Ligand-free indium(III)-catalyzed Heck reaction

Article abstract of DOI:10.1016/j.tet.2013.07.019

A novel ligand-free indium(III)-catalyzed Heck reaction of various aryl iodides with olefins has been developed. As a result, a set of the corresponding E-internal olefins was obtained selectively in high to excellent yields. The reaction condition is tolerant to air, in accordance with the concept of modern green chemistry.

Full text of DOI:10.1016/j.tet.2013.07.019

Tetrahedron 69 (2013) 7925e7930
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Ligand-free indium(III)-catalyzed Heck reaction
,
a
a
b
Pei Liu a, Ying-ming Pan a , Kun Hu , Xiao-chao Huang , Ying Liang ,
*
,
Heng-shan Wang a
*
a Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, Ministry of Education of China, School of Chemistry & Chemical
Engineering of Guangxi Normal University, Guilin 541004, People’s Republic of China
b School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 15 May 2013
Received in revised form 28 June 2013
Accepted 8 July 2013
Available online 12 July 2013
A novel ligand-free indium(III)-catalyzed Heck reaction of various aryl iodides with olefins has been
developed. As a result, a set of the corresponding E-internal olefins was obtained selectively in high to
excellent yields. The reaction condition is tolerant to air, in accordance with the concept of modern green
chemistry.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
CeH activation
Heck reaction
Indium
Alkenes
Aryl iodides
1. Introduction
preliminary experiments, in which those substrates were sub-
mitted to the standard conditions used for the indium(III)-
The coupling between an aryl halide and a terminal alkene,
widely known as the Heck reaction, has become one of the most
important tools in synthetic chemistry.1,2 As a result, many efficient
and selective catalytic systems have been developed for the Heck
cross-coupling reaction.3 However, the vast majority of the existing
protocols involve the use of palladium catalysts.4 The development
of improved procedures, in which less expensive, ligand-free and
more sustainable catalysts are used, has remained an elusive goal.
In this respect, indium catalysts stand out as valuable alternatives
to those transition metals used in Heck reactions. The use of indium
salts to perform established transition-metal-catalyzed reactions
has gained significant attention because of their numerous ad-
vantages, namely, their relatively low cost, minimal toxicity, se-
lectivity, and tolerance toward various functional groups, or
interesting chemical properties.5 To the best of our knowledge, an
indium catalyzed C(sp2)eC(sp2) coupling reaction involving a ter-
minal alkene and an aryl halide has not been reported so far.
In our previous research on indium(III)-catalyzed reactions of
CeC triple bonds,6 we have observed that the InCl3 possess a high
catalytic activity. Inspired by these findings, we envisaged that the
Heck reaction could be promoted by InCl3. To our delight,
catalyzed process revealed that the target products were obtained
in good yields.
2. Results and discussion
To identify the optimal conditions for the Heck reaction, a series
of catalysts, bases and solvents were screened (Table 1). Initially,
the coupling of styrene (1a) with phenyl iodide (2a) was selected as
a model system. The effects of the additives, such as organic and
inorganic bases, in the coupling reaction were investigated (Table 1,
entries 10e13). When using K2CO3 or DMAP as base, 3aa was ob-
tained in good yields (Table 1, entries 10 and 11). Especially, in the
presence of CH3COONa, the yield of product 3aa was up to 96%
(Table 1, entry 1). Therefore, CH3COONa was selected as the base for
further screening reactions. When In(OTf)3, CuI, or Cu(OAc)2 was
used, the reaction was obviously inhibited (Table 1, entries 2e4). In
addition, in the presence of other metal catalysts, such as AgOTf,
FeCl3, InCl2, and BiCl3, most of the starting material 1a was re-
covered (Table 1, entries 5e9). Further optimization suggested that
solvents had a strong effect on this process. When this reaction was
performed in CH3NO2 or DMA, the product 3aa was not obtained at
all (Table 1, entries 14 and 15). Moreover, in other solvents, such as
DMSO, PhCl, and PhCH3, the yields of 3aa dramatically decreased to
28e50% (Table 1, entries 16e18). On the basis of the above
* Corresponding authors. E-mail addresses: panym2013@hotmail.com (Y.-ming
Pan), wang_hengshan@yahoo.com.cn (H.-shan Wang).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.07.019

7926
P. Liu et al. / Tetrahedron 69 (2013) 7925e7930
Table 1
experiments, the optimized reaction conditions are summarized as
follows: 5 mol % InCl3, 1 equiv of CH3COONa, and in DMF.
Screening conditions for Heck reaction between styrene (1a) and phenyl iodide (2a)a
With the optimal conditions in hand, the scope of the substrates
was investigated. Typical results are shown in Table 2. Promoted by
InCl3, almost all of the alkyl- and aryl-substituted alkenes pro-
cessed smoothly under the optimal conditions. The terminal aryl
alkenes 1b and 1c possessing an electron-donating group at the
aryl ring (R¼2-MeC6H4, 4-MeC6H4) reacted with-out a hitch and
afforded the desired products 3ab and 3ac in 94% and 93% yields,
respectively (Table 2, entries 3ab and 3ac). Substrates 1d and 1f,
possessing an electron-withdrawing group (R¼4-FC6H4, 4-BrC6H4)
at the benzene ring, also reacted smoothly and afforded the desired
products 3ad and 3af in 85% and 90% yields, respectively (Table 2,
entries 3ad and 3af). It was noted that aryl-substituted alkenes
bearing a strong electron-withdrawing group on the benzene ring
(R¼C6F5) treated with phenyl iodide 2a afford the desired product
3ae in high yield (Table 2, entry 3ae). Obviously, electron-rich ter-
minal alkenes provided the desired products in higher yields than
electron-poor terminal alkenes did. To our delight, the terminal
alkyl alkenes 1j and 1k in the presence of InCl3 also gave the
products 3aj and 3ak in 75% and 80% yields, respectively (Table 2,
entries 3aj and 3ak). Very interestingly, the reaction of substrate 2-
methyl-3-butene-2-ol 1g and phenyl iodide afforded the un-
expected product 3ag (Table 2, entry 3ag). Additionally, alkenes
bearing polycyclic aromatic substituents, such as 2-
vinylnaphthalene 1h were found to give the corresponding prod-
I
Cat., base, solvent
140 oC, 24 h
2a
Catalyst
3aa
1a
Entry
Solvent
Base
Yieldb (%)
1
2
3
4
5
7
8
9
InCl3
In(OTf)3
CuI
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMA
CH3NO2
DMSO
PhCl
CH3COONa
CH3COONa
CH3COONa
CH3COONa
CH3COONa
CH3COONa
CH3COONa
CH3COONa
K2CO3
DMAP
Cs2CO3
NaHCO3
CH3COONa
CH3COONa
CH3COONa
CH3COONa
CH3COONa
CH3COONa
96
65
18
16
0
0
0
0
78
68
45
62
0
Cu(OAc)2
AgOTf
FeCl3
InCl2
BiCl3
InCl3
InCl3
InCl3
InCl3
InCl3
InCl3
InCl3
InCl3
InCl3
d
10
11
12
13
14
15
16
17
18
19
0
50
45
28
0
PhCH3
DMF
a
Reaction conditions: styrene 1a (0.3 mmol), phenyl iodide 2a (0.45 mmol),
catalyst (5 mol % to 1a), base (1 equiv to 1a), solvent (2.0 mL), 140 ꢀC, 24 h.
b
Isolated yield of pure product based on 1a.
ucts 3ah in excellent yield (Table 2, entry 3ah).
A mono-
substitution on the ortho- and para-position of aryl olefins had no
Table 2
Ligand-free indium-catalyzed Heck reaction with alkenes 1 and 2aa
96% 3aa
94% 3ab
93% 3ac
85% 3ad
80% 3ae
90% 3af
75% 3agb
90% 3ah
86% 3ai
75% 3aj
80% 3akb
94% 3alb
a Reaction conditions: alkenes 1 (0.3 mmol), phenyl iodide 2a (0.45 mmol), InCl3 (5 mol % to 1a),
CH3COONa (1 equiv to 1a), DMF (2.0 mL), 140 oC, 24 h. Isolated yield of pure product based on
1a. b The reactions were carried out in sealed tubes. c Only E isomer was observed by 1H NMR.

P. Liu et al. / Tetrahedron 69 (2013) 7925e7930
7927
effect on the yields of the reaction (Table 2, entries 3ab and 3ac).
This method was also successful with ethyl acrylate to afford the
corresponding E-internal olefin 3al in 94% yield (Table 2, entry 3al).
The steric effect in our system was then examined. 1,1-
Diphenylethylene 1i was found to give the corresponding product
3ai in excellent yield (Table 2, entry 3ai).
Interestingly, the reaction of 4-chloro-alpha-methylstyrene
with 2a resulted in a mixture of the two regioisomeric products
3am and 3an (ratio¼1:1) in 44% and 44% yields, respectively
(Scheme 1).
provided corresponding products in high yields. In general, the
presence of the ortho-, meta-, and para-position substituents in
the electrophilic reagent did not hamper the reaction, which
proceeded smoothly in those cases, and afforded the corre-
sponding products 3 in 85e90% yields (Table 3, entries 3ba, 3ca,
3ad, 3da and 3ea). In addition, iodide bearing polycyclic aromatic
substituent, such as 1-iodonaphthalene led to the corresponding
E-internal olefin 3ah in 92% yield (Table 3, entry 3ah). Alkynes
bearing a heterocyclic aromatic substituent, such as 2-thienyl
iodide, and 3-pyridinyl iodide were also found to afford the de-
Scheme 1. Heck reaction of 4-chloro-alpha-methylstyrene 1o with phenyl iodide 2a.
Table 3
Ligand-free indium-catalyzed Heck reaction with styrene 1a and aryl iodides 2a
90% 3ba
85% 3ca
93% 3ad
89% 3da
85% 3ea
80% 3fa[b]
83% 3ga
92% 3ha
a
Reaction conditions: styrene 1 (0.3 mmol), aryl iodides 2a (0.45 mmol), InCl3 (5 mol % to 1a),
CH3COONa (1 equiv to 1a), DMF (2.0 mL), 140 oC, 24 h. Isolated yield of pure product based on
1a. b The reactions were carried out in sealed tubes. c Only E isomer was observed by 1H NMR.
Next, the scope of this indium-catalyzed Heck reaction was
sired products 3ga and 3fa in 83% and 80% yields, respectively
explored by treating styrene 1a with an array of aryl iodides
under the aforementioned optimized conditions. The reaction
was readily extended to a variety of aryl iodides in high yields, as
long as aryl iodides were used as the arylating agents. Un-
fortunately, phenyl bromide and phenyl tosylate were not suitable
for the reaction under the current conditions. The coupling re-
actions of both electron-rich and electron-deficient aryl iodides
(Table 3, entries 3fa and 3ga).
On the basis of the mechanism of previous reports7 and our
results, a possible catalytic cycle for this indium-catalyzed the re-
action of aryl iodides with olefins was proposed in Scheme 2. An
þ
immediate InCl2 4 was formed firstly and subsequently the re-
action of immediate 4 with phenyl iodide 1 afforded an organo-
indium intermediate 5. Then, the intermediate 5 could easily react

7928
P. Liu et al. / Tetrahedron 69 (2013) 7925e7930
Scheme 2. Possible reaction mechanism.
with styrene 2 to give intermediate 7.
b
-H elimination of the in-
with water (30 mL) and extracted with ethyl acetate (3ꢁ30 mL).
The combined organic layers were washed with water and brine,
dried over Na2SO4 and filtered. The solvent was removed under
vacuum. The residue was purified by flash column chromatography
to afford E-internal olefins 3.
termediate 7 occurred to give the desired products 3 and indium
species 8. Finally, indium species 8 could be deprotonated to the
þ
active intermediate InCl2 4 to finish the catalytic cycle.
3. Conclusion
4.3. Characterization of the compounds
In summary, we have developed an effective Heck reaction of
alkenes to aryl iodides, which was catalyzed by the commercially
available indium catalyst in the presence of CH3COONa. The alkyl-
and aryl-substituted alkenes with aryl iodides are readily available.
This reaction system can be carried out under mild conditions that
give a rapid access to a variety of E-internal olefin and will be ap-
pealing for industries.
4.3.1. (E)-Stilbenze (3aa).8 White solid; mp 123e124 ꢀC; 1H NMR
(500 MHz, CDCl3)
d
7.57 (d, J¼7.7 Hz, 4H), 7.43e7.40 (m, 4H),
7.33e7.30 (m, 2H), 7.17 (s, 2H); 13C NMR (125 MHz, CDCl3)
d
137.3,
þ
128.7, 127.6, 126.5; APCI HRMS exact mass calcd for (C14H13
quires m/z 181.10173, found m/z 181.10029.
)
re-
4.3.2. (E)-2-Methylstilbene (3ab).8 White solid; mp 158e159 ꢀC; 1H
NMR (500 MHz, CDCl3)
7.62 (d, J¼7.4 Hz,1H), 7.55 (d, J¼7.6 Hz, 2H),
7.40e7.34 (m, 3H), 7.31e7.20 (m, 4H), 7.02 (d, J¼16.2 Hz, 1H), 2.45 (s,
3H).13C NMR (125 MHz, CDCl3)
137.7, 136.4, 135.8, 130.4, 130.0, 128.7,
128.1, 127.6, 127.5, 126.5, 126.2, 125.3, 19.9. APCI HRMS exact mass
calcd for (C15H15
þ requires m/z 195.11738, found m/z 195.11545.
4. Experimental section
d
4.1. General methods and materials
d
All manipulations were performed under an air atmosphere
unless otherwise statement. Column chromatography was per-
formed on silica gel (300e400 mesh). NMR spectra were obtained
using a Bruker Avance 500 spectrometer (1H at 500 MHz and 13C at
125 MHz). Chemical shifts for 1H NMR spectra are reported in parts
per million (ppm) from tetramethylsilane with the solvent reso-
)
4.3.3. (E)-4-Methylstilbene (3ac).8 White solid; mp 120e121 ꢀC; 1H
NMR (500 MHz, CDCl3)
7.55 (d, J¼7.5 Hz, 2H), 7.46 (d, J¼8.0 Hz, 2H),
d
7.40 (t, J¼7.6 Hz, 2H), 7.29 (t, J¼7.3 Hz,1H), 7.21 (d, J¼7.9 Hz, 2H), 7.13
(d, J¼3.8 Hz, 2H), 2.41 (s, 3H).13C NMR (125 MHz, CDCl3)
d 137.5, 134.5,
nance as the internal standard (CDCl3: d 7.26 ppm). Chemical shifts
130.4, 129.4, 128.6, 127.7, 127.4, 126.4, 126.4, 21.2; APCI HRMS exact
for 13C NMR spectra are reported in parts per million (ppm) from
tetramethylsilane with the solvent as the internal standard (CDCl3:
mass calcd for (C15H15)
þ requires m/z 195.11738, found m/z 195.11586.
4.3.4. (E)-4-Fluorostilbene (3ad).8 White solid; mp 123e124 ꢀC; 1H
NMR (500 MHz, CDCl3) 7.54e7.49 (m, 4H), 7.41e7.38 (m, 2H),
7.32e7.29 (m, 1H), 7.12e7.03 (m, 4H). 13C NMR (125 MHz, CDCl3)
163.3 and 161.3, 137.1, 133.5, 128.7, 128.4 and 128.0, 127.9, 127.6,
d
77.0 ppm). High resolution mass spectra (HRMS) were recorded
on the Exactive Mass Spectrometer (Thermo Scientific, USA)
equipped with APCI ionization source.
d
d
4.2. General procedure for the E-internal olefin 3aae3an and
3bae3ga
127.4, 126.4, 115.7 and 115.5; APCI HRMS exact mass calcd for
(C14H12F)þ requires m/z 199.09230, found m/z 199.09111.
The reaction mixture of alkenes 1 (0.3 mmol), aryl iodides 2
(0.45 mmol), InCl3 (5 mol %), CH3COONa (1 equiv) and DMF (2 mL)
in a 10 mL dried flask was stirred at 140 ꢀC, and monitored peri-
odically by TLC. Upon completion, the reaction mixture was diluted
4.3.5. (E)-1,2,3,4,5-Pentafluoro-6-styrylbenzene (3ae).9 White solid;
mp 135e136 ꢀC; 1H NMR (500 MHz, CDCl3)
d
7.54 (d, J¼7.4 Hz, 2H),
7.46e7.33 (m, 4H), 6.99 (d, J¼16.8 Hz, 1H). 13C NMR (125 MHz,
CDCl3)
d 145.8, 138.8, 137.3, 136.5, 129.0, 128.9, 126.9, 124.6, 112.7;

P. Liu et al. / Tetrahedron 69 (2013) 7925e7930
7929
APCI HRMS exact mass calcd for (C14H8F5)þ requires m/z 271.05462,
found m/z 271.05481.
(m, 4H), 7.31e7.28 (m, 2H), 7.13e7.10 (m, 3H), 2.42 (s, 3H). 13C
NMR (125 MHz, CDCl3) 138.2, 137.4, 137.2, 128.8, 128.6, 128.6,
128.4, 127.5, 127.2, 126.5, 123.7, 21.42; APCI HRMS exact mass
d
4.3.6. (E)-4-Bromostilbene (3af).8 Yellow solid; mp 137e138 ꢀC; 1H
calcd for (C15H15
195.11630.
)
requires m/z 195.11738, found m/z
þ
NMR (500 MHz, CDCl3)
d 7.53e7.48 (m, 4H), 7.41e7.34 (m, 4H),
7.31e7.28 (m, 1H), 7.11 (d, J¼16.3 Hz, 1H), 7.04 (d, J¼16.3 Hz, 1H). 13C
NMR (125 MHz, CDCl3)
d
136.9,136.2,131.7,129.4,128.7,127.9,127.9,
4.3.15. (E)-1,3-Dimethyl-5-styrylbenzene (3ca). White solid; mp
145e146 ꢀC; 1H NMR (500 MHz, CDCl3)
7.55 (d, J¼7.4 Hz, 2H),
7.42e7.39 (m, 2H), 7.31e7.28 (m, 1H), 7.20 (s, 2H), 7.11 (d, J¼6.8 Hz,
2H), 6.96 (s, 1H), 2.39 (s, 6H). 13C NMR (125 MHz, CDCl3)
138.2,
137.6, 137.3, 129.5, 129.0, 128.7, 128.4, 127.5, 126.5, 124.5, 21.38; APCI
127.4, 126.5, 121.3; APCI HRMS exact mass calcd for (C14H12Br)þ re-
d
quires m/z 259.01224; 261.01019, found m/z 259.01227; 261.01019.
d
4.3.7. (E)-(3-Methylbuta-1,3-dienyl)benzene
(3ag).13 Colourless
7.47 (d, J¼7.5 Hz,
solid; mp 58e59 ꢀC; 1H NMR (500 MHz, CDCl3)
d
HRMS exact mass calcd for (C16H17)
þ requires m/z 209.13303, found
2H), 7.36 (t, J¼7.7 Hz, 2H), 7.29e7.25 (m, 1H), 6.92 (d, J¼16.1 Hz,1H),
m/z 209.13174.
6.57 (d, J¼16.1 Hz, 1H), 5.15 (s, 1H), 5.11 (s, 1H), 2.01 (s, 3H). 13C NMR
(125 MHz, CDCl3)
d
142.0, 137.4, 131.7, 128.7, 128.6, 127.4, 126.5,
4.3.16. (E)-2-Chlorostilbene (3da).8 White solid; mp 38e39 ꢀC; 1H
NMR (500 MHz, CDCl3)
7.71 (dd, J¼7.8, 1.4 Hz, 1H), 7.58e7.53 (m,
117.3, 18.6; APCI HRMS exact mass calcd for (C11H13
)
þ requires m/z
d
145.10173, found m/z 145.10117.
3H), 7.42e7.38 (m, 3H), 7.32e7.27 (m, 2H), 7.21 (td, J¼7.7, 1.5 Hz,
1H), 7.10 (d, J¼16.3 Hz, 1H). 13C NMR (125 MHz, CDCl3)
d 137.0,
4.3.8. 2-[(E)-2-Phenyl-1-ethenyl]naphthalene (3ah).10 White solid;
mp 147e149 ꢀC; 1H NMR (500 MHz, CDCl3)
7.90 (s, 1H), 7.87e7.85
135.4, 133.4, 131.2, 129.8, 128.7, 128.5, 128.0, 126.9, 126.8, 126.4,
124.7; APCI HRMS exact mass calcd for (C14H12Cl)þ requires m/z
215.06275, found m/z 215.06152.
d
(m, 3H), 7.79 (d, J¼8.4 Hz, 1H), 7.61 (d, J¼7.6 Hz, 2H), 7.50 (s, 1H),
7.43 (t, J¼7.5 Hz, 2H), 7.37e7.26 (m, 4H). 13C NMR (125 MHz, CDCl3)
d
137.3, 134.8, 133.7, 133.0, 129.0, 128.8, 128.7, 128.3, 128.0, 127.8,
4.3.17. (E)-3-Chlorostilbene (3ea).8 White solid; mp 72e73 ꢀC; 1H
127.7, 126.6, 126.5, 126.3, 125.9, 123.5; APCI HRMS exact mass calcd
for (C18H15
þ requires m/z 231.11738, found m/z 231.11583.
NMR (500 MHz, CDCl3) d 7.51e7.50 (m, 3H), 7.38e7.35 (m, 3H),
)
7.30e7.27 (m, 2H), 7.23 (t, J¼6.2 Hz, 1H), 7.11 (d, J¼16.3 Hz, 1H), 7.02
(d, J¼16.3 Hz, 1H). 13C NMR (125 MHz, CDCl3)
d 139.2, 136.8, 134.6,
4.3.9. 1,10,100-Ethene-1,1,2-triyltribenzene (3ai).11 White solid; mp
72e73 ꢀC; 1H NMR (500 MHz, CDCl3)
7.36e7.04 (m, 15H), 6.99 (s,
1H). 13C NMR (125 MHz, CDCl3)
143.4, 142.57, 140.3, 137.4, 130.4,
129.5, 128.6, 128.2, 128.2, 127.9, 127.6, 127.5, 127.4, 126.7; APCI
130.1, 129.8, 128.7, 128.0, 127.5, 127.2, 126.6, 126.3, 124.7; APCI
HRMS exact mass calcd for (C14H12Cl)þ requires m/z 215.06275,
found m/z 215.06168.
d
d
HRMS exact mass calcd for (C20H17
)
þ requires m/z 257.13303, found
4.3.18. (E)-2-Styrylpyridine (3fa).15 White solid; mp 92e93 ꢀC; 1H
m/z 257.13107.
NMR (500 MHz, CDCl3)
7.63e7.55 (m, 3H), 7.41e7.36 (m, 3H), 7.31e7.28 (m, 1H), 7.20e7.14
(m, 2H). 13C NMR (125 MHz, CDCl3)
156.1, 149.6, 136.6, 135.7,
132.8, 128.7, 128.3, 127.9, 127.1, 122.1, 121.8; APCI HRMS exact
mass calcd for (C13H12N)þ requires m/z 182.09697, found m/z
182.09583.
d
8.61 (d, J¼4.7 Hz, 1H), 7.68e7.65 (m, 1H),
4.3.10. (E)-1,3-Diphenylpropene (3aj).12 Yellowish oil; 1H NMR
(500 MHz, CDCl3) 7.38e7.35 (m, 2H), 7.32e7.28 (m, 4H), 7.25e7.18
d
d
(m, 4H), 6.47 (d, J¼15.8 Hz, 1H), 6.40e6.34 (m, 1H), 3.56 (d,
J¼6.7 Hz, 2H). 13C NMR (125 MHz, CDCl3)
d 140.2, 137.5, 131.1, 129.2,
128.7, 128.5, 128.3, 127.1, 126.2, 126.1, 39.3; APCI HRMS exact mass
calcd for (C15H15
)
þ requires m/z 195.11738, found m/z 195.11552.
4.3.19. (E)-2-Styrylthiophene (3ga).8 Yellow solid; mp 112e113 ꢀC;
1H NMR (500 MHz, CDCl3)
d
7.51 (d, J¼7.6 Hz, 2H), 7.39 (t, J¼7.7 Hz,
4.3.11. (E)-1-(3,3-Dimethylbut-1-enyl)benzene (3ak).14 White solid;
2H), 7.31e7.26 (m, 2H), 7.23 (t, J¼6.2 Hz, 1H), 7.11 (d, J¼3.4 Hz, 1H),
mp 84e85 ꢀC; 1H NMR (500 MHz, CDCl3)
7.36 (d, J¼7.3 Hz, 2H),
d
7.06e7.02 (m, 1H), 6.98 (d, J¼16.1 Hz, 1H). 13C NMR (125 MHz,
7.29 (t, J¼7.7 Hz, 2H), 7.19 (t, J¼7.3 Hz, 1H), 6.32e6.24 (m, 2H), 1.12
CDCl3) d 142.9, 137.0, 128.7, 128.3, 127.6, 126.3, 126.1, 124.3, 121.8;
(s, 9H), 13C NMR (125 MHz, CDCl3)
d
141.9, 138.1, 128.5, 126.7, 126.0,
APCI HRMS exact mass calcd for (C12H11S)þ requires m/z 187.05815,
found m/z 187.05727.
þ
124.6, 33.3, 29.6; APCI HRMS exact mass calcd for (C12H17
)
re-
quires m/z 161.13303, found m/z 161.13156.
4.3.20. (E)-1-Styrylnaphthalene (3ha).8 White solid; mp 68e69 ꢀC;
4.3.12. Ethyl(E)-cinnamate (3ai).8 Colourless liquid; 1H NMR
(500 MHz, CDCl3)
7.69 (d, J¼16.0 Hz, 1H), 7.52e7.50 (m, 2H),
1H NMR (500 MHz, CDCl3)
d
8.27 (d, J¼8.3 Hz, 1H), 7.95e7.76 (m,
d
4H), 7.65 (d, J¼7.6 Hz, 2H), 7.60e7.51 (m, 3H), 7.45 (t, J¼7.6 Hz, 2H),
7.38e7.36 (m, 3H), 6.43 (d, J¼16.1 Hz, 1H), 4.28e4.24 (m, 2H),
7.35 (t, J¼7.4 Hz, 1H), 7.20 (d, J¼16.0 Hz, 1H). 13C NMR (125 MHz,
1.35e1.31 (t, J¼7.2 Hz, 3H). 13C NMR (125 MHz, CDCl3)
d
166.9,144.5,
CDCl3) d 137.6, 135.0, 133.7, 131.7, 131.4, 128.7, 128.6, 128.0, 127.8,
134.4, 130.1, 128.8, 128.0, 118.2, 60.4, 14.2; APCI HRMS exact mass
126.7, 126.1, 125.8þ, 125.8, 125.7, 123.8, 123.6; APCI HRMS exact mass
calcd for (C11H13O2)þ requires m/z 177.09155, found m/z 177.09096.
calcd for (C18H15) requires m/z 231.11738, found m/z 231.11543.
4.3.13. (E)-1-Chloro-4-(1-phenylprop-1-en-2-yl)benzene (3am) and
1-chloro-4-(3-phenylprop-1-en-2-yl)benzene (3an). White solid;
Acknowledgements
mp 140e141 ꢀC; 1H NMR (500 MHz, CDCl3)
d
7.48 (d, J¼8.3 Hz, 2H),
We thank the Project 973 (2011CB512005), the National Natural
Science Foundation of China (41206077 and 81260472), Guangxi
Natural Science Foundation of China (2012GXNSFAA053027,
2011GXNSFD018010 and 2010GXNSFF013001) for financial
support.
7.41e7.35 (m, 8H), 7.31e7.28 (m, 5H), 7.24e7.21 (m, 3H), 6.85 (s,1H),
5.50 (s, 1H), 5.09 (s, 1H), 3.83 (s, 2H), 2.28 (s, 3H). 13C NMR
(125 MHz, CDCl3)
d 145.9, 142.4, 138.0, 136.3, 133.3, 132.9, 129.7,
129.1, 128.8, 128.4, 128.4, 127.5, 127.3, 126.7, 126.2, 115.0, 41.6, 29.7,
17.4; APCI HRMS exact mass calcd for (C15H14Cl)þ requires m/z
229.07840, found m/z 229.07664.
Supplementary data
4.3.14. (E)-3-Methylstilbene (3ba).8 White solid; mp 48e49 ꢀC;
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2013.07.019.
1H NMR (500 MHz, CDCl3)
d
7.55 (d, J¼7.3 Hz, 2H), 7.41e7.36

7930
P. Liu et al. / Tetrahedron 69 (2013) 7925e7930
172e186; (f) Wu, X.-F.; Anbarasan, P.; Neumann, H.; Beller, M. Angew. Chem.,
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