Preparation of 1,1-difluoroalkanes from aldehydes via 1,1-bistriflates: Advantageous use of HF-Lewis base reagents

Article abstract of DOI:10.1016/j.jfluchem.2014.06.020

Alkane-1,1-bistriflates, prepared in excellent yields by reaction of aldehydes with triflic anhydride, are converted to their respective 1,1-difluoroalkanes in good to excellent yield through reaction with fluorinating agent, triethylaminetrishydrofluorid

Full text of DOI:10.1016/j.jfluchem.2014.06.020

Accepted Manuscript
Title: Preparation of 1,1-Difluoroalkanes from Aldehydes via
1,1-bis-triflates.Advantageous Use of HF-Lewis Base
Reagents
Author: William R. Dolbier Jr. Masamune Okamoto
PII:
S0022-1139(14)00175-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jfluchem.2014.06.020
FLUOR 8349
To appear in:
FLUOR
Received date:
Revised date:
Accepted date:
9-4-2014
20-6-2014
21-6-2014
Please cite this article as: W.R. Dolbier Jr., M. Okamoto, Preparation
of 1,1-Difluoroalkanes from Aldehydes via 1,1-bis-triflates.Advantageous
Use of HF-Lewis Base Reagents, Journal of Fluorine Chemistry (2014),
http://dx.doi.org/10.1016/j.jfluchem.2014.06.020
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Fluorine Chemistry
Manuscript Number: FLUOR-D-14-00092R1
Title: Preparation of 1,1-Difluoroalkanes from Aldehydes via 1,1-bis-
triflates. Advantageous Use of HF-Lewis Base Reagents
Article Type: SI: Umemoto Issue
Keywords: deoxofluorination
gem-difluoroalkanes
HF-Lewis base reagents
Corresponding Author: Prof. William R. Dolbier Jr., Ph.D
Corresponding Author's Institution: University of Florida
First Author: William R. Dolbier Jr., Ph.D
Order of Authors: William R. Dolbier Jr., Ph.D; Masamune Okamoto, MS
Manuscript Region of Origin: USA
Abstract: Alkane-1,1-bistriflates, prepared in excellent yields by
reaction of aldehydes with triflic anhydride, are converted to their
respective 1,1-difluoroalkanes in good to excellent yield through
reaction with fluorinating agent, triethylamine trishydrofluoride.
Straight chain 1,1-bistriflates are more reactive than those substituted
at the 2-position, but the latter are also converted successfully,
without evidence of any rearrangement products.
Page 1 of 21

*Graphical Abstract - Pictogram
Page 2 of 21

Synopsis
1,1-Difluoroalkanes are readily prepared from their respective 1,1-bistriflates by treatment with Et3N-
3HF.
Page 3 of 21

Highlights
1,1-alkane bistriflates are readily prepared from aldehydes
1,1-difluoroalkanes are readily prepared from 1,1-bistriflates
Triethylamine trishydrofluoride is an excellent fluorinating reagent
Page 4 of 21

Preparation of 1,1-Difluoroalkanes from Aldehydes via 1,1-bis-triflates.
Advantageous Use of HF-Lewis Base Reagents
William R. Dolbier, Jr.* and Masamune Okamoto
Department of Chemistry, University of Florida, Gainesville, FL 32611-7200
Abstract. Alkane-1,1-bistriflates, prepared in excellent yields by reaction of aldehydes
with triflic anhydride, are converted to their respective 1,1-difluoroalkanes in good to
excellent yield through reaction with fluorinating agent, triethylamine trishydrofluoride.
Straight chain 1,1-bistriflates are more reactive than those substituted at the 2-position,
but the latter are also converted successfully, without evidence of any rearrangement
products.
1. Introduction
The most commonly used method for conversion of aldehydes to 1,1-
difluoroalkanes involves use of one of many available, sulfur-based deoxofluorination
reagents, such as SF4, DAST (diethylaminosulfur trifluoride) [1], Deoxo-Fluor (bis(2-
methoxyethyl)aminosulfur trifluoride) [2], Xtal-Fluor [3] and Fluolead[4]
Closer to the specific methodology to be described in this paper, is the work of
Garcia Martinez [5] and that of Makosza [6], within whose papers the conversion of 1,1-
bistriflates to 1,1-difluoroalkanes via nucleophilic substitution was reported (Scheme 1).
1
Page 5 of 21

There is always considerable interest in finding the lowest cost solution to a
particular synthetic problem, and anhydrous HF is probably the least expensive
available source of fluorine. This, combined with our own interest in the use of either
anhydrous HF [7] or HF-Lewis base reagents [8] to carry out fluorine/halogen exchange
processes and our current interest in the synthesis of gem-difluoroalkanes [9], led us to
examine the use of various HF-Lewis base combinations for conversion of 1,1-
bistriflates to 1,1-difluoroalkanes.
2. Results and Discussion
During an earlier study of the kinetic effects of fluorine substituents on
nucleophilic substitution [10], we had the occasion to prepare 1-bromo-1-fluorononane
from the 1,1-bistriflate via stepwise nucleophilic substitution using a method developed
by Garcia-Martinez [11]. It was noticed that considerable 1,1-difluoroalkane was formed
along with the desired bromo, fluoro compound, and although, as mentioned above,
earlier work has shown that 1,1-difluorides can be prepared via from the bistriflate by
nucleophilic substitution by fluoride, we thought that the process might be improved by
2
Page 6 of 21

use of HF-Lewis base reagents as the source of fluoride in a presumed solvolytic
process.
2.1. Preparation of 1,1-bistriflates
The requisite 1,1-bistriflates were readily prepared by the reaction of the
respective aldehydes with triflic anhydride in the presence 2,6-lutidine, as shown in
Scheme 2. Yields were as follows: 1a (R = 3-heptyl), 95%; 1b (R = n-octyl), 96%; 1c (R
= n-hexyl), 84%; 1d (R = n-butyl), 80%; 1e (R = benzyl), 54%; 1f (R = isopropyl), 58%;
1g (R = cyclohexyl), 80%; 1h (R = t-butyl), 84%. The 19F NMR spectra of all of these
bistriflates exhibited a characteristic singlet signal between -74.0 and -74.9 ppm in their
19F NMR spectra along with a characteristic triplet (JHH = 5-6 Hz) (1b-e) or doublet (JHH
= 2-5 Hz) (1a, f-h) at 6.3-6.5 ppm in their proton NMR spectra [12]. Proton and fluorine
NMR spectra are provided in the Supplementary Data for all prepared bistriflates.
It was not possible to convert any benzaldehyde derivatives (i.e., R = Ph) to their
respective bistriflates, nor were bistriflates able to be prepared from ketones, vinyl
triflates being the only obtainable products [13].
2.2. Conversion of 1,1-bistriflates to 1,1-difluoroalkanes
3
Page 7 of 21

In preliminary experiments using 2-ethylhexane-1,1-diyl
bis(trifluoromethanesulfonate) (1a) in conjunction with THF-5HF, pyridine-HF, and Et3N-
3HF as sources of fluoride ion, it was found that, without an additive, only Et3N-3HF had
any significant effectiveness in this exchange reaction (Scheme 3, Table 1, entries 1-3).
On the other hand, with addition of proton sponge (entries 4-7), the effectiveness of all
three became enhanced, with that of Et3N-3HF reaching the point of being satisfactory.
Table 1. Preliminary experiments using bistriflate, 1aa
Entry
Reagent (Equiv)
THF-5HF (30)
Pyr-HF (30)
Et3N-3HF (20)
THF-5HF (30)
Pyr-HF (10)
Solvent
Additive
2a (%)b
0
3a (%)b
Trace
1
2
3
4
5
6
7
-
-
-
-
-
-
-
Trace
21.8
17.1
17.5
51.4
85
0
0
PS (4 eq)c
PS (4eq)c
PS (4eq)c
PS (1eq)c
10.4
Trace
0
CH2Cl2 (0.25M)
CH2Cl2 (0.25M)
CH2Cl2 (0.25M)
Et3N-3HF (5)
Et3N-3HF (8)
0
a all reactions run at rt for 24 h; b NMR yields; c PS = proton sponge (1,8-bis-
(dimethylamino)-naphthalene
Because the reaction of bistriflate 1a with any source of HF will generate two
equivalents of very strong acid HOTf, two equivalents of base (i. e., Et3N) will be
consumed during the reaction; hence there is a logical necessity that an excess in
equivalents of Et3N-3HF be used in the reaction in order, at the minimum, to mitigate the
impact of formation of HOTf on destruction of the structural integrity of Et3N-3HF.
In fact proton sponge, 1,8-bis-(dimethylamino)-naphthalene, is known to form a
4
Page 8 of 21

strong 1:1 complex with HF [14], and to effectively steal HF from Et3N-3HF [15]
(Scheme 4). This 1:1 complex is also known to be an effective source of nucleophilic
fluoride ion for halogen-exchange reactions of heterocyclic systems [15,16]. Due to the
Scheme 4. Proton sponge – HF complex formation
steric interaction of its basic centers, proton sponge (PS) is an exceptionally strong
amine base (pKa = 12.1)[17,18]. It therefore would also act as a great scavenger for the
protons of the triflic acid that is formed in the reaction.
2.2.1. Optimization experiments
It was considered that these results were sufficient to allow us to center our
attention upon the use of Et3N-3HF as the most efficient exchange reagent. Further
experiments were carried out using Et3N-3HF to optimize conditions and to test other
amines as additives. Proton sponge was considered much too expensive to be used as
additive in this reaction, unless it was determined to be absolutely necessary.
In the end, one equivalent of proton sponge proved adequate and two sufficient
to obtain good yields (Entries 1-6, Table 2), but it was also found the DMAP (4-
5
Page 9 of 21

(dimethylamino)pyridine) and TMEDA (1,2-(dimethylamino)ethane) were adequate, but
not entirely equivalent replacements for proton sponge. The more reactive, straight-
chain bistriflate, nonane-1,1-diyl bis(trifluoromethanesulfonate), (1b) was used for these
optimization reactions (Scheme 5, Table 2)
Table 2. Optimization experiments
Entry Et3N-3HF
(equiv)
Additive
(equiv)
Time (h) Temp
(oC)
2b (%)a
3b (%)a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
5
4
1
1
1
8
1
2
8
4
4
8
4
4
4
none
none
none
PS (1)
PS (1)
PS (1)
PS (2)
PS (2)
17
2.5
17
2.5
17
rt
40
0
66
81
5
5
70
58
0
18
69
85
62
80
92
81
77
87
70
44
86
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
17
2.5
2.5
2.5
17
2.5
17
2.5
2,5
17
PS (2)
DMAP (0.2)
DMAP (2)
DMAP (2)
TMEDA (2)
TMEDA (0.2)
TMEDA (0.2)
47
a NMR yields
6
Page 10 of 21

2.2.2. Results using optimized method
Considering all information gleaned from the preliminary and optimization
experiments, a variety of 1,1-bistriflates were examined under conditions that were
chosen in order to provide optimal results for each individual substrate, with the results
being given in Table 3 (Scheme 6). The n-alkyl 1,1-difluoroalkane products (R =
19
primary) exhibited characteristic triplet of doublet signals at about -116 ppm in their F
NMR spectra (JHF = 17.5 Hz and 57 Hz), and triplet of triplet signals at 5.8-5.9 ppm in
1
their H NMR spectra (JFH = 57 Hz, and JHH = 4.5 Hz), whereas the 2-substituted
products (R = secondary) exhibited characteristic doublet of doublet signals at -123 to -
124 ppm (JHF = 57 Hz and 16 Hz) in their 19F NMR spectra and triplet of doublet signals
at about 5.7 ppm (JHF = 57 Hz and JHH = 1-2 Hz) in their 1H NMR spectra.
The less sterically-hindered, n-alkyl 1,1-bistriflates (R = primary) were more
reactive than the branched substrates (R = secondary). Arguably, the best results
Table 3. Results under optimized conditons
, 19F NMR
, 19F NMR
Substr
R
Temp Time
Additive
(equiv)
2
3
(oC)
(hr)
(%)b
(%)
[Ref]
b
1b
1b
1b
1c
1c
n-octyl
n-octyl
n-octyl
n- hexyl
n- hexyl
rt
rt
40
40
rt
17
2.5
2.5
2.5
2.5
TMEDA (0.4) 86
-116.2 [6]
0
0
5
0
0
-129.8, -75.5
PS (2)a
None
92
81
TMEDA (0.4) 72
-116.2 [19]
PS (2)a
87
7
Page 11 of 21

1c
1d
1d
1d
1e
1e
1e
1a
1a
1a
1a
1f
n- hexyl
n-butyl
n-butyl
n-butyl
PhCH2
40
40
rt
40
40
rt
40
rt
40
rt
40
40
rt
40
40
rt
40
rt
60
2.5
2.5
2.5
2.5
5
17
5
40
5
17
17
7
7
7
None
78
0
0
0
0
0
0
0
0
0
13
17
2
0
19
0
TMEDA (0.4) 73
-116.1 [20]
-115.4 [6]
-123.3 [6]
PS (2)a
None
78
66
TMEDA (0.4) 76
-117.94, -75.4
-125.9, -75.4
PhCH2
PhCH2
PS (2)a
None
61
67
3-heptyl
3-heptyl
3-heptyl
3-heptyl
isopropyl
isopropyl
isopropyl
cyclohexyl
cyclohexyl
cyclohexyl
t-butyl
TMEDA (0.4) 79
TMEDA (0.4) 69
PS (2)a
60
TMEDA (0.4) 73
TMEDA (0.4) 57
-124.2 [20]
-123.6 [20]
1f
1f
PS (2)a
66
TMEDA (0.4) 50
TMEDA (0.4) 79
1g
1g
1g
1h
1h
7
-125.6, -75.4
-129.8, -75.3
17
17
17
17
PS (2)a
None
79
54
0
3
4
TMEDA (0.4)
TMEDA (0.4) 35
-128.3 [1,20] 98
22
t-butyl
a 8 equiv of Et3N-3HF used; b NMR yields
were generally obtained, when using 2 equivalents of proton sponge as additive, along
with 8 equivalents of Et3N-3HF. Under these conditions 78-92% yields were obtained
for n-alkyl substrates (1b-1d), with 60-79% yields being obtained for the 2-substituted
substrates (1a, f & g). Alternatively, using only 4 equivalents of Et3N-3HF combined
with 0.4 equivalents of TMEDA gave equally good results (72-86% yields for n-alkyl
substrates (1b-1d) and 73-79% yields being obtained for 2-substituted substrates (1a, f
& g)). Competitive results were also obtained for the straight chain, n-alkyl 1,1-
bistriflate substrates when no additive was added (Yields of 66-81%), but all 2-
substituted substrates required an additive in order to obtain decent conversions.
Conditions for at least partial conversion of the neopentyl substrate, 1h, were
able to be found, but heating at 60 o for 17 hours was required in order to obtain 35%
conversion. When the reaction was carried out at room temperature, only the
monofluoro product was formed (98%). No rearrangement products were able to be
8
Page 12 of 21

detected from either this system or any of the other 2-substituted alkyl systems (1a, f, or
g). This lack of rearrangement products was surprising, considering the expectation
that these reactions, particularly that of the neopentyl substrate, might proceed via a
solvolytic process involving carbocations. Apparently all of the observed reactions are
proceeding via an SN2 mechanism.
2.3. Use of pure proton-sponge – HF complex
It had earlier been noted that the 1:1 complex of proton sponge with HF was itself
a good nucleophilic source of fluoride anion [15,16]. Indeed Darabantu found that
combinations of Et3N-3HF with PS also acted as excellent sources of nucleophilic
fluoride anion for use in nucleophilic aromatic substitution reactions of heterocyclic
halides [15]. However, to our knowledge no one has reported the use of either PS-HF
or combinations of Et3N-3HF as sources of fluoride ion in SN2 reactions, which is the
probable mechanism for the reactions with our bistriflates. It was therefore decided to
examine the use of pure PS-HF in our bistriflate reaction, with the result (Scheme 7)
that use of PS-HF alone proved to give results similar, but slightly inferior to those of the
Et3N-3HF/PS mixtures in reactions with n-nonyl bistriflate (1b).
Scheme 7. Use of proton sponge – HF in conversion of bistriflates
9
Page 13 of 21

2.4. Possible alternative use of 1,1-bis(trifluoroacetates)
A recent report of a ketone acylal, cyclohexane-1,1-diyl bis(trifluoroacetate) being
successfully converted to 1,1-difluorocyclohexane using pyridine-HF with catalysis by
trifluoroacetic acid [21], led us to also examine and compare the reactivity of an
analogous aldehyde acylal, 2-ethylhexane-1,1-diyl bis(trifluoroacetate), (4) under
various conditions of exchange (Scheme 8).
Bistrifluoroacetate 4 proved to be completely unreactive with any of the HF-Lewis
base reagents, with no fluorine incorporation being obtained after stirring overnight at
room temperature. Neither addition of catalytic CF3CO2H to pyridine-HF, nor addition of
proton sponge to Et3N-3HF led to observable exchange.
3. Conclusions
Triethylamine trishydrofluoride proved to be an excellent reagent for the purpose
of converting alkane 1,1-bistriflates to the respective 1,1-difluoroalkanes in a process
that occurs without observable rearrangement. Thus, this two-step procedure for
conversion of aldehydes to 1,1-difluoroalkanes should be considered a good alternative
to the use of deoxofluorinating reagents for this purpose.
10
Page 14 of 21

4. Experimental
4.1. General information
All NMR spectra were run using CDCl3 as solvent, unless otherwise specified. 1H
NMR spectra were recorded at 300 MHz, with chemical shifts being reported in ppm
downfield relative to TMS. 19F NMR spectra were recorded at 282 MHz, with chemical
shifts being reported in ppm downfield relative to CFCl3. 13C NMR spectra were
recorded at 75 MHz with proton decoupling, and chemical shifts are reported in ppm
downfield relative to TMS. as the reference. All reagents were purchased at commercial
quality and were used without further purification.
4.2. Typical procedure for preparation of 1,1-bistriflates. Nonane-1,1-diyl
bis(trifluoromethanesulfonate (1b)
A solution of trifluoromethanesulfonic anhydride (4.2 g, 15 mmol) in dichloromethane (5
mL) was slowly added to a stirred solution of nonanal (1.0 g, 7 mmol) and 2.6-lutidine
(1.1 g, 10 mmol) in dichloromethane (30 mL) at 0 oC. After stirring for 5 h, the reaction
mixture was sealed and left in a freezer for 48-72 h at -10 oC, after which time the
reaction was complete, as determined by 19F-NMR. The solvent was then removed by
rotary evaporation at room temperature and the residue extracted with pentane (2×40
mL). The pentane extract was washed with aqueous 1.0 M hydrochloric acid (50 mL),
11
Page 15 of 21

saturated sodium bicarbonate solution (50 mL), and brine (50 mL), after which the
organic phase was dried with magnesium sulfate and the solvent removed by rotary
evaporation at room temperature to obtain a product that required no additional
purification before being used in the next step: nonane-1,1-diyl
bis(trifluoromethanesulfonate (2.8 g, 6.6 mmol, 94%); 1H NMR,  0.87 (t, J = 6.8 Hz,
3H), 1.28-1.50 (m, 12H), 2.08-2.15 (m, 2H), 6.48 (t, J = 5.1 Hz, 1H); 19F NMR,  -74.9
(s, 6F).
Proton and fluorine NMR spectra of all bistriflates are included in the
Supplementary Data for this paper.
4.2.1. Heptane-1,1-diyl bis(trifluoromethanesulfonate (1c)
1H NMR,  0.88 (t, J = 6.8 Hz, 3H), 1.28-1.51 (m, 8H), 2.08-2.16 (m, 2H), 6.48 (t,
J = 5.2 Hz, 1H); 19F NMR,  -74.9 (s, 6F).
4.2.2. Pentane-1,1-diyl bis(trifluoromethanesulfonate (1d)
1H NMR,  0.96 (t, J = 7.1 Hz, 3H), 1.41-1.48 (m, 4H); 2.09-2.16 (m, 2H), 6.48 (t,
J = 5.4 Hz, 1H); 19F NMR,  -74.9 (s, 6F).
4.2.3. 2-Phenylethane-1,1-diyl bis(trifluoromethanesulfonate (1e)
1H NMR,  3.40 (d, J = 5.1 Hz, 2H), 6.54 (t, J = 5.5 Hz, 1H), 7.23-7.40 (m, 5H);
19F NMR,  -74.8 (s, 6F) [22] .
12
Page 16 of 21

4.2.4. 2-Ethylhexane-1,1-diyl bis(trifluoromethanesulfonate (1a)
1H NMR,  0.90-1.05 (m, 6H), 1.34-1.61 (m, 8 H), 1.86-1.91 (m, 1H), 6.52 (d, J =
5.4 Hz, 1H); 19F NMR,  -74.8 (s, 6F).
4.2.5. Cyclohexylmethane-1,1-diyl bis(trifluoromethanesulfonate (1f)
1H NMR,  1.18-1.36 (m, 5H), 1.73-2.05 (m, 6H), 6.31 (d, J = 2.4 Hz, 1H); 19F
NMR,  -74.7 (s, 6F).
4.2.6. 2-methylpropane-1,1-diyl bis(trifluoromethanesulfonate (1g)
1H NMR,  1.14 (d, J = 7.2, 6H), 2.31-2.36 (m, 1H), 6.56 (d, J = 3.3, 1H); 19F
NMR,  -74.7 (s, 6F) [12].
4.2.7. 2,2-Dimethylpropane-1,1-diyl bis(trifluoromethanesulfonate (1h)
1H NMR,  1.13 (s, 9H), 6.63 (s, 1H); 19F NMR,  -74.0 (s, 6F) [22].
4.3. Typical preparation of 1,1-difluoroalkanes: 1,1-difluorononane (2b)
13
Page 17 of 21

Triethylamine-tris-hydrofluoride, Et3N-3HF, (7.2 g, 45 mmol) was added to a
stirred suspension of proton-sponge (1.50 g, 7 mmol) in dichloromethane (15 mL) at 0
oC. After stirring this mixture for 10 min. at 0 ℃, a solution of nonane-1,1-diyl
bis(trifluoromethanesulfonate (1b) (2.4 g, 5.7 mmol) in dichloromethane (5 mL) was
slowly added and the mixture stirred for an additional 5.5 h. At that time, 30 mL of
pentane was added to the reaction mixture, which was then filtered to remove all solids.
To the filtrate was added 30 mL of half-saturated sodium bicarbonate and the mixture
was stirred for 20 min at room temperature. The organic layer was then separated,
washed with half-saturated sodium hydrogen carbonate, 1.0 M hydrochloric acid (30
mL) and brine (50 mL). The organic phase was dried with magnesium sulfate, and the
solvent was removed by a rotary evaporation at room temperature to obtain crude
product (1.35 g). The 1,1-difluorononane was purified by column chromatography (silica
gel, pentane), with the pentane being removed carefully to provide 0.72 g (77%) of
1
colorless liquid product, 2b [6,23]: H NMR,  0.88 (t, J = 6.5 Hz, 3H), 1.28-1.47 (m,
12H), 1.73-1.82 (m, 2H), 5.79 (tt, J = 4.4 and 57 Hz, 1H); 19F NMR,  -116.2 (td, J = 17.5
and 57 Hz, 2F); 13C NMR,  11.2, 13.9, 20.5-20.6 (m, 2C), 22.9, 26.9 (t, J = 4.6 Hz),
29.0, 43.5 (t, J = 18 Hz), 119.2 (t, J = 237 Hz).
Products 2a and 2b were satisfactorily isolated in this manner, whereas other
products were not isolated, and their yields were obtained solely by 19F NMR. All of the
1,1-difluoro alkane products have been previously prepared, and references to papers
containing their earlier-obtained spectral data are provided.
14
Page 18 of 21

4.3.1. 1,1-difluoroheptane (2c)[19]
19F NMR,  -116.2 (td, J = 17.5 and 57 Hz, 2F).
4.3.2. 1,1-difluoropentane (2d)[20]
19F NMR,  -116.1 (td, J = 17.5 and 57 Hz).
4.3.3. 1,1-difluoro-2-phenylethane (2e)[6]
1H NMR,  3.41 (dt, J = 4.5 and 18 Hz, 2H), 5.92 (tt, J = 4.5 and 57 Hz), 1H), 19F
NMR,  -115.3 (td, J = 17.5 and 57 Hz, 2F); 13C NMR,  40.9 (t, J = 45 Zh), 116.6 (t, J =
241 Hz), 127.4, 128.6, 129.8.
4.3.4. 1,1-difluoro-2-ethylhexane (2a)[6,20]
1H NMR,  0.91-0.95 (m, 6H), 1.32-1.55 (m, 9H), 5.71 (dt, J = 1.4 and 57 Hz,
1H); 19F NMR,  -123.45 (dd, J = 16 and 57 Hz); 13C NMR,  14.1, 22.2 (t, J = 5.7 Hz),
22.7, 29.1 (m), 29.4, 31.8, 34.1 (t, J = 21 Hz), 117.5 (t, J = 238 Hz).
4.3.5. (difluoromethyl)cyclohexane (2f)[6,20]
1F NMR,  –123.6 (dd, J = 16 and 57 Hz, 2F).
4.3.6. 1,1-difluoro-2-methylpropane (2g)[20]
19F NMR,  -124.1 (dd, J = 16 and 57 Hz, 2F).
15
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4.3.7. 1,1-difluoro-2,2-dimethylpropane (2h)[1,20]
19F NMR,  -128.3 (d, J = 57 Hz, 2F).
4.3.8. 1-fluorononanyl trifluoromethanesulfonate (3b)
Under conditions where the partially fluorinated product, 1-fluorononanyl
trifluoromethanesulfonate (3b) was formed as the major product (Table 2, Entry 3), it
was isolated by first washing the reaction mixture sequentially by satd. NaHCO3, 1N-
HCl, and satd. NaHCO3, which after careful evaporation of the dichloromethane solvent
1
was further purified by silica gel chromatography (pentane): H NMR,  0.89 (t, J = 7.2
Hz, 3H), 1.54 (m, 12H), 1.92-2.02 (m, 2H), 6.13 (td, J = 5.2 and 55 Hz, 1H); 19F NMR, 
-75.4 (d, J = 7.3 Hz, 3F), -119.2 (m, 1F).
Acknowledgment
Support of this research by Central Glass Co., Ltd is gratefully acknowledged.
Appendix A. Supplementary data
Supplementary data associated with this paper, including copies of proton and
fluorine NMR spectra of all new compounds, can be found in the online version.
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