Stereoselective synthesis of fluorobis(phenylsulfonyl)methyl-substituted alkenes using free radical fluoroalkylation

Article abstract of DOI:10.1016/j.jfluchem.2008.04.013

(PhSO₂)₂CFI was prepared in quantitative yield by the iodination of fluorobis(phenylsulfonyl)methane and utilized in facile radical bis(phenylsulfonyl)monofluoromethylation of various terminal alkenes. The synthetic methodology was f

Full text of DOI:10.1016/j.jfluchem.2008.04.013

Journal of Fluorine Chemistry 129 (2008) 1036–1040
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Stereoselective synthesis of fluorobis(phenylsulfonyl)methyl-substituted alkenes
using free radical fluoroalkylation
*
*
G.K. Surya Prakash , Istvan Ledneczki, Sujith Chacko, Shashank Ravi, George A. Olah
Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, 837 Bloom Walk, Los Angeles, CA 90089-1661, United States
A R T I C L E I N F O
A B S T R A C T
Article history:
(PhSO2)2CFI was prepared in quantitative yield by the iodination of fluorobis(phenylsulfonyl)methane
and utilized in facile radical bis(phenylsulfonyl)monofluoromethylation of various terminal alkenes. The
synthetic methodology was further extended for the preparation of monofluoromethyl-substituted
alkenes.
Received 1 April 2008
Received in revised form 29 April 2008
Accepted 30 April 2008
Available online 4 May 2008
ß 2008 Elsevier B.V. All rights reserved.
Dedicated to Prof. Dennis P. Curran on the
occasion of receiving the 2008 American
Chemical Society Award for Creative Work
in Fluorine Chemistry.
Keywords:
Fluoroalkylation
Radical reactions
Stereoselective
1. Introduction
alcohols [4] and also developed a new electrophilic reagent, which
can transfer ‘‘CH2F+’’ to various nucleophiles [6]. Besides electro-
Fluorocarbon molecules possess unique properties leading to
their use in various facets of life [1]. The inductive effect, the
enhancement of metabolic stability and drastic change in binding
affinity and selectivity are major advantages of introducing
fluorine into a drug molecule [2]. This in turn reflects in better
lipophilicity, improved bioavailability and modulated physio-
chemical properties. Its presence has emerged to about 20% in the
drug market including half of the top 10 drugs sold in 2005 over the
past 50 years. This big leap can be attributed to better under-
standing of ‘‘fluorine effects’’ in drug research and also to novel
methodologies to introduce fluorine in various organic molecules.
Compounds with monofluoromethyl group carry significant
importance in biological systems. Monofluoroacetic acid is a lethal
inhibitor for the Kreb’s cycle. Sevoflurane, a new generation of
monofluoromethyl anesthetics has fast uptake and elimination
properties [3]. Various groups have reported methods to introduce
monofluoromethyl group in organic molecules using different
approaches [4]. Our group has focused on developing novel
fluorinating and fluoroalkylating agents for many years [5]. We
recently reported a novel methodology to introduce monofluoro-
methyl group by Mitsunobu reaction of primary and secondary
philic and nucleophilic pathways, radical reaction routes are also of
substantial interest. Radical hydroperfluoroalkylation of alkenes
using perfluoroalkyl halides was reported using copper powder,
Pd(PPh3)4 and Na2SO4 [7]. Hu and co-workers reported the radical
(phenylsulfonyl)difluoromethylation of terminal alkenes [8]. Till
now, to the best of our knowledge, no report exists on radical
bis(phenylsulfonyl)monofluoromethylation. In our continuing
effort on fluoroalkylation, we report now the synthesis of
fluoroiodobis(phenylsulfonyl)methane and its use in the radical
fluoromethylation of terminal alkenes for the preparation of
monofluoromethyl-substituted alkanes and alkenes.
2. Results and discussion
We have previously carried out iodination of phenylsulfonyldi-
fluoromethane in excellent yields using potassium t-butoxide as
the base [9]. Fluorobis(phenylsulfonyl)methane is recognized as
the synthetic equivalent of monofluoromethide species and it can
be easily deprotonated using a milder base such as cesium
carbonate in acetonitrile. Even potassium carbonate in dimethyl-
formamide is a suitable system to facilitate the deprotonation.
Fluoroiodobis(phenylsulfonyl)methane was prepared from fluor-
obis(phenylsulfonyl)methane using iodine in the presence of
cesium carbonate in excellent yield (Scheme 1).
* Corresponding authors. Tel.: +1 213 740 5984.
E-mail address: gprakash@usc.edu (G.K. Surya Prakash).
0022-1139/$ – see front matter ß 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2008.04.013

G.K.S. Prakash et al. / Journal of Fluorine Chemistry 129 (2008) 1036–1040
1037
Table 2
Reaction of terminal alkenes using triethylborane
Scheme 1. Preparation of fluoroiodobis(phenylsulfonyl)methane.
Entry
R
Products
4a
Isolated yield (%)
60
Table 1
Optimization of reaction conditions
1
2
3
4b
4c
15
75
a
Entry
Et3B (equiv.)
Molar ratio (3a:2)
Conditions
Yield (%)b
4
5
6
7
8
4d
4e
4f
15
69
70
40
71
1
2
3
4
5
1
2
2
2
2
2
A
A
B
C
C
33
27
40
56
60
3
1
0.33
1
a
Condition A: bubbling compressed air through the reaction mixture. Condition
B: bubbling air through the reaction mixture. Condition C: reaction is done under air
blanket.
b
Isolated yields.
4g
4h
After establishing an easy and efficient preparation of 2, we
explored its free radical bis(phenylsulfonyl)monofluoromethyla-
tion of terminal alkenes using triethylborane and air to initiate the
reaction. Triethylborane has been extensively used in asymmetric
radical reactions at low temperatures [10]. We explored various
conditions using 1-heptene as the model system and found that
the reaction gave the best yield when carried out under an air
blanket using 1 equiv. of the initiator relative to 2 [7] (Table 1).
After establishing the optimal conditions for the reaction, we
reacted various terminal alkenes to generate their corresponding
adducts in moderate to good yields. The reactions were monitored
using 19F NMR and found to be completed in less than 30 min. The
reaction was found to be applicable towards alkenes bearing
ketones, esters and silyl groups. However, in the case of nitriles,
hydroxyl groups and ethers, the reaction was non-selective and
gave multiple products. Styrene and dienes were found to be
sluggish towards the radical reaction and the desired products
were isolated only in minor amounts (Table 2).
It has been reported that tributyltinhydride can be used for de-
iodination reaction to generate the corresponding alkanes from the
iodoalkanes [9]. In our case, the use of neither Bu3SnH nor
tris(trimethylsilyl)silyl hydride was successful in generating
bis(phenylsulfonyl)monofluoromethyl-substituted alkanes. The
Table 3
Stereoselective synthesis of bis(phenylsulfonyl)monofluoromethyl-substituted alkenes
Entry
1
R
Products
Yield (%)a
60
5a
2
3
4
5
6
5b
5c
5d
5e
5f
63
68
63
38
64
a
Isolated yields.

1038
G.K.S. Prakash et al. / Journal of Fluorine Chemistry 129 (2008) 1036–1040
CH2Cl2 (2 mL) and purged with pure air from a balloon. (Only the
atmosphere of the flask was affected, the air was not bubbled into
the solution.) Meanwhile the solution was cooled down to ꢁ30 8C
and Et3B solution (0.3 mmol, 1 M hexane solution) was added
dropwise via syringe. The reaction mixture was stirred for
additional 30 min at this temperature. After the removal of
volatile solvents under vacuum, the crude product was purified by
gradient silica gel column chromatography (Sorbent silica gel, 65–
250 mesh) using hexane/ethyl acetate as the eluents to give the
desired product 4.
Scheme 2. Stereoselective synthesis of bis(phenylsulfonyl)monofluoromethyl-
substituted alkenes.
adducts from the radical reaction, however, underwent facile
dehydroiodination using 1,5-diazabicyclo[4,3,0]non-5-ene (DBU)
to generate stereoselectively the bis(phenylsulfonyl)monofluor-
omethyl-substituted alkenes in high yields (Scheme 2).
Encouraged by this result, we also investigated a one-pot
stereoselective synthesis of bis(phenylsulfonyl)monofluoro-
methyl-substituted alkenes starting from terminal alkenes. After
completion of the first addition step, the second HI elimination step
can be indeed carried out in one pot without isolation of the
intermediate adduct 4. After screening various conditions, we found
that DBU in toluene at 0 8C gave the desired alkenes in good to
moderate overall yields. The reaction is found to be compatible with
functionalities such as ketones, esters and silyl groups (Table 3).
4.4. Typical one-pot procedure for the preparation of 1-fluoro-1,1-
bis(phenylsulfonyl)alkenes
A flask containing bis(phenylsulfonyl)iodofluoromethane (2)
(0.3 mmol) and the alkene (3) (0.6 mmol) was dissolved in dry
CH2Cl2 (2 mL) and was purged with pure air from a balloon. (Only
the atmosphere of the flask was affected, the air was not bubbled
into the solution.) Meanwhile the solution was cooled down to
ꢁ30 8C and Et3B solution (0.3 mmol, 1 M hexane solution) was
added dropwise via syringe. The reaction mixture was stirred for
additional 30 min at this temperature. After the removal of volatile
solvents under vacuum the residue was dissolved in toluene (5 mL)
and DBU (0.36 mmol) was added dropwise at 0 8C and the solution
was stirred at this temperature for 3 h. After evaporation the
remaining material was purified by gradient silica gel column
chromatography (Sorbent silica gel, 65–250 mesh) using hexane/
ethyl acetate as the eluents to give the desired product 5.
3. Conclusions
We report the preparation of fluoroiodobis(phenylsulfonyl)-
methane and its use for the radical addition to terminal alkenes.
The adducts undergo dehydroiodination to provide the E isomers
of bis(phenylsulfonyl)monofluoromethyl-substituted alkenes in
preparatively acceptable yields in the presence of DBU. This
methodology is found to be compatible with ketones, esters and
silyl functional groups.
4.5. Fluoroiodobis(phenylsulfonyl)methane (2)
1H NMR (CDCl3): 8.03 (m, 4H, J = 7.4 Hz), 7.77 (t, 2H, J = 7.5 Hz),
7.60 (m, 4H). 19F NMR (CDCl3): ꢁ110.56 (s, 1F). 13C NMR (CDCl3):
136.04, 133.09, 131.87, 129.26, 105.28 (d, J(C–F) = 337.8 Hz). HRMS
calcd. for C13H11FIO4S2 441.2628, found 441.2613.
4. Experimental
4.1. General
Unless otherwise mentioned, all reagents were purchased from
commercial sources. 1H, 13C, and 19F NMR spectra were recorded on
Varian Mercury-400 NMR spectrometer. 1H NMR chemical shifts
4.6. 1-Fluoro-3-iodo-1,1-bis(phenylsulfonyl)octane (4a)
1H NMR (CDCl3): 7.94 (m, 4H), 7.76 (m, 2H), 7.60 (m, 4H), 4.46
(m, 1H), 3.21 (dd, 2H, J = 6.0 Hz, J(H–F) = 17 Hz) 1.65 (m, 2H), 1.26
(m, 6H), 0.88 (m, 3H). 19F NMR (CDCl3): ꢁ149.84 (t, 1F, J(H–
F) = 17 Hz). 13C NMR (CDCl3): 135.72, 135.62, 134.56, 134.33,
131.10, 131.0, 129.41, 129.24, 114.78 (d, J(C–F) = 272.3 Hz), 40.95
(d, J = 1.8 Hz), 40.42 (d, J = 16.4 Hz), 30.71, 29.12, 24.86 (d,
J = 3.4 Hz), 22.49, 14.11. HRMS calcd. for C20H25O4FS2I 539.0223,
found 539.0220.
were determined relative tointernal(CH3)4Si (TMS) at 0.00 ppm. 13
C
NMR chemical shifts were determined relative to the 13C signal of
the solvent: CDCl3 (77.16 ppm). CFCl3 was used as internal standard
for 19F NMR. High-resolution mass spectra were recorded in EI+ or
FAB+ mode on a high-resolution mass spectrometer.
4.2. Typical procedure for the preparation of
fluoroiodobis(phenylsulfonyl)methane (2)
4.7. 1-Fluoro-3-iodo-3-phenyl-1,1-bis(phenylsulfonyl)propane (4b)
Into acetonitrile solution (20 mL) of bis(phenylsulfonyl)fluor-
omethane (1) Cs2CO3 (3.2 mmol) was added and stirred for 10 min.
Subsequently, iodine (3.5 mmol) was added to the reaction
mixture and stirred until all starting material was consumed
based on 19F NMR (20 min). The solvent was evaporated and the
remaining material was dissolved in CH2Cl2 (10 mL) and it was
washed with water (2ꢀ 20 mL), 10% Na2S2O3 solution (2ꢀ 20 mL)
and dried using MgSO4. (The water washing should precede the
washing with thiosulfate solution otherwise the starting material
will be recovered.) After evaporation the pure bis(phenylsulfony-
l)iodofluoromethane (2) was isolated in high yield.
1H NMR (CDCl3): 7.97 (m, 2H), 7.90 (m, 2H), 7.75 (m, 2H), 7.58
(m, 4H), 7.29 (m, 5H), 5.40 (dd, 1H, J = 2.1 Hz, J = 9.0 Hz), 2.86 (m,
1H), 2.71 (m, 1H). 19F NMR (CDCl3): ꢁ143.47 (dd, J
¼ 13:2 Hz,
ðH ꢁFÞ
B
JðH
¼ 22:4 Hz). 13C NMR (CDCl3): 142.87, 135.74, 135.68,
ꢁFÞ
A
134.93, 134.58, 131.27, 131.09, 129.40, 129.36, 128.80, 128.09,
125.62, 115.17 (d, J(C–F) = 268.0 Hz), 68.79 (d, J = 6.0 Hz), 40.77 (d,
J = 16.5 Hz). HRMS calcd. for C21H19FO4S2 (MꢁI)+ 417.0631, found
417.0648.
4.8. 1-Fluoro-3-iodo-5-phenyl-1,1-bis(phenylsulfonyl)pentane (4c)
4.3. Typical procedure for the radical addition of
fluoroiodobis(phenylsulfonyl)methane with alkenes
1H NMR (CDCl3) 7.92 (d, 2H, J = 8.5 Hz), 7.84 (d, 2H, J = 8.5 Hz),
7.73 (m, 2H), 7.56 (m, 4H), 7.28 (m, 2H), 7.22 (m, 1H), 7.14 (m, 2H),
4.12 (m, 1H), 3.26 (m, 2H), 2.75 (m, 1H), 2.57 (m, 1H), 1.95 (m, 2H).
19F NMR (CDCl3): ꢁ149.39 (t, 1F, J = 16.6 Hz). 13C NMR (CDCl3):
140.1, 135.6, 135.5, 134.3, 134.1, 130.9, 130.8, 129.3, 129.1, 128.5,
A flask containing fluoroiodobis(phenylsulfonyl)methane (2)
(0.3 mmol) and the alkene (3) (0.6 mmol) was dissolved in dry

G.K.S. Prakash et al. / Journal of Fluorine Chemistry 129 (2008) 1036–1040
1039
128.4, 126.1, 114.6 (d, J = 272 Hz), 42.3, 40.2 (d, J = 16 Hz), 35.5,
23.7. HRMS calcd. for C23H23O4FS2I 573.0067, found 573.0093.
NMR (CDCl3): 144.48, 144.39, 135.29, 135.12, 130.96, 128.96,
114.43, 114.29, 113.23 (d, J(C–F) = 267 Hz), 32.66, 31.13, 27.79,
22.46, 14.03. HRMS calcd. for C20H24FO4S2 411.1100, found
411.1110.
4.9. 7-Fluoro-5-iodo-7,7-bis(phenylsulfonyl)hept-3-ene (4d)
1H NMR (CDCl3): 7.92 (d, 4H, J = 8.5 Hz), 7.73 (t, 2H, J = 7.5 Hz),
4.15. 1-Fluoro-5-phenyl-1,1-bis(phenylsulfonyl)pent-2-ene (5b)
7.57 (m, 4H), 5.60 (m, 2H), 3.97 (m, 1H), 3.14 (m, 2H), 1.50 (m, 2H),
0.89 (m, 3H). 19F NMR (CDCl3): ꢁ142.27 (t, 1F, J(H–F) = 17.1 Hz). 13
C
1H NMR (CDCl3): 7.90 (d, 4H, J = 8.1 Hz), 7.72 (t, 2H, J = 7.5 Hz),
7.55 (t, 4H, J = 8.0 Hz), 7.28 (m, 2H), 7.22 (m, 1H), 7.05 (d, 2H,
J = 7.3 Hz), 6.06 (dd, 1H, J(H–H) = 15.6 Hz, J(H–F) = 22.4 Hz), 5.88 (td,
1H, J = 6.6 Hz, J(H–H) = 15.6 Hz), 2.51 (t, 2H, J = 7.7 Hz), 2.35 (dd, 2H,
J = 7.1 Hz, J = 14.3 Hz). 19F NMR (CDCl3): ꢁ150.97 (d, J(H–
F) = 22.3 Hz). 13C NMR (CDCl3): 143.16, 143.08, 140.51, 135.42,
135.11, 131.08, 129.22, 129.06, 128.52, 126.44, 115.23, 115.09,
113.36 (d, J(C–F) = 267 Hz), 34.43, 34.36. HRMS calcd. for
NMR (CDCl3): 140.05, 139.04, 135.43, 135.38, 131.02, 129.19,
119.49, 119.43, 114.50 (d, J(C–F) = 267.3 Hz), 73.71, 33.49 (d,
J = 18.9 Hz), 29.83, 9.71. HRMS calcd. for C19H20FO4S2 (MꢁI)+
395.0787, found 395.0790.
4.10. 1-Fluoro-3-iodo-1,1-bis(phenylsulfonyl)pentadecane (4e)
1H NMR (CDCl3): 7.94 (dd, 4H, J = 8.5 Hz, J = 17.8 Hz), 7.75 (dd,
2H, J = 7.2 Hz, J = 13.4 Hz), 7.60 (t, 4H, J = 7.3 Hz), 4.28 (m, 1H), 3.21
(dd, 2H, J = 6.1 Hz, J(H–F) = 16.9 Hz), 1.64 (m, 2H), 1.26 (m, 20H),
0.88 (t, 3H, J = 6.8 Hz). 19F NMR (CDCl3): ꢁ149.85 (t, 1F, J(H–
F) = 16.8 Hz). 13C NMR (CDCl3): 135.73, 135.64, 134.4, 134.2,
131.17, 131.1, 129.44, 129.26, 114.79 (d, J(C–F) = 272.3 Hz), 41.05,
40.54, 40.37, 32.06, 29.79, 29.76, 29.68, 29.50, 28.62, 24.91 (d,
J = 3.3 Hz), 22.84, 14.28. HRMS calcd. for C27H39O4FS2I 637.1319,
found 637.1317
C23H22O4FS2 445.0944, found 445.0934.
4.16. 1-Fluoro-1,1-bis(phenylsulfonyl)pentadec-2-ene (5c)
1H NMR (CDCl3): 7.93 (d, 4H, J = 8.4 Hz), 7.71 (t, 2H, J = 7.5 Hz),
7.56 (t, 4H, J = 7.9 Hz), 5.98 (dd, 1H, J(H–H) = 15.7 Hz, J(H–
F) = 22.5 Hz), 5.81 (dt, 1H, J = 6.8 Hz, J(H–H) = 15.7 Hz), 2.01 (dd,
2H, J = 6.8 Hz, J = 13.7 Hz), 1.26 (m, 20H), 0.88 (t, 3H, J = 6.8 Hz). 19
F
NMR (CDCl3): ꢁ150.68 (d, J(H–F) = 22.5 Hz). 13C NMR (CDCl3):
144.44, 144.36, 135.26, 135.06, 130.91, 128.93, 114.40, 114.26,
113.31 (d, J(C–F) = 266.9 Hz), 32.69, 32.01, 29.77, 29.74, 29.73,
29.57, 29.45, 29.43, 29.00, 28.11, 22.79, 14.24. HRMS calcd. for
4.11. 7-Fluoro-5-iodo-7,7-bis(phenylsulfonyl)heptan-2-one (4f)
1H NMR (CDCl3): 7.92 (t, 4H, J = 8.7 Hz), 7.76 (q, 2H, J = 7.3 Hz),
7.59 (t, 4H, J = 7.8 Hz), 4.35 (m, 1H), 3.21 (m, 2H), 2.56 (m, 2H), 2.14
(s, 3H), 2.00 (m, 1H), 1.90 (m, 1H). 19F NMR (CDCl3): ꢁ149.14 (t, 1F,
J(H–F) = 16.8 Hz). 13C NMR (CDCl3): 206.78, 135.77, 135.72, 134.32,
134.26, 131.13, 131.10, 129.44, 129.31, 114.68 (d, J(C–
F) = 272.5 Hz), 43.66, 40.42 (d, J = 16.4 Hz), 34.69 (d, J = 2.4 Hz),
30.19, 23.16 (d, J = 3.4 Hz). HRMS calcd. for C19H21O5FS2I 538.9859,
found 538.9847.
C27H38O4FS2 509.2196, found 509.2213.
4.17. 7-Fluoro-7,7-bis(phenylsulfonyl)-hept-6-en-2-one (5d)
1H NMR (CDCl3): 7.92 (d, 4H, J = 8.4 Hz), 7.73 (t, 2H, J = 7.5 Hz),
7.57 (t, 4H, J = 8.0 Hz), 6.02 (tdd, 1H, J = 1.4 Hz, J(H–H) = 15.6 Hz, J(H–
F) = 22.2 Hz), 5.82 (td, 1H, J = 6.6 Hz, J(H–H) = 15.7 Hz), 2.39 (t, 2H,
J = 6.9 Hz), 2.28 (dd, 2H, J = 6.7 Hz, J = 13.7 Hz), 2.10 (s, 3H). 19F
NMR (CDCl3): ꢁ150.83 (d, 1F, J(H–F) = 22.3 Hz). 13C NMR (CDCl3):
206.54, 142.35, 142.26, 135.36, 134.94, 130.96, 128.99, 115.45,
115.27, 113.17 (d, J(C–F) = 267.2 Hz), 41.38, 30.05, 26.39. HRMS
calcd. for C19H20FO5S2 411.0736, found 411.0733.
4.12. Ethyl-6-fluoro-4-iodo-6,6-bis(phenylsulfonyl)hexanoate (4g)
1H NMR (CDCl3): 7.94 (t, 4H), 7.76 (m, 2H), 7.59 (m, 4H), 4.37
(m, 1H), 4.13 (q, 2H, J = 7.2 Hz), 3.23 (m, 2H), 2.40 (m, 2H), 2.06 (m,
1H), 1.94 (m, 1H), 1.26 (t, 3H, J = 7.2 Hz). 19F NMR (CDCl3): ꢁ149.42
(t, J(H–F) = 16 Hz). 13C NMR (CDCl3): 172.14, 135.78, 135.72, 131.15,
131.13, 130.31, 129.63, 129.45, 129.31, 114.66 (d, J(C–
F) = 272.2 Hz), 60.78, 40.48 (d, J = 16.4 Hz), 35.99, 34.64, 22.86,
14.33. HRMS calcd. for C20H23O6FS2I 568.9965, found 568.9979.
4.18. Ethyl-6-fluoro-6,6-bis(phenylsulfonyl)hex-2-enoate (5e)
1H NMR (CDCl3): 7.92 (d, 4H, J = 7 Hz), 7.30 (t, 2H, J = 7 Hz), 7.57
(t, 4H, J = 8 Hz), 6.05 (dd, 1H, J = 23 Hz, J(H–H) = 15.8 Hz), 5.40 (m,
1H), 4.13 (q, 2H, J = 7 Hz), 2.36 (m, 2H), 2.23 (m, 2H), 1.26 (m, 3H).
19F NMR (CDCl3): ꢁ150.83 (t, 1F, J(H–F) = 22.5 Hz). 13C NMR (CDCl3):
172.04, 141.78, 141.69, 135.37, 134.93, 130.98, 128.98, 115.82,
115.68, 113.13 (d, J(C–F) = 267 Hz), 60.84, 32.44, 27.7, 14.29. HRMS
calcd. for C20H22FO6S2 441.0842, found 441.0841.
4.13. 1-Fluoro-1,1-bis(phenylsulfonyl)-3-iodo-3-
trimethylsilylpropane (4h)
1H NMR (CDCl3): 8.03 (d, 2H, J = 8.5 Hz), 7.82 (d, 2H, J = 8.5 Hz),
7.73 (td, 2H, J = 7.5 Hz, J = 20.8 Hz), 7.58 (td, 4H, J = 7.9 Hz,
J = 14.0 Hz), 3.54 (ddd, 1H, J = 1.9 Hz, J = 17.8 Hz, J(H–F) = 24.6 Hz),
3.40 (dd, 1H, J = 1.9 Hz, J = 10.2 Hz), 2.76 (ddd, 1H, J = 3.1 Hz,
J = 10.2 Hz, J = 17.8 Hz), 0.18 (s, 9H). 19F NMR (CDCl3): ꢁ151.76 (d,
1F, J(H–F) = 24.5 Hz). 13C NMR (CDCl3): 135.64, 135.49, 135.17,
133.44, 131.29, 131.15, 129.40, 129.05, 114.37 (d, J(C–
F) = 273.4 Hz), 34.15 (d, J = 17.7 Hz), 6.06 (d, J = 3.2 Hz), ꢁ2.32.
HRMS calcd. for C18H23O4FSiS2I 540.9836, found 540.9841.
4.19. 1-Fluoro-1,1-bis(phenylsulfonyl)-3-trimethylsilylprop-2-ene
(5f)
1H NMR (CDCl3): 7.91 (td, 4H, J = 1.1 Hz, J = 8.6 Hz), 7.71 (t, 2H,
J = 7.5 Hz), 7.55 (dd, 4H, J = 7.5 Hz, J = 8.1 Hz), 6.42 (dd, 1H, J(H–
H) = 19.0 Hz, J(H–F) = 20.2 Hz), 6.05 (d, 1H, J(H–H) = 19.0 Hz), ꢁ0.05 (s,
9H). 19F NMR (CDCl3): ꢁ151.65 (d, 1F, J(H–F) = 20.3 Hz). 13C NMR
(CDCl3): 144.65, 144.61, 135.35, 135.03, 130.95, 130.94, 128.92,
128.18, 128.01, 112.97 (d, J(C–F) = 266.8 Hz), ꢁ1.94. HRMS calcd. for
4.14. 1-Fluoro-1,1-bis(phenylsulfonyl)-oct-2-ene (5a)
C18H22FO4S2Si 413.0713, found 413.0710.
1H NMR (CDCl3): 7.92 (m, 4H), 7.71 (m, 2H), 7.56 (m, 4H), 5.98
(ddt, 1H, J = 1.4 Hz, J(H–H) = 15.6 Hz, J(H–F) = 22.2 Hz), 5.83 (dt, 1H,
J = 7.1 Hz, J(H–H) = 15.5 Hz), 2.51 (m, 2H), 1.23 (m, 4H), 1.08 (m, 2H),
0.83 (m, 3H). 19F NMR (CDCl3): ꢁ150.67 (d, J(H–F) = 22.2 Hz). 13C
Acknowledgment
Support of our work by the Loker Hydrocarbon Research
Institute is gratefully acknowledged.

1040
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(e) G.K.S. Prakash, C. Weber, S. Chacko, G.A. Olah, J. Comb. Chem. 9 (2007) 920–
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