Task-specific ionic liquid as base, ligand and reaction medium for the palladium-catalyzed Heck reaction

Article abstract of DOI:10.1016/j.tet.2008.10.042

A novel ionic liquid, which was based on ethanolamine-functionalized quaternary ammonium salt was designed and synthesized. 4-Di(hydroxyethyl)aminobutyl tributylammonium bromide (DHEABTBAB) 1, a task-specific ionic liquid, which acts as a base, ligand and reaction medium, exhibits a very high activity and recyclability to palladium-catalyzed Heck reaction. The olefinations of iodoarenes, bromoarenes and chloroarenes with olefins generated the corresponding cross-coupling products in good to excellent yields only in the presence of DHEABTBAB and palladium acetate under phosphine-free reaction conditions. It is noteworthy that palladium and DHEABTBAB could be repeatedly recycled and reused for six consecutive trials without significant loss of their activities.

Full text of DOI:10.1016/j.tet.2008.10.042

Tetrahedron 65 (2009) 364–368
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Task-specific ionic liquid as base, ligand and reaction medium
for the palladium-catalyzed Heck reaction
,
b
,
a
a
Lei Wang a , Hongji Li , Pinhua Li
*
a Department of Chemistry, Huaibei Coal Teachers College, Huaibei, Anhui 235000, PR China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel ionic liquid, which was based on ethanolamine-functionalized quaternary ammonium salt was
designed and synthesized. 4-Di(hydroxyethyl)aminobutyl tributylammonium bromide (DHEABTBAB) 1,
a task-specific ionic liquid, which acts as a base, ligand and reaction medium, exhibits a very high activity
and recyclability to palladium-catalyzed Heck reaction. The olefinations of iodoarenes, bromoarenes and
chloroarenes with olefins generated the corresponding cross-coupling products in good to excellent
yields only in the presence of DHEABTBAB and palladium acetate under phosphine-free reaction con-
ditions. It is noteworthy that palladium and DHEABTBAB could be repeatedly recycled and reused for six
consecutive trials without significant loss of their activities.
Received 4 August 2008
Received in revised form
30 September 2008
Accepted 13 October 2008
Available online 22 October 2008
Keywords:
Heck reaction
Task-specific ionic liquid (TSIL)
Ethanolamine-functionalized quaternary
ammonium salt
Ó 2008 Elsevier Ltd. All rights reserved.
4-Di(hydroxyethyl)aminobutyl
tributylammonium bromide (DHEABTBAB)
1. Introduction
imidazolium cation. In addition, the synthesis of TSILs is rather
complicated and multi-step procedures have to be required.
The use of ionic liquids (ILs) has received more attention as eco-
friendly, reusable and alternative reaction media in organic syn-
thesis because of their unique properties, such as high thermal and
chemical stability, negligible vapour pressure, no flammability, high
loading capacity and excellent electrical conductivity.1 A number of
organic reactions including hydrogenation, oxidation, C–C bond-
forming reactions have already been demonstrated in ILs.2
Most recently, much more attention has been focused on the
synthesis of functionalized ionic liquids (FILs), through in-
corporation of additional functional groups as a part of the cation
and/or anion, so-called task-specific ionic liquids (TSILs), and their
applications in chemical research. The incorporation of functional
groups can impart a particular capability to the ionic liquids, en-
hancing their capacity for catalyst reusability. Moreover, specific
functional groups, such as amine, amide, nitrile, ether, alcohol, acid,
urea or thiourea, can be incorporated into the ionic liquids for task-
specific purposes. They have shown great promise not only as
alternative green solvents, but also as reagents or catalysts in or-
ganic transformations.1b,3 However, many of them were focused on
the incorporation of functionality into a branch appended to the
The Heck reaction is one of the most important, reliable and
general reaction for carbon–carbon bond formation in organic
synthesis.4 Palladium compounds, usually complexes with phos-
phine ligands, are very often used as catalyst precursors in the Heck
reaction. Phosphines play a role of stabilizers of in situ formed
soluble Pd(0) complexes, which are generally considered as the
catalytically active forms.5 Phosphine-free catalysts have been
received great interest recently as less complicated and environment-
friendly alternatives to phosphine containing systems.2b,6 Un-
fortunately, some of the catalyst systems suffer from drawbacks of
ligands sensitivity towards air and moisture, tedious multi-step
synthesis, or high cost of ligands. Furthermore, a homogeneous
palladium catalyst usually precipitated from the solution, and
recycling or recovery of the expensive palladium is difficult. It is
desirable to develop a more robust, simple and cost-effective non-
phosphine ligand and a recyclable palladium catalyst system for
Heck reaction.
In general, the essential requirement for the Heck reaction in-
cludes a base, a ligand-stabilized active Pd species, and a reaction
medium. This promoted us to design and synthesize a task-specific
ionic liquid, which acts as a base, a non-phosphine ligand, as well as
an environmentally benign reaction medium in an ion-pair unity.
Although phosphine-free palladium-catalyzed Heck reaction in
functionalized ionic liquid, which was used as an efficient and
* Corresponding author. Tel.: þ86 561 380 2069; fax: þ86 561 309 0518.
E-mail address: leiwang@hbcnc.edu.cn (L. Wang).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.10.042

L. Wang et al. / Tetrahedron 65 (2009) 364–368
365
Table 1
recyclable reaction medium in the presence of K3PO4 has been
Effect of palladium source on the Heck reactiona
reported in our laboratory recently, it is desirable to develop more
efficient and multi-functional ionic liquid for palladium-catalyzed
Heck reaction.7 Here, we wish to report our success in the
development of a new ionic liquid, which was based on ethanol-
amine-functionalized quaternary ammonium salt. 4-Di(hydroxy-
ethyl)aminobutyl tributylammonium bromide, 1 exhibits a very
high activity and recyclability to palladium-catalyzed Heck reaction
(Scheme 1). The olefinations of iodoarenes, bromoarenes and
chloroarenes with olefins generated the corresponding cross-cou-
pling products in good to excellent yields only in the presence of 1
and palladium acetate (1 mol %) under phosphine-free reaction
conditions. It is noteworthy that palladium and 1 could be re-
peatedly recycled and reused for six consecutive trials without
significant loss of their activities.
Entry
Palladium source/amount
Yieldb (%)
1
2
3
4
5
6
7
Palladium powder (micron, 1 mol %)
Pd/C (1 mol %)
Pd2(dba)3 (1 mol %)
Pd(PPh3)2Cl2 (1 mol %)
Pd(CH3CN)2Cl2 (1 mol %)
PdCl2 (1 mol %)
0
23
47
40
52
96
98
Pd(OAc)2 (1 mol %)
a
Styrene (104 mg, 1.00 mmol), bromobenzene (157 mg, 1.00 mmol), Pd source
(0.01 mmol), 1 (2.0 mL) at 100 ꢀC for 6 h.
b
Isolated yields.
generally completed in a matter of hours, but the time, as expected,
was inversely proportional to the temperature. A reaction tem-
perature of 100 ꢀC was found to be optimal. Thus, the optimized
reaction conditions for this Heck reaction are the Pd(OAc)2 (1 mol %)
in 1 at 100 ꢀC for 6 h.
Br
BrCH2(CH2)2CH2Br
C2H5OH, reflux
(n-C4H9)3N(CH2)3CH2Br
(n-C4H9)3N
To examine the versatility of this procedure, the Heck reactions
of styrene with iodoarenes containing electron-rich, electron-poor
or electron-neutral substituents were examined. The results are
listed in Table 2. It shows that the stereoselectivities (E/Z >99%,
trans-products formed), conversions, and yields (>99% yields and
conversions) were satisfactory under the present reaction condi-
tions (entries 1–4, Table 2). For bromobenzene, activated and
deactivated bromoarenes, excellent yields of cross-coupling prod-
ucts were also isolated under the standard reaction conditions
(entries 5–10, Table 2). On the other hand, the relatively hindered
substrates, i.e., 2-methyl-bromobenzene and 3-methyl-bromo-
benzene, also underwent the olefinations and led to the good yields
(entries 11–12, Table 2). The scope of this catalytic system with
other vinyl substrates, such as ethyl acrylate, butyl acrylate and
acrylonitrile, was also examined and good to excellent results were
HN(CH2CH2OH)2
C2H5OH, reflux
(n-C4H9)3N(CH2)4N(CH2CH2OH)2 Br, 1
TSIL, 1
X
R
+
R
Pd(OAc)2 (1 mol %)
R1
R1
No Additional Base !
No Phosphine !
(E)-Product
X = I, Br, Cl R = Ar, CO2R2, CN
Recoverable TSIL !
Recoverable Catalyst !
Scheme 1. Synthesis of task-specific ionic liquid 1 and its application in the Heck
reaction.
2. Results and discussion
Table 2
The synthesis of task-specific ionic liquid 1 was illustrated in
Scheme 1. It was readily prepared through a straightforward two-
step procedure from commercially available starting materials and
reagents in good yields. Tri(n-butyl)amine was reacted with 1,4-
dibromobutane with 1:4 molar ratio in ethanol under reflux tem-
perature for 48 h to afford (4-bromobutyl)tri(n-butyl)ammonium
bromide in 95% yield. This intermediate subsequently reacted with
diethanolamine in the presence of K2CO3 in ethanol at 80 ꢀC for
24 h to generate the corresponding functionalized ionic liquid 1 in
91% yield. TSIL, 1 was further purified by drying in a vacuum (ca.
2 mmHg) at 100 ꢀC to remove the residual starting materials, re-
agents or organic solvents.
To examine its activity, 1 was used for the palladium-catalyzed
Heck reaction in the absence of any additives. The experimental
results revealed that ethanolamine-functionalized ionic liquid 1,
exhibits a very high activity. It is presumably due to the effective
N,O-ligand in organic reactions, such as asymmetric addition of
aldehydes or imines,8 Suzuki and Ullmann reactions,9 and present
reaction.
The effect of palladium source on the Heck reaction of bromo-
benzene and styrene in the presence of 1 was explored (Table 1).
Among the palladium sources tested, simple palladium inorganic
salts, such as Pd(OAc)2 and PdCl2, proved to be the best of choice
(98% and 96% yields of trans-stilbene, respectively). Pd(CH3CN)2Cl2,
Pd(PPh3)2Cl2, Pd2(dba)3 and Pd/C were inferior and generated
trans-stilbene in 52%, 47%, 40% and 23% yields, respectively. How-
ever, Pd powder (micron) was found to be inactive to the Heck
reaction.
Palladium-catalyzed Heck reaction in TSIL 1a
Entry
Organic halide
Olefin
Yieldb (%)
1
2
3
4
5
6
7
8
C6H5I
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
C6H5CH]CH2
99
99
99
99
99
99
95
99
95
93
88
82
89
86
66
p-CH3C6H4I
p-CH3OC6H4I
p-CH3COC6H4I
C6H5Br
p-CH3COC6H4Br
p-CNC6H4Br
p-C2H5O2CC6H4Br
p-CH3C6H4Br
p-CH3OC6H4Br
m-CH3C6H4Br
o-CH3C6H4Br
p-CNC6H4Cl
p-CH3COC6H4Cl
C6H5Cl
9
10
11
12
13
14
15
16
17
18
19
20
21
22
a
C6H5I
99
99
CO2C2H5
CO2C4H9
p-CH3OC6H4I
C6H5Br
99
96
92
97
CO2C2H5
CO2C2H5
CO2C2H5
CN
p-NO2C6H4Br
p-CH3OC6H4Br
p-CH3C6H4Br
Br
90
CO2C2H5
N
Olefin (1.00 mmol), organic halide (1.00 mmol), Pd(OAc)2 (2.3 mg, 0.01 mmol), 1
(2.0 mL) at 100 ꢀC for 6 h.
During the course of our further optimization of the reaction
conditions, when using 1 mol % of Pd(OAc)2 in 1, the reactions were
b
Isolated yields.

366
L. Wang et al. / Tetrahedron 65 (2009) 364–368
obtained for iodoarenes, bromoarenes including relatively deacti-
vated bromides bearing an methoxy as the substituent, and het-
eroaryl bromide, such as 3-bromopyridine under identical
conditions (entries 16–22, Table 2). It is noteworthy that good
yields of desired products were observed for activated chloroarenes
(entries 13–14, Table 2). However, a moderate yield of the product
was generated for chlorobenzene (entry 15, Table 2) and little or no
activity was observed with deactivated aryl chlorides.
In contrast, while no significant colour change was observed in
the course of the Heck reaction, carried out in ordinary ionic liquids,
such as [Bmim]Br, [Bmim]BF4 or [Bmim]PF6, the task-specific ionic
liquid 1–palladium solution rapidly turned black following the
addition of bromobenzene, which was indicative of nanoparticle
palladium metal formation. It was possible to isolate the palladium
nanoparticles from the Heck reactions, which were subsequently
analyzed using transmission electron microscopy (TEM), and the
TEM image was shown in Figure 1. The nanoparticles obtained from
1 have an average diameter of ca. 4 nm, and such microdissimilarity
was in accordance with the macroappearance disparity of the ionic
liquid systems. The TEM image also indicated that nanoparticles
generated in 1 is evenly distributed and it supports the hypothesis
that the ethanolamine-functionalized ionic liquid stabilizes the
palladium colloid. The ethanolamine moiety could either co-
ordinate to the palladium surface or point away from the surface of
the nanoparticle, thereby repelling proximal neighbours. In this
case, agglomeration would be prevented and, ultimately, the ac-
tivity of palladium catalyst was increased.
100
80
60
40
20
0
1
2
3
4
5
6
Cycle
Figure 2. Successive trials by using recoverable 1 and palladium.
advantages: (i) it acts as an eco-friendly and recyclable reaction
medium; (ii) it acts as a base and an N,O-ligand, so the Heck re-
action can be carried out under no additional ligand and base added
reaction conditions; (iii) it is applicable to a broader substrate scope
(aromatic iodides, bromides and chlorides); (iv) combination of
functional groups including Br, N and OH, enhances Heck reaction
and gives high yields of products; (v) Pd catalyst and 1 can be re-
covered and recycled; (vi) its experimental process is simple.
The recyclability of 1 and palladium was also investigated. When
bromobenzene was treated with styrene with 1 mol % Pd(OAc)2 in 1
at 100 ꢀC for 6 h, the desired coupling product was obtained in 99%
yield. After extraction of the product from the reaction mixture
using ethyl ether, 1 and palladium were recovered and fresh
starting materials were charged. Palladium and 1 were recycled six
times with no loss of their activities (Fig. 2). Meanwhile, palladium
leaching in the catalytic system was also determined. Inductively
coupled plasma (ICP) analyses of the extracted organic solvents
indicated that Pd content was <0.2 ppm.
Organic Base
OH
N
OH
(n-C4H9)3N
IL, Eco-friendly &
Recyclable
Br
N,O-Ligand
Effective anion
The functions of TSIL 1 were shown in Scheme 2. In comparison
with the general ionic liquid, our developed 1, showed particular
Scheme 2. The functions of task-specific ionic liquid 1.
3. Conclusion
In summary, we have developed an efficient and economic
catalyst system for Heck reaction using 1 as solvent, ligand and base
in a unity, and palladium acetate as catalyst under phosphine-free
reaction conditions. The olefination reactions of olefins with
iodoarenes, bromoarenes and chloroarenes generated the corre-
sponding coupling products in good to excellent yields in the
presence of 1, an ideal TSIL for its high activity and easily synthe-
sized. In addition,1 and palladium can be easily recycled and reused
with the same efficacies for six cycles.
4. Experimental
4.1. Physical measurements and materials
Melting points were recorded on a WRS-2B melting point ap-
paratus and are uncorrected. All 1H NMR spectra were recorded at
300 MHz or 400 MHz by Bruker FT-NMR spectrometers. Chemical
shift are given as d value with reference to tetramethylsilane (TMS)
as internal standard. IR spectra were obtained by using a Nicolet
NEXUS 470 spectrophotometer. The CHN analysis was performed
on a Vario El III elementar. The Pd content was determined by
a Jarrell-Ash 1100 ICP analysis. Products were purified by flash
chromatography on 230–400 mesh silica gel, SiO2. The chemicals
Figure 1. TEM of palladium metal in the Heck reaction carried out in 1.

L. Wang et al. / Tetrahedron 65 (2009) 364–368
367
were purchased from commercial suppliers (Aldrich, USA and
4.5. (E)-Stilbene
Shanghai Chemical Company, China) and were used without puri-
fication prior to use.
Mp 120–122 ꢀC (lit.10 mp 120 ꢀC). 1H NMR (400 MHz, DMSO):
d
¼7.64–7.60 (m, 4H), 7.40–7.27 (m, 4H), 7.24–7.13 (m, 4H). IR (cmꢂ1
,
KBr):
n
¼3020, 1631, 1495, 1451, 1364, 962, 764, 692.
4.2. Preparation of 4-di(hydroxyethyl)aminobutyl
tributylammonium bromide, 1
4.6. (E)-4-Methylstilbene
In a 100 mL round-bottom flask were introduced successively
30 mL of anhydrous ethanol and 1,4-dibromobutane (8.64 g,
40 mmol). Tri-n-butylamine (1.86 g, 10 mmol) in 10 mL of anhy-
drous ethanol was added drop-wise in 3 h. After the reaction
mixture was refluxed for 48 h, ethanol and unreacted starting
materials were removed under reduced pressure. The residue was
washed with ethyl ether (10 mLꢁ3). The obtained liquid was dried
under reduced pressure at 80 ꢀC for 24 h to generate the desired
product, (4-bromobutyl)tri(n-butyl)ammonium bromide (3.81 g) in
Mp 121–122 ꢀC (lit.10 mp 120 ꢀC). 1H NMR (400 MHz, DMSO):
d
¼7.59 (d, J¼7.6 Hz, 2H), 7.50 (d, J¼8.0 Hz, 2H), 7.41–7.24 (m, 3H),
7.21–7.16 (m, 4H), 2.31 (s, 3H). IR (cmꢂ1, KBr):
1574, 1448, 1365, 969, 809, 749, 690.
n
¼3018, 2831, 1632,
4.7. (E)-4-Acetylstilbene
Mp 149–151 ꢀC (lit.9 mp 148–150 ꢀC). 1H NMR (400 MHz,
95% yield. 1H NMR (400 MHz, DMSO):
d
¼3.69 (t, J¼6.2 Hz, 2H),
DMSO):
d
¼7.97 (d, J¼8.4 Hz, 2H), 7.75 (d, J¼8.4 Hz, 2H), 7.66 (d,
J¼7.6 Hz, 2H), 7.43–7.32 (m, 5H), 2.51 (s, 3H). IR (cmꢂ1, KBr):
3.56–3.43 (m, 8H), 2.06–1.91 (m, 2ꢁ2H), 1.79–1.73 (m, 3ꢁ2H), 1.43–
1.37 (m, 3ꢁ2H), 0.94 (t, J¼7.4 Hz, 3ꢁ3H). 13C NMR (100 MHz,
n
¼2897, 1708, 1600, 1517, 1368, 1357, 1265, 1178, 1074, 966, 867, 821,
¼58.1, 57.3, 33.6, 29.0, 23.4, 20.1, 19.1, 12.9. IR (cmꢂ1, film):
756, 725, 692.
DMSO):
d
n
¼2961, 2874, 1468, 1382, 740.
To a 50 mL round-bottomed flask, (4-bromobutyl)tri(n-butyl)-
4.8. (E)-4-Cyanostilbene
ammonium bromide (2.0 g, 5 mmol), potassium carbonate (0.69 g,
5 mmol) and diethanolamine (0.63 g, 6 mmol) were mixed well
in 20 mL of dry ethanol. The mixture was stirred for 24 h at
80 ꢀC. After completion of reaction, ethanol and unreacted starting
materials were removed under reduced pressure. The residue was
washed with ethyl acetate (5 mLꢁ2), ethyl ether (5 mLꢁ2) and
hexane (5 mLꢁ2), respectively. The organic solvent was evaporated
under reduced pressure. The residue was dried in a vacuum (ca.
1 mmHg) at 100 ꢀC for 24 h to generate the corresponding product,
4-di(hydroxyethyl)aminobutyl tri(n-butyl)ammonium bromide
(1.94 g) in 91% yield. Freezing point: ꢂ18 ꢀC. 1H NMR (400 MHz,
Mp 117–119 ꢀC (lit.10 mp 117.4–117.7 ꢀC). 1H NMR (400 MHz,
DMSO):
d
¼7.83 (d, J¼8.4 Hz, 2H), 7.80 (d, J¼8.4 Hz, 2H), 7.66 (d,
J¼7.6 Hz, 2H), 7.56 (t, J¼7.4 Hz, 2H), 7.44 (t, J¼8.4 Hz, 1H), 7.31 (d,
J¼16.5 Hz,1H), 7.19 (d, J¼16.5 Hz,1H). IR (cmꢂ1, KBr):
¼2834, 2362,
n
1602, 1504, 1364, 973.
4.9. (E)-4-Methoxystilbene
Mp 136–138 ꢀC (lit.11 mp 135–137 ꢀC). 1H NMR (400 MHz,
DMSO):
d
¼7.60 (d, J¼6.4 Hz, 2H), 7.50 (d, J¼8.4 Hz, 2H), 7.36 (t,
DMSO):
d
¼3.62 (s, br, 2H), 3.44–3.38 (m, 6H), 3.21–3.15 (m, 8H),
J¼7.8 Hz, 2H), 7.24 (t, J¼6.4 Hz, 1H), 7.16 (d, J¼16.4 Hz, 1H), 7.10 (d,
J¼16.4 Hz, 1H), 6.95 (d, J¼8.8 Hz, 2H), 3.80 (s, 3H). IR (cmꢂ1, KBr):
3.00–2.89 (m, 4H), 1.66–1.53 (m, 10H), 1.42–1.35 (m, 3ꢁ2H), 0.93 (t,
J¼6.8 Hz, 3ꢁ3H). 13C NMR (100 MHz, DMSO):
d
¼59.9, 58.2, 57.6,
n
¼2836, 1605, 1512, 1447, 1365, 1297, 1179, 1030, 967, 828, 689.
57.3, 55.8, 26.6, 23.2, 20.3, 19.2, 13.0. IR (cmꢂ1, film):
n
¼3354, 2956,
2870, 1472, 1385, 749. Anal. Calcd for C20H45BrN2O2: C, 56.46; H,
10.66; N, 6.58. Found: C, 56.08; H, 10.35; N, 6.99.
4.10. (E)-Ethyl cinnamate
Oil.12 1H NMR (400 MHz, DMSO):
d
¼7.67 (d, J¼16.4 Hz, 1H),
7.62–7.50 (m, 2H), 7.41–7.36 (m, 3H), 6.60 (d, J¼16.0 Hz,1H), 4.18 (q,
4.3. General experimental procedure for the Heck reaction
J¼7.2 Hz, 2H), 1.25 (t, J¼7.0 Hz, 3H). IR (cmꢂ1, film):
¼3074, 2954,
n
1709, 1621, 1497, 1312, 772, 687.
Under an atmosphere of nitrogen, an oven-dried, two-necked
round-bottom flask containing a stir bar was charged with an or-
ganic halide (1.00 mmol), olefin (1.00 mmol), Pd(OAc)2 (2.3 mg,
0.01 mmol), and task-specific ionic liquid, 1 (2.0 mL). The mixture
was heated and stirred at 100 ꢀC for 6 h. After completion of the
reaction, ethyl ether (3.0 mLꢁ2) was added to the mixture to ex-
tract the product. The combined organic layer was washed with
water and brine, dried with MgSO4 and evaporated under reduced
pressure. The residue was finally purified by flash chromatography
on silica gel to give the desired product.
4.11. (E)-Ethyl 3-(4-nitrophenyl)-2-propenoate
Mp 138–140 ꢀC (lit.13 mp 139–139.8 ꢀC). 1H NMR (400 MHz,
DMSO):
¼8.25 (d, J¼8.8 Hz, 2H), 8.20 (d, J¼8.8 Hz, 2H), 7.69 (d,
d
J¼16.0 Hz, 1H), 6.57 (d, J¼16.0 Hz, 1H), 4.22 (q, J¼7.0 Hz, 2H), 1.26 (t,
J¼7.0 Hz, 3H). IR (cmꢂ1, KBr):
¼3075, 2982, 1717, 1644, 1525, 1446,
n
1354, 1188, 1034, 873, 767, 664.
4.12. (E)-Ethyl 4-styrylbenzoate
4.4. The recyclability of TSIL, 1 and palladium catalyst
Mp 106.0–107.5 ꢀC (lit.14 mp 106.0–106.5 ꢀC). 1H NMR
(400 MHz, DMSO):
d
¼7.96 (d, J¼8.4 Hz, 2H), 7.66 (d, J¼7.6 Hz, 2H),
After carrying out the reaction, the mixture was extracted with
ethyl ether (3 mLꢁ2). After the neutralization of ammonium salt
formed during the reaction with potassium carbonate, 1 and pal-
ladium were washed with C2H5OH (2 mL) to remove sodium halide
through centrifugal separation. The centrifugate containing
C2H5OH, 1 and palladium was evaporated under reduced pressure.
The residue was then washed with Et2O (3 mL), CH2Cl2 (3 mL) and
hexane (3 mL), respectively, in order to remove adsorbed organic
substrates. After dried under reduced pressure, they can be reused
directly without further purification.
7.46–7.30 (m, 5H), 7.22 (d, J¼16.4 Hz, 1H), 7.13 (d, J¼16.4 Hz, 1H),
4.32 (q, J¼7.1 Hz, 2H), 1.34 (t, J¼7.2 Hz, 3H). IR (cmꢂ1, KBr):
¼3035,
n
2928, 1711, 1632, 1365, 1277, 1176, 851, 776.
4.13. (E)-2-Methylstilbene
Mp 31–32 ꢀC (lit.12 30–32 ꢀC). 1H NMR (300 MHz, CDCl3):
d
¼7.58–7.48 (m, 3H), 7.37–7.16 (m, 6H), 7.01 (d, J¼16.2 Hz, 2H), 2.36
(s, 3H). IR (cmꢂ1, KBr):
n¼2920, 1601, 1495, 1448, 965, 761.

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L. Wang et al. / Tetrahedron 65 (2009) 364–368
3. (a) Luo, S.; Mi, X.; Zhang, L.; Liu, S.; Xu, H.; Cheng, J.-P. Angew. Chem., Int. Ed.
4.14. (E)-3-Methylstilbene
2006, 45, 3093–3097; (b) Fukumoto, K.; Yoshizawa, M.; Ohno, H. J. Am. Chem.
Soc. 2005, 127, 2398–2399; (c) Zhao, D.; Fei, Z.; Geldbach, T. J.; Scopelliti, R.;
Dyson, P. J. J. Am. Chem. Soc. 2004, 126, 15876–15882; (d) Yao, Q.; Zhang, Y.
Angew. Chem., Int. Ed. 2003, 42, 3395–3398; (e) Cole, A. C.; Jensen, J. L.; Ntai, I.;
Tran, K. L. T.; Weaver, K. J.; Forbes, D. C.; Davis, J. H., Jr. J. Am. Chem. Soc. 2002,
124, 5962–5963; (f) Song, G.; Cai, Y.; Peng, Y. J. Comb. Chem. 2005, 7, 561–566;
(g) Xiao, J.-C.; Twamley, B.; Shreeve, J. M. Org. Lett. 2004, 6, 3845–3847; (h)
Holbrey, J. D.; Reichert, W. M.; Tkatchenko, I.; Bouajila, E.; Walter, O.; Tommasi,
I.; Rogers, R. D. Chem. Commun. 2003, 28–29; (i) Branco, L. C.; Rosa, J. N.; Ramos,
J. J. M.; Alfonso, C. A. M. Chem.dEur. J. 2002, 8, 3671–3677; (j) Visser, A. E.;
Swatloski, R. P.; Reichert, W. M.; Davis, J. H., Jr.; Rogers, R. D.; Mayton, R.; Sheff,
S.; Wierzbicki, A. Chem. Commun. 2001, 135–136; (k) Merrigan, T. L.; Bates, E. D.;
Dorman, S. C.; Davis, J. H., Jr. Chem. Commun. 2000, 2051–2052.
Mp 47–48 ꢀC (lit.15 48.6–49.2 ꢀC). 1H NMR (300 MHz, CDCl3):
d
¼7.52–7.50 (m, 2H), 7.35–7.31 (m, 4H), 7.27–7.22 (m, 2H), 7.09–
7.07 (m, 3H), 2.38 (s, 3H). IR (cmꢂ1, KBr):
966, 784, 695.
n
¼3021, 2921, 1600, 1495,
4.15. (E)-4-Methylcinnamonitrile
Mp 72–73 ꢀC (lit.16 mp 71–73 ꢀC). 1H NMR (400 MHz, DMSO):
d
¼7.58 (d, J¼16.4 Hz, 1H), 7.53–7.23 (m, 4H), 6.37 (d, J¼16.4 Hz, 1H),
4. (a) Heck, R. F. Acc. Chem. Res. 1979, 12, 146–151; (b) Heck, R. F. Palladium Re-
agents in Organic Synthesis; Academic: London, UK, 1985; (c) Heck, R. F. In
Comprehensive Organic Synthesis; Trost, B. M., Flemming, I., Eds.; Pergamon:
New York, NY, 1991; Vol. 4, Chapter 4.3; (d) Cornils, B.; Herrmann, W. A. Applied
2.33 (s, 3H). IR (cmꢂ1, KBr):
1181, 1110, 978, 801.
n
¼3062, 2956, 2216, 1653, 1624, 1618,
Homogeneous Catalysis with Organometallic Compounds:
A Comprehensive
Handbook in Two Volumes; VCH: Weinheim, New York, NY, 1996; (e) Negishi,
E.-i. Handbook of Organopalladium Chemistry for Organic Synthesis; Wiley-
Interscience: New York, NY, 2002; (f) Meijere, A.; Diederich, F. Metal-Catalyzed
Cross-Coupling Reactions; Wiley-VCH: New York, NY, 2004.
4.16. (E)-Butyl 3-(4-methoxyphenyl)-2-propenoate
Light yellow liquid.17 1H NMR (300 MHz, CDCl3):
d
¼7.64 (d,
5. Amatore, C.; Jutand, A. Acc. Chem. Res. 2000, 33, 314–321.
J¼16.8 Hz, 1H), 7.47 (d, J¼8.7 Hz, 2H), 6.89 (d, J¼8.7 Hz, 2H), 6.30 (d,
6. (a) Schmidt, A. F.; Smirnov, V. V. J. Mol. Catal. A: Chem. 2003, 203, 75–78; (b)
Gurtler, C.; Buchwald, S. L. Chem.dEur. J. 1999, 5, 3107–3112; (c) Ohff, M.; Ohff,
A.; Milstein, D. Chem. Commun. 1999, 357–358; (d) Bergbreiter, D. E.; Osburn, P.
L.; Wilson, A.; Sink, E. J. Am. Chem. Soc. 2000, 122, 9058–9064; (e) Rocaboy, C.;
Gladysz, J. A. Org. Lett. 2002, 4, 1993–1996; (f) Consorti, C. S.; Zanini, M. L.; Leal,
S.; Ebeling, G.; Dupont, J. Org. Lett. 2003, 5, 983–986; (g) Consorti, C. S.; Flores,
F. R.; Dupont, J. J. Am. Chem. Soc. 2005, 127, 12054–12065.
J¼15.9 Hz, 1H), 4.20 (t, J¼6.6 Hz, 2H), 3.82 (s, 3H), 1.73–1.63 (m, 2H),
1.49–1.37 (m, 2H), 0.97 (t, J¼7.2 Hz, 3H). IR (cmꢂ1, film):
¼2959,
n
2934, 1604, 1463, 983, 828.
4.17. (E)-Ethyl 3-(3-pyridinyl)-2-propenoate
7. Zhou, L.; Wang, L. Synthesis 2006, 2653–2658.
8. Chiral amino alcohols have been widely used as ligands (O,N-ligands) in the
asymmetric alkynylation of aldehydes, see: (a) Emmerson, D. P. G.; Hems, W. P.;
Davis, B. G. Org. Lett. 2006, 8, 207–210; (b) Lu, G.; Li, X.; Zhou, Z.; Chan, W. L.;
Chan, A. S. C. Tetrahedron: Asymmetry 2001, 12, 2147–2152 the asymmetric
diethylzinc addition to aldehyde and imines, see: (c) Tanyeli, C.; Suenbuel, M.
Tetrahedron: Asymmetry 2005, 16, 2039–2043; (d) Jimeno, C.; Pasto, M.; Riera,
A.; Pericas, M. A. J. Org. Chem. 2003, 68, 3130–3138; (e) Nevalainen, M.; Ne-
valainen, V. Tetrahedron: Asymmetry 2001, 12, 1771–1777; (f) Soai, K.; Hatanaka,
T.; Miyazawa, T. J. Chem. Soc., Chem. Commun. 1992, 1097–1098; (g) Brandt, P.;
Hedberg, C.; Lawonn, K.; Pinho, P.; Andersson, P. G. Chem.dEur. J. 1999, 5, 1692–
1699 the asymmetric ruthenium-catalyzed transfer hydrogenation of ketones,
see: (h) Wu, X.; Li, X.; McConville, M.; Saidi, O.; Xiao, J. J. Mol. Catal. A: Chem.
2006, 247, 153–158; (i) Patti, A.; Pedotti, S. Tetrahedron: Asymmetry 2003, 14,
597–602 the enantioselective trimethylsilylcyanation of aldehydes, see: (j) You,
J.-S.; Gau, H.-M.; Choi, M. C. K. Chem. Commun. 2000, 1963–1964 and in the
enantioselective Henry reactions, see: (k) Palomo, C.; Oiarbide, M.; Laso, A.
Angew. Chem., Int. Ed. 2005, 44, 3881–3884.
Light red liquid.18 1H NMR (300 MHz, CDCl3):
d¼8.73 (s, 1H),
8.56 (d, J¼4.8 Hz, 1H), 7.87 (d, J¼8.1 Hz, 1H), 7.64 (d, J¼16.2 Hz, 1H),
7.38–7.34 (m, 1H), 6.50 (d, J¼15.9 Hz, 1H), 4.26 (q, J¼6.8 Hz, 2H),
1.28 (t, J¼7.2 Hz, 3H). IR (cmꢂ1, film):
¼3054, 2956, 1703, 1604,
n
1565, 1437, 968, 825.
Acknowledgements
We gratefully acknowledge financial support by the National
Natural Science Foundation of China (No. 20772043, 20572031),
and the Key Project of Science and Technology of the Department of
Education, Anhui Province, China (No. ZD2007005-1).
9. Amino alcohols, such as prolinol and trans-2-aminocyclohexanol, as effective
ligands (O,N-ligands) for Ni-catalyzed Suzuki reactions of unactivated alkyl
halides, including secondary alkyl chlorides, with arylboronic acids, see: (a)
Gonzalez-Bobes, F.; Fu, G. C. J. Am. Chem. Soc. 2006, 128, 5360–5361 amino ethyl
ethers as ligands (O,N-ligands) for vinyl aryl ether bond formation by direct
coupling of vinyl halides and phenols under mild Ullmann-type reaction con-
dition, see: (b) Wan, Z.; Jones, C. D.; Koenig, T. M.; Pu, Y. J.; Mitchell, D. Tetra-
hedron Lett. 2003, 44, 8257–8259.
10. Iyer, S.; Kulkarni, G. M.; Ramesh, C. Tetrahedron 2004, 60, 2163–2172.
11. Sugihara, T.; Satoh, T.;Miura, M.;Nomura, M. Adv. Synth. Catal. 2004, 346,1765–1772.
12. Huang, Z. Z.; Tang, Y. J. Org. Chem. 2002, 67, 5320–5326.
13. Bloomfield, J. J.; Fuchs, R. J. Org. Chem. 1961, 26, 2991–2993.
14. Nakao, Y.; Imanaka, H.; Sahoo, A. K.; Yada, A.; Hiyama, T. J. Am. Chem. Soc. 2005,
127, 6952–6953.
15. Ruasse, M. F.; Dubois, J. E. J. Org. Chem. 1972, 37, 1770–1778.
16. Morton, C. J. H.; Gilmour, R.; Smith, D. M.; Lightfoot, P.; Slawin, A. M. Z.; MacLean,
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