Thiophilic nucleophilic trifluoromethylation of α-substituted dithioesters. Access to S-trifluoromethyl ketene dithioacetals and their reactivity with electrophilic species

Article abstract of DOI:10.1016/j.jfluchem.2011.02.016

The nucleophilic trifluoromethylation of dithioesters bearing a nucleofugal group in α-position, using CF₃TMS under fluoride activation, afforded unprecedented S-CF₃ ketene dithioacetals via a domino process thiophilic trifluoromethylation-β-elimination. The best results were obtained with non-enolisable α-carbamoyloxydithioesters. The higher homologues S-C₂F₅ ketene dithioacetals were prepared by a similar way. These new dithioacetals react with methylating reagents quantitatively and chemoselectively at sulfur to give stable dimethylsulfonium type salts. They react more classically with triflic acid, protonation taking place at the β-carbon to give a dithiolium salt, characterized in solution but non-isolable.

Full text of DOI:10.1016/j.jfluchem.2011.02.016

Journal of Fluorine Chemistry 134 (2012) 164–171
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Thiophilic nucleophilic trifluoromethylation of
a
Access to S-trifluoromethyl ketene dithioacetals and their reactivity with
electrophilic species
-substituted dithioesters.
1
2
*
Sonia Gouault-Bironneau , Vadim M. Timoshenko , Fabienne Grellepois, Charles Portella
Institut de Chimie Mole´culaire de Reims, Universite´ de Reims-Champagne-Ardenne – CNRS (UMR 6229), UFR Sciences, BP 1039, 51687 REIMS Cedex 2, France
A R T I C L E I N F O
A B S T R A C T
Article history:
The nucleophilic trifluoromethylation of dithioesters bearing a nucleofugal group in
a-position, using
Received 11 January 2011
Received in revised form 9 February 2011
Accepted 27 February 2011
Available online 15 March 2011
CF3TMS under fluoride activation, afforded unprecedented S-CF3 ketene dithioacetals via a domino
process thiophilic trifluoromethylation– -elimination. The best results were obtained with non-
enolisable -carbamoyloxydithioesters. The higher homologues S-C2F5 ketene dithioacetals were
b
a
prepared by a similar way. These new dithioacetals react with methylating reagents quantitatively and
chemoselectively at sulfur to give stable dimethylsulfonium type salts. They react more classically with
Keywords:
triflic acid, protonation taking place at the
but non-isolable.
b
-carbon to give a dithiolium salt, characterized in solution
Fluorine
Sulfur
ß 2011 Elsevier B.V. All rights reserved.
Trifluoromethylation
Dithioesters
Thiophilic addition
Ketene dithioacetals
Research topic
C-glycosides, vic-F,RF-heterocycles, difluoromethyl deriva-
tives.
Fluorine Chemistry at the university of Reims
(ii) F & S. Taking advantage of the versatility of sulfur (various
oxidation states, low polarizability. . .). Key BBs in this field:
perfluoroketene dithioacetals and perfluorodithiocarboxylic
acid derivatives. Main applications: synthesis of a wide
The group from Reims became involved in fluorine chemistry
around 1985. Our interest was focused on methodologies in
organofluorine chemistry, sometimes turned towards specific
applications in the framework of cooperation with industrial
companies (building blocks (BB) of pharmaceutical interest,
surfactants). The main research topics have been:
variety of trifluoromethylated heterocycles via
thiolesters, -RF-succinic derivatives. . .
g-keto-a-RF-
a
-
-
Perfluoroalkylation
Radical and nucleophilic F-alkylation using RFI and RFTMS were
used for well defined applications: synthesis of highly fluorinated
compounds, of C-trifluoromethylated sugars or more generally of
multifunctionalized fluorinated derivatives.
-
Fluorine associated with other heteroelements
(i) F & Si. Taking advantage of the high reciprocal affinity of these
two elements to develop new multistep one pot transforma-
tions, in particular from reaction of acylsilanes and organo-
metallic reagents (RFLi, RFMgI, RFSiMe3). Key BBs in this field:
perfluoroenoxysilanes, which are both nucleophilic and
electrophilic. Applications: gem-difluoro terpenes, difluoro-
Quaternary CF3-containing BBs
(i) Synthesis of enantiopure trifluoromethylated BBs from
tartaric acid based substrates.
(ii) Development of new CF3-cyclopentane difunctionalized BBs.
* Corresponding author. Tel.: +33 326 913234; fax: +33 326 913166.
1. Introduction
E-mail address: charles.portella@univ-reims.fr (C. Portella).
1
´
Current address: Innov’orga, Faculte des Sciences, Moulin de la Housse, BP 1039,
Due to the high polarizability of sulfur, sulfur containing
organic compounds exhibit a versatile chemistry. Thus both
carbophilic and thiophilic addition can be observed on thiocarbo-
51687 Reims Cedex 2, France.
2
Permanent address: Institute of Organic Chemistry, NAS of Ukraine, Mur-
manska Str. 5, 02660 Kyiv, Ukraine.
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.02.016

S. Gouault-Bironneau et al. / Journal of Fluorine Chemistry 134 (2012) 164–171
165
S
X
RF
F
SR'
S
R'M
RF-CF2
1) LDA, THF, - 20 °C
Ph
SMe
OCO2Et
Et2O
X = SR, NR2
X
2) CS2, - 20 °C
BnO
OEt
3) MeI, - 20 °C to rt
Scheme 1. S-alkylation of perfluorodithioacid derivatives.
4) H2O
O
3
Ph
EtO2C
CS2Me
OH
nyl compounds as well as on dithiocarboxylic derivatives [1]. The
strong withdrawing character of fluorine allows perfluorothio-
carboxylic derivatives to react selectively with organometallics at
4 (48 %)
LDA
OEt
sulfur, with subsequent fluoride
b-elimination. We have thus
Ph
Li+
O
O
developed a closely related chemistry of perfluoroketene dithioa-
cetals and perfluorodithioesters or, more generally, perfluorothio-
carboxylic derivatives (Scheme 1) [2]. These studies were focused
on the addition of non-fluorinated reagents on fluorinated
substrates [3]. More recently we reported that nucleophilic
trifluoromethylation of perfluorodithioesters occurs also at sulfur
as the first step of a domino process where the corresponding S-CF3
perfluoroketene dithioacetal is the first intermediate [4].
Ph CS2Li
EtO2C OLi
O
CS2
Ph
LiO
Ph
OLi
Ph
LDA
OEt
O-Li+
CO2Et
LiO
OEt
To complete these studies we have investigated the behavior of
non-fluorinated substrates bearing in
group under nucleophilic trifluoromethylation conditions with the
expectation that a similar sequence S-addition– -elimination
a-position a nucleofugal
Scheme 4. Synthesis of dithioester 4 via a rearrangement of a lithiated carbonate.
b
to a similar reaction sequence, giving the unexpected rearranged
dithioester 4, the structure of which was confirmed by X-Ray
diffraction analysis [6] (Scheme 4 and Fig. 1).
would give an unprecedented S-CF3 ketene dithioacetal (Scheme
2). The properties of such a new intermediate of course would
deserve to be explored. We report herein the results of this study.
Compound 4 is the result of a Chan type rearrangement [7]
occurring at the intermediate carbanion stage, followed by a
second deprotonation prior to reaction with carbon disulfide
(Scheme 4). Such a rearrangement, discovered with acyloxyace-
tates, was reported later from carbonate derivatives [8]. This
transformation required two equivalents of LDA, which is
consistent with such a mechanism. The selectivity in the final
methylation at sulfur is coherent in terms of HSAB correlation.
To avoid this rearrangement, we decided to synthesize a
carbamate derivative (Scheme 5). Starting from benzylcarbamate
5, the desired carbamate 6 was obtained in a poor yield using LDA
as a base. Changing LDA for sec-butyl lithium/TMEDA [9] afforded,
from a complex reaction mixture, the dithioketene 7, indicating
that the deprotonation and further transformation of 6 is the
limiting factor of this synthesis. To circumvent this side reaction,
2. Results and discussion
2.1. Preconditions
Regarding the model substrates for this study, we have chosen
a
-phenyl dithioacetic esters type derivatives, considering that a
phenyl substituent would stabilize the postulated ketene dithioa-
cetal and possible further intermediates for reactivity study.
Trifluoromethyl(trimethyl)silane (TFMTMS), already assessed as a
thiophilic reagent on perfluorodithioesters [4] and widely used in
this laboratory, was systematically used for nucleophilic trifluor-
omethylation experiments. Extension to pentafluoroethyl(tri-
methyl)silane (PFETMS) was also considered. The leaving group
should have the property to favor the chain transfer in a reaction
performed under nucleophilic initiation.
we turned to a-alkyl substituted compounds. 1-Phenylethyl and 1-
phenylpropyl dimethylcarbamates 8a,b were easily prepared. They
were deprotonated according to conditions previously described
[10] and converted in high yields into the desired dithioesters 9a,b
(Scheme 6). The latter were obtained in high purity after the simple
filtration of their dichloromethane solution through a pad of
silicagel and solvent removal.
2.2. Synthesis of substrates
In a first approach,
a-t-butyl(dimethyl)silyl (TBDMS) dithioe-
ster 2 was prepared from silyl ether 1, with a good yield of 86%
(Scheme 3).3 Ethoxycarbonyloxyl group was a second possible
leaving group, since the corresponding ethoxide resulting from its
decarboxylation would constitute an excellent transfer reagent to
activate TFMTMS. The corresponding carbonate 3 was submitted
R1
R2
LG
S
R1
R2
SCF3
SR
CF3TMS
SR
Scheme 2. Purpose: S-trifluoromethylation of
a-substituted dithioesters.
1) nBuli / TMEDA
THF
Ph
CS2Me
OTBDMS
2 (86 %)
-20 °C to -5 °C
Ph
OTBDMS
2) CS2
3) MeI, rt
1
Scheme 3. Synthesis of
a
-t-butyl(dimethyl)silyloxy dithioester 2.
Fig. 1. Structure of 4 from X-ray analysis.

166
S. Gouault-Bironneau et al. / Journal of Fluorine Chemistry 134 (2012) 164–171
4
1) LDA, THF, -20°C
2) CS2, -20°C
3) MeI, -20°C to rt
S
Ph
TMSO-
SMe
TMSOH
Me2N
O
F-
6 (35%)
O
HF
Ph
O
NMe2
S
Ph
4
O
SMe
5
O-
EtO2C
1. s-BuLi/TMEDA
Ph
SMe
SMe
THF, -78°C
SMe
S
2. CS2
3. MeI, -78°C to rt
Ph
EtO2C
Me2NOC O
7 (17%)
-
CF3TMS
O
CF3
Si
13
Scheme 5. Synthesis of
a-carbamoyloxy dithioester 6.
Scheme 9. Proposed chain mechanism for S-trifluoromethylation of 4.
1. s-BuLi/TMEDA
THF, -78°C
2. CS2
Ph
CS2Me
Ph
R
on the stoichiometry of TMAF, but a catalytic amount of TMAF
(0.1 equiv.) is enough for a complete conversion of the substrate,
giving the expected ketene dithioacetal 11 (two diastereomers)
and the compound 12 which corresponds to the silyl ether of the
substrate. The selectivity towards 11 was improved when the
reaction was activated with 0.5 equiv. of TMAF, but it could not be
separated from an unidentified trifluromethylated by-product
OCONMe2
3. MeI, -78°C to rt
OCONMe2
R
8a: R = Me
8b: R = Et
9a: R = Me 81%
9b: R = Et 91%
Scheme 6. Synthesis of
a-alkyl-a-carbamoyloxy dithioesters 9.
exhibiting
a
CF3 signal at À60.8 ppm. The transformation
-elimination subsequent
corresponds formally to an hydroxide
b
to the thiophilic trifluoromethylation, but the initiation of the
reaction proceeds probably by a prior deprotonation of 4, the
resulting alkoxide being the actual anionic activator of TFMTMS.
The TFM transfer possibly occurs via an intramolecular way
through intermediate 13 (Scheme 9).
S
SCF3
SMe
CF3SiMe3 (1.2 equiv)
Ph
SMe
Ph
TMAF (1.5 equiv)
THF
OTBDMS
-20 °C to rt
As observed for their preparation, the reactivity of carbamate
10 (traces: -39 ppm)
2
derivatives depends on the degree of substitution of the
a carbon.
Scheme 7. Reaction of
a-t-butyl(dimethyl)silyl dithioester 2 with CF3TMS.
Reaction of 6 with TFMTMS led to partial conversion and a complex
mixture, using either TMAF or CsF as initiator, and THF or
dimethoxyethane (DME) as solvent. At the best, a small signal at
À39 ppm disclosed the possible presence of traces of the S-CF3
ketene dithioacetal when the reaction was performed at À20 8C. In
contrast clean and total conversion of compounds 9 containing a
2.3. S-perfluoroalkylation of dithioesters
We have now a variety of dithioesters bearing a leaving group in
position to submit them to nucleophilic trifluoromethylation
(pefluoroalkylation) conditions. As mentioned above, TFMTMS was
a reagent of choice for such a purpose, as was pentafluoroethyl(-
trimethyl)silane (PFETMS) for an extension to the higher homo-
logue.
a
quaternary
a carbon was observed under CsF activation in DME,
and the corresponding ketene dithioacetals 14 were isolated in
high yields (Scheme 10). The efficiency of the reaction prompted us
to extend it to PFETMS reagent. Indeed the S-C2F5 ketene
dithioacetals 15 were isolated in high yields (Scheme 10).
The
a-OTBDMS dithioester 2 was treated in THF with TFMTMS
Compounds 14 and 15 were isolated as
a mixture of
and tetramethylammonium fluoride (TMAF) as initiator. No
reaction was observed when using a catalytic amount (0.1 equiv.)
of TMAF. With an excess of TMAF (1.5 equiv.), a complex reaction
took place with total conversion of 2. A weak signal at À39 ppm in
the 19F NMR spectrum of the complex crude mixture indicates the
presence of an S-CF3 moiety, thus probably of traces of the
expected ketene dithioacetal 10 (Scheme 7). We assume that TMAF
acts also as a base which can deprotonate the substrate and lead to
its degradation.
diastereomers which, in spite of their very low polarity, could
be separated by flash chromatography using petroleum ether as
eluent. E configuration was assigned to the major isomer of 15a by
NOESY analysis (Fig. 2). The 1H NMR spectrum of this major isomer
exhibits SMe protons at higher field (2.2 vs 2.4 ppm), which allows
to determine the E/Z ratio for the set of analogues.
The reaction of the dithiomalonic derivative 4 under the same
conditions is more interesting (Scheme 8). The results also depend
S
R
SRF
RFTMS / CsF
Ph
SMe
DME
R
Ph
SMe
OCONMe2
9a,b
rt, 24 h
SCF3
SMe
CO2Et
S
S
CF3SiMe3 (1.1 equiv)
Ph
EtO2C
Ph
Ph
+
SMe
RF
R
Product
14a
%Yied (E/Z)
79 (82/18)
91 (87/13)
SMe
TMAF (x equiv)
THF
EtO2C
OH
OTMS
CF3
Me
Et
-20 °C to rt
CF3
14b
4
11
12
C2F5
C2F5
15a
15b
83 (86/14)
90 (88/12)
Me
Et
x = 0.1
x = 0.5
23 %
~ 60 %
33 %
0 %
Scheme 8. Reaction of
a-hydroxy dithioester 4 with CF3TMS.
Scheme 10. Reaction of a-carbamoyloxy dithioesters 9 with CF3TMS or C2F5TMS.

S. Gouault-Bironneau et al. / Journal of Fluorine Chemistry 134 (2012) 164–171
167
NOE
F3CS
Ph
-
+ BF4
S
Ph
SCF3
SMe
-
Me3O+ BF4
DCM, Δ
99%
1.46%
Me
SCF2CF3
SMe
EtO2C
H
CO2Et
16
11
SCF3
H
NOE
Me
F3CS
Et
Et
S+ TfO-
Me
1.19%
TfOMe
C6H6, rt
99%
Fig. 2. NOE measurement on compound 15a (major isomer).
Ph
SMe
14b
Ph
17
R
SCF3
+
E
Scheme 12. Methylation of ketene dithioacetal 11 and 14b.
Ph
SMe
E+
R
SCF3
SMe
?
compound 11 was treated with methyl triflate. The salt 16 proved
to be stable and no rearrangement was observed even after heating
in acetonitrile. Similarly, compound (E)-14b was converted
quantitatively into the corresponding dimethylsulfonium salt 17
on reaction with methyl triflate (Scheme 12). Thus the reaction is
Ph
R
SCF3
Ph
S Me
+
E
totally chemoselective, S-methylation being preferred to
b-C-
Fig. 3. Possible reactions of S-CF3 ketene dithioacetals with electrophiles.
methylation. As for the exclusive formation of the dimethylsulfo-
nium salts, this selectivity is less surprising because of the weak
nucleophilicity of the S-CF3 moiety.
In contrast to methylation reaction, reaction of 14b with triflic
acid led to the b-protonated salt 18 (Scheme 13). This salt is stable
This reaction worked effectively with less than 20 mol% of CsF,
confirming the role of the latter as initiator of a chain reaction
where the carbamoyloxy group proved to be an excellent chain
transfer agent. However, it is difficult to discriminate the actual
chain transfer agent between the carbamoyloxy group itself or
the dimethylamide moiety resulting from decarboxylation
(Scheme 11).
enough in DCM or chloroform solution but could not be isolated. Its
structure was confirmed by NMR analysis. After the addition of 3
equivalents of triflic acid to a CDCl3 solution of 14b, the signals of
the starting compound disappeared and a double set of new signals
was observed. The NMR spectra exhibit the same set of signals for
reaction of the pure isomer (E)-14b or of the mixture of
stereoisomers. The 19F NMR spectrum displays two singlets of S-
CF3 groups at À35.7 and À40.0 ppm in a 55:45 ratio. This ratio is
confirmed in the 1H NMR spectrum for (i) signals corresponding to
the quaternary proton, which appeared as two doublets of doublets
in the 4.9 ppm region (coupling with non-equivalent CH2 protons);
(ii) for SMe (two singlets at 3.5 and 3.3 ppm). The cationic
character of the dithiolium moiety is confirmed by a signal at
247 ppm in the 13C NMR spectrum. The double set of signals
observed may be explained by a geometric type isomerism, with
two major configurations among the four ones presented in
Scheme 13.
Compound 14b was recovered after treatment with trifluor-
oacetic acid. The same is true of its treatment with trifluoroacetic
anhydride and triflic anhydride. This inertness could be actually
due to an equilibrium in favor of the reversed reaction.
The salt 18 can be considered itself as a super acid as it gave
back its proton to compounds as weakly basic as phenol,
tolylmercaptan, triphenylphosphine or ethyl acetoacetate. The
ketene dithioacetal 14b was recovered, as a 1:1 mixture of E,Z-
isomers, on the addition of any of these compounds to a chloroform
solution of 18. The addition of water to 18 affords the thiol ester 19
and the corresponding acid 20, the expected products of acid
2.4. Reaction of S-CF3 ketene dithioacetals with some electrophiles
This new type of ketene dithioacetal bearing an S-CF3 moiety
seemed to us of great interest, in particular regarding their
nucleophilic behavior towards protonation or reaction with carbon
electrophiles (Fig. 3). The presence of the TFM group on sulfur
might change significantly the chemoselectivity. Indeed, the usual
electrophilic attack on
b carbon favored by sulfur stabilizing the
resulting carbocation might be prevented by the presence of the
strong withdrawing character of TFM. On the other hand reaction
at
b carbon would give a dithiolium salt which could be a source of
electrophilic TFM, thus would represent a new system to reverse
the polarity of TFMTMS [11].
Treatment of the dithioacetal 11 with triflic acid led to an
intractable mixture. Compound 11 did not react with dimethyl-
sulfate, but gave stable salt when treated in dichloromethane with
trimethyloxonium tetrafluoroborate. Methylation occurred exclu-
sively at sulfur to give quantitatively the dimethylsulfonium salt
derivative 16 (Scheme 12). A similar reaction took place when
-
CO2
Me2N
CF3TMS
Y= Me2N or Me2NCO2
Et
Ph
Et
SCF3
SMe
S CF3
TfO-
S Me
18
TfOH
CDCl3
+
-
-
[Y(Me3Si)CF3]
Me2NCO2
Ph
H
100% conv.
14b
Ph
R
SCF3
SMe
Ph
S
F3C
R
Ph
SCF3
-
SMe
F3C
Et
Ph
H
S CF3
+
Et
Ph
H
S CF3
+
Et
Ph
H
Me2NCO2
SMe
R
S
Et
Ph
S
+
Me2NCO2
+
S
Me3SiY
S Me
S
Me
H
S Me
Me
Scheme 11. Proposed chain mechanism for S-trifluoromethylation of
a-
carbamoyloxydithioesters.
Scheme 13. Reaction of the ketene dithioacetal 14b with triflic acid.

168
S. Gouault-Bironneau et al. / Journal of Fluorine Chemistry 134 (2012) 164–171
GC–MS 70 eV, m/z (rel. int.): 207 [M+] (1), 118 [MÀMe2NCO2H]
Et
Ph
Et
H3O+
O
O
H2O
+
18
14b
Ph
(74), 117 (100), 115 (50), 91 (60).
H
SMe
H
OH
4.3. Methyl 2-t-butyl(dimethylsilyl)-2-phenyethaneldithioate (2)
19 (38%)
20 (30%)
Scheme 14. Hydrolysis of ketene dithioacetal 14b.
To a solution of silylether 1 (1 g, 4.5 mmol) in THF (15 mL) were
added successively, at À20 8C and under Ar, TMEDA (2.04 mL,
13.5 mmol, 3 equiv.) and n-BuLi (1.8 M in hexanes, 7.5 mL,
13.5 mmol, 3 equiv.). After 4 h of stirring from À20 8C to À5 8C,
CS2 (1.35 mL, 22.5 mmol, 5 equiv.) was added. After 1 h 45 min of
stirring from À5 8C to 0 8C, MeI (1.4 mL, 22.5 mmol, 5 equiv.) was
added and the stirring was continued for 15 h at rt. The reaction
was then diluted with ether and quenched with sat. aq. NH4Cl. The
ethereal layer was extracted, washed successively with H2O and
brine, dried (MgSO4) and the solvent was evaporated. The residue
was purified by chromatography on SiO2 (PE) to afford 2 (1.2 g,
hydrolysis of the ketene dithioacetal 14b resulting from proton
transfer to water (Scheme 14).
3. Conclusion
We have described the reactions of
with TFMTMS under fluoride activation.
thiophilic trifluoromethylation– -elimination afforded new S-
a-substituted dithioesters
A
domino process
b
86%) as a solid. 1H NMR (CDCl3):
d 7.35–7.10 (5H, m, Ph), 6.65 (1H,
CF3 ketene dithioacetals via a chain mechanism. The best results
were obtained with a carbamoyloxy leaving group and substrates
s, CH-CS2), 2.58 (3H, s, SCH3), 0.94 (9H, s, C(CH3)3), 0.11 (3H, s,
SiCH3), À0.11 (3H, s, SiCH3). 13C NMR (CDCl3):
d 216.1 (CS2), 139.4
non-bearing hydrogen in
a-position. The transformation worked
(C ipso), 128.4 (2 CH arom), 126.5 (CH para), 126.2 (2 CH arom),
79.7 (CH–O), 26.9 (C(CH3)3), 19.3 (SCH3), 17.1 (C(CH3)3), À7.1
(SiCH3), À8.4 (SiCH3). Anal. calcd for C15H25OS2Si: C, 57.64; H, 7.74.
Found: C, 57.72; H, 7.73.
with PFETMS as well. These dithioacetals react quantitatively with
methylating reagents exclusively at sulfur to give stable dimethyl-
sulfonium type salts. Their chemoselectivity is more classical with
triflic acid, protonation taking place at
b-carbon to give a
dithiolium salt, well characterized in solution but non-isolable.
4.4. Methyl 2-hydroxy-2-ethoxycarbonyl-2-phenylethanedithioate
(4)
4. Experimental
To
a solution of diisopropylamine (2.34 mL, 16.66 mmol,
4.1. General remarks
2 equiv.) in THF (30 mL) was added dropwise, at À20 8C and
under Ar, n-BuLi (2.5 M in hexanes, 6.7 mL, 16.66 mmol, 2 equiv.).
After 20 min of stirring at this temperature, the carbonate 3 (1.5 g,
8.33 mmol) was added to the reaction mixture followed by CS2
(1 mL, 3.18 mmol, 1.1 equiv.) after 20 min of supplementary
stirring. After 1 h of supplementary stirring from À20 8C to
À5 8C, MeI (1.04 mL, 16.66 mmol, 2 equiv.) was added and the
stirring was continued for 4 h at rt. The reaction was diluted with
ether and quenched with HCl 1 N. The ethereal layer was extracted,
was washed successively with H2O, sat. aq. NaHCO3 and brine, was
dried on MgSO4 and the solvent was evaporated. The residue was
purified by chromatography on SiO2 (PE:EtOAc 95:5) to afford an
orange solid 4 (1.07 g, 48%). A single crystal was obtained from
THF was distilled from sodium-benzophenone. CH2Cl2 was
dried with CaCl2 and distilled over CaH2. Tetramethylethylene-
diamine (TMEDA) was freshly distilled prior used. Dried TMAF was
prepared by the dehydration of TMAFÁ4H2O [12]. Silicagel
(Macherey-Nagel GmbH & Co KG – 40–63
mm, ASTM for column
chromatography) was used for flash chromatography. Preparative
centrifugal thin-layer chromatography was carried out on rotors
coated with silica gel 60 PF254 containing gypsum, the layer
thickness was 1 mm. NMR spectra were recorded, at frequencies of
250 MHz for 1H, 235.3 MHz for 19F and 62.9 MHz for 13C NMR.
Chemical shifts (() are reported in ppm relative to TMS for 1H and
13C NMR spectra and to CFCl3 for 19F NMR spectra. In the 13C NMR
data, reported signal multiplicities are related to C–F coupling. The
following abbreviations are used to indicate the multiplicities: s
(singlet), d (doublet), t (triplet), q (quartet), m (multiplet), br s
(broad singlet). Elemental analyses were performed on a Perkin-
Elmer CHN 2400 apparatus and analyses fell within Æ0.4% of the
calculated values. HRMS were recorded on a Micromass ESI-Q-TOF
mass spectrometer using an electrospray source in positive mode
(ESI+). GC–MS data were obtained on a Trace MS Thermoquest
apparatus at 70 eV in the electron impact mode.
ether for X-ray analysis. 1H NMR (CDCl3):
(3H, m, Ph), 5.12 (1H, s, OH), 4.32 (2H, m, CH2CH3), 2.61 (3H, m,
SCH3), 1.31 (3H, t, J = 7.0 Hz, CH2CH3). 13C NMR (CDCl3):
238.5
d 7.73 (2H, m, Ph), 7.38
d
(CS2), 170.5 (CO), 137.6 (C ipso), 128.8 (CH para), 127.9 (2 CH arom),
127.4 (2 CH arom), 88.3 (C–OH), 63.2 (CH2O), 20.7 (SCH3), 13.9
(CH2CH3). ESMS m/z 293.01 [M+Na]+.
4.5. Methyl 2-(dimethylcarbamoyloxy)-2-phenylethanedithioate (6)
To
a solution of diisopropylamine (446 mL, 3.18 mmol,
1.1 equiv.) in THF (7 mL) was added at À20 8C and under Ar, n-
BuLi (2.34 M in hexanes, 1.36 mL, 3.18 mmol, 1.1 equiv.). After
20 min of stirring at this temperature, the carbamate 5 (600 mg,
2.89 mmol) in solution of THF (3 mL) was added to the reaction
4.2. Precursors of starting dithioesters
Benzyloxy(t-butyl)dimethylsilane 1 was prepared according to
the literature [13]. The carbonate 3 was prepared according to a
reported procedure [14]. The carbamates 5, 8a and 8b were
prepared by treatment of the corresponding benzyl alcohol with
dimethylcarbamoyl chloride in pyridine according to a reported
procedure [9]. Compounds 5 [9] and 8a [15] were already
described.
mixture followed by CS2 (191
30 min of supplementary stirring. After 1 h of supplementary, MeI
(270 L, 4.33 mmol, 1.5 equiv.) was added and the stirring was
mL, 3.18 mmol, 1.1 equiv.) after
m
continued for 1 h at rt. The reaction was diluted with ether and
quenched with HCl 1 N. The ethereal layer was extracted, was
washed with sat. aq. NaHCO3 and brine, was dried on MgSO4 and
the solvent was evaporated. The residue was purified by
4.2.1. 1-Phenylpropyl dimethylcarbamate (8b)
Yield: 92%. Oil, bp 85 8C (2 mbar). 1H NMR (CDCl3):
d 7.29 (5H,
3
We have also prepared silyl ethers with different substitution pattern on silicon
m, Ph), 5.58 (1H, t, J = 6.5 Hz, CH–O), 2.97 (3H, br s, NCH3), 2.89 (3H,
br s, NCH3), 1.87 (2H, m, CH2CH3), 0.89 (3H, t, J = 7.0 Hz, CH2CH3).
but their metallation was more problematic: desilylation for TMS derivative; low
reactivity for TIPS derivative.

S. Gouault-Bironneau et al. / Journal of Fluorine Chemistry 134 (2012) 164–171
169
chromatography on SiO2 (PE:EtOAc 80:20) to afford 6 (300 mg,
35%) as an oil. 1H NMR (CDCl3):
7.50 (2H, m, Ph), 7.41 (3H, m, Ph),
6.92 (1H, s, CH–O), 3.33 (4H, m, 2 CH2CH3), 2.58 (3H, s, SCH3), 1.11
7.42–7.22 (5H, m, Ph), 4.28 (2H, q, J = 7.0 Hz, CH2–CH3), 2.49 (s,
SCH3 minor), 2.33 (s, SCH3 major), 1.31 (3H, t, J = 7.0 Hz, CH2–CH3).
13C NMR (CDCl3):
d 166.7 (CO minor), 166.6 (CO major), 148.1 (55C
d
(3H, t, J = 7.0 Hz, CH2CH3), 1.08 (3H, t, J = 7.0 Hz, CH2–CH3).
minor), 148.0 (55C major), 135.3 (C ipso minor), 134.6 (C ipso major),
129.4, 129.0, 128.8, 128.7, 128.6, 128.5 (CH arom), 128.6 (q, CF3, JCF
308 Hz), 127.6 (C55 minor), 127.2 (C55 major), 62.4 (O–CH2 minor),
62.1 (O–CH2 major), 17.8 (SCH3 minor), 17.6 (SCH3 major), 14.1
(CH2CH3 minor), 14.0 (CH2CH3 major). ESMS m/z 344.9 [M+Na]+.
4.6. Methyl 2-(dimethylcarbamoyloxy)-2-phenylpropanedithioate
(9a)
In a three neck flask, under argon, were introduced carbamate 8a
(3.86 g, 0.02 mol), anhydrous THF (150 mL) and TMEDA (2.4 g,
0.021 mol, 1.05 equiv.). After cooling to À78 8C, s-BuLi (1.4 M in
cyclohexane, 16 mL, 0.022 mol, 1.1 equiv.) was added slowly. The
resulting mixture turned to deep yellow and was kept at À78 8C for
5 min. CS2 (1.4 mL, 0.023 mol, 1.15 equiv.) was added over 1 min,
with a color turning to deep red. Finally methyl iodide (1.4 mL,
0.023 mol, 1.15 equiv.) was added, giving an orange mixture. The
coolingbath was removed (aprecipitateappeared atÀ25 8C)and the
reaction mixture was left under stirring overnight. The mixture was
partitioned between water (100 mL) and ether (150 mL). Ethereal
solution was washed with water (3Â 50 mL), then with brine (2Â
75 mL), dried and concentrated, giving an almost pure product (1H
NMR) as an orange oil. Final flash chromatography on silicagel
(CH2Cl2) yielded 9a (4.6 g, 81%) as a yellow-orange oil (Rf = 0.75).
4.8.2. Methyl 2-ethoxycarbonyl-2-phenyl-2-
(trimethylsilyloxy)ethanedithioate (12)
1H NMR (CDCl3):
d
7.70 (2H, m, Ph), 7.34 (3H, m, Ph), 4.25 (2H,
m, CH2CH3), 2.55 (3H, s, SCH3), 1.30 (3H, t, J = 7.0 Hz, CH2CH3), 0.21
(9H, s, Si(CH3)3). 13C NMR (CDCl3):
239.5 (CS2), 169.4 (C55O),
d
140.6 (C ipso), 128.2 (CH para), 127.6 (2 CH arom), 127.3 (2 CH
arom), 92.6 (C–CS2), 62.3 (CH2O), 19.5 (SCH3), 13.9 (CH2CH3), 1.69
(Si(CH3)3). Anal. calcd for C15H22O3S2Si: C, 52.59; H, 6.47. Found: C,
52.72; H, 6.75.
4.9. 1-Methylsulfanyl-2-phenyl-1-(trifluoromethylsulfanyl)propene
(14a). Typical procedure
To predried CsF (0.15 mg, 0.89 mmol, 0.18 equiv.) was added a
solution of dithioester 9a (1.4 g, 4.94 mmol) in DME (20 mL) then
CF3TMS (0.75 mL, 5.07 mmol, 1.02 equiv.). The mixture was
vigorously stirred at rt for 14 h. The reaction was monitored by
GC–MS. The reaction was completed after the introduction of an
additional amount of CF3TMS (0.35 mL, 2.37 mmol, 0.47 equiv.)
and 10 h stirring. The volatile products were evaporated, the
residue was stirred with petroleum ether (25 mL), filtered and
1H NMR (CDCl3):
CH3N), 2.92 (3H, s, CH3N), 2.55 (3H, s, CH3S), 2.37 (3H, s, CH3). 13
NMR (CDCl3): 239.8 (C55S), 153.6 (C55O), 142.6 (CH ipso), 128.0
d 7.56 (2H, m, Ph), 7.31 (3H, m, Ph), 3.21 (3H, s,
C
d
(CH ortho), 127.39 (CH para), 124.6 (CH meta), 92.5 (C quat.), 36.3
(CH3N), 36.2 (CH3N), 27.7 (CH3), 19.5 (CH3S). GC–MS 70 eV, m/z
(rel. int.): 236 [MÀCH3S] (5), 195 [MÀOCONMe2] (50), 147
[MÀOCONMe2–CH3S] (92), 103 (100).
evaporated to give
a crude orange oil (
19F NMR ratio of
4.7. Methyl 2-(dimethylcarbamoyloxy)-2-phenylbutanedithioate
stereoisomers: 1:0.22). Chromatography over silicagel (PE) gave
successively as pale yellow oil: (Z)-14a, Rf = 0.45, 0.065 g; a
mixture (Z,E)-14a, 0.31 g and (E)-14a, Rf = 0.35, 0.66 g. Total yield:
79% (see discussion for configuration assignments).
(9b)
The same procedure was applied to carbamate 8b (4.14 g,
0.02 mol) to prepare 9b (5.44 g (91%); Rf = 0.4 (CH2Cl2).
Major E-isomer, Rf 0.35 (PE, SiO2). 19F NMR (CDCl3):
CF3). 1H NMR (CDCl3):
7.37 (3H, m, Ph), 7.20 (2H, m, Ph), 2.43 (3H,
s, CH3), 2.24 (3H, s, SCH3). 13C NMR (CDCl3):
156.3 (q, JCF = 1.4 Hz,
d
À41.8 (s,
1H NMR (CDCl3):
d
7.55 (2H, m, Ph), 7.30 (3H, m, Ph), 3.25 (3H, s,
d
CH3N), 3.07 (2H, ddq, 2J = 14.5 Hz, 3J = 7.5 Hz, CH2), 2.93 (3H, s,
CH3N), 2.54 (3H, s, CH3S), 0.78 (3H, t, 3J = 7.5 Hz, CH3). 13C NMR
d
55C), 142.3 (Cipso), 129.6 (q, JCF = 310.0 Hz, CF3), 128.4 (CH ortho),
127.9 (CH para), 127.19 (CH meta), 119.6 (q, JCF = 1.3 Hz, C55), 26.1
(CH3), 17.8 (SCH3). GC–MS 70 eV, m/z (rel. int.): 264 [M+] (70), 195
[MÀCF3] (25), 163 [MÀS-CF3] (8), 148 [MÀS-CF3–CH3] (100), 115
(54), 103 (64).
(CDCl3):
d 239.9 (C55S), 153.4 (C55O), 141.6 (C ipso), 128.05 (CH
ortho), 127.4 (CH para), 124.8 (CH meta), 95.6 (C quat.), 36.4 (2
CH3N), 31.4 (CH2), 19.4 (CH3S), 7.4 (CH3). GC–MS 70 eV, m/z (rel.
int.): 250 [MÀCH3S] (3), 209 [MÀOCONMe2] (30), 206 [MÀCS2Me]
(27), 162 [MÀOCONMe2–CH3S] (60), 147 (100).
Minor Z-isomer, Rf 0.45 (PE, SiO2). 19F NMR (CDCl3):
CF3). 1H NMR (CDCl3):
7.35 (m, 3H, Ph), 7.14 (m, 2H, Ph), 2.46 (s,
3H, CH3), 2.43 (s, 3H, SCH3). 13C NMR (CDCl3):
156.3 (q, 55C, JCF
d
À41.9 (s,
d
4.8. Trifluoromethylation of dithiomalonic derivative (4)
d
1.4 Hz), 143.0 (Cipso), 129.1 (q, JCF = 310.0 Hz, CF3), 128.3 (CH ortho),
127.7 (CH para), 127.6 (CH meta), 120.0 (q, JCF = 1.3 Hz, C55), 25.8
(CH3), 17.3 (SCH3).
To a solution of 4 (220 mg, 0.81 mmol) and dried TMAF (8.3 mg,
0.089 mmol, 0.11 equiv.) in THF (6 mL) was added at À20 8C and
under Ar CF3SiMe3 (198
mL, 1.36 mmol, 1.67 equiv.). The tempera-
ture was slowly raised to rt and the reaction mixture was stirred for
18 h 30 min and then quenched with sat. aq. NH4Cl. The organic
layer was extracted with ether, washed with brine, dried (MgSO4)
and the solvent was evaporated. The residue was purified by
centrifugalthinlayerchromatography(PE:EtOAc98:2)toafford first
12 (Rf = 0.9, 91 mg, 33%), then 11 (Rf = 0.74, 60 mg, 23%), as oils.
A separate experiment carried out from 4 (300 mg, 1.11 mmol)
and TMAF (52 mg, 0.55 mmol, 0.5 equiv.), afforded a mixture
(254 mg) of the ketene dithioacetal 11 and a trifluoromethylated
by-product x. The molar ratio 11/x is 84/16 based on CF3 signals
integration.
4.10. 1-Methylsulfanyl-2-phenyl-1-(trifluoromethylsulfanyl)but-1-
ene (14b)
According to the typical procedure, reaction of dithioester 9b
(1.74 g, 5.85 mmol) with CF3TMS (1.0 mL + 0.3 mL, 8.8 mmol,
1.5 equiv.) and CsF (0.1 g, 0.6 mmol, 0.1 equiv.) in DME (20 mL)
yielded the ketene dithioacetal 14b (1.4 g, 86%, 1:0.15 mixture of E/
Z isomers) as a pale yellow oil. In a separate experiment, a careful
flash chromatography (PE) allowed to isolate pure samples of each
of the stereoisomers: (Z)-14b, Rf = 0.45, 10%; (E)-14b, Rf = 0.3, 77%.
Major E-isomer, Rf 0.3 (PE, SiO2). 19F NMR (CDCl3):
CF3). 1H NMR (CDCl3):
7.37 (3H, m, Ph), 7.15 (2H, m, Ph), 2.86 (2H,
q, 3J = 7.3 Hz, CH2), 2.22 (3H, s, SCH3), 0.91 (3H, t, 3J = 7.3 Hz, CH3).
13C NMR (CDCl3):
161.6 (q, JCF = 1.0 Hz,55C), 140.8 (C ipso), 129.4
d
À41.9 (s,
d
4.8.1. 1-Methylsulfanyl-1-trifluoromethylsulfanyl-2-
ethoxycarbonyl-2-phenylethene (11)
d
Mixture of 2 diastereomers (77:23 determined by 19F NMR). 19
F
(q, JCF = 310.5 Hz, CF3), 128.4 (CH ortho), 127.9 (CH para), 127.8 (CH
5
NMR (CDCl3):
d
À40.4 (minor), À41.4 (major). 1H NMR (CDCl3):
d
meta), 119.3 (q, JCF = 1.2 Hz, C55), 32.0 (CH2), 17.8 (q, JCF = 0.9 Hz,

170
S. Gouault-Bironneau et al. / Journal of Fluorine Chemistry 134 (2012) 164–171
SCH3), 12.4 (CH3). GC–MS 70 eV, m/z (rel. int.): 278 [M+] (100), 263
[MÀCH3] (4), 209 [MÀCF3] (30), 162 (45), 129 (70), 115 (70), 103
(64).
major), À38.9 (CF3 minor), À147.5 (BF4 minor), À149.9 (BF4 major).
1H NMR (CDCl3):
7.47–7.38 (5H, m, Ph), 4.38 (2H, q, J = 7.0 Hz,
CH2CH3), 3.03 (s, S(CH3)2 minor), 2.90 (s, S(CH3)2 major), 1.25 (3H, t,
J = 7.0 Hz, CH2CH3).
d
Minor Z-isomer, Rf 0.45 (PE, SiO2). 19F NMR (CDCl3):
CF3). 1H NMR (CDCl3):
7.34 (3H, m, Ph), 7.09 (2H, m, Ph), 2.83 (2H,
q, 3J = 7.4 Hz, CH2), 2.43 (3H, s, SCH3), 0.98 (3H, t, 3J = 7.4 Hz, CH3).
13C NMR (CDCl3):
162.4 (q, JCF = 1.6 Hz,55C), 141.7 (C ipso), 129.1
d
À41.8 (s,
d
4.14. (Z)-dimethyl(2-phenyl-1-(trifluoromethylsulfanyl)but-1-
d
enyl)sulfonium trifluoromethanesulfonate (17)
(q, JCF = 311.4 Hz, CF3), 128.2 (CH ortho), 128.1 (CH para), 127.6 (CH
meta), 119.9 (q, JCF = 1.7 Hz, C55), 32.2 (CH2), 17.4 (SCH3), 12.4
(CH3).
To a benzene solution (2 mL) of ketene dithioacetal (E)-14b
(54 mg, 0.194 mmol) was added methyltriflate (32 mg,
0.195 mmol, 1 equiv.) and the mixture was stirred at rt for 2 h.
Solvent was removed and the oily residue was washed with ether
and dried in vacuum to yield the salt 17 (83 mg, 97%). 19F NMR
4.11. 1-Methylsulfanyl-1-pentafluoroethylsulfanyl-2-phenylpropene
(15a)
(CDCl3):
d
À41.2 (3F, s, S-CF3), À79.4 (3F, s, SO2CF3). 1H NMR
According to the typical procedure, reaction of dithioester 9a
(1.4 g, 4.94 mmol) with CF3CF2TMS (1.0 g + 0.43 g, 7.44 mmol,
1.5 equiv.) and CsF (0.15 g, 0.89 mmol, 0.18 equiv.) in DME (20 mL)
yielded 15a (1.29 g, 83%, 1:0.16 mixture of isomers) as a pale
yellow liquid.
(acetone-d6):
d 7.52 (3H, m, Ph), 7.41 (2H, m, Ph), 3.18 (2H, q,
3J = 7.5 Hz, CH2), 3.11 (6H, s, S(CH3)2), 0.88 (3H, t, J = 7.5 Hz, CH3).
ESMS m/z (rel. int.): 293 [MÀTfO] (45), 231 [MÀTfO–CH3SCH3]
(74), 103 (100).
Major E-isomer, Rf 0.3 (PE, SiO2). 19F NMR (CDCl3):
d
À83.3 (3F, t,
4.15. Reaction of compound 14b with triflic acid and hydrolysis
3JFF = 3.5 Hz, CF3), À91.7 (2F, q, 3JFF = 3.5 Hz, CF2). 1H NMR (CDCl3):
d
7.37 (3H, m, Ph), 7.20 (2H, m, Ph), 2.42 (3H, s, CH3), 2.24 (3H, s,
SCH3). 13C NMR (CDCl3):
d 157.6 (t, JCF = 1.3 Hz,55C), 142.3 (C ipso),
To a solution of ketene dithioacetal 14b (140 mg, 0.5 mmol) in
0.5 mL of CDCl3 triflic acid (220 mg, 1.47 mmol, 2.94 equiv.) was
added under argon at 0 8C. The color of solution turned to dark
yellow from pale yellow and NMR spectra were recorded after
5 min of stirring to room temperature. The salt 18 was observed as
a 55/45 mixture of diastereomers.
128.5 (CH ortho), 128.1 (CH para), 127.3 (CH meta), 120.8 (tq,
JCF = 291.5 Hz, JCF = 40.5 Hz, CF2), 118.2 (t, JCF = 1.7 Hz, C55), 116.5
(qt, JCF = 287.3 Hz, 3JCF = 37.0 Hz, CF3), 26.3 (CH3), 18.0 (SCH3). GC–
MS 70 eV, m/z (rel. int.): 314 [M+] (30), 195 [MÀC2F5] (22), 148
[MÀSC2F5–SCH3] (100), 103 (64).
Minor Z-isomer, Rf 0.4 (PE, SiO2). 19F NMR (CDCl3):
d
À83.6 (3F, t,
4.15.1. 1-(Methylsulfanyl)-2-phenyl-1-
3JFF = 3.5 Hz, CF3), À91.8 (2F, q, 3JFF = 3.5 Hz, CF2). 1H NMR (CDCl3):
(trifluoromethylsulfanyl)butan-1-ylium trifluoromethanesulfonate
d
7.32 (3H, m, Ph), 7.11 (2H, m, Ph), 2.45 (3H, s, CH3), 2.43 (3H, s,
(18)
SCH3).
19F NMR (CDCl3):
d
À35.7 (s, S-CF3 major), À40.1 (s, S-CF3 minor),
À77.3 (CF3SO3H), À78.7 (CF3SO3À). 1H NMR (CDCl3): 7.6–7.3 (5H, m,
Ph), 4.92 (dd, 3J = 8.5 Hz, 3J = 5.5 Hz, CH major), 4.86 (dd, 3J = 9.0 Hz,
3J = 5.0 Hz, CH minor), 3.50 (s, SCH3 minor), 3.33 (s, SCH3 major), 2.45
4.12. 1-Methylsulfanyl-1-pentafluoroethylsulfanyl-2-phenylbut-1-
ene (15b)
and 2.27 (2H, m, CH2), 1.17 (t, 3J = 7.0 Hz, CH3 major), 1.11 (t,
3J = 7.5 Hz, CH3 minor). 13C NMR (CDCl3):
4
According to the typical procedure, reaction of dithioester 9b
(98 mg, 0.33 mmol) with CF3CF2TMS (70 mg + 26 mg, 0.5 mmol,
1.5 equiv.) and CsF (0.10 g, 0.06 mmol, 0.18 equiv.) in DME (4 mL)
afforded the ketene dithioacetal 15b (98 mg, 90%, 1:0.13 mixture
of E/Z isomers) as a pale yellow liquid.
d
247.3 (q, JCF = 1.0 Hz,
CS2), 246.3 (q, 4JCF = 1.0 Hz, CS2), 134–126 (C arom + CF3), 118.6 (q,
CF3SO3H), 62.7 (q, 3JCF = 2.5 Hz, CH), 62.7 (q, 3JCF = 1.5 Hz, CH), 32.9
(CH2), 29.1 (CH2), 24.8 (SCH3), 24.1 (SCH3), 12.4 (CH3), 11.5 (CH3).
ESMS m/z (rel. int.): 279 [MÀTfO] (40), 231 [MÀTfO–CH3SH] (20),
177 [MÀTfO–CF3SH] (35), 129 (100).
Major E-isomer, Rf 0.3 (PE, SiO2). 19F NMR (CDCl3):
d
À83.4 (3F, t,
3
3
CF3, JFF = 3.5 Hz), À91.72 (2F, q, JFF = 3.5 Hz, CF2). 1H NMR
After recording of spectra the chloroform solution was poured
in cold water (1 mL), and the mixture was stirred for 5 min. The
organic layer was separated and washed with water (2Â 1 mL).
After drying over MgSO4 the solvent was evaporated and residue
was filtered through a short column of silicagel using CH2Cl2 as
eluent. Two fractions were collected, containing the thiol ester 19
[16] (40 mg, 38%) (Rf ꢀ 1) and the acid 20 [17] (26 mg, 30%)
(Rf = 0.3) as colorless oils.
(CDCl3):
d 7.42 (3H, m, Ph), 7.21 (2H, m, Ph), 2.92 (2H, q,
3J = 7.7 Hz, CH2), 2.28 (3H, s, SCH3), 0.97 (3H, t, 3J = 7.7 Hz, CH3). 13
NMR (CDCl3): 162.8 (t, JCF = 1.0 Hz,55C), 140.8 (C ipso), 128.4 (CH
C
d
ortho), 128.0 (CH para), 127.7 (CH meta), 120.6 (tq, JCF = 292.4 Hz,
3
3JCF = 40.2 Hz, CF2), 118.8 (qt, JCF = 286.3 Hz, JCF = 36.5 Hz, CF3),
117.8 (t, JCF = 1.6 Hz, C55), 32.1 (CH2), 17.9 (SCH3), 12.4 (CH3). GC–
MS 70 eV, m/z (rel. int.): 328 [M+] (65), 281 [MÀCH3S] (2), 209
[MÀC2F5] (40), 162 (66), 128 (68), 115 (90), 103 (100).
Minor Z-isomer, Rf 0.45 (PE, SiO2). 19F NMR (CDCl3):
d
À83.6 (3F,
4.15.2. S-methyl 2-phenylbutanethioate (19)
3
3
t, JFF = 4.0 Hz, CF3), À91.7 (2F, q, JFF = 4.0 Hz, CF2). 1H NMR
1H NMR (CDCl3): 7.32 (5H, m, Ph), 3.65 (1H, t, 3J = 7.5 Hz, CH),
2.25 (3H, s, SCH3), 2.16 (1H, m, CHAHB), 1.85 (1H, m, CHAHB), 0.89
(CDCl3):
d 7.32 (3H, m, Ph), 7.08 (2H, m, Ph), 2.85 (2H, q,
3
3JHH = 7.7 Hz, CH2), 2.44 (3H, s, SCH3), 0.99 (3H, t, JHH = 7.7 Hz,
(3H, t, 3J = 7.0 Hz, CH3). 13C NMR (CDCl3):
d 201.0 (C55O), 138.6,
CH3).
128.7, 128.7, 127.1, 126.9 (C arom), 53.4 (CH), 26.6 (CH2), 12.4
(SCH3), 11.8 (CH3). GC–MS 70 eV, m/z (rel. int.): 194 [M+] (3), 147
[MÀSCH3] (10), 119 [PhCHEt] (50), 91 (100).
4.13. 2-Ethoxycarbonyl-2-phenyl-1-(trifluoromethylsulfanyl)eth-1-
enyl)dimethylsulfonium trifluoromethanesulfonate (16)
4.15.3. 2-Phenylbutanoic acid (20)
A solution of 11 (100 mg, 0.310 mmol) and trimethyloxonium
tetrafluoroborate (90 mg, 0.373 mmol, 1.2 equiv.) in CH2Cl2 (4 mL)
was stirred at reflux for 11 h and then at rt for 13 h. The reaction
mixture was concentrated under reduced pressure. The residue
was washed with Et2O to give 16 (140 mg, 100%, 2 diastereomers
1H NMR (CDCl3): 7.31 (5H, m, Ph), 6.5 (1H, br s, OH), 3.46 (1H, t,
3J = 7.5 Hz, CH), 2.07 (1H, m, CHAHB), 1.80 (1H, m, CHAHB), 0.90 (3H,
t, 3J = 7.0 Hz, CH3). 13C NMR (CDCl3):
d 179.8 (C55O), 138.6, 128.8,
128.7, 128.2, 128.0 (C arom), 52.2 (CH), 26.4 (CH2), 12.2 (CH3). GC–
MS 70 eV, m/z (rel. int.): 164 [M+] (15), 119 [MÀCOOH] (40), 91
(100).
(
19F NMR), 84:16) as a viscous oil. 19F NMR (CDCl3):
d
À38.7 (CF3

S. Gouault-Bironneau et al. / Journal of Fluorine Chemistry 134 (2012) 164–171
171
Chem. 127 (2006) 471–475;
(d) C. Portella, Y.G. Shermolovich, Tetrahedron Lett. 38 (1997) 4063–4064.
[4] V.M. Timoshenko, C. Portella, J. Fluorine Chem. 130 (2009) 586–590.
[6] CCDC 805008 contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge from the Cambridge Crystallographic
Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.
[7] (a) S.D. Lee, T.H. Chan, K.S. Kwon, Tetrahedron Lett. 25 (1984) 3399–3402;
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Acknowledgments
We are grateful to CNRS, Universite de Reims Champagne-
´
´
Ardenne and Region Champagne-Ardenne for supporting this
research. We also thank Henry Baillia for the NMR analyses, Sylvie
Lanthony for elemental analyses and Emmanuel Wenger (Uni-
´
versite de Nancy) for the X-ray structure determination of
[8] R.A. Holton, C. Somoza, H.-B. Kim, F. Liang, R.J. Biediger, P. Douglas Boatman, M.
Shindo, C.C. Smith, S. Kim, H. Nadizadeh, Y. Suzuki, C. Tao, P. Vu, S. Tang, P. Zhang,
K.K. Murthi, L.N. Gentile, J.H. Liu, J. Am. Chem. Soc. 116 (1994) 1597–1598.
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[11] I. Kieltsch, P. Eisenberger, A. Togni, Angew. Chem. Int. Ed. 46 (2007) 754–
757.
compound 4.
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