Application of recoverable nanosized palladium(0) catalyst in Sonogashira reaction

Article abstract of DOI:10.1016/j.tet.2005.07.013

In the absence of ligand, copper and amine, a recoverable nanoparticle palladium(0) catalyzed Sonogashira reaction of aryl iodides and bromides with terminal alkynes was developed. The protocol involved the use of an environmental-friendly reaction system with ethanol as the solvent, potassium carbonate as a base, and poly(vinylpyrrolidone) (PVP) supported nanosized palladium metal colloids as the catalyst. The palladium metal was recovered and recycled by a simple decantation of the reaction solution and used for eight consecutive trials without significant loss of its reactivity.

Full text of DOI:10.1016/j.tet.2005.07.013

Tetrahedron 61 (2005) 8633–8640
Application of recoverable nanosized palladium(0) catalyst in
Sonogashira reaction
a
Pinhua Li, Lei Wang
a,b,
a
*
and Hongji Li
a
Department of Chemistry, Huaibei Coal Teachers College, Huaibei, Anhui 235000, People’s Republic of China
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, People’s Republic of China
b
Received 18 March 2005; revised 1 July 2005; accepted 5 July 2005
Available online 26 July 2005
Abstract—In the absence of ligand, copper and amine, a recoverable nanoparticle palladium(0) catalyzed Sonogashira reaction of aryl
iodides and bromides with terminal alkynes was developed. The protocol involved the use of an environmental-friendly reaction system with
ethanol as the solvent, potassium carbonate as a base, and poly(vinylpyrrolidone) (PVP) supported nanosized palladium metal colloids as the
catalyst. The palladium metal was recovered and recycled by a simple decantation of the reaction solution and used for eight consecutive
trials without significant loss of its reactivity.
q 2005 Elsevier Ltd. All rights reserved.
1
. Introduction
tedious if not impossible, and might result in high palladium
contamination of the products. In addition, amines, such as
triethylamine and piperidine, required in most Sonogashira
reactions, have a bad smell and add to the environmental
burden.
The palladium complexes in the presence of a catalytic
amount of CuI and an amine (as a solvent or in large excess)
catalyzed coupling of terminal alkynes with aryl and alkenyl
halides (the Sonogashira reaction) is one of the most
powerful and straightforward methods for the formation of
A number of modifications, such as copper-free catalyst
2
1
10
systems, amine- and copper-free systems, ligand-free
11
sp –sp carbon–carbon bonds in organic synthesis. This
method has been widely used for the synthesis of natural
1
2
13
14
systems, palladium powder systems, nickel systems,
environmental-friendly reaction media (including
2
products, biologically active molecules, nonlinear optical
3
4
materials and molecular electronics, dendrimeric and
10n,15
13
solventless, and ionic liquid
10m,16
aqueous,
phase-transfer reaction conditions and hydrogen atmosphere
systems),
5
polymeric materials, macrocycles with acetylene links,
6
7
17
conditions, have been used to solve one or two of the
and polyalkynylated molecules. In general, the traditional
palladium-catalyzed reaction conditions are mild, and many
reactions can be accomplished at ambient temperature.
However, the Sonogashira reaction often generates homo-
coupling products of terminal alkynes (Glaser coupling or
above problems, but none of them can solve all of the
problems. Last year, a transition-metal free Sonogashira
coupling was developed by Leadbeater using PEG–NaOH
1
8
(aqueous) under microwave irradiation conditions, but
this approach was limited by the narrow choice of reactants
(only to aryl iodides and aromatic terminal alkynes). Most
recently, ligand-, copper- and amine-free Sonogashira
reactions in DMF (not an environmental benign solvent)
8
Hay coupling ) along with the main reaction in considerable
yields owing to the addition of CuI and these undesirable
by-products are generally not easy to be separated from the
desired products due to very similar chromatographic
mobility. Furthermore, the reaction generally proceeds in
the presence of a homogeneous more expensive palladium
complex catalyst, which makes the recovery of the metal
9
19
or in iso-propanol were demonstrated. Nevertheless, the
development of simpler, more practical, economic, and
efficient catalyst system is still an important topic in this
area.
Keywords: Nanoparticle palladium metal; Sonogashira reaction; Ligand
free; Copper free; Amine free.
Herein, we report a Sonogashira protocol only in the
presence of PVP-supported nanoparticle palladium metal,
potassium carbonate in ethanol (ligand-free, co-catalyst-
free, and amine-free in environmental-friendly solvent),
*
Corresponding author. Address: Department of Chemistry, Huaibei Coal
Teachers College, Huaibei, Anhui 235000, People’s Republic of China.
Tel.: C86 561 380 2069; fax: C86 561 309 0518;
e-mail: leiwang@hbcnc.edu.cn
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.07.013

8634
P. Li et al. / Tetrahedron 61 (2005) 8633–8640
Scheme 1.
which generates the corresponding coupling products in
excellent yields. It can solve some of the above problems in
the reaction. Moreover, the palladium metal can be
recovered and recycled by a simple decantation of the
reaction solution and used for eight consecutive trials
without significant loss of its reactivity (Scheme 1).
other hand, an atom-economical Pd/Ni bimetallic nano-
particles, a layered double hydroxide supported nano-
palladium, has been tested as the catalyst for the
1
2,21
Sonogashira reaction.
As stabilizers and supporting
materials, polyvinylpyrrolidone (PVP) and tetraalkyl-
ammonium salts can prevent undesired agglomeration by
forming a monomolecular layer around the palladium metal
2
2
core. We used Pd/PVP or Pd(OAc) /n-Bu NBr (Jeffery’s
2
4
2
. Results and discussion
23
catalyst), in place of Pd(OAc) to perform the model
2
Sonogashira reaction. We were delighted that the desired
products were obtained almost quantitatively (96% yield by
using Pd/PVP and 90% yield by using Pd(OAc) /n-Bu NBr,
2.1. Optimization of reaction conditions for Sonogashira
reaction
2
4
entries 5 and 6, Table 1). However, only trace of the cross-
coupling product was isolated when the reaction was carried
out in the presence of submicron palladium or palladium
sponge (entries 3 and 4, Table 1). The optimized loading of
nano-palladium particles on PVP was found to be in the
range of 0.5–5.0 mol% (entries 7–12, Table 1).
Although, P-ligands stabilize palladium and influence its
reactivity, the simplest and cheapest Pd-catalysts are of
course ligand-free systems, specifically when used in low
loading. Such an experimental protocol would constitute a
significant advancement, especially if generally applicable.
In our initial screening experiments, the Sonogashira
reaction catalyzed by palladium in the absence of copper,
ligand and amine was our goal. When we searched for a
cross-coupling protocol of iodobenzene and phenyl-
acetylene, we observed that iodobenzene could react with
During the course of our further optimization of the reaction
conditions, we examined several different bases for the
Sonogashira coupling reactions. K CO was found to be the
2
3
most effective one (entry 5, Table 2). Other bases such as
KOAc, KF, and K PO , were substantially less effective,
phenylacetylene in the presence of 3 mol% of Pd(OAc) and
2
3
4
2
equiv of K CO in ethanol under ligand-, copper- and
2 3
KOH failed to promote the reaction, and piperidine,
diethylamine, dibenzylamine, and triethylamine were no
longer the effective bases in this catalyst system (entries 1–4
and 6–9, Table 2). Because of the polar properties of PVP,
the reaction conducted in EtOH and MeOH were most
effective (entries 1 and 2, Table 3). The use of DMSO and
DMF as solvents led to slower reactions (entries 7 and 8,
Table 3), and no desired cross-coupling products were
observed while reactions were carried out in toluene,
dichloromethane, THF, and acetonitrile (entries 3–6,
Table 3). When 1 mol% loading of palladium was used,
the reactions were generally completed in a matter of hours
amine-free reaction conditions at reflux temperature for 6 h
to afford the desired cross-coupling product as the sole
product in 52% yield (no homo-coupling product, entry 1,
Table 1). Encouraged by this result, we continued to
improve the yield by using the most efficient palladium
source. In the last decade, Reetz et al. reported that
palladium metal colloids could be prepared size-selectively
in the range of 1–5 nm in organic solvents or in water by
reducing palladium salts chemically or electrochemically in
the presence of polymers (such as polyvinylpyrrolidone) or
surfactants (e.g., tetraalkyl ammonium salts) and sub-
2
0
sequently used for Heck and Suzuki reactions. On the
a
Table 1. Effect of palladium source on the Sonogashira coupling reaction
b
Yield (%)
Entry
Palladium source/amount
1
2
3
4
5
6
7
8
9
1
1
1
Pd(OAc)
2
(3mol%)
(3 mol%)
52
48
Trace
0
96
90
93
94
95
Pd(PPh
3
)
4
Palladium powder (submicron) (5 mol%)
Palladium sponge (5 mol%)
Palladium colloids (nanosize) on PVP (3 mol%)
Pd(OAc)
2
(3 mol%)/n-Bu
4
NBr (1.0 mol)
Palladium colloids (nanosize) on PVP (5 mol%)
Palladium colloids (nanosize) on PVP (4 mol%)
Palladium colloids (nanosize) on PVP (2 mol%)
Palladium colloids (nanosize) on PVP (1 mol%)
Palladium colloids (nanosize) on PVP (0.75 mol%)
Palladium colloids (nanosize) on PVP (0.5 mol%)
0
1
2
95
92
c
90
a
b
c
2 3
Phenylacetylene (1.00 mmol), iodobenzene (1.00 mmol), Palladium, K CO (2.00 mmol) in EtOH (4 mL) at 80 8C stirring for 6 h.
Isolated yields.
The reaction was performed for 10 h.

P. Li et al. / Tetrahedron 61 (2005) 8633–8640
8635
a
Table 2. Effect of base on the Sonogashira coupling reaction
b
Yield (%)
Entry
Base
1
2
3
4
5
6
7
8
9
Piperidine
40
42
54
79
K
3
PO
KF
KOAc
CO
4
K
2
3
95
KOH
Trace
38
27
Triethylamine
Diethylamine
Dibenzylamine
21
a
Phenylacetylene (1.00 mmol), iodobenzene (1.00 mmol), Pd(0) colloids (7 nm diameter size, 1.06 mg, 0.01 mmol, on PVP), base (2.00 mmol) in EtOH
4 mL) at 80 8C stirring for 6 h.
Isolated yields.
(
b
a
Table 3. Effect of solvent on the Sonogashira coupling reaction
b
Yield (%)
Entry
Solvent
CH OH
1
2
3
4
5
6
7
8
3
95
95
0
0
0
Trace
90
90
CH CH OH
CH
THF
CH Cl
CH CN
3
2
C
6
H
5
3
2
2
3
DMSO
DMF
a
Phenylacetylene (1.00 mmol), iodobenzene (1.00 mmol), Pd(0) colloids (7 nm diameter size, 1.06 mg, 0.01 mmol, on PVP), K
4 mL) at 80 8C stirring for 6 h.
Isolated yields.
2
CO
3
(2.00 mmol) in EtOH
(
b
a
Table 4. Nanoparticle palladium metal catalyzed Sonogashira coupling reaction
b
Yield (%)
Entry
Organic halide
Terminal alkyne
1
2
C
p-CH
6
H
OC
5
I
C
C
6
H
H
5
C^CH
C^CH
95
92
3
6
H
4
I
6
5
c
9
0
3
4
5
6
7
8
9
p-CH
3
C
6
H
4
I
C
C
C
C
C
C
C
6
6
6
6
6
6
6
H
H
H
H
H
H
H
5
5
5
5
5
5
5
C^CH
C^CH
C^CH
C^CH
C^CH
C^CH
C^CH
94
98
93
91
96
90
83
92
94
91
93
92
90
92
94
80
86
78
82
43
p-CH
3
COC
NC
NC
p-CF
m-CNC
o-CF
6
H
4
I
p-O
2
6 4
H I
H I
6 4
m-O
2
3
C
6
H
4
I
I
I
6
6
H
H
4
3
C
4
10
11
12
13
14
15
16
17
18
19
20
21
22
C
C
C
C
C
C
6
H
H
H
H
H
H
5
I
p-BrC
p-FC
p-CH
p-C
6
H
4
C^CH
C^CH
C^CH
C^CH
17C^CH
6
6
6
6
6
5
5
5
5
5
I
I
I
I
I
6 4
H
3
C
6
H
4
6
H
5
C
6
H
4
n-C
n-C
n-C
n-C
8
6
8
8
H
H
H
H
13C^CH
17C^CH
17C^CH
3 6 4
p-CH OC H I
3 6 4
p-CH C H I
p-CNC
m-O NC
p-CH COC
6
H
4
Br
C
C
C
C
C
6
H
5
C^CH
C^CH
C^CH
C^CH
C^CH
2
6
H
4
Br
6
6
6
6
H
H
H
H
5
5
5
5
3
6
H
4
Br
2-Bromopyridine
p-CH Br
3 6 4
C H
d
9
4
a
Terminal alkyne (1.00 mmol), organic halide (1.00 mmol), Pd(0) colloids (7 nm diameter size, 1.06 mg, 0.01 mmol, on PVP), K
4 mL) at 80 8C stirring for 6 h.
Isolated yields.
2 3
CO (2.00 mmol) in EtOH
(
b
c
d
Up to 10 mmol scales.
In the presence of PPh
3
.

8636
P. Li et al. / Tetrahedron 61 (2005) 8633–8640
a
Table 5. Successive trials by using recoverable nanosized palladium on PVP
b
Yield (%)
b
Yield (%)
Trial
Trial
1
2
3
4
95
94
92
93
5
6
7
8
92
91
90
90
a
Phenylacetylene (1.00 mmol), iodobenzene (1.00 mmol), Pd(0) colloids (7 nm diameter size, 1.06 mg, 0.01 mmol, on PVP), K
4 mL) at 80 8C stirring for 6 h.
Isolated yields.
2 3
CO (2.00 mmol) in EtOH
(
b
but the time, as expected, was inversely proportional to the
temperature. A reaction temperature of 80 8C was found to
be optimal. Thus, the optimized reaction conditions for this
Sonogashira reaction were Pd/PVP (1 mol%), K CO
conditions (entries 1–8, Table 4). This cross-coupling was
also tolerant of ortho substitution in aryl iodides and led to
good yields (entry 9, Table 4). Regardless of their electronic
characters, both of the aromatic terminal alkynes and
aliphatic terminal alkynes component coupled smoothly
with iodobenzene to produce the desired products in
excellent yields (entries 10–17, Table 4). Activated aryl
bromide reacted with phenylacetylene to generate the
corresponding products in good yields (entries 18–21,
Table 4). For electron-rich aryl bromide, relatively lower
yield was obtained under the present reaction conditions
(entry 22, Table 4). When the simplest and cheapest
2
3
(
2 equiv) in ethanol under reflux temperature for 6 h.
2.2. The Sonogashira coupling reaction of aryl halides
with terminal alkynes
To survey the generality of this Sonogashira-type reaction,
we investigated the reaction using a variety of aryl iodides
and bromides, with a wide range of terminal alkynes as
substrates under the optimized conditions. The results are
shown in Table 4. The electron-neutral, electron-rich and
electron-poor aryl iodides reacted with phenylacetylene
very well to generate the corresponding cross-coupling
products in excellent yields under the standard reaction
P-ligand PPh
was added to the reaction mixture, an
3
excellent yield of the product was isolated (entry 22,
Table 4). Further investigation of ligands to the coupling
reactions is currently underway and will be reported in due
course.
Figure 1. The simple decantation procedure for recycling palladium metal collide on PVP in solution.

P. Li et al. / Tetrahedron 61 (2005) 8633–8640
8637
2
PVP
.3. The recyclable of the nanoparticle palladium(0) on
recorded at 300 or 250 MHz, and 75 or 62.5 MHz,
respectively. Chemical shifts were given as d value with
reference to tetramethylsilane (TMS) as the internal
standard. GC/MS data were obtained by using a Hewlett-
Packard 6890 series GC equipped with a 5983 mass
selective detector. The chemicals were purchased from
commercial suppliers and were used without further
purification. Products were purified by flash column
chromatography.
The recyclable of the palladium on PVP was also surveyed.
After carrying out the reaction, Et O was added to the
reaction mixture. The product was extracted into organic
layer, Pd–PVP, and other inorganics precipitated and
agglomerated to the bottom of the flask. After decantation
of the reaction solution, additional K CO was added to the
2
2
3
palladium on PVP and the reaction was repeated. Only
minor decreases in reaction yields were observed after eight
repetitive cycles (Table 5). The simple decantation
procedure for recycling palladium metal collide on PVP in
solution is stated in Figure 1. Alternatively, the product
might be distilled directly from the reaction mixture.
Palladium, PVP and other inorganics were left at the bottom
of flask, and they could be reused directly without
purification.
4.2. Preparation of palladium metal colloids on PVP
2
2
According to the literature, palladium acetate (50 mg) was
added to a solution of PVP (MW 40,000, 2.5 g) in methanol
(150 mL) and the mixture was refluxed under nitrogen for
3 h. The resulting brown liquid was filtered through 0.2 mm
Teflon Millipore, and methanol was removed under reduced
pressure. This procedure reproducibly yielded colloidal
palladium particles in the form of well-formed micro-
crystallites with a mean diameter of 7 nm (Fig. 2).
3. Conclusion
4.3. General procedure for the Sonogashira reaction
using Pd(OAc) /n-Bu NBr (Jeffery’s catalyst)
In conclusion, we have developed an efficient, simple,
practical, and economic catalyst system for the Sonogashira
reaction using PVP supported nanosized palladium metal
2
4
Under nitrogen atmosphere, an oven-dried round-bottomed
flask was charged with Pd(OAc)2 (6.7 mg, 0.03 mmol),
(
1 mol% loading) in ethanol under ligand-, copper-, and
amine-free reaction conditions. Furthermore, palladium on
PVP can be recycled at least eight times without loss of
activity via a simple decantation procedure. In addition, the
protocol uses environmentally benign reagents and solvents.
n-Bu NBr (322 mg, 1.0 mmol), K CO
3
(272 mg,
4
2
2.0 mmol), aryl halide (1.0 mmol), terminal alkyne
(1.0 mmol), and ethanol (4 mL). The reaction mixture was
refluxed at 80 8C for 6 h. After cooling to the room
temperature, Et O (25 mL) was added. The organic layer
2
was successively washed with water (2!10 mL) and brine
(10 mL) and dried over Na SO . The solution was filtered,
4
. Experimental
2
4
concentrated, and the residue was purified by flash
chromatography on silica gel to give the desired cross-
coupling product.
4
.1. General
Melting points were recorded on a melting point apparatus
and were uncorrected. All H and C NMR spectra were
1
13
4.4. General procedure for recycling of palladium metal
on PVP
After carrying out a reaction, Et O (10 mL) was added to the
2
reaction mixture. The product was extracted into organic
layer, Pd–PVP and other inorganics precipitated and
agglomerated to the bottom of the flask. After decantation
of the reaction solution, additional K CO (136 mg,
2
3
1.0 mmol) was added to the palladium on PVP and the
reaction was repeated following the general procedure for
the Sonogashira reaction using Pd/PVP as described below.
4.5. General procedure for the Sonogashira reaction
using Pd/PVP
Under nitrogen atmosphere, an oven-dried round-bottomed
flask was charged with Pd/PVP (0.106 g of 1% Pd on PVP,
containing 1.06 mg Pd), K CO (272 mg, 2.0 mmol), aryl
2
3
halide (1.0 mmol), terminal alkyne (1.0 mmol), and ethanol
4 mL). The reaction mixture was refluxed at 80 8C for 6 h.
After cooling to the room temperature, Et O (10 mL) was
(
2
added and stirred for 10 min to ensure product removal from
Pd/PVP. As Pd/PVP and other inorganics precipitated and
agglomerated to the bottom of the flask, the organic layer
was decanted and the residue was washed using Et O (2!
2
5 mL). The combined organic layers were dried over
Figure 2. TEM of palladium metal colloids on PVP (Measured by Philips
Tecnai 200).

8638
P. Li et al. / Tetrahedron 61 (2005) 8633–8640
Na SO , filtered, concentrated, and the residue was purified
2
by flash chromatography on silica gel to give the desired
cross-coupling product.
29.2, 29.1, 28.9, 28.8, 22.7, 19.4, 14.1; MS m/z (relative
intensity, %): 214 (M , 13), 171 (3), 157 (17), 143 (60), 129
(66), 115 (100), 91 (41).
4
C
2
.5.1. Diphenylacetylene. Mp 60–61 8C (lit. 60–62 8C).
4
31 1
4.5.9. 1-Phenyl-1-octyne. Oil. H NMR (CDCl3,
250 MHz) d: 7.40–7.37 (m, 2H), 7.30–7.23 (m, 3H), 2.39
4
1
H NMR (CDCl , 250 MHz) d: 7.54–7.50 (m, 4H), 7.32–
3
1
.28 (m, 6H); C NMR (CDCl , 62.5 MHz) d: 131.6, 128.3,
3
7
1
1
(t, JZ6.97 Hz, 2H), 1.65–1.54 (m, 2H), 1.50–1.26 (m, 6H),
3
C
28.2, 123.3, 89.4; MS m/z (relative intensity, %): 178 (M ,
00), 152 (14), 126 (7), 89 (13).
13
0.90 (t, JZ6.68 Hz, 3H); C NMR (CDCl , 62.5 MHz) d:
3
131.5, 128.1, 127.4, 124.2, 90.4, 80.6, 31.4, 28.7, 22.6, 19.4,
1
(15), 143 (55), 129 (54), 115 (100), 91 (31).
C
4.0; MS m/z (relative intensity, %): 186 (M , 26), 157
2
.5.2. Phenyl-p-tolyacetylene. Mp 71–72.5 8C (lit. 72–
5
4
7
7
7
1
2
1
3 8C). H NMR (CDCl , 250 MHz) d: 7.52–7.48 (m, 2H),
3
3
2 1
.41 (d, JZ7.80 Hz, 2H), 7.29–7.26 (m, 3H), 7.10 (d, JZ
4.5.10. 1-(4-Methoxylphenyl)-1-decyne. Oil.
H NMR
1
.81 Hz, 2H), 2.30 (s, 3H); C NMR (CDCl , 62.5 MHz) d:
3
(CDCl , 250 MHz) d: 7.32 (d, JZ8.72 Hz, 2H), 6.80 (d, JZ
3
3
38.3, 131.5, 129.0, 128.2, 128.0, 123.4, 120.2, 89.6, 88.7,
1.4; MS m/z (relative intensity, %): 192 (M , 100), 165
8.73 Hz, 2H), 3.78 (s, 3H), 2.37 (t, JZ7.00 Hz, 2H), 1.64–
1.54 (m, 2H), 1.46–1.28 (m, 10H), 0.88 (t, JZ6.00 Hz, 3H);
C
1
3
(
15), 139 (4), 115 (6), 94 (10).
C NMR (CDCl , 62.5 MHz) d: 159.0, 132.8, 116.3, 113.8,
3
88.7, 80.2, 55.2, 31.8, 29.2, 29.1, 28.9, 22.2, 19.4, 14.1; MS
m/z (relative intensity, %): 244 (M , 19), 201 (4), 188 (23),
173 (30), 159 (25), 147 (100), 121 (33), 115 (21), 91 (15).
C
4
(
.5.3. (4-Acetylphenyl)phenylacetylene. Mp 95–96 8C
lit. 94–96 8C). H NMR (CDCl , 250 MHz) d: 7.91 (d,
2
6
1
3
JZ8.41 Hz, 2H), 7.58 (d, JZ8.41 Hz, 2H), 7.54–7.52 (m,
1
H), 7.36–7.33 (m, 3H), 2.57 (s, 3H); C NMR (CDCl3,
3
32 1
2
6
1
4.5.11. 1-(4-Methylphenyl)-1-decyne. Oil.
H NMR
2.5 MHz) d: 197.1, 136.1, 131.7, 131.6, 128.7, 128.4,
28.2, 128.1, 122.6, 92.6, 88.6, 26.5; MS m/z (relative
(CDCl , 250 MHz) d: 7.27 (d, JZ8.00 Hz, 2H), 7.04 (d,
3
JZ7.93 Hz, 2H), 2.38 (t, JZ7.56 Hz, 2H), 2.29 (s, 3H),
1.63–1.52 (m, 2H), 1.45–1.28 (m, 10H), 0.88 (t, JZ6.46 Hz,
C
intensity, %): 220 (M , 60), 205 (100), 176 (48), 151 (18),
1
1
3H); C NMR (CDCl , 62.5 MHz) d: 137.2, 131.4, 128.8,
3
02 (10), 88 (19).
3
1
21.1, 89.5, 80.6, 31.9, 29.2, 29.1, 28.9, 28.8, 22.7, 21.3,
C
4
.5.4. (4-Nitrophenyl)phenylacetylene. Mp 120–122 8C
19.4, 14.0; MS m/z (relative intensity, %): 228 (M , 16),
185 (4), 171 (13), 157 (36), 143 (32), 131 (100), 115 (24), 91
(11).
2
7
1
(
lit. 120–121 8C). H NMR (CDCl , 250 MHz) d: 8.19 (d,
3
JZ8.83 Hz, 2H), 7.64 (d, JZ8.73 Hz, 2H), 7.56–7.52 (m,
1
H), 7.39–7.37 (m, 3H); C NMR (CDCl , 62.5 MHz) d:
3
2
1
8
3
46.9, 132.2, 131.8, 130.2, 129.2, 128.5, 123.6, 122.0, 94.7,
7.5; MS m/z (relative intensity, %): 223 (M , 100), 193
4.5.12. (4-Methoxyphenyl)phenylacetylene. Mp 58–60 8C
(lit. 57–61 8C). H NMR (CDCl , 300 MHz) d: 7.53–7.46
C
33
1
3
(
40), 176 (80), 165 (33), 151 (40), 139 (8), 126 (14).
(m, 4H), 7.37–7.30 (m, 3H), 6.87 (dd, JZ8.70, 2.10 Hz,
1
H), 3.82 (s, 3H); C NMR (CDCl , 75 MHz) d: 159.5,
3
2
133.0, 131.4, 128.3, 127.9, 123.5, 115.3, 113.9, 89.3, 88.0,
3
4
(
.5.5. (3-Nitrophenyl)phenylacetylene. Mp 67–69 8C
lit. 68–70 8C). H NMR (CDCl , 300 MHz) d: 8.31 (s,
2
8
1
C
55.3; MS m/z (relative intensity, %): 208 (M , 100), 193
(48), 165 (39), 139 (8).
3
1
7
7
1
H), 8.11 (d, JZ8.10 Hz, 1H), 7.76 (d, JZ7.80 Hz, 1H),
1
.51–7.47 (m, 3H), 7.31–7.35 (m, 3H); C NMR (CDCl3,
3
5 MHz) d: 148.3, 137.2, 131.8, 129.3, 129.0, 128.5, 126.4,
25.2, 122.8, 122.3, 92.0, 86.9; MS m/z (relative intensity,
4.5.13. (4-Trifluoromethylphenyl)phenylacetylene. Mp
3
4
1
104–106 8C). H NMR (CDCl3,
103–105 8C (lit.
300 MHz) d: 7.63–7.60 (m, 4H), 7.57–7.54 (m, 2H), 7.39–
7
C
): 223 (M , 100).
%
1
3
.35 (m, 3H); C NMR (CDCl , 75 MHz) d: 131.8, 131.7,
3
4
(
.5.6. (4-Fluorophenyl)phenylacetylene. Mp 108–110 8C
lit. 108–109 8C). H NMR (CDCl , 250 MHz) d: 7.53–
129.9 (JZ32.8 Hz), 128.8, 128.4, 127.1 (JZ1.2 Hz), 125.3
(JZ3.7 Hz), 123.9 (JZ270.7 Hz), 122.5, 91.7, 87.9; MS
m/z (relative intensity, %): 246 (M , 100), 227 (9), 196 (8),
2
9
1
3
1
3
C
7
.47 (m, 4H), 7.35–7.31 (m, 3H), 7.06–7.00 (m, 2H);
C
NMR (CDCl , 62.5 MHz) d: 162.5 (d, JZ248.1 Hz), 133.5
176 (10), 98 (8).
3
(
1
d, JZ8.9 Hz), 131.5, 128.3, 123.1, 119.3 (d, JZ5.6 Hz),
15.6 (d, JZ22.4 Hz), 89.0, 88.3; MS m/z (relative
intensity, %): 196 (M , 100), 175 (7), 144 (5), 98 (15).
0
4.5.14. 4-(Phenylethynyl)-1,1 -biphenyl. Mp 163–164 8C
C
28
1
(lit. 162–163 8C). H NMR (CDCl , 300 MHz) d: 7.63–
3
13
.54 (m, 7H), 7.48–7.43 (m, 2H), 7.38–7.34 (m, 4H);
7
C
4
(
7
6
1
.5.7. (4-Bromophenyl)phenylacetylene. Mp 82–84 8C
lit. 82–84 8C). H NMR (CDCl , 250 MHz) d: 7.53–
NMR (CDCl , 75 MHz) d: 140.9, 140.3, 132.0, 131.6,
3
2
9
1
128.8, 128.34, 128.25, 127.6, 127.0, 123.2, 122.1, 90.0,
89.3; MS m/z (relative intensity, %): 254 (M , 100), 255
(23), 252 (26), 127 (9).
3
1
.44 (m, 4H), 7.38–7.31 (m, 5H); C NMR (CDCl3,
3
C
2.5 MHz) d: 133.0, 131.6, 128.5, 128.4, 122.9, 122.5,
22.2, 90.5, 88.3; MS m/z (relative intensity, %): 258, 256
C
(
M , 97, 100), 176 (88), 151 (37), 128 (17), 88 (61).
4.5.15. (4-Cyanophenyl)phenylacetylene. Mp 109–110 8C
3
lit. 108.5–109.5 8C). H NMR (CDCl , 300 MHz) d:
5
1
(
7.65–7.59 (m, 4H), 7.56–7.53 (m, 2H), 7.40–7.37 (m, 3H);
3
3
0 1
4
2
.5.8. 1-Phenyl-1-decyne. Oil.
50 MHz) d: 7.40–7.36 (m, 2H), 7.28–7.22 (m, 3H), 2.38
H NMR (CDCl3,
1
3
C NMR (CDCl , 75 MHz) d: 132.0 (2C), 131.8, 129.1,
3
(
1
6
t, JZ6.96 Hz, 2H), 1.64–1.53 (m, 2H), 1.45–1.28 (m,
0H), 0.88 (t, JZ6.54 Hz, 3H); C NMR (CDCl3,
2.5 MHz) d: 131.5, 128.1, 127.3, 124.2, 90.3, 80.6, 31.9,
128.5, 128.2, 122.2, 118.5, 111.4, 93.7, 87.7; MS m/z
(relative intensity, %): 203 (M , 100), 176 (8), 151 (5), 75
(5).
1
3
C

P. Li et al. / Tetrahedron 61 (2005) 8633–8640
8639
4
.5.16. (3-Cyanophenyl)phenylacetylene. Mp 69–71 8C
M. J. Org. Chem. 2000, 65, 7110–7113. (c) Ioshimura, F.;
Kawata, S.; Hirama, M. Tetrahedron Lett. 1999, 40,
8281–8285. (d) Nicolaou, K. C.; Dai, W.-M. Angew. Chem.,
Int. Ed. Engl. 1991, 30, 1387–1416.
3
5
1
(
lit. 70–71 8C). H NMR (CDCl , 300 MHz) d: 7.79 (t, JZ
3
1
7
1
1
1
.50 Hz, 1H), 7.73 (dt, JZ7.80, 1.50 Hz, 1H), 7.59 (dt, JZ
.80, 1.50 Hz, 1H), 7.55–7.52 (m, 2H), 7.45 (t, JZ7.80 Hz,
1
H), 7.39–7.36 (m, 3H); C NMR (CDCl , 75 MHz) d:
3
3. (a) Cosford, N. D. P.; Tehrani, L.; Roppe, J.; Schweiger, E.;
Smith, N. D.; Anderson, J.; Bristow, L.; Brodkin, J.; Jiang, X.;
McDonald, I.; Rao, S.; Washburn, M.; Varney, M. A. J. Med.
Chem. 2003, 46, 204–206. (b) Taylor, E. C.; Dowling, J. E.
J. Org. Chem. 1997, 62, 1599–1603. (c) Nakamura, H.;
Aizawa, M.; Takeuchi, D.; Murai, A.; Shimoura, O.
Tetrahedron Lett. 2000, 41, 2185–2188. (d) Amiet, G.;
H u¨ gel, H. M.; Nurlawis, F. Synlett 2002, 495–497. (e) Liu,
T.-Z.; Isobe, M. Synlett 2000, 266–268. (f) Kort, M.; Correa,
V.; Valentijin, A. R. P. M.; Marel, G. A.; Potter, B. V. L.;
Taylor, C. W.; Boom, J. H. J. Med. Chem. 2000, 43,
3
35.6, 134.8, 131.7, 131.3, 129.2, 128.9, 128.4, 124.8,
22.2, 118.0, 112.8, 91.7, 86.8; MS m/z (relative intensity,
C
): 203 (M , 100), 176 (7), 151 (5), 75 (5).
%
3
6
4
.5.17. (2-Trifluoromethylphenyl)phenylacetylene. Oil.
H NMR (CDCl , 300 MHz) d: 7.67–7.62 (m, 2H), 7.57–
1
3
7
m/z (relative intensity, %): 246 (M , 100), 225 (17), 202
.53 (m, 2H), 7.49–7.44 (m, 1H), 7.39–7.33 (m, 4H); MS
C
(
12), 196 (8), 176 (5), 98 (4). Anal. Calcd for C H F : C,
15 9 3
7
3.22; H, 3.68. Found: C, 73.12; H, 3.77.
3
295–3303.
3
7
1
4. (a) Nalwa, H. S.; Miyata, S. Nonlinear Optics of Organic
Molecules and Polymers; CRC: Boca Raton, FL, 1997. (b)
Mongin, O.; Porres, L.; Moreaux, L.; Merta, J.; Blanchard-
Desce, M. Org. Lett. 2002, 4, 719–722. (c) Brunsveld, L.;
Meijer, E. W.; Prince, R. B.; Moore, J. S. J. Am. Chem. Soc.
4
(
7
7
7
1
.5.18. 2-(2-Phenylethynyl)pyridine. Oil.
H NMR
CDCl , 300 MHz) d: 8.60 (dd, JZ5.10, 0.90 Hz, 1H),
3
.68–7.59 (m, 3H), 7.51 (dd, JZ8.10, 0.90 Hz, 1H), 7.37–
13
.33 (m, 3H), 7.23–7.19 (m, 1H); C NMR (CDCl3,
5 MHz) d: 149.9, 143.2, 136.0, 131.9, 128.8, 128.2, 127.0,
22.6, 122.0, 89.1, 88.4; MS m/z (relative intensity, %): 179
M , 100), 180 (17), 178 (40), 151 (13), 126 (8), 76 (9).
2
Gonzalez, F. Synlett 2001, 1699–1702. (e) Sonoda, M.;
001, 123, 7978–7984. (d) P e´ rez-Balderas, F.; Santoyo-
C
´
(
Inaba, A.; Itahashi, K.; Tobe, Y. Org. Lett. 2001, 3, 2419–
2
421. (f) Wong, K.-T.; Hsu, C. C. Org. Lett. 2001, 3, 173–175.
g) Torruellas, W. E.; Neher, D.; Zanoni, R.; Stegeman, G. I.;
(
Acknowledgements
Kajzar, F.; Leclerc, M. Chem. Phys. Lett. 1990, 175, 11–16. (h)
Lee, C.-H.; Yamamoto, T. Tetrahedron Lett. 2001, 42, 3993–
We gratefully acknowledge financial support by the
National Natural Science Foundation of China (No.
0372024), the Excellent Scientist Foundation of Anhui
Province, China (No. 04046080), the Natural Science
Foundation of the Education Department of Anhui
Province, China (No. 2002kj254zd), the Scientific Research
Foundation for the Returned Overseas Chinese Scholars,
State Education Ministry, China (No. 2002247), the
Excellent Young Teachers Program of MOE, China (No.
3
996. (i) Matsumi, N.; Naka, K.; Chujo, Y. J. Am. Chem. Soc.
998, 120, 5112–5113. (j) Martin, R. E.; Diederich, F. Angew.
1
2
Chem., Int. Ed. 1999, 38, 1350–1377. (k) Inouye, M.;
Takahashi, K.; Nakazumi, H. J. Am. Chem. Soc. 1999, 121,
3
41–345.
5
. (a) Wegner, G.; M u¨ llen, K. Electronic Materials—the
Oligomer Approach; Wiley-VCH: Weinheim, 1998. (b) Li,
J.; Ambroise, A.; Yang, S. I.; Diers, J. R.; Seth, J.; Wack, C. R.;
Bocian, D. F.; Holten, D.; Lindsey, J. S. J. Am. Chem. Soc.
2024), and the Key Project of Science and Technology of
State Education Ministry, China (No. 0204069).
1
999, 121, 8927–8940. (c) Solomin, V. A.; Heitz, W.
Macromol. Chem. Phys. 1994, 195, 303–314. (d) Strachan,
J.-P.; Gentemann, S.; Seth, J.; Kalsbeck, W. A.; Lindsey, J. S.;
Holten, D.; Bocian, D. F. Inorg. Chem. 1998, 37, 1191–1201.
(
e) Wagner, R. W.; Seth, J.; Yang, S. I.; Kim, D.; Bocian,
D. F.; Holten, D.; Lindsey, J. S. J. Org. Chem. 1998, 63, 5042–
049.
References and notes
5
1
. (a) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
975, 16, 4467–4470. (b) Burnagin, N. A.; Sukhomlinova,
6. (a) H o¨ ger, S.; Rosselli, S.; Ramminger, A.-D.; Enkelmann, V.
Org. Lett. 2002, 4, 4269–4272. (b) Li, C.-J.; Slaven, W. T., IV;
John, V. T.; Banerjee, S. Chem. Commun. 1997, 1569–1570.
7. (a) Mongin, O.; Papamicael, C.; Hoyler, N.; Gossauer, A.
J. Org. Chem. 1998, 63, 5568–5580. (b) Tobe, Y.; Utsumi, N.;
Nagano, A.; Naemura, K. Angew. Chem., Int. Ed. 1998, 37,
1285–1287. (c) Onitsuka, K.; Fujimoto, M.; Ohshiro, N.;
Takahashi, S. Angew. Chem., Int. Ed. 1999, 38, 689–692.
8. (a) Glaser, C. Ber. Dtsch. Chem. Ges. 1869, 2, 422–424. (b)
Glaser, C. Ann. Chem. Pharm. 1870, 154, 137–171. (c) Hay,
A. S. J. Org. Chem. 1962, 27, 3320–3321. (d) Rossi, R.;
Carpita, A.; Bigelli, C. Tetrahedron Lett. 1985, 26, 523–526.
(e) Liu, Q.; Burton, D. J. Tetrahedron Lett. 1997, 38,
4371–4374. (f) For a review of acetylenic coupling, see:
Siemsen, P.; Livingston, R. C.; Diederich, F. Angew. Chem.,
Int. Ed. 2000, 39, 2632–2657.
1
L. I.; Luzikova, E. V.; Tolstaya, T. P.; Beletskaya, I. P.
Tetrahedron Lett. 1996, 37, 897–900. (c) Hundertmark, T.;
Littke, A. F.; Buchwald, S. L.; Fu, G. C. Org. Lett. 2000, 2,
1
729–1731. (d) Erdelyi, M.; Gogoll, A. J. Org. Chem. 2001,
6, 4165–4169. For selected reviews on Sonogashira reaction,
6
see: (e) Sonogashira, K. In Trost, B. M., Fleming, I., Eds.;
Comprehensive Organic Synthesis; Pergamon: Oxford, 1991;
Vol. 3, pp 521–549. (f) Sonogashira, K. In Metal-Catalyzed
Cross-Coupling Reactions; Diederich, F., Stang, P. J., Eds.;
Wiley-VCH: Weinheim, 1998; pp 203–229. (g) Sonogashira,
K. In Handbook of Organopalladium Chemistry for Organic
Synthesis; Negishi, E., Meijere, A., Eds.; Wiley-VCH: New
York, 2002. (h) Sonogashira, K. J. Organomet. Chem. 2002,
6
53, 46–49. (i) Negishi, E.; Anastasia, L. Chem. Rev. 2003,
03, 1979–2018 and references cited therein.
1
9. (a) Ziener, U.; Godt, A. J. Org. Chem. 1997, 62, 6137–6143.
(b) Kukula, H.; Veit, S.; Godt, A. Eur. J. Org. Chem. 1999,
277–286.
2
. (a) Paterson, I.; Davies, R. D. M.; Marquez, R. Angew. Chem.,
Int. Ed. 2001, 40, 603–607. (b) Toyota, M.; Komori, C.; Ihara,

8640
P. Li et al. / Tetrahedron 61 (2005) 8633–8640
1
0. (a) Leadbeater, N. E.; Tominack, B. J. Tetrahedron Lett. 2003,
4, 8653–8656. (b) Soheili, A.; Albaneze-Walker, J.; Murry,
J. A.; Dormer, P. G.; Hughes, D. L. Org. Lett. 2003, 5,
191–4194. (c) Heuz e´ , K.; M e´ ry, D.; Gauss, D.; Astruc, D.
20. Son, S. U.; Jang, Y.; Park, J.; Na, H. B.; Park, H. M.; Yun,
4
H. J.; Lee, J.; Hyeon, T. J. Am. Chem. Soc. 2004, 126,
5026–5027.
4
21. (a) Reetz, M. T.; Helbig, W.; Quaiser, S. A.; Stimming, U.;
Breuer, N.; Vogel, R. Science 1995, 267, 367–369. (b) Reetz,
M. T.; Winter, M.; Breinbauer, R.; Thurn-Albrecht, T.; Vogel,
W. Chem. Eur. J. 2001, 7, 1084–1094. (c) Reetz, M. T.;
Maase, M. Adv. Mater. 1999, 11, 773–777. (d) Reetz, M. T.;
Westermann, E. Angew. Chem., Int. Ed. 2000, 39, 165–168. (e)
Reetz, M. T.; Westermann, E.; Lohmer, R.; Lohmer, G.
Tetrahedron Lett. 1998, 39, 8449–8452. (f) Reetz, M. T.;
Breinbauer, R.; Wanninger, K. Tetrahedron Lett. 1996, 37,
Chem. Commun. 2003, 2274–2275. (d) M e´ ry, D.; Heuz e´ , K.;
Astruc, D. Chem. Commun. 2003, 1934–1935. (e) Ma, Y.;
Song, C.; Jiang, W.; Wu, Q.; Wang, Y.; Liu, X.; Andrus, M. B.
Org. Lett. 2003, 5, 3317–3319. (f) Djakovitch, L.; Rollet, P.
Tetrahedron Lett. 2004, 45, 1367–1370. (g) Uozumi, Y.;
Kobayashi, Y. Heterocycles 2003, 59, 71–74. (h) Pal, M.;
Parasuraman, K.; Gupta, S.; Yeleswarapu, K. R. Synlett 2002,
1976–1982. (i) Fu, X.; Zhang, S.; Yin, J.; Schumacher, D. P.
Tetrahedron Lett. 2002, 43, 6673–6676. (j) B o¨ hm, V. P. W.;
Herrmann, W. A. Eur. J. Org. Chem. 2000, 3679–3681. (k) Fu,
X.; Zhang, S.; Yin, J.; Schumacher, D. Tetrahedron Lett. 2002,
4
499–4502. (g) Narayanan, R.; EI-Sayed, M. A. J. Am. Chem.
Soc. 2003, 125, 8340–8347. (h) Reetz, M. T.; Vries, J. G.
Chem. Commun. 2004, 1559–1563 and references cited
therein. (i) Reetz, M. T.; Helbig, W. J. Am. Chem. Soc.
4
3, 6673–6676. (l) Alonso, D. A.; N a´ jera, C.; Pacheco, M. C.
Tetrahedron Lett. 2002, 43, 9365–9368. (m) Fukuyama, T.;
Shinmen, M.; Nishitani, S.; Sato, M.; Ryu, I. Org. Lett. 2002,
1
994, 116, 7401–7402. (j) Reetz, M. T.; Quaiser, S. A.;
Breinbauer, R.; Tesche, B. Angew. Chem., Int. Ed. Engl. 1995,
4, 2728–2730.
4
, 1691–1694. (n) N a´ jera, C.; Gil-Molt o´ , J.; Karlstr o¨ m, S.;
3
Falvello, L. R. Org. Lett. 2003, 5, 1451–1454. (o) Alonso,
D. A.; N a´ jera, C.; Pacheco, M. C. Adv. Synth. Catal. 2003, 345,
2
2
2. The palladium colloid on poly(vinylpyrrolidone) (PVP) was
prepared according to a simple and convenient procedure, see:
Bradley, J. S.; Millar, J. M.; Hill, E. W. J. Am. Chem. Soc.
1146–1158. (p) Buchmeiser, M. R.; Schareina, T.; Kempe, R.;
Wurst, K. J. Organomet. Chem. 2001, 634, 39–46. It should be
noted that the copper-free Sonogashira coupling reactions are
representative and not comprehensive in this paper.
1
991, 113, 4016–4017.
3. For Jeffery’s catalyst systems (Pd/QX) and their applications,
see (a) Jeffery, T. J. Chem. Soc., Chem. Commun. 1984,
1
1. (a) Cheng, J.; Sun, Y.; Wang, F.; Guo, M.; Xu, J.-H.; Pan, Y.;
Zhang, Z. J. Org. Chem. 2004, 69, 5428–5432. (b) Arques, A.;
Aunon, D.; Molina, P. Tetrahedron Lett. 2004, 45, 4337–4340.
1287–1289. (b) Jeffery, T. Tetrahedron Lett. 1985, 26,
2667–2670. (c) Jeffery, T. Tetrahedron Lett. 1994, 35,
3051–3054. (d) Jeffery, T.; Galland, J. C. Tetrahedron Lett.
1994, 35, 4103–4106. (e) Jeffery, T. Tetrahedron 1996, 52,
10113–10130. (f) Jeffery, T. In Advances in Metal-Organic
(
c) Mori, A.; Kawashima, J.; Shimada, T.; Suguro, M.;
Hirabayashi, K.; Nishihara, Y. Org. Lett. 2000, 2, 2935–2937.
d) Alonso, D. A.; Najera, C.; Pacheco, M. C. Tetrahedron
(
Chemistry; Liebeskind, L. S., Ed.; Jai: London, 1996;
pp 153–260.
Lett. 2002, 43, 9365–9368. (e) Gelman, D.; Buchwald, S. L.
Angew. Chem., Int. Ed. 2003, 42, 5993–5996.
2
2
2
2
2
2
3
4. Carpino, L. A.; Chen, H.-W. J. Am. Chem. Soc. 1979, 101,
1
1
1
2. Choudary, B. M.; Madhi, S.; Chowdari, N. S.; Kantam, M. L.;
Sreedhar, B. J. Am. Chem. Soc. 2002, 124, 14127–14136.
3. Kabalka, G. W.; Wang, L.; Namboodiri, V.; Pagni, R. M.
Tetrahedron Lett. 2000, 41, 5151–5154.
3
90–394.
5. Paquett, L. A.; Wittenbrook, L. S. J. Am. Chem. Soc. 1967, 89,
483–4487.
4
6. Arcadi, A.; Cacchi, S.; Fabrizi, G.; Marinelli, F.; Pace, P. Eur.
J. Org. Chem. 1999, 12, 3305–3313.
7. Hunter, D. H.; Cram, D. J. J. Am. Chem. Soc. 1966, 88,
4. (a) Beletskaya, I. P.; Latyshev, G. V.; Tsvetkov, A. V.;
Lukashev, N. V. Tetrahedron Lett. 2003, 44, 5011–5013. (b)
Wang, L.; Li, P.; Zhang, Y. Chem. Commun. 2004, 514–515.
5. (a) Bong, D. T.; Ghadiri, M. R. Org. Lett. 2001, 3, 2509–2511.
5
765–5776.
1
8. Chow, H.-F.; Wan, C.-W.; Low, K.-H.; Yeung, Y.-Y. J. Org.
Chem. 2001, 66, 1910–1913.
9. Redenko, A. P.; Vasil’ev, A. V.; Russ J. Org. Chem. 1995, 31,
(
b) Casalnuovo, A. L.; Caladrese, J. C. J. Am. Chem. Soc.
990, 112, 4324–4330. (c) Dibowski, H.; Schmidtchen, F. P.
1
Tetrahedron Lett. 1998, 39, 525–528. (d) Genet, J.-P.; Blart,
E.; Savignac, M. Synlett 1992, 715–717.
1
360.
0. Sato, H.; Isono, N.; Miyoshi, I.; Mori, M. Tetrahedron 1996,
2, 8143–8158.
1
6. Park, S. B.; Alper, H. Chem. Commun. 2004, 1306–1307.
7. (a) Using an atmosphere of hydrogen gas diluted with nitrogen
or argon to diminish homo-coupling in Sonogashira reaction,
see: Elangovan, A.; Wang, Y.-H.; Ho, T.-I. Org. Lett. 2003, 5,
5
1
3
1. Masuda, Y.; Hoshi, M.; Arase, A. Chem. Lett. 1980, 413.
2. Kabalka, G. W.; Wang, L.; Pagni, R. M. Tetrahedron 2001, 57,
3
8
017–8028.
1841–1844. (b) Use of phase-transfer conditions to diminish
3
3. Huggins, J. M.; Bergman, R. G. J. Am. Chem. Soc. 1981, 103,
3002–3011.
homo-coupling, see: Chow, H.-F.; Wan, C.-W.; Low, K.-H.;
Yeung, Y.-Y. J. Org. Chem. 2001, 66, 1910–1913. (c) With
slow addition of the acetylene to diminish homo-coupling, see:
Thorand, S.; Krause, N. J. Org. Chem. 1998, 61, 8551–8553.
8. Leadbeater, N. E.; Marco, M.; Tominack, B. J. Org. Lett. 2003,
34. Kiplinger, J. L.; King, M. A.; Fechtenk o¨ tter, A.; Arif, A. M.;
Richmond, T. G. Organometallics 1996, 15, 5292–5301.
35. Yoshida, K.; Fueno, T. J. Org. Chem. 1973, 38, 1045–1046.
36. Feuerstein, M.; Berthiol, F.; Doucet, H.; Santelli, M. Synthesis
2004, 1281–1289.
1
1
5
, 3919–3922.
9. (a) Urgaonkar, S.; Verkade, J. G. J. Org. Chem. 2004, 69,
752–5755. (b) Zhang, G. Synlett 2005, 619–622.
5
37. Agawa, T.; Miller, S. I. J. Am. Chem. Soc. 1961, 83, 449–453.