Selective trifluorination of alkyl aryl sulfides using IF5

Article abstract of DOI:10.1016/j.tet.2004.09.076

In the reaction of IF₅ with alkyl aryl sulfides in heptane under reflux conditions, the arylthio group migrated once and three fluorine atoms were selectively introduced on the alkyl chain. In order to find the reason why the reaction stopped at the trifluorination step, we examined the oxidation potentials of the starting material, a reaction intermediate, and the product, and the time course of the reactions. Graphical Abstract.

Full text of DOI:10.1016/j.tet.2004.09.076

Tetrahedron 60 (2004) 11445–11451
Selective trifluorination of alkyl aryl sulfides using IF5
*
Shinichi Ayuba, Chiharu Hiramatsu, Tsuyoshi Fukuhara and Shoji Hara
Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Received 9 June 2004; accepted 17 September 2004
Available online 13 October 2004
Abstract—In the reaction of IF5 with alkyl aryl sulfides in heptane under reflux conditions, the arylthio group migrated once and three
fluorine atoms were selectively introduced on the alkyl chain. In order to find the reason why the reaction stopped at the trifluorination step,
we examined the oxidation potentials of the starting material, a reaction intermediate, and the product, and the time course of the reactions.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
By using 2.4 equiv of IF5, 4a could be selectively obtained
and the formation of 3a was not observed. When the
reaction was carried out at 40 8C in a tight-screw capped
vessel, the arylthio group migrated twice and 1,2,2,3,3-
pentafluoro-1-(p-chlorophenylthio)propane (2a) was
obtained as the main product. However, under reflux in
heptane, the main product was 4a even after 6 h, and 2a was
formed only as a minor product (5%) (Table 1).
Oxidative fluorination of sulfur compounds has been
conveniently used to introduce one or several fluorine
atoms into organic molecules under mild conditions.1
Recently, we have found that an arylthio group of alkyl
aryl sulfides migrated on the carbon chain successively to
the terminal carbon by the reaction with IF5 at 40 8C in a
tight-screw capped vessel, and the fluorination took place on
the carbon where the arylthio group was attached.2 Finally,
3–7 fluorine atoms could be introduced into the alkyl chains
depending on the alkyl chain length (Scheme 1). During our
continuous study of fluorination using IF5, we found that
three fluorine atoms can be selectively introduced into the
alkyl chain of the alkyl aryl sulfides regardless of the alkyl
chain length by carrying out the reaction in heptane under
reflux conditions.
When isolated 4a was subjected to the reaction with IF5 at
40 8C in the tight-screw capped vessel for 28 h, further
fluorination and migration of the arylthio group took place
to give 2a as the main product (Scheme 2).
Various alkyl aryl sulfides were used for the reaction with
IF5 under reflux condition in heptane (Table 2). When an
electron-donating group was attached at the p-position of a
phenyl group (1b), 1.2 equiv of IF5 was enough to obtain the
trifluorinated product (4b). On the other hand, the presence
of a strong electron-withdrawing group (1c) retarded the
reaction, and longer reaction time and large excess of IF5
were required to complete the reaction. When phenyl propyl
sulfide was used, a competitive iodination by in situ-
generated IF3 at the p-position of the phenyl group took
place,4 and a mixture of 1,1,2-trifluoro-2-phenylthiopropane
and 1,1,2-trifluoro-2-(p-iodophenylthio)propane was
formed. In all cases, the arylthio group migrated only
once and three fluorine atoms were introduced into the
sulfides regardless of the alkyl chain length. The functional
groups such as ester (1h) or amide (1i), can tolerate the
reaction conditions.
Scheme 1.
2. Results and discussion
When p-chlorophenyl propyl sulfide (1a) was allowed to
react with 1.2 equiv of IF5 in heptane under reflux condition
for 1 h, the arylthio group migrated once and a mixture of
1,1-difluoro-2-(p-chlorophenylthio)propane (3a) and 1,1,2-
trifluoro-2-(p-chlorophenylthio)propane (4a) was obtained.
As previously proposed,2 the fluorination and migration of
the arylthio group proceed as follows. In the first step,
oxidation of the sulfur in 1a takes place to give a sulfonium
intermediate which gives mono-fluorinated product 5a,5 or a
Keywords: Halogenation; Hypervalent elements; Migration; Sulfides.
* Corresponding author. Tel./fax: C81 11 706 6556;
e-mail: hara@org-mc.eng.hokudai.ac.jp
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.09.076

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S. Ayuba et al. / Tetrahedron 60 (2004) 11445–11451
Table 1. Reaction of 1a with IF5 under various conditionsa
Amount of IF5 (eq to 1a)
Reaction time (h)
Yield (%)b
3a
4a
2a
1.2
2.4
2.4
2.4c
1
1
6
48
43
0
0
17
74
72
0
0
0
5
72
0
a If otherwise not mentioned, the reaction was carried out in heptane under reflux.
b Isolated yield based on 1a.
c The reaction was carried out in hexane at 40 8C in a tight-screw capped vessel.
vinylic sulfide.6 Addition of in situ-generated IF to the
vinylic sulfide gives 1-arylthio-1-fluoro-2-iodopropane
(6a).3 Then elimination of an iodide, migration of the
arylthio group, and fluorination at the terminal carbon take
place successively to give 1,1-difluoro-2-arylthiopropane
3a. Finally, the oxidative fluorination of 3a takes place at
the a-carbon of the sulfur to give 4a. The next step,
Scheme 2.
a
Table 2. Fluorination of alkyl aryl sulfides using IF5
Substrate
IF5/1
Product
Yield (%)b
51
p-MeC6H4SPr 1b
1.2
4b
4c
4d
p-NO2C6H4SPr 1c
p-ClC6H4SEt 1d
4.8
2.4
66c
66
p-ClC6H4SBu 1e
2.4
3.6
70
83
4e
4f
p-ClC6H4SC12H25 1f
p-ClC6H4S(CH2)10SC6H4Cl-p 1g
7.2
4.8
75
4g
71d
4h
4i
1h
p-ClC6H4S(CH2)CONMe2 1i
2.4
3.6
71
71
p-ClC6H4S(CH2)3Ph 1j
4j
a If otherwise not mentioned, the reaction was carried out in heptane under reflux for 1 h.
b Isolated yields based on substrates.
c The reaction was carried out for 24 h.
d The reaction was carried out for 6 h.

S. Ayuba et al. / Tetrahedron 60 (2004) 11445–11451
11447
Scheme 3.
elimination of HF from 4a to a vinylic sulfide 7a, is slow
and 4a can be selectively obtained (Scheme 3).
Then, we investigated the time courses of the reactions at
40 8C in the tight-screw capped vessel to find the reason
why the reaction does not stop at 4a and proceeds to 2a
under the reaction conditions. The yields of 3a increase up
to 1 h and then gradually decrease with an increase in the
yields of 4a. The amount of 4a gradually increases up to 3 h
and then begins to decrease with an increase in the yields of
2a. After 24 h, 2a is almost the sole product and the yields
of 3a and 4a are less than 2%. During the reaction, the
formation of 1,1,2,2-tetrafluoro-3-(p-chlorophenylthio)pro-
pane (8a) is observed but the yield is low (less than 6%)
(Fig. 1). When the reaction is carried out under reflux in
heptane, 3a and 4a are formed as main products in 15 min
The oxidation potentials of 1a, 3a, and 4a were measured by
an electrochemical method to find the reason why the
reaction stopped at 4a (Scheme 4). As expected, the starting
material 1a has low oxidation potential (1.10 V) and,
therefore, the oxidative fluorination step of 1a proceeded
fast under the reaction conditions. 1,1-Difluoro-2-arylthio-
propane 3a, which was isolated as the main product when
the reaction was carried out using 1.2 equiv of IF5 to 1a, has
higher oxidation potential than 1a due to the electron-
withdrawing effect of the difluoromethyl group, and the
oxidative fluorination of 3a to 4a proceeds relatively slowly.
Trifluorinated product 4a has the highest oxidation potential
of 1.65 V which indicates that a lone-paired electron density
on the sulfur is the lowest because of the strong electron-
withdrawing effect of an attached trifluoropropyl group.
Generally, a-fluorosulfides are unstable due to the lone-
paired electrons on the sulfur and a facile elimination of
fluoride takes place to cause their decomposition,8 and
isolation of 1-fluoro-1-arylthiopropane (5a) was unsuccess-
ful. Though 4a is also the a-fluorosulfide, 4a was stable
enough to isolate. As the lone-paired electron density on the
sulfur is low in 4a, the arylthio group did not destabilize 4a.
Consequently, elimination of HF from 4a to the formation
of 7a is slow.
Figure 1. Time dependence of the product distributions in the reaction of
IF5 with 1a at 40 8C in a tight-screw capped vessel (C; 3a, B; 4a, 6; 8a,
!; 2a).
Scheme 4.

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S. Ayuba et al. / Tetrahedron 60 (2004) 11445–11451
examine the possibility, we carried out the reaction at 98 8C
in the tight-screw capped vessel. Under the reaction
conditions, the generated volatile material stays in the
reaction mixture and, therefore, the reaction must proceed to
give 2a. As expected, the reaction is completed in 1 h and 2a
is formed as the main product with a trace amount of 8a
(Fig. 3). The reaction proceeds more quickly than that at
40 8C, and 3a and 4a disappear in 30 min. These results
indicate that volatile material which is necessary to convert
4a to 2a, may be formed during the reaction. When the
reaction is carried out under reflux without tight-screw cap,
it escapes from the reaction mixture and the further
conversion of 4a does not take place. A volatile material
such as HF (bp 19.5 8C) or IF (1.0 8C) is generated during
the reaction. However, we could not identify the material
which actually plays an important role to convert 4a to 2a.
3. Conclusion
We have succeeded in introducing three fluorine atoms into
sulfides selectively by the reaction with IF5 in heptane under
reflux conditions. During the reaction, the migration of the
arylthio group takes place only once.
Figure 2. Time dependence of the product distributions in the reaction of
IF5 with 1a under reflux in heptane (C; 3a, B; 4a, 6; 8a, !; 2a).
and then the yields of 3a decrease with an increase in the
yields of 4a. After 1 h, 3a disappears and 4a becomes the
sole main product. The formation of 2a is observed but
the yield is low (less than 6%) (Fig. 2). These results suggest
that IF5 quickly decomposes at the higher temperature
(98 8C) before 4a changes to 2a. However, such a possibility
is ruled out because an extra addition of IF5 to the reaction
mixture after 1 h does not cause an increase of 2a. Another
possibility is the generation of a volatile material which is
necessary to transform 4a to 2a. When the reaction is carried
out in the tight-screw capped vessel, it stays in the reaction
mixture and the transformation from 4a to 2a proceeds. On
the other hand, it escapes from the reaction mixture under
reflux conditions and the reaction stopps at 4a. In order to
4. Experimental
4.1. General
The IR spectra were recorded using a JASCO FT/IR-410.
1
The H NMR (400 MHz), 19F NMR (376 MHz), and 13C
NMR (100 MHz) spectra were recorded in CDCl3 on a
JEOL JNM-A400II FT NMR and the chemical shift, d, are
referred to TMS (1H, 13C) and CFCl3 (19F), respectively.
The EI-low and high-resolution mass spectra were measured
on a JEOL JMS-700TZ, JMS-FABmate or JMS-HX110. IF5
in a stainless-steel cylinder was supplied by Daikin
Industries, Ltd. IF5 decomposes in air emitting HF fume,
and, therefore, it should be carefully handled in a bench
hood with rubber-gloved hands. Due to its low viscosity and
high density, it is difficult to transfer IF5 from the cylinder to
a reaction vessel with a pipette; therefore, IF5 was used as a
CH2Cl2 solution. From the cylinder, IF5 was transferred
through a Teflone tube into a Teflone FEP bottle under an
N2 atmosphere. After measuring the amount of IF5 in the
bottle, CH2Cl2 was added to make a 16.7 mol% solution. IF5
in CH2Cl2 was kept in the Teflone FEP bottle and
transferred quickly from the bottle to the reaction vessel
using a Teflone pipette in open air. The sulfides other than
1i were prepared from the corresponding aryl mercaptans
and alkyl halides under basic conditions.9 The sulfide 1i was
prepared from p-chlorophenylthiol with N,N-diethylacryl-
amide.10 Et3N-5HF was prepared by the addition of Et3N to
anhydrous HF.11
4.2. Fluorination of sulfides 1 using IF5
4.2.1. General procedure. The reaction was carried out in
an 8 ml-Teflone FEP bottle. IF5 in CH2Cl2 (0.776 g of
16.7 mol% solution, 1.2 mmol), heptane (1 ml) and sub-
strate (0.5 mmol) were introduced into a reaction vessel and
a Teflone tube with a diameter of 10 mm and a length of
Figure 3. Time dependence of the product distributions in the reaction of
IF5 with 1a at 98 8C in a tight-screw capped vessel (C; 3a, B; 4a, 6; 8a,
!; 2a).

S. Ayuba et al. / Tetrahedron 60 (2004) 11445–11451
11449
1000 mm was attached to the top of the bottle. A water-
jacket was attached to the Teflone tube for cooling and the
reaction mixture was stirred under reflux for 1 h. After
consumption of the starting material was confirmed by GC,
the reaction mixture was poured into ice–water and the
product was extracted three times with ether. The combined
ethereal phases were washed with aqueous Na2S2O3,
NaHCO3, and brine, successively and dried over MgSO4.
After concentration under reduced pressure, the product was
isolated by column chromatography (silica gel/hexane–
ether as eluent).
24.8 Hz), 112.11 (ddd, JZ253.5, 248.5, 39.3 Hz), 123.93
(2C, s), 124.17 (s), 136.23 (2C, s), 148.57 (s). MS: 251 (MC,
84), 201 (10), 200 (100), 155 (32), 154 (12), 125 (14), 109
(16), 108 (17), 97 (11), 69 (11). HRMS (EI) Calcd for
C9H8O2NF3S: (MC) 251.0228. Found: 251.0217.
4.2.6. 1,1,2-Trifluoro-2-(p-chlorophenylthio)ethane 4d.
Colorless liquid: IR (neat) 1571, 1477, 1378, 1151, 1095,
1013, 826 cmK1. 1H NMR d 5.67 (ddt, JZ25.2, 9.0, 3.9 Hz,
1H), 5.80 (tt, JZ54.8, 3.7 Hz, 1H), 7.36 (d, JZ8.1 Hz, 2H),
7.51 (d, JZ8.1 Hz, 2H). 19F NMR d K168.00 (ddd, JZ
50.7, 19.2, 3.7 Hz, 1F), K128.76 (dddd, JZ293.0, 54.9,
18.9, 9.8 Hz, 1F), K126.85 (dddd, JZ292.3, 54.3, 23.8,
9.2 Hz, 1F). 13C NMR d 97.63 (dt, JZ226.6, 28.1 Hz),
111.48 (ddd, JZ248.9, 246.5, 34.7 Hz), 127.62 (s), 129.70
(2C, s), 135.32 (2C, s), 136.06 (s). MS: 228 (MCC2, 37),
226 (MC, 100), 177 (33), 175 (90), 143 (47), 108 (29).
HRMS (EI) Calcd for C8H6ClF3S: (MC) 225.9831. Found:
225.9829.
4.2.2. 1,1-Difluoro-2-(p-chlorophenylthio)propane 3a.
Colorless liquid: IR (neat) 1477, 1455, 1390, 1150, 1095,
1051, 1033, 1013, 823 cmK1. 1H NMR d 1.37 (d, JZ7.1 Hz,
3H), 3.24–3.37 (m, 1H), 5.74 (dt, JZ56.6, 3.7 Hz, 1H),
7.30 (d, JZ8.4 Hz, 2H), 7.42 (d, JZ8.4 Hz, 2H). 19F NMR
d K124.56 (ddd, JZ276.0, 56.5, 16.3 Hz, 1F), K118.34
(ddd, JZ276.0, 56.2, 9.8 Hz, 1F). 13C NMR d 13.40 (t, JZ
4.1 Hz), 45.76 (t, JZ21.9 Hz), 116.59 (t, JZ246.0 Hz),
129.25 (2C, s), 131.09 (s), 134.43 (s), 134.68 (2C, s). MS:
224 (MCC2, 25), 222 (MC, 69), 173 (37), 172 (10), 171
(100), 145 (17), 144 (12), 143 (45), 136 (18), 109 (10), 108
(28), 59 (11). HRMS (EI) Calcd for C9H9ClF2S: (MC)
222.0081. Found: 222.0075.
4.2.7. 1,1,2-Trifluoro-2-(p-chlorophenylthio)butane 4e.
Colorless liquid: IR (neat) 1574, 1477, 1389, 1187, 1093,
1
1015, 891, 825 cmK1. H NMR d 1.16 (t, JZ7.6 Hz, 3H),
1.88–2.19 (m, 2H), 5.49 (ddd, JZ56.4, 54.5, 2.3 Hz, 1H),
7.35 (d, JZ8.5 Hz, 2H), 7.53 (d, JZ8.5 Hz, 2H). 19F NMR
d K144.89 to K144.72 (m, 1F), K135.67 (ddd, JZ283.8,
56.5, 14.3 Hz, 1F), K127.94 (ddd, JZ283.8, 53.9, 13.0 Hz,
1F). 13C NMR d 7.49 (d, JZ4.1 Hz), 25.43 (dd, JZ22.3,
2.5 Hz), 104.35 (ddd, JZ226.2, 26.9, 23.2 Hz), 112.44
(ddd, JZ253.9, 247.3, 41.4 Hz), 125.53 (s), 129.43 (2C, s),
136.55 (s), 137.76 (2C, s). MS: 256 (MCC2, 26), 254 (MC,
70), 205 (11), 203 (29), 146 (38), 145 (19), 144 (100), 143
(31), 109 (21), 108 (27). HRMS (EI) Calcd for
C10H10ClF3S: (MC) 254.0144. Found: 254.0160.
4.2.3. 1,1,2-Trifluoro-2-(p-chlorophenylthio)propane 4a.
Colorless liquid: IR (neat) 1574, 1477, 1448, 1389, 1225,
1092, 1015, 938, 852, 825 cmK1. 1H NMR d 1.67 (dm, JZ
19.0 Hz, 3H), 5.50 (ddd, JZ56.6, 54.4, 2.0 Hz, 1H), 7.36
(d, JZ8.5 Hz, 2H), 7.54 (d, JZ8.5 Hz, 2H). 19F NMR d
K135.96 to K135.73 (m, 1F), K135.62 (dddd, JZ283.5,
56.8, 14.6, 1.2 Hz, 1F), K127.88 (dddd, JZ283.5, 54.3,
12.2, 1.2 Hz, 1F). 13C NMR d 18.79 (dd, JZ23.2, 2.5 Hz),
101.83 (dm, JZ221.4 Hz), 112.12 (ddd, JZ253.5, 246.9,
40.5 Hz), 125.53 (s), 129.49 (2C, s), 136.72 (s), 137.71 (2C,
s). MS: 242 (MCC2, 37), 241 (MCC1, 11), 240 (MC,
100), 191 (28), 189 (76), 146 (32), 145 (18), 144 (87), 143
(32), 134 (11), 109 (23), 108 (33). HRMS (EI) Calcd for
C9H8ClF3S: (MC) 239.9987. Found: 239.9980.
4.2.8. 1,1,2-Trifluoro-2-(p-chlorophenylthio)dodecane
4f. Colorless liquid: IR (neat) 2925, 2855, 1574, 1476,
1093, 1015, 824 cmK1. 1H NMR d 0.89 (t, JZ6.8 Hz, 3H),
1.27 (bs, 14H), 1.53–1.63 (m, 2H), 1.83–2.09 (m, 2H), 5.47
(ddd, JZ58.3, 56.4, 2.0 Hz, 1H), 7.35 (d, JZ8.3 Hz, 2H),
7.53 (d, JZ8.3 Hz, 2H). 19F NMR d K143.15 to K142.98
(m, 1F), K135.88 (ddd, JZ282.6, 55.5, 14.0 Hz, 1F),
K127.76 (ddd, JZ283.8, 54.3, 12.2 Hz, 1F). 13C NMR d
14.11 (s), 22.69 (s), 22.93 (d, JZ2.5 Hz), 29.29 (s), 29.32
(s), 29.47 (s), 29.56 (s), 29.65 (s), 31.86–31.91 (m), 32.06
(d, JZ1.7 Hz), 104.06 (ddd, JZ225.8, 27.3, 24.0 Hz),
112.30 (ddd, JZ253.1, 247.3, 41.0 Hz), 125.61 (s), 129.39
(2C, s), 136.52 (s), 137.69 (2C, s). MS: 368 (MCC2, 31),
367 (MCC1, 17), 366 (MC, 81), 146 (37), 145 (13), 144
(100), 143 (12), 57 (12), 43 (18). HRMS (EI) Calcd for
C18H26ClF3S: (MC) 366.1396. Found: 366.1404.
4.2.4. 1,1,2-Trifluoro-2-(p-methylphenylthio)propane 4b.
Colorless liquid: IR (neat) 2993, 1494, 1386, 1096, 1072,
813 cmK1 1H NMR d 1.66 (d, JZ19.0 Hz, 3H), 2.38
.
(s, 3H), 5.34–5.64 (m, 1H), 7.18 (d, JZ8.5 Hz, 2H), 7.48
(d, JZ8.5 Hz, 2H). 19F NMR d K136.58 to –135.53
(m, 2F), K128.56 to K127.60 (m, 1F). 13C NMR d 18.37–
18.76 (m), 21.25 (s), 101.79 (ddd, JZ222.17, 27.9,
23.8 Hz), 112.13 (ddd, JZ253.5, 246.0, 41.4 Hz), 123.36
(s), 129.97 (2C, s), 136.50 (2C, s), 140.38 (s). MS: 221
(MCC1, 12), 220 (MC, 100), 200 (13), 169 (62), 149 (17),
124 (41), 123 (63), 121 (10), 92 (11), 91 (47), 79 (12), 77
(16). HRMS (EI) Calcd for C10H11F3S: (MC) 220.0533.
Found: 220.0526.
4.2.9. 2,9-Bis(p-chlorophenylthio)-1,1,2,9,10,10-hexa-
fluorodecane 4g. Yellow solid: mp 59–62 8C; IR (neat)
2938, 2858, 1745, 1573, 1475, 1092, 825 cmK1. 1H NMR d
0.88–2.13 (m, 12H), 5.46 (ddd, JZ56.4, 54.2, 2.0 Hz, 2H),
7.36 (d, JZ8.5 Hz, 4H), 7.53 (d, JZ8.5 Hz, 4H). 19F NMR
d K143.25 to K143.07 (m, 2F), K136.01 (ddd, JZ282.6,
56.2, 14.6, Hz, 2F), K127.76 (ddd, JZ283.2, 53.7, 12.8 Hz,
2F). 13C NMR d 22.78 (2C, s) 29.25 (2C, s), 31.80 (2C, d,
JZ20.7 Hz), 101.83 (2C, dm, JZ221.4 Hz), 112.12 (2C,
ddd, JZ253.5, 246.9, 40.5 Hz), 125.53 (2C, s), 129.49
(4C, s), 136.72 (2C, s), 137.71 (4C, s). MS: 538 (MCC4,
4.2.5. 1,1,2-Trifluoro-2-(p-nitrophenylthio)propane 4c.
Colorless liquid: IR (neat) 3104, 2996, 1600, 1523, 1347,
1093, 854 cmK1. 1H NMR d 1.74 (d, JZ19.3 Hz, 3H), 5.58
(ddd, JZ56.1, 54.2, 2.4 Hz, 1H), 7.79 (d, JZ8.8 Hz, 2H),
8.23 (d, JZ9.0 Hz, 2H). 19F NMR d K135.97 to K135.74
(m, 1F), K133.53 (ddd, JZ285.0, 55.8, 14.3 Hz, 1F),
K127.29 (ddd, JZ285.0, 54.3, 12.8 Hz, 1F). 13C NMR d
19.29 (d, JZ23.2 Hz), 102.06 (ddd, JZ225.8, 27.3,

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S. Ayuba et al. / Tetrahedron 60 (2004) 11445–11451
16), 537 (MCC3, 17), 536 (MCC2, 68), 535 (MCC1, 24),
534 (MC, 91), 390 (12), 146 (37), 145 (27), 144 (100), 143
(41), 109 (13), 108 (15). HRMS (EI) Calcd for
C22H22Cl2F6S2: (MC) 534.0444. Found: 534.0433.
with a potential scanner (Nichia ES 512A) connected to a
potentio/galvanostat (Nichia NP-100M).
4.3.1. Fluorination of 4a with IF5. Hexane (2 ml), 4a
(0.118 g, 0.5 mmol), and IF5 in CH2Cl2 (0.776 g of
16.7 mol% solution, 1.2 mmol) were introduced into a
reaction vessel made of Teflone FEP with a tight screw cap
and the mixture was stirred at 40 8C for 28 h. After
consumption of the starting material was confirmed by
GC, the reaction mixture was poured into ice–water and the
product was extracted three times with ether. The combined
etheral phases were washed with aqueous Na2S2O3,
NaHCO3, and brine successively and dried over MgSO4.
After concentration under reduced pressure, the product was
isolated by column chlomatography (silica gel/hexane–
ether as eluent).
4.2.10. Methyl 3-(p-chlorophenylthio)-2,2,3-trifluoropro-
panoate 4h. Colorless liquid: IR (neat) 2961, 1785, 1575,
1478, 1442, 1391, 1312, 1220, 1096, 1074, 1014 cmK1. 1H
NMR d 3.95 (s, 3H), 6.00 (ddd, JZ50.0, 12.2, 9.3 Hz, 1H),
7.36 (d, JZ8.5 Hz, 2H), 7.49 (d, JZ8.5 Hz, 2H). 19F NMR
d K167.38 (ddd, JZ50.0, 22.0, 20.1 Hz, 1F), K115.63
(ddd, JZ268.6, 20.1, 12.2 Hz, 1F), K114.27 (ddd, JZ
268.6, 22.0, 9.3 Hz, 1F). 13C NMR d 53.91 (s), 99.23 (ddd,
JZ230.5, 29.7, 27.3 Hz), 111.13 (ddd, JZ259.7, 258.9,
30.6 Hz), 128.47 (s), 129.61 (2C, s), 134.74 (2C, s), 135.85
(s), 161.78 (t, JZ31.0 Hz). MS: 286 (MCC2, 23), 284
(MC, 57), 177 (37), 175 (100), 145 (20), 143 (53), 108 (46).
HRMS (EI) Calcd for C10H8F3O2ClS: (MC) 283.9885.
Found: 283.9880.
4.3.2. 1,2,2,3,3-Pentafluoro-1-(p-chlorophenylthio)pro-
pane 2a. Colorless liquid: IR (neat) 1478, 1391, 1215,
1096, 1013, 829, 744 cmK1. 1H NMR d 5.87 (ddd, JZ66.8,
16.1, 6.1 Hz, 1H), 6.02 (dt, JZ52.7, 6.4 Hz, 1H), 7.37
(d, JZ8.5 Hz, 2H), 7.52 (d, JZ8.5 Hz, 2H). 19F NMR d
K167.19 (ddt, JZ50.7, 18.9, 9.2 Hz, 1F), K140, 65 (dddd,
JZ305.2, 53.1, 8.9, 5.8 Hz, 1F), K137.08 (ddt, JZ304.9,
52.8, 9.5 Hz, 1F), K128.50 (dm, JZ276.5 Hz, 1F),
K125.77 (dm, JZ276.5 Hz, 1F). 13C NMR d 98.60 (ddd,
JZ227.4, 33.1, 25.6 Hz), 108.70 (tm, JZ251.5 Hz), 112.74
(tm, JZ255.4 Hz), 128.35 (s), 129.79 (2C, s), 134.81 (2C,
s), 136.18 (s). MS: 278 (MCC2, 37), 276 (MC, 100), 175
(81), 143 (48), 108 (27). HRMS (EI) Calcd for C9H6ClF5S:
(MC) 275.9799. Found: 275.9797.
4.2.11. N,N-Dimethyl 2-(p-chlorophenylthio)-2,3,3-tri-
fluoropropanamide 4i. White solid: mp 37–39 8C; IR
(KBr) 3056, 2942, 1651, 1476, 1402, 1153, 1085, 1015, 926,
825 cmK1. 1H NMR d 2.81 (s, 3H), 2.85 (d, JZ7.1 Hz, 3H),
6.43 (ddd, JZ54.6, 53.4, 11.0 Hz, 1H), 7.37 (d, JZ8.3 Hz,
2H), 7.56 (d, JZ8.3 Hz, 2H). 19F NMR d K152.70 to
K152.54 (m, 1F), K135.99 (ddd, JZ223.4, 54.9, 17.7 Hz,
1F), K125.32 (ddd, JZ225.2, 53.1, 20.1 Hz, 1F). 13C NMR
d 37.12 (d, JZ15.7 Hz), 37.30 (s), 103.29 (dt, JZ256.4,
22.3 Hz), 113.48 (ddd, JZ254.4, 249.8, 24.0 Hz), 124.69
(s), 129.23 (2C, s), 137.29 (s), 138.14 (2C, s), 162.24 (dd,
JZ20.7, 4.1 Hz). MS: 299 (MCC2, 10), 297 (MC, 27), 72
(100). HRMS (EI) Calcd for C11H11F3ONClS: (MC)
297.0202. Found: 297.0202.
4.3.3. The time course of the reaction of 1a with IF5 at
40 8C in the tight-screw capped vessel. The reaction was
carried out at 40 8C using hexane (2 ml), 1a (0.093 g,
0.5 mmol), and IF5 in CH2Cl2 (0.776 g of 16.7 mol%
solution, 1.2 mmol) in the tight-screw capped vessel as
described in Section 4.3.1 and the yields were obtained by
GC using undecane as an internal standard.
4.2.12. 1,1,2-Trifluoro-2-(p-chlorophenylthio)-3-phenyl-
propane 4j. Colorless liquid: IR (neat) 3033, 2988, 1476,
1092, 1015, 984, 825, 700 cmK1. 1H NMR d 3.17 (ddd, JZ
26.8, 14.9, 2.2 Hz, 1H), 3.44 (t, JZ15.6 Hz, 1H), 5.45 (ddd,
JZ55.9, 54.2, 1.5 Hz, 1H), 7.31–7.47 (m, 7H), 7.49 (d, JZ
8.3 Hz, 2H). 19F NMR d K142.14 to K141.95 (m, 1F),
K135.12 (dddd, JZ283.8, 56.2, 14.3, 1.2 Hz, 1F),
K128.92 (dddd, JZ283.8, 54.3, 12.8, 2.4 Hz, 1F). 13C
NMR d 38.43 (d, JZ20.7 Hz), 103.42 (ddd, JZ228.3,
26.5, 24.0 Hz), 112.11 (ddd, JZ258.1, 248.1, 41.4 Hz),
125.50 (s), 127.67 (s), 128.40 (2C, s), 129.39 (2C, s), 130.82
(2C, s), 132.53 (s), 136.51 (s), 137.64 (2C, s). MS: 318
(MCC2, 38), 317 (MCC1, 18), 316 (MC, 100), 225 (16),
173 (64), 157 (21), 153 (12), 146 (10), 144 (26), 143 (13),
133 (12), 127 (19), 122 (15), 109 (17), 108 (14), 91 (95).
HRMS (EI) Calcd for C15H12ClF3S: (MC) 316.0301.
Found: 316.0300.
4.3.4. The time course of the reaction of 1a with IF5 in
heptane under reflux condition. The reaction was carried
out using heptane (1 ml), 1a (0.093 g, 0.5 mmol), and IF5
in CH2Cl2 (0.776 g of 16.7 mol% solution, 1.2 mmol) as
described in Section 4.2.1 and the yields were obtained by
GC using undecane as an internal standard.
4.3.5. The time course of the reaction of 1a with IF5 at
98 8C in the tight-screw capped vessel. The reaction was
carried out at 98 8C using heptane (2 ml), 1a (0.093 g,
0.5 mmol), and IF5 in CH2Cl2 (0.776 g of 16.7 mol%
solution, 1.2 mmol) in a tight-screw capped vessel as
described in Section 4.3.1 and the yields were obtained by
GC using undecane as an internal standard.
4.3. Oxidation potentials of the sulfides 1a, 3a, and 4a.11
The oxidation potentials of the sulfides 1a, 3a, and 4a
(0.25 mmol) were measured in Et3N-5HF (6 ml) using an
undivided cell (30 ml) made of Teflone PFA, a smooth Pt
wire (1 mm!10 mm) as a working electrode, and a smooth
Pt sheet (20 mm!20 mm) as a counter electrode. The
reference electrode was AgC/AgClNO3 (0.01 M) in MeCN
containing Et4NBF4 (0.1 M). The potential was scanned
Acknowledgements
We are grateful to Daikin Industries, Ltd. for their donation
of IF5.

S. Ayuba et al. / Tetrahedron 60 (2004) 11445–11451
11451
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