Fluoride-induced coupling of perfluoroketene dithioacetals with silyl alkynes: A way towards new polyfunctionalized trifluoromethyl building blocks

Article abstract of DOI:10.1016/j.jfluchem.2007.07.014

Under fluoride activation, the vinyl fluorine of perfluoroketene dithioacetal may be substituted by silylated nucleophiles. Using silyl alkynes, a formal transition metal free sila-Sonogashira cross-coupling reaction occurred. The resulting enynes were hy

Full text of DOI:10.1016/j.jfluchem.2007.07.014

Journal of Fluorine Chemistry 128 (2007) 1300–1305
www.elsevier.com/locate/fluor
Fluoride-induced coupling of perfluoroketene dithioacetals with
silyl alkynes: A way towards new polyfunctionalized
trifluoromethyl building blocks§
1
Tiziano Nocentini, Cedric Brule, Jean-Philippe Bouillon ,
´
Sonia Gouault-Bironneau, Charles Portella
´
*
´ ´ ´
Laboratoire Reactions Selectives et Applications, UMR 6519 CNRS, Universite de Reims Champagne-Ardenne,
´
Faculte des Sciences, BP 1039, 51687 Reims Cedex 2, France
Received 4 May 2007; received in revised form 29 July 2007; accepted 30 July 2007
Available online 6 August 2007
Dedicated to Professor Kenji Uneyama, in honor of his ACS Award for creative work in fluorine chemistry.
Abstract
Under fluoride activation, the vinyl fluorine of perfluoroketene dithioacetal may be substituted by silylated nucleophiles. Using silyl alkynes, a
formal transition metal free sila-Sonogashira cross-coupling reaction occurred. The resulting enynes were hydrolyzed giving new polyfunctional
trifluoromethyl building blocks.
# 2007 Elsevier B.V. All rights reserved.
Keywords: Ketene dithioacetal; Cross-coupling; Sila-Sonogashira; Fluorine substitution; Silyl alkynes; Trifluoromethyl building blocks
1. Introduction
temperature and its decomposition at room temperature leading
to a quantitative conversion of the substrate into the ethoxide
substituted analogue (Scheme 1). A first possibility to
overcome this difficulty was to use enediolates as reagents
[5]. A second one, more efficient, was to use a silylated
precursor of ethyl acetate enolate which, under smooth fluoride
activation and hydrolysis of ketene dithioacetal intermediate,
gave the expected a-trifluoromethyl succinic derivative in high
yield (Scheme 1) [3].
Perfluoroketene dithioacetals 1 [1] are simple and versatile
building blocks. Most of applications we have reported so far
were a consequence of the easy substitution of the vinylic
fluorine atom by an enolate to give, after acid hydrolysis, an a-
trifluoromethyl g-keto thiolester [2] or a-trifluoromethyl
succinic derivatives [3], which can be derivatized towards
various types of trifluoromethyl heterocycles [4], a class of
compounds of great interest. Whereas, conversion of 1 into g-
keto derivatives using potassium ketone enolate works very
well (Scheme 1), similar reaction with potassium or lithium
ethyl acetate enolate failed, the enolate being unreactive at low
This result prompted us to study an extension of this chain
reaction (Scheme 2) to other silyl nucleophiles, using substrate
2 as a model. Even if the reaction concept can be applied to O-
silyl derivatives like silyl ethers and enol silyl ethers [6], the
practical interest of these reagents is limited since the reaction
works very well with alkoxides or ketone enolates. C-silyl
nucleophiles were more attractive because the a priori
required reaction conditions would be much milder than
those using a classical organometallic reagent. We report here
on cross-coupling reactions of the substrate 2 with C-silyl
nucleophiles under fluoride activation, with a special interest
for silyl alkyne reagents, which exhibit interesting reactivity
on acid hydrolysis.
§
Fluorinated ketene dithioacetals. Part 14. For part 13, see Sotoca et al. [E.
Sotoca, J.-P. Bouillon, S. Gil, M. Parra, C. Portella, Tetrahedron 61 (2005)
4395–4402].
* Corresponding author. Tel.: +33 326 913 234; fax: +33 326 913 166.
E-mail address: charles.portella@univ-reims.fr (C. Portella).
´ ´
Current address: Laboratoire ‘‘Sciences et Methodes Separatives’’, EA
1
´
3233, Universite de Rouen, IRCOF, F-76821 Mont Saint Aignan Cedex,
France.
0022-1139/$ – see front matter # 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2007.07.014

T. Nocentini et al. / Journal of Fluorine Chemistry 128 (2007) 1300–1305
1301
could be isolated in moderate yield using TMAF and
acetonitrile (ACN) as solvent (entry 4). Vinyltrimethylsilane
and trimethylsilylcyanide failed to give coupling reaction
(entries 5 and 6).
We then turned our attention to silylalkynes. Transition
metal catalyzed cross coupling of terminal alkynes with aryl or
vinyl halides, the Sonogashira reaction [7], has been extended
to silyl alkynes [8]. Our aim was to perform a sila-Sonogashira
type reaction between silyl alkynes and the fluorovinyl
substrate 2 without transition metal, under simple fluoride
initiation. This type of coupling was exemplified with
polyfluorinated aromatics [9], but was never reported, to our
knowledge, with fluorovinyl derivatives. Functionalized silyl
alkynes bearing an ester or a ketone function failed to give any
modification of the starting material (entries 7 and 8). In
contrast, complete conversion occurred when a mixture of 2
and phenyl(trimethylsilyl)acetylene is activated by a catalytic
amount of TMAF in THF at room temperature, giving the
coupling product 5 in 78% isolated yield (entry 9).
Scheme 1.
2. Results and discussion
Coupling of (trimethylsilyl)acetylene was then attempted.
Surprisingly, using an equimolar mixture of reactants, the only
compound we were able to fully characterize was the 1/2
coupling product 6, isolated in 10% yield. This indicates that
once the ‘‘normal’’ coupling has taken place, fluoride is basic
enough to deprotonate the terminal alkyne moiety, allowing the
chain process to evolve (Scheme 3). Fluoride activation of Pd or
Pd/Cu catalyzed coupling between terminal alkynes and
organic halides has been recently reported [10]. In our case,
the CF3 substituent probably enhances the acidity of terminal
alkyne moiety resulting from the first coupling. When 2 was
reacted with 0.5 equivalent of (trimethylsilyl)acetylene, the
yield of 6 increased to 35%, but the conversion remained
incomplete (70%). This reaction produced a deep-dark
unidentified by-product (vide infra). We assumed that the
reaction could be improved using bis(trimethylsilyl)acetylene
in a 1/2 ratio with 2. The yield of 6 was indeed increased, but to
a moderate extent (44%), for similar reasons.
Reaction of compound 2 with various commercially
available silyl reagents, in the presence of 10% molar
equivalent of tetramethylammonium fluoride (TMAF), gave
variable results (Table 1). Benzyltrimethylsilane reacted
smoothly to give effectively the expected coupling product 3
in 73% isolated yield (entry 1). Reaction with allyltrimethylsi-
lane was more problematic. Depending on the fluoride initiator
and solvent, either no reaction (entries 2 and 3) or partial
conversion was observed. The corresponding allyl product 4
Reactions with both (trimethylsilyl)acetylene and bis(tri-
methylsilyl)acetylene gave, beside the bis(coupling) product 6,
a deep-dark compound X not yet fully characterized [11]. This
compound, obtained after washing the silica gel column with
ether, is highly soluble in this solvent and soluble in hexane.
After high dilution in ether, the color turned to red. For the
moment, it seems to be a highly conjugated oligomeric or
polymeric compound. Further investigations are foreseen for
both characterization of this compound and optimization of the
selectivity of the reaction.
Most often, the condensation product prepared so far by
substitution of the vinylic fluorine of 1 by an enolate was
converted into a thiolester by acid hydrolysis. The new alkyne
derived coupling products reported here exhibit two conjugated
protonation sites, and their acid hydrolysis was not expected to
be a trivial reaction. Indeed, none of the alkyne derivatives 5
and 6 gave, on acid hydrolysis, the product derived from a
simple reaction of the dithioacetal moiety. Compound 5 was
converted into the 1,3-diketo derivative 7 on treatment with hot
trifluoroacetic acid–water 9:3. This transformation is due to a
Scheme 2.

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T. Nocentini et al. / Journal of Fluorine Chemistry 128 (2007) 1300–1305
Table 1
Fluoride activated cross coupling of some C-silyl compounds
Entry
1
R-TMS
Solvent
THF
Initiatora
TMAF
Conversion (%)b
100
Product
Yield (%)c
73
2
3
4
THF
DME
ACN
TMAF
CsF
0
0
–
–
–
–
TMAF
67
38
5
THF
TMAF
0
–
–
6
7
TMSCN
THF
THF
TMAF
TMAF
0d
0
–
–
–
–
8
9
THF
THF
TMAF
TMAF
0
–
–
100
78
a
0.1 equiv.
b
c
d
1 h reaction at room temperature.
Isolated yield.
Partial decomposition (<15%) of starting material occurred on heating with CsF (1.0 equiv.) in DMF or DMSO.
conjugate protonation leading to the delocalized intermediate
cation 8 (Scheme 4). This intermediate traps water selectively
at the b-carbon, leading to the acyl intermediate 9 which is
further hydrolyzed into thiolester 7.
To confirm this mechanism, 5 was reacted with refluxing
anhydrous trifluoroacetic acid. A minor amount of compound
10, corresponding to the trapping of the intermediate 8 by
ethanethiol (probably produced by degradation), was char-
acterized. Finally, reacting 5 in anhydrous trifluoroacetic acid
containing one equivalent of n-hexanethiol gave quantitatively
the corresponding thioenol derivative 11 (Scheme 5).
The acid hydrolysis of the dienyne type compound 6 gave
interesting results. Treatment of 6 during 2 h at 75 8C in a
mixture trifluoroacetic acid–water 9:3 led to a new and
unexpected compound, the thiophene derivative 12, in high
yield (88%). Such a compound can be explained by a similar
first conjugated protonation, with a subsequent intramolecular
trapping of the intermediate 13 by sulfur and then S-
dealkylation (Scheme 6). The resulting compound 14 is further
hydrolyzed into the final substituted 3-trifluoromethyl thio-
phene derivative 12.
Scheme 4.
This reaction path was confirmed in a way similar to the
previous one: using anhydrous trifluoroacetic acid, the reaction
Scheme 3.

T. Nocentini et al. / Journal of Fluorine Chemistry 128 (2007) 1300–1305
1303
Scheme 5.
Scheme 6.
4. Experimental
4.1. General remarks
Scheme 7.
Melting points are uncorrected. FT-IR spectra were recorded
1
stopped at the compound 14 which was isolated in 85% yield.
Its reaction with trifluoroacetic acid–water 9:3 led quantita-
tively to the corresponding thiol ester 12 (Scheme 7).
on a MIDAC Corporation Spectrafile IRTM apparatus. H, 13C
and 19F spectra were recorded on a Bruker AC-250 in CDCl3 as
the solvent. Tetramethylsilane (d = 0.00) or CHCl3 (d = 7.27)
were used as internal standards for 1H and 13C NMR spectra and
CFCl3 for 19F NMR spectra. MS data were obtained on a Trace
MS Thermoquest apparatus (GCMS) at 70 eV in the electron
impact mode. Elemental analyseswere performed with a Perkin–
Elmer CHN 2400 apparatus. All reactions were monitored by
GCMS. Silicagel Merck 9385 (40–63 mm) was used for flash
chromatography. Tetramethylammonium fluoride (TMAF) was
dried for 5 h by heating at 200 8C under reduced pressure. Per-
fluoroketene dithioacetal 2 was prepared according to Ref. [1].
3. Conclusion
C-silyl nucleophiles, more particularly silyl alkynes, react
in very mild conditions with perfluoroketene dithioacetal 2, via
a chain process initiated by tetramethylammonium fluoride.
This reaction can be viewed as a transition metal free sila-
Sonogashira cross-coupling reaction between a silyl alkyne and
a fluorovinyl substrate. The enyne type compounds 5 and 6
undergo an interesting acid hydrolysis pathway via a totally
selective conjugate protonation.
4.2. Typical fluoride activated cross-coupling procedure
The coupling products and their hydrolysis products are
further examples contributing to the versatility of the very
simple building block 2.
To a suspension of anhydrous TMAF (16 mg, 0.1 equiv.) in
dry THF (10 mL) were added perfluoroketene dithioacetal 2

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T. Nocentini et al. / Journal of Fluorine Chemistry 128 (2007) 1300–1305
3
(0.40 g, 1.7 mmol), then benzyltrimethylsilane (0.39 mL,
2.0 mmol). The suspension was stirred for 1 h at room
temperature, under argon atmosphere. The resulting mixture
was washed with brine (8 mL) and the aqueous phase was
extracted twice with ether (2ꢀ 10 mL). The combined organic
phases were dried over MgSO4, filtered and concentrated under
reduced pressure. The crude was purified by silica gel column
chromatography (eluent:petroleum ether/AcOEt (97/3)) to give
the cross-coupling product 3 as an oil (0.38 g; yield: 73%).
CH2S), 3.07 (q, JH,H = 7.4 Hz, 2H, CH2S), 7.3–7.6 (m, 5H,
Ph). 13C NMR: d = 14.8 (CH3CH2S), 14.9 (CH3CH2S), 28.9
3
(CH2S), 30.3 (CH2S), 83.8 (q, JC,F = 3.0 Hz, PhCC), 100.4
2
(PhCC), 116.7 (q, JC,F = 33.7 Hz, CF3C ), 121.2 (q,
1JC,F = 274.9 Hz, CF3), 122.6 (Cq Ph), 128.4 (2ꢀ CH Ph),
3
131.4 (2ꢀ CH Ph), 128.8 (CH Ph), 153.6 (q, JC,F = 2.0 Hz,
(EtS)2C ). 19F NMR: d = ꢁ56.9 (s). Calcd. for C14H17F3S2:
C, 56.94; H, 4.78; S, 20.27; found: C, 57.21; H, 5.09; S,
20.20.
4.2.1. 1,1-Bis(ethylsulfanyl)-3-phenyl-2-
trifluoromethylprop-1-ene (3)
4.2.4. 1,1,6,6-Tetrakis(ethylsulfanyl)-2,5-
bis(trifluoromethyl)-hexa-1,5-dien-3-yne (6)
3
1H NMR: d = 1.25 (t, JH,H = 7.3 Hz, 3H, CH3CH2S), 1.28
It is prepared according to a similar procedure from
TMAF (6 mg, 0.06 mmol), perfluoroketene dithioacetal 2
(0.30 g, 1.3 mmol) and bis(trimethylsilyl)acetylene (0.15 mL,
0.6 mmol). The reaction mixture was stirred for 10 h at room
temperature, under argon atmosphere. After usual work-up, the
crude was purified by silica gel column chromatography
(eluent:petroleum ether/AcOEt (95/5)) to give the starting
compound 2 (78 mg, conversion: 74%) and the desired product
6 as an oil (120 mg, yield: 44%).
(t, 3JH,H = 7.3 Hz, 3H, CH3CH2S), 2.85 (q, 3JH,H = 7.3 Hz, 2H,
3
CH2S), 2.89 (q, JH,H = 7.3 Hz, 2H, CH2S), 4.07 (s, 2H,
PhCH2), 7.1–7.4 (m, 5H, Ph). 13C NMR: d = 14.7 (CH3CH2S),
15.0 (CH3CH2S), 27.9 (CH2S), 28.8 (CH2S), 37.7 (q,
1
3JC,F = 2.0 Hz, PhCH2), 123.3 (q, JC,F = 276.5 Hz, CF3),
126.3 (CH Ph), 127.9 (2ꢀ CH Ph), 128.5 (2ꢀ CH Ph),
2
135.6 (q, JC,F = 27.5 Hz, CF3C ), 138.2 (Cq Ph), 143.8 (q,
3JC,F = 3.0 Hz, (EtS)2C ). 19F NMR: d = ꢁ55.9 (s). IR (film)
n = 3030, 2968, 2928, 1561, 1453, 1300, and 1126 cmꢁ1; MS:
m/z (%) = 306 [M+], 277, 215, 195, 151, 91 (100). Anal. Calcd.
for C14H17F3S2: C, 54.88; H, 5.59; found: C, 55.27; H, 5.49.
3
1H NMR: d = 1.30 (t, JH,H = 7.2 Hz, 6H, CH3CH2S), 1.31
(t, 3JH,H = 7.4 Hz, 6H, CH3CH2S), 2.95 (q, 3JH,H = 7.2 Hz, 4H,
CH2S), 3.03 (q, 3JH,H = 7.4 Hz, 4H, CH2S). 13C NMR: d = 14.8
(CH3CH2S), 14.9 (CH3CH2S), 29.2 (CH2S), 30.4 (CH2S), 94.4
2
4.2.2. 1,1-Bis(ethylsulfanyl)-2-trifluoromethylpenta-1,4-
diene (4)
(Cq acetylenic), 116.1 (q, JC,F = 34.0 Hz, CF3C ), 121.2 (q,
1JC,F = 275.3 Hz, CF3), 155.2 ((EtS)2C ). 19F NMR: d = ꢁ56.8
(s). MS: m/z (%) = 454 (M+, 100), 396, 336. HRMS
(ESI+) Calcd. for C16H21O2F6S4 [M + H] + 455.0430; found:
455.0422.
It is prepared according to a similar procedure from TMAF
(20 mg, 0.21 mmol), perfluoroketene dithioacetal 2 (0.50 g,
2.1 mmol) and allyltrimethylsilane (0.41 mL, 2.6 mmol). The
crude was distilled under reduced pressure using a Bu¨chi
Kugelrohr apparatus to give the starting compound 2 (165 mg,
conversion: 67%) and the desired product 4 as an oil (208 mg,
4.3. Reactions of coupling products with TFA
yield: 38%).
Bp 100–115 8C/10 mbar. 1H NMR: d = 1.24 (t, JH,H
4.3.1. S-Ethyl 3-oxo-4-phenyl-2-
trifluoromethylbutanthioate (7)
3
=
7.3 Hz, CH3CH2S), 1.25 (t, 3JH,H = 7.3 Hz, 3H, CH3CH2S), 2.82
To compound 5 (65 mg, 0.2 mmol) were added trifluor-
oacetic acid (TFA, 153 mL, 2.0 mmol) and water (12 mL,
0.7 mmol). The mixture was heated at 70–75 8C for 2 h. After
cooling at 0 8C, the excess of TFA was neutralized with a
saturated aqueous solution of NaHCO3 (ꢂ1.0 mL). The
aqueous phase was extracted twice with dichloromethane
(2ꢀ 3 mL). The combined organic phases were dried over
MgSO4, filtered and concentrated in vacuo. The crude was
purified by silica gel column chromatography (eluent:petro-
leum ether/AcOEt (95/5)) to give the desired product 7 as an oil
(42 mg, yield: 73%.).
3
3
(q, JH,H = 7.3 Hz, 2H, CH2S), 2.86 (q, JH,H = 7.3 Hz, 2H,
3
CH2S), 3.42 (dm, JH,H = 5.8 Hz, 2H, CH2CH CH2), 5.0–5.1
(m, 2H, CH2CH CH2), 5.7–5.9 (m, 1H, CH2CH CH2). 13C
NMR: d = 14.6 (CH3CH2S), 15.1 (CH3CH2S), 27.6 (CH2S), 28.7
3
(CH2S), 36.0 (q, JC,F = 2.0 Hz, CH2CH CH2), 116.2
1
(CH2CH CH2), 123.2 (q, JC,F = 276.4 Hz, CF3), 133.7
2
(CH2CH CH2), 134.9 (q, JC,F = 26.2 Hz, CF3C ), 142.7 (q,
3JC,F = 3.0 Hz, (EtS)2C ). 19F NMR: d = ꢁ56.7 (s). IR (film):
n = 2980, 2929, 1562, 1298, 1159, 1128 cmꢁ1; MS: m/z
(%) = 257 [M + 1], 227, 195, 165 (100), 139.
3
1H NMR: d = 1.29 (t, JH,H = 7.4 Hz, 3H, CH3CH2S), 2.99
3
(q, JH,H = 7.4 Hz, 2H, CH2S), 3.88 (d, JH,H = 16.0 Hz, 1H,
2
4.2.3. 1,1-Bis(ethylsulfanyl)-4-phenyl-2-
trifluoromethylbut-1-en-3-yne (5)
2
PhCH2), 3.96 (d, JH,H = 16.0 Hz, 1H, PhCH2), 4.52 (q,
It is prepared according to a similar procedure from TMAF
(4 mg, 0.04 mmol), perfluoroketene dithioacetal 2 (0.10 g,
0.4 mmol) and phenyltrimethylsilylacetylene (0.13 mL,
0.6 mmol). The crude was purified by silica gel column
chromatography (eluent:petroleum ether/AcOEt (99/1)) to give
the cross-coupling product 5 as an oil (105 mg, yield: 78%).
3JH,F = 8.0 Hz, 1H, CF3CH), 7.1–7.4 (m, 5H, Ph). 13C NMR:
d = 14.0 (CH3CH2S), 24.7 (CH2S), 49.3 (PhCH2), 67.2 (q,
2JC,F = 26.3 Hz, CF3CH), 121.5 (q, JC,F = 281.5 Hz, CF3),
1
127.8 (CH Ph), 129.0 (CH Ph), 129.7 (CH Ph), 131.7 (Cq Ph),
186.5 (CO), 193.1 (CO). 19F NMR: d = ꢁ64.0 (d,
3JH,F = 8.0 Hz). LC–MS (ESꢁ): m/z (%) = 289 [M ꢁ 1]ꢁ,
243 (100), 227, 217. HRMS (ESI+) Calcd. for C13H13O2F3SNa
[M + Na]+: 313.0486; found: 313.0482.
3
1H NMR: d = 1.33 (t, JH,H = 7.4 Hz, 3H, CH3CH2S), 1.37
(t, 3JH,H = 7.4 Hz, 3H, CH3CH2S), 2.95 (q, 3JH,H = 7.4 Hz, 2H,

T. Nocentini et al. / Journal of Fluorine Chemistry 128 (2007) 1300–1305
1305
4.3.2. 1,1-Bis(ethylsulfanyl)-3-hexylsulfanyl-4-phenyl-2-
trifluoromethylbuta-1,3-diene (11)
then evaporated under reduced pressure and the resulting oil
was purified by silica gel TLC (eluant:petroleum ether) to give
compound 14 as an oil (122 mg, yield: 85%.).
Compound 5 (165 mg, 0.52 mmol) was added to n-
hexanethiol (68 mg, 0.58 mmol) and anhydrous TFA
(2.5 mL). The resulting mixture was stirred for 2 h at room
temperature. TFA was then evaporated under reduced pressure
and the resulting oil was immediately purified by silica gel
column chromatography (eluent:petroleum ether) to give
compound 11 (227 mg, yield: 100%), as a 1:2.6 mixture of
stereoisomers.
1H NMR: d = 1.33 (t, 3JH–H = 7.4 Hz, 3H, CH3CH2S), 1.44
(t, 3JH–H = 7.3 Hz, 3H, CH3CH2S), 1.46 (t, 3JH–H = 7.3 Hz, 3H,
3
CH3CH2S), 2.92 (q, JH–H = 7.3 Hz, 2H, CH2S), 3.04 (q, JH–
3
3
H = 7.3 Hz, 2H, CH2S), 3.08 (q, JH–H = 7.3 Hz, 2H, CH2S),
7.09 (1H, s, CH thiophene). 13C NMR: d = 14.3 (CH3CH2S),
14.7 (CH3CH2S), 14.8 (CH3CH2S), 28.7 (CH2S), 29.8 (CH2S),
`
1
32.3 (CH2S), 121.7 (q, JC,F = 274.0 Hz, CF3), 121.9 (q,
1
3
2
Major isomer: H NMR: d = 0.8–0.9 (m, 3H), 1.10 (t, JH–
3
H = 7.5 Hz, 3H, CH3CH2S), 1.19 (t, JH–H = 7.5 Hz, 3H,
1JC,F = 270.0 Hz, CF3), 125.4 (q, JC,F = 32.0 Hz, CF3C ),
2
128.6 (CH), 131.2 (q, JC,F = 34.0 Hz, CF3C ), 136.9 (Cq),
CH3CH2S), 1.1–1.3 (m, 8H, 4ꢀ CH2), 2.5–3.0 (m, 6H, 3ꢀ
CH2), 6.73 (s, 1H, PhCH ), 7.1–7.3 (m, 5H, Ph). 13C NMR:
d = 14.5 (CH3), 15.4 (CH3), 15.7 (CH3), 23.0 (CH2), 28.4
(CH2), 29.1 (CH2), 29.8 (CH2), 31.8 (CH2), 31.9 (CH2), 32.9
140.3 (Cq), 152.6 (Cq). 19F NMR: d = ꢁ58.1 (s), ꢁ55.7 (s). MS:
m/z (%) = 426, 367 (100), 338.
Acknowledgements
1
(CH2), 122.5 (q, JC,F = 274.0 Hz, CF3), 127.9 (2ꢀ CH Ph),
128.3 (2ꢀ CH Ph), 128.8 (CH Ph), 129.9 (Cq), 132.0 (Cq),
132.6 (Cq), 136.1 (PhCH), 147.2 (Cq). 19F NMR: d = ꢁ55.0 (s).
Anal Calcd. for C21H29F3S3: C, 58.03; H, 6.73; found: C, 57.94;
H, 6.94.
We gratefully acknowledge CEREP company, ANRT, CNRS,
Region Champagne-Ardenne and the European Commission
for financial support.
´
1
Minor isomer: Selected data: H NMR: d = 6.39 (s, 1H,
PhCH ). 19F NMR: d = ꢁ55.9 (s).
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chromatography (eluent:petroleum ether/AcOEt (95/5)) to give
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´
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3
1H NMR: d = 1.30 (t, JH,H = 7.4 Hz, 3H, CH3CH2S), 1.35
(t, 3JH,H = 7.4 Hz, 3H, CH3CH2S), 2.99 (q, 3JH,H = 7.4 Hz, 2H,
[4] C. Portella, J.-P. Bouillon, in: V.A. Soloshonok (Ed.), Fluorine-Containing
Synthons, Oxford University Press/American Chemical Society, Washing-
ton, DC, 2005 , pp. 232–247 (Chapter 12).
3
CH2S), 3.00 (q, JH,H = 7.4 Hz, 2H, CH2S), 4.65 (q,
3JH,F = 8.0 Hz, 1H, CF3CH), 7.22 (s, 1H, H-40). 13C NMR:
d = 14.0 (CH3CH2S), 14.3 (CH3CH2S), 24.7 (CH2S), 32.2
[5] E. Sotoca, J.-P. Bouillon, S. Gil, M. Parra, C. Portella, Tetrahedron 61
(2005) 4395–4402.
2
(CH2S), 57.4 (q, JC,F = 29.4 Hz, CF3CH), 121.7 (q,
1
1JC,F = 271.8 Hz, CF3), 122.3 (q, JC,F = 282.1 Hz, CF3),
[6] We have checked the feasibility of the reaction with allyloxytrimethylsi-
´
lane and the acetophenone derived enoxytrimethylsilane: C. Brule, PhD
3
128.4 (q, JC,F = 2.7 Hz, CH), 130.3 (Cq), 131.2 (q,
Dissertation, Reims Champagne-Ardenne University, 2004.
[7] (a) R. Chinchilla, C. Najera, Chem. Rev. 107 (2007) 874–922;
(b) H. Doucet, J.-C. Hierso, Angew. Chem. Int. Ed. 46 (2007) 834–871.
[8] Y. Nishihara, K. Ikegashira, A. Mori, T. Hiyama, Chem. Lett. 12 (1997)
1233–1234.
3
2JC,F = 34.1 Hz, CF3C ), 141.7 (q, JC,F = 2.1 Hz, Cq), 190.0
3
(CO). 19F NMR: d = ꢁ67.8 (d, JH,F = 8.0 Hz, 3F, CF3CH),
ꢁ58.4 (s, 3F, CF3C ). IR (film): n = 2972, 2932, 1683, 1450,
and 1126 cmꢁ1; LC–MS (ESꢁ): m/z (%) = 381 [M ꢁ 1]ꢁ (100).
HRMS (ESIꢁ) Calcd. for C12H12F6OS3–H+: 380.9876; found:
380.9887.
[9] (a) G.A. Artamkina, S.V. Kovalenko, I.P. Beletskaya, O.A. Reutov,
Russian J. Org. Chem. 26 (1990) 225–229;
(b) S.V. Kovalenko, I.V. Alabugin, Chem. Commun. (2005) 1444–1446.
[10] (a) M.S.M. Ahmed, A. Sekiguchi, T. Shimada, J. Kawashima, A. Mori,
Bull. Chem. Soc. Jpn. 78 (2005) 327–330;
4.3.4. 5-(1,1-Bis(ethylsulfanyl)-3,3,3-trifluoroprop-1-en-2-
yl)-2-(ethylsulfanyl)-3-(trifluoromethyl) thiophene (14)
Compound 6 (155 mg, 0.34 mmol) was added to anhydrous
TFA (2.5 mL) under nitrogen and the resulting mixture was
stirred overnight at room temperature. The excess of TFA was
(b) A. Mori, T. Shimada, T. Kondo, A. Sekiguchi, Synlett (2001) 649–
651.
[11] NMR data of unidentified by-product X: 1H NMR: d = 1.0–1.6 (brs), 2.6–
3.6 (brs). 13C NMR: d = 14.5–15.5 (brs), 29.5–30.5 (brs). 19F NMR:
d = ꢁ56.4 to ꢁ57.0 (brs).