Remarkably facile heck reactions in aqueous two-phase system catalyzed by reusable Pd/C under ligand-free conditions

Article abstract of DOI:10.1080/00397911.2010.535943

A fast and convenient Heck reaction was achieved catalyzed by Pd/C in aqueous two-phase system. The aqueous two-phase system has been shown to be a highly active solvent for Heck reactions of aryl halides even in the absence of organic ligands. Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397911.2010.535943

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Remarkably Facile Heck Reactions in
Aqueous Two-Phase System Catalyzed
by Reusable Pd/C Under Ligand-Free
Conditions
Yan-Qin Yuan a & Sheng-Rong Guo a
a Department of Chemistry , Lishui University , Lishui , China
Accepted author version posted online: 07 Oct 2011.Published
online: 16 Dec 2011.
To cite this article: Yan-Qin Yuan & Sheng-Rong Guo (2012) Remarkably Facile Heck Reactions in
Aqueous Two-Phase System Catalyzed by Reusable Pd/C Under Ligand-Free Conditions, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
42:7, 1059-1069, DOI: 10.1080/00397911.2010.535943
To link to this article: http://dx.doi.org/10.1080/00397911.2010.535943
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Synthetic Communications1, 42: 1059–1069, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.535943
REMARKABLY FACILE HECK REACTIONS IN AQUEOUS
TWO-PHASE SYSTEM CATALYZED BY REUSABLE
Pd/C UNDER LIGAND-FREE CONDITIONS
Yan-Qin Yuan and Sheng-Rong Guo
Department of Chemistry, Lishui University, Lishui, China
GRAPHICAL ABSTRACT
Abstract A fast and convenient Heck reaction was achieved catalyzed by Pd/C in aqueous
two-phase system. The aqueous two-phase system has been shown to be a highly active
solvent for Heck reactions of aryl halides even in the absence of organic ligands.
Keywords Aqueous two-phase system; Heck reaction; Pd=C; trans-cinnamate
INTRODUCTION
The Heck reaction, a palladium-catalyzed cross-coupling of olefins with aryl
and vinyl halides,[1] is widely employed in modern organic synthesis for preparation
of alkenes containing virtually any functional groups.[2] The reaction is usually car-
ried out in organic solvents with prolonged heating in the presence of palladium
complexes with phosphine ligands (1–5 mol%) and an appropriate base.[3] In recent
years, catalysts based on phosphorus,[4] sulfur,[5] nitrogen-containing[6] pallada-
cycles,[7] and nucleophilic N-heterocyclic carbenes[8] have been proposed instead of
palladium complexes with phosphine. However, even in the presence of new, more
efficient catalysts, the reaction is completed at 100–150 ꢀC in 24–90 h.[9,10] For this
reason, a search for a more active reaction system is still among the most important
tasks in the study of Heck reactions.[10]
Another promising line (from the practical standpoint) in this area is the use of
water instead of toxic and difficult to recover organic solvents, because water is the
most accessible, safe, and ecologically pure solvent.[11] Recently, much effort has
been directed toward using water as a solvent for organic and organometallic
Received June 1, 2010.
Address correspondence to Sheng-Rong Guo, Department of Chemistry, Lishui University, Lishui
323000, China. E-mail: guosr9609@163.com
1059

1060
Y.-Q. YUAN AND S.-R. GUO
reactions,[12] but the main problem with the application of water in organic synthesis
is the long time of reaction and the insolubility of many reagents and catalysts in this
medium.
An aqueous two-phase system (ATPS) is widely used in biochemistry and bio-
technology for purification of proteins,[13] enzymes,[14] amino acids[15] and so on.[16]
ATPS has great potential for industrial applications because it can be used to obtain
a concentrated and purified product in one step by addition of crude broths contain-
ing suspended matter (e.g., cells) and offers gentle nontoxic environments for labile
biomolecules. To seek new reaction solvents, we found that the ATPS is more effec-
tive than pure water or other traditional organic solvents in the Heck reaction, so we
now report a new method for the Heck reaction that using ATPS as solvent cata-
lyzed by ligand-free and reusable Pd=C catalysts.
RESULTS AND DISCUSSION
Generally there are two type of aqueous two-phase systems: one is composed
of a polymer, a phase-separation salt (which is the key factor because the organic
solvent and the salts absorb the water together until it has a dynamic balance to
form the two-phase system), and water (e.g., PEG=Na2SO4=H2O), and another is
composed of an organic solvent, a phase-separation salt, and water (e.g., acetone=
(NH4)2SO4=H2O). As a model, the Heck reaction of PhI with methyl acrylate
(MA) catalyzed by 3 mol% Pd=C (5%) without ligand and cocatalyst under reflux
condition (about 77–80 ꢀC) was examined in different ATPSs such as ethanol=
K2HPO4=H2O, and the results seen in Table 1. In pure water, only 16% conversion
was obtained after 12 h (Table 1, entry 2). While using the base of K2CO3 in pure
water, the product is a mixture that include the methyl cinnamate and cinnamic acid
(Table 1, entry 1). Addition of a phase-transfer catalyst (PTC) (e.g., cetyltrimethy-
lammonium bromide, CTAB) led only to a gradual increase in the conversion rate.
In anhydrous ethanol, only 21% conversion was obtained after 12 h (Table 1, entry
3); we also scanned other traditional solvents, and both the yields and reaction times
are moderate to good (Table 1, entries 4–7). While using the ATPS as solvent, the
product conversion increased very quickly. In ethanol=K2HPO4 ATPS, the yield
of methyl cinnamate increased dramatically to 96% after 2 h (Table 1, entries
9 and 10). This result encouraged us to explore the Heck reaction in a series of
ATPSs to find the optimal conditions for the cross-coupling reaction.
To optimize the ATPS and find an efficient protocol for Heck coupling reac-
tion, we studied the effect of various parameters such as solvent, phase-separation
salts (they act in a double role: those salts can separate the mixture solvent into
two phases, and the basic salt can also promote the Heck reaction, while the acidic
salts did not work for the reaction), and catalyst (Scheme 1). The results are
summarized in Table 1. We selected three simple ATPSs as reaction solvents to find
the best one for the Heck reaction (Scheme 1). The alkalinity of K2CO3 is too strong
to lead the product to hydrolyze into cinnamic acid (entries 1 and 8), and the Heck
reaction (entries 9 and 10) proceeded in 96% yield catalyzed by Pd=C in the EtOH=
K2HPO4 ATPS reflux for 2 h. In the acetone=K2HPO4 system, it proceeded in 87%
yield (entry 11), and in the PEG2000=K2HPO4 system (entry 14) it gave 89%
yield. No reaction occurred in the acid ATPS such as acetone=(NH4)2SO4 or

HECK REACTIONS IN AQUEOUS SYSTEM
1061
Table 1. Effect of different solvents on the Heck reaction of C6H5I with MA under reflux conditionsa
Entry
1
Solvent
Water
Phase-separation salts
K2CO3
Catalyst
T (ꢀC=h)
Yieldb (%)
Pd=C
Pd(OAc)2
Pd=C
Reflux=12
Reflux=12
Reflux=12
Reflux=12
Reflux=12
Reflux=12
Reflux=8
Reflux=8
Reflux=8
Reflux=8
Reflux=2
Reflux=2
Reflux=2
Reflux=2
Reflux=2
Reflux=2
Reflux=2
Reflux=2
Reflux=2
Reflux=2
Mixture
Mixture
16, 21c
15, 19c
21
2
3
Water
EtOH
K2HPO4
K2HPO4
Pd(OAc)2
Pd=C
Pd(OAc)2
Pd=C
Pd=C
23
82
4
5
6
7
8
DMF
DMSO
K2HPO4
K2HPO4
K3PO4
85
73
1,4-Dioxane
Toluene
EtOH=water
Pd=C
Pd=C
K3PO4
K2CO3
61
Pd=C
Pd(OAc)2
Pd=C
Mixture
Mixture
96
9
EtOH=water
EtOH=water
K2HPO4
K3PO4
Pd(OAc)2
Pd=C
95
94
10
Pd(OAc)2
Pd=C
Pd=C
90
87
11
12
13
14
Acetone=water
Acetone=water
PEG2000=water
PEG2000=water
K2HPO4
(NH4)2SO4
(NH4)2SO4
K2HPO4
—
—
Pd=C
Pd=C
89
aReaction condition: 3 mmol PhI, 3.3 mmol methyl acrylate, 3 mol% Pd=C, 8 mmol base (or phase sep-
aration salts), and solvent (10 mL), reflux at 80 ꢀC for corresponding time by GC or TLC.
bIsolated yield.
cAdded CTAB.
PEG2000=(NH4)2SO4 system (entries 12 and 13). We got similar results in the ATPS
catalyzed by Pd(OAc)2. From all those experimental data in Table 1, we consider
that the ATPS is better than the pure water, ethanol, dimethylformamide (DMF),
and other traditional solvents for the Heck reaction. The catalytic activity of Pd=
C is similar to that of Pd(OAc)2 and it can be reused, so we finally consider that
EtOH=K2HPO4 ATPS as solvent catalyzed by Pd=C is the optimal condition for
the Heck reaction.
Taking the reaction of C6H5I with methyl acrylate as a model in the ethanol=
water two-phase system, we also scanned the effects of other bases such as KOH,
NaOH, Na2CO3, NaHCO3, KH2PO4, and DBU (1,8-diazabicyclo[5.4.0]undec-7-
ene). All those bases could not separate the mixture into two phases, so the reaction
conditions are like the traditional condition (Scheme 2). Among the bases, KOH,
NaOH, and Na2CO3 made the most of methyl cinnamate to decompose into cin-
namic acid (Table 2, entries 1–3). NaHCO3, KH2PO4, and DBU gave moderate
yields of 78–86% (Table 2, entries 4–6). It must be pointed that only K2HPO4,
Scheme 1.

1062
Y.-Q. YUAN AND S.-R. GUO
Scheme 2.
K3PO4, and K2CO3 can make the ethanol aqueous separate into two phases, whereas
KOH, NaOH, Na2CO3, DBU, NaHCO3, and KH2PO4 do not have separation
phenomena.
The typical experimental procedure for the Pd=C catalyzed Heck-type cross-
coupling reactions is as follows: The reaction was carried out simply by treatment
of a solution of aryl halides (3 mmol), olefin (3.3 mmol, 1.1 eq), and 3 mol% Pd=C
in an ATPS (6 mL ethanol, 4 mL water, 8 mmol K2HPO4) reflux for an appropriate
period of time until there was complete consumption of the starting material, as
monitored by thin-layer chromatography (TLC). After the reaction, the mixture
was filtered to recycle the catalyst, and the residue mixture fell into two phases auto-
matically. The supernatant phase, which contains 96% of the product, was separated
out and another 6 mL were added to extract the residue (about 4% of product in the
water phase). It was dried over Na2SO4. The solvent was filtered and evaporated.
The product was purified by chromatography on silica (eluent: EtOAc=petroleum
ether ¼ 1:15). The purity of the isolated product was determined by gas chromato-
1
graphic (GC) analysis or H NMR. The results are summarized in Table 3. In fact,
iodobenzene reacted with various olefins and gave the corresponding products with
86–96% yields in a short time (Table 3, 3a–3f). From the GC=MS spectra, we found
the doubly substituted product of 1.4% exists when 2-BrC6H4 I reacts with excess
olefin, but the C-I bond is the main reaction position (3d–3f). 2-Methylsulfanyl iodo-
benzene (3r) yielded 35%, probably because of the steric effect of the S-methyl group.
Aryl bromides proceeded from moderate to satisfactory yields (3g–3l). The reactant,
having an electron-withdrawing group (3j–3l), reacted better and gave greater yield
than those having an electronic-donating group (3g–3i). Similar conditions brought
Table 2. Effect of different bases on the Heck reaction in
ethanol=watera
Entry
Base
Yield (%)b
1
2
3
4
5
6
KOH
NaOH
Mix
Mix
Mix
81
Na2CO3
NaHCO3
KH2PO4
DBU
86
78
aReaction condition: 3 mmol PhI, 3.3 mmol methyl acry-
late, 8 mmol base, 3 mol% Pd=C, ethanol 6 ml, and water
4 ml, reflux at 80 ꢀC for corresponding time by GC.
bIsolated yield.

HECK REACTIONS IN AQUEOUS SYSTEM
1063
Table 3. Heck reaction of aryl or heteraryl halides with olefinsa
Compound
ArX
Olefinb
Time (h)
Yieldc (%)
3a
3b
3c
3d
3e
3f
C6H5I
C6H5I
C6H5I
MA
BA
1.5
1.5
2.0
1.5
1.5
2.0
4.0
4.0
8.0
2.0
2.0
2.0
4.0
4.0
6.0
8.0
8.0
6.0
24
96
93
PTEA
MA
BA
86
2-BrC6H4I
2-Br C6H4I
2-Br C6H4I
92d
94d
87d
90
PTEA
MA
BA
3g
3h
3i
4-CH3C6H4Br
4-CH3C6H4Br
4-CH3C6H4Br
3-NO2C6H4Br
3-NO2C6H4Br
3-NO2C6H4Br
2-Bromothiophene
2-Bromothiophene
2-Bromothiophene
4-NO2C6H4Cl
4-NO2C6H4Cl
2-CH3SC6H4I
C6H5Cl
85
82
PTEA
MA
BA
3j
94
93
3k
3l
PTEA
MA
BA
89
89
3m
3n
3o
3q
3p
3r
3a
85
80
PTEA
MA
BA
87
88
MA
MA
35
Trace
aReaction condition: 3 mmol ArX, 3.3 mmol olefin, 8 mmol K2HPO4, and 3 mol % Pd=C, aqueous
two-phase system (10 mL) reflux at 80 ꢀC for corresponding time by GC or TLC.
bMA: CH2 ¼ CHCO2CH3, BA: CH2 ¼ CHCO2(Bu-n), PTEA: CH2 ¼ CHCO2CH2CH2SPh.
cIsolated yield.
dExit about 1.4–2.0% double-substituted product from the GC=MS.
about the coupling of heteroaryl substrates such as 2-bromothiophene, which also
gave a moderate yield of 80–89%. Unfortunately, aryl chloride did not react well,
even when prolonging the reaction time at high temperature, except 1-chloro-4-
nitrobenzene (3p, 3q). All of the reactions were clean, and (E)-cinnamates were the
only products.
Pd=C remained completely in the ATPS after the reaction, so it could be
reused. Iodobenzene and methyl acrylate were chosen as reactants. After the Pd=C
was filtered out of the first reaction, the catalyst was irradiated by ultrasound for
0.5 h at room temperature in pure water. Then another portion of iodobenzene
and methyl acrylate was added. The procedure was repeated four times, and the
catalyst system proceeded well with a little loss of activity (Table 4, entry 1, runs
1–5). When we decreased the amount of Pd=C to 1.5 mol%, the reaction still
Table 4. Recycling of the catalyst system
Isolated yield (%)
Entry
Run 1
Run 2
Run 3
Run 4
Run 5
1
2a
94
84
90
76
82
70
74
62
78
60
aIn entry 2, 1.5 mol% Pd=C was used.

1064
Y.-Q. YUAN AND S.-R. GUO
proceeded well, and good yields were obtained in the following four runs (Table 4,
entry 2, runs 1–5).
CONCLUSIONS
In summary, an efficient ATPS for the Heck-type cross-coupling reaction has
been developed. In the presence of Pd=C, coupling of various aryl halides with ole-
fins were carried out efficiently to afford the desired products in moderate to excel-
lent yields. The procedure is operationally simple and comparable. The use of an
ATPS reaction medium and traditional Pd catalysts promise further opportunities
in batch processing and catalyst recycling.
EXPERIMENTAL
1
All reagents were used as received. H NMR and 13C NMR were recorded at
300 MHz and 75 MHz with a Bruker Avance 300 spectrometer. Chemical shifts are
reported in parts per million (ppm) using tetramethylsilane (TMS) as an internal
standard. Infrared (IR) spectra were obtained using a Bruker Equinox 55 Fourier
transform (FT)–IR spectrophotometer in KBr pellets. Melting points were obtained
with a XT4A melting-point apparatus and were uncorrected. GC analyses were
conducted using a Trace GC=Thermo Finnigan equipped with an SE-54 capillary
column (25 m) and an FID detector. Melting points were determined by using a
Buchi B-540 melting-point apparatus and are uncorrected.
¨
Aryl or heteroaryl halide (3 mmol), MA (3.3 mmol, BA or PTEA) (see Note b
in Table 3 for MA, BA, and PTEA definitions), 6 mL ethanol, 4 mL water, 1.4 g
K2HPO4, and 5% Pd=C (0.09 mmol) were placed in a 25-ml, two-necked flask.
The mixture was heated and refluxed to about 80 ꢀC in an air atmosphere for the
required time with magnetic stirring. After cooling to room temperature, the mixture
was filtered to recycle the catalyst, and the residue mixture fell into two phases auto-
matically. The supernatant phase, which contains 96% of the product was separated
out, and then another 6 mL were added to extract the residue (about 4% of product
in the water phase), which was dried over Na2SO4. The solvent was filtered and
evaporated. The product was purified by chromatography on silica (eluent: EtOAc=
petroleum ether ¼ 1:15). The purity of the isolated product was determined by GC
1
analysis or H NMR.
(E)-Methyl Cinnamate (3a)
1
White solid, mp 35–36 ꢀC (lit.[17] 34–35 ꢀC); H NMR (CDC13, 300 MHz) d:
7.70 (d, J ¼ 15.9 Hz, 1H), 7.50–7.53 (m, 2H), 7.37–7.42 (m, 3H), 6.45 (d, J ¼ 15.9 Hz,
Hz, 1H), 3.80 (s, 3H); 13C NMR (75 MHz, CDCl3) d: 167.4, 144.8, 134.4, 130.3,
128.9, 128.1, 117.8, 51.6; IR (KBr) n: 2365, 1708, 1632, 1152, 856 cmꢁ1
(E)-n-Butyl Cinnamate (3b)
.
Oil;[18,19] 1H NMR (CDCl3, 300 MHz) d: 7.79 (d, J ¼ 16.0 Hz, 1H), 7.61–7.63
(m, 2H), 7.46–7.49 (m, 3H), 6.55 (d, J ¼ 16.0 Hz, 1H), 4.33 (t, J ¼ 6.6 Hz, 2H),

HECK REACTIONS IN AQUEOUS SYSTEM
1065
1.80–1.85 (m, 2H), 1.48–1.61 (m, 2H), 1.07 (t, J ¼ 7.3 Hz, 3H); 13C NMR (75 MHz,
CDCl3) d: 167.0, 144.5, 134.5, 130.2, 128.8, 128.0, 118.3, 64.4, 30.8, 19.2, 13.7; IR
(film) n: 3068, 2959, 1712, 1638, 1467, 1327, 767, 684 cmꢁ1
.
(E)-2-(Phenylsulfanyl)ethyl Cinnamate (3c)
Oil; 1H NMR (CDC13, 300 MHz) d: 7.68 (d, J ¼ 16.1 Hz, 1H), 7.58 (d,
J ¼ 8.5 Hz, 1H), 7.23–7.53 (m, 10H), 6.42 (d, J ¼ 16.1 Hz, 1H), 4.40 (t, J ¼ 6.6 Hz,
2H), 3.25 (t, J ¼ 6.6 Hz, 2H); 13C NMR (75 MHz, CDCl3) d: 166.7, 145.3, 135.2,
134.3, 130.3, 129.2, 129.0, 128.8, 128.2, 126.6, 117.7, 63.1, 32.5; IR (film) n: 3038,
2825, 1716, 1618, 1469, 1121, 749, 594 cmꢁ1. Anal. calcd. for C17H16O2S: C, 71.80;
H, 5.67. Found: C, 71.83; H, 5.68.
(E)-Methyl 2-Bromocinnamate (3d)
Oil;[20] 1H NMR (CDC13, 300 MHz) d: 8.06 (d, J ¼ 15.9 Hz, 1H), 7.60–7.64 (m,
2H), 7.34 (t, J ¼ 7.4 Hz, 1H), 7.21–7.25 (m, 1H), 6.40 (d, J ¼ 15.9 Hz, 1H), 3.83 (s,
3H); 13C NMR (75 MHz, CDCl3) d: 166.8, 143.2, 134.5, 133.4, 131.2, 127.7, 127.1,
125.3, 120.7, 51.9; IR (KBr) n: 2365, 1708, 1632, 1152, 856 cmꢁ1. Anal. calcd. for
C10H9BrO2: C, 49.82; H, 3.76. Found: C, 49.83; H, 3.73.
(E)-n-Butyl 2-Bromocinnamate (3e)
Oil;[21] 1H NMR (CDC13, 300 MHz) d: 8.04 (d, J ¼ 15.9 Hz, 1H), 7.61 (d,
J ¼ 8.5 Hz, 2H), 7.32 (t, J ¼ 7.4 Hz, 1H), 7.19 – 7.25 (m, 1H), 6.39 (d, J ¼ 15.9 Hz,
1H), 4.23 (t, J ¼ 6.6 Hz, 2H), 1.62 – 1.75 (m, 2H), 1.39 – 1.50 (m, 2H), 0.97 (t,
J ¼ 7.3 Hz, 3H); 13C NMR (75 MHz, CDCl3) d: 166.5, 143.1, 134.8, 133.5, 131.1,
128.0, 127.3, 126.5, 121.1, 64.2, 31.1, 19.1,13.4; IR (KBr) n: 2808, 2306, 1695,
1605, 1158, 852, 714 cmꢁ1. Anal. calcd. for C13H15BrO2: C, 55.14; H, 5.34. Found:
C, 55.12; H, 5.38.
(E)-2-(Phenylsulfanyl)ethyl 2-Bromocinnamate (3f)
1
Oil; H NMR (CDC13, 300 MHz) d: 8.08 (d, J ¼ 16.1 Hz, 1H), 7.58–7.64 (m,
2H), 7.44 (d, J ¼ 7.5 Hz, 2H), 7.19–7.36 (m, 5H), 6.38 (d, J ¼ 16.1 Hz, 1H), 4.40 (t,
J ¼ 6.6 Hz, 2H), 3.25 (t, J ¼ 6.6 Hz, 2H); 13C NMR (75 MHz, CDCl3) d: 166.1,
143.6, 135.0, 134.4, 133.5, 131.3, 129.9, 129.1, 127.8, 127.7, 126.6, 125.4, 120.4,
63.1, 32.4; IR (KBr) n: 2816, 2351, 1702, 1612, 1155, 974, 856, 658 cmꢁ1. Anal. calcd.
for C17H15BrO2S: C, 56.21; H, 4.16. Found: C, 56.23; H, 4.18.
(E)-Methyl 3-p-Tolyl Acrylate (3g)
White solid;[17,18] mp 56.5–57.4 ꢀC (lit.[21] 60–62 ꢀC); 1H NMR (CDCl3,
300 MHz) d: 7.63 (d, J ¼ 16 Hz, 1H), 7.44 (d, J ¼ 8.1 Hz, 2H), 7.21 (d, J ¼ 7.9 Hz,
2H), 6.46 (d, J ¼ 16 Hz, 1H), 3.82 (s, 3H), 2.3 (s, 3H); 13C NMR (CDCl3) d: 167.5,
144.8, 140.6, 131.6, 129.5, 128.0, 116.6, 51.6, 21.4; IR (KBr) 2922, 1709, 1631,
1168 cmꢁ1
.

1066
Y.-Q. YUAN AND S.-R. GUO
(E)-n-Butyl 3-p-Tolyl Acrylate (3h)
Oil;[18] 1H NMR (CDCl3, 300 MHz) d: 7.75 (d, J ¼ 16.0 Hz, 1H), 7.53 (d,
J ¼ 8.0 Hz, 2H), 7.29 (d, J ¼ 8.0 Hz, 2H), 6.50 (d, J ¼ 16.0 Hz, 1H), 4.20
(t, J ¼ 6.7 Hz, 2H), 2.48 (s, 3H), 1.75–1.85 (m, 2H), 1.51–1.61 (m, 2H), 1.08 (t,
J ¼ 7.4 Hz, 3H);13C NMR (75 MHz, CDCl3) d: 13.8, 19.3, 21.5, 30.8, 64.4, 117.3,
128.1, 129.7, 131.9, 140.7, 144.6, 167.3; IR (film) n: 3015, 2959, 1712, 1608, 1514,
983, 813 cmꢁ1
.
(E)-2-(Phenylthio)ethyl 3-p-Tolyl Acrylate (3i)
Oil; 1H NMR (CDC13, 300 MHz) d: 7.63 (d, J ¼ 16.1 Hz, 1H), 7.50 (d,
J ¼ 8.5 Hz, 2H), 7.45 (d, J ¼ 8.4 Hz, 2H), 7.23–7.53 (m, 5H), 6.46 (d, J ¼ 16.1 Hz,
1H), 4.40 (t, J ¼ 6.6 Hz, 2H), 3.25 (t, J ¼ 6.6 Hz, 2H); 13C NMR (75 MHz, CDCl3)
d: 166.5, 145.5, 135.2, 134.9, 130.5, 130.2, 129.0, 128.8, 128.1, 126.2, 114.1, 63.1,
32.5, 18.5; IR (KBr) n: 3035, 2908, 2865, 1609, 1445, 965, 819, 756, 693 cmꢁ1. Anal.
calcd. for C18H18O2S: C, 72.45; H, 6.08. Found: C, 72.46; H, 6.03.
(E)-Methyl 3-(3-Nitrophenyl)acrylate (3j)
White solid;[21] mp 115–116 ꢀC (lit.[22] 113–114 ꢀC); 1H NMR (CDC13,
300 MHz) d: 8.36 (s, 1H), 8.22 (d, J ¼ 8.0 Hz, 1H), 7.82 (d, J ¼ 7.6 Hz, 1H), 7.70
(d, J ¼ 16.0 Hz, 1H), 7.58 (t, J ¼ 8.5 Hz, 1H), 6.57 (d, J ¼ 16.0 Hz, 1H), 3.83 (s,
3H); 13C NMR (75 MHz, CDCl3) d: 166.6, 148.7, 141.9, 136.1, 133.6, 129.9, 124.5,
122.4, 120.9, 52.0; IR (KBr) n: 2819, 2512, 1705, 1595, 1515, 1343, 1155, 858 cmꢁ1
.
(E)-n-Butyl 3-(3-Nitrophenyl)acrylate (3k)
1
White solid, mp 48–49 ꢀC (lit.[22,23] 47–48 ꢀC); H NMR (CDC13, 300 MHz) d:
8.38 (s, 1H), 8.23 (d, J ¼ 8.0 Hz, 1H), 7.83 (d, J ¼ 7.6 Hz, 1H), 7.71 (d, J ¼ 16.0 Hz,
1H), 7.59 (t, J ¼ 8.5 Hz, 1H), 6.57 (d, J ¼ 16.0 Hz, 1H), 4.24 (t, J ¼ 6.6 Hz, 2H),
1.66–1.75 (m, 2H), 1.38–1.51 (m, 2H), 0.97 (t, J ¼ 7.5 Hz, 3H); 13C NMR
(75 MHz, CDCl3) d: 166.2, 148.7, 141.6, 136.3, 133.6, 129.0, 124.4, 122.4, 121.6,
64.8, 30.7, 19.1, 13.7; IR (KBr) n: 2851, 2516, 2313, 1709, 1645, 1550, 1321,
958 cmꢁ1
.
(E)-2-(Phenylthio)ethyl 3-(3-Nitrophenyl)acrylate (3l)
White solid, mp 65–66 ꢀC; 1H NMR (CDC13, 300 MHz) d: 8.36 (s,1H), 8.25 (d,
J ¼ 8.1 Hz, 1H), 7.81 (d, J ¼ 8.4 Hz, 1H), 7.66 (d, J ¼ 16.3 Hz, 1H), 7.58 (d,
J ¼ 8.5 Hz, 1H), 7.45 (d, J ¼ 8.5 Hz, 2H), 7.21–7.39 (m, 3H), 6.50 (d, J ¼ 16.3 Hz,
1H), 4.42 (t, J ¼ 6.6 Hz, 2H), 3.25 (t, J ¼ 6.6 Hz, 2H); 13C NMR (75 MHz, CDCl3)
d: 165.8, 148.7, 142.2, 136.1, 135.1, 133.6, 130.1, 129.9, 129.1, 126.7, 124.6,
122.5,120.8, 63.6, 32.6; IR (KBr) n: 3025, 1709, 1602, 1508, 1339, 958, 850,
755 cmꢁ1. Anal. calcd. for C17H15NO4S: C, 61.99; H, 4.59. Found: C, 61.95; H, 4.62.

HECK REACTIONS IN AQUEOUS SYSTEM
1067
(E)-Methyl 3-(Thiophen-2-yl)acrylate (3m)
Oil;[23,24] 1H NMR (300 MHz, CDCl3) d: 7.68 (d, J ¼ 16.1 Hz, 1H), 7.32 (d,
J ¼ 5.2 Hz, 1H), 7.23 (d, J ¼ 5.6 Hz, 1H), 7.04 (dd, J ¼ 5.2 Hz; J ¼ 5.6 Hz, 1H), 6.23
(d, J ¼ 16.1 Hz, 1H), 3.85 (s, 3H); 13C NMR (75 MHz, CDCl3) d: 165.5, 141.3,
139.8, 130.2, 128.8, 128.2, 116.3, 52.6; IR (film) n: 2952, 1701, 1624, 1306 cmꢁ1
.
(E)-n-Butyl 3-(Thiophen-2-yl)acrylate (3n)
Oil;[23,25] 1H NMR (300 MHz, CDCl3) d: 7.76 (d, J ¼ 15.7 Hz, 1H), 7.35 (d,
J ¼ 4.9 Hz, 1H), 7.23 (d, J ¼ 3.4 Hz, 1H), 7.04 (dd, J ¼ 3.7 Hz; J ¼ 6.7 Hz, 1H), 6.23
(d, J ¼ 15.7 Hz, 1H), 4.18 (t, J ¼ 6.6 Hz, 2H), 1.72–1.62 (m, 2H), 1.48–1.36 (m,
2H), 0.95 (t, J ¼ 7.4 Hz, 3H);13C NMR (75 MHz, CDCl3) d: 167.3, 140.0, 137.3,
131.3, 128.7, 128.5, 117.5, 64.8, 31.2, 19.6, 14.1; IR (film) n: 2959, 1708, 1628,
1316 cmꢁ1
.
(E)-2-(Phenylthio)ethyl 3-(Thiophen-2-yl)acrylate (3o)
1
Oil; H NMR (300 MHz, CDCl3) d: 7.61 (d, J ¼ 15.9 Hz, 1H), 7.52–7.45 (m,
2H), 7.36 (q, J ¼ 3.4 Hz, J ¼ 6.8 Hz, 1H), 7.04 (d, J ¼ 8.2 Hz, 2H), 6.42 (d,
J ¼ 15.9 Hz, 1H), 6.28–6.21 (m, 3H), 4.25 (t, J ¼ 6.6 Hz, 2H), 3.25 (t, J ¼ 6.6 Hz,
2H); 13C NMR (75 MHz, CDCl3) d: 166.8, 141.2, 139.9, 133.2, 130.5, 129.9, 129.2,
128.8, 128.0, 124.6, 116.3, 64.8, 31.2; IR (film) n: 2925, 1716, 1626, 1306,
983 cmꢁ1. Anal. calcd. for C15H14O2S2: C, 62.04; H, 4.86. Found: C, 62.02; H, 4.88.
(E)-Methyl 3-(4-Nitrophenyl)acrylate (3p)
Light yellow solid, mp 132.3–133.5 ꢀC (lit.[24,26] 133–135 ꢀC); 1H NMR (CDCl3,
300 MHz) d: 8.25 (d, J ¼ 8.8 Hz, 2H), 7.73 (d, J ¼ 16.3 Hz, 1H), 7.69–7.66 (m, 2H), 6.65
(d, J ¼ 16.2 Hz, 1H), 3.83 (s, 3H); 13C NMR (CDCl3) d: 166.4, 148.5, 141.9, 140.5,
128.6, 124.2, 122.1, 52.1; IR (KBr) IR: 2959, 1709, 1641, 1599, 1518, 1343 cmꢁ1
.
(E)-n-Butyl 3-(4-Nitrophenyl)acrylate (3q)
1
Light yellow solid, mp 62.8–65.3 ꢀC (lit.[24,27] 64–65 ꢀC); H NMR (CDCl3,
300 MHz) d: 8.25 (d, J ¼ 8.8 Hz, 2H), 8.05 (d, J ¼ 8.4 Hz, 2H), 7.78 (d, J ¼ 16.1 Hz,
1H), 6.86 (d, J ¼ 16.1 Hz, 1H), 4.14 (t, J ¼ 6.8 Hz, 2H), 1.65–1.70 (q, J ¼ 6.8 Hz,
2H), 1.40–1.51 (m, 2H), 1.07 (t, J ¼ 7.2 Hz, 3H); IR (KBr) n: 3058, 2958, 1709,
1601, 1493, 1308, 982, 759 cmꢁ1
.
(E)-Methyl 3-(2-(Methylthio)phenyl)acrylate (3r)
Oil; 1H NMR (CDC13, 300 MHz) d: 8.21 (d, J ¼ 15.8 Hz, 1H), 7.54 (d,
J ¼ 8.0 Hz, 1H), 7.27–7.35 (m, 2H), 7.22 (t, J ¼ 8.5 Hz, 1H), 6.40 (d, J ¼ 15.8 Hz,
1H), 3.83 (s, 3H), 2.49 (s, 3H); 13C NMR (75 MHz, CDCl3) d: 167.2, 141.8, 139.4,
134.8, 130.3, 127.5, 127.1, 125.7, 119.7, 51.7, 16.7; IR (KBr) n: 2812, 2356, 1692,
1602, 1156, 858, 765 cmꢁ1. Anal. calcd. for C11H12O2S: C, 63.43; H, 5.81. Found:
C, 63.47; H, 5.86.

1068
Y.-Q. YUAN AND S.-R. GUO
ACKNOWLEDGMENTS
This work was supported by the Natural Science Foundation of Zhejiang
Province, China (Project Y407240), and the Key Science Foundation of Lishui
University (Project KY07002).
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