A new method for the synthesis of trifluoromethylating agents-Diaryltrifluoromethylsulfonium salts

Article abstract of DOI:10.1016/j.jfluchem.2007.10.001

A new synthetic method has been developed to prepare diaryltrifluoromethylsulfonium salts from diaryldifluorosulfuranes by the action of Me₃SiCF₃/F^-. This reaction is the transformation of nucleophilic trifluoro-methylating reagent into electrophilic one.

Full text of DOI:10.1016/j.jfluchem.2007.10.001

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Journal of Fluorine Chemistry 129 (2008) 131–136
www.elsevier.com/locate/fluor
A new method for the synthesis of trifluoromethylating
agents—Diaryltrifluoromethylsulfonium salts
*
Lev M. Yagupolskii , Andrej V. Matsnev, Raisa K. Orlova,
Boris G. Deryabkin, Yurii L. Yagupolskii
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Murmanska 5, 02094 Kyiv, Ukraine
Received 8 August 2007; received in revised form 5 October 2007; accepted 6 October 2007
Available online 13 October 2007
Abstract
A new synthetic method has been developed to prepare diaryltrifluoromethylsulfonium salts from diaryldifluorosulfuranes by the action of
Me3SiCF3/Fꢀ. This reaction is the transformation of nucleophilic trifluoro-methylating reagent into electrophilic one.
# 2007 Elsevier B.V. All rights reserved.
Keywords: Diaryltrifluoromethylsulphonium salts; Trifluoromethyl group; Diarylsulfides; Nucleophilic mechanism
1. Introduction
charge is delocalized only over one carbon atom and three
fluorine atoms. Therefore, the electrophilic perfluoroalkylation
of various organics and inorganics using iodonium salts which
we developed formerly (1978) [4] was restricted to introduction
of perfluoroalkyl residues larger than the CF3 group. At firsꢀt,
Clꢀ was contained as an anion in these salts and then the BF4
anion was used to completely ionize the bond between the
iodine atom and the perfluoroalkyl group. Later on (1982),
Umemoto carried out his voluminous work on electrophilic
perfluoroalkylation using compounds with the CF3SO3ꢀ anion
(FITS reagents) [5] in which the I–OSO2CF3 bond was very
polar but not completely ionic. As in our preceding
experiments, Umemoto likewise failed to accomplish electro-
philic trifluoromethylation with iodonium salts. Recently,
cyclic compounds have been obtained which contain the
iodine atom bound to the trifluoromethyl group and the oxygen
atom. A lone electron pair on the oxygen atom significantly
weakens the trifluoromethylating ability of such reagents [6].
One of the present authors succeeded to conduct electro-
philic trifluoromethylation by meansꢀof diaryl(trifluoromethyl)-
sulfonium salts Ar2S+CF3 SbF6 in 1984 [7]. These
trifluoromethylating reagents were obꢀtained by the reaction
of the salts p-ClC6H4S+(F)CF3 SbF6 with aromatic com-
pounds. In the method that was developed, the electrophilic
substitution only proceeds smoothly if electron-donor sub-
stituents are in the aromatic ring. On the other hand, such
substituents partially neutralize a positive charge on the sulfur
atom thus significantly reducing the trifluoromethylating
Organic compounds containing trifluoromethyl group have
found wide application in the synthesis of medicines,
pesticides, dyes, polymers, and a variety of other materials [1].
Initially, the synthesis of compounds containing trifluor-
omethyl group involved the replacement of the chlorine atoms
in the CCl3 group by fluorine atoms using HF or SbF3, the
reaction of carboxylic acids with SF4, or the reaction of CF3Cu
with aromatic bromo and iodo derivatives [2]. Afterwards,
radical trifluoromethylation reactions were used [1] which
implied formation of the trifluoromethyl radical reacting
unselectively with a substrate.
Prakash pioneered nucleophilic methods for the introduction
of the trifluoromethyl group, with the application of Me3SiCF3/
Fꢀ system generating CF3 anion [3]; this strategy has been
usefully employed in recent years.
ꢀ
An idea of electrophilic perfluoroalkylation in which a
perfluoroalkyl group could be positively charged at first
appeared to violate common sense. However, such reactions
turned out to be quite possible provided the perfluoroalkyl
group is bound to a positively charged heteroatom.
Among all the perfluoroalkyl moieties, the trifluoromethyl
cation appears to be the most unfavorable one, as its positive
* Corresponding author.
E-mail address: matsnev@bpci.kiev.ua (A.V. Matsnev).
0022-1139/$ – see front matter # 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2007.10.001

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reactivity of the salts obtained. Later on, Shreeve and co-
workers [8] and Wakselman and co-workers [9] showed that
reactions of this kind were also possible with benzene and its
fluoro, chloro and trifluoromethoxy derivatives, i.e., with
compounds usually entering into the Friedel–Krafts reaction
and containing no strongly electron-withdrawing substituents.
A much greater trifluoromethylating ability was exhibited
by S-(trifluoromethyl)-dibenzothiophenium salts lacking elec-
tron-donor residues which were synthesized by Umemoto [10].
He succeeded in nitrating the salts obtained so that one or two
nitro groups were introduced into the meta position to the
trifluoromethylsulfonium moiety [10]. Subsequently, Shreeve
also introduced a nitro group into the meta position to the sulfur
atom by the nitration of diphenyl- and 4-fluorodiphenyl(tri-
fluoromethyl)sulfonium salts [8]. The nitro compounds proved
to be much more reactive than their non-nitrated analogues.
The present work is aimed at the development of a general
synthetic method to prepare diaryl(trifluoromethyl)sulfonium
salts, especially those containing strong electron-withdrawing
substituents both at the meta and the para positions to the
S+ꢀCF3 group.
Scheme 1.
Scheme 2.
fonic anhydride. This reaction is probably an equilibrium one,
especially if electron-withdrawing substituents are present in
the benzene ring; therefore, a large excess of trifluorometha-
nesulfonic anhydride is needed (Scheme 3).
2. Results and discussion
Appropriate diaryl sulfides chosen as starting compounds
were reacted with xenon difluoride to afford diaryldifluor-
osulfuranes (Scheme 1).
To study the reactivity of the diaryltrifluoromethylsulfonium
salts obtained, they were subjected to reactions with different
nucleophiles (Scheme 4). As expected, salts 3d and 3e appeared
to be the most reactive. For instance, 3a was found to react with
sodium iodide only under heating, whereas the reaction with 3d
went to completion after 6 h at room temperature and 3e
provided CF3I (5) after a 3-h reaction time at room temperature.
4-Nitrophenyl(phenyl)(trifluoromethyl)sulfonium tetrafluoro-
borate (3d) was reacted with sodium iodide and sodium p-
nitrothiophenolate. Salt 4 reacted with N-methylpyrrole and
N,N-dimethylaniline to furnish trifluoromethyl derivatives.
Diaryltrifluoromethylsulfonium salts were previously
demonstrated to react with compounds bearing a negatively
charged sulfur atom, e.g., with thiophenolates. It was of interest
to ascertain whether compounds with an uncharged electron-
rich sulfur atom could be trifluoromethylated. N,N,N0,N0-
Tetraethylthiourea turned out to react with 4-nitrophenyl(phe-
nyl)(trifluoromethyl)sulfonium salt to give sulfonium salt 9.
A thiocarbonyl group, if separated from electron-donor
substituents by benzene rings, enters into the reaction as well. It
was thus possible to obtain dye 10 by trifluoromethylation of
Michler’s thioketone. This dye was synthesized by one of us
earlier using a hard-to-obtain reagent [15] (Scheme 5).
Elemental fluorine can be used for fluorination as well [11].
However, we employed xenon difluoride as a reagent more
conveniently handled in the laboratory.
The reaction strongly depends on the number of acceptor
substituents in the aromatic rings. Thus, diphenyl sulfide reacts
with xenon difluoride at 0 8C in petroleum ether to give solid
diphenyldifluorosulfurane [12], whereas 4-nitrodiphenyl sul-
fide enters into the reaction only at 50–70 8C. Boron trifluoride
etherate activating xenon difluoride can be used as a catalyst in
this reaction; in this case, however, some side-reactions occur
which significantly lower the yields of the desired products,
diarylfluorosulfonium tetrafluoroborates. The compounds
obtained entered into nucleophilic trifluoromethylation with
the reagent Me3SiCF3/Me4NF, i.e., with the trifluoromethyl
anion, and yielded diaryltrifluoromethylsulfonium salts.
The method allows a conversion of the CF3ꢀ anion reacting
with various substrates by a nucleophilic mechanism into an
electrophilic reagent containing an electropositive CF3d+ group
[13] (Scheme 2).
Salt 3d bearing a triflate group as an anion was synthesized
by the reaction of 4-nitrophenyltrifluoromethylsulfoxide [14]
with benzene in the presence of excess trifluoromethanesul-
Scheme 3.

L.M. Yagupolskii et al. / Journal of Fluorine Chemistry 129 (2008) 131–136
133
Scheme 4.
Not only thiophenolates but also the compounds of
tetravalent sulfur, e.g., the salts of sulfinic acids, turned out
to enter into electrophilic trifluoromethylations leading to the
corresponding sulfones (Scheme 6).
Using nucleophilic trifluoromethylation of arylsulfonyl
fluorides, aryltrifluoromethylsulfones were previously obtained
by one of the present authors together with collaborators [16].
The compounds of trivalent phosphorus also enter into the
reactions of electrophilic trifluoromethylation. Diethoxytri-
fluoromethylphosphonate 12 was synthesized by the reaction of
diethoxyphosphinate with diphenyl(trifluoromethyl)sulfonium
salt (Scheme 7).
Trifluoromethylation with sulfonium salts is possible when
the electrophilic attack is directed on a heteroatom not in its
highest valence state as, for instance, nitrogen in sodium nitrite
Scheme 5.
Scheme 6.
Scheme 7.
Scheme 8.

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L.M. Yagupolskii et al. / Journal of Fluorine Chemistry 129 (2008) 131–136
[17], sulfur in the salts of thiols and sulfinic acids, or
phosphorus in phosphinates.
3.1.3. 3,5-Di(trifluoromethyl)diphenyldifluorosulfurane
(2c)
The aryl(methyl)(trifluoromethyl)sulfonium salts synthe-
sized earlier act as methylating rather than trifluoromethylating
agents [7].
XeF2 (0.18 g, 1.07 mmol) was added to stirred 3,5-
di(trifluoromethyl)phenylphenylsulfide (0.3 g, 0.93 mmol).
The reaction mixture was heated to 50 8C and stirred at this
temperature till the end of effervesce of gas; then reaction
mixture became solid. The product was used without further
purification.
We obtained 4-nitrophenyl(trifluoromethyl)fluorosulfonium
salt 13 to ascertain whether this reagent provides electrophilic
trifluoromethylation or fluorination. For this purpose, salt 13
was reacted with electron-rich heterocycles, namely, N-
methylpyrrole and indole. The reaction proved to involve
substitution of the fluorine atom in salt 13 leading to hetaryl(4-
nitrophenyl)(trifluoromethyl)sulfonium salts 14 and 15
(Scheme 8).
3.1.4. 4-Nitrophenylphenyldifluorosulfurane (2d)
XeF2 (0.08 g, 0.47 mmol) was added to stirred 4-nitrophe-
nylphenylsulfide (0.1 g, 0.43 mmol). The reaction mixture was
heated to 50–70 8C and stirred at this temperature till the end of
effervesce of gas. The product was used without further
purification.
The compounds synthesized are the first representatives of
the trifluoromethylsulfonium salts in which the +SCF3 group is
bound to the heterocyclic moiety.
In conclusion, we have elaborated a new synthetic method to
aryl- and hetaryl(trifluoromethyl)sulfonium salts and demon-
3.1.5. 4,40-Dinitrodiphenyldifluorosulfurane (2e)
XeF2 (0.14 g, 0.83 mmol) was added to stirred 4,40-
dinitrodiphenylphenylsulfide (0.2 g, 0.73 mmol). The reaction
mixturewas heated to temperature of beginning of gas effervesce
and stirred at this temperature till the end of effervesce of gas.
ꢀ
strated a nontrivial transformation of the CF3 anion into the
positively charged CF3d+ group attacking various substrates by
an electrophilic mechanism.
3. Experimental
3.2. Typical procedure for synthesis of S-
(trifluoromethyl)diarylsulfonium salts (3a–e)
Moisture-sensitive reactions were carried out under dry
argon using flame-dried glassware. All chemicals were of
reagent grade or were purified by standard methods before use.
Solvents were distilled from the appropriate drying agents
immediately prior to use. Some reactions were monitored by
thin-layer chromatography (TLC) on precoated silica gel
Kieselgel 60 F/UV254 plates (Merck); spots were visualized
with UV light. Purification of most products was performed by
column chromatography (CC) on Silica gel, 70230 mesh 60A
(Aldrich). 1H and 19F NMR spectra were recorded at 299.5 and
282.2 MHz, respectively with a Varian VXR-300 spectrometer,
and chemical shifts are given in ppm relative to Me4Si and
CCl3F, respectively, as internal standards. Coupling constants
are given in Hz. Melting points were determined in open
capillaries and are uncorrected.
A three-necked flask was charged with Me4NF (0.12 g,
1.29 mmol) and glyme (5 mL). The mixture was cooled to ca.
ꢀ60 8C, and Me3SiCF3 (0.36 g, 2.54 mmol) was added. The
reaction mixture was stirred for ca. 1 h at ꢀ45 8C, then cooled
to ꢀ65 8C, and diaryldifluorosulfurane (1.29 mmol) was added.
The reaction mixture was stirred at this temperature for
additional 40 min and then BF3ꢁEt2O (0.37 g, 2.6 mmol) was
added. The mixture was allowed to warm to rt, the solvent was
evaporated. The residue was purified by silica gel chromato-
graphy (CH2Cl2:CH3CN = 4:1) to give the corresponding
product.
3.2.1. S-(Trifluoromethyl)diiphenylsulfonium
tetrafluoroborate (3a)
Yield 75%, mp 99–101 8C; 1H NMR (CDCl3): d 7.98–8.08
(m, 4H), 8.10–8.20 (m, 2H), 8.40–8.48 (m, 4H); 19F NMR
(CDCl3): d ꢀ50.3 (s, 3F), ꢀ150.1 (s, 4F). Anal. calcd for
C13H10BF7S: C, 45.61; H, 2.92. Found: C, 45.26; H, 3.19.
3.1. Sulfides (1 a–e) were synthesized by standard
procedures [18]
3.1.1. Diphenyldifluorosulfurane (2a)
XeF2 (0.22 g, 1.3 mmol) was added to a stirred solution of
diphenylsulfide (0.23 g, 1.24 mmol) in pentane (5 mL) cooled
to 0 8C. The reaction mixture was allowed to warm to rt and
stirred till the end of effervesce of gas. The product precipitated
as white crystals and was used without further purification after
decantation of the solvent.
3.2.2. S-(Trifluoromethyl)-4,40-difluorodiphenylsulfonium
tetrafluoroborate (3b)
1
Yield 61%, mp 113–114 8C; H NMR (CDCl3): d 7.61 (d,
4H); 8.35 (d, 4H) 19F NMR (CDCl3): d ꢀ50.19 (s, 3F); ꢀ95.86
(s, 2F); ꢀ150.9 (br s, 4F). Anal. calcd for C13H8BF9S, C 41,26;
H 2,12; S 8,48. Found: C, 40.97; H, 2.32; S, 8.90.
3.1.2. 4,40-Difluorodiphenyl(difluoro)sulfurane (2b)
XeF2 (0.23 g 1.36 mmol) was added to 4,40-difluorodiphe-
nylsulfide (0.3 g, 1.35 mmol) which was cooled to 0 8C and
stirred. The mixture was allowed to warm to rt and stirred till
the end of effervesce of gas. The product was used without
further purification.
3.2.3. S-(Trifluoromethyl)-3,5-
di(trifluoromethyl)diphenylsulfonium tetrafluoroborate (3c)
1
Yield 42%, H NMR (CDCl3): d 8.07 (t, 2H), 8.22 (t, 2H),
8.56 (d, 2H), 8.85 (s, 1H), 9.02 (s, 2H). 19F NMR (CDCl3): d
ꢀ47.79 (s, 3F), ꢀ62.32 (s, 6F), ꢀ149,57 (s, 4F). Anal. calcd for
C15H8BF13S: C, 37.66; H, 1.67. Found: C, 37.87; H, 1.96.

L.M. Yagupolskii et al. / Journal of Fluorine Chemistry 129 (2008) 131–136
135
3.2.4. S-(Trifluoromethyl)-4-nitrophenylphenylsulfonium
tetrafluoroborate (3d)
3.6. Mixture of o- and p-trifluoromethyl-N,
N-dimethylanilines (8)
1
Yield 40%, mp 135–137 8C (dec.); H NMR (CDCl3): d
7.76–7.91 (m, 1H), 7.97–8.12 (m, 2H), 8.13–8.25 (m, 2H),
8.36–8.60 (m, 2H), 8.61–8.0 9 (m, 2H). 19F NMR (CDCl3): d
ꢀ48.6 (s, 3F), ꢀ149.8 (s, 4F). Anal. calcd for C13H9BF7NO2S:
C, 40.31; H, 2.33; S, 8.27. Found: C, 40.13; H, 2.32; S,
8.23.
A two-necked flask was charged with a solution of salt 4 or
3d (0.5 g, 1.1 mmol) in water-free CH3CN (5 mL) and N,N-
dimethylaniline (0.3 g, 2.5 mmol). The mixture was refluxed
for 6 h. The reaction was monitored by TLC. After the reaction
completed, the solvent was evaporated. The residue was
purified by silica gel chromatography (pentane). Evaporation of
the solvent yielded 0.17 g of ca. 3:1 mixture of o- and p-
trifluoromethyl-N,N-dimethylanilines (82%). 1H NMR
(CDCl3): d 2.83 (s, 6H, p-N(CH3)2); 2.85 (s, 6H, o-
N(CH3)2); 6.57 (m, 1H); 6.70 (d, 2H, HC–(C–N(CH3)2)–
CH); 7.06 (m, 1H,); 7.25 (m, 1H); 7.27 (d, 2H, HC–CCF3–CH),
7.55 (m, 1H). 19F NMR (CDCl3): d ꢀ59.46 (s, 3F, p-
CF3);ꢀ60.12 (s, 3F, o-CF3). Anal. calcd for C9H10F3N: C
54.20; H 5.05; N 7.90. Found: C 54.18; H 5.02; N 7.75.
3.2.5. S-(Trifluoromethyl)-4,40-dinitrodiphenylsulfonium
tetrafluoroborate (3e)
Yield 35%, mp 158–160 8C (dec.); 1H NMR (CDCl3): d 8.76
(s). 19F NMR (CDCl3): d ꢀ47.2 (s, 3F), ꢀ148.7 (s, 4F). Anal.
calcd for C13H8BF7N2O4S: S 7,40. Found: S 7,11.
3.3. S-(Trifluoromethyl)-4-nitrophenylphenylsulfonium
triflate (4)
A three-necked flask was charged with 4-nitrophenyltri-
fluoromethylsulfoxide (0.2 g, 0.89 mmol) and 4 mL of ben-
zene. The solution was cooled to 2–3 8C, and
trifluorometanesulphonic anhydride (1.18 g, 4.2 mmol) was
added. The reaction mixture was stirred for 24 h at rt. The
excesses of benzene and anhydride were evaporated in vacuum
(20 Torr). Then CH2Cl2 (5 mL) was added. The solution
obtained was washed with cold water (3 mL ꢂ 7 mL), dried
over MgSO4 and concentrated in vacuum. The residue was
purified by silica gel chromatography (CH2Cl2:CH3CN = 4:1)
3.7. Tetraethylamino(trifluoromethylthio)carbenium
triflate (9)
A two-necked flask was charged with a solution of salt 4
(0.1 g, 0.22 mmol) in water-free CH3CN (5 mL) and tetra-
ethylthiourea (0.05 g, 0.27 mmol). The mixture was heated to
80 8C in the heating bath and stirred at this temperature for
16 h. The reaction was monitored by TLC. After the reaction
completed, the solvent was evaporated. The residue was
purified by silica gel chromatography (CH2Cl2:CH3CN = 8:1).
Evaporation of the solvent yielded 0.06 g of 9 (79%). 1H NMR
(CDCl3): d 1.38 (t, 3H); 3.8 (q, 2H). 19F NMR (CDCl3): d ꢀ38.5
(s, 3F), ꢀ78.3 (c, 3F); FAB-HRMS: m/z 257 ([M-CF3SO3ꢀ],
C11H20F6N2O3S2 calcd 257).
1
to give 0.16 g of 4 (42.5%). H NMR (CDCl3): d 7.86–7.89
(d, 2H); 8.36–8.39 (d, 2H); 8.65–8.75 (m, 5H). 19F NMR
(CDCl3): d ꢀ48.95 (s, 3F). ꢀ78.7 (s, 3F). Anal. calcd for
C14H9F6NO5S2: C 37.42; H 2.00; S 14.25. Found: 37.22; H
2.29; S 13.65.
3.8. Bis[4-(N,N-
dimethylamino)phenyl](trifluoromethylthio)carbenium
triflate (10)
3.4. Trifluoroiodomethane (5)
To a suspension of NaI (0.1 g, 0.67 mmol) in CH3CN (3 mL)
salt 3a (0.2 g, 0.59 mmol) was added. The reaction mixture was
refluxed for 15 min. The product was distilled into a receiver
A two-necked flask was charged with a solution of salt 4
(0.1 g, 0.22 mmol) in water-free CH3CN (5 mL) and Michler’s
thioketone (0.13 g, 0.46 mmol). The mixture was heated to
80 8C and stirred at this temperature for 16 h. The reaction was
monitored by TLC. After the reaction completed, the solvent
was evaporated. The residue was purified by silica gel
chromatography (CH2Cl2:CH3CN, 8:1). Evaporation of the
solvent yielded 0.07 g of 10 (72%). 1H NMR (CDCl3): d 3.39 (s,
6H), 7.01 (d, 4H), 7.73 (d, 4H). 19F NMR (CDCl3): d ꢀ38.5 (s,
3F), ꢀ78.3 (s, 3F); FAB–HRMS: m/z 341 ([M-CF3SO3ꢀ],
C18H20F6N2O3S2 calcd 341).
cooled with liquid nitrogen. The yield of 5 was quantitative. 19
NMR (CDCl3): d ꢀ15.5 (s). GLC data: holding time, 4 min. 19
NMR (CDCl3): d ꢀ15.5 (s).
F
F
3.5. 4-Nitrophenyltrifluoromethylsulfide (6) was prepared
from 3d according to literature procedure [7]
3.5.1. 7. 2-Trifluoromethyl-N-methylpyrrole (7)
A two-necked flask was charged with a solution of salt 4
(0.2 g, 0.45 mmol) in water-free THF (1 mL) and N-methyl-
pyrrole (0.9 g, 11.1 mmol). The mixture was refluxed for 7 h.
Then water (5 mL) was added. The product was extracted with
pentane, dried over MgSO4 and concentrated in vacuum. The
residue was purified by silica gel chromatography (pentane)
3.9. Reaction of sodium salt of 4-chlorobenzenesulfinic
acids and diphenyl(S-trifluoromethyl)sulfonium
tetrafluoroborate (3a)
1
and yielded 0.06 g of 7 (90%). H NMR (CDCl3): d 4.55 (s,
A solution of sodium salt of 4-chlorobenzenesulfinic acid
(0.06 g, 0.3 mmol) and salt 2a (0.1 g, 0.29 mmol) in water-free
DMSO(5 mL)wasstirredat100 8Cfor3 h. Thereactionmixture
was thenpouredontowater. Theproduct was extractedwithether
3H); 6.8 (t, 1H); 7.25 (d, 1H); 7.48 (d, 1H). 19F NMR (CDCl3): d
ꢀ59.08 (s, 3F). Anal. calcd for C6H6F3N: C, 48.32; H, 4.03; N,
9.39. Found: C, 48.29; H, 3.97; N, 9.20.

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L.M. Yagupolskii et al. / Journal of Fluorine Chemistry 129 (2008) 131–136
(3 mL ꢂ 5 mL), dried over MgSO4 and concentrated in vacuum.
The residuewas purified by silica gel chromatography (pentane).
Evaporation of the solvent yielded 0.06 g of 11 (81%). Mp = 55–
56 8C (pentane) [20]. 19F NMR (CDCl3): d ꢀ76.9.
(d, 1H), 7.97 (d, 1H), 8.54 (d, 2H), 8.71 (d, 2H), 9.14 (s, 1H),
12.68 (br s, 1H). 19F NMR (CDCl3): d ꢀ53.4 (s, 3F), ꢀ149.2
(s, 4F). Anal. calcd for C15H10BF7N2O2S: C, 42.25; H, 2.35.
Found: C, 41.75; H 2.02.
3.10. Reaction of sodium diethoxyphosphinate and
diphenyl(S-trifluoromethyl)sulfonium tetrafluoroborate
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XeF2 (0.14 g, 0.83 mmol) and BF3ꢁEt2O (0.1 g, 0.71 mmol)
were added to a stirred solution of 4-nitrophenyltrifluoro-
methylsulfide (0.15 g, 0.67 mmol) in dichloromethane (5 mL)
at ꢀ60 8C. The reaction mixture was stirred at rt till the end of
effervesce of gas. The product was used without further
purification.
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of Papers, 18th International Symposium on Fluorine Chemistry, Bremen,
Germany, July 30–August 4, 2006, PM-Grafik-Design, Herstellung,
Wachtersbach, 2006, 150.
3.12. Typical procedure for synthesis of S-(trifluoromethyl)
arylhetarylsulfonium salts (14, 15)
An appropriate heterocycle (2.7 mmol) was added dropwise
to a solution of salt 13 (0.43 g, 1.32 mmol) in dichloromethane
(5 mL) at ꢀ60 8C. The reaction mixture was allowed to warm to
rt and stirred for 24 h at rt. Then the solvent was evaporated, and
the residue was purified by silica gel chromatography
(CH2Cl2:CH3CN, 8:1). Evaporation of solvent resulted in salts
14 and 15:
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(Engl. Transl.) 25 (1989) 1005–1006.
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(2004) 1967–1968.
ꢃ (14): N-Metylpyrrole was used as starting heterocycle;
mixture a:b = 1:1, mp = 110–112 8C;1H NMR (CDCl3): d
3.88 (s, 3H), 4.12 (s, 3H), 6.62–7.61 (m, 6H), 8.21–8.63 (m,
8H). 19F NMR (CDCl3): ꢀ54,0 (s, 3F), ꢀ54.1 (s, 3F), ꢀ150.1
(s, 8F). Anal. calcd for C12H10BF7N2O2S: C, 36.92; H, 2.56;
N 7.18. Found: C, 37.18; H, 2.57; N, 7.20.
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USSR 20 (1984) 2051–2052 (Engl. Transl.).
ꢃ (15): Indole was used as starting heterocycle; mp = 164–
166 8C; 1H NMR (CDCl3): d 7.50 (t, 1H), 7.61 (t, 1H), 7.73