Stereoselective synthesis of (E)-β-arylvinyl bromides by microwave-induced Hunsdiecker-type reaction

Article abstract of DOI:10.1055/s-2005-865283

(E)-β-Arylvinyl bromides were readily prepared in a short reaction time (1-2 min) by microwave irradiation of the corresponding 3-arylpropenoic acids in the presence of N-bromosuccinimide and a catalytic amount of lithium acetate. Furthermore, two facile strategies for the efficient synthesis of (E)-β-bromo-4-arylethynylstyrene and (E)-β-bromo-4-arylstyrene have been developed by respectively combining Sonogashira and Suzuki coupling reaction with Hunsdiecker-type reaction. Formation of cis-α-bromo-β- lactone by microwave irradiation of cis-cinnamic acid with NBS provides a useful support for the mechanistic study of the present halodecarboxylation reaction. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2005-865283

PAPER
1319
Stereoselective Synthesis of (E)-b-Arylvinyl Bromides by Microwave-Induced
Hunsdiecker-Type Reaction
M
icrowave-Induc
h
edHunsdiec
u
ker-Type Re
n
a
ction xiang Kuang,*a Qing Yang,b Hisanori Senboku,c Masao Tokudac
a
Department of Materials Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan
Fax +81(6)68505785; E-mail: kuang@ch.wani.osaka-u.ac.jp
b
c
Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo, 060-8589, Japan
Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Received 2 December 2004; revised 19 January 2005
Recently, the method of microwave irradiation has been
used by organic chemists to effect organic transforma-
tions. Remarkable reductions in reaction times, clean con-
ditions and better yields have been reported in
Abstract: (E)-b-Arylvinyl bromides were readily prepared in a
short reaction time (1–2 min) by microwave irradiation of the cor-
responding 3-arylpropenoic acids in the presence of N-bromosuc-
cinimide and a catalytic amount of lithium acetate. Furthermore,
two facile strategies for the efficient synthesis of (E)-b-bromo-4- microwave-induced reactions.19 In a preliminary paper,20
arylethynylstyrene and (E)-b-bromo-4-arylstyrene have been devel-
oped by respectively combining Sonogashira and Suzuki coupling
reaction with Hunsdiecker-type reaction. Formation of cis-a-bro-
mo-b-lactone by microwave irradiation of cis-cinnamic acid with
NBS provides a useful support for the mechanistic study of the
present halodecarboxylation reaction.
we reported a microwave-induced Hunsdiecker-type reac-
tion for the stereoselective synthesis of (E)-b-arylvinyl ha-
lides from 3-arylpropenoic acids. In this paper, we report
the application of microwave-induced Hunsdiecker-type
reaction to the synthesis of the various (E)-b-arylvinyl
bromides carrying either an electron-donating or -with-
drawing group. Using our optimized conditions, micro-
wave irradiation of 3-arylpropenoic acids 1 in an
acetonitrile–water (4.6:0.4) solvent containing N-bromo-
succinimide (1.05 equiv) and catalytic amount of LiOAc
(0.2 equiv) for 1–2 min gave the corresponding (E)-b-
arylvinyl bromides 2 in good to excellent yields
(Scheme 1). The results summarized in Table 1 show that
the vinyl bromides 2a–h were obtained in higher yields
and in a shorter reaction time by the microwave irradia-
tion method than by previous methods.17h,m By previous
methods, (E)-b-arylvinyl bromides carrying strong elec-
tron-donating groups such as methoxy (2f) generally
could be prepared in high yields, however, the reaction of
trans-cinnamic acids carrying an electron-withdrawing
group (1i–l) or unsubstituted trans-cinnamic acids (1a, 1g
and 1h) with NBS gave (E)-b-arylvinyl bromides in low
yields. Under previous conditions, some (E)-b-arylvinyl
bromides even bearing an electron-donating group were
still produced in moderate yields, because the electron-do-
nating group such as methyl (2b and 2c) was not strong
enough. Moreover, the existence of big functional group
such as benzyloxyl (2d and 2e) in the molecules also re-
sulted in unsatisfactory yields. However, these problems
are circumvented by our present method. Microwave irra-
diation of 1i–l gave the products 2i–l in moderate yields;
even so, these yields were higher than those obtained by
previously reported methods. These results indicated that
the present microwave-induced Hunsdiecker-type reac-
Key words: (E)-b-arylvinyl bromides, a,b-unsaturated carboxylic
acids, stereoselective synthesis, microwave irradiation, Huns-
diecker-type reaction
(E)-Vinyl bromides are very useful synthetic intermedi-
ates in organic synthesis. Their use as precursors of vinyl
anion1 and as coupling components in a wide range of
transition metal-catalyzed coupling reaction2 has stimu-
lated a great deal of interests in their synthesis. Therefore,
development of methods for their stereoselective synthe-
sis is of considerable importance. There are many meth-
ods for the preparation of (E)-vinyl bromides, but the
reagents used in most cases are limited to organometallic
compounds such as organoaluminum,3 organoboron,4 or-
ganosilicon,5 geminal dichromium reagent,6 organozinc
reagent,7 organolithium reagent,8 hydrozirconating re-
agent,9 organotin reagent,10 indium metal,11 Grignard re-
agent,12 and samarium metal.13 Methods using diethyl
phosphonate,14 lithium aluminum hydride15 and electro-
chemical reduction16 have also been reported. The
Hunsdiecker-type bromodecarboxylation17 and decarbox-
ylation of cinnamic acid dibromides18 have been the most
frequently used methods for the synthesis of (E)-vinyl
bromides. However, these synthetic methods have several
drawbacks: use of complex reagent such as organometal-
lic compounds, bis(collidine)halogen(I) hexafluorophos-
phate, and tetrabutylammonium trifluoroacetate, use of a
large amount of solvent for dissolution of substrate and
catalyst, long reaction time, low yields and limitation to
arylvinyl bromides carrying electron-withdrawing group.
NBS, LiOAc
Br
MeCN–H2O
CO2H
Ar
Ar
MW 1–2 min
SYNTHESIS 2005, No. 8, pp 1319–1325
Advanced online publication: 23.03.2005
x
x
.
x
x
.2
0
0
5
1
2
DOI: 10.1055/s-2005-865283; Art ID: F17704SS
Scheme 1
© Georg Thieme Verlag Stuttgart · New York

1320
C. Kuang et al.
PAPER
Table 1 Stereoselective Synthesis of (E)-b-Arylvinyl Bromides 2
Entry
1
Acid 1
Product 2
MW (min)
1
Yield (%)a
84
E/Zb
Br
1a
2a
2b
>95:5
2
3
1b
1c
1
1
91
92
>98:2
Br
Me
2c
>98:2
Br
Me
Me
4
5
1d
1e
2d
2e
1
1
93
90
>98:2
>98:2
Br
BnO
BnO
Br
Br
OMe
6
1f
2f
1
98
>98:2
MeO
OMe
OMe
7
8
1g
1h
2g
2h
1
1
88
84
>98:2
>98:2
Br
Br
9
10
11
12
1i
2i
2
2
2
2
60
56
71
52
97:3
Br
F
1j
1k
1l
2j
2k
2l
97:3
Br
Cl
Br
>97:3
>96:4
Br
Br
CF3
a Isolated yields.
b Determined by 1H NMR spectroscopy.
tion was very useful for the synthesis of (E)-b-arylvinyl Alkynyl arenes and biarenes are very useful precursors for
bromides carrying either an electron-donating or -with- conducting polymers, liquid crystals, and nonlinear opti-
drawing group.
cal materials. For the carbon–carbon bond formation, the
Sonogashira coupling and Suzuki coupling have been fre-
quently used. (E)-b-Bromo-4-phenylethynylstyrene (2n)
was prepared in two steps by coupling 4-bromocinnamic
acid with ethynylbenzene followed by bromodecarboxy-
lation of the coupling product 1n (Scheme 3). A similar
Similarly, the microwave irradiation of 4-benzenediacryl-
ic acid (1m) with NBS afforded the corresponding 1,4-
bis(trans-b-bromovinyl)benzene (2m) in 68% yield
(Scheme 2). Compound 2m can be used for the synthesis
of conjugated polymers.21
Synthesis 2005, No. 8, 1319–1325 © Thieme Stuttgart · New York

PAPER
Microwave-Induced Hunsdiecker-Type Reaction
1321
CO2H
Br
NBS, LiOAc
MeCN–H2O
HO2C
Br
MW 2 min
1m
2m
68% (E,E)/(E,Z)/(Z,Z)>97:2:1
Scheme 2
attempt involving Suzuki coupling/bromodecarboxyla-
tion led to the formation of (E)-b-bromo-4-anisylstyrene
(2o) (Scheme 4). These two processes using microwave
reaction as key step could provide an easy access to vari-
ous substituted arylvinyl bromides.
O
O
O
NBS
LiOAc
O
Ar
OLi
Ar
OH
Br
Ar
Br
1
A
Proposed reaction pathways of the present halodecarbox-
ylation are shown in Scheme 5. Reaction of lithium car-
boxylate of 1 with NBS gives bromonium ion A, which is
immediately converted to trans-a-bromo-b-lactone B or
zwitterion C, which would eliminate carbon dioxide to
give (E)-b-arylvinyl bromide 2. The thermal decomposi-
tion of b-lactone is a well-established method for the ste-
reoselective synthesis of substituted alkenes. These
thermal reactions are reported to proceed through a transi-
tion state with a zwitterionic character.22 The formation of
trans-3-bromo-4-phenylbutenolide17h,23 from the reaction
of 4-phenylbut-3-enoic acid with NBS and catalytic LiO-
Ac provides an indirect experimental support for the oc-
currence of intermediates A and B. However, even at low
temperature, no signals for intermediate A and B were de-
tected in the 1H NMR of the reaction mixture.
O
O
O
H
-CO2
O
Ar
Ar
Br
H
Ar
Br
2
C
B
Scheme 5
Recently, we were induced to study the reactivity of cis-
cinnamic acid with NBS. Much to our delight, a mixture
of cis-3-bromo-4-phenyloxetan-2-one (4) and b-bro-
mostyrene (E/Z = 74:26) were found by microwave irra-
diation of cis-cinnamic acid (3) with NBS (Scheme 6).24
1
The coupling constant (J = 5.94 Hz) observed in the H
NMR of 4 clearly indicated that 4 was a cis-b-lactone. In
the IR spectrum, the characteristic carbonyl absorption
was observed at 1844 cm–1. EI-MS spectrum showed the
specific peak due to decarboxylation of the lactone (M+ –
CO2H
CO2H
Pd(PPh3)4, CuI
+
Et3N, DMF
Br
120 °C, 5 h
1n
80%
Br
NBS, LiOAc
MeCN–H2O
MW 2 min
2n
85% E/Z >98:2
Scheme 3
CO2H
CO2H
Pd(PPh3)4
+
B(OH)2
MeO
Et3N, DMF
Br
100 °C, 7 h
1o
MeO
Br
88%
NBS, LiOAc
MeCN–H2O
MW 2 min
MeO
2o
91% E/Z >98:2
Scheme 4
Synthesis 2005, No. 8, 1319–1325 © Thieme Stuttgart · New York

1322
C. Kuang et al.
PAPER
which was recrystallized from AcOH to give 1n; yield: 992 mg
(80%); colorless crystals; mp 211.0–212.0 °C (AcOH).
CO2). The lability of cis-a-bromo-b-lactone makes it dif-
ficult to purify this compound by chromatography. The
phenomenon that cis-a-bromo-b-lactone easily decarbox- IR (Nujol): 1701, 1677, 1627, 721 cm–1.
1H NMR (CDCl3 + DMSO-d6): d = 6.44 (1 H, d, J = 16.0 Hz),
7.34–7.37 (3 H, m), 7.52–7.55 (6 H, m), 7.65 (1 H, d, J = 16.0 Hz).
ylated to the b-bromostyrene even at room temperature
1
was observed by H NMR detection. Nishida et al. have
shown that the decarboxylation rate of the trans-b-lactone
is higher than that of cis-b-lactone.25 Combining these
facts together, it is not surprising to note that no signals for
trans-a-bromo-b-lactone B were found in the 1H NMR of
the reaction mixture of trans-cinnamic acid with NBS,
even if intermediate B could be present.
13C NMR (CDCl3 + DMSO-d6): d = 89.02, 91.09, 122.06, 123.84,
128.32, 128.64, 128.86, 131.34, 131.71, 134.37, 142.85.
EIMS: m/z (%) = 248 (M+, 100), 202 (45).
HRMS: m/z calcd for C17H12O2 [M+]: 248.0839; found: 248.0838.
Anal. Calcd for C17H12O2: C, 82.24; H, 4.87. Found: C, 82.29; H,
4.83.
O
O
trans-4-Anisylcinnamic Acid (1o)
NBS, LiOAc
MeCN–H2O
To a degassed solution of 4-bromocinnamic acid (5.0 mmol, 1.140
g), 4-anisylboronic acid (6.0 mmol, 912 mg), Pd(Ph3P)4 (0.30
mmol, 347 mg) in anhyd DMF (25 mL) was added Et3N (20 mmol,
2.023 g) under argon. The mixture was stirred at 100 °C in an oil
bath for 7 h. After cooling to r.t., the resulting mixture was
quenched with aq HCl and filtered. The precipitate was washed with
Et2O and purified by column chromatography on silica gel with
EtOAc–hexane to give a crude product, which was recrystallized
from acetone–H2O to yield 1o; yield: 1.117 g (88%); colorless crys-
tals; mp 230–231 °C (acetone–H2O).
Br
+
CO2H
Br
MW 1 min
3
E/Z = 74:26
β-bromostyrene
40%
4
cis-α-bromo-β-lactone
30%
Scheme 6
In conclusion, this application of microwave irradiation to
the Hunsdiecker-type reaction is found to have significant
advantage over existing procedure. We have developed a
simple and efficient method for the preparation of b-
arylvinyl bromides from the corresponding 3-aryl-prope-
noic acids using NBS in a high yield and with a high ste-
reoselectivity. For the first time we have isolated and
detected a new a-bromo-b-lactone by microwave irradia-
tion of cis-cinnamic acid with NBS, which provide a use-
ful support for the mechanism study of the present
bromodecarboxylation reaction.
IR (Nujol): 1678, 1602, 823 cm–1.
1H NMR (CDCl3 + DMSO-d6): d = 3.85 (3 H, s), 6.44 (1 H, d,
J = 15.8 Hz), 6.98 (2 H, d, J = 8.5 Hz), 7.54–7.58 (6 H, m), 7.68 (1
H, d, J = 15.8 Hz).
13C NMR (CDCl3 + DMSO-d6): d = 54.80, 113.81, 117.88, 126.34,
127.47, 128.01, 131.91, 132.32, 141.79, 143.54, 159.01, 168.17.
EIMS: m/z (%) = 254 (M+, 100), 239 (35), 211 (18).
HRMS: m/z calcd for C16H14O3 [M+]: 254.0943; found: 254.0932.
Anal. Calcd for C16H14O3: C, 75.58; H, 5.55. Found: C, 75.63; H,
5.48.
(E)-b-Arylvinyl Bromides 2; General Procedure
Melting points were recorded using a Yanagimoto micro melting
point apparatus and were uncorrected. IR spectra were recorded us-
ing a JASCO IR-810 IR spectrometer (between NaCl plates). H
A mixture of substituted trans-cinnamic acid 1 (5 mmol), LiOAc (1
mmol), and NBS (935 mg, 5.25 mmol) was added to a mixture of
MeCN–H2O (5 mL, 4.6:0.4). The mixture was kept inside a micro-
wave oven operating at 2450 MHz (Toshiba, ER-V11, 200 watt)
and was irradiated for 1–2 min. The reaction mixture was removed
from the oven, and cooled to r.t. Evaporation of the solvent under
reduced pressure gave the crude product, which was subjected to
column chromatography (silica gel, EtOAc–hexane) to afford (E)-
b-arylvinyl bromides 2. In the case of acids 1d, 1e, 1g, 1h, 1m, 1n
and 1o, the reaction scale was 1.0 mmol.
1
and 13C NMR spectra were recorded using a JEOL JNM-EX270 FT
NMR spectrometer at 270 MHz (1H) and at 67.8 MHz (13C) in
CDCl3 with SiMe4 as an internal standard. High- and low-resolution
mass spectra were determined using a JEOL JMS-FABmate or
JEOL JMS-700TZ spectrometer. Column chromatography was car-
ried out on a silica gel 60 N (100–210 mm, Kanto Chemical Co.
Ltd). Commercially available NBS, 4-bromocinnamic acid, and
LiOAc were used without any further purification. Commercially
available MeCN was purified by distillation. Commercially avail-
able anhyd DMF packed under N2 (Kanto Chemical) was used
without any further purification. Et3N, CuI, Pd(Ph3P)4, phenylacet-
ylene, and 4-anisylboronic acid are available from Aldrich. Substi-
tuted trans-cinnamic acids 1a–m are commercially available. Acids
1n and 1o were prepared as described below. cis-Cinnamic acid (3)
was prepared according to the procedure reported in the literature.26
(E)-b-Bromostyrene (2a)27
Yield: 764 mg (84%); colorless oil.
IR (neat): 1609, 1575, 941 cm–1.
1H NMR (270 MHz, CDCl3): d = 6.77 (1 H, d, J = 13.9 Hz), 7.11 (1
H, d, J = 13.9 Hz), 7.27–7.32 (5 H, m).
13C NMR (67.5 MHz, CDCl3): d = 106.49, 126.06, 128.23, 128.75,
135.85, 137.11.
(E)-3-[(4-(2-Phenylethynyl)phenyl]prop-2-enoic Acid (1n)
To a mixture of 4-bromocinnamic acid (5.0 mmol, 1.140 g), phenyl-
acetylene (6.0 mmol, 613 mg), CuI (0.30 mmol, 57 mg) and
Pd(Ph3P)4 (0.30 mmol, 347 mg) in anhyd degassed DMF (20 mL)
was added Et3N (20.0 mmol, 2023 mg) under argon. The mixture
was stirred at 120 °C in an oil bath for 5 h. After cooling to r.t., the
resulting mixture was quenched with aq HCl and filtered. The pre-
cipitate was washed with Et2O and purified by column chromatog-
raphy on silica gel with EtOAc–hexane to afford the crude product,
EIMS: m/z (%) = 184 [(M + 2)+, 81], 182 (M+, 82), 103 (100), 77
(39).
HRMS: m/z calcd for C8H779Br [M+]: 181.9731; found: 181.9729.
(E)-b-Bromo-4-methylstyrene (2b)27
Yield: 892 mg (91%); colorless crystals; mp 46.0–46.5 °C (EtOH)
(Lit.27 mp 46.0–46.5 °C).
Synthesis 2005, No. 8, 1319–1325 © Thieme Stuttgart · New York

PAPER
Microwave-Induced Hunsdiecker-Type Reaction
1323
IR (Nujol): 1605, 1511, 931 cm–1.
13C NMR (67.5 MHz, CDCl3): d = 55.97, 60.84, 60.95, 106.02,
107.51, 121.70, 122.84, 132.18, 142.37, 151.19, 153.74.
1H NMR (270 MHz, CDCl3): d = 2.32 (3 H, s), 6.70 (1 H, d,
J = 13.9 Hz), 7.06 (1 H, d, J = 13.9 Hz), 7.12 (2 H, d, J = 8.3 Hz),
7.19 (2 H, d, J = 8.3 Hz).
EIMS: m/z (%) = 274 [(M + 2)+, 48], 272 (M+, 50), 193 (42), 178
(100).
13C NMR (67.5 MHz, CDCl3): d = 21.24, 105.39, 125.97, 129.45,
133.14, 137.00, 138.20.
HRMS: m/z calcd for C11H1379BrO3 [M+]: 272.0048; found:
272.0047.
EIMS: m/z (%) = 198 [(M + 2)+, 43], 196 (M+, 45), 117 (100), 115
(80), 91 (44).
Anal. Calcd for C11H13BrO3: C, 48.37; H, 4.80; Br, 29.26. Found:
C, 48.18; H, 4.71; Br, 29.10.
HRMS: m/z calcd for C9H979Br [M+]: 195.9887; found: 195.9874.
(E)-2-(b-Bromovinyl)naphthalene (2g)12
Yield: 204 mg (88%); colorless crystals; mp 84–85 °C (EtOH).
IR (Nujol): 1611, 1594, 945 cm–1.
(E)-b-Bromo-4-isopropylstyrene (2c)15
Yield: 1.031 g (92%); colorless oil.
IR (neat): 1610, 1578, 1513, 1223, 933 cm–1.
1H NMR (270 MHz, CDCl3): d = 6.90 (1 H, d, J = 13.9 Hz), 7.26 (1
H, d, J = 13.9 Hz), 7.44–7.49 (3 H, m), 7.69 (1 H, d, J = 1.0 Hz),
7.77–7.83 (3 H, m).
13C NMR (67.5 MHz, CDCl3): d = 106.84, 122.90, 126.28, 126.35,
126.60, 127.74, 128.08, 128.55, 133.12, 133.33, 133.44, 137.25.
1H NMR (270 MHz, CDCl3): d = 1.23 (6 H, d, J = 6.9 Hz), 2.87 (1
H, q, J = 6.9 Hz), 6.69 (1 H, d, J = 13.9 Hz), 7.06 (1 H, d, J = 13.9
Hz), 7.16 (2 H, d, J = 8.6 Hz), 7.21 (2 H, d, J = 8.6 Hz).
13C NMR (67.5 MHz, CDCl3): d = 23.79, 33.87, 105.46, 126.07,
126.81, 133.51, 136.98, 149.14.
EIMS: m/z (%) = 234 [(M + 2)+, 85], 232 (M+, 86), 153 (95), 152
(100), 127 (20), 76 (27).
HRMS: m/z calcd for C12H979Br [M+]: 231.9887; found: 231.9907.
EIMS: m/z (%) = 226 [(M + 2)+, 54], 224 (M+, 57), 209 (100), 130
(46).
HRMS: m/z calcd for C11H1379Br [M+]: 224.0200; found: 224.0201.
(E)-1-(b-Bromovinyl)naphthalene (2h)11
Yield: 195 mg (84%); colorless oil.
(E)-b-Bromo-4-benzyloxystyrene (2d)
Yield: 268 mg (93%); colorless crystals; mp 77–78 °C.
IR (neat): 1603, 1590, 935 cm–1.
IR (film): 1509, 1458, 955, 695 cm–1.
1H NMR (270 MHz, CDCl3): d = 6.76 (1 H, d, J = 13.9 Hz), 7.38–
7.56 (4 H, m), 7.79–7.86 (3 H, m), 8.02 (1 H, d, J = 13.9 Hz).
13C NMR (67.5 MHz, CDCl3): d = 108.46, 123.67, 124.19, 125.50,
126.07, 126.22, 126.42, 128.50, 128.73, 130.49, 133.50, 134.95.
1H NMR (270 MHz, CDCl3): d = 5.06 (2 H, s), 6.61 (1 H, d,
J = 13.9 Hz), 6.92 (2 H, d, J = 8.9 Hz), 7.03 (1 H, d, J = 13.9 Hz),
7.23 (2 H, d, J = 8.9 Hz), 7.34–7.41 (5 H, m).
13C NMR (67.5 MHz, CDCl3): d = 69.97, 104.11, 115.07, 127.33,
127.42, 128.03, 128.59, 128.95, 136.47, 136.64, 158.79.
EIMS: m/z (%) = 234 [(M + 2)+, 13], 232 (M+, 13), 153 (93), 152
(100), 126 (17), 76 (12).
EIMS: m/z (%) = 290 [(M + 2)+, 5], 288 (M+, 5), 91 (100).
HRMS: m/z calcd for C12H979Br [M+]: 231.9887; found: 231.9907.
HRMS: m/z calcd for C15H1379BrO [M+]: 288.0150; found:
288.0149.
(E)-b-Bromo-4-fluorostyrene (2i)28
Yield: 600 mg (60%); colorless oil.
Anal. Calcd for C15H13BrO: C, 62.30; H, 4.53; Br, 27.63. Found: C,
62.11; H, 4.63; Br, 27.45.
IR (neat): 1602, 1589, 946 cm–1.
1H NMR (270 MHz, CDCl3): d = 6.67 (1 H, d, J = 13.9 Hz), 6.95–
7.03 (2 H, m), 7.04 (1 H, d, J = 13.9 Hz), 7.21–7.25 (2 H, m).
13C NMR (67.5 MHz, CDCl3): d = 106.07 (d, J = 2.5 Hz), 115.76
(d, J = 20.7 Hz), 127.68 (d, J = 8.5 Hz), 132.10 (d, J = 3.7 Hz),
135.93, 162.56 (d, J = 247.8 Hz).
(E)-b-Bromo-4-benzyloxy-3-methoxystyrene (2e)
Yield: 286 mg (90%); colorless crystals; mp 104–105 °C (hexane).
IR (Nujol): 1612, 1508, 1277, 1155, 720 cm–1.
1H NMR (270 MHz, CDCl3): d = 3.88 (3 H, s), 5.14 (2 H, s), 6.52
(1 H, d, J = 13.9 Hz), 6.84 (3 H, m), 6.97 (1 H, d, J = 13.9 Hz),
7.30–7.46 (5 H, m).
EIMS: m/z (%) = 202 [(M + 2)+, 28], 200 (M+, 27), 202 (28), 149
(100).
13C NMR (67.5 MHz, CDCl3): d = 56.01, 71.12, 104.22, 111.46,
111.69, 119.89, 127.29, 127.97, 128.60, 128.89, 136.69, 136.83,
148.26, 150.00.
EIMS: m/z (%) = 320 [(M + 2)+, 48], 318 (M+, 50), 91 (100).
HRMS: m/z calcd for C16H1579BrO2 [M+]: 318.0256; found:
HRMS: m/z calcd for C8H679BrF [M+]: 199.9637; found: 199.9629.
(E)-b-Bromo-4-chlorostyrene (2j)29
Yield: 605 mg (56%); colorless crystals; mp 47–48 °C (MeOH)
(Lit.29 mp 47–48 °C).
IR (Nujol): 1604, 1586, 945 cm–1.
318.0244.
1H NMR (270 MHz, CDCl3): d = 6.75 (1 H, d, J = 13.9 Hz), 7.05 (1
H, d, J = 13.9 Hz), 7.21 (2 H, d, J = 8.6 Hz), 7.29 (2 H, d, J = 8.6
Hz).
Anal. Calcd for C16H15BrO2: C, 60.21; H, 4.74; Br, 25.03. Found:
C, 60.05; H, 4.61; Br, 25.01.
(E)-b-Bromo-2,3,4-trimethoxystyrene (2f)
Yield: 1.333 g (98%); colorless crystals; mp 66–67 °C (hexane).
13C NMR (67.5 MHz, CDCl3): d = 107.19, 127.26, 129.00, 134.03,
134.36, 135.98.
IR (film): 1595, 1494, 944, 669 cm–1.
EIMS: m/z (%) = 220 [(M + 4)+, 23], 218 [(M + 2) +, 100], 216 (M+,
77), 139 (32), 137 (98), 102 (57), 101 (63), 75 (36).
HRMS: m/z calcd for C8H679Br35Cl [M+]: 215.9341; found:
215.9343.
1H NMR (270 MHz, CDCl3): d = 3.86 (3 H, s), 3.87 (3 H, s), 3.88
(3 H, s), 6.63 (1 H, d, J = 8.6 Hz), 6.77 (1 H, d, J = 13.9 Hz), 6.98
(1 H, d, J = 8.6 Hz), 7.20 (1 H, d, J = 13.9 Hz).
Synthesis 2005, No. 8, 1319–1325 © Thieme Stuttgart · New York

1324
C. Kuang et al.
PAPER
(E)-b-Bromo-4-bromostyrene (2k)30
Yield: 930 mg (71%); colorless crystals; mp 67–68 °C (Lit.30 mp
67–68 °C).
13C NMR (67.5 MHz, CDCl3): d = 55.34, 106.14, 114.17, 114.26,
126.48, 126.72, 126.93, 127.94, 128.14, 128.69, 132.86, 134.25,
136.78, 140.62, 159.33.
IR (Nujol): 1610, 1589, 930 cm–1.
EIMS: m/z (%) = 290 [(M + 2)+, 8], 288 (M+, 8), 184 (100).
1H NMR (270 MHz, CDCl3): d = 6.78 (1 H, d, J = 14.2 Hz), 7.04 (1
H, d, J = 14.2 Hz), 7.15 (2 H, d, J = 8.3 Hz), 7.44 (2 H, d, J = 8.3
Hz).
13C NMR (67.5 MHz, CDCl3): d = 107.33, 122.17, 127.55, 131.93,
134.77, 136.03.
HRMS: m/z calcd for C15H1379BrO [M+]: 288.0149; found:
288.0148.
Anal. Calcd for C15H13BrO: C, 62.30; H, 4.53; Br, 27.63. Found: C,
62.24; H, 4.55; Br, 27.61.
EIMS: m/z (%) = 264 [(M + 2)+, 90], 262 (M+, 100), 181 (78), 102
(70).
Acknowledgment
This work was supported by a Grant-in-Aid for Exploratory Re-
search (No. 13875171) from Japan Society for the Promotion of
Science. We would like to thank S. Oka, M. Kiuchi, Y. Takihata and
N. Hazama (Center for Instrumental Analysis, Hokkaido Universi-
ty) for their assistance in measurement of mass spectra.
HRMS: m/z calcd for C8H679Br81Br [M+]: 261.8816; found:
261.8825.
(E)-b-Bromo-3-trifluoromethylstyrene (2l)31
Yield: 650 mg (60%); colorless oil.
IR (neat): 1613, 1591, 939 cm–1.
1H NMR (270 MHz, CDCl3): d = 6.86 (1 H, d, J = 14.0 Hz), 7.12 (1
H, d, J = 14.0 Hz), 7.40–7.90 (4 H, m).
13C NMR (67.5 MHz, CDCl3): d = 108.68, 122.74 (d, J = 3.7 Hz),
124.77 (d, J = 3.7 Hz), 126.79 (q, J = 272.2 Hz), 129.22 (d, J = 8.5
Hz), 131.25 (d, J = 33.0 Hz), 135.81, 136.58.
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(E,E)-1,4-Bis(b-bromovinyl)benzene (2m)32
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52), 207 (36), 128 (72).
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(E)-b-Bromo-4-anisylstyrene (2o)
Yield: 254 mg (91%); colorless crystals; mp 94–95 °C (hexane).
IR (Nujol): 1610, 1497, 762 cm–1.
1H NMR (270 MHz, CDCl3): d = 3.85 (3 H, s), 6.79 (1 H, d,
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Synthesis 2005, No. 8, 1319–1325 © Thieme Stuttgart · New York

PAPER
Microwave-Induced Hunsdiecker-Type Reaction
1325
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d = 2.96 (1 H, dd, J = 18.1, 6.6 Hz), 3.23 (1 H, dd,
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Synthesis 2005, No. 8, 1319–1325 © Thieme Stuttgart · New York