Electrolytic partial fluorination of organic compounds. Part 60: Highly regioselective anodic fluorination of aryl propargyl sulfides

Article abstract of DOI:10.1016/S0040-4020(02)00559-8

Aryl propargyl sulfides were subjected to electrochemical fluorination in dimethoxyethane (DME) containing various fluoride supporting electrolytes using an undivided cell to provide the corresponding α-monofluorinated or α,α-difluorinated sulfides selectively as main products in good yields depending on the amount of electricity passed. The α,α-difluorinated sulfides were stable enough to be isolated while the α-monofluorinated ones were very unstable. The α-monofluorinated sulfides were readily converted into the corresponding stable α-monofluoroallenyl sulfides in good yields. Furthermore, synthetic utility of α-monofluoroallenyl sulfides was also investigated.

Full text of DOI:10.1016/S0040-4020(02)00559-8

TETRAHEDRON
Pergamon
Tetrahedron 58 (2002) 5877±5883
Electrolytic partial ¯uorination of organic compounds. Part 60:
Highly regioselective anodic ¯uorination of aryl propargyl sul®desq
Sayed M. Riyadh, Hideki Ishii and Toshio Fuchigamip
Department of Electronic Chemistry, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8502, Japan
Received 10 April 2002;accepted 29 May 2002
AbstractÐAryl propargyl sul®des were subjected to electrochemical ¯uorination in dimethoxyethane (DME) containing various ¯uoride
supporting electrolytes using an undivided cell to provide the corresponding a-mono¯uorinated or a,a-di¯uorinated sul®des selectively as
main products in good yields depending on the amount of electricity passed. The a,a-di¯uorinated sul®des were stable enough to be isolated
while the a-mono¯uorinated ones were very unstable. The a-mono¯uorinated sul®des were readily converted into the corresponding stable
a-mono¯uoroallenyl sul®des in good yields. Furthermore, synthetic utility of a-mono¯uoroallenyl sul®des was also investigated. q 2002
Elsevier Science Ltd. All rights reserved.
1. Introduction
allenyl phosphonates have very recently been reported.8
a-Fluoroallenyl sul®des are also expected to be useful as
the ¯uorobuilding blocks. However, there have been no
report on the synthesis of a-¯uoroallenyl sul®des so far.
Previously, we found that sul®des bearing electron-with-
drawing groups underwent selective anodic ¯uorination
with good ef®ciencies.9 Since an acetylenic group is also
an electron-withdrawing group, we have attempted anodic
¯uorination of sul®des having an acetylenic group, i.e. aryl
propargyl sul®des.
Selective incorporation of ¯uorine atom(s) into organic
compounds is of great importance in chemical industry
and medicinal chemistry. Organo¯uorine compounds are
currently used as lubricants, coatings, textile chemicals,
agrochemicals, and pharmaceuticals.2
Among organo¯uorine compounds, di¯uoromethylene
compounds attract much interest since the unique stereo-
electronic properties of a gem-di¯uoromethylene group
have widespread utilization in pharmacologically active
substances. For example, the presence of a di¯uoromethyl-
ene group has aided in the formation of stable hydrate and
hemiacetals capable of inhibiting proteases and esterases.3
A di¯uoromethylene group has been employed as an
isoelectronic±isosteric replacement for the oxygen atom
in the phosphate analogues,4 and in the synthesis of
b,b-di¯uro-a-aminoacids,5 and ¯uorinated arachidonic
acid.6 However, the construction of a di¯uoromethylene
group is not easy and very often requires a large amount
of oxidizing, toxic or costly reagents.7 On the other hand,
the ®rst synthesis and synthetic application of a-¯uoro-
In this paper, we report the ®rst successful regioselective
anodic mono- and di¯uorination of aryl propargyl sul®des
using various ¯uoride salts in DME together with the novel
synthesis of a-¯uoroallenyl sul®des from the anodically
¯uorinated a-¯uoropropargyl sul®des.10
2. Results and discussion
2.1. Preparation of aryl propargyl sul®des 1a±c
The starting aryl propargyl sul®des 1a±c were prepared in
Scheme 1.
q See Ref. 1.
Keywords: electrochemical ¯uorination; a-mono¯uorinated; a-mono¯uoroallenyl sul®des.
Corresponding author. Tel./fax: 181-45-924-5406;e-mail: fuchi@echem.titech.ac.jp
p
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00559-8

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S. M. Riyadh et al. / Tetrahedron 58 (2002) 5877±5883
Scheme 2.
good yields by the reaction of the corresponding thiophenols
with propargyl bromide in a re¯uxing ethanol solution
containing sodium ethoxide as shown in Scheme 1.11,12 On
the other hand, 3-phenyl-2-propynyl phenyl sul®de (1d) was
prepared as shown in Scheme 2.13
potential of sul®des, the anodic peak potentials of 1 were
measured by cyclic voltammetry in an anhydrous aceto-
nitrile solution containing Bu4NBF4 (0.1 M) using a plati-
num disc electrode and SSCE as a reference electrode.
These sul®des exhibited irreversible anodic waves. The
®rst oxidation peak potentials (Epox) of these sul®des 1 are
summarized in Table 1.
2.2. Oxidation potentials of aryl propargyl sul®des 1±4
It was found that substitution on either the acetylenic group
or the benzene ring affected the oxidation potentials of
sul®des signi®cantly. Substituted acetylenic sul®des 1d
was oxidized at a more positive potential than the corre-
sponding phenyl propargyl sul®de (1a) due to the elec-
tron-withdrawing effect of the phenyl group. The presence
of an electron-withdrawing chlorine atom on the phenyl ring
caused a considerable increase in Epox while the presence of
an electron-donating methyl group caused a little decrease
in Epox when compared with unsubstituted phenyl propargyl
sul®de (1a).
In order to investigate the substituent effect on the oxidation
Table 1. Oxidation potentials (peak potentials Epox) of aryl propargyl
sul®des 1a±d
Sul®de
R1
Epox (V vs. SSCE)a
No.
R2
1a
1b
1c
1d
H
H
H
H
Ph
1.66
1.85
1.62
1.76
As shown in Table 2, the oxidation potential of propargyl
sul®de is higher than those of the corresponding acetyl and
ester derivatives but lower than that of a cyano derivative.
Cl
Me
H
a
Substrate (0.01 M) in 0.1 M Bu4N´BF4/MeCN;sweep rate: 100 mV/s.
As shown in Fig. 1, a good linear correlation of oxidation
potentials (Epox) of the sul®des with Taft's (sp) values14 for
these substituent groups was obtained. This indicates that
the ®rst electron-transfer from the substrate to the anode
may be the oxidation potential determining step.
Table 2. Oxidation potentials (Epox) of organosulfur compoundsa [PhS±
CH2±EWG]
EWG
Epox (V vs. SSCE)
H
1.41
1.53
1.53
1.66b
1.75
2.3. Anodic ¯uorination of aryl propargyl sul®des 1a±d
COMe
COOEt
CuCH
CN
Anodic ¯uorination of phenyl propargyl sul®de (1a) as a
model compound was carried out at a constant current in
an undivided cell under various conditions. The results are
summarized in Table 3.
a
Substrate (0.01 M) in 0.1 M NaClO4/MeCN;scan rate:100 mV/s.
Substrate (0.01 M) in 0.1 M Bu4N´BF4/MeCN;Pt disc electrode
(fˆ1 mm);scan rate: 100 mV/s.
b
Fluorination proceeded regardless of electrolytic conditions
Figure 1. Relationship between oxidation potentials (Epox) and substituent constants (sp).

S. M. Riyadh et al. / Tetrahedron 58 (2002) 5877±5883
5879
Table 3. Anodic ¯uorination of phenyl propargyl sul®de 1a under various electrolytic conditions
Run
Solvent
Supporting electrolyte
Charge passed (F/mol)
Yield (%)a
2a
3a
1
2
3
4
5
6
7
DME
DME
DME
DME
DME
DME
MeCN
Et4NF´4HF
Et4NF´4HF
Et4NF´4HF
Et4NF´4HF
Et3N´3HF
Et3N´5HF
Et4NF´4HF
1
2
3
4
4
4
4
30
43
52
64
53
77
25
0
5
11
13
40
17
12
a
Calculated by 19F NMR.
Figure 2. Effect of charge passed on the anodic ¯uorination of phenyl propargyl sul®de (1a) in Et4NF´4HF/DME.
to provide a-mono- and a,a-di¯uorinated products 2a and
3a. A ¯uorine atom was regioselectively introduced into the
position a to the sulfur atom. Fluorination at the acetylenic
group or phenyl ring did not take place at all. Regardless of
supporting ¯uoride salts, acetonitrile was not suitable for the
¯uorination due to the passivation of the anode (run 7). On
the other hand, the use of DME provided mainly a-mono-
¯uorinated sul®de 2a. Among the ¯uoride salts used,
Et3N´5HF gave the best result (run 6) and Et4NF´4HF was
also suitable for the selective formation of 2a (run 4). When
Et3N´3HF was used, the ¯uorinated product 2a was formed
considerably (run 5).
yield of a-mono¯uorinated sul®de 2a increased with an
increase of the electricity and at 4 F/mol of electricity the
maximum yield (64%) was obtained, and then the yield
decreased. On the other hand, the yield of a,a-di¯uorinated
sul®de 3a increased largely after 4 F/mol was passed. At
8 F/mol of electricity, the maximum yield (70%) was
obtained. Even at 2 F/mol, a,a-di¯uorinated sul®de 3a
was already formed appreciably as a by-product. When
10 F/mol was passed, a,a-di¯uorinated product 3a was
obtained exclusively. These results clearly suggest that 3a
was formed via 2a.
As shown in Table 3 and Fig. 2, a,a-di¯uorinated sul®de
3a was always formed as a by-product under constant
current electrolytic conditions even at the early stage of
the electrolysis. Therefore, constant potential anodic
oxidation of 1a at 1.5 V (vs SSCE) was attempted. In this
case, the desired mono¯uorinated product 2a was formed
exclusively in good yield as shown in Scheme 3.
Next, the relationship between the yields of the products, 2a
and 3a and the electricity passed was investigated at a
constant current using Et4NF´4HF. As shown in Fig. 2, the
Next, the effect of supporting ¯uoride salts on the anodic
di¯uorination of 1a was investigated. In this case, a large
excess amount of electricity was passed in order to obtain 3a
selectively. As shown in Table 4, the use of Et3N´3HF gave
Scheme 3.

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S. M. Riyadh et al. / Tetrahedron 58 (2002) 5877±5883
Table 4. Anodic di¯uorination of aryl propargyl sul®des 1a±d
Run
Sul®de
R1
Supporting electrolyte
Charge passed (F/mol)
Yield (%)a
No.
R2
2
3
1
2
3
4
5
6
7
1a
1a
1a
1a
1b
1c
1d
H
H
H
H
Cl
Me
H
H
H
H
H
H
H
Ph
Et4NF´4HF
Et4NF´4HF
Et3N´3HF
Et3N´5HF
Et3N´3HF
Et3N´3HF
Et3N´3HF
8
10
8
8
8
22
0
21
20
5
70
55
75(70)
65
72 (66)
67 (62)
65 (63)
6
10
20
0
a
Determined by 19F NMR;isolated yields are shown in parantheses.
the highest yield of 3a (run 3) and Et4NF´4HF was also
effective for the di¯uorination (run 1). The use of
Et3N´5HF gave lower yield (run 4). Longer electrolysis of
1a resulted in exclusive formation of 3a although the yield
decreased appreciably (run 2). Previously, we found that
Et4NF´4HF/MeCN was effective for a,a-di¯uorination of
sul®des having various electron-withdrawing groups but
Et3N´3HF/MeCN was not suitable.15 In contrast, only poor
yield (14%) of 2a was obtained in Et4NF´4HF/MeCN but
the use of Et3N´3HF/DME gave 3a in good yield (75%) (run
3). Consequently, MeCN electrolytic solutions were not
suitable for the formation of 3. On the other hand, DME
was suitable because it did not cause anode passivation
although excess amount of electricity is necessary due to
oxidation of DME itself. Furthermore, DME strongly
solvates the cationic part of the ¯uoride salt to make the
¯uoride ion more reactive. Consequently, the ¯uoride ion
easily attacks on the anodically generated cationic inter-
mediate (Scheme 6).16 In support of this, DME has much
higher donor number (23.9) than MeCN (14.1).17 Therefore,
a solvent effect of DME on the anodic ¯uorination is
notable.16
Anodic di¯uorination of other aryl propargyl sul®des 1b±d
was also carried out in Et3N´3HF/DME. As shown in Table
4, a,a-di¯uorinated sul®des 3b±d were predominantly
(runs 5 and 6) or exclusively (run 7) formed. In this case,
¯uorination of DME also occurred simultaneously.18 The
di¯uorinated products 3b±d were readily isolated by
column chromatography. In the case of p-tolyl sul®de 1c,
benzylic ¯uorination did not take place at all although
anodic benzylic substitution easily takes place (run 6). In
the case of 1d, neither phenyl nor acetylenic ¯uorination did
not occur and a,a-di¯uorinated product 3d was obtained
exclusively. Therefore, this ¯uorination is highly regio-
selective.
2.4. Synthesis of a-¯uoroallenyl sul®des 4a±c
Although a-¯uoropropargyl sul®de 2a was formed in good
yield, the isolation of pure 2a was unsuccessful due to its
unstability.19 Therefore, we attempted to convert 2a into a
more stable derivative. Thus, the electrolytic solution
containing a crude product 2a was basi®ed by addition of
an ethanol solution of sodium ethoxide and the resulting
Scheme 4.

S. M. Riyadh et al. / Tetrahedron 58 (2002) 5877±5883
5881
Scheme 5.
stable a-¯uoroallenyl sul®de 4a was easily isolated in
good yield as shown in Scheme 4 (isolated yields of 4
were shown). Other a-¯uoropropargyl sul®des 2b and 2c
were similarly converted into the corresponding a-¯uoro-
allenyl sul®des 4b and 4c in moderate yields. Thus, we
successfully prepared a-¯uoroallenyl sul®des for the ®rst
time.
On the other hand, treatment of 4b with benzylamine
provided a-¯uoroacetonyl sul®de 6 due to the contaminated
water in benzylamine as shown in Scheme 6. However, even
when anhydrous benzylamine was used, no hydroamination
product was formed and the starting 4b was mostly
recovered. This is in sharp contrast to that a-¯uoroallenyl
phosphonates undergo hydroamination ef®ciently.
Scheme 6.
2.5. Synthetic utility of a-¯uoroallenyl sul®des
In order to disclose the role of acetylenic group, anodic
¯uorination of allyl phenyl sul®de was attempted. However,
many complicated products were formed. Therefore, a
strongly electron-withdrawing acetylenic group is essential
for this regioselective anodic ¯uorination (Scheme 7).
The allene unit itself is a synthetically useful functional
group,20 and its chiral nature has recently been used
advantageously in asymmetric synthesis.21 a-Fluoroallenyl
Scheme 7.
sul®des 4a±c are hitherto unknown ¯uorinated molecules,
which seem to be useful ¯uorinated building blocks. Zepta
and Hammond reported the reaction of a-¯uoroallenyl
phosphonates with various reagents such as iodine and
amines.8 To investigate the synthetic utility of a-¯uoro-
allenyl sul®des, the addition of iodine was initially
examined. Generally, 1,1-disubstituted allenes regio-
selectively add I2 across the C2±C3 bond to afford the
more highly substituted ole®nes.22 In this case, treatment
of a-¯uoroallenyl sul®de 4b with I2 in CH2Cl2 at room
temperature afforded exclusively (E)-diiodo 5 equipped
with two valuable synthetic handles such as allyl- and vinyl-
iodine in moderate yield as shown in Scheme 5.
The high regioselectivity can be explained in terms of
facilitation of deprotonation of the ¯uorosulfonium ion
intermediate A by the strong electron-withdrawing acetyl-
enic group as shown in Scheme 8.23
N-Fluoropyridinium salts are known to be good ¯uorinating
reagents.24 The chemical ¯uorination of phenyl propargyl
sul®de 1a as a model compound was also attempted.
However, treatment of 1a with various N-¯uoropyridinium
tri¯ates in dichloromethane at either room temperature or
under re¯ux resulted in no formation of ¯uorinated products
as shown in Scheme 9. The ¯uorination did not proceed
even in the presence of Et3N.25
Scheme 8.

5882
S. M. Riyadh et al. / Tetrahedron 58 (2002) 5877±5883
Scheme 9.
In summary, we have successfully carried out anodic mono-
and di¯uorination of aryl propargyl sul®des for the ®rst time
and the mono¯uorinated products were readily transformed
into stable a-¯uoroallenyl sul®des. Synthetic utility of
a-¯uoroallenyl sul®des was also demonstrated.
3.1.2. p-Chlorophenyl a-¯uoropropargyl sul®de (2b). 1H
NMR d 2.97 (dd, 1H, Jˆ4.6, 2 Hz), 6.31 (dd, 1H, Jˆ54,
2 Hz), 7.34 (d, 2H, Jˆ8.6 Hz), 7.51 (d, 2H, Jˆ8.6 Hz); 19F
NMR d 262.52 (dd, Jˆ54, 4.6 Hz);MS ( m/z) 200 (M1),
HRMS calcd for C9H6ClFS: 199.9863. Found: 199.9860.
1
3.1.3. a-Fluoropropargyl p-tolyl sul®de (2c). H NMR d
3.03 (dd, 1H, Jˆ4.6, 2.3 Hz), 6.41 (dd, 1H, Jˆ54, 2.3 Hz),
7.1±7.3 (m, 4H); 19F NMR d 263.48 (dd, Jˆ54, 4.6 Hz);
MS (m/z) 180 (M1), HRMS calcd for C10H9FS: 180.0409.
Found: 180.0412.
3. Experimental
Caution. Et4NF´4HF and Et3N´5HF are toxic and if in
contact with skin causes serious burns, and therefore proper
safety precautions should be taken all the time;it is there-
fore recommended to protect hands with rubber gloves.26
3.1.4. a,a-Di¯uoropropargyl phenyl sul®de (3a). 1H
NMR d 2.98 (t, 1H, Jˆ4.3 Hz), 7.2±7.6 (m, 5H); 19F
NMR d 16.7 (d, Jˆ4.3 Hz);MS ( m/z) 184 (M1), HRMS
calcd for C9H6F2S: 184.0158. Found: 184.0157.
1H NMR and 19F NMR spectra were recorded at 270 and
254 MHz respectively, in CDCl3. The chemical shifts for 1H
NMR are given in d ppm down®eld from internal TMS,
and the chemical shifts for 19F NMR are given in d ppm
down®eld from external CF3COOH.
3.1.5. p-Chlorophenyl a,a-di¯uoropropargyl sul®de
1
(3b). H NMR d 3.03 (t, 1H, Jˆ4.2 Hz), 7.4 (d, 2H, Jˆ
8.2 Hz), 7.5 (d, 2H, Jˆ8.2 Hz); 19F NMR d 15.6 (d, Jˆ
4.2 Hz);MS ( m/z) 218 (M1), 183 (M12Cl). Anal. calcd
for C9H5ClF2S: C, 49.44;H, 2.30. Found: C, 49.11;H, 2.78.
Materials. Phenyl propargyl sul®de (1a),11 p-tolyl propargyl
sul®de (1c),11 p-chlorophenyl propargyl sul®de (1b),12 and
3-phenyl-2-propynylphenyl sul®de (1d)13 were prepared
according to the literature. Et4NF´4HF and Et3N´5HF were
obtained from Morita Chemical Industries Co. Ltd. (Japan).
3.1.6. a,a-Di¯uoropropargyl p-tolyl sul®de (3c). 1H NMR
d 2.9 (t, 1H, Jˆ4.6 Hz), 2.38 (s, 3H), 7.1±7.6 (m, 4H); 19F
NMR d 15.7 (d, Jˆ4.6 Hz);MS ( m/z) 198 (M1), 183
(M12CH3), HRMS calcd for C10H8F2S: 198.0315. Found:
198.0324.
3.1. Anodic mono- and di¯uorination of aryl propargyl
sul®des
3.1.7. 1,1-Di¯uoro-1-phenylthio-3-phenylpropyne (3d).
1H NMR d 7.3±7.7 (m, 10H); 19F NMR d 18.5 (s);MS
(m/z) 260 (M1), 183 (M12Ph). Anal. calcd for
C15H10F2S: C, 69.21;H, 3.87. Found: C, 69.19;H, 4.10.
In a typical anodic ¯uorination, constant current electrolysis
(5 mA/cm2) of 1 (1 mmol) was carried out at platinum
electrodes (3£3 cm2) at room temperature in DME
(30 mL) containing 0.37 M ¯uoride salt using an undivided
cell under nitrogen atmosphere. After electrolysis, the
supporting electrolyte was removed by silica gel short
column chromatography using ethyl acetate and the eluent
was evaporated under reduced pressure to give 2a±c and
3a±d. The yields of the ¯uorinated products were estimated
by means of 19F NMR using a known amount of mono-
¯uorobenzene as an internal standard: the yields were
calculated on the basis of the integral ratios between the
mono¯uorobenzene and the ¯uorinated products. The
products 2a±c could not be puri®ed completely due to
their instability. On the other hand, the products 3a±d
were further puri®ed by column chromatography on silica
gel using pentane as eluent to obtain pure 3a±d.
3.2. Preparation of a-¯uoroallenyl sul®des 4a±c
After electrolytic ¯uorination was carried out as above, the
electrolytic solution containing a-¯uoropropargyl sul®des
2a±c were dissolved in ethanolic sodium ethoxide solution
prepared from sodium metal (0.023 g, 1 mg atom) in ethanol
(20 mL) and the mixture was stirred at room temperature for
3 h and then the reaction mixture was neutralized with aq.
HCl. The product was extracted with chloroform and dried
over anhydrous MgSO4. The solvent was removed under
reduced pressure and the residue was puri®ed with prepara-
tive thin layer chromatography using pentane as eluent.
3.2.1. a-Fluoroallenyl phenyl sul®de (4a). 1H NMR d 5.09
(d, 2H, Jˆ3.2 Hz), 7.2±7.5 (m, 5H); 19F NMR d 240.05 (t,
Jˆ3.2 Hz);MS ( m/z) 166 (M1), 165 (M12H), HRMS calcd
for C9H7FS: 166.0253. Found: 166.0239.
3.1.1. a-Fluoropropargyl phenyl sul®de (2a). 1H NMR d
3.03 (dd, 1H, Jˆ4.6, 2.3 Hz), 6.41 (dd, 1H, Jˆ53.8, 2.3 Hz),
7.3±7.6 (m, 5H); 19F NMR d 262.82 (dd, Jˆ53.8, 4.6 Hz);
MS (m/z) 166 (M1), HRMS calcd for C9H7FS: 166.0253.
Found: 166.0239.
3.2.2. p-Chlorophenyl a-¯uoroallenyl sul®de (4b). 1H NMR

S. M. Riyadh et al. / Tetrahedron 58 (2002) 5877±5883
5883
Bioorganic Chemistry, Welch, J. T., Eswarakrishan, S., Eds.;
Wiley: New York, 1991. (c) Hiyama, T. Organo¯uorine
Compounds. Chemistry and Applications;Springer: Berlin,
2000.
d 5.5 (d, 2H, Jˆ2.6 Hz), 7.4 (d, 2H, Jˆ8.2 Hz), 7.5 (d, 2H,
Jˆ8.2 Hz); 19F NMR d 245.13 (t, Jˆ2.6 Hz);MS ( m/z) 200
(M1), 165 (M12Cl). Anal. calcd for C9H6ClFS: C, 53.87;
H, 3.01. Found: C, 53.53;H, 3.06, HRMS calcd for
C9H6ClFS: 199.9863. Found: 199.9874.
3. Altenburger, J. M.;Schirlin, D. Tetrahedron Lett. 1991, 32,
7255.
3.2.3. a-Fluoroallenyl p-tolyl sul®de (4c). 1H NMR d 2.31
(s, 3H), 5.5 (d, 2H, Jˆ3.1 Hz), 7.1±7.4 (m, 4H); 19F NMR d
245.84 (t, Jˆ3.1 Hz);MS ( m/z) 180 (M1), 165 (M12CH3),
HRMS calcd for C10H9FS: 180.0409. Found: 180.0414.
4. (a) Yokomatsu, T.;Abe, H.;Yamagishi, T.;Suemune, K.;
Shibuya, S. J. Org. Chem. 1999, 64, 8413. (b) O'Hagan, D.;
Rzepa, H. S. J. Chem. Soc., Chem. Commun. 1997, 645.
5. Shi, G.;Cai, W. J. Org. Chem. 1995, 60, 6289.
6. Kwok, P. Y.;Muellner, F. W.;Chen, C. K.;Fried, J. J. Am.
Chem. Soc. 1987, 109, 3684.
3.3. Iodination of a-¯uoroallenyl sul®de 4b
7. Chemistry of Organo¯uorine Compounds, Hudlicky, M.,
Pavlath, A. E., Eds.;American Chemical Society: Washing-
ton, DC, 1995;p. 41.
To a stirred solution of 4b (0.2 g, 1 mmol) was added a
solution of iodine (0.304 g, 1.2 mmol) in CH2Cl2 (15 mL),
and the mixture was stirred at room temperature for 4 h. The
reaction mixture was quenched with 5% Na2S2O3 (25 mL),
and extracted with CHCl3. The combined organic layers
were dried and concentrated. The crude product was
puri®ed by column chromatography on silica gel using
pentane as an eluent.
8. Zepata, A. J.;Gu, Y.;Hammond, G. B. J. Org. Chem. 2000,
65, 227.
9. (a) Fuchigami, T.;Shimojo, M.;Konno, A.;Nakagawa, K.
J. Org. Chem. 1990, 55, 6074. (b) Fuchigami, T.;Shimojo,
M.;Konno, A. J. Org. Chem. 1995, 60, 3459. (c) Fuchigami,
T. 4th ed, Organic Electrochemistry;Lund, H., Hammerich,
O., Eds.;Marcel Dekker: New York, 2001;Vol. 25.
(d) Fuchigami, T. Advances in Electron Transfer Chemistry;
Mariano, P. S., Ed.;JAI: CN, 1999;Vol. 6, p. 41.
10. For preliminary report: Riyadh, S. M.;Ishii, H.;Fuchigami, T.
Tetrahedron Lett. 2001, 42, 3009.
3.3.1. (E)-p-Chlorophenyl 1-¯uoro-2,3-diiodo-1-propenyl
1
sul®de (5). H NMR d 4.6 (s, 2H), 7.4 (d, 2H, Jˆ8.2 Hz),
7.5 (d, 2H, Jˆ8.2 Hz); 19F NMR d 18.84 (s);MS ( m/z) 327
(M12I). Anal. calcd for C9H6ClFI2S: C, 23.79;H, 1.33;I,
55.85;S, 7.06. Found: C, 23.88;H, 1.38;I, 55.64, S, 7.11.
11. Sato, K.;Miyamoto, O. Nippon Kagaku Zasshi 1956, 77,
1409.
3.4. Reaction of a-¯uoroallenyl sul®de 4b with
benzylamine
12. Pourcelot, G.;Cadiot, P. Bull. Soc. Chim. Fr. 1966, 3016.
13. Fartes, C. C.;Garrote, C. F. Synth. Commun. 1993, 23, 2869.
14. Taft, R. W. Steric Effect in Organic Chemistry;Wiley: New
York, 1956 Chapter 13.
The mixture of a-¯uoroallenyl sul®de 4b (0.2 g, 1 mmol)
and benzylamine (0.107 g, 1 mmol) in THF (20 mL) was
stirred at room temperature for 40 h. The reaction was
diluted with water, and extracted with chloroform repeat-
edly. The combined organic layers were collected, dried
over anhydrous MgSO4 and ®ltered. The ®ltrate was
evaporated under reduced pressure, and the residue was
puri®ed by column chromatography on silica gel using a
hexane/ethylacetate eleuent (5:1) to give pure 6.
15. Fuchigami, T.;Konno, A. J. Org. Chem. 1997, 62, 8579.
16. (a) Hou, Y.;Fuchigami, T. J. Electrochem. Soc. 2000, 147,
4567. (b) Shaaban, M. R.;Ishii, H.;Fuchigami, T. J. Org.
Chem. 2000, 65, 8685. (c) Dawood, K. M.;Higashiya, S.;
Hou, Y.;Fuchigami, T. J. Fluorine Chem. 1998, 93, 159.
(d) Dawood, K. M.;Fuchigami, T. J. Org. Chem. 1999, 64,
138.
17. Gutmann, V.;Wychera, E. Inorg. Nucl. Chem. Lett. 1996, 2,
257.
1
3.4.1. p-Chlorophenyl a-¯uoroacetonyl sul®de (6). H
18. (a) Hou, Y.;Fuchigami, T. Tetrahedron Lett. 1999, 40, 7819.
(b) Ishii, H.;Hou, Y.;Fuchigami, T. Tetrahedron 2000, 56,
8877.
NMR d 2.14 (s, 3H), 5.87 (d, 1H, Jˆ51 Hz), 7.34 (d, 2H,
Jˆ8.2 Hz), 7.45 (d, 2H, Jˆ8.2 Hz); 19F NMR d 282.92 (d,
Jˆ51 Hz)); 13C NMR d 27.43 (CH3), 98.55, 128.64, 130.66,
136.41, 137.13 (CH), 199.77 (CO);MS ( m/z) 218 (M1).
Anal. calcd for C9H8ClFOS: C, 49.43;H, 3.69;S, 14.66.
Found: C, 49.29;H, 3.51;S, 14.42.
19. a-Fluoropropargyl sul®des 2a±c were very unstable. Even in
a diluted solution stored in a refrigerator, they gradually
decomposed within 12 h.
20. (a) Trost, B. M.;Michelly, P. Y.;Gerusz, V. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 1750. (b) Morwick, T. M.;Paquett,
L. A. J. Org. Chem. 1997, 62, 627.
Acknowledgements
21. Mikami, K.;Yoshida, A. Angew. Chem., Int. Ed. Engl. 1997,
36, 858.
This work was ®nancially supported by a Grant-in-Aid for
Scienti®c Research (No. 12555252) from the Ministry of
Education, Science, Sports and Culture of Japan. We are
also grateful to Morita Chemical Industries Co., Ltd., for
generous gifts of ¯uoride salts.
22. Schuster, H. F.;Coppola, G. M. Allenes in Organic Synthesis;
Wiley: New York, 1984.
23. Fuchigami, T.;Konno, A.;Nakagawa, K.;Shimojo, M. J. Org.
Chem. 1994, 59, 5937.
24. (a) Umemoto, T.;Tomizawa, G. Bull. Chem. Soc. Jpn 1986,
59, 3625. (b) Umemoto, T.;Tomizawa, G. J. Org. Chem.
1995, 60, 8565.
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