Electrochemical fluoro-selenenylation of electron-deficient olefins

Article abstract of DOI:10.1016/j.tet.2008.12.068

Electrochemical fluoro-selenenylation of electron-deficient olefins like α,β-unsaturated ester, carboxylic acid, amide, and phosphonate was successfully carried out by the anodic oxidation of diphenyl diselenide in the presence of olefins in Et₃

Full text of DOI:10.1016/j.tet.2008.12.068

Tetrahedron 65 (2009) 1559–1566
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Tetrahedron
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Electrochemical fluoro-selenenylation of electron-deficient olefins
*
Hirokatsu Nagura, Shinsuke Inagi, Toshio Fuchigami
Department of Electronic Chemistry, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8502, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Electrochemical fluoro-selenenylation of electron-deficient olefins like a,b-unsaturated ester, carboxylic
Received 1 December 2008
Received in revised form 21 December 2008
Accepted 23 December 2008
Available online 27 December 2008
acid, amide, and phosphonate was successfully carried out by the anodic oxidation of diphenyl diselenide
in the presence of olefins in Et3N$5HF/CH3NO2. The anodically generated benzeneselenenyl fluoride
[PhSeF] equivalent was stable in the electrolytic solution, which resulted in the efficient fluoro-selene-
nylation. The fluoro-selenenylation products were shown to be potential useful fluoro-building blocks.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
not suitable for large-scale synthesis. Here, we describe a new
efficient system for fluoro-selenenylation of electron-deficient
The efficient methods for preparation of organofluorine com-
pounds are receiving considerable attention because of their
unique chemical, physical, and biological properties.1 We showed
that electrochemical fluorination is more elegant and applicable
olefins like a,b-unsaturated esters and carboxylic acids by using an
electrochemical method, which can be conducted at ambient
temperature under mild and safe conditions.
than conventional methods for selective a-fluorination of hetero-
2. Result and discussion
atom compounds.2 On the other hand, fluoro-selenenylation of
olefins is one of the important methods for preparation of organo-
fluorine compounds since a fluorine atom and a selenenyl group
can be introduced into a carbon–carbon double bond at the same
time and obtainable fluorinated selenides are expected to be useful
fluorine-containing building blocks.3
2.1. Electrochemical fluoro-selenenylation of ethyl acrylate
under various conditions
First, we investigated the reaction of [PhSeF] equivalent with
ethyl acrylate (1a) as a model electron-deficient olefin under vari-
ous conditions as shown in Table 1.
Several fluoro-selenenylation systems such as PhSeNpthali-
mide-Py$HF/CH2Cl2,4 PhSeNpthalimide-Py$9HF/CH2Cl2,5 ultra-
sonication in AgF–PhSeBr/CH2Cl2,6 (PhSe)2/XeF2/CH2Cl2,7 and
(PhSe)2/p-Tol-IF2/CH2Cl2,8 which generate benzeneselenenyl fluo-
ride [PhSeF] equivalent9 in situ have been reported so far. Uneyama
et al. also developed electrochemical oxidation of (PhSe)2 in
Et3N$3HF/CH2Cl2.10 In this system, electrochemical oxidation of
diphenyl diselenide generates an electron-deficient selenium spe-
cies (PhSeþ), which is converted into [PhSeF] equivalent in the
presence of a fluoride ion without use of any oxidation reagents.
However, the electrochemical system cannot be applied to the
fluoro-selenenylation of electron-deficient olefins such as methyl
acrylate. On the other hand, the reaction of [PhSeF] equivalent with
electron-deficient olefins has been successfully demonstrated by
using the (PhSe)2/XeF2/CH2Cl2 system. In this system, however,
limited conditions like a high concentration of [PhSeF] equivalent,
low temperature (ꢀ20 ꢁC), and a nitrogen atmosphere are re-
quired.11 Moreover, XeF2 is very expensive, therefore this method is
Under the reported electrochemical conditions (Et3N$3HF/
CH2Cl2),10 the reaction did not proceed at all (Entry 1). On the
contrary, when the supporting electrolyte was changed from
Et3N$3HF to Et3N$5HF, the desired products 2a and 3a were formed
in 11% and 4%, respectively (Entry 2). This is due to the higher
nucleophilicity of fluoride ions of Et3N$5HF compared with that
of Et3N$3HF. Since the oxidation peak potentials of (PhSe)2 in
Et3N$3HF/CH2Cl2 (1/9) and Et3N$5HF/CH2Cl2 (1/9) were almost
same (1.38 V and 1.39 V vs Fcþ/Fc), the anodically generated species
would be the same [PhSeF] equivalent. The electrolysis using an
undivided cell at ambient temperature also provided the fluori-
nated products in almost same yields as Entry 2 (Entry 3). Notably,
the use of CH3NO2 as the solvent markedly promoted the reaction,
and fluorinated products 2a and 3a were obtained in 35% and 12%
yields, respectively (Entry 4). When Et3N$3HF/CH3NO2 solution was
employed, however, the desired fluoro-selenenylation did not take
place (Entry 5). In consideration to the fact that the concentration of
[PhSeF] equivalent affects the efficiency of the reaction,11 current
density was changed from 10 mA/cm2 to 20 mA/cm2 in an
Et3N$5HF/CH3NO2 solution in order to increase the concentration
of [PhSeF] equivalent (Entry 6). However, the products yields were
* Corresponding author. Tel./fax: þ81 45 924 5406.
E-mail address: fuchi@echem.titech.ac.jp (T. Fuchigami).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.12.068

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H. Nagura et al. / Tetrahedron 65 (2009) 1559–1566
Table 1
Electrochemical fluoro-selenenylation of ethyl acrylate (1a) under various conditions
F
SePh
OEt
-2e
PhSe
OEt
F
OEt
+
+
PhSeSePh
0.2 mmol
Supporting electrolyte/
Solvent
O
O
O
2a
1a
4 F/mol
3a
(6 equiv.)
Entry
Cella
Supporting electrolyte/solvent (ml)
Temp
Current density (mA/cm2)
Yieldb (%)
2a
3a
1
2
3
4
5
6
7c
D
D
Et3N$3HF/CH2Cl2 (1/9)
Et3N$5HF/CH2Cl2 (1/9)
Et3N$5HF/CH2Cl2 (1/9)
Et3N$5HF/CH3NO2 (1/9)
Et3N$3HF/CH3NO2 (1/9)
Et3N$5HF/CH3NO2 (1/9)
Et3N$5HF/CH3NO2 (2/8)
0 ꢁ
0 ꢁ
rt
rt
rt
C
C
10
10
10
10
10
20
10
0
11
12
35
0
23
73 (54)
0
4
4
12
0
7
UD
UD
UD
UD
UD
rt
rt
18 (14)
a
D: Divided cell equipped with a sintered glass filter. UD: Undivided cell.
Determined by 19F NMR. Isolated yields are shown in parentheses.
Diphenyl diselenide (0.5 mmol) was used.
b
c
decreased due to the over oxidation of the fluorinated products. On
the other hand, the concentrations of the supporting electrolyte
and diphenyl diselenide were found to affect greatly the efficiency
of the reaction. Thus, 2a and 3a were obtained in 73% and 18%
yields, respectively, by the electrolysis of 0.5 mmol of (PhSe)2 and
3 mmol of ethyl acrylate in an Et3N$5HF/CH3NO2 (2 ml/8 ml) so-
lution (Entry 7). The use of higher concentrations of (PhSe)2 and
olefin should increase the frequency factor in the addition reaction
step, therefore, the increased yield is reasonable.
Previously, it was reported that the lifetime of the [PhSeF]
equivalent would affect the efficiency of the reaction of [PhSeF]
equivalent with electron-deficient olefins.11 With this in mind, we
carried out anodic oxidation of (PhSe)2 in Et3N$5HF/CH3NO2 using
a divided cell equipped with a Nafion membrane in the absence of
ethyl acrylate. After 2 F/mol of charge was passed, the electrolysis
was stopped, and then the solution was stirred for arbitrary time
under air atmosphere at ambient temperature followed by the
addition of ethyl acrylate (1a) to the anodic compartment. The re-
sults are shown in Figure 1.
Immediately after the electrolysis of (PhSe)2, 1a was added to
the electrolytic solution, and the solution was stirred for 0.5 h. In
this case, fluorinated products 2a and 3a were obtained in 48% and
18% yields, respectively. Both products were isolated in 37% and 15%
yields. Moreover, even when the electrolysis was stopped and the
resulting electrolytic solution was stirred for 1 h at ambient tem-
perature followed by addition of 1a, a considerable amount of
fluorinated products 2a and 3a was detected. These results clearly
suggest that electrochemically generated [PhSeF] equivalent is
stable in an Et3N$5HF/CH3NO2 solution. Therefore, it is reasonable
that fluoro-selenenylation of ethyl acrylate, which is much less
reactive compared with electron-rich olefins, can be successfully
carried out since the lifetime of [PhSeF] equivalent is markedly
prolonged in this solution.
2.2. Electrochemical fluoro-selenenylation of
a,b-
unsaturated esters in Et3N$5HF/CH3NO2 solution
Next, we carried out electrochemical fluoro-selenenylation of
various -unsaturated esters like ethyl methacrylate (1b), ethyl
a,b
crotonate (1c), ethyl tiglate (1d), and ethyl 3-methylcrotonate (1e)
under the optimized conditions (Table 1, Entry 7). The results are
summarized in Table 2.
OEt
O
1a
SePh
OEt
+
PhSe
F
stirring
X min
F
-2e
OEt
Desired products were formed in good to excellent yields
(Entries 2–5). In the case of reaction with ethyl crotonate, the
product was formed as a single diastereomer. Additionally, pre-
vious reports on the addition reaction involving electrophilic
selenium reagents describe that the reaction affords specifically the
trans-addition product.4–6,8 Therefore, we assume that the reaction
of [PhSeF] equivalent with electron-deficient olefins gives the
trans-addition products. However, isolated yields were decreased
in all cases because of the instability of the products during the
separation with a silica gel column chromatography, and the cor-
responding alcohols were detected by GC–MS. Similar hydrolysis of
fluoro-selenenylation products during purification with column
chromatography was reported by Uneyama et al. They did not show
any isolated yields of fluoro-selenenylation products.11
PhSeSePh
[PhSeF]
Divided cell
(Nafion membrane)
0.5 h
O
2a
O
3a
60
50
40
30
20
10
2a
3a
Regioselectivity of the reaction was dependent on the sub-
stituent of
In the case of 1a, an electrophilic selenenyl group was mainly
introduced into the -position of the ester group since -selene-
nylation generates less stable cationic intermediate A due to the
electron-withdrawing effect of the ester group. On the other hand,
a,b-unsaturated esters as shown in Scheme 1.
0
0
50
100
X (min)
Yields were determined by 19F NMR.
150
200
a
b
an electron-donating methyl group substituent at the
b-position of
Figure 1. Relationships between yields (2a and 3a) and initiation time of the reaction
with 1a after electrolysis of (PhSe)2.
a,b-unsaturated esters should stabilize the cationic intermediate B

H. Nagura et al. / Tetrahedron 65 (2009) 1559–1566
1561
Table 2
Electrochemical fluoro-selenenylation with various a,b-unsaturated esters
R3 SePh
OEt
R3
F
R3
-2e
R1
OEt
+
F
PhSe
OEt
+
PhSeSePh
Undivided cell
R1 R2
R1 R2
.
R2
O
O
O
Et3N 5HF/CH3NO2 (2/8)
Pt-Pt, rt
3
10 mA/cm2
2
1
Entry
Olefin
R1
R2
R3
Charge passed (F/mol)
Yielda (%)
2
3
1
2
3
4
5
1a
1b
1c
1d
1e
H
H
Me
Me
Me
H
H
H
H
H
Me
H
Me
H
4
6
4.5
8
6
2a
2b
2c
2d
2e
73 (54)
26 (9)
99 (71)
56 (26)
90 (58)
3a
3b
3c
3d
3e
18 (14)
73 (54)
0
12 (5)
0
Me
a
Determined by 19F NMR. Isolated yields are shown in parentheses.
-e
F-
[PhSeF]
1/2 PhSeSePh
SePh
O
SePh
OEt
F-
F-
OEt
F
PhSe
OEt
OEt
O
(more stable)
2a 73%
O
1a
O
F
PhSe
OEt
PhSe
OEt
O
O
A
3a 18%
SePh
SePh
F-
PhSe
OEt
[PhSeF]
OEt
OEt
OEt
F
O
O
O
O
2c 99%
B
1c
OEt
SePhO
SePh
SePh
[PhSeF]
F-
F-
F
OEt
OEt
PhSe
OEt
OEt
O
O
1b
O
O
2b 26%
F
PhSe
OEt
PhSe
OEt
O
O
(more stable)
3b 73%
Scheme 1.
generated by
result in exclusive selenenylation at the
group. It is reasonable that the substitution of
ters with an -methyl group enhanced -selenenylation due to its
electron-donating and steric effects.
a
-selenenylation. Such stabilization effect seems to
-position to the carbonyl
-unsaturated es-
In the cases of methacrylic acid (4a), crotonic acid (4b), and
methacrylic amide (4c), the reactions proceeded smoothly to pro-
vide the corresponding fluorinated products in moderate yields
(Entries 1–3). On the contrary, the reaction with methyl vinyl
a
a,b
a
b
We also conducted the reaction of [PhSeF] equivalent with
various kinds of crotonic acid esters (1f–h) in an Et3N$5HF/CH3NO2
(2 ml/8 ml) solution. The results are summarized in Table 3.
As shown in Table 3, even bulky groups like isopropyl ester
group (1g) or p-methoxybenzyl ester group (1h) did not interfere
with fluoro-selenenylation, and the desired products 2g and 2h
were formed in excellent yields.
Table 3
Electrochemical fluoro-selenenylation with various crotonates
SePh
OR
-2e
OR
+
PhSeSePh
Undivided cell
.
F
O
Et3N 5HF/CH3NO2 (2/8)
Pt-Pt, rt
O
2
1
10 mA/cm2
2.3. Electrochemical fluoro-selenenylation of olefins having
various electron-withdrawing group in Et3N$5HF/CH3NO2
solution
Entry
Olefin
R
Charge passed (F/mol)
Yielda (%)
1
2
3
4
1f
Me
Et
i-Pr
4
4.5
4
2f
96 (64)
1c
1g
1h
2c
2g
2h
99 (71)
92 (70)
99 (59)
4-MeOC6H4CH2
5
The electrochemical fluoro-selenenylation was also extended to
a
various
a
,b
-unsaturated carbonyl compounds as shown in Table 4.
Determined by 19F NMR. Isolated yields are shown in parentheses.

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H. Nagura et al. / Tetrahedron 65 (2009) 1559–1566
Table 4
Electrochemical fluoro-selenenylation with various
a
,
b
-unsaturated carbonyl compounds
R2
R2 SePh
-2e
R2
F
R1
+
Y
PhSeSePh
F
Y
PhSe
Y
+
Undivided cell
Et3N 5HF/CH3NO2 (2/8)
Pt-Pt, rt
R1
O
R1
O
.
O
4
5
6
10 mA/cm2
Entry
Olefin
R1
R2
Y
Charge passed (F/mol)
Yielda (%)
5
6
1
2
3
4
5
4a
4b
4c
4d
4e
H
Me
H
H
H
Me
H
Me
H
OH
OH
NH2
Me
H
4.5
5
4
6
8
5a
5b
5c
5d
5e
Trace
6a
6b
6c
6d
6e
71 (36)
0
50 (45)
11 (9)
8 (5)
59 (20)
15 (11)
21 (14)
8 (3)
Me
a
Determined by 19F NMR. Isolated yields are shown in parentheses.
ketone (4d) and methacrolein (4e) became complicated and the
fluorinated products were obtained in low yields (Entries 4 and 5).
The fluoro-selenenylation was also successfully extended to acryl
and crotyl amides having a chiral oxazolidinone moiety (4f and 4g)
and the corresponding fluorinated products were obtained in good
to moderate yields as a diastereoisomeric mixture (Scheme 2).
Furthermore, the reactions of olefins having diethyl phospho-
nate (7a), methylsulfonyl (7b), and cyano (7c) groups were also
carried out as shown in Table 5.
In the case of 7a, fluorinated product 8a was formed in moderate
yield (Entry 1). On the other hand, the reaction of 7b provided
desired product 8b in low yield and a considerable amount of
starting material was recovered (Entry 2). The stronger electron-
withdrawing methylsulfonyl group compared with ester group
seems to interfere with the reaction. Moreover, in the case of 7c,
which has much stronger electron-withdrawing cyano group, the
reaction did not proceed at all (Entry 3). In this case, the starting
material was mostly recovered.
Table 5
Electrochemical fluoro-selenenylation with olefins having various electron-with-
drawing groups
R
R
SePh
EWG
-2e
+
PhSeSePh
F
EWG
Undivided cell
.
Et3N 5HF/CH3NO2 (2/8)
Pt-Pt, rt
7
8
10 mA/cm2
Entry
Olefin
R
EWG
Charge passed (F/mol)
Yielda of 8 (%)
1
2
3
7a
7b
7c
H
H
Me
P(O)(OEt)2
SO2Me
CN
6
8
8
8a
8b
8c
59 (40)
19 (19)
0
a
Determined by 19F NMR. Isolated yields are shown in parentheses.
F
O
F
O
O
O
H2O2
N
N
O
O
2.4. Transformation of fluoro-selenenylation products
CH2Cl2
rt, 7 h
SePh
A selenium group of the fluoro-selenenylation products is
expected to have versatile functionalities. Therefore, we tried to
transform the fluorinated selenides. First, we carried out desele-
nenylation of 5g as a model compound with hydrogen peroxide.
Ph
5g
Ph
9
18% (Isolated yield)
Scheme 3.
Deselenenylation proceeded, however, desired olefin
9 was
obtained in low yield (Scheme 3). It was determined that com-
pound 9 is Z-form on the basis of the coupling constant of olefinic
fluorine and proton (ca. 32 Hz). Product 9 is expected to be a good
chiral fluorinated Michael acceptor. This is in sharp contrast to the
yield (85%). On the other hand, the reaction of regioisomer 3a did
not proceed at all and 55% of starting material 3a was recovered.
This seems to be due to the instability of the radical intermediate
generated by deselenenylation of 3.
We also conducted the photochemical deselenenylation of 2a
followed by addition reaction onto olefins. The reaction with
1-octen and n-butyl vinyl ether provided the desired products in
reasonable yields as shown in Scheme 5.
highly effective deselenenylation of
a-phenylselenenyl-a-fluo-
roester derivatives reported previously.12
Next, we conducted radical initiated deselenenylation followed
by allylation of selenides 2a and 3a (Scheme 4). The reaction of 2a
proceeded smoothly and desired product 10 was formed in good
O
O
F
O
O
SePhO
F
O
-2e
R
N
R
N
O
Undivided cell
R
N
O
O
+
.
SePh
Et3N 5HF/CH3NO2 (2/8)
Pt-Pt, rt
Ph
Ph
5f 57(36)%
4 F/mol, 10 mA/cm2
Ph
6f Trace
4f R = H
(diastereomeric mixture ca. 1.5:1 determined by 19F NMR)
4g R = Me
5g 90(56)%
6g 0%
(diastereomeric mixture ca. 1.3:1 determined by 19F NMR)
Scheme 2.

H. Nagura et al. / Tetrahedron 65 (2009) 1559–1566
1563
SePh
AIBN(0.5 equiv.)
n-Bu3Sn
+
F
OEt
F
OEt
Benzene
(2 equiv.)
O
reflux, 2 h
O
10
2a
84(75)a %
a Isolated yield
F
F
AIBN(0.5 equiv.)
3a
n-Bu3Sn
OEt
+
OEt
+
PhSe
Benzene
55%
O
(2 equiv.)
O
reflux, 2 h
3a
Not obtained
Scheme 4.
4.2. General procedure for electrochemical fluoro-
selenenylation
F
SePh
h
( >200 nm)
O
O
+
Y
F
OEt
Y
CH2Cl2, rt
60~75 min
(PhSe)2 (0.5 mmol) and olefins (3 mmol) are dissolved in
Et3N$5HF/CH3NO2 (2 ml/8 ml). Constant current (40 mA) electro-
lysis of the solution was carried out in an undivided cell equipped
with two Pt electrodes (2ꢂ2 cm2) under an air atmosphere at
ambient temperature. Other conditions are shown in tables. After
(PhSe)2 was mostly consumed (monitored by silica gel TLC), the
electrolysis solution was passed through a short column of silica gel
(CHCl3 or ethyl acetate). The solvent was then removed by evapo-
ration and the residue was purified by column chromatography on
silica gel (hexane/ethyl acetate¼10/1–9/1) or by HPLC (Develosil
ODS-5, MeCN as eluent) to provide the desired fluorinated prod-
ucts. The yields were calculated based on the theoretical amount of
[PhSeF] equivalent.
O
(20 equiv)
11: Y = n-BuO- (20 %)a
2a
12: Y = n-Hex- (16 %)a
a Isolated yields.
Scheme 5.
3. Conclusion
We successfully carried out fluoro-selenenylation of electron-
deficient olefins like -unsaturated carbonyl compounds, phos-
a,b
phonate, and sulfonyl compound by using electrochemical
oxidation of (PhSe)2 in Et3N$5HF/CH3NO2. It was demonstrated
that the Et3N$5HF/CH3NO2 solvent system made the lifetime of
electrochemically generated [PhSeF] equivalent longer, and con-
sequently this effect resulted in highly effective fluoro-seleneny-
lation of electron-deficient olefins. In sharp contrast to the
previous chemical fluoro-selenenylation using expensive XeF2
under limited conditions like a nitrogen atmosphere and low
temperature (ꢀ20 ꢁC), this electrochemical method can be readily
conducted under an air atmosphere at ambient temperature
without any expensive reagents. In addition, we demonstrated the
potentiality of the carbon–carbon bond formation of the fluori-
nated products utilizing their selenenyl groups as the leaving
group.
4.3. Ethyl 3-fluoro-2-(phenylselenyl)propionate (2a)
1H NMR (270 MHz, CDCl3):
d
¼7.63–7.59 (m, 2H), 7.38–7.29 (m,
3H), 4.86–4.49 (m, 2H), 4.17 (q, J¼7.3 Hz, 2H), 3.85 (m, 1H), 1.24 (t,
J¼7.3 Hz, 3H). 13C NMR (68 MHz, CDCl3):
¼170.00 (d, J¼2.8 Hz),
d
135.87, 129.20, 129.09, 126.00, 81.95 (d, J¼177.7 Hz), 61.58, 41.61 (d,
J¼19.6 Hz),14.01. 19F NMR (254 MHz, CDCl3):
¼ꢀ127.85 (td, J¼48.1,
d
11.0 Hz). HRMS (EI): m/z [Mþ] calcd for C11H13FO2Se: 276.0065;
Found: 276.0063.
4.4. Ethyl 2-fluoro-3-(phenylselenyl)propionate (3a)
4. Experimental
1H NMR (270 MHz, CDCl3):
d
¼7.60–7.55 (m, 2H), 7.31–7.27 (m,
3H), 5.07 (ddd, J¼48.1, 6.6, 4.8 Hz, 1H), 4.25–4.12 (m, 2H), 3.44–3.19
4.1. General procedure
(m, 2H), 1.26 (t, J¼7.3 Hz, 3H). 13C NMR (68 MHz, CDCl3):
¼168.10
d
(d, J¼24.0 Hz), 133.61, 129.12, 128.60, 127.68, 87.96 (d, J¼186.7 Hz),
1H, 13C, and 19F NMR spectra were recorded at 270, 68, and
254 MHz, respectively, on a JEOL-NM-EX 270 with tetramethylsi-
lane (0.00 ppm) as internal standard. The chemical shifts for 19F are
61.89, 28.79 (d, J¼22.4 Hz), 14.16. 19F NMR (254 MHz, CDCl3):
d
¼ꢀ107.96 (dt, J¼48.1, 22.2 Hz). HRMS (EI): m/z [Mþ] calcd for
C11H13FO2Se: 276.0065; Found: 276.0068.
given in
d ppm downfield from internal trifluoroacetic acid. The
following abbreviations are used: s, singlet; d, doublet; t, triplet; q,
quartet and m, multiplet. High-resolution mass spectra (HRMS)
were taken on a JEOL MStation JMS-700 mass spectrometer. Pre-
parative photoreactions were carried out using a low-pressure
mercury-vapor lamp UVL6DH-12 (SEN LIGHTS CORP. products).
Cyclic voltammetry measurement was carried out with 5 mM of
(PhSe)2 and 5 mM of ferrocene (Fc) as a reference in Et3N$3HF or
Et3N$5HF (1 ml)/CH2Cl2 (9 ml) at a Pt plate electrode (0.5ꢂ0.5 cm2)
using a Hokutodenko HA-501 Potentiostat/Galvanostat. Sweep rate
was 100 mV/s and Ag wire was used as a pseudo-reference elec-
trode. The oxidation peak potential of (PhSe)2 was shown versus
Fcþ/Fc.
4.5. Ethyl 3-fluoro-2-methyl-2-(phenylselenyl)-
propionate (2b)
1H NMR (270 MHz, CDCl3):
d
¼7.61–7.58 (m, 2H), 7.45–7.29 (m,
3H), 4.75 (dd, J¼47.6, 9.1 Hz, 1H), 4.46 (dd, J¼47.6, 9.1 Hz, 1H), 4.14–
3.98 (m, 2H), 1.58 (s, 3H), 1.16 (t, J¼7.1 Hz, 3H). 13C NMR (68 MHz,
CDCl3):
d
¼171.31 (d, J¼2.8 Hz), 138.04, 129.67, 128.88, 125.37, 86.20
(d, J¼180.5 Hz), 61.44, 47.91 (d, J¼17.3 Hz), 19.77 (d, J¼3.4 Hz),
13.96. 19F NMR (254 MHz, CDCl3):
d¼ꢀ132.60 (t, J¼47.6 Hz). HRMS
(FAB): m/z [Mþ] calcd for C12H15FO2Se: 290.0221; Found:
290.0228.

1564
H. Nagura et al. / Tetrahedron 65 (2009) 1559–1566
4.6. Ethyl 2-fluoro-2-methyl-3-(phenylselenyl)-
propionate (3b)
4.12. Isopropyl 3-fluoro-2-(phenylselenyl)butanoate (2g)
1H NMR (270 MHz, CDCl3):
d
¼7.63–760 (m, 2H), 7.35–7.27 (m,
1H NMR (270 MHz, CDCl3):
d
¼7.58–7.55 (m, 2H), 7.32–7.24 (m,
3H), 5.11–4.84 (m, 2H), 3.61 (dd, J¼9.6, 8.6 Hz, 1H), 1.56 (dd, J¼23.9,
3H), 4.22–4.07 (m, 2H), 3.46–3.31 (m, 2H), 1.66 (d, J¼20.9 Hz, 3H),
6.3 Hz, 3H), 1.22 (d, J¼6.3 Hz, 3H), 1.19 (d, J¼6.3 Hz, 3H). 13C NMR
1.24 (t, J¼7.3 Hz, 3H). 13C NMR (68 MHz, CDCl3):
d¼170.34 (d,
(68 MHz, CDCl3):
d
¼169.87 (d, J¼3.4 Hz), 135.33, 129.16, 128.72,
J¼25.2 Hz), 138.01, 133.32, 128.94, 127.35, 94.51 (d, J¼185.6 Hz),
127.07, 90.00 (d, J¼172.2 Hz), 68.93, 48.91 (d, J¼21.2 Hz), 21.74,
61.86, 35.37 (d, J¼25.2 Hz), 23.87 (d, J¼24.6 Hz), 14.12. 19F NMR
21.63, 19.10 (d, J¼22.4 Hz). 19F NMR (254 MHz, CDCl3):
¼ꢀ87.89 to
d
(254 MHz, CDCl3):
d
¼ꢀ73.65 to ꢀ74.05 (m). HRMS (FAB): m/z [Mþ]
ꢀ88.39 (m). HRMS (FAB): m/z [Mþ] calcd for C13H17FO2Se:
calcd for C12H15FO2Se: 290.0221; Found: 290.0220.
304.0378; Found: 304.0379.
4.7. Ethyl 3-fluoro-2-(phenylselenyl)butanoate (2c)
4.13. p-Methoxybenzyl 3-fluoro-2-(phenylselenyl)-
butanoate (2h)
1H NMR (270 MHz, CDCl3):
d
¼7.63–7.60 (m, 2H), 7.39–7.28 (m,
3H), 5.12–4.85 (m, 1H), 4.12 (q, J¼7.1 Hz, 2H), 3.65 (dd, J¼9.7, 8.4 Hz,
1H NMR (270 MHz, CDCl3):
d
¼7.55–7.51 (m, 2H), 7.34–7.22 (m,
1H), 1.56 (dd, J¼30.1, 6.1 Hz, 3H), 1.20 (t, J¼7.1 Hz, 3H). 13C NMR
5H), 6.89–6.86 (m, 2H), 5.12–4.84 (m, 1H), 5.04 (s, 2H), 3.81 (s, 3H),
(68 MHz, CDCl3):
d
¼170.26 (d, J¼3.4 Hz), 135.50, 129.16, 128.83,
3.67 (dd, J¼9.6, 8.4 Hz, 1H), 1.56 (dd, J¼23.9, 6.3 Hz, 3H). 13C NMR
126.84, 89.91 (d, J¼172.1 Hz), 61.32, 48.51 (d, J¼21.2 Hz), 19.07 (d,
(68 MHz, CDCl3):
d
¼170.14 (d, J¼3.4 Hz), 159.47, 135.56, 129.94,
J¼22.4 Hz), 14.03. 19F NMR (254 MHz, CDCl3):
¼ꢀ87.65 to ꢀ88.15
d
129.90, 129.14, 128.83, 127.43, 113.78, 89.81 (d, J¼172.7 Hz), 66.84,
(m). HRMS (FAB): m/z [Mþ] calcd for C12H15FO2Se: 290.0221;
55.29, 48.45 (d, J¼21.2 Hz), 19.04 (d, J¼21.2 Hz). 19F NMR (254 MHz,
Found: 290.0220.
CDCl3):
d
¼ꢀ87.72 to 88.22 (m). HRMS (EI): m/z [M þ] calcd for
C18H19FO3Se: 382.0483; Found: 383.0473.
4.8. Ethyl 3-fluoro-2-methyl-2-(phenylselenyl)butanoate (2d)
1H NMR (270 MHz, CDCl3):
d
¼7.60–7.56 (m, 2H), 7.44–7.29 (m,
4.14. 2-Fluoro-2-methyl-3-(phenylselenyl)propionic acid (6a)
3H), 5.19 (dq, J¼46.0, 6.3 Hz,1H), 4.10–3.95 (m, 2H), 1.57 (dd, J¼24.1,
6.3 Hz, 3H), 1.51 (s, 3H), 1.13 (t, J¼7.1 Hz, 3H). 13C NMR (68 MHz,
1H NMR (270 MHz, CDCl3):
d
¼9.02 (br s, 1H), 7.64–7.55 (m, 2H),
7.39–7.24 (m, 3H), 3.47–3.32 (m, 2H), 1.71 (d, J¼20.8 Hz, 3H). 13C
CDCl3):
d
¼171.66 (d, J¼2.2 Hz), 137.84, 129.55, 128.80, 125.86, 91.77
(d, J¼174.9 Hz), 61.28, 51.99 (d, J¼19.6 Hz), 16.15 (d, J¼2.2 Hz), 15.80
NMR (68 MHz, CDCl3):
d
¼175.74 (d, J¼26.3 Hz), 137.93, 133.56,
(d, J¼23.5 Hz), 13.92. 19F NMR (254 MHz, CDCl3):
¼ꢀ94.92 (dq,
d
129.33, 129.05, 94.43 (d, J¼186.7 Hz), 34.96 (d, J¼24.6 Hz), 23.80 (d,
J¼46.0, 24.1 Hz). HRMS (FAB): m/z [Mþ] calcd for C13H17FO2Se:
J¼24.0 Hz). 19F NMR (254 MHz, CDCl3):
¼ꢀ74.45 to ꢀ74.87 (m).
d
HRMS (FAB): m/z [MþNaþ] calcd for C10H11FO2NaSe: 284.9800;
304.0378; Found: 304.0376.
Found: 284.9808.
4.9. Ethyl 2-fluoro-2-methyl-3-(phenylselenyl)butanoate (3d)
1H NMR (270 MHz, CDCl3):
d
¼7.62–7.58 (m, 2H), 7.30–7.27 (m,
4.15. 3-Fluoro-2-(phenylselenyl)butanoic acid (5b)
3H), 4.20 (qd, J¼7.1, 1.6 Hz, 2H), 3.57 (dq, J¼24.7, 7.3 Hz, 1H), 1.72 (d,
1H NMR (270 MHz, CDCl3):
d
¼9.64 (br s, 1H), 7.65–7.62 (m, 2H),
J¼21.4 Hz, 3H), 1.50 (d, J¼7.3 Hz, 3H), 1.28 (t, J¼7.1 Hz, 3H). 13C NMR
7.40–7.28 (m, 3H), 5.09–4.81 (m, 1H), 3.62 (dd, J¼9.4, 8.4 Hz, 1H),
(68 MHz, CDCl3):
d
¼170.39 (d, J¼25.2 Hz), 134.99, 128.97, 128.60,
1.60 (dd, J¼23.9, 6.3 Hz, 3H). 13C NMR (68 MHz, CDCl3):
¼175.60
d
127.85, 97.14 (d, J¼187.8 Hz), 61.83, 45.43 (d, J¼23.5 Hz), 22.7 (d,
J¼23.5 Hz), 18.02 (d, J¼3.4 Hz), 14.20. 19F NMR (254 MHz, CDCl3):
(d, J¼2.8 Hz), 135.53, 129.35, 129.13, 126.60, 89.65 (d, J¼172.2 Hz),
48.07 (d, J¼19.6 Hz), 18.98 (d, J¼22.9 Hz). 19F NMR (254 MHz,
d
¼ꢀ79.20 to ꢀ79.55 (m). HRMS (FAB): m/z [Mþ] calcd for
CDCl3):
d
¼ꢀ87.89 to ꢀ88.39 (m). HRMS (EI): m/z [Mþ] calcd for
C13H17FO2Se: 304.0378; Found: 304.0379.
C10H11FO2Se: 261.9908; Found: 261.9909.
4.10. Ethyl 3-fluoro-3-methyl-2-(phenylselenyl)
butanoate (2e)
4.16. 3-Fluoro-2-methyl-2-(phenylselenyl)propionamide (5c)
1H NMR (270 MHz, CDCl3):
d
¼7.65–7.62 (m, 2H), 7.33–7.26 (m,
1H NMR (270 MHz, CDCl3):
d
¼7.66–7.62 (m, 2H), 7.45–7.33 (m,
3H), 4.12 (q, J¼7.3 Hz, 2H), 3.84 (d, J¼10.4 Hz,1H),1.62 (d, J¼22.1 Hz,
3H), 6.13 (br s, 1H), 5.64 (br s, 1H), 4.68 (dd, J¼47.8, 9.6 Hz, 1H), 4.49
3H), 1.61 (d, J¼21.1 Hz, 3H), 1.20 (t, J¼7.3 Hz, 3H). 13C NMR (68 MHz,
(dd, J¼47.8, 9.7 Hz, 1H), 1.56 (s, 3H). 13C NMR (68 MHz, CDCl3):
CDCl3):
d
¼170.46 (d, J¼8.4 Hz), 134.72, 129.10, 128.32, 126.79, 95.35
d
¼173.65,137.60,129.62,129.12,127.24, 86.34 (d, J¼178.3 Hz), 49.75
(d, J¼172.7 Hz), 61.19, 54.53 (d, J¼25.7 Hz), 25.86 (d, J¼23.5 Hz),
(d, J¼16.8 Hz), 20.81 (d, J¼3.9 Hz). 19F NMR (254 MHz, CDCl3):
25.06 (d, J¼24.0 Hz),14.03. 19F NMR (254 MHz, CDCl3):
¼ꢀ56.00 to
d
d
¼ꢀ133.00 (t, J¼47.8 Hz). HRMS (FAB): m/z [MþNaþ] calcd for
ꢀ56.55 (m). HRMS (FAB): m/z [Mþ] calcd for C13H17FO2Se:
C10H12FNONaSe: 283.9966; Found: 283.9973.
304.0378; Found: 304.0373.
4.11. Methyl 3-fluoro-2-(phenylselenyl)butanoate (2f)
4.17. 2-Fluoro-3-methyl-2-(phenylselenyl)propionamide (6c)
1H NMR (270 MHz, CDCl3):
d
¼7.62–7.59 (m, 2H), 7.37–7.27 (m,
1H NMR (270 MHz, CDCl3):
d
¼7.57–7.52 (m, 2H), 7.27–7.23 (m,
3H), 4.98 (ddq, J¼47.2, 9.6, 6.1 Hz, 1H), 3.70–3.63 (m, 1H), 3.66 (s,
3H), 6.40 (br s, 1H), 6.29 (br s, 1H), 3.52–3.26 (m, 2H), 1.67 (dd,
3H), 1.56 (dd, J¼24.1, 6.1 Hz, 3H). 13C NMR (68 MHz, CDCl3):
J¼21.8, 1.3 Hz, 3H). 13C NMR (68 MHz, CDCl3):
d
¼174.18 (d,
d
¼170.66 (d, J¼3.4 Hz), 135.53, 129.17, 128.91, 126.77, 89.87 (d,
J¼22.4 Hz), 137.59, 132.85, 128.92, 127.15, 97.21 (d, J¼186.1 Hz),
J¼172.2 Hz), 52.33, 48.31 (d, J¼21.2 Hz), 19.03 (d, J¼22.4 Hz). 19F
35.05 (d, J¼24.0 Hz), 23.93 (d, J¼24.0 Hz). 19F NMR (254 MHz,
NMR (254 MHz, CDCl3):
d
¼ꢀ87.48 to ꢀ87.99 (m). HRMS (FAB): m/z
CDCl3):
d
¼ꢀ73.03 to ꢀ73.60 (m). HRMS (FAB): m/z [MþNaþ] calcd
[Mþ] calcd for C11H13FO2Se: 276.0065; Found: 276.0065.
for C10H12FNONaSe: 283.9966; Found: 283.9966.

H. Nagura et al. / Tetrahedron 65 (2009) 1559–1566
1565
4.18. 4-Fluoro-3-(phenylselenyl)butan-2-one (5d)
1H NMR (270 MHz, CDCl3):
4.29–4.14 (m, 2H), 3.29 (dd, J¼13.4, 3.5 Hz, 1H), 2.75 (dd, J¼13.4,
9.7 Hz, 1H), 1.60 (dd, J¼24.4, 5.8 Hz, 3H). 13C NMR (68 MHz, CDCl3):
d
¼7.56–7.53 (m, 2H), 7.42–7.28 (m,
d
¼169.28 (d, J¼1.7 Hz), 152.93, 135.93, 135.01, 129.40, 129.23,
3H), 4.89–4.48 (m, 2H), 3.97–3.88 (m, 1H), 2.40 (s, 3H). 13C NMR
129.13, 128.92, 127.31, 125.57, 90.17 (d, J¼171.6 Hz), 66.08, 55.29,
(68 MHz, CDCl3):
d
¼201.42 (d, J¼1.7 Hz), 135.89, 129.34, 129.30,
44.25 (d, J¼20.1 Hz), 37.54, 18.90 (d, J¼22.4 Hz). 19F NMR (254 MHz,
125.36, 81.14 (d, J¼161.5 Hz), 48.67 (d, J¼19.6 Hz), 28.59. 19F NMR
CDCl3):
d
¼ꢀ87.65 to ꢀ88.15 (m). HRMS (FAB): m/z [MþHþ] calcd for
(254 MHz, CDCl3):
d
¼ꢀ130.51 (td, J¼46.2, 9.1 Hz). HRMS (FAB): m/z
C20H21FNO3Se: 422.0671; Found: 422.0663.
[MþNaþ] calcd for C10H11FONaSe: 268.9857; Found: 268.9858.
Diastereomer b (miner): 1H NMR (270 MHz, CDCl3):
d
¼7.63–
7.60 (m, 2H), 7.40–7.16 (m, 8H), 5.33–5.03 (m, 2H), 4.60–4.52 (m,
1H), 4.16–4.03 (m, 2H), 3.20 (dd, J¼13.5, 3.3 Hz, 1H), 2.84 (dd,
J¼13.5, 8.9 Hz, 1H), 1.59 (dd, J¼24.1, 6.1 Hz, 3H). 13C NMR (68 MHz,
4.19. 3-Fluoro-4-(phenylselenyl)butan-2-one (6d)
1H NMR (270 MHz, CDCl3):
d
¼7.57–7.49 (m, 2H), 7.33–7.26 (m,
CDCl3):
d
¼169.34 (d, J¼2.2 Hz), 152.75, 136.11, 136.04, 134.75,
3H), 4.94 (ddd, J¼49.1, 6.8, 4.0 Hz, 1H), 3.41–3.11 (m, 2H), 2.31 (d,
129.40, 129.16, 128.80, 127.24, 125.55, 90.09 (d, J¼171.6 Hz), 65.91,
J¼4.8 Hz, 3H). 13C NMR (68 MHz, CDCl3):
¼206.64 (d, J¼26.3 Hz),
d
55.32, 44.35 (d, J¼20.1 Hz), 37.73, 18.95 (d, J¼22.4 Hz). 19F NMR
133.33, 129.32, 128.42, 127.60, 94.23 (d, J¼186.1 Hz), 28.28 (d,
(254 MHz, CDCl3):
d
¼ꢀ86.65 to ꢀ87.14 (m). HRMS (FAB): m/z
J¼22.4 Hz), 26.71. 19F NMR (254 MHz, CDCl3):
d
¼ꢀ107.36 to
[MþNaþ] calcd for C20H20FNO3NaSe: 444.0490; Found: 444.0498.
ꢀ107.76 (m). HRMS (FAB): m/z [MþNaþ] calcd for C10H11FONaSe:
268.9857; Found: 268.9855.
4.24. Diethyl [2-fluoro-1-(phenylselenyl)ethyl]-
phosphonate (8a)
4.20. 3-Fluoro-2-methyl-2-(phenylselenyl)propion-
aldehyde (5e)
1H NMR (270 MHz, CDCl3):
3H), 4.96–4.57 (m, 2H), 4.28–4.12 (m, 4H), 3.46–3.28 (m, 1H), 1.38–
1.31 (m, 6H). 13C NMR (68 MHz, CDCl3):
d
¼7.71–7.66 (m, 2H), 7.37–7.28 (m,
1H NMR (270 MHz, CDCl3):
(m, 5H), 4.62 (dd, J¼47.4, 9.6 Hz, 1H), 4.53 (dd, J¼47.4, 9.6 Hz, 1H),
1.52 (s, 3H). 13C NMR (68 MHz, CDCl3):
d¼9.32 (d, J¼1.6 Hz, 1H), 7.53–7.29
d
¼134.91, 129.23, 128.53,
127.93, 81.81 (d, J¼177.7 Hz), 63.19 (dd, J¼29.1, 6.7 Hz), 38.28 (dd,
d
¼191.77 (d, J¼2.2 Hz),
J¼145.9, 19.6 Hz), 16.51 (dd, J¼6.1, 3.4 Hz). 19F NMR (254 MHz,
138.02, 130.00, 129.30, 123.49, 83.46 (d, J¼177.7 Hz), 54.57 (d,
CDCl3):
d
¼ꢀ132.63 to ꢀ133.15 (m). HRMS (FAB): m/z [MþNaþ]
J¼17.8 Hz), 16.06 (d, J¼3.4 Hz). 19F NMR (254 MHz, CDCl3):
calcd for C12H18FO3PNaSe: 363.0041; Found: 363.0042.
d
¼ꢀ141.05 (t, J¼47.4 Hz). HRMS (FAB): m/z [MþNaþ] calcd for
C10H11FONaSe: 268.9857; Found: 268.9857.
4.25. 2-Fluoro-1-(phenylselenyl)ethyl methyl sulfone (8b)
4.21. 2-Fluoro-2-methyl-3-(phenylselenyl)propion-
aldehyde (6e)
1H NMR (270 MHz, CDCl3):
3H), 5.24–4.73 (m, 2H), 4.30–4.18 (m, 1H), 3.11 (s, 3H). 13C NMR
d
¼7.77–7.75 (m, 2H), 7.40–7.31 (m,
(68 MHz, CDCl3):
d
¼135.64, 129.48, 129.47, 125.88, 81.69 (d,
1H NMR (270 MHz, CDCl3):
(m, 2H), 7.3–7.25 (m, 3H), 3.30–3.21 (m, 2H), 1.51 (d, J¼21.4 Hz, 3H).
13C NMR (68 MHz, CDCl3):
¼200.39 (d, J¼39.7 Hz), 133.30, 129.51,
d
¼9.74 (d, J¼4.5 Hz, 1H), 7.58–7.53
J¼177.2 Hz), 63.80 (d, J¼19.0 Hz), 40.81 (d, J¼6.1 Hz). 19F NMR
(254 MHz, CDCl3):
d
¼ꢀ133.62 (td, J¼48.0, 23.1 Hz). HRMS (FAB): m/z
d
[MþNaþ] calcd for C9H11FO2SNaSe: 304.9527; Found: 304.9525.
129.15, 127.6, 98.11 (d, J¼178.3 Hz), 33.18 (d, J¼24.0 Hz), 21.29 (d,
J¼23.5 Hz). 19F NMR (254 MHz, CDCl3):
d¼ꢀ79.66 to ꢀ80.11 (m).
4.26. 4-Benzyl-3-(3-fluoro-2-butenoyl)-oxazolidin-2-one (9)
4.22. 4-Benzyl-3-[3-fluoro-2-(phenylselenyl)propanoyl]-
oxazolidin-2-one (5f)
Hydrogen peroxide (35%, ca. 1.2 equiv) was added to a solution
of 5g (87 mg, diastereomixture) in CH2Cl2 (3 ml) at ambient tem-
perature. The solution was stirred for 7 h, treated with 1 M aq
Na2S2O3, and extracted with two portions of CH2Cl2. The combined
extracts were washed with brine and dried over anhydrous sodium
sulfate. After the removal of the solvent by evaporation, the residue
was purified by column chromatography on silica gel (hexane/
AcOEt¼4/1) to provide a pure 9 (10 mg, yield: 18%).
Diastereomer a (major): 1H NMR (270 MHz, CDCl3):
d
¼7.66–7.62
(m, 2H), 7.42–7.25 (m, 8H), 5.25 (td, J¼10.1, 5.1 Hz, 1H), 4.94–4.51
(m, 3H), 4.26–4.16 (m, 2H), 3.33 (dd, J¼13.4, 3.5 Hz, 1H), 2.81 (dd,
J¼13.4, 9.7 Hz, 1H). 13C NMR (68 MHz, CDCl3):
d
¼168.94 (d,
J¼1.7 Hz), 152.82, 136.63, 134.93, 129.44, 129.38, 129.20, 128.93,
127.33, 124.60, 81.58 (d, J¼177.2 Hz), 66.19, 55.27, 38.12 (d,
1H NMR (270 MHz, CDCl3):
d¼7.37–7.21 (m, 5H), 6.68 (dq,
J¼19.6 Hz), 37.62. 19F NMR (254 MHz, CDCl3):
d
¼ꢀ128.31 (dt,
J¼32.1, 0.7 Hz, 1H), 4.77–4.68 (m, 1H), 4.20–4.17 (m, 2H), 3.35 (dd,
J¼46.2, 9.1 Hz). HRMS (FAB): m/z [MþNaþ] calcd for C19H18FNO3
J¼13.2, 3.0 Hz, 1H), 2.78 (dd, J¼13.2, 9.6 Hz, 1H), 2.14 (dd, J¼16.8,
-
NaSe: 430.0334; Found: 430.0343.
0.7 Hz, 3H). 13C NMR (68 MHz, CDCl3):
d
¼170.87 (d, J¼290.1 Hz),
Diastereomer b (miner): 1H NMR (270 MHz, CDCl3):
d
¼7.62–
161.21 (d, J¼1.7 Hz), 153.22, 135.21, 129.34, 128.85, 127.23, 98.22,
7.59 (m, 2H), 7.43–7.17 (m, 8H), 5.37 (td, J¼10.2, 4.8 Hz,1H), 4.88 (dt,
J¼47.1, 10.2 Hz, 1H), 4.73–4.51 (m, 2H), 4.27–4.18 (m, 2H), 3.23 (dd,
J¼13.7, 3.3 Hz, 1H), 2.86 (dd, J¼13.7, 9.1 Hz, 1H). 13C NMR (68 MHz,
66.05, 55.17, 37.94, 19.95 (d, J¼25.7 Hz). 19F NMR (254 MHz, CDCl3):
d
¼6.83 (dq, J¼32.1, 16.8 Hz). HRMS (FAB): m/z [MþHþ] calcd for
C14H15FNO3: 264.1036; Found: 264.1036.
CDCl3):
d
¼169.07 (d, J¼1.7 Hz), 152.74, 136.57, 134.70, 129.45,
129.38, 129.21, 128.87, 127.33, 124.76, 81.64 (d, J¼177.2 Hz), 66.15,
4.27. Ethyl 2-fluoromethyl-4-pentenoate (10)
55.43, 38.57 (d, J¼19.6 Hz), 37.80. 19F NMR (254 MHz, CDCl3):
d
¼ꢀ128.41 (dt, J¼47.1, 9.1 Hz). HRMS (FAB): m/z [MþNaþ] calcd for
The solution of AIBN (17 mg) in benzene (1 ml) was added to
a solution of 2a (55 mg) and allyl tri-n-butyltin (153 mg) in benzene
(4 ml) at ambient temperature, and then the solution was stirred
under reflux for 2 h. After the removal of the solvent by evapora-
tion, the residue was purified by column chromatography on silica
gel (hexane/AcOEt¼20/1) to provide a pure 10 (24 mg, yield: 75%).
C19H18FNO3NaSe: 430.0334; Found: 430.0323.
4.23. 4-Benzyl-3-[3-fluoro-2-(phenylselenyl)butanoyl]-
oxazolidin-2-one (5g)
Diastereomer a (major): 1H NMR (270 MHz, CDCl3):
(m, 2H), 7.37–7.29 (m, 8H), 5.19–4.96 (m, 2H), 4.79–4.70 (m, 1H),
d¼7.66–7.62
1H NMR (270 MHz, CDCl3):
2H), 4.74–4.42 (m, 2H), 4.19 (q, J¼7.3 Hz, 2H), 2.91–2.75 (m, 1H),
d
¼5.83–5.68 (m, 1H), 5.15–5.07 (m,

1566
H. Nagura et al. / Tetrahedron 65 (2009) 1559–1566
2.51–2.29 (m, 2H), 1.27 (t, J¼7.3 Hz, 3H). 13C NMR (68 MHz, CDCl3):
1H NMR (270 MHz, CDCl3):
d
¼4.73–4.37 (m, 2H), 4.19 (q,
d
¼172.07 (d, J¼5.6 Hz), 138.89, 117.72, 82.78 (d, J¼170.5 Hz), 60.88,
J¼7.1 Hz, 2H), 2.84–2.67 (m, 1H), 1.67–1.43 (m, 2H), 1.30–1.25 (m,
45.79 (d, J¼20.1 Hz), 31.86 (d, J¼6.7 Hz), 14.30. 19F NMR (254 MHz,
16H), 0.89 (t, J¼6.3 Hz, 3H). 13C NMR (68 MHz, CDCl3):
¼173.04 (d,
d
CDCl3):
d
¼ꢀ146.71 (td, J¼46.2, 18.5 Hz). HRMS (EI): m/z [Mþ] calcd
J¼5.0 Hz), 83.59 (d, J¼170.5 Hz), 60.73, 46.34 (d, J¼19.6 Hz), 31.88,
for C8H13FO2: 160.0900; Found: 160.0895.
29.49, 29.38, 29.26, 27.71 (d, J¼6.7 Hz), 27.00, 22.73, 14.31, 14.20. 19F
NMR (254 MHz, CDCl3):
d
¼ꢀ144.43 (td, J¼46.2, 16.8 Hz). HRMS
(FAB): m/z [MþNaþ] calcd for C13H25FO2Na: 255.1736; Found:
4.28. Ethyl 4-butoxy-2-(fluoromethyl)butanoate (11)
255.1734.
A solution of 2a (27 mg) and n-butyl vinyl ether (205 mg) in
CH2Cl2 (10 ml) was bubbled with N2 at ambient temperature for
15 min, and then photolyzed for 60 min with 6-W low-pressure
mercury-vapor lamp. The reaction was conducted using a quartz
vessel. After the photolysis, the resulting solution was evaporated
under vacuum and the residue was purified by HPLC (Develosil
ODS-5, MeCN as eluent) to provide pure products 11 (4.4 mg, yield:
20%).
Acknowledgements
The authors thank Ms. M. Ishikawa of Center for Advanced
Materials Analysis (Suzukakedai), Technical Department, Tokyo
Institute of Technology, for HRMS analysis and Morita Chemical
Industries Co. Ltd for generous gifts of Et3N$3HF and Et3N$5HF.
1H NMR (270 MHz, CDCl3):
d
¼4.74–4.63 (m, 1H), 4.57–4.46 (m,
References and notes
1H), 4.18 (q, J¼7.1 Hz, 2H), 3.50–3.36 (m, 4H), 3.00–2.83 (m, 1H),
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2.06–1.91 (m, 1H), 1.86–1.72 (m, 1H), 1.59–1.25 (m, 7H), 0.91 (t,
J¼7.4 Hz, 3H). 13C NMR (68 MHz, CDCl3):
¼172.65 (d, J¼5.0 Hz),
d
83.56 (d, J¼170.5 Hz), 70.81, 67.87, 60.83, 43.61 (d, J¼19.7 Hz), 31.81,
27.87 (d, J¼5.6 Hz), 19.41, 14.28, 14.00. 19F NMR (254 MHz, CDCl3):
d
¼ꢀ145.03 (td, J¼46.0, 20.3 Hz). HRMS (FAB): m/z [MþHþ] calcd for
C11H22FO3: 221.1553; Found: 221.1558.
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4.29. Ethyl 2-(fluoromethyl)decanoate (12)
A solution of 2a (27 mg) and 1-octene (230 mg) in CH2Cl2
(10 ml) was bubbled with N2 at ambient temperature for 15 min,
and then photolyzed for 75 min with 6-W low-pressure mercury-
vapor lamp. The reaction was conducted using a quartz vessel. After
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uum and the residue was purified by HPLC (Develosil ODS-5, MeCN
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