Polymer-supported β-bromoethyl selenide: An efficient reagent for the synthesis of aryl vinyl ethers

Article abstract of DOI:10.1055/s-2004-834874

A simple and efficient procedure for the solid-phase synthesis of aryl vinyl ethers using polymer-supported β-bromoethyl selenide with traceless linker strategy is described.

Full text of DOI:10.1055/s-2004-834874

PAPER
2833
Polymer-Supported b-Bromoethyl Selenide: An Efficient Reagent for the
Synthesis of Aryl Vinyl Ethers
P
olymer-Supp
h
orted
b
-Brom
o
oethyl Selen
u
ide -Ri Sheng,* Xiao-Ling Liu, Xing-Cong Wang, Qin Xin, Cai-Sheng Song
Institutes of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, 330027, P. R. China
Fax +86(791)8517500; E-mail: shengsr@163.com
Received 30 June 2004; revised 17 August 2004
R
Abstract: A simple and efficient procedure for the solid-phase syn-
thesis of aryl vinyl ethers using polymer-supported b-bromoethyl
selenide with traceless linker strategy is described.
OH
(3a–3h)
C2H4
SeBr
SeCH2CH2Br
THF, r.t.
K2CO3, NBu4I, KI
DMF, r.t.
Key words: solid-phase organic synthesis, polymer-supported b-
bromoethyl selenide, aryl vinyl ether, oxidation-elimination
1
2
R
H2O2
THF, r.t.
OCH=CH2
SeCH2CH2O
Vinyl ethers are valuable intermediates that can be used in
a wide array of chemical transformations.1 More specifi-
cally, aryl vinyl ethers with unsubstituted vinyl moiety,
have been involved in reactions such as [2+2],2 [2+4]3 and
1,3-dipolar cycloadditons,4 and hydroformylation,5 etc.
Aryl vinyl ethers are usually prepared according to either
of the following procedures: the dehydrohalogenation of
aryl 2-haloethyl ethers6 or the addition of phenols to acet-
ylene.7 Recently, other transformations with copper (II)-
promoted coupling of arylboronic acids8 and tributyl(vi-
nyl)tin9 with phenols have also been reported. However,
most of these methods involved difficulties such as harsh
reactions, laborious manipulation and low overall yields,
or in some cases, reactions are unsuitable for sensitive
substrates, vigorous toxic compounds are used or some re-
agents are not readily available. It is well known that phe-
nylseleno group is readily converted to a leaving group
giving access to carbon-carbon double bond via oxidation
followed by b-elimination.10 However, organoselenium
reagents always have a foul smell and are quite toxic,
which is often problematic in organic synthesis. Recently,
the use of the selenium reagents immobilized on polymer-
resin has provided significant advantages, including de-
crease volatility and simplification of product work-up.11
In connection with our interest in solid-phase organosele-
nium chemistry,12 herein, we wish to report a convenient
and efficient solid-phase synthetic approach to aryl vinyl
ethers based on a novel polymer-supported b-bromoethyl
selenide (Scheme 1).
R
4a–h
5a–h
Scheme 1
perature for long time without diminution of capacity or
the liberation of disagreeable odors. With the resin 2 in
hand, the preparation of phenolic ethers resin 4, the key
for the success of this protocol was investigated. Usually
the synthesis of phenolic ethers has been efficiently ac-
complished by alkylation reaction in the presence of a
base. Here, the alkylation reaction was investigated start-
ing from resin 2 and 4-cyanophenol (3f). In our case,
when potassium carbonate and DMF were employed as a
base and a solvent, respectively, the alkylation on solid-
phase at room temperature for 24 hours was complete as
monitored by FT-IR spectra with a single strong CN peak
at 2210 cm–1 and the complete disappearance of the C-Br
Table 1 Preparation of Aryl Vinyl Ethers on a Polymeric Support
Entry
Phenol
R
Product Yield
(%)a
Purity
(%)b
1
2
3
4
5
6
7
8
3a
3b
3c
3d
3e
3f
H
5a
5b
5c
5d
5e
5f
95
94
96
93
93
95
94
92
> 95
> 95
> 95
> 95
> 95
> 95
> 95
> 95
3-CH3
4-t-C4H9
4-Br
Simple stirring of polymer-supported selenium bromide 1
in THF at room temperature with a excess of anhydrous
ethene resulted in a rapid decolorization of the resin (less
than five minutes) to produce a yellow b-bromoethyl se-
lenide resin 2 in nearly quantitative yield, as monitored by
FT-IR spectroscopy showing a moderate strong C-Br ab-
sorption at 572 cm–1. Resin 2 can be stored at room tem-
4-NO2
4-CN
3g
3h
4-CO2CH3
4-NHCOCH3
5g
5h
a Overall yield based on polymer-supported b-bromoethyl selenide
(1.14 mmol Br/g).
b Determined by 1 H NMR of crude cleavage product.
SYNTHESIS 2004, No. 17, pp 2833–2836
x
x.
x
x
.
2
0
0
4
Advanced online publication: 21.10.2004
DOI: 10.1055/s-2004-834874; Art ID: F09704SS
© Georg Thieme Verlag Stuttgart · New York

2834
S.-R. Sheng et al.
PAPER
was stirred at r.t. for 5 min. After removal of the solvent, the yellow
resin 2 containing Br (1.14 mmol) was obtained and then swelled in
DMF (8 mL). K2CO3 (0.25 g, 1.8 mmol), NBu4I (0.018 g, 0.05
mmol), KI (0.025g, 0.15 mmol) and a solution of phenols 3a–i (2.0
mmol) in DMF (2 mL) was added under a nitrogen atmosphere. The
mixture was stirred at r.t. for 10 h and then filtered, the polymer was
washed successively with HOAc (ca 2.0 equiv), H2O, THF (2 × 5
mL), MeOH (2 × 5 mL) and CH2Cl2 (2 × 5 mL). The washed resin
4 was pre-swollen with THF (15 mL), followed by the treatment
with 30% hydrogen peroxide (1.5 mL, 17.4 mmol) and stirred at r.t.
for 30 min. Then the resin was filtered off and rinsed with Et2O (4
× 3 mL). The filtrate was extracted with Et2O and the organic ex-
tracts were washed with water, dried over anhyd MgSO4 and con-
centrated to afford product 5a–i.
absorption and was found to have lost all its bromine by
elemental analysis. Furthermore, it has been found that the
alkylation was carried out completely in only about ten
hours in the presence of catalytic amounts of NBu4I/KI.
But in other solvents such as CH3CN, CH2Cl2 and THF
under the same conditions as above, or at reflux tempera-
ture even for longer time, the alkylation was not complete
according to the FT-IR spectrum of the isolated resin with
CBr and CN absorptions.
As expected, oxidation–elimination of resins 4a–h was
very rapid and efficient with excess of 30% hydrogen per-
oxide at room temperature to afford the corresponding
aryl vinyl ethers 5a–h in good yields (92–96%) and high
purity of crude materials in all cases (> 95% by 1H NMR
analysis) (Table 1). The residual resin, polystyrene-sup-
ported phenylseleninic acid, was obtained as a by-prod-
uct, whose FT-IR data was identical to the previously
reported data.13 The polystyrene-supported phenylsele-
Phenyl Vinyl Ether (5a)
Colorless oil (lit.7a oil).
IR: 3045, 1640, 1623, 1600, 1495, 1230, 1212, 1165, 1155, 1145,
956, 942 cm–1.
1H NMR: d = 7.15–7.02 (m, 5 H), 6.58 (dd, J = 14.0, 6.0 Hz, 1 H),
4.70 (dd, J =14.0, 1.5 Hz, 1 H), 4.34 (dd, J = 6.0, 1.5 Hz, 1 H).
ninic acid could be converted to resin 1 for recycle by
13C NMR: d = 154.0, 144.4, 133.1, 120.5, 115.3, 95.3.
12c,14
treatment of it with KI/Na2S2O3
followed by bro-
mine.12a For example, phenyl vinyl ether (5a) was ob-
tained in 84% yield under the same reaction condition
using the recovered selenenyl bromide resin 1 (second
run), and in 71% yield after second recycle (i.e. third run).
It was shown that recycling 2–3 times led to a gradual de-
terioration of the resin 1.
Anal. Calcd for C8H8O: C, 79.98; H, 6.71. Found: C, 80.06; H, 6.80.
3-Methylphenyl Vinyl Ether (5b)
Colorless oil (lit.7a oil).
IR: 3050, 1640, 1622, 1600, 1500, 1380, 1230, 1160, 1149, 960,
822 cm–1.
1H NMR: d = 6.83–7.20 (m, 4 H), 6.50 (dd, J = 14.2, 6.5 Hz, 1 H),
4.32 (dd, J = 14.2, 1.8 Hz, 1 H), 4.04 (dd, J = 6.5, 1.8 Hz, 1 H), 2.30
(s, 3 H).
13C NMR: d = 154.6, 140.4, 132.1, 123.7, 122.6, 119.5, 115.3, 95.6,
21.5.
Similarly, the treatment of resin 2 with 1-naphthol (3i)
gave 1-naphthyl vinyl ether (5i) in 93% yield and with
>95% purity. With our successful synthesis of aryl vinyl
ethers, we studied the reaction of resin 2 with benzyl alco-
hol in the same procedure, but no reaction was observed.
However, when sodium hydride was used instead of
K2CO3, 80% isolated yield of benzyl vinyl ether (5j) was
obtained. The yield of 5j did not improved greatly on en-
hancing the reaction temperature or prolonging the reac-
tion time.
Anal. Calcd for C9H10O: C, 80.56; H, 7.51. Found: C, 80.66; H,
7.60.
4-t-Butylphenyl Vinyl Ether (5c)
Colorless oil (lit.6a oil).
IR: 3045, 2940, 1640, 1600, 1600, 1500, 1378, 1240, 1180, 1149,
825 cm–1.
1H NMR: d = 6.80 (d, J = 8.2 Hz, 2 H), 7.18 (d, J = 8.2 Hz, 2 H),
6.51 (dd, J = 14.0, 6.2 Hz, 1 H), 4.28 (dd, J = 14.0, 1.6 Hz, 1 H),
4.24 (dd, J = 6.2, 1.6 Hz, 1 H), 1.31 (s, 9 H).
In conclusion, a convenient and efficient method for the
solid-phase traceless synthesis of aryl vinyl ethers from
alkylation of polymer-supported b-bromoethyl selenide
with phenols and subsequent oxidation–elimination has
been developed. Simple workup procedure replaces the
time-consuming isolation and purification steps in the
corresponding solution-phase synthesis.
13C NMR: d = 157.1, 145.5, 133.7, 120.0, 117.3, 95.8, 38.0, 28.5.
Anal. Calcd for C12H16O: C, 81.77; H, 9.15. Found: C, 81.86; H,
9.20.
4-Bromophenyl Vinyl Ether (5d)
Melting points are uncorrected. 1H NMR (400 MHz) spectra were
recorded on a Bruker Avance (400 MHz) spectrometer, using
CDCl3 as the solvent and TMS as internal standard. FT-IR spectra
were taken on a Perkin-Elmer SP One FT-IR spectrophotometer.
Microanalyses were performed with a PE 2400 elemental analyzer.
Polystyrene for the preparation of polystyrene-supported selenium
bromide according to the procedure described by Nicolaou11a was
purchased from Aldrich (100–200 mesh, cross-linked with 1% divi-
nylbenzene). Phenols were purchased from commercial sources or
prepared in our laboratory.
Colorless oil (lit.15 oil).
IR: 3050, 1636, 1578, 1475, 1230, 1160, 1140, 1060, 1000, 950,
820 cm–1.
1H NMR: d = 7.40 (d, J = 8.5 Hz, 2 H), 6.95 (d, J = 8.5 Hz, 2 H),
6.60 (dd, J = 13.8, 6.1 Hz, 1 H), 4.78 (dd, J = 13.8, 1.8 Hz, 1 H),
4.48 (dd, J = 6.1, 1.8 Hz, 1 H).
13C NMR: d = 155.9, 147.7, 132.6, 118.5, 115.7, 96.0.
Anal. Calcd for C8H7BrO: C, 48.27; H, 3.55. Found: C, 48.36; H,
3.63.
Preparation of Aryl Vinyl Ethers; General Procedure
To THF (10 mL) saturated with anhyd ethane was added the poly-
styrene-bound selenenyl bromide 1 (1.0 g, 1.18 mmol). The deep
red coloration of the polymer disappeared instantly and the mixture
4-Nitrophenyl Vinyl Ether (5e)
Colorless oil (lit.15 oil).
Synthesis 2004, No. 17, 2833–2836 © Thieme Stuttgart · New York

PAPER
Polymer-Supported b-Bromoethyl Selenide
2835
IR: 3060, 1638, 1600, 1580, 1498, 1481, 1330, 1230, 1160, 1120,
1100, 945, 840 cm–1.
1H NMR: d = 8.25 (d, J = 8.9 Hz, 2 H), 7.10 (d, J = 8.9 Hz, 2 H),
6.68 (dd, J = 13.6, 6.0 Hz, 1 H), 5.01 (dd, J = 13.6, 1.9 Hz, 1 H),
4.70 (dd, J = 6.0, 1.9 Hz, 1 H).
1H NMR: d = 7.20–7.12 (m, 5 H), 6.50 (dd, J = 13.9, 6.7 Hz, 1 H),
4.55 (s, 2 H), 4.22 (dd, J = 13.9, 2.0 Hz, 1 H), 3.97 (dd, J = 6.7, 2.0
Hz, 1 H).
13C NMR: d = 139.5, 131.1, 128.6, 127.5, 114.8, 95.2, 73.9.
Anal. Calcd for C9H10O: C, 80.56; H, 7.51. Found: C, 80.65; H,
7.61.
13C NMR: d = 161.3, 145.5, 142.8, 125.7, 116.3, 99.1.
Anal. Calcd for C8H7NO3: C, 58.18; H, 4.27; N, 8.48. Found: C,
58.25; H, 4.35; N, 8.52.
Acknowledgment
4-Cyanophenyl Vinyl Ether (5f)
We are grateful for the financial support from the Natural Science
Foundation of Jiangxi Province, P. R. China (No.0420017).
Colorless oil (lit.16 oil).
IR: 3050, 2200, 1635, 1595, 1492, 1300, 1235, 1160, 1125, 950,
824 cm–1.
1H NMR: d = 7.70 (d, J = 8.6 Hz, 2 H), 7.10 (d, J = 8.6 Hz, 2 H),
6.66 (dd, J = 13.7, 6.1 Hz, 1 H), 4.98 (dd, J = 13.7, 2.0 Hz, 1 H),
4.68 (dd, J = 6.1, 2.0 Hz, 1 H).
References
(1) Comprehensive Organic Synthesis, Vol. 9; Trost, B. M.;
Fleming, I., Eds.; Pergamon: Oxford, 1991, Cumulative
Indexes, see: enol ethers; ethers, phenyl vinyl; ethers, vinyl;
vinyl ethers.
13C NMR: d = 159.8, 145.8, 134.1, 118.6, 117.1, 106.1, 98.6.
(2) For selected examples of [2+2] cylcoadditons, see:
(a) Brückner, R.; Huisgen, R. Tetrahedron Lett. 1990, 31,
2557. (b) El-Nabi, H. A. A. Tetrahedron 1997, 53, 1813.
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1982, 55, 2190.
Anal. Calcd for C9H7NO: C, 74.46; H, 4.86; N, 9.65. Found: C,
74.53; H, 4.91; N, 9.70.
Methyl 4-(Vinyloxy)benzoate (5g)
Colorless oil (lit.16 oil).
(3) For selected examples of Diels–Alder reactions, see:
(a) Markó, I. E.; Evans, G. R.; Declercq, J.-P. Tetrahedron
1994, 50, 4557. (b) Wada, E.; Yasuoka, H.; Kanemasa, S.
Chem. Lett. 1994, 145. (c) Hojo, M.; Masuda, R.; Okada, E.
Synthesis 1990, 347.
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1813. (b) Shimizu, T.; Hayashi, Y.; Teramura, K. J. Org.
Chem. 1983, 48, 3053.
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1466. (b) Abu-Gnim, C.; Amer, I. J. Organomet. Chem.
1996, 516, 235. (c) Basoli, C.; Botteghi, C.; Cabras, M. A.;
Chelucci, G.; Marchetti, M. J. Organomet. Chem. 1995, 488,
C20.
(6) (a) Mizuno, K.; Kimura, Y.; Otsuji, Y. Synthesis 1979, 688.
(b) Dombroski, J. R.; Hallensleben, M. L. Synthesis 1972,
693. (c) McClelland, R. A. Can. J. Chem. 1977, 55, 548.
(d) Oae, S.; Yano, Y. Tetrahedron 1968, 24, 5721.
(e) Fueno, T.; Matsumura, I.; Okuyama, T.; Furukawa, J.
Bull. Chem. Soc. Jpn. 1968, 41, 818.
IR: 3050, 2985, 2940, 1710, 1635, 1596, 1498, 1425, 1300, 1272,
1235, 1156, 1132, 1100, 840 cm–1.
1H NMR: d = 8.00 (d, J = 8.3 Hz, 2 H), 7.15 (d, J = 8.3 Hz, 2 H),
6.88 (dd, J = 13.6, 6.0 Hz, 1 H), 4.85 (dd, J = 13.6, 1.6 Hz, 1 H),
4.55 (dd, J = 6.0, 1.6 Hz, 1 H), 3.84 (s, 3 H).
13C NMR: d = 166.5, 160.2, 146.6, 131.5, 124.5, 116.1, 97.3, 51.8.
Anal. Calcd for C10H10O3: C, 67.41; H, 5.66. Found: C, 67.50; H,
5.71.
N-[4-(Vinyloxy)phenyl]acetamide (5h)
Mp 102–103 °C (lit.17 mp 103–103.5 °C).
IR: 3258, 3188, 3130, 3055, 1650, 1600, 1495, 1300, 1235, 1210,
1162, 1145, 940, 830 cm–1.
1H NMR: d = 7.40–7.50 (m, 2 H), 7.26 (br s, 1 H), 6.95–7.05 (m, 2
H), 6.63 (dd, J = 13.7, 6.1 Hz, 1 H), 4.75 (dd, J = 13.7, 1.7 Hz, 1 H),
4.55 (dd, J = 6.1, 1.7 Hz, 1 H), 2.18 (s, 3 H).
13C NMR: d = 169.2, 153.2, 148.5, 133.4, 122.1, 117.3, 94.6, 24.1.
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Anal. Calcd for C10H11NO2: C, 67.78; H, 6.26; N, 7.90. Found: C,
67.87; H, 6.36; N, 7.96.
1-Naphthyl Vinyl Ether (5i)
Mp 31–32 °C (lit.18 mp 32 °C).
IR: 3050, 1630, 1600, 1495, 1255, 1226, 1172, 1152, 1142, 942
cm–1.
1H NMR: d = 7.00–7.50 (m, 7 H), 6.71 (dd, J = 14.1, 6.0 Hz, 1 H),
4.81 (dd, J = 14.1, 1.6 Hz, 1 H), 4.45 (dd, J = 6.0, 1.6 Hz, 1 H).
13C NMR: d = 152.7, 144.9, 133.9, 132.6, 128.9, 128.7, 128.3,
126.7, 125.9, 123.5, 115.8, 95.7.
Anal. Calcd for C12H10O: C, 84.68; H, 5.92. Found: C, 84.74; H,
6.01.
Benzyl Vinyl Ether (5j)
Colorless oil (lit.18 oil).
IR: 2986, 1642, 1596, 1500, 1425, 1302, 1235, 1150, 1100, 965
cm–1.
Synthesis 2004, No. 17, 2833–2836 © Thieme Stuttgart · New York

2836
S.-R. Sheng et al.
PAPER
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Synthesis 2004, No. 17, 2833–2836 © Thieme Stuttgart · New York