Synthesis of (Z)-1-bromo-1-alkenes and terminal alkynes from anti-2,3-dibromoalkanoic acids by microwave-induced reaction

Article abstract of DOI:10.1016/j.tet.2005.02.043

(Z)-1-Bromo-1-alkenes were stereoselectively prepared in high yields in a short reaction time by microwave irradiation of the corresponding anti-2,3-dibromoalkanoic acids in a Et₃N/DMF system. A one-pot synthesis of terminal alkynes and enynes from 2,3-dibromoalkanoic acids were also developed by microwave-induced reaction.

Full text of DOI:10.1016/j.tet.2005.02.043

Tetrahedron 61 (2005) 4043–4052
Synthesis of (Z)-1-bromo-1-alkenes and terminal alkynes from
anti-2,3-dibromoalkanoic acids by microwave-induced reaction
b
c
c
Chunxiang Kuang,a, Qing Yang, Hisanori Senboku and Masao Tokuda
*
aDepartment of Materials Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan
bDepartment of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku,
Tokyo 113-0033, Japan
cDivision of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Received 20 December 2004; accepted 14 February 2005
Abstract—(Z)-1-Bromo-1-alkenes were stereoselectively prepared in high yields in a short reaction time by microwave irradiation of the
corresponding anti-2,3-dibromoalkanoic acids in a Et3N/DMF system. A one-pot synthesis of terminal alkynes and enynes from 2,3-
dibromoalkanoic acids were also developed by microwave-induced reaction.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
Remarkable reductions in reaction times, clean conditions
and better yields have been reported in microwave-induced
reactions.8 In a preliminary paper,9 we reported a rapid and
convenient method for a stereoselective synthesis of (Z)-1-
bromoalkenes from the corresponding 2,3-dibromoalkanoic
acids using a Et3N/DMF system under microwave
irradiation. In this paper, we describe the details of
debrominative decarboxylation of 2,3-dibromoalkanoic
acids, including its mechanism and its uses for the
preparation of terminal alkynes and enynes in a one-pot
reaction (Scheme 1).
(Z)-1-Bromo-1-alkenes are an important synthetic inter-
mediate for stereospecific synthesis of substituted alkenes.
A variety of methods have been reported for the
stereocontrolled preparation of (Z)-1-bromo-1-alkenes,
including Wittig-type condensation,1 metal–halogen
exchange of metalloalkenes,2 hydroboration–protonolysis
of haloalkynes,3 palladium catalyzed hydrogenolysis of 1,1-
dibromo-1-alkenes by tributyltin hydride,4 transformation
of ketones using an appropriate acetyl halide in a strongly
acidic solvent,5 SmI2-mediated b-elimination of O-acetyl
dihalo alcohols,6 and debrominative decarboxylation of
cinnamic and acrylic acids dibromides.7 Debrominative
decarboxylation of brominated a,b-unsaturated carboxylic
acids might be one of the most useful methods for a
synthesis of (Z)-1-bromo-1-alkenes since the starting a,b-
unsaturated acids are readily available and the procedure is
very simple, especially, the reaction is easy to be operated in
a large scale. However, the yields are low in the case of
aliphatic (Z)-1-bromoalkenes and (Z)-b-bromostyrene
carrying ortho- and para-nitro-substituents even if an
improved procedure using triethylamine and DMF solvent
was used in these reactions.
2. Results and discussion
2.1. Stereoselective synthesis of (Z)-1-bromo-1-alkenes
Microwave irradiation of anti-2,3-dibromoalkanoic acids
(2), in DMF solution containing 1.05 equiv of triethylamine
for 0.2–1.0 min, gave the corresponding (Z)-1-bromo-1-
alkenes (3) in excellent yields and high (Z)-selectivities
(Scheme 1). anti-2,3-Dibromoalkanoic acids (2) were
readily obtained by bromination of the corresponding
trans-a,b-unsaturated carboxylic acids (1). The yields of
(Z)-3 and the ratios of (Z) and (E) are summarized in
Table 1. These results indicate that present reaction can be
used for the synthesis of both aromatic and aliphatic (Z)-1-
bromo-1-alkenes. Unsubstituted cinnamic acid dibromides
(2a and 2q) and those with electron-withdrawing group
(entries 3 and 4) were converted to the corresponding (Z)-b-
bromostyrenes (3a, 3q, 3g–i, 3k–l and 3m–p)in excellent
Recently, the method of microwave irradiation to effect
organic transformation has been used by organic chemists.
Keywords: (Z)-1-Bromo-1-alkenes; anti-2,3-Dibromoalkanoic acids;
Terminal alkynes; Enynes; Microwave irradiation.
Corresponding author. Tel.: C81 6 6879 4592; fax: C81 6 6850 5785;
e-mail: kuang@ch.wani.osaka-u.ac.jp
*
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.02.043

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C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
Scheme 1.
Table 1. Stereoselective synthesis of (Z)-1-bromo-1-alkenes
Entry
Dibromide (2)
Product (3)
MW (min)
0.5
Yield (%)a
95
Z/Eb
2a
3a
O98/2
1
EDG
4-CH3
4-CH3O
4-n-C7H15
3,4-OCH2O
2b
2c
2d
2e
2f
3b
3c
3d
3e
3f
0.5
0.5
0.5
0.5
98
95
96
99
97
98/2
75/25
90/10
95/5
O
2
3
3,4,5-(CH3O)3 0.5
X
82/18
2g
2h
2i
2j
2k
2l
3g
3h
3i
3j
3k
3l
4-Br
4-Cl
2-Cl
2,6-Cl2
4-F
3-F
1.0
1.0
1.0
1.0
1.0
1.0
96
96
94
92
98
98
O98/2
O98/2
98/2
85/15
O98/2
O98/2
EWG
4-CO2CH3
4-NO2
3-NO2
2-NO2
2m
2n
2o
3m
3n
3o
1.0
1.0
1.0
1.0
99
98
99
96
O98/2
O98/2
O98/2
O98/2
4
5
2p
3p
2q
2r
3q
3r
0.5
96
O98/2
6
7
0.5
98
65/35
2s
3s
1.0
73
O98/2
8
9
2t
3t
0.2
0.2
82
91
O98/2
O98/2
2u
3u
a Isolated yields of (Z)- and (E)-1-bromo-1-alkenes.
b Determined by 1H NMR.

C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
4045
group (entry 2) or there was a large steric hindrance in the
ortho position of the benzene ring (3j and 3r). The reaction
of pyridyl-substituted and aliphatic anti-2,3-dibromo-
alkanoic acids gave the corresponding (Z)-1-bromo-1-
alkenes (3s–u) with the complete Z selectivity and excellent
yields. All of these results indicate that the yields by the
present method are quite higher than those of previous
procedures.
Three proposed reaction pathways for the present debromi-
native decarboxylations are shown in Schemes 2–4. Most of
the reactions probably proceed via trans-elimination
involving simultaneous loss of carbon dioxide and bromide
ion to give (Z)-vinyl bromides (Scheme 2).
Scheme 2.
yields with high stereoselectivies. Even if weak electron-
donating group such as methyl and methyenedioxy were
contained in the molecules, the reaction stereoselectively
proceeded in high yields (3b and 3e). However, the Z/E
stereoselectivity was reduced to 65–90% when the benzene
ring (3c–f) was substituted with strong electron-donating
On the other hand, in the case of cinnamic acid dibromides
carrying strong electron-donating group such as alkyloxyl
Scheme 3.
Scheme 4.

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C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
observed when the microwave irradiation was lasted for a
longer time (2 min) or an excess base (3 equiv of Et3N) was
used. As to the second step (MW2), it was found that bases
such as Et3N, pyridine, DABCO, NaOH, K2CO3 or t-BuOK
were not effective in this one-pot reaction. 1,8-diazabicyclo-
[5.4.0]undec-7-ene (DBU) was found to be the best base in
this one-pot system. It would be very convenient for this
one-pot reaction to use same base in two successive steps.
Unfortunately, when DBU instead of Et3N was used in the
first step, a mixture of (Z)- and (E)-vinyl bromide
(approximate to 92/8) was formed, and this stereoselectivity
was much lower than those using Et3N. Since DBU did only
cause an elimination of (Z)-vinyl bromides under these
conditions, a mixture of terminal alkynes and unreacted (E)-
vinyl bromides was obtained. Under microwave irradiation
the reaction of anti-3-aryl-2,3-dibromopropanoic acids and
triethylamine in DMF followed by addition of DBU
proceeded smoothly to afford the corresponding terminal
alkynes in high yields. As shown in Table 2, these terminal
alkynes were obtained in high yields and in short reaction
time by the microwave irradiation method. The proposed
reaction pathway of the present elimination was shown in
Scheme 6. However, microwave irradiation of alkyl-
substituted 2,3-dibromoalkanoic acids by the same way
gave the corresponding aliphatic alkynes in low yields.
Scheme 5.
(2c–f), a unimolecular elimination process of bromide ion
to give relatively stable carbocations A and B would give
(Z)- and (E)-vinyl bromide, respectively, with a preferential
formation of (Z)-isomer (Scheme 3).
When a large steric hindrance is present at the ortho position
of the aryl ring, anion of anti-2,3-dibromoalkanoic acids (2j
and 2r) might undergo both cis and trans elimination to give
cis and trans isomer, respectively (Scheme 4).
2.2. A one-pot synthesis of terminal alkynes
Terminal alkynes are useful and versatile intermediates in
organic synthesis. In our continuous study, we have
developed a new procedure for one-pot conversion of
anti-3-aryl-2,3-dibromopropanoic acids (2) into terminal
alkynes (4) in excellent yields within a few minutes under
microwave irradiation (Scheme 5).
2.3. A one-pot synthesis of enynes
Various conditions were examined to optimize the yields of
terminal alkynes. In the first step (MW1), treatment of anti-
3-aryl-2,3-dibromopropanoic acids with triethylamine in
DMF under microwave irradiation within 0.5–1.0 min
resulted in (Z)-1-bromo-1-alkenes with high Z/E selectivity
and excellent yields. No remarkable improvement of the
yields and stereoselectivities of (Z)-1-bromo-1-alkenes was
Furthermore, we applied this transformation to a one-pot
synthesis of enynes from anti-2,3-dibromoalkanoic acids.
Microwave irradiation of a mixture of anti-2,3-dibromo-3-
phenylpropanoic acid (2a), Et3N and DMF for 1 min and
subsequent microwave irradiation of the mixture in the
presence of ethynylbenzene, Pd(PPh3)4, CuI and Et3N for
Table 2. One-pot synthesis of terminal alkynes by microwave irradiation of anti-3-aryl-2,3-dibromopropanoic acids
Entry
1
Dibromide (2)
Product (4)
MW1/MW2 (min)
0.5/1.0
Yield (%)a
88
2a
4a
4g
4h
2
3
2g
2h
1.0/1.0
1.0/1.0
95
93
4
2i
4i
1.0/1.0
1.0/1.0
90
99
5
2m
4m
a Isolated yields.
Scheme 6.

C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
4047
Scheme 7.
2 min gave the desired product 5a in 52% yield (Scheme 7).
The one-pot synthetic method is convenient for operation in
comparison with a two-step strategy. The enynes could be
obtained directly from anti-2,3-dibromo-3-arylpropanoic
acid (2) without the isolation of (Z)-1-bromo-1-alkenes (3)
which is an unstable intermediate. Furthermore, the two-
step method does not have any advantage in yield over the
one-pot method. By a two-step synthetic method, 3a was
obtained with a 95% isolated yield in the first step then
subjected to the next coupling step. The enyne 5a was
obtained in 55% yield in the second step under the same
condition as that of the one-pot method. Thus, the total yield
of a two-step reaction was almost same as that of the one-pot
reaction. Conjugated enynes are of great interest in organic
synthesis.
procedure reported in the literature.10–12 The physical data
of 1d, 1m, 1t and 1u are shown below.
4.1.1. 4-Heptyloxy-trans-cinnamic acid (1d). Mp 148 8C
(AcOH) (lit.10 148 8C); IR (nujol) 1795, 1573, 723 cmK1
;
1H NMR (CDCl3Cd6-DMSO) d 0.89 (3H, t, JZ6.6 Hz),
1.30–1.47 (8H, m), 1.78 (2H, tq, JZ6.6 Hz), 3.96 (2H, t,
JZ6.6 Hz), 6.29 (1H, d, JZ15.8 Hz), 6.88 (2H, d, JZ
8.6 Hz), 7.46 (2H, d, JZ8.6 Hz), 7.64 (1H, d, JZ15.8 Hz);
13C NMR d 13.89, 22.39, 25.75, 28.82, 28.93, 31.55, 67.92,
114.61, 115.65, 126.75, 129.52, 144.54, 160.73, 169.45.
4.1.2. 4-Methoxycarbonylcinnamic acid (1m). Mp 246–
247 8C (H2O–MeOH); IR (nujol) 1717, 1687, 1282 cmK1
;
1H NMR (CDCl3Cd6-DMSO) d 3.92 (3H, s), 6.51 (1H, d,
JZ16.1 Hz), 7.60 (2H, d, JZ8.2 Hz), 7.65 (1H, d, JZ
16.1 Hz), 8.03 (2H, d, JZ8.2 Hz); 13C NMR d 51.39,
120.71, 127.04, 129.16, 130.24, 138.00, 142.01, 165.44,
167.16; EIMS m/z 206 (MC, 38), 191 (20), 175 (100), 147
(32); HRMS calcd for C11H10O4. m/z 206.0579. Found m/z
206.0579.
3. Conclusions
In summary, we have developed a facile method for
stereoselective synthesis of (Z)-1-bromo-1-alkenes from
the corresponding anti-2,3-dibromoalkanoic acids using a
Et3N/DMF system, in which the use of microwave
irradiation enables the preparation of (Z)-1-bromo-1-
alkenes in high yields and high stereoselectivities within
0.2–1.0 min of reaction time. Additionally, we applied this
transformation to a one-pot synthesis of terminal alkynes
and enynes under microwave irradiation.
4.1.3. trans-3-Cyclohexylacrylic acid (1t). Mp 57–58 8C
(hexane) (lit.11 58–59 8C); IR (nujol) 1774, 1695, 985 cmK1
;
1H NMR d 1.07–1.48 (5H, m), 1.66–1.96 (5H, m), 2.10–
2.21 (1H, m), 5.77 (1H, d, JZ15.8 Hz), 7.03 (1H, dd, JZ
15.8, JZ6.6 Hz); EIMS m/z 154 (MC, 26), 82 (88), 67
(100); 13C NMR d 25.60, 25.84, 31.48, 40.48, 118.27,
157.16, 172.83.
4.1.4. trans-Dec-2-enoic acid (1u). Bp 98 8C/0.07 mm Hg
(lit.12 98 8C/0.07 mm Hg); IR (neat) 1774, 1695, 981 cmK1
;
4. Experimental
1H NMR d 0.88 (3H, t, JZ6.9 Hz), 1.28–1.64 (10H, m),
2.18–2.26 (2H, m), 5.82 (1H, d, JZ15.8 Hz), 7.03–7.14
(1H, m); 13C NMR d 13.98, 22.57, 27.83, 29.00, 29.05,
31.68, 32.57, 120.61, 152.45, 172.41.
Melting points were recorded using a Yanagimoto micro
melting point apparatus and were uncorrected. IR spectra
were recorded using a JASCO IR-810 infrared spectrometer
(between NaCl plates). 1H 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.
Chemical shifts are reported in ppm (d) using 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
carried out on a Silica Gel 60 N (100–210 mm, Kanto
Chemical Co. Ltd).
4.2. General procedure for the preparation of anti-2,3-
dibromoalkanoic acids (2)
anti-2,3-Dibromoalkanoic acids (2a–u) were prepared
according to the previous described procedure.7i,7j
4.2.1. anti-2,3-Dibromo-3-phenylpropanoic acid (2a). Mp
1
197–198 8C (CHCl3) (lit.13 196–198 8C); H NMR d 4.88
(1H, d, JZ11.5 Hz), 5.33 (1H, d, JZ11.5 Hz), 7.38–7.43
(5H, m).
4.1. General procedure for the preparation of trans-a,b-
unsaturated carboxylic acids (1)
4.2.2. anti-2,3-Dibromo-3-(4-methylphenyl)propanoic
acid (2b). Mp 191–192 8C (CHCl3) (lit.7i 192 8C); 1H
NMR d 2.35 (3H, s) 4.88 (1H, d, JZ11.5 Hz), 5.32 (1H, d,
Acids (1a–c, 1e–l, 1n–s) were commercially available.
Acids (1d, 1m, 1t and 1u) were prepared according to the

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C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
JZ11.5 Hz), 7.20 (2H, d, JZ8.0 Hz), 7.30 (2H, d, JZ
8.0 Hz).
17), 245 (43), 121 (100); HRMS calcd for C9H779Br81Br
FO2. m/z 325.8777. Found m/z 325.8768.
4.2.3. anti-2,3-Dibromo-3-(4-methoxyphenyl)propanoic
4.2.12. anti-2,3-Dibromo-3-(3-fluorophenyl)propanoic
acid (2l).7i Mp 196–197 8C (CHCl3); IR (nujol) 1716,
1
acid (2c). Mp 155–156 8C (CHCl3) (lit.7i 155–156 8C); H
1
NMR d 3.83 (3H, s), 4.86 (1H, d, JZ11.9 Hz), 5.34 (1H, d,
JZ11.9 Hz), 6.92 (2H, d, JZ8.6 Hz), 7.34 (2H, d, JZ
8.6 Hz).
1591, 1146 cmK1; H NMR d 4.92 (1H, d, JZ11.5 Hz),
5.38 (1H, d, JZ11.5 Hz), 7.06–7.75 (4H, m); 13C NMR d
46.86, 49.32, 113.98 (d, JZ22.0 Hz), 114.92 (d, JZ
20.7 Hz), 123.02 (d, JZ3.6 Hz), 129.32 (d, JZ7.3 Hz),
139.60 (d, JZ7.1 Hz), 161.25 (d, JZ246.5 Hz), 168.20;
EIMS m/z 326 ((MC2)C, 35), 324 (MC, 20), 245 (42), 121
(100); HRMS calcd for C9H779Br81Br FO2. m/z 323.8796.
Found m/z 323.8796.
4.2.4. anti-2,3-Dibromo-3-(4-heptyloxyphenyl)propanoic
acid (2d). Mp 83–84 8C (hexane); IR (film) 1717, 1609,
1
1514 cmK1; H NMR d 0.89 (3H, t), 1.31–1.48 (8H, m),
1.77 (2H, dd, JZ6.6 Hz), 3.97 (2H, t, JZ6.6 Hz), 4.88 (1H,
d, JZ11.5 Hz), 5.34 (1H, d, JZ11.5 Hz), 6.90 (2H, d, JZ
8.6 Hz), 7.33 (2H, d, JZ8.6 Hz); 13C NMR d 14.07, 22.59,
25.96, 29.02, 29.16, 31.75, 46.74, 50.46, 68.10, 114.79,
128.91, 129.32, 159.91, 173.35; EIMS m/z 422 ((MC2)C,
4.2.13. anti-2,3-Dibromo-3-(4-methoxycarbonylphenyl)-
propanoic acid (2m). Mp 208–209 8C (acetone–hexane);
IR (film) 1718, 1508, 1436 cmK1; 1H NMR d 3.92 (3H, s),
4.79 (1H, d, JZ11.5 Hz), 5.37 (1H, d, JZ11.5 Hz), 7.48
(2H, d, JZ8.2 Hz), 8.06 (2H, d, JZ8.2 Hz); 13C NMR d
46.92, 49.63, 52.20, 128.10, 130.00, 130.71, 130.71, 142.64,
3), 420 (MC, 5), 198 (50), 107 (100); HRMS calcd for
79
C16H Br2O3. m/z 419.9936. Found m/z 419.9919. Anal.
Calcd for C16H22Br2O3: C, 45.52, H, 5.25, Br, 37.86. Found:
C, 45.50, H, 5.21, Br, 37.88.
22
166.25, 169.30; EIMS m/z 366 ((MC2)C, 13), 364 (MC,
79
10), 285 (45), 175 (100); HRMS calcd for C11H Br2O4. m/z
10
4.2.5. anti-2,3-Dibromo-3-(3,4-methylenedioxyphenyl)-
propanoic acid (2e).14 Mp 143–144 8C (CHCl3); 1H
NMR d 4.81 (1H, d, JZ11.8 Hz), 5.28 (1H, d, JZ
11.8 Hz), 6.01 (2H, s), 6.77–6.90 (3H, m).
363.8946. Found m/z 363.8942. Anal. Calcd for
C11H10Br2O4: C, 36.10, H, 2.75, Br, 43.66. Found: C,
36.05, H, 2.78, Br, 43.70.
4.2.14. anti-2,3-Dibromo-3-(4-nitrophenyl)propanoic
acid (2n). Mp 216–217 8C (AcOH) (lit.,18 216–217 8C);
4.2.6. anti-2,3-Dibromo-3-(3,4,5-trimethoxyphenyl)pro-
panoic acid (2f). Mp 154–155 8C (benzene–hexane) (lit.15
153–155 8C); 1H NMR d 3.86 (3H, s), 3.88 (3H!2, s), 4.78
(1H, d, JZ11.5 Hz), 5.29 (1H, d, JZ11.5 Hz), 6.63 (2H, s).
1
IR (nujol) 1715, 1515, 1366 cmK1; H NMR (CDCl3Cd6-
DMSO) d 4.85 (1H, d, JZ11.8 Hz), 5.43 (1H, d, JZ
11.8 Hz), 7.65 (2H, d, JZ8.9 Hz), 8.25 (2H, d, JZ8.9 Hz).
4.2.7. anti-2,3-Dibromo-3-(4-bromophenyl)propanoic
acid (2g). Mp 191–192 8C (EtOH) (lit.7i 192 8C); 1H
NMR d 4.84 (1H, d, JZ11.5 Hz), 5.28 (1H, d, JZ
11.5 Hz), 7.29 (2H, d, JZ8.6 Hz), 7.54 (2H, d, JZ8.6 Hz).
4.2.15. anti-2,3-Dibromo-3-(3-nitrophenyl)propanoic
acid (2o). Mp 172–173 8C (AcOH) (lit.7i 172 8C); IR (film)
1
1709, 1680, 1541, 1356 cmK1; H NMR d 4.86 (1H, d, JZ
11.8 Hz), 5.39 (1H, d, JZ11.8 Hz), 7.61 (1H, t, JZ7.9 Hz),
7.75 (1H, d, JZ8.9 Hz), 8.26 (2H, dt, JZ8.9, 7.9 Hz).
4.2.8. anti-2,3-Dibromo-3-(4-chlorophenyl)propanoic
acid (2h). Mp 194–195 8C (acetone–hexane) (lit.16 194–
195 8C); IR (nujol) 1719, 721 cmK1; 1H NMR d 4.82 (1H, d,
JZ11.5 Hz), 5.30 (1H, d, JZ11.5 Hz), 7.20–7.40 (4H, m).
4.2.16. anti-2,3-Dibromo-3-(2-nitrophenyl)propanoic
acid (2p). Mp 179–180 8C (benzene) (lit.7i 180 8C); IR
(nujol) 1711, 1540, 1351 cmK1 1H NMR (CDCl3Cd6-
;
DMSO) d 4.89 (1H, d, JZ11.8 Hz), 6.10 (1H, d, JZ
11.8 Hz), 7.51–7.58 (1H, m), 7.73–7.79 (2H, m), 7.91 (1H,
d, JZ7.9 Hz).
4.2.9. anti-2,3-Dibromo-3-(2-chlorophenyl)propanoic
acid (2i). Mp 175–176 8C (acetone–hexane) (lit.17 175–
1
176 8C); H NMR d 4.98 (1H, d, JZ11.5 Hz), 5.92 (1H, d,
JZ11.5 Hz), 7.28–7.51 (4H, m); 13C NMR d 44.68, 45.01,
127.68, 130.25, 130.47, 134.05, 134.84, 173.06.
4.2.17. anti-2,3-Dibromo-3-(2-naphthyl)propanoic acid
(2q). Mp 178–180 8C (EtOH) (lit.19 177–180 8C); 1H NMR
(CDCl3Cd6-DMSO) d 4.98 (1H, d, JZ11.8 Hz), 5.56 (1H,
d, JZ11.8 Hz), 7.50–7.56 (3H, m), 7.83–7.91 (4H, m); 13C
NMR d 47.06, 51.23, 123.95, 126.02, 126.28, 126.99,
127.13, 127.43, 128.28, 132.00, 132.61, 134.46, 168.98.
4.2.10. anti-2,3-Dibromo-3-(2,6-dichlorophenyl)pro-
panoic acid (2j). Mp 193–194 8C (acetone–hexane) (lit.17
1
193–194 8C); H NMR d 5.69 (1H, d, JZ11.8 Hz), 6.37
(1H, d, JZ11.8 Hz), 7.25–7.28 (1H, m), 7.35–7.41 (2H, m);
EIMS m/z 376 ((MC2)C, 8), 374 (MC, 5), 297 (62), 181
(64), 171 (100); HRMS calcd for C9H769Br235Cl2O2. m/z
373.8111. Found m/z 373.8124.
4.2.18. anti-2,3-Dibromo-3-(1-naphthyl)propanoic acid
(2r). Mp 181–182 8C (CCl4) (lit.20 181–182 8C); 1H NMR d
5.14 (1H, d, JZ11.5 Hz), 6.29 (1H, d, JZ11.5 Hz), 7.44–
7.93 (6H, m), 8.16 (1H, d, JZ8.6 Hz).
4.2.11. anti-2,3-Dibromo-3-(4-fluorophenyl)propanoic
acid (2k).7i Mp 191–192 8C (CHCl3); IR (nujol) 1718,
4.2.19. anti-2,3-Dibromo-3-pyridin-3-yl-propanoic acid
(2s).7j Mp 169–170 8C (CHCl3); 1H NMR (d6-DMSOC
CDCl3) d 5.35 (1H, d, JZ11.5 Hz), 5.82 (1H, d, JZ
11.5 Hz), 7.36 (1H, m), 8.48 (1H, m), 8.76 (1H, d, JZ
3.9 Hz), 9.06 (1H, s); 13C NMR d 44.61, 45.83, 127.49,
130.51, 141.93, 142.15, 145.44, 168.31.
1600, 1591, 1509 cmK1 1H NMR d 4.83 (1H, d, JZ
;
11.5 Hz), 5.32 (1H, d, JZ11.5 Hz), 7.10 (2H, m), 7.40 (2H,
m); 13C NMR d 47.17, 49.68, 115.11 (d, JZ22.0 Hz),
129.37 (d, JZ8.6 Hz), 133.39 (d, JZ3.7 Hz), 161.95 (d, JZ
249.1 Hz), 168.64; EIMS m/z 328 ((MC2)C, 8), 326 (MC,

C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
4049
4.2.20. anti-2,3-Dibromo-3-cyclohexylpropanoic acid
(2t).21 Mp 158–159 8C (hexane); 1H NMR d 1.14–1.84
(10H, m), 1.94–2.03 (1H, m), 4.36 (1H, dd, JZ11.8, JZ
2.3 Hz), 4.53 (1H, d, JZ11.8 Hz); 13C NMR d 25.39, 25.51,
25.91, 25.95, 32.05, 38.95, 45.14, 59.01, 173.78.
E),6.88 (2H, d, JZ8.6 Hz), 6.98 (0.90H, d, JZ7.9 Hz, Z),
7.65 (2H, d, JZ8.6 Hz); 13C NMR d 14.05, 22.57, 25.95,
29.02, 29.16, 31.73, 67.89, 103.81, 114.03, 114.61, 127.20,
130.37, 131.59, 159.03; EIMS m/z 298 ((MC2)C, 99), 296
(MC, 100), 200 (100), 198 (98), 119 (65); HRMS calcd for
79
C15H BrO. m/z 296.0776. Found m/z 296.0757. Anal.
Calcd for C15H21BrO: C, 60.61, H, 7.12, Br, 26.88. Found:
C, 60.52, H, 7.08, Br, 26.93.
21
4.2.21. anti-2,3-Dibromodecanoic acid (2u). Mp 44–45 8C
(hexane) (lit.7i 45 8C); IR (nujol) 1728, 1285 cmK1 1H
;
NMR d 0.89 (3H, t, JZ3.9 Hz), 1.22–1.48 (10H, m), 1.50–
1.64 (2H, m), 4.31–4.47 (2H, m).
4.3.5. (Z)-b-Bromo-3,4-methylenedioxystyrene (3e).14
Colorless oil; IR (neat) 1611, 1503, 1489, 965, 940 cmK1
;
1H NMR d 5.98 (2H, s), 6.29 (1H, d, JZ7.9 Hz), 6.81 (1H,
d, JZ7.9 Hz), 6.95 (1H, d, JZ8.2 Hz), 7.02–7.10 (1H, m),
7.38 (1H, d, JZ1.3 Hz); 13C NMR d 101.16, 104.50,
108.05, 108.66, 123.78, 128.87, 131.64, 147.34, 147.45;
EIMS m/z 228 ((MC2)C, 99), 226 (MC, 100), 149 (97);
HRMS calcd for C9H779BrO2. m/z 225.9630. Found m/z
225.9627.
4.3. General procedure for the preparation of (Z)-1-
bromo-1-alkene (3)
A mixture of anti-2,3-dibromoalkanoic acid (1 mmol) and
triethylamine (1.05 mmol) was added to 2 ml DMF. The
mixture was kept inside a microwave oven operated at
2450 MHz (TOSHIBA, ER-V11, 200 W) and was irradiated
for 0.2–1.0 min without any stirring. The reaction mixture
was then removed from the oven and cooled to room
temperature. Water and ether were added to the reaction
mixture and the organic layer was separated. Aqueous layer
was extracted with ether. The combined organic layers were
washed with water and brine, and dried over anhydrous
magnesium sulfate. After evaporation of the solvent, the
crude product was purified by column chromatography on
silica gel with EtOAc–hexane to give (Z)-1-bromo-1-alkene
(3). Large scale reaction using 20 mmol of anti-2,3-
dibromoalkanoic acid was also operated in the same way.
4.3.6. (Z/E)-b-Bromo-3,4,5-trimethoxystyrene (3f).23
1
Colorless oil; IR (neat) 1615, 1581, 970 cmK1; H NMR d
3.84 (0.54H, s, E), 3.86 (1.08H, s, E), 3.87 (2.46H, s, Z),
3.88 (4.92H, s, Z), 6.37 (0.82H, d, JZ8.2 Hz, Z), 6.51
(0.36H, s, E), 6.69 (0.18H, d, JZ13.9 Hz, E), 6.97–7.05
(2.64H, m); 13C NMR d 55.99, 60.72, 103.12, 105.44,
106.20, 130.15, 131.89, 152.74; EIMS m/z 274 ((MC2)C,
100), 272 (MC, 100), 259 (96), 229 (75); HRMS calcd for
79
C11H BrO3. m/z 272.0048. Found m/z 272.0044.
13
4.3.7. (Z)-b-Bromo-4-bromostyrene (3g).7i Colorless oil;
1
4.3.1. (Z)-b-Bromostyrene (3a).4c Colorless oil; IR (neat)
IR (neat) 1612, 1587, 1486, 1010 cmK1; H NMR d 6.45
1
1616, 1491, 925, 771 cmK1; H NMR d 6.43 (1H, d, JZ
(1H, d, JZ8.2 Hz), 6.98 (1H, d, JZ8.2 Hz), 7.48 (2H, d,
JZ8.6 Hz), 7.54 (2H, d, JZ8.6 Hz); 13C NMR d 107.26,
122.24, 130.44, 131.21, 131.35, 133.71; EIMS m/z 264
((MC4)C, 8), 262 ((MC2)C, 100), 260 (MC, 51), 181 (31),
102 (55); HRMS calcd for C8H769Br2. m/z 259.8836. Found
m/z 259.8839.
8.2 Hz), 7.07 (1H, d, JZ8.2 Hz), 731–7.40 (3H, m), 7.66–
7.69 (2H, m); 13C NMR d 106.31, 128.17, 128.26, 128.93,
132.29, 134.83; EIMS m/z 184((MC2)C, 92), 182 (MC,
97), 103 (100), 77 (42); HRMS calcd for C8H779Br. m/z
181.9731. Found m/z 181.9734.
4.3.2. (Z)-b-Bromo-4-methylstyrene (3b).4c Colorless oil;
4.3.8. (Z)-b-Bromo-4-chlorostyrene (3h).16 Colorless oil;
IR (neat) 1614, 1589, 1490, 1014, 946, 720 cmK1; 1H NMR
d 6.45 (1H, d, JZ7.9 Hz), 7.12 (1H, d, JZ7.9 Hz), 7.34
(2H, d, JZ8.2 Hz), 7.62 (2H, d, JZ8.2 Hz); 13C NMR d
107.17, 128.44, 130.22, 131.20, 133.31, 134.01; EIMS m/z
220 ((MC4)C, 43), 218 ((MC2)C, 43), 216 (MC, 30), 195
(100), 139 (28), 137 (60), 102 (40), 101 (45), 75 (31);
HRMS calcd for C8H769Br35Cl. m/z 215.9341. Found m/z
215.9335.
1
IR (neat) 1606, 1510, 947 cmK1; H NMR d 2.36 (3H, s),
6.36 (1H, d, JZ7.9 Hz), 7.02 (1H, d, JZ7.9 Hz), 7.17 (2H,
d, JZ7.9 Hz), 7.58 (2H, d, JZ7.9 Hz); 13C NMR d 21.33,
105.40, 128.89, 132.14, 138.26; EIMS m/z 198 ((MC2)C,
8),196 (MC, 8), 121 (100), 91 (44); HRMS calcd for
C9H799Br. m/z 195.9887. Found m/z 195.9890.
4.3.3. (Z/E)-b-Bromo-4-methoxystyrene (3c).22 Colorless
oil; IR (neat) 1608, 1574, 1511, 927 cmK1; 1H NMR d 3.80
(0.75H, s. E), 3.82 (2.25H, s, Z), 6.30 (0.75H, d, JZ8.2 Hz,
Z), 6.60 (0.25H, d, JZ13.9 Hz, E), 6.84 (0.5H, d, JZ
8.9 Hz, E), 6.88 (0.25H, d, JZ13.9 Hz, E), 6.90 (1.50H, d,
JZ8.9 Hz, Z), 6.99 (0.75H, d, JZ8.2 Hz, Z), 7.22 (0.50H, d,
JZ8.9 Hz, E), 7.67 (1.50H, d, JZ8.9 Hz, Z); 13C NMR d
55.18, 104.09, 113.54, 114.12, 127.31, 130.44, 131.59,
159.44; EIMS m/z 214 ((MC2)C, 99), 212 (MC, 100), 197
(85), 133 (68); HRMS calcd for C9H799BrO. m/z 211.9837.
Found m/z 211.9835.
4.3.9. (Z)-b-Bromo-2-chlorostyrene (3i). Colorless oil; IR
(neat) 1619, 1593, 1468, 1435, 946 cmK1; 1H NMR d 6.59
(1H, d, JZ8.2 Hz), 7.23–7.31 (3H, m), 7.37–7.44 (1H, m),
7.80–7.84 (1H, m); 13C NMR d 109.34, 126.20, 129.38,
129.90, 130.22, 133.24, 133.46; EIMS m/z 220 ((MC4)C,
11), 218 ((MC2)C, 42), 216 (MC, 32), 137 (100), 101 (52);
HRMS calcd for C8H769Br35Cl. m/z 215.9341. Found m/z
215.9322. Anal. Calcd for C8H6BrCl: C, 44.18, H, 2.78, Br,
36.74, Cl, 16.30. Found: C, 44.42, H, 2.90, Br, 36.11, Cl,
16.02.
4.3.4. (Z/E)-b-Bromo-4-heptyloxystyrene (3d). Colorless
oil; IR (neat) 1607, 1510, 924 cmK1; 1H NMR d 0.89 (3H, t,
JZ6.9 Hz), 1.20–1.47 (8H, m), 1.78 (2H, q, JZ6.9 Hz),
3.96 (2H, t, JZ6.6 Hz), 6.28 (0.90H, d, JZ7.9 Hz, Z), 6.59
(0.10H, d, JZ13.9 Hz, E), 6.86 (0.10H, d, JZ13.9 Hz,
4.3.10. (Z/E)-b-Bromo-2,6-dichlorostyrene (3j). Colorless
oil; IR (film) 1698, 1558, 1429, 978 cmK1; 1H NMR d 6.64
(0.15H, d, JZ14.5 Hz, E), 6.74 (0.85H, d, JZ7.6 Hz, Z),
6.97 (0.85H, d, JZ7.6 Hz, Z), 7.05 (0.15H, d, JZ14.5 Hz,

4050
C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
E); 7.15–7.30 (1H, m), 7.31–7.39 (2H, m); 13C NMR d
114.09, 127.85, 129.38, 129.47, 133.65, 134.28; EIMS m/z
254 ((MC4)C, 18), 252 ((MC2)C, 35), 250 (MC, 24), 181
(100), 137 (52); HRMS calcd for C8H759Br35Cl2. m/z
249.8952. Found m/z 249.8954. Anal. Calcd for
C8H5BrCl2: C, 38.14, H, 2.00, Br, 31.72, Cl, 28.14.
Found: C, 38.10, H, 2.02, Br, 31.75, Cl, 28.18.
4.3.17. (Z)-2-(b-Bromovinyl)naphthalene (3q).4c Color-
1
less oil; IR (film) 1615, 1592, 929 cmK1; H NMR d 6.52
(1H, d, JZ7.9 Hz), 7.23 (1H, d, JZ7.9 Hz), 7.47–7.51 (2H,
m), 7.80–7.85 (4H, m), 8.15 (1H, s); 13C NMR d 106.66,
126.27, 126.41, 126.47, 127.64, 127.71, 128.28, 128.57,
132.38, 132.99, 133.04, 136.90; EIMS m/z 234 ((MC2)C,
100), 232 (MC, 98), 153 (88), 127 (58); HRMS calcd for
C12H799Br. m/z 231.9888. Found m/z 231.9884.
4.3.11. (Z)-b-Bromo-4-fluorostyrene (3k).24 Colorless oil;
4.3.18. (Z/E)-1-(b-Bromovinyl)naphthalene (3r).4c Color-
1
IR (neat) 1602, 1506, 1327, 1237 cmK1; H NMR d 6.38
1
less oil; IR (neat) 1605, 1590, 935 cmK1; H NMR d 6.73
(1H, d, JZ8.2 Hz), 6.97–7.07 (3H, m), 7.61–7.67 (2H, m);
13C NMR d 106.12, 115.16 (d, JZ21.9 Hz), 130.75 (d, JZ
8.6 Hz), 130.93 (d, JZ3.6 Hz), 131.14, 162.30 (d, JZ
249.1 Hz); EIMS m/z 202 ((MC2)C, 92), 200 (MC, 95),
121 (100), 101 (65); HRMS calcd for C8H769BrF. m/z
199.9637. Found m/z 199.9637.
(0.65H, d, JZ7.9 Hz, Z), 6.76 (0.35H, d, JZ13.5 Hz, E),
7.39–7.59 (4H, m), 7.70 (0.65H, d, JZ7.2 Hz, Z), 7.79–7.92
(3H, m), 8.01–8.04 (0.35H, m, E); 13C NMR d 108.46 (E),
109.95 (Z), 123.61 (ECZ), 124.11 (Z), 124.15 (E), 125.08
(Z), 125.46 (E), 125.89 (Z), 126.03 (E), 126.18 (ZCE),
126.39 (E), 126.72 (Z), 128.44 (Z), 128.50 (E), 128.69 (E),
130.45 (E), 131.01 (Z), 131.30 (Z), 132.11 (Z), 133.42 (Z),
133.50 (E), 134.91 (E); EIMS m/z 234 ((MC2)C, 92), 232
(MC, 93), 153 (100), 126 (75); HRMS calcd for C12H799Br.
m/z 231.9894. Found m/z 231.9893.
4.3.12. (Z)-b-Bromo-3-fluorostyrene (3l).24 Colorless oil;
1
IR (neat) 1609, 1582, 950 cmK1; H NMR d 6.47 (1H, d,
JZ8.2 Hz), 6.98–7.03 (2H, m), 7.27–7.49 (3H, m); 13C
NMR d 107.70, 115.19 (d, JZ20.8 Hz), 115.50 (d, JZ
21.9 Hz), 148.89 (d, JZ3.7 Hz), 129.67 (d, JZ8.5 Hz),
131.24 (d, JZ2.4 Hz), 136.89 (d, JZ7.3 Hz), 162.45 (d, JZ
245.4 Hz); EIMS m/z 202 ((MC2)C, 77), 200 (MC, 80),
121 (100), 101 (62); HRMS calcd for C8H769BrF. m/z
199.9637. Found m/z 199.9643.
4.3.19. (Z)-3-(b-Bromovinyl)pyridine (3s).4c Colorless oil;
1
IR (neat) 1617, 1567, 954 cmK1; H NMR d 6.57 (1H, d,
JZ8.2 Hz), 7.05 (1H, d, JZ8.2 Hz), 7.28 (1H, dd, JZ7.9,
4.3 Hz), 8.13 (1H, d, JZ7.9 Hz), 8.53 (1H, d, JZ4.3 Hz),
8.76 (1H, s); 13C NMR d 109.21, 123.07, 129.14, 130.96,
135.50, 149.07, 150.27; EIMS m/z 185 ((MC2)C, 96), 183
(MC, 94), 104 (100), 77 (41); HRMS calcd for C7H769BrN.
m/z 182.9684. Found m/z 182.9682.
4.3.13. (Z)-Methyl-4-(b-bromovinyl)benzoate (3m). Mp
43–44 8C (hexane); IR (film) 1722, 1609, 1565, 967 cmK1
;
1H NMR d 3.93 (3H, m), 7.56 (1H, d, JZ8.2 Hz), 7.12 (1H,
d, JZ8.2 Hz), 7.74 (2H, d, JZ8.6 Hz), 8.04 (2H, d, JZ
8.6 Hz); 13C NMR d 52.167, 108.73, 128.84, 129.47, 129.59,
131.61, 139.30, 166.68; EIMS m/z 242 ((MC2)C, 47), 240
(MC, 48), 209 (37), 211 (98), 209 (99), 183 (73), 181 (85), 102
(68); HRMS calcd for C10H799BrO2. m/z 239.9786. Found m/z
239.9790. Anal. Calcd for C10H9BrO2: C, 49.82, H, 3.76, Br,
33.14. Found: C, 49.73, H, 3.85, Br, 33.17.
4.3.20. (Z)-1-Bromo-2-cyclohexylethene (3t).4c Colorless
oil; IR (neat) 1412, 1261, 929, 701 cmK1; 1H NMR d 1.05–
1.43 (5H, m), 1.61–1.73 (5H, m), 5.92 (1H, dd, JZ6.9,
8.9 Hz), 6.04 (1H, dd, JZ1.0 Hz, 6.9 Hz); 13C NMR d
25.55, 25.91, 31.57, 38.82, 105.42, 140.16; EIMS m/z 190
((MC2)C, 7), 188 (MC, 8), 109 (100), 67 (94); HRMS
79
calcd for C8H Br. m/z 188.0201. Found m/z 188.0190.
13
4.3.14. (Z)-b-Bromo-4-nitrostyrene (3n).7i Colorless oil;
IR (film) 1594, 1509, 1341, 856 cmK1; 1H NMR d 6.68 (1H,
d, JZ8.2 Hz), 7.15 (1H, d, JZ8.2 Hz), 7.83 (2H, d, JZ
8.9 Hz), 8.24 (2H, d, JZ8.9 Hz); 13C NMR d 110.75,
123.52, 129.66, 130.65, 141.25; EIMS m/z 229 ((MC2)C,
100), 227 (MC, 100), 182 (60), 181 (61), 102 (81); HRMS
calcd for C8H769BrNO2. m/z 226.9582. Found m/z 226.9584.
4.3.21. (Z)-1-Bromonon-1-ene (3u).7i Colorless oil; IR
(neat) 1623, 939 cmK1; 1H NMR d 0.88 (3H, t, JZ6.6 Hz),
1.21–1.44 (10H, m), 2.18 (2H, q, JZ6.9 Hz), 6.04–6.15
(2H, m); 13C NMR d 14.09, 22.64, 28.14, 29.09, 29.68,
31.79, 107.49, 135.04; EIMS m/z 206 ((MC2)C, 30), 204
(MC, 31), 119 (20), 69 (82), 43 (100); HRMS calcd for
79
C9H Br. m/z 204.0514. Found m/z 204.0522.
17
4.3.15. (Z)-b-Bromo-3-nitrostyrene (3o).7i Colorless oil;
4.4. General procedure for the one-pot synthesis of
terminal alkynes (4)
1
IR (neat) 1611, 1592, 1574, 1532, 1351, 924 cmK1; H
NMR d 6.64 (1H, d, JZ8.2 Hz), 7.14 (1H, d, JZ8.2 Hz),
7.56 (1H, t, JZ7.9 Hz), 7.98 (1H, d, JZ7.9 Hz), 8.17 (1H,
m), 8.55 (1H, s); 13C NMR d 109.77, 122.87, 123.59,
129.20, 130.27, 134.71, 136.42, 148.07; EIMS m/z 229
((MC2)C, 100), 227 (MC, 100), 182 (80), 181 (80), 102
(71); HRMS calcd for C8H769BrNO2. m/z 226.9582. Found
m/z 226.9594.
A mixture of anti-3-aryl-2,3-dibromopropanoic acids (2,
1.0 mmol) and triethylamine (1.05 mmol) was added to 2 ml
DMF. The mixture was kept inside a microwave oven
operated at 2450 MHz (TOSHIBA, ER-V11, 200 W) and
was irradiated for 0.5–1.0 min without any stirring. The
reaction mixture was then removed from the oven and
cooled to room temperature. DBU (2.0 mmol) was added to
the reaction mixture and the mixture was also irradiated for
1.0 min without any stirring. Water and ether were added to
the reaction mixture and the organic layer was separated.
Aqueous layer was extracted with ether. The combined
organic layers were washed with water and brine, and dried
over anhydrous magnesium sulfate. After evaporation of the
4.3.16. (Z)-b-Bromo-2-nitrostyrene (3p).7i Colorless oil;
1
IR (film) 1604, 1571, 1524, 1345, 960 cmK1; H NMR d
6.62 (1H, d, JZ7.9 Hz), 7.45–7.60 (2H, m), 7.62–7.71 (2H,
m), 8.09–8.12 (1H, m); 13C NMR d 110.19, 124.71, 129.00,
130.19, 130.80, 131.75, 133.15, 147.38; EIMS m/z 148
(MCKBr, 46), 102 (32), 92 (100).

C. Kuang et al. / Tetrahedron 61 (2005) 4043–4052
4051
solvent, the crude product was purified by column
chromatography on silica gel with EtOAc–hexane to give
terminal alkynes (4).
oil; IR (neat) 3061, 3022, 2185, 1595, 1449 cmK1
;
1H
NMR d 5.91 (1H, d, JZ12.0 Hz), 6.69 (1H, d, JZ12.0 Hz),
7.28–7.43 (10H, m); 13C NMR d 138.65, 136.53, 131.48,
128.75, 128.48, 128.38, 128.32, 128.28, 123.43, 107.36,
95.83, 88.23; EIMS m/z 204 (MC, 31), 119 (20), 69 (82), 43
(100); HRMS calcd for C16H12. m/z 204.0939. Found m/z
204.0938.
4.4.1. Ethynylbenzene (4a).25 Colorless oil; IR (neat) 3290,
2108, 1599, 1575, 1489, 1445, 1071, 1026 cmK1; 1H NMR
d 3.05 (1H, s), 7.27–7.31 (3H, m), 7.46–7.49 (2H, m); 13C
NMR d 77.18, 83.59, 122.06, 128.24, 128.71, 132.05.
4.4.2. 4-Bromo-1-ethynylbenzene (4g).26 Mp 63.5–64.5 8C
(hexane); IR (nujol) 3312, 2110, 1485, 1071, 825 cmK1; 1H
NMR d 3.12 (1H, s), 7.35 (2H, d, JZ8.5 Hz), 7.46 (2H, d,
JZ8.5 Hz); 13C NMR d 78.33, 82.55, 121.04, 123.12,
131.59, 133.54; EIMS m/z 182 ((MC2)C, 90), 180 (MC,
100), 101 (92), 75 (52); HRMS calcd for C8H759Br. m/z
179.9575. Found m/z 179.9575.
Acknowledgements
This work was supported by a Grant-in-Aid for Exploratory
Research (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 Instru-
mental Analysis, Hokkaido University) for their assistance
in measurement of mass spectra.
4.4.3. 4-Chloro-1-ethynylbenzene (4h).27 Mp 45–46 8C
(hexane); IR (nujol) 3272, 2110 cmK1; 1H NMR d 3.10 (1H,
s), 7.29 (2H, d, JZ8.5 Hz), 7.41 (2H, d, JZ8.5 Hz); 13C NMR
d 78.15, 82.49, 120.57, 128.65, 133.33, 134.90; EIMS m/z 138
((MC2)C, 38), 136 (MC, 100), 101 (40), 75 (37); HRMS
calcd for C8H5Cl. m/z 136.0080. Found m/z 136.0077.
References and notes
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4.4.4. 2-Chloro-1-ethynylbenzene (4i).28 Colorless oil; IR
(neat) 3312, 2114, 1485, 1071, 825 cmK1; 1H NMR d 3.12
(1H, s), 7.35 (2H, d, JZ8.5 Hz), 7.46 (2H, d, JZ8.5 Hz);
13C NMR d 78.33, 82.55, 121.04, 123.12, 131.59, 133.54;
EIMS m/z 138 ((MC2)C, 35), 136 (MC, 100), 101 (38), 75
(34); HRMS calcd for C8H5Cl. m/z 136.0080. Found m/z
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4.4.5. Methyl 4-ethynylbenzoate (4m).29 Mp 94–95 8C
1
(hexane–EtOAc); IR (nujol) 2106, 1733, 1275 cmK1; H
NMR d 3.23 (1H, s), 3.92 (3H, s), 7.55 (2H, d, JZ8.5 Hz),
7.98 (2H, d, JZ8.5 Hz); 13C NMR d 52.25, 80.00, 82.77,
126.73, 129.43, 130.11, 132.05, 166.39; EIMS m/z 160
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`
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mixture was kept inside a microwave oven and was
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organic layers were washed with water and brine, and dried
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