °C for 24 h. [b] Isolated yields. [c] AuI
(0.02 mmol) and dppf (0.02 mmol) were added to the reaction.
During the course of further optimization of the reaction
conditions, when using 1 mol-% of AuI, the reactions were
generally completed in a matter of hours, but the time, as
expected, was inversely proportional to the temperature. A
We also investigated the application of this coupling–cy-
reaction temperature of 130 °C was found to be optimal. clization reaction sequence to the synthesis of substituted
Thus, the optimized reaction conditions for the Sonoga- indoles, and the results are listed in Table 6. The reaction
shira reactions are: AuI (1 mol-%), dppf (1 mol-%), K2CO3 of o-iodoaniline with aromatic terminal alkynes proceeded
(2 equiv.) in toluene at 130 °C for 24 h.
very well and excellent yields of the desired products were
We investigated the coupling reactions by using a variety achieved (Table 6, Entries 1–4). However, only a moderate
of aryl iodides and bromides and a wide range of terminal yield of the desired product was obtained for an aliphatic
alkynes as the substrates under the optimized reaction con- terminal alkyne (Table 6, Entry 5). N-substituted o-iodoani-
5948
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Eur. J. Org. Chem. 2008, 5946–5951

Gold(I) Iodide Catalyzed Sonogashira Reactions
(4-Methoxyphenyl)phenylacetylene:[16] 1H NMR (300 MHz,
CDCl3): δ = 7.54–7.44 (m, 4 H, ArH), 7.38–7.32 (m, 3 H, ArH),
6.89 (d, J = 8.4 Hz, 2 H, ArH), 3.83 (s, 3 H, ArOCH3) ppm. 13C
NMR (75 MHz, CDCl3): δ = 159.6, 133.1, 131.4, 128.4, 127.9,
123.4, 115.4, 113.9, 89.2, 88.1, 55.4 ppm.
Phenyl-p-tolylacetylene:[17] 1H NMR (300 MHz, CDCl3): δ = 7.50–
7.45 (m, 2 H, ArH), 7.44 (d, J = 8.1 Hz, 2 H, ArH), 7.28–7.22 (m,
3 H, ArH), 7.15 (d, J = 7.8 Hz, 2 H, ArH), 2.31 (s, 3 H, ArCH3)
ppm. 13C NMR (75 MHz, CDCl3): δ = 138.2, 131.6, 129.0, 128.1,
128.0, 123.5, 120.0, 89.8, 88.5, 21.5 ppm.
Diphenylacetylene:[18] 1H NMR (300 MHz, CDCl3): δ = 7.58–7.53
(m, 4 H, ArH), 7.35–7.29 (m, 6 H, ArH) ppm. 13C NMR (75 MHz,
CDCl3): δ = 131.7, 128.5, 128.2, 123.2, 89.5 ppm.
Phenyl-m-tolylacetylene:[19] 1H NMR (300 MHz, CDCl3): δ = 7.57–
7.53 (m, 2 H, ArH), 7.42–7.29 (m, 5 H, ArH), 7.29–7.16 (m, 2 H,
ArH), 2.38 (s, 3 H, ArCH3) ppm. 13C NMR (75 MHz, CDCl3): δ
= 138.0, 132.1, 131.6, 129.3, 128.8, 128.4, 128.2, 128.1, 123.4, 123.1,
89.7, 89.1, 21.4 ppm.
lines, such as N-Boc, N-p-Ts, N-Ms, and N-acetyl o-iodoan-
ilines, also reacted with phenylacetylene to provide the
coupling–cyclization reaction products in good yields
(Table 6, Entries 7–10). Unfortunately, when o-bromoani-
line was used as the substrate instead of o-iodoaniline, no
desired product was obtained (Table 6, Entry 6). However,
when o-iodophenol was used as the starting material, no
desired product was isolated. The mechanism of the gold-
catalyzed Sonogashira coupling reaction and the effect of
the ligand are not fully clear and further investigation is
currently underway in our laboratory.
Table 6. AuI-catalyzed coupling–cyclization reactions of alkynes
and o-iodoanilines.[a]
Phenyl-o-tolylacetylene:[20] 1H NMR (300 MHz, CDCl3): δ = 7.68–
7.58 (m, 3 H, ArH), 7.44–7.39 (m, 3 H, ArH), 7.31–7.20 (m, 3 H,
ArH), 2.63 (s, 3 H, ArCH3) ppm. 13C NMR (75 MHz, CDCl3): δ
= 140.1, 132.8, 131.9, 131.8, 129.6, 129.1, 128.6, 128.5, 128.2, 125.7,
88.5, 81.9, 20.7 ppm.
(4-Trifluoromethylphenyl)phenylacetylene:[21] 1H NMR (300 MHz,
CDCl3): δ = 7.64–7.61 (m, 4 H, ArH), 7.59–7.55 (m, 2 H, ArH),
7.39–7.36 (m, 3 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ =
131.9, 131.8, 129.9 (J = 32.4 Hz), 128.9, 128.5, 127.1 (J = 1.4 Hz),
125.2 (J = 3.9 Hz), 123.9 (J = 270.1 Hz), 122.6, 91.8, 87.9 ppm.
(3-Trifluoromethylphenyl)phenylacetylene:[22] 1H NMR (300 MHz,
CDCl3): δ = 7.78–7.73 (m, 1 H, ArH), 7.74–7.63 (m, 1 H, ArH),
7.61–7.51 (m, 3 H, ArH), 7.47–7.42 (m, 1 H, ArH), 7.43–7.32 (m,
3 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 134.8, 131.8,
131.2 (q, J = 32 Hz), 129.7, 128.9, 128.5, 124.8, 124.4, 124.1, 123.9
(q, J = 270 Hz), 122.6, 90.9, 87.9 ppm.
Entry
Alkyne
R2
X
Yield[b] [%]
1
2
3
4
5
6
7
8
9
C6H5CϵCH
p-CH3C6H4CϵCH
p-ClC6H4CϵCH
p-FC6H4CϵCH
n-C6H13CϵCH
C6H5CϵCH
H
H
H
H
H
I
I
I
I
I
Br
I
I
I
I
99
99
96
94
41
0
72
73
60
79
H
C6H5CϵCH
Boc
p-Ts
Ms
acetyl
C6H5CϵCH
C6H5CϵCH
10
C6H5CϵCH
[a] Alkyne (1.0 mmol), o-iodoaniline (1.0 mmol), AuI (3.2 mg,
0.01 mmol), dppf (5.5 mg, 0.01 mmol), K2CO3 (276 mg, 2.0 mmol)
in toluene (2 mL) at 130 °C for 24 h. [b] Isolated yields.
(2-Trifluoromethylphenyl)phenylacetylene:[23] 1H NMR (300 MHz,
CDCl3): δ = 7.68–7.61 (m, 2 H, ArH), 7.59–7.54 (m, 2 H, ArH),
7.49–7.42 (m, 1 H, ArH), 7.39–7.32 (m, 4 H, ArH) ppm. MS: m/z
(%) = 246 (100) [M]+, 225 (19), 202 (15), 196 (9), 176 (10), 98 (12).
(4-Fluorophenyl)phenylacetylene:[24] 1H NMR (300 MHz, CDCl3): δ
= 7.54–7.49 (m, 4 H, ArH), 7.37–7.32 (m, 3 H, ArH), 7.08–7.02
(m, 2 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 162.6 (d, J
= 248.0 Hz), 133.5 (d, J = 8.7 Hz), 131.6, 128.3, 123.1, 119.5 (d, J
= 5.9 Hz), 115.8 (d, J = 22.8 Hz), 89.1, 88.2 ppm.
(2-Fluorophenyl)phenylacetylene:[25] 1H NMR (300 MHz, CDCl3): δ
= 7.58–7.49 (m, 3 H, ArH), 7.34–7.20 (m, 4 H, ArH), 7.12–7.01
(m, 2 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 162.7 (d, J
= 250.0 Hz), 133.5, 131.7, 129.9 (d, J = 7.9 Hz), 128.6, 128.4, 123.9
(d, J = 2.9 Hz), 122.9, 115.5 (d, J = 21.0 Hz), 111.9 (d, J =
15.7 Hz), 94.5, 82.8 ppm.
(4-Nitrophenyl)phenylacetylene:[26] 1H NMR (300 MHz, CDCl3): δ
= 8.21 (d, J = 8.82 Hz, 2 H, ArH), 7.66 (d, J = 8.70 Hz, 2 H, ArH),
7.58–7.54 (m, 2 H, ArH), 7.39–7.35 (m, 3 H, ArH) ppm. 13C NMR
(75 MHz, CDCl3): δ = 146.9, 132.1, 131.9, 130.1, 129.3, 128.6,
123.7, 122.0, 94.8, 87.7 ppm.
Conclusions
We developed a novel gold(I)-catalyzed Sonogashira
coupling reaction. The cross-coupling reactions of terminal
alkynes with aryl iodides and aryl bromides generate the
corresponding coupling products in good to excellent yields
under the present reaction conditions. Furthermore, aro-
matic terminal alkynes could also react with 2-iodoaniline
to form substituted indoles in excellent yields through a
coupling–cyclization reaction sequence under the present
reaction conditions.
Experimental Section
Representative Procedure for the Gold(I) Iodide Catalyzed Sonoga-
shira Reaction: Phenylacetylene (102 mg, 1.0 mmol), p-iodoanisole
(234 mg, 1.0 mmol), AuI (3.2 mg, 0.01 mmol), dppf (5.5 mg,
0.01 mmol) and K2CO3 (276 mg, 2.0 mmol) were added to a round-
bottomed flask containing toluene (2 mL). The reaction mixture
was stirred at 130 °C for 24 h. After completion of reaction, the
mixture was filtered and washed with diethyl ether (2ϫ5 mL). The
combined organic phase was dried with Na2SO4, filtered, and con-
centrated, and the residue was purified by flash chromatography
on silica gel to give 200 mg of (p-methoxyphenyl)phenylacetylene
(96% yield).
(3-Nitrophenyl)phenylacetylene:[27] 1H NMR (300 MHz, CDCl3): δ
= 8.34 (s, 1 H, ArH), 8.17 (d, J = 8.19 Hz, 1 H, ArH), 7.77 (d, J
= 7.86 Hz, 1 H, ArH), 7.55–7.49 (m, 3 H, ArH), 7.34–7.32 (m, 3
H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 148.4, 137.3,
131.9, 129.5, 129.1, 128.6, 126.5, 125.3, 122.9, 122.5, 92.1,
86.9 ppm.
Eur. J. Org. Chem. 2008, 5946–5951
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5949

P. Li, L. Wang, M. Wang, F. You
FULL PAPER
(4-Acetylphenyl)phenylacetylene:[25] 1H NMR (300 MHz, CDCl3): δ 1-Methylsulfonyl-2-phenylindole:[36] 1H NMR (300 MHz, CDCl3): δ
= 7.95 (d, J = 8.47 Hz, 2 H, ArH), 7.59 (d, J = 8.44 Hz, 2 H, ArH), = 8.12 (d, J = 7.84 Hz, 1 H, ArH), 7.52–7.61 (m, 3 H, ArH), 7.46–
7.58–7.54 (m, 2 H, ArH), 7.39–7.35 (m, 3 H, ArH), 2.57 (s, 3 H,
COCH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 197.3, 136.2,
131.9, 131.8, 128.9, 128.5, 128.3, 128.1, 122.7, 92.7, 88.8, 26.7 ppm.
1-Phenyl-1-decyne:[28] 1H NMR (300 MHz, CDCl3): δ = 7.44–7.39
(m, 2 H, ArH), 7.29–7.24 (m, 3 H, ArH), 2.39 [t, J = 6.99 Hz, 2
H, CH2(CH2)6CH3], 1.62–1.55 [m, 2 H, CH2CH2(CH2)5CH3],
1.47–1.29 [m, 10 H, CH2CH2(CH2)5CH3], 0.89 (t, J = 6.57 Hz, 3
H, CH2CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 131.7, 128.1,
127.5, 124.3, 90.1, 80.7, 31.9, 29.2, 29.1, 28.9, 28.8, 22.8, 19.4,
14.0 ppm.
1-Phenyl-1-octyne:[29] 1H NMR (300 MHz, CDCl3): δ = 7.41–7.36
(m, 2 H, ArH), 7.32–7.25 (m, 3 H, ArH), 2.41 [t, J = 6.97 Hz, 2
H, CH2(CH2)4CH3], 1.66–1.52 [m, 2 H, CH2CH2(CH2)3CH3],
1.53–1.29 [m, 6 H, CH2CH2(CH2)3CH3], 0.91 (t, J = 6.72 Hz, 3 H,
CH2CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 131.7, 128.1,
127.5, 124.2, 90.5, 80.7, 31.5, 28.9, 22.6, 19.4, 14.1 ppm.
(4-Bromophenyl)phenylacetylene:[24] 1H NMR (300 MHz, CDCl3):
δ = 7.55–7.45 (m, 4 H, ArH), 7.39–7.30 (m, 5 H, ArH) ppm. 13C
NMR (75 MHz, CDCl3): δ = 133.1, 131.7, 128.6, 128.4, 122.9,
122.6, 122.3, 90.5, 88.4 ppm.
(4-Chlorophenyl)phenylacetylene:[30] 1H NMR (300 MHz, CDCl3):
δ = 7.56–7.48 (m, 2 H, ArH), 7.48–7.42 (m, 2 H, ArH), 7.37–7.32
(m, 4 H, ArH), 7.32–7.29 (m, 1 H, ArH) ppm. 13C NMR (75 MHz,
CDCl3): δ = 134.6, 133.3, 132.1, 129.1, 128.9, 128.8, 123.5, 122.1,
90.6, 88.5 ppm.
4-(Phenylethynyl)-1,1Ј-biphenyl:[27] 1H NMR (300 MHz, CDCl3): δ
= 7.65–7.52 (m, 7 H, ArH), 7.49–7.45 (m, 2 H, ArH), 7.41–7.37
(m, 4 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 140.9, 140.4,
132.1, 131.6, 128.9, 128.4, 128.2, 127.7, 127.0, 123.1, 122.1, 90.0,
89.4 ppm.
2-(2-Phenylethynyl)pyridine:[31] 1H NMR (300 MHz, CDCl3): δ =
8.61 (dd, J = 5.10, 0.90 Hz, 1 H, PyH), 7.69–7.58 (m, 3 H, PyH),
7.53 (dd, J = 8.10, 0.90 Hz, 1 H, ArH), 7.39–7.35 (m, 3 H, ArH),
7.25–7.17 (m, 1 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ =
149.9, 143.1, 136.2, 131.9, 128.8, 128.3, 127.1, 122.6, 122.0, 89.2,
88.6 ppm.
7.40 (m, 3 H, ArH), 7.37 (td, J = 7.44, 1.53 Hz, 1 H, ArH), 7.34
(td, J = 7.41, 1.53 Hz, 1 H, ArH), 6.72 (s, 1 H, 3-indole-H), 2.74
(s, 3 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 141.9, 137.9,
131.9, 130.5, 130.1, 128.9, 127.6, 125.1, 124.7, 120.9, 115.9, 113.1,
39.8 ppm.
1-(p-Toluenesulfonyl)-2-phenylindole:[37] 1H NMR (300 MHz,
CDCl3): δ = 8.25 (d, J = 7.58 Hz, 1 H, ArH), 7.45–7.30 (m, 6 H,
ArH), 7.29–7.13 (m, 4 H, ArH), 6.98 (d, J = 8.13 Hz, 2 H, ArH),
6.47 (s, 1 H, 3-indole-H), 2.23 (s, 3 H, ArCH3) ppm. 13C NMR
(75 MHz, CDCl3): δ = 144.5, 142.3, 138.5, 138.1, 134.5, 130.8,
130.3, 129.3, 126.8, 124.5, 124.1, 120.7, 116.6, 113.1, 21.5 ppm.
2-(p-Fluorophenyl)indole:[38] 1H NMR (300 MHz, CDCl3): δ = 8.24
(br. s, 1 H, NH), 7.69–7.59 (m, 3 H, ArH), 7.45 (d, J = 8.31 Hz, 1
H, ArH), 7.25–7.10 (m, 4 H, ArH), 6.78 (s, 1 H, 3-indole-H) ppm.
13C NMR (75 MHz, CDCl3): δ = 152.5 (J = 250.3 Hz), 137.1,
136.9, 129.3, 128.8, 127.1 (J = 7.6 Hz), 122.6, 120.7, 120.3, 116.4
(J = 20.5 Hz), 111.1, 99.7 ppm.
2-(p-Chlorophenyl)indole:[39] 1H NMR (300 MHz, CDCl3): δ = 8.26
(br. s, 1 H, NH), 7.64 (d, J = 8.19 Hz, 2 H, ArH), 7.52 (d, J =
8.25 Hz, 2 H, ArH), 7.45–7.38 (m, 3 H, ArH), 7.26–7.10 (m, 2 H,
ArH), 6.79 (s, 1 H, 3-indole-H) ppm. MS: m/z = 227 [M]+.
2-Hexyl-1H-indole:[40] 1H NMR (300 MHz, CDCl3): δ = 7.84 (br.
s, 1 H, NH), 7.54 (d, J = 7.80 Hz, 1 H, ArH), 7.25 (d, J = 7.86 Hz,
1 H, ArH), 7.16–7.00 (m, 2 H, ArH), 6.25 (s, 1 H, 3-indole-H),
2.72 [t, J = 7.65 Hz, 2 H, CH2(CH2)4CH3], 1.69–1.59 [m, 2 H,
CH2CH2(CH2)3CH3], 1.45–1.32 [m, 6 H, CH2CH2(CH2)3CH3],
0.89 (t, J = 7.53 Hz, 3 H, CH2CH3) ppm. 13C NMR (75 MHz,
CDCl3): δ = 140.1, 136.2, 129.0, 121.3, 119.7, 119.5, 110.3, 99.8,
31.9, 29.5, 29.3, 28.8, 22.9, 14.4 ppm.
1-(2-Phenyl-1H-indol-1-yl)ethanone:[41] 1H NMR (300 MHz,
CDCl3): δ = 8.38 (d, J = 8.43 Hz, 1 H, ArH), 7.57 (d, J = 7.56 Hz,
1 H, ArH), 7.47–7.39 (m, 5 H, ArH), 7.33 (ddd, J = 8.40, 7.32,
1.38 Hz, 1 H, ArH), 7.21 (dt, J = 7.50, 1.20 Hz, 1 H, ArH), 6.52 (s,
1 H, 3-indole-H), 2.02 (s, 3 H, COCH3) ppm. 13C NMR (75 MHz,
CDCl3): δ = 171.5, 139.6, 137.6, 134.3, 129.0, 128.8, 128.5, 125.2,
123.7, 120.4, 116.0, 111.6, 27.9 ppm.
tert-Butyl 2-phenylindole-1-carboxylate:[42] 1H NMR (300 MHz,
CDCl3): δ = 8.25 (d, J = 8.40 Hz, 1 H, ArH), 7.58 (d, J = 7.41 Hz,
1 H, ArH), 7.44–7.35 (m, 6 H, ArH), 7.23 (m, 1 H, ArH), 6.51 (s,
1 H, 3-indole-H), 1.34 [s, 9 H, (CH3)3] ppm. 13C NMR (75 MHz,
CDCl3): δ = 150.1, 140.3, 137.5, 135.1, 129.0, 128.7, 127.9, 127.3,
124.5, 122.7, 120.2, 115.4, 109.7, 83.6, 27.8 ppm.
3-(2-Phenylethynyl)pyridine:[32] 1H NMR (300 MHz, CDCl3): δ =
8.75–8.71 (m, 1 H, ArH), 8.59–8.53 (m, 1 H, ArH), 7.79–7.72 (m,
1 H, ArH), 7.58–7.53 (m, 2 H, ArH), 7.39–7.33 (m, 3 H, ArH),
7.25–7.21 (m, 1 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ =
152.3, 148.5, 138.5, 131.7, 128.9, 128.4, 123.1, 122.6, 120.5, 92.8,
86.1 ppm.
(4-Cyanophenyl)phenylacetylene:[33] 1H NMR (300 MHz, CDCl3): δ
= 7.68–7.61 (m, 4 H, ArH), 7.58–7.55 (m, 2 H, ArH), 7.44–7.40
(m, 3 H, ArH) ppm. 13C NMR (75 MHz, CDCl3): δ = 132.0, 131.8,
129.1, 128.5, 128.2, 122.2, 118.5, 111.4, 93.7, 87.7 ppm.
2-Phenylindole:[34] 1H NMR (300 MHz, CDCl3): δ = 8.26 (br. s, 1
H, NH), 7.66–7.63 (m, 3 H, ArH), 7.44–7.27 (m, 4 H, ArH), 7.22–
7.10 (m, 2 H, ArH), 6.84 (s, 1 H, 3-indole-H) ppm. 13C NMR
(75 MHz, CDCl3): δ = 137.9, 136.9, 132.3, 129.2, 129.0, 127.8,
125.1, 122.4, 120.6, 120.3, 110.9, 100.1 ppm.
2-p-Tolylindole:[35] 1H NMR (300 MHz, CDCl3): δ = 8.28 (br. s, 1
H, NH), 7.63 (d, J = 7.64 Hz, 1 H, ArH), 7.56 (d, J = 8.04 Hz, 2
H, ArH), 7.36 (d, J = 7.91 Hz, 1 H, ArH), 7.25 (d, J = 7.91 Hz, 2
H, ArH), 7.18–7.09 (m, 2 H, ArH), 6.79 (s, 1 H, 3-indole-H), 2.38
(s, 3 H, ArCH3) ppm. 13C NMR (75 MHz, CDCl3): δ = 138.1,
137.6, 136.7, 129.7, 129.6, 129.3, 125.1, 122.1, 120.5, 120.2, 110.8,
99.4, 21.2 ppm.
Acknowledgments
We gratefully acknowledge financial support by the National Natu-
ral Science Foundation of China (20772043, 20572031).
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: August 4, 2008
Published Online: November 4, 2008
Eur. J. Org. Chem. 2008, 5946–5951
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5951