A Neutral Metal-Free System for Head-to-Tail Dimerization of Electron-Rich Alkenes

Article abstract of DOI:10.1055/s-0036-1589039

A neutral metal-free system for the head-to-tail dimerization of electron-rich alkenes with stoichiometric amount of BrCCl ₂ H and NaI is reported. This reaction proceeds under mild conditions with high efficiency and broad scope.

Full text of DOI:10.1055/s-0036-1589039

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
2017, 49, A–F
paper
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en
A.-Y. Luo et al.
Paper
Synthesis
A Neutral Metal-Free System for Head-to-Tail Dimerization of
Electron-Rich Alkenes
A-Yun Luo
BrCCl2H (2 equiv)
NaI (1.2 equiv)
Me
Yan Bao
Ar
Ar
Ar
MeCN, 90 °C, N2
Xiu-Fen Cheng
Xi-Sheng Wang*
Ar = electron-rich
(hetero)arenes
metal-free,
neutral conditions
20 examples
up to 99% yield
0
0
0
0
0-
0
0
3
2-
3
9
8
5-
6
6
9
Hefei National Laboratory for Physical Sciences at the Microscale and
Department of Chemistry, University of Science and Technology of
China, 96 Jinzhai Road, Hefei, Anhui 230026, P. R. of China
xswang77@ustc.edu.cn
Received: 30.03.2017
Accepted after revision: 05.05.2017
Published online: 20.06.2017
also promote the dimerization of alkenes with the aid of
P(OEt)3.6 In particular, most known reaction systems for the
head-to-tail dimerization of alkenes normally work only for
electron-deficient and -neutral alkenes, and thus dimeriza-
tion of electron-rich substrates remains to be demonstrat-
ed. Herein, we report an efficient, highly selective method
for the head-to-tail dimerization of electron-rich alkenes.
The reaction was performed in the presence of NaI and
BrCCl2H without using any expensive transition metal cata-
lysts in a neutral condition and exhibited mild conditions,
easy handling, and broad scope.
DOI: 10.1055/s-0036-1589039; Art ID: ss2017-h0208-op
Abstract A neutral metal-free system for the head-to-tail dimerization
of electron-rich alkenes with stoichiometric amount of BrCCl2H and NaI
is reported. This reaction proceeds under mild conditions with high effi-
ciency and broad scope.
Key words metal-free, head-to-tail, dimerization, electron-rich
alkenes, BrCCl2H
As the most abundant and low-cost petrochemical feed-
stocks, alkenes have been widely used in organic synthesis
for both academic research and industrial production. For
instance, alkenes have been used in different kinds of trans-
formations to make a wide range of important synthetic in-
termediates,1 or to produce a variety of polymers, which
could be further processed into diverse industrial products
such as rubber, cellulose, plastic, lubricant, etc.2 Dimeriza-
tion of readily available simple alkenes has been used as an
important method to produce higher alkenes for further
transformations, including three modes, named head-to-
head, head-to-tail, and tail-to-tail.3 Among all the three
ways, the head-to-tail dimerization attracted more atten-
tion for easy construction of an allylic carbon stereogenic
center. One approach for the head-to-tail dimerization of
alkenes is transition metal catalysis, in which nickel, cobalt,
palladium, and ruthenium have demonstrated high catalyt-
ic activity for the dimerization of a variety of styrenes.4
However, the requirement of expensive and/or toxic transi-
tion metal catalysts, phosphorus ligands, and some special
additives, definitely limited their applications in organic
synthesis. Meanwhile, Brønsted acid catalyzed dimeriza-
tion of alkenes,5 which represents an alternative metal-free
approach, is appealing due to the advantages of low cost,
nontoxicity, and easy handling. Additionally, iodine could
Our study commenced with 4-methoxystyrene (1a) as
the model substrate under nitrogen atmosphere at 90 °C. It
was interesting to find that the desired product 2a was ob-
tained in 24% yield when acetonitrile was used as the sol-
vent (Table 1, entry 1). To our delight, the yield could be im-
proved to 46% when 2 equivalents of BrCCl2H was added to
the reaction system (entry 2). The careful screening of the
analogues of BrCCl2H, including ICH2Cl, CHBr3, BrCH2Cl, and
CCl4 gave only low yield of less than 10% (entries 3–6). To
further improve the yield of this transformation, different
kinds of halides were added to the reaction as additives.
Notably, the addition of stoichiometric amount of iodides
increased the yield significantly, and sodium iodide afford-
ed the dimerization product 2a in 95% yield. In comparison,
the replacement of iodides with iodine gave none of the de-
sired product and bromides or chlorides gave only very low
yields, which indicated I– may play an important role in this
transformation. While solvent screening gave no higher
yields, the optimization of amounts of sodium iodide and
reaction time could further improve the yield to 99%. Con-
sidering the possible release of proton by BrCCl2H in the re-
action system, a number of Brønsted acids, including AcOH,
TfOH, HCl, and HBr were investigated, which showed 2
equivalents or 20 mol% of HCl could afford moderate yield,
but the addition of sodium iodide helped in no way to raise
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

B
A.-Y. Luo et al.
Paper
Synthesis
the yield. These results revealed that our new metal-free
system dimerize the alkenes in an interesting path different
from any known Brønsted acid promoted reaction system.
merization product was obtained from styrene analogue
bearing an electron-withdrawing substituent such as nitro
group. These results indicated that the electronic effect of
the substituents played an important role in the present di-
merization reaction. As shown in Scheme 1, while styrene-
based substrates installed with a 4-MeO on the phenyl ring
gave good results, halogen substituents including 2-F, 3-F,
3-Cl, and 3-Br were tolerated together with a 4-MeO sub-
stituent in the same phenyl ring, affording the dimerization
products in excellent yields (2h, 2k, 2l, 2m) under relatively
higher temperature (100 °C) and longer reaction time (24
h). Additionally, the methyl- and methylthio-substituted
styrenes gave the corresponding dimerization products in
relatively lower yields and required a higher temperature
(110–120 °C), possibly due to the weaker electron-donating
ability of methyl and methylthio groups in comparison to
methoxy group. Some electron-rich heteroaryl olefins were
also effective substrates and gave the dimerization prod-
ucts in excellent yields. Notably, 2-vinylthiophene and 1-vi-
nylpyrrolidin-2-one were also compatible with this reac-
tion to afford the dimerization products in moderate and
good yields, respectively.
Table 1 Optimization of Reaction Conditionsa
Me
additive I (2.0 equiv)
additive II (1.0 equiv)
MeO
solvent, 90 °C
N2, 24 h
MeO
OMe
1a
2a
Entry
Additive-I
Additive-II
Solvent
Yield (%)b
1
2
–
–
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
24
46
BrCCl2H
ICH2Cl
CHBr3
BrCH2Cl
CCl4
–
3
–
<10
<10
trace
8
4
–
5
–
6
–
7
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
BrCCl2H
AcOH
TfOH
TBAI
NaI
KI
75
8
95
9
93
1
The H NMR analysis of the mixture from the crude re-
10
11
12
13
14
15
16
17
18c
19
20
21
22
23d
24
25c,d
I2
0
action system with CD3CN as the solvent gave a new signal
at 7.603 ppm, which could also be detected by mixing
BrCCl2H and NaI in CD3CN accordingly. Further 1H NMR and
GC-MS analysis indicated an in situ-generated reagent such
as ICCl2H. To understand the mechanism of this alkene di-
merization reaction, a series of deuterium experiments
were next conducted. First, 1-methoxy-4-(vinyl-2,2-d2)
benzene (1a′) was synthesized and subjected to the stan-
dard conditions, which afforded a mixture of deuterated
and nondeuterated dimerization products. 1H NMR analysis
of this mixture showed that 18% and 16% of H were ob-
served on the 2- and 4-carbon, respectively (Scheme 2, eq.
1). Second, 1 and 2 equivalents of H2O were also added to
the reaction system, which revealed that the proportion of
hydrogen atom on the 2- and 4-carbon increased with the
amount of water in the reaction (Scheme 2, eqs. 2, 3). Final-
ly, the addition of 1 equivalent of D2O significantly raised
the ratio of deuterium atom on the 2- and 3-carbon of the
products (Scheme 2, eq. 4). Based on all these results, it is
speculated that a proton exchange occurred between the
substrates and water in the reaction, as the Brønsted acids
catalytic system did,5 but at this stage, the mechanism is
still unclear and remains to be explored.
LiBr
KCl
KBr
NaCl
NaI
NaI
NaI
NaI
–
12
17
12
18
MeNO2
toluene
DMF
87
trace
25
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
99
trace
N.D.
51
–
HCl
–
HBr
–
37
HCl
–
63
HCl
NaI
NaI
trace
52
HCl
a Reaction conditions: 1a (0.2 mmol, 1.0 equiv), additive-I (2.0 equiv), ad-
ditive-II (1.0 equiv), MeCN (1 mL), 90 °C, 24 h, N2.
b Isolated yield.
c NaI (1.2 equiv) was used; reaction time: 12 h.
d HCl (20 mol%) was used.
With the optimized conditions in hand, the scope and
limitations of this reaction were investigated and some re-
sults are summarized in Scheme 1. In general, vinylarenes
containing electron-donating groups were suitable sub-
strates and generated the corresponding products in mod-
erate to excellent yields. Thus, the dimerization of 4-MeO-,
2-MeO-, 4-Me-, 4-PhO-, 4-PhCH2O-, 4-MeS-substituted sty-
renes proceeded efficiently to give the desired 1,3-diaryl-
but-1-ene derivatives 2a–f in 53% to 99% yields. No di-
In summary, we have developed a neutral metal-free
system for the head-to-tail dimerization of electron-rich
alkenes with stoichiometric amount of BrCCl2H and NaI.
This novel transformation demonstrated mild conditions,
high efficiency, low cost, and environmental friendliness.
Further applications of this method will be reported in due
course.
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

C
A.-Y. Luo et al.
Paper
Synthesis
Me
BrCCl2H (2.0 equiv), NaI (1.2 equiv)
MeCN, N2
R
R
R
1
2
Me
Me
Me
OMe Me
OMe
MeO
OMe
Me
Me
PhO
OPh
OMe
2a, 90 °C, 12 h, 99%
2b, 90 °C, 18 h, 63%
2c, 110 °C, 24 h,70%
Me Me Me
2d, 90 °C, 12 h, 90%
Me
Me
F
Me
F
BzO
OBz
MeS
SMe
MeO
OMe
MeO
2e, 90 °C, 12 h, 86%
2f, 120 °C, 12 h, 53%
2g, 90 °C, 12 h, 89%
2h, 100 °C, 24 h, 84%
MeO
Me
OMe
Me
Me
Me
Me
Me
F
F
Cl
Cl
MeO
OMe
MeO
OMe
MeO
OMe
OMe
OMe
2i, 90 °C, 12 h, 49%
2j, 90 °C, 12 h, 88%
2k, 100 °C, 24 h, 89%
2l, 100 °C, 24 h, 85%
Me
Me
Me
Me
Br
Br
O
O
O
O
O
O
O
O
O
O
MeO
OMe
2m, 100 °C, 24 h, 84%
2n, 110 °C, 12 h, 83%
2o, 100 °C, 12 h, 83%
2p, 90 °C, 12 h, 90%
Me
OMe Me
OMe
Me
Me
O
O
MeO
MeO
OMe
OMe
S
N
N
S
MeO
OMe
OMe
OMe
2q, 90 °C, 12 h, 87%
2r, 90 °C, 12 h, 44%
2s, 90 °C, 12 h, 55%
2t, 90 °C, 12 h, 89%
Scheme 1 The substrate scope for the dimerization of alkenes. Reagents and conditions (unless otherwise noted): 1 (0.2 mmol, 1.0 equiv), CHBrCl2 (2.0
equiv), NaI (1.2 equiv), MeCN (1 mL), 90 °C, 12 h, N2. Isolated yields are shown.
b, 16% H
*
*
All the commercially available reagents were used as received. NMR
spectra were recorded on Bruker 400 MHz NMR spectrometer (400
MHz for 1H; 101 MHz for 13C). 1H NMR chemical shifts were deter-
mined relative to internal TMS at δ = 0.0 or at the signal of a residual
protonated solvent: CDCl3 δ = 7.26, CD3CN δ = 1.94. Chemical shifts
are reported in ppm and coupling constants (J) in hertz (Hz). Melting
points were measured on a Beijing Tektronix X-4 digital microscopic
melting point apparatus. High-resolution mass spectra (HRMS) were
acquired on a Water TOF-MS GCT Premier mass spectrometer.
D
(1)
standard conditions
D
MeO
a, 18% H
MeO
MeO
MeO
MeO
OMe
1a'
*
b, 59% H
D
(2)
standard conditions
D
D
*
MeO
MeO
H2O (1.0 equiv)
a, 63% H
OMe
1a'
1a'
For the preparation of substituted styrenes 1h,k–m,p, see the Sup-
porting Information.
*
b, 68% H
*
D
(3)
standard conditions
Dimerization of Alkenes; General Procedure
H2O (2.0 equiv)
a, 72% H
To a 25 mL of Schlenk tube was added NaI (36 mg, 0.24 mmol, 1.2
equiv) under air, then evacuated and backfilled with N2 (3 times). The
appropriate styrene 1 (0.2 mmol, 1.0 equiv), BrCCl2H (65.6 mg, 0.4
mmol, 2.0 equiv) and MeCN (1 mL) were added subsequently. The
Schlenk tube was then sealed with Teflon lined cap and immersed
into a preheated oil bath. After stirring for 12 h or 18 h or 24 h
(Scheme 1), the reaction mixture was cooled to r.t. and the solvent
was removed under vacuum. The residue was purified by flash col-
umn chromatography on silica gel to afford the desired product 2.
OMe
*
b, 10% H
*
D
(4)
standard conditions
D
MeO
D2O (1.0 equiv)
a, 6% H
OMe
1a'
Scheme 2 Deuterium experiments
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

D
A.-Y. Luo et al.
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Synthesis
(E)-4,4′-(But-1-ene-1,3-diyl)bis(methoxybenzene) (2a)7
Yield: 26.6 mg (99%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
1H NMR (400 MHz, CDCl3): δ = 7.29 (d, J = 8.8 Hz, 2 H), 7.19 (d, J = 8.8
Hz, 2 H), 6.87 (d, J = 8.8 Hz, 2 H), 6.84 (d, J = 8.8 Hz, 2 H), 6.34 (d, J =
16.0 Hz, 1 H), 6.23 (dd, J = 16.0, 6.4 Hz, 1 H), 3.80 (s, 6 H), 3.61–3.53
(m, 1 H), 1.43 (d, J = 7.2 Hz, 3 H).
1H NMR (400 MHz, CDCl3): δ = 7.27–7.23 (m, 3 H), 7.22–7.18 (m, 4 H),
7.17–7.16 (m, 1 H), 6.34 (d, J = 16.0 Hz, 1 H), 6.29 (dd, J = 16.0, 5.3 Hz,
1 H), 3.62–3.55 (m, 1 H), 2.47 (s, 3 H), 2.46 (s, 3 H), 1.43 (d, J = 7.2 Hz,
3 H).
13C NMR (101 MHz, CDCl3): δ = 142.8, 137.1, 136.0, 134.7 (2 C), 128.1,
128.0, 127.3, 126.9, 126.7, 42.2, 21.3, 16.4, 16.1.
HRMS (EI): m/z calcd for C18H20S2 [M]+: 300.1006; found: 300.1014.
13C NMR (101 MHz, CDCl3): δ = 158.9, 158.1, 138.1, 133.6, 130.6,
128.3, 127.7, 127.3, 114.0, 113.9, 55.4, 41.8, 21.6.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(1-methoxy-3-methylbenzene) (2g)
Yield: 26.4 mg (89%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
1H NMR (400 MHz, CDCl3): δ = 7.18 (s, 1 H), 7.14 (d, J = 8.4 Hz, 1 H),
7.05 (d, J = 9.5 Hz, 2 H), 6.76 (dd, J = 11.1, 8.5 Hz, 2 H), 6.32 (d, J = 15.9
Hz, 1 H), 6.21 (dd, J = 15.9, 6.6 Hz, 1 H), 3.82 (s, 6 H), 3.57–3.50 (m, 1
H), 2.22 (s, 3 H), 2.20 (s, 3 H), 1.42 (d, J = 7.0 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 158.7, 157.7, 137.1, 136.6, 136.2,
134.9, 129.8, 127.3, 126.7, 125.6, 116.1, 115.6, 111.6, 111.4, 55.3 (2 C),
37.9, 21.0, 20.2, 19.8.
(E)-2,2′-(But-1-ene-1,3-diyl)bis(methoxybenzene) (2b)8
Yield: 16.9 mg (63%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
1H NMR (400 MHz, CDCl3): δ = 7.45 (dd, J = 7.6, 1.7 Hz, 1 H), 7.24 (dd,
J = 7.6, 1.7 Hz, 1 H), 7.22–7.16 (m, 2 H), 6.95–6.84 (m, 4 H), 6.80 (dd, J
= 16.1, 1.5 Hz, 1 H), 6.44 (dd, J = 16.1, 6.6 Hz, 1 H), 4.15–4.08 (m, 1 H),
3.86 (s, 3 H), 3.84 (s, 3 H), 1.43 (d, J = 7.2 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 156.9, 156.6, 135.6, 134.7, 128.0,
127.7, 127.1 (2 C), 126.6, 123.0, 120.8, 120.7, 111.8, 110.0, 55.6 (2 C),
35.7, 20.3.
HRMS (EI): m/z calcd for C20H24O2 [M]+: 296.1776; found: 296.1775.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(methylbenzene) (2c)7
Yield: 16.6 mg (70%); colorless oil; Rf = 0.7 (PE/EtOAc, 50:1).
(E)-4,4′-(But-1-ene-1,3-diyl)bis(3-fluoro-1-methoxybenzene) (2h)
Yield: 25.6 mg (84%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
1H NMR (400 MHz, CDCl3): δ = 7.25 (d, J = 2.2 Hz, 1 H), 7.23 (s, 1 H),
7.16 (d, J = 8.1 Hz, 2 H), 7.13–7.08 (m, 4 H), 6.37 (d, J = 16.0 Hz, 1 H),
6.31 (dd, J = 16.0, 6.0 Hz, 1 H), 3.62–3.55 (m, 1 H), 2.32 (s, 3 H), 2.31 (s,
3 H), 1.43 (d, J = 6.8 Hz, 3 H).
1H NMR (400 MHz, CDCl3): δ = 7.33 (t, J = 8.7 Hz, 1 H), 7.15 (t, J = 8.6
Hz, 1 H), 6.68–6.56 (m, 4 H), 6.49 (d, J = 16.0 Hz, 1 H), 6.31 (dd, J =
16.0, 6.7 Hz, 1 H), 3.92–3.85 (m, 1 H), 3.78 (s, 6 H), 1.43 (d, J = 7.0 Hz, 3
H).
13C NMR (101 MHz, CDCl3): δ = 142.9, 136.8, 135.8, 134.9, 134.6,
129.3 (2 C), 128.3, 127.3, 126.2, 42.3, 29.8, 21.5, 21.3, 21.1.
13C NMR (101 MHz, CDCl3): δ = 161.1 (d, J = 246.1 Hz), 160.7 (d, J =
249.4 Hz), 159.9 (d, J = 11.1 Hz), 159.3 (d, J = 11.1 Hz), 134.3 (d, J = 4.0
Hz), 128.8 (d, J = 6.1 Hz), 127.8 (d, J = 6.1 Hz), 124.5 (d, J = 15.2 Hz),
120.9 (d, J = 3.0 Hz), 118.0 (d, J = 13.1 Hz), 110.3 (d, J = 3.0 Hz), 109.9
(d, J = 3.0 Hz), 101.8 (d, J = 26.5 Hz), 101.6 (d, J = 26.3 Hz), 55.7 (2 C),
35.6, 20.5.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(phenoxybenzene) (2d)
Yield: 35.3 mg (90%); colorless oil; Rf = 0.7 (PE/EtOAc, 50:1).
1H NMR (400 MHz, CDCl3): δ = 7.34–7.30 (m, 6 H), 7.23–7.21 (m, 2 H),
7.10–7.06 (m, 2 H), 7.00–6.93 (m, 8 H), 6.39 (d, J = 16.0 Hz, 1 H), 6.29
(dd, J = 16.0 Hz, 6.8 Hz, 1 H), 3.65–3.59 (m, 1 H), 1.46 (d, J = 6.8 Hz, 3
H).
13C NMR (101 MHz, CDCl3): δ = 157.6, 157.5, 156.4, 155.5, 140.7,
134.6, 133.0, 129.9, 129.8, 128.6, 127.8, 127.6, 123.3, 123.1, 119.2 (2
C), 118.8 (2 C), 42.0, 21.5.
HRMS (EI): m/z calcd for C18H18F2O2 [M]+: 304.1275; found: 304.1276.
(E)-2,2′-(But-1-ene-1,3-diyl)bis(1,4-dimethoxybenzene) (2i)8
Yield: 16.1 mg (49%); colorless oil; Rf = 0.7 (PE/EtOAc, 5:1).
1H NMR (400 MHz, CDCl3): δ = 7.00 (d, J = 2.8 Hz, 1 H), 6.82 (d, J =3.2
Hz, 1 H), 6.80 (s, 1 H), 6.77 (s, 1 H), 6.75 (d, J = 1.6 Hz, 1 H), 6.73 (d, J =
2.8 Hz, 1 H), 6.70 (dd, J = 8.8, 3.2 Hz, 1 H), 6.39 (dd, J = 16.1, 6.4 Hz, 1
H), 4.11–4.04 (m, 1 H), 3.81 (s, 3 H), 3.79 (s, 3 H), 3.77 (s, 3 H), 3.76 (s,
3 H), 1.41 (d, J = 6.8 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 153.9 (2 C), 151.3, 151.1, 136.0, 135.6,
128.0, 123.0, 114.5, 113.0, 112.5, 112.0, 111.9, 110.9, 56.5, 56.4, 55.9,
55.8, 35.9, 20.3.
HRMS (EI): m/z calcd for C28H24O2 [M]+: 392.1776; found: 392.1777.
(E)-4,4′-(But-1-ene-1,3-diyl)bis[(benzyloxy)benzene] (2e)
Yield: 36.1 mg (86%); white solid; mp 94–96 °C; Rf = 0.7 (PE/EtOAc,
50:1).
1H NMR (400 MHz, CDCl3): δ = 7.44–7.37 (m, 8 H), 7.31 (dd, J = 18.4,
7.7 Hz, 4 H), 7.19 (d, J = 7.7 Hz, 2 H), 6.93 (dd, J = 11.8, 8.4 Hz, 4 H),
6.34 (d, J = 15.8 Hz, 1 H), 6.23 (dd, J = 15.8, 6.4 Hz, 1 H), 5.06 (s, 4 H),
3.62–3.55 (m, 1 H), 1.43 (d, J = 6.7 Hz, 3 H).
(E)-4,4′-(But-1-ene-1,3-diyl)bis(1-methoxy-2-methylbenzene) (2j)
Yield: 26.1 mg (88%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
1H NMR (400 MHz, CDCl3): δ = 7.19 (s, 1 H), 7.15 (dd, J = 8.4, 2.0 Hz, 1
H), 7.08–7.05 (m, 2 H), 6.77 (dd, J = 11.4, 8.3 Hz, 2 H), 6.33 (d, J = 16.0
Hz, 1 H), 6.22 (dd, J = 16.0, 6.6 Hz, 1 H), 3.82 (s, 6 H), 3.58–3.51 (m, 1
H), 2.23 (s, 3 H), 2.21 (s, 3 H), 1.43 (d, J = 7.2 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 157.1, 156.3, 137.8, 133.5, 130.1,
129.8, 128.4, 127.7, 126.7, 126.6, 125.3, 124.9, 110.0, 55.5, 41.8, 21.6,
16.5, 16.4.
13C NMR (101 MHz, CDCl3): δ = 158.1, 157.4, 138.4, 137.3, 137.2,
133.8, 130.8, 128.7, 128.4, 128.1, 128.0, 127.7, 127.6 (2 C), 127.4,
115.0, 114.9, 70.2 (2 C), 41.8, 21.5.
HRMS (EI): m/z calcd for C30H28O2 [M]+: 420.2089; found: 420.2084.
(E)-[But-1-ene-1,3-diylbis(4,1-phenylene)]bis(methylsulfane) (2f)
Yield: 15.9 mg (53%); white solid; mp 64–66 °C; Rf = 0.7 (PE/EtOAc,
25:1).
HRMS (EI): m/z calcd for C20H24O2 [M]+: 296.1776; found: 296.1772.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(2-fluoro-1-methoxybenzene) (2k)
Yield: 27.1 mg (89%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

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1H NMR (400 MHz, CDCl3): δ = 7.11 (dd, J = 12.6, 2.0 Hz, 1 H), 7.03–
6.94 (m, 3 H), 6.93–6.85 (m, 2 H), 6.28 (d, J = 16 Hz, 1 H), 6.17 (dd, J =
16, 6.8 Hz, 1 H), 3.87 (s, 7 H), 3.59–3.52 (m, 1 H), 1.41 (d, J = 6.8 Hz, 3
H).
13C NMR (101 MHz, CDCl3): δ = 152.6 (d, J = 246.1 Hz), 152.3 (d, J =
246.4 Hz), 146.9 (d, J = 11.1 Hz), 146.0 (d, J = 10.9 Hz), 138.8 (d, J = 5.5
Hz), 134.2, 131.1 (d, J = 6.5 Hz), 127.4 (d, J = 1.9 Hz), 122.8 (d, J = 3.3
Hz), 122.4 (d, J = 1.9 Hz), 115.1 (d, J = 18.3 Hz), 113.6 (d, J = 1.7 Hz),
113.4 (d, J = 1.9 Hz), 113.3 (d, J = 18.7 Hz), 56.5, 56.4, 41.6, 21.2.
HRMS (EI): m/z calcd for C18H16O4 [M]+: 296.1049; found: 296.1053.
(E)-5,5′-(But-1-ene-1,3-diyl)bis(2,3-dihydrobenzofuran) (2p)
Yield: 26.3 mg (90%); colorless oil; Rf = 0.7 (PE/EtOAc, 15:1).
1H NMR (400 MHz, CDCl3): δ = 7.25 (s, 1 H), 7.10–7.08 (m, 2 H), 7.01–
6.99 (m, 1 H), 6.72 (t, J = 8.2 Hz, 2 H), 6.33 (d, J = 16.0 Hz, 1 H), 6.19
(dd, J = 16.0, 6.7 Hz, 1 H), 4.55 (td, J = 8.7, 2.7 Hz, 4 H), 3.58–3.52 (m, 1
H), 3.18 (td, J = 8.7, 4.0 Hz, 4 H), 1.42 (d, J = 7.0 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 159.5, 158.6, 138.3, 133.3, 130.7,
128.0, 127.4, 127.2, 126.8, 126.6, 123.9, 109.3, 109.1, 71.5, 71.3, 42.1,
30.0, 29.8, 21.8.
HRMS (EI): m/z calcd for C18H18F2O2 [M]+: 304.1275; found: 304.1279.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(2-chloro-1-methoxybenzene) (2l)
Yield: 28.6 mg (85%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
HRMS (EI): m/z calcd for C20H20O2 [M]+: 292.1463; found: 292.1460.
1H NMR (400 MHz, CDCl3): δ = 7.39 (d, J = 2.0 Hz, 1 H), 7.25 (d, J = 2.3
Hz, 1 H), 7.17 (dd, J = 8.5, 2.0 Hz, 1 H), 7.10 (dd, J = 8.5, 2.0 Hz, 1 H),
6.86 (dd, J = 12.2, 8.5 Hz, 2 H), 6.26 (d, J = 16.0 Hz, 1 H), 6.18 (dd, J = 16,
6.4 Hz, 1 H), 3.88 (s, 6 H), 3.57–3.51 (m, 1 H), 1.41 (d, J = 7.2 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 154.2, 153.5, 138.8, 134.2, 131.3,
129.2, 127.8, 127.2, 126.5, 125.8, 122.7, 122.4, 112.3, 112.1, 56.3, 41.6,
21.3.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(1,2-dimethoxybenzene) (2q)8
Yield: 28.5 mg (87%); colorless oil; Rf = 0.6 (PE/EtOAc, 5:1).
1H NMR (400 MHz, CDCl3): δ = 6.90 (d, J = 11.3 Hz, 2 H), 6.83–6.79 (m,
4 H), 6.33 (d, J = 16.0 Hz, 1 H), 6.23 (dd, J = 16.0, 6.3 Hz, 1 H), 3.88 (s, 6
H), 3.87 (s, 6 H), 3.61–3.55 (m, 1 H), 1.45 (d, J = 7.2 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 149.1 (2 C), 148.5, 147.6, 138.6, 133.7,
130.8, 128.1, 119.3, 119.2, 111.4, 111.3, 111.0, 108.8, 56.1, 56.0 (2 C),
42.2, 21.4.
HRMS (EI): m/z calcd for
C
18H18Cl2O2 [M]+: 336.0684; found:
336.0679.
(E)-5,5′-(But-1-ene-1,3-diyl)bis(1,2,4-trimethoxybenzene) (2r)8
Yield: 17.2 mg (44%); colorless oil; Rf = 0.5 (PE/EtOAc, 5:1).
1H NMR (400 MHz, CDCl3): δ = 6.96 (s, 1 H), 6.78 (s, 1 H), 6.70 (dd, J =
16.1, 1.6 Hz, 1 H), 6.55 (s, 1 H), 6.49 (s, 1 H), 6.25 (dd, J = 16.1, 6.4 Hz,
1 H), 4.08–4.00 (m, 1 H), 3.88 (s, 6 H), 3.84 (s, 3 H), 3.83 (s, 3 H), 3.82
(s, 3 H), 3.81 (s, 3 H), 1.40 (d, J = 7.2 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 151.1 (2 C), 149.0, 147.9, 143.5, 143.3,
133.5, 126.4, 122.2, 119.0, 112.2, 109.8, 98.4, 98.1, 56.9 (3 C), 56.6,
56.3, 56.2, 35.1, 20.5.
(E)-4,4′-(But-1-ene-1,3-diyl)bis(2-bromo-1-methoxybenzene)
(2m)
Yield: 35.8 mg (84%); colorless oil; Rf = 0.7 (PE/EtOAc, 25:1).
1H NMR (400 MHz, CDCl3): δ = 7.57 (d, J = 1.8 Hz, 1 H), 7.42 (d, J = 1.9
Hz, 1 H), 7.22 (dd, J = 8.5, 1.8 Hz, 1 H), 7.15 (dd, J = 8.4, 1.9 Hz, 1 H),
6.83 (dd, J = 12.6, 8.5 Hz, 2 H), 6.26 (d, J = 16.0 Hz, 1 H), 6.18 (dd, J =
16.0, 6.3 Hz, 1 H), 3.88 (s, 6 H), 3.58–3.51 (m, 1 H), 1.41 (d, J = 6.8 Hz, 3
H).
13C NMR (101 MHz, CDCl3): δ = 155.1, 154.4, 139.3, 134.3, 132.2,
131.8, 130.8, 127.3, 127.0, 126.5, 112.1, 112.0, 111.9, 111.7, 56.4, 41.5,
21.3.
(E)-2,2′-(But-1-ene-1,3-diyl)dithiophene (2s)
Yield: 12.1 mg (55%); colorless oil; Rf = 0.7 (PE).
1H NMR (400 MHz, CDCl3): δ = 7.18 (dd, J = 5.1, 1.2 Hz, 1 H), 7.12 (d, J =
5.0 Hz, 1 H), 6.97–6.92 (m, 3 H), 6.87 (dt, J = 3.5, 1.0 Hz, 1 H), 6.58 (d, J
= 15.7 Hz, 1 H), 6.20 (dd, J = 15.6, 7.4 Hz, 1 H), 3.90–3.83 (m, 1 H), 1.53
(d, J = 7.0 Hz, 3 H).
13C NMR (101 MHz, CDCl3): δ = 149.5, 142.5, 134.3, 127.4, 126.9,
125.3, 123.9, 123.6, 123.4, 122.5, 38.2, 22.3.
HRMS (EI): m/z calcd for C12H12S2 [M]+: 220.0380; found: 220.0384.
HRMS (EI): m/z calcd for
C
18H18Br2O2 [M]+: 423.9674; found:
423.9673.
(E)-6,6′-(But-1-ene-1,3-diyl)bis(2,3-dihydrobenzo[b][1,4]dioxine)
(2n)
Yield: 26.9 mg (83%); colorless oil; Rf = 0.6 (PE/EtOAc, 5:1).
1H NMR (400 MHz, CDCl3): δ = 6.88 (d, J = 1.9 Hz, 1 H), 6.84 (dd, J = 8.3,
2.0 Hz, 1 H), 6.82–6.77 (m, 3 H), 6.73 (dd, J = 8.2, 2.0 Hz, 1 H), 6.27 (d,
J = 16.0 Hz, 1 H), 6.17 (dd, J = 16.0, 6.7 Hz, 1 H), 4.24 (s, 9 H), 3.54–3.47
(m, 1 H), 1.39 (d, J = 7.0 Hz, 3 H).
(E)-1,1′-(But-1-ene-1,3-diyl)bis(pyrrolidin-2-one) (2t)9
13C NMR (101 MHz, CDCl3): δ = 143.6, 143.4, 142.9, 141.9, 139.4,
133.9, 131.6, 127.7, 120.3, 119.6, 117.3, 117.2, 116.0, 114.8, 64.5 (2 C),
64.5, 41.9, 21.5.
Yield: 19.8 mg (89%); light yellow oil; Rf = 0.5 (PE/acetone, 1:1).
1H NMR (400 MHz, CDCl3): δ = 6.96 (d, J = 13.8 Hz, 1 H), 4.93–4.82 (m,
2 H), 3.47–3.44 (m, 2 H), 3.31–3.21 (m, 2 H), 2.46 (t, J = 7.6 Hz, 2 H),
2.36 (t, J = 8.0 Hz, 2 H), 2.12–2.04 (m, 2 H), 2.00–1.93 (m, 2 H), 1.26 (d,
J = 6.8 Hz, 3 H).
HRMS (EI): m/z calcd for C20H20O4 [M]+: 324.1362; found: 324.1364.
13C NMR (101 MHz, CDCl3): δ = 174.4, 173.4, 125.2, 110.8, 46.1, 45.3,
42.5, 31.6, 31.3, 18.0, 17.5, 17.1.
(E)-5,5′-(But-1-ene-1,3-diyl)bis(benzo[d][1,3]dioxole) (2o)
Yield: 24.6 mg (83%); colorless oil; Rf = 0.6 (PE/EtOAc, 5:1).
1H NMR (400 MHz, CDCl3): δ = 6.90 (d, J = 1.6 Hz, 1 H), 6.79–6.70 (m, 5
H), 6.30 (d, J = 16.0 Hz, 1 H), 6.16 (dd, J = 16.0, 6.7 Hz, 1 H), 5.93 (s, 2
H), 5.92 (s, 2 H), 3.57–3.50 (m, 1 H), 1.40 (d, J = 7.0 Hz, 3 H).
Funding Information
13C NMR (101 MHz, CDCl3): δ = 148.1, 147.8, 146.9, 146.0, 139.9,
133.8, 132.2, 128.2, 120.7, 120.2, 108.4, 108.3, 107.9, 105.7, 101.1,
101.0, 42.3, 21.6.
We gratefully acknowledge the National Science Foundation of China
(21602213, 21522208, and 21372209) for financial support.
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F

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Supporting Information
(c) Masuda, T.; Isobe, E.; Higashimura, T. J. Am. Chem. Soc. 1983,
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Komiya, S.; Hirano, M. Organometallics 2014, 33, 6604. (c) Erver,
F.; Kuttner, J. R.; Hilt, G. J. Org. Chem. 2012, 77, 8375.
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Supporting information for this article is available online at
https://doi.org /10.1055/s-0036-1589039.
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© Georg Thieme Verlag Stuttgart · New York — Synthesis 2017, 49, A–F