Fluoride-induced nucleophilic (phenylthio)difluoromethylation of carbonyl compounds with [difluoro(phenylthio)methyl]trimethylsilane (TMS-CF 2SPh)

Article abstract of DOI:10.1016/j.jfluchem.2004.12.005

A fluoride-induced nucleophilic (phenylthio)difluoromethylation method using TMS-CF₂SPh has been achieved. This new methodology efficiently transfers "PhSCF₂" group into both enolizable and non-enolizable aldehydes and ketones to giv

Full text of DOI:10.1016/j.jfluchem.2004.12.005

Journal of Fluorine Chemistry 126 (2005) 529–534
www.elsevier.com/locate/fluor
Fluoride-induced nucleophilic (phenylthio)difluoromethylation of
carbonyl compounds with [difluoro(phenylthio)methyl]trimethylsilane
(TMS–CF2SPh)
*
G.K. Surya Prakash , Jinbo Hu, Ying Wang, George A. Olah
Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1661, USA
Received 7 December 2004; accepted 9 December 2004
Available online 12 January 2005
Dedicated to Professor Richard D. Chambers on the occasion of his 70th birthday.
Abstract
A fluoride-induced nucleophilic (phenylthio)difluoromethylation method using TMS–CF2SPh has been achieved. This new methodology
efficiently transfers ‘‘PhSCF2’’ group into both enolizable and non-enolizable aldehydes and ketones to give corresponding (phenylthio)di-
fluoromethylated alcohols in good to excellent yields. Diphenyldisulfide can also be (phenylthio)difluoromethylated into PhSCF2SPh in high
yield. The reaction with methyl benzoate, however, gives only low yield of (phenylthio)difluoromethyl phenyl ketone. The above-obtained
PhSCF2-containing alcohols can be further transformed into difluoromethyl alcohols using an oxidation–desulfonylation procedure. This new
type of nucleophilic (phenylthio)difluoromethylation methodology may have other potential applications in the medicinal and agrochemical
fields.
# 2004 Elsevier B.V. All rights reserved.
Keywords: [Difluoro(phenylthio)methyl]trimethylsilane; (Phenylthio)difluoromethylation; Carbonyl compounds; Fluoride; Autocatalytic reaction
1. Introduction
In 1989, we developed the first general and efficient
nucleophilic trifluoromethylation method using (trifluoro-
methyl)trimethylsilane (TMS–CF3) [3–5]. With a similar
protocol, fluoride-induced nucleophilic chlorodifluorometh
ylation with TMS–CF2Cl, (trimethylsilyl)difluoromethyla-
tion with TMSCF2TMS, and perfluorovinylation with TMS
CF2CF2TMS have been developed in our laboratory [6].
Herein, we would like to disclose another nucleophilic
fluoroalkylation methodology in this category, using
[difluoro(phenylthio)methyl]trimethylsilane (TMS–CF2S-
Ph) as the nucleophilic (phenylthio)difluoromethylating
reagent.
Recently, the selective introduction of difluoro(arylthio)-
methyl or difluoro(heteroarylthio)methyl group (ArSCF2)
into organic molecules has been found to be attractive, since
these compounds have potential biological applications such
as anti-HIV-1 reverse transcriptase inhibitors and other
agrochemical intermediates [1,2]. The currently known
methods to construct the ArSCF2 moiety are based on the
SRN1 reactions between an aryl- or heteroarylthiolate
(ArSNa) and a halodifluoromethyl-containing compound
(halo = Br, Cl) [1,2]. To our best knowledge, there is no
synthetic method available so far for the direct introduction
of a difluoro(arylthio)methyl (ArSCF2) building block into
organic molecules.
2. Results and discussion
[Difluoro(phenylthio)methyl]trimethylsilane (TMS–CF2
SPh) was prepared for the first time by us as a high-boiling
and reasonably stable liquid (b.p. 86–87 8C/4 mmHg), using
* Corresponding author. Tel.: +1 213 740 5984;
fax: +1 213 740 6270/6679.
E-mail address: gprakash@usc.edu (G.K. Surya Prakash).
0022-1139/$ – see front matter # 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2004.12.005

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G.K.S. Prakash et al. / Journal of Fluorine Chemistry 126 (2005) 529–534
Scheme 1. Preparation of TMS–CF2SPh.
the Barbier coupling reaction of bromodifluoromethyl
phenyl sulfide (1), magnesium metal and chlorotrimethylsi-
lane (TMSCl) in 85% isolated yield (Scheme 1) [7]. Since
compound 1 can be readily prepared from dibromodifluoro-
methane (Halon 1202) and sodium benzenethiolate [8],
TMS–CF2SPh is an inexpensive chemical and can be widely
used.
desulfonylation procedure (Scheme 4). Difluoromethyl
alcohols are highly useful compounds for many applications
[9].
Concerning the mechanism of this fluoride-induced
(phenylthio)difluoromethylation of carbonyl compounds
(both aldehydes and ketones), we propose that a penta-
covalent silicon anion species 11 is formed from TMS–
CF2SPh and TBAT (Scheme 5). Species 11 acts as a real
(phenyltꢀhio)difluoromethylating agent, transferring the
PhSCF2 into the carbonyl compound 2 to give alkoxide
12. Alkoxide 12 can further act as an initiator for TMS–
CF2SPh to form another pentacovalent silicon species 13
as a (phenylthio)difluoromethylating agent, thus giving
the silylated carbinol product 3 from TMS–CF2SPh and
carbonyl compounds 2 in a catalytic cycle (Scheme 5).
In principle, the reaction is a fluoride-induced autocatalytic
process, and such a mechanism has been previously
proposed by us in the case of TMS–CF3 [3].
The reaction conditions for the fluoride-induced nucleo-
philic (phenylthio)difluoromethylation reaction (Scheme 2)
is similar to that of trifluoromethylation with TMS–CF3
[3,4]. Catalytic amount (10 mol.%) of tetrabutylammonium
triphenyldifluorosilicate (TBAT) was used as the anhydrous
fluoride source. The results are summarized in Table 1.
As shown in Table 1, various aldehydes and ketones were
(phenylthio)difluoromethylated in good to excellent yields
with this method. Enolizable carbonyl compounds behave
similarly as non-enolizable ones, with slightly lower yields
(see entries 7 and 8). In the case of an a,b-unsaturated
carbonyl compound, only 1,2-addition product was obtained
(entry 5).
Table 1
This new type of (phenylthio)difluoromethylation
method was also applied to other systems such as disulfides
and esters. For example, when excess potassium tert-
butoxide was used as the promoter, diphenyl disulfide (5)
reacted with TMS–CF2SPh to give product 6 in 85% yield
(Scheme 3, Eq. (1)). The reaction between methyl benzoate
(7) and TMS–CF2SPh was attempted several times using
different solvents at ꢀ78 8C to room temperature, and the
ketone product 8 was produced in 28–41% conversions
(Scheme 3, Eq. (2)).
Nucleophilic (phenylthio)difluoromethylation of carbonyl compounds with
TMS–CF2SPh (after desilylation)
Entry Carbonyl compounds 2 Product 4
Yield (%)a
1
85
2
87
The above-obtained (phenylthio)difluoromethyl carbi-
nols (4) can also be further transformed into difluoromethyl
carbinols (10), using simple oxidation and reductive
3
4
72
81
5
6
7
91
86
82
8
77
Scheme 2. Nucleophilic (phenylthio)difluoromethylation with TMS–
a
CF2SPh.
Isolated yield.

G.K.S. Prakash et al. / Journal of Fluorine Chemistry 126 (2005) 529–534
531
Scheme 3. (Phenylthio)difluoromethylation of diphenyl disulfide and methyl benzoate.
Scheme 4. Preparation of difluoromethyl alcohols (10) from 4.
Scheme 5. Proposed mechanism of the (phenylthio)difluoromethylation of carbonyl compounds with TMS–CF2SPh.
3. Conclusion
transfers PhSCF2 group into both enolizable and non-
enolizable aldehydes and ketones to give the corresponding
(phenylthio)difluoromethylated carbinols in good to excel-
lent yields. Diphenyldisulfide can also be (phenylthio)-
difluoromethylated into PhSCF2SPh in high yield. The
In conclusion, a fluoride-induced nucleophilic (phe-
nylthio)difluoromethylation method using TMS–CF2SPh
has been achieved. This new methodology efficiently

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G.K.S. Prakash et al. / Journal of Fluorine Chemistry 126 (2005) 529–534
2
reaction with methyl benzoate, however, gives only low
yield of (phenylthio)difluoromethyl phenyl ketone. The
above-obtained PhSCF2-containing alcohols can be further
transformed into difluoromethyl alcohols using oxidation–
desulfonylation procedure. This nucleophilic fluoroalkyla-
tion chemistry can also be extended to other (arylthio)-
difluoromethylation, (heteroarylthio)difluoromethylation
and (alkylthio)difluoromethylation using corresponding
TMS–CF2SR reagents, which are still under investigation
in our laboratory.
(m, 10H, Ph). 13C NMR (CDCl3): d 76.0 (t, JC–F = 28 Hz,
3
CF2CH), 125.7 (t, JC–F = 2.6 Hz, Ph), 127.7 (Ph), 128.3
(Ph), 128.8 (t, 1JC–F = 285 Hz, CF2), 128.9 (Ph), 129.0 (Ph),
129.8 (Ph), 135.2 (Ph), 136.4 (Ph). 19F NMR (CDCl3): d
ꢀ81.7 (dd, 2JF–F = 210 Hz, 3JF–H = 8.2 Hz, 1F), ꢀ85.2 (dd,
2JF–F = 210 Hz, 3JF–H = 12 Hz, 1F). MS: 266 [M+], 160, 107,
77. HRMS (EI): m/z calcd for C14H12F2OS [M+] 266.0577,
found 266.0575.
4.2.2. 2,2-Difluoro-2-phenylthio-1-(2-naphthyl)ethanol (4b)
1
Pale yellow solid, 87% yield. H NMR (CDCl3): d 3.01
(d, 3JH–H = 3.5 Hz, 1H, OH), 5.20 (m, 1H, CF2–CH), 7.28–
2
4. Experimental
8.00 (m, 12H, aryl). 13C NMR (CDCl3): d 76.0 (t, JC–
F = 27 Hz, CF2CH), 124.9 (t, 3JC–F = 1.4 Hz, aryl), 125.8 (t,
3JC–F = 2.3 Hz, aryl), 126.2 (aryl), 126.5 (aryl), 127.5 (aryl),
127.6 (aryl), 128.0 (aryl), 128.2 (aryl), 129.0 (aryl), 129.0 (t,
1JC–F = 264 Hz, CF2), 129.8 (aryl), 132.6 (aryl), 132.8
(aryl), 133.5 (aryl), 136.4 (aryl). 19F NMR (CDCl3): d ꢀ81.3
4.1. General
Unless otherwise mentioned, all reagents were purchased
from commercial sources. TMS–CF2SPh was prepared
according to our previous procedures [7]. THF was distilled
under nitrogen over sodium/benzophenone ketyl prior to
use. Toluene was distilled over sodium. Column chromato-
graphy was carried out using silica gel (60–200 mesh).
1H, 13C, 19F NMR spectra were recorded on Bruker AMX
500 and Varian Mercury-400 NMR spectrometers. (CH3)4Si
2
3
2
(dd, JF–F = 210 Hz, JF–H = 8 Hz, 1F), ꢀ84.6 (dd, JF–
3
F = 210 Hz, JF–H = 12 Hz, 1F). MS: 316 [M+], 187, 157,
129, 77. HRMS (EI): m/z calcd for C18H14F2OS [M+]
316.0733, found 316.0730.
4.2.3. 2,2-Difluoro-2-phenylthio-1-(40-
chlorophenyl)ethanol (4c)
(TMS) was used as an internal standard for H and 13C
1
NMR, CFCl3 was used as internal standard for 19F NMR. For
some cases, CDCl3 was used as the internal standard for 1H
NMR (7.26 ppm) and 13C NMR (77 ppm). Mass spectra
were obtained on a Hewlett Packard 5890 Gas Chromato-
graph equipped with a Hewlett Packard 5971 Mass Selective
Detector at 70 eV. HRMS data were recorded on a VG 7070
high-resolution mass spectrometer. The purity of the isolated
products (usually >97% purity) was examined by GC–MS
White solid, 72% yield. 1H NMR (CDCl3): d 3.08 (d, 3JH–
H = 4.2 Hz, 1H, OH), 4.97 (m, 1H, CF2–CH), 7.35–7.60 (m,
2
9H, aryl). 13C NMR (CDCl3): d 75.4 (t, JC–F = 27.3 Hz,
CF2CH), 125.5 (t, 3JC–F = 2.2 Hz, aryl), 128.5 (aryl), 128.7
1
(t, JC–F = 285 Hz, CF2), 129.1 (aryl), 129.2 (aryl), 130.0
(aryl), 133.6 (aryl), 135.0 (aryl), 136.4 (aryl). 19F NMR
(CDCl3): d ꢀ81.4 (dd, 2JF–F = 210 Hz, 3JF–H = 7.2 Hz, 1F),
2
3
ꢀ85.2 (dd, JF–F = 210 Hz, JF–H = 11.5 Hz, 1F). HRMS
(EI): m/z calcd for C14H11ClF2OS [M+] 300.0187, found
300.0179.
1
and H, 13C, 19F NMR spectroscopy.
4.2. Typical procedures for the nucleophilic
(phenylthio)difluoromethylation with TMS–CF2SPh
4.2.4. 2,2-Difluoro-2-phenylthio-1-(40-
bromophenyl)ethanol (4d)
1
Pale yellow solid, 81% yield. H NMR (CDCl3): d 2.84
Under an argon atmosphere, into a Schlenk flask
containing benzaldehyde (106 mg, 1.0 mmol) and TMS–
CF2SPh (278 mg, 1.2 mmol) in dry THF (5 mL) at 0 8C, was
added dropwise a THF solution (3 mL) of TBAT (54 mg,
0.1 mmol). Then the reaction mixture was stirred at 0 8C for
1 h, followed by stirring at room temperature overnight. A
wet THF solution (10 mL, containing 10% of water) of
TBAFꢁ3H2O (315 mg, 1 mmol) was then added and the
whole mixture was stirred for another 30 min. The THF
solvent was removed under vacuum, and the residue was
purified by silica gel column chromatography (hexane:ethyl
acetate (v/v) = 9:1, then 7:1) to give the 2,2-difluoro-2-
phenylthio-1-phenylethanol (4a) as a colorless liquid, yield:
226 mg (85%).
3
(d, JH–H = 4 Hz, 1H, OH), 4.96 (m, 1H, CF2–CH), 7.35–
7.60 (m, 9 H, aryl). 13C NMR (CDCl3): d 75.5 (t, JC–
2
F = 27.3 Hz, CF2CH), 123.3 (aryl), 125.4 (aryl), 128.6 (t,
1JC–F = 285 Hz, CF2), 129.1 (aryl), 129.4 (aryl), 130.0
(aryl), 131.5 (aryl), 134.0 (aryl), 136.4 (aryl). 19F NMR
(CDCl3): d ꢀ81.6 (dd, 2JF–F = 211 Hz, 3JF–H = 7.3 Hz, 1F),
2
3
ꢀ85.7 (dd, JF–F = 211 Hz, JF–H = 11.4 Hz, 1F). HRMS
(EI): m/z calcd for C14H11BrF2OS [M+] 343.9682, found
343.9681.
4.2.5. 1,1-Difluoro-1-phenylthio-4-phenyl-but-
3-en-2-ol (4e)
Pale yellow liquid, 91% yield. 1H NMR (CDCl3): d 3.13
3
(d, JH–H = 5.4 Hz, 1H, OH), 4.59 (m, 1H, CF2–CH), 6.26
3
(dd, JH–H = 16.1 Hz, JH–H = 6.3 Hz, 1H, PhCH = CH–
3
4.2.1. 2,2-Difluoro-2-phenylthio-1-phenylethanol (4a)
Colorless liquid, 85 % yield. 1H NMR (CDCl3): d 2.71 (d,
3JH–H = 4 Hz, 1H, OH), 4.92 (m, 1H, CF2–CH), 7.21–7.51
3
CH), 6.77 (d, JH–H = 16 Hz, 1H, PhCH = CH–CH), 7.31
(m, 8H, aryl), 7.60 (d, 3JH–H = 7.8 Hz, 2H, aryl). 13C NMR

G.K.S. Prakash et al. / Journal of Fluorine Chemistry 126 (2005) 529–534
533
(CDCl3): d 75.0 (t, 2JC–F = 27 Hz), 122.4 (–CH=CH–), 125.7
1H NMR (CDCl3): d 7.33 (tt, J = 7.3 Hz, 2.0 Hz, 4H, aryl),
7.39 (tt, J = 7.3 Hz, 2.0 Hz, 2H, aryl), 7.58 (d, J = 8.0 Hz,
3
(t, JC–F = 2.5 Hz, aryl), 126.8 (aryl), 128.3 (aryl), 128.5
1
(aryl), 128.9 (t, JC–F = 285 Hz, CF2), 129.0 (aryl),
3
4H, aryl). 13C NMR (CDCl3): d 127.2 (t, JC–F = 14 Hz),
1
129.1 (aryl), 130.2 (aryl), 132.3 (t, JC–F = 315 Hz), 136.1
129.8 (aryl), 135.1 (–CH=CH–), 135.7 (aryl), 136.4 (aryl).
2
19F NMR (CDCl3): d ꢀ83.0 (dd, JF–F = 207.6 Hz,
(aryl). 19F NMR (CDCl3): d ꢀ49.5 (s). MS: 268 [M+], 159,
2
3
3JF–H = 9.2 Hz, 1F), ꢀ84.8 (dd, JF–F = 207.8 Hz, JF–
H = 8.9 Hz, 1F). HRMS (EI): m/z calcd for C16H14F2OS
[M+] 292.0733, found 292.0728.
109, 77.
4.4. Preparation of difluoromethylated alcohols (10) from
(phenylthio)difluoromethylated alcohols (4)
4.2.6. 2,2-Difluoro-2-phenylthio-1,1-diphenylethanol (4f)
White solid, 86% yield. 1H NMR (CDCl3): d 3.16 (b, 1H,
OH), 7.29–7.62 (m, 15H, aryl). 13C NMR (CDCl3): d 81.5 (t,
Compound 4a (or 4b) (1 equiv.) was oxidized with 30%
aqueous H2O2 (4 equiv.) in acetic acid at 50 8C overnight.
After a standard workup, the neutralized crude product 9a
(or 9b) was added into a mixture of Na(Hg) amalgam
(5 wt.% Na in Hg, 5 equiv.) and MeOH at ꢀ20 8C, and the
mixture was stirred at ꢀ20 8C to room temperature for 1 h.
The liquid phase was decanted, and the solid residue was
washed with ether for 3 times. After solvent removal of the
combined organic phase, the residue was purified by silica
gel column chromatography (hexane/ethyl acetate (v/
v) = 5:1) to give product 10a (or 10b) in 49 and 53% yield,
respectively. The characterization data of 10a are consistent
3
2JC–F = 24 Hz, CF2C–), 126.2 (t, JC–F = 2 Hz, aryl), 127.7
3
(t, JC–F = 2 Hz, aryl), 127.9 (aryl), 128.2 (aryl), 128.9
1
(aryl), 129.7 (aryl), 131.1 (t, JC–F = 293 Hz, CF2), 136.6
(aryl), 140.2 (aryl). 19F NMR (CDCl3): d ꢀ77.9 (s). MS: 342
[M+], 213, 183, 165, 105, 77. HRMS (EI): m/z calcd for
C20H16F2OS [M+] 342.0890, found 342.0899.
4.2.7. 2,2-Difluoro-2-phenylthio-1-methyl-1-phenylethanol
(4g)
Colorless liquid, 82% yield. 1H NMR (CDCl3): d 1.83 (s,
3H, CH3), 2.64 (b, 1H, OH), 7.32–7.68 (m, 10H, aryl). 13
C
1
with the previous report [10]. For product 10b: H NMR
NMR (CDCl3): d 24.5 (t, 3JC–F = 2.4 Hz, CH3), 77.9 (t, 2JC–
(CDCl3): d 2.99 (b, 1H, OH), 4.98 (m, 1H, CF2CH), 5.86 (td,
J = 56 Hz, 4.7 Hz, 1H, CF2H), 7.50 (m, 3H, aryl), 7.87 (m,
3
F = 24.4 Hz, CF2C–), 126.1 (t, JC–F = 2.2 Hz, aryl), 126.3
(aryl), 128.1 (aryl), 128.2 (aryl), 128.8 (aryl), 129.6 (aryl),
131.0 (t, 1JC–F = 290 Hz, CF2), 136.5 (aryl), 140.0 (aryl). 19
2
4H, aryl). 13C NMR (CDCl3): d 73.7 (t, JC–F = 24.6 Hz,
F
CF2CH), 115.8 (t, 1JC–F = 246 Hz, CF2), 124.3 (aryl), 126.4
(aryl), 126.5 (aryl), 126.6 (aryl), 127.7 (aryl), 128.1 (aryl),
NMR (CDCl3): d ꢀ82.1 (d, 2JF–F = 204.5 Hz, 1F), ꢀ84.9 (d,
2JF–F = 204.5 Hz, 1F). HRMS (EI): m/z calcd for
C15H14F2OS [M+] 280.0733, found 280.0727.
3
128.4 (aryl), 133.0 (aryl), 133.2 (t, JC–F = 3.5 Hz, aryl),
2
133.5 (aryl). 19F NMR (CDCl3): d ꢀ127.4 (ddd, JF–
2
3
F = 284 Hz, JF–H = 56 Hz, JF–H = 9 Hz, 1F, CF2H),
ꢀ128.0 (ddd, 2JF–F = 284 Hz, 2JF–H = 56 Hz, 3JF–
H = 10 Hz, 1F, CF2H). MS: 208 [M+].
4.2.8. 1-Difluoro(phenylthio)methylcyclohexanol (4h)
1
Colorless liquid, 77% yield. H NMR (CDCl3): d 1.19–
1.88 (m, 11H, 5CH2 and 1CH), 7.34–7.63 (m, 5H, Ph). 13
C
3
NMR (CDCl3): d 20.8 (CH2), 25.3 (CH2), 31.0 (t, JC–
F = 2.2 Hz, CF2–C–CH2), 75.9 (t, 2JC–F = 23.3 Hz, CF2–C),
Acknowledgement
3
126.2 (t, JC–F = 2.4 Hz, aryl), 128.9 (aryl), 129.6 (aryl),
132.1 (aryl), 136.7 (aryl). 19F NMR (CDCl3): d ꢀ87.6 (s).
HRMS (EI): m/z calcd for C13H16F2OS [M+] 258.0890,
found 258.0894.
Support of our work by the Loker Hydrocarbon Research
Institute is gratefully acknowledged.
4.3. Nucleophilic (phenylthio)difluoromethylation of
diphenyl disulfide
References
[1] C.R. Burkholder, W.R. Dolbier Jr., M. Medebielle, J. Fluorine Chem.
102 (2000) 369–376.
Under an argon atmosphere, into a Schlenk flask
containing diphenyl disulfide (218 mg, 1.0 mmol) and
TMS–CF2SPh (464 mg, 2.0 mmol) in dry THF (7 mL) at
0 8C, was added dropwise a THF solution (3 mL) of t-BuOK
(336 mg, 3.0 mmol). Then the reaction mixture was stirred
at 0 8C to room temperature for 2 h, followed by quenching
with saturated NaCl aqueous solution (10 mL). The mixture
was extracted with ether (15 mL ꢂ 3), and the combined
organic phase was dried over MgSO4. After the removal of
volatile solvents, the residue was further purified by silica
gel column chromatography (using hexane as eluent) to give
PhSCF2SPh (6) as a colorless liquid, yield: 227 mg (85%).
[2] C. Burkholder, W.R. Dolbier Jr., M. Medebielle, S. Ait-Mohand,
Tetrahedron Lett. 42 (2001) 3459–3462.
[3] G.K.S. Prakash, R. Krishnamurti, G.A. Olah, J. Am. Chem. Soc. 111
(1989) 393–395.
[4] R. Krishnamurti, D.R. Bellew, G.K.S. Prakash, J. Org. Chem. 56
(1991) 984–989.
[5] G.K.S. Prakash, A.K. Yudin, Chem. Rev. 97 (1997) 757–786;
G.K.S. Prakash, M. Mandal, J. Fluorine Chem. 112 (2001) 123–131;
G.K.S. Prakash, J. Hu, New Fluoroalkylation Chemistry, in: V.
Soloshonok (Ed.), Fluorinated Synthons, ACS Symposium Series,
2005.
[6] A.K. Yudin, G.K.S. Prakash, D. Deffieux, M. Bradley, R. Bau, G.A.
Olah, J. Am. Chem. Soc. 119 (1997) 1572–1581.

534
G.K.S. Prakash et al. / Journal of Fluorine Chemistry 126 (2005) 529–534
[7] G.K.S. Prakash, J. Hu, G.A. Olah, J. Org. Chem. 68 (2003) 4457–
[9] P. Kirsch, Modern Fluoroorganic Chemistry: Synthesis, Reactivity
Applications, Wiley-VCH, Weinheim, 2004.
[10] S. Kaneko, T. Yamazaki, T. Katazume, J. Org. Chem. 58 (1993) 2302–
2312.
4463.
[8] X.-Y. Li, X. Jiang, Y. Gong, H. Pan, HuaXue XueBao 43 (1985) 260–
265.