An efficient dehyrohalogenation method for the synthesis of α,β,β-trifluorostyrenes, α-chloro-β,β- difluorostyrenes and E-1-arylperfluoroalkenes

Article abstract of DOI:10.1016/j.jfluchem.2005.05.005

Dehydrofluorination of 1-aryl-1,2,2,2-tetrafluoroethanes (ArCHFCF ₃) and 1-aryl-1-chloro-2,2,2-trifluoroethane (ArCHClCF₃) using lithiumhexamethyldisilazide (LHMDS) in tetrahydrofuran (THF) at room temperature produced 1,2,2-trifluorostyrene and 1-chloro-2,2-difluorostyrene, respectively, in very good isolated yields. Dehydrofluorination of 1,2,2,3,3,3-hexafluoro-1-phenyl-propane (PhCHFCF₂CF₃) and 1,2,2,3,3,4,4,4-octafluoro-1-phenyl-butane (PhCHFCF₂CF ₂CF₃) using LHMDS produced the corresponding substituted olefins (1-phenyl-1,2,3,3,3-pentafluoroprop-1-ene and 1-phenyl-1,2,3,3,4,4,4- pentafluorobut-1-ene) in good yield and high E-selectivity. Dehydrofluorination of 1-chloro-1-phenyl-2,2,3,3,3-pentafluoropropane (PhCHClCF₂CF ₃) and 1-chloro-1-phenyl-2,2,3,3,4,4,4-heptafluorobutane (PhCHClCF₂CF₂CF₃) produced a mixture of the corresponding E and Z olefins (PhCClCFCF₃ and PhCClCFCF ₂CF₃) in good yield.

Full text of DOI:10.1016/j.jfluchem.2005.05.005

Journal of Fluorine Chemistry 126 (2005) 1174–1184
www.elsevier.com/locate/fluor
An efficient dehyrohalogenation method for the synthesis of
a,b,b-trifluorostyrenes, a-chloro-b,b-difluorostyrenes and
E-1-arylperfluoroalkenes
*
R. Anilkumar, Donald J. Burton
Department of Chemistry, The University of Iowa, Iowa City, IA 52242, USA
Received 19 March 2005; received in revised form 16 May 2005; accepted 18 May 2005
Available online 27 June 2005
Abstract
Dehydrofluorination of 1-aryl-1,2,2,2-tetrafluoroethanes (ArCHFCF3) and 1-aryl-1-chloro-2,2,2-trifluoroethane (ArCHClCF3) using
lithiumhexamethyldisilazide (LHMDS) in tetrahydrofuran (THF) at room temperature produced 1,2,2-trifluorostyrene and 1-chloro-2,2-
difluorostyrene, respectively, in very good isolated yields. Dehydrofluorination of 1,2,2,3,3,3-hexafluoro-1-phenyl-propane (PhCHFCF2CF3)
and 1,2,2,3,3,4,4,4-octafluoro-1-phenyl-butane (PhCHFCF2CF2CF3) using LHMDS produced the corresponding substituted olefins (1-
phenyl-1,2,3,3,3-pentafluoroprop-1-ene and 1-phenyl-1,2,3,3,4,4,4-pentafluorobut-1-ene) in good yield and high E-selectivity. Dehydro-
fluorination of 1-chloro-1-phenyl-2,2,3,3,3-pentafluoropropane (PhCHClCF2CF3) and 1-chloro-1-phenyl-2,2,3,3,4,4,4-heptafluorobutane
(PhCHClCF2CF2CF3) produced a mixture of the corresponding E and Z olefins (PhCCl CFCF3 and PhCCl CFCF2CF3) in good yield.
# 2005 Elsevier B.V. All rights reserved.
Keywords: 1,2,2-Trifluorostyrene; 1-Chloro-2,2-difluorostyrene; 1-Arylperfluoroalkene; 1-Aryl-1,2,2,2-tetrafluoroethane; 1-Chloro-1-aryl-2,2,2-trifluor-
oethane; Dehydrofluorination; Dehydrohalogenation; Trifluoromethylketone; LHMDS; DAST
1. Introduction
temperature preparation of 1,2,2-trifluorostyrene by the
metallation of the readily available HFC-134a (Scheme 1)
[20,21]. This methodology was successfully extended to the
synthesis of various 1-halo-2,2-difluorostyrenes from
CF3CH2X (X = Cl, Br, I) type precursors [22–24].
Fluorine containing olefins are versatile synthetic
building blocks in organic synthesis [1–3]. They have also
been used as potential enzyme inhibitors [4–6] and proved to
have cytotoxic activity [7,8]. Some of them have been shown
to exhibit potent nematocidal and insecticidal activities [9–
12]. Hence, the synthesis of fluorinated olefins, especially in
a stereoselective fashion, was interesting from both the
chemical and biological point of view.
Simultaneously, with the metallation method, we have
explored other possible routes for a highly efficient synthesis
of 1,2,2-trifluorostyrenes and 1-halo-2,2-difluorostyrenes.
One such method was a dehydrohalogenation process, where
dehydrofluorination or dehydrochlorination of the corre-
sponding fluorinated precursors by a selective base could lead
to TFS or related olefins. In a previous communication, we
demonstrated that bases like lithiumhexamethyldisilazide
(LHMDS) or DBU were excellent for effecting this
transformation without undergoing the normally observed
side reactions, the addition or addition–elimination with the
product olefin [25]. Herein, we describe the full account of
this dehyrohalogenation strategy for the synthesis of various
substituted 1,2,2-trifluorostyrenes, 1-chloro-2,2-difluorostyr-
enes and (E)-1-arylperfluoroalkenes.
Among the fluorinated olefins, 1,2,2-trifluorostyrene
(TFS) has received increased attention as its polymers
and co-polymers found application as ionomer membranes
in fuel cell separators [13–19]. The challenge in the
application of TFS has been its synthesis as the preparation
of this monomer in good yield and purity has been a difficult
task. Recently, we have developed a remarkable room
* Corresponding author. Fax: +1 319 335 1270.
E-mail address: donald-burton@uiowa.edu (D.J. Burton).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.05.005

R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
1175
Scheme 1. Synthesis of 1,2,2-trifluorostyrenes and 1-halo-2,2-difluorostyrenes by metallation/coupling method.
2. Results and discussion
oethanes was then carried out using lithiumhexametyldisi-
lazide in tetrahydrofuran (THF) at 15 8C to produce 1,2,2-
trifluorostyrenes in very good isolated yield. The results of
the dehyrofluorination of various 1-aryl-1,2,2,2-tetra-
fluoethanes are summarized in Table 1.
2.1. Synthesis of 1,2,2-trifluorostyrenes
The precursor for the dehydrofluorination, 1-phenyl-
1,2,2,2-tetrafluoroethane was synthesized from the commer-
cially available trifluoromethylphenylethanol with diethy-
laminosulfur trifluoride (DAST) [26]. Dehydrofluorination
of 1-phenyl-1,2,2,2-tetrafluoroethane was attempted using
various bases, and lithiumhexamethyldisilazide was found
to be the best, 91% yield (19F NMR) of 1,2,2-trifluorostyrene
[25]. After standardizing the reaction conditions for the
dehydrofluorination using the disilazide base, we have
performed reactions for the synthesis of a series of
substituted 1,2,2-trifluorostyrenes. The precursors, 1-aryl-
1,2,2,2-tetrafluoroethanes (ArCHFCF3) were obtained from
the corresponding trifluoromethylacetophenones (synthe-
sized by the reaction of the corresponding Grignard reagent
with either trifluoroacetic acid or its ethyl ester) [27,28]. The
trifluoromethylacetophenones were reduced to the corre-
sponding alcohol with NaBH4, followed by fluorination with
DAST or DeoxofluorTM at low temperature to obtain the
desired tetrafluorinated arylethanes in good yield [29]. The
direct synthesis of these alcohols can also be achieved by the
reaction of trifluoromethyltrimethylsilane and the corre-
sponding aldehyde in presence of a fluoride ion source [30].
Dehydrofluorination of the aryl substituted tetrafluor-
Similar to the TFS synthesis discussed above, we also
attempted the dehydrochlorination of the corresponding
chlorinated precursors, as it can be achieved with a relatively
milder base due to the better leaving group ability of ClÀ.
Thus, 2-chloro-1-phenyl-1,2,2-trifluoroethane (PhCHFCF2-
Cl) was synthesized by a similar sequence of reactions used
for the synthesis of tetrafluorophenylethanes using chlorodi-
fluoroacetic acid instead of trifluoroacetic acid. The
dehydrochlorination of 2-chloro-1-phenyl-1,2,2-trifluoroeth-
anewas initially carried out in THF using LHMDS to produce
the TFS in 94% (19F NMR) yield. The dehydrochlorination of
2-chloro-1-phenyl-1,2,2-trifluoroethane was also attempted
inCH2Cl2 usingDBUatroomtemperaturefor24 htoproduce
TFS in 86% (19F NMR) yield.
2.2. Synthesis of 1-chloro-2,2-difluorostyrenes
After the successful synthesis of various 1,2,2-trifluor-
ostyrenes, we have applied the dehydrofluorination method
for the synthesis of 1-chloro-2,2-difluorostyrenes from the
corresponding chlorinated precursors. Dehydrohalogenation
has been previously used for the synthesis of 1-chloro-2,2-
Table 1
Dehydrofluorination of 1-aryltetrafluoroethanes to corresponding 1,2,2-trifluorostyrenes
Entry
Ar
Isolated yield
Reaction Time for
NMR yield of
Isolated yield of
styrene (ArCF CF2)a (%)
of ArCHFCF3 (%)
dehydro-fluorination (h)
styrene (ArCF CF2)
1b
2c
3
4d
5c,e
6f
7
C6H5–
72
84
83
69
76
63
78
72
69
3
91
84
93
90
79
90
88
95
89
74
72
81
82
69
61
83
91
69
p-ClC6H4–
p-MeC6H4–
p-MeOC6H4–
m-BrC6H4–
m-F3CC6H4–
m-O2NC6H4–
1-Naphthyl–
2-Thienyl–
1.5
8
8
0.5
1
1
8
9f
1
1
a
All products gave satisfactory 19F, 1H, 13C NMR, GC–MS and HRMS consistent with assigned structure and are in agreement with samples prepared in our
laboratory by other methods [20,21,31].
b
The distilled styrene was contaminated with 1–2% hexamethyldisilazane.
c
1.1 eq. LHMDS used.
d
Purified by column chromatography (styrene partially dimerized during distillation).
e
Some cyclodimerization of the styrene observed when the reaction mixture stirred for longer time.
f
Low isolated yield is due to the high volatility of the product.

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R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
Table 2
Dehydrofluorination of 1-aryl-1-chloro-2,2,2-trifluoroethanes to corresponding 1-chloro-2,2-difluorostyrenes
Entry
Ar
Isolated
yield of
ArCHClCF3
(%)
Reaction
NMR yield
of styrene
Isolated yield
of styrene
(ArCCl CF2)a
(%)
time (h) for
dehydro-fluorination
(ArCCl CF2)
1
2
3
4
5
6
7
C6H5–
84
84
88
80
89
79
85
90
3
3
4
3
3
3
3
5
89
90
98
91
92
84
96
95
74
79
81
73
78
68
92
87
p-ClC6H4–
p-MeC6H4–
p-MeOC6H4–
m-BrC6H4–
m-F3CC6H4–
1-Naphthyl–
2-Thienyl–
8
a
All styrenes gave satisfactory 19F, 1H, 13C NMR, GC–MS and HRMS consistent with assigned structure and are in agreement with samples prepared in our
laboratory by other methods [22,25].
difluorostyrenes in moderate yields, essentially by a two step
process; addition of halogen to RCH CF2 [32,33] followed
by dehydrohalogenation using a selective base [34]. The
precursor for the dehydrofluorination, 1-chloro-1-phenyl-
2,2,2-trifluoroethane was synthesized by the reaction of the
corresponding alcohol with thionyl chloride in the presence
of pyridine [35]. The dehydrofluorination of 1-chloro-1-
phenyl-2,2,2-trifluoroethane with LHMDS was performed
in THF at 15 8C to produce 1-chloro-2,2-difluorostyrene in
72% isolated yield. A series of 1-aryl-1-chloro-2,2,2-
trifluoroethanes was subsequently synthesized and dehydro-
fluorinations were performed under similar reaction condi-
tions to produce substituted 1-chloro-2,2-difluorostyrenes in
very good isolated yields. The results of the dehyrofluorina-
tion of various 1-aryl-1-chloro-2,2,2-trifluoroethanes are
summarized in Table 2.
PhCHClCF3. This type of side reaction was absent in the
dehydrochlorination of PhCHFCF2Cl during the synthesis of
1,2,2-trifluorostyrene, where the intermediate carbanion
generation at the a-carbon is less facile due to destabiliza-
tion of the anion by the a-fluorine.
2.3. Synthesis of (E)-1-arylperfluoroalkenes
We then attempted the dehyrofluorination reaction for the
stereoselective synthesis of the fluorinated olefins; such
olefins synthesized in a stereoselective fashion have been
biologically more potent than their isomeric mixture [36].
Hiyama et al. have synthesized (E)-1-aryl-1,2,3,3,3-penta-
fluoropropenes by the dehydrohalogenation of the corre-
sponding fluorinated precursor [37]. The dehydrochlorination
was achieved using DBU, whereas dehydrofluorination
required strong bases like NaNH2/t-BuOH or t-BuOK. In
this reaction, E-isomer was formed as the major product,
which was explained by the least steric interactions in the
corresponding conformation leading to the E-olefin during
this elimination. In the conformation leading to the Z-product,
the CF3 group and the phenyl group repulsively interact,
forcing Z-olefin as the minor product. However, there was
considerable loss of steroselectivity in the dehydrohalogena-
tion reaction using sodium and potassium alkoxides bases
which was explained by a chelate interaction of the alkali
metal and fluorine that eventually forces the formation of
some amount of Z-olefin. The E-steroselectivity was also
observed in the synthesis of fluorovinyl bromides
The dehydrofluorination of PhCHClCF3 was also
attempted using DBU at room temperature in CH2Cl2
solvent, but in vain. Dehydrochlorination of PhCHClCF2Cl
was an easy process under similar conditions, resulting in
complete conversion of the starting material in 3 h with the
formation of 1-chloro-2,2-difluorostyrene (70%) along with
other products constituting mainly PhCHClCF3 (10%)
(Scheme 2). The formation of PhCHClCF3 in this reaction
was rather surprising and could be explained by the attack of
the fluoride ion (released from the substrate by the
nucleophilic attack of the base on the terminal carbon) on
the terminal carbon of the styrene to produce a stabilized
carbanion which further abstracts a proton to produce
Scheme 2. Dehydrohalogenation of PhCHClCF3 and PhCHClCF2Cl using DBU.

R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
1177
Table 3
Synthesis of 1-arylperfluoroalkenes by the dehydrofluorination of corresponding precursors
RF
Isolated yield of
Isolated yield of
NMR yield
of styrene
Isolated yield
of styrene (%)
E/Z ratioa
PhCH(OH)CF2RF (%)
PhCHFCF2RF (%)
PhCF CFRF
CF3
94
95
64
92
93
75
80
99:1
98:2
CF2CF3
a
74
E/Z ratio determined by 19F NMR (3JFF (trans) = 130 Hz, JFF (cis) = 12 Hz).
3
(RCF CFBr and RCH CFBr) where the corresponding
precursors were dehydrobrominated at low temperature [38].
Thus, in accordance with this observation, we have
synthesized 1,2,2,3,3,3-hexafluoro-1-phenyl-propane (PhC-
HFCF2CF3) and 1,2,2,3,3,4,4,4-octafluoro-1-phenyl-butane
(PhCHFCF2CF2CF3) starting from the corresponding ketones
(prepared by the reaction of phenylmagnesium bromide with
pentafluoropropanoic acid or heptafluorobutanoic acid). The
ketones were reduced to the corresponding alcohol using
NaBH4 and the resulting alcohol was treated with DAST to
obtain the desired precursors. Dehyrofluorination was carried
out using LHMDS in THF at 15 8C to produce the
corresponding olefins in excellent isolated yield (Table 3).
The 19F NMR spectrum of the reaction mixture and the
isolated product revealed that there was an excellent
selectivity for the E-isomer. (E) and (Z)-1-phenyl-1,2,3,3,3-
pentafluoropropenewas formed in 99:1 ratio, whereas (E) and
(Z)-1-phenyl-1,2,3,3,4,4,4-pentafluorobutene was formed in
98:2 selectivity (3JFF (trans) = 130 Hz, 3JFF (cis) = 12 Hz). The
excellent E-selectivity in this reaction could be explained by
analyzing the conformations leading to the corresponding
olefins (Fig. 1A and B). Conformation A leading to E-isomer
is free of steric interaction between the bulky phenyl group
and RF (RF = CF3 or CF2CF3) group and is more favorable,
whereas the conformation B leading to Z-isomer is less
favorable due to the steric interaction between the phenyl
group and the RF group.
We have also attempted the stereoselctive synthesis of 1-
chloro-1-phenyl-2,3,3,3-tetrafluoroprop-1-ene by this strat-
egy. Dehydrofluorination of the corresponding precursor, 1-
chloro-1-phenyl-2,2,3,3,3-pentafluoropropane, yielded
a
mixture of E and Z product olefins in 87% yield in 90:10
selectivity (Table 4). We assume that the major isomer is (E)
based on the trend observed in the dehydrofluorination
reaction. Similarly 1-chloro-1-phenyl-2,3,3,4,4,4-hexafluor-
obut-1-ene was synthesized in 84% yield as a mixture of E
and Z isomers (75:25) by dehyrofluorination of correspond-
ing precursor 1-chloro-1-phenyl-2,2,3,3,4,4,4-heptafluoro-
butane.
The loss of steroselectivity in the dehydrofluorination of
chlorinated phenyl propanes and butanes, in comparison with
corresponding fluorinated compounds, was attributed to the
bulkinessofchlorine (Fig. 1), C isthe favored conformation in
this elimination which leads to the major E-olefin. The steric
interaction between RF and Cl group in C forces some extent
the less favored conformation (Fig. 1D), resulting the Z-
isomer as a minor product in this elimination [39].
In conclusion, we have developed a convenient alter-
native room temperature route for the synthesis of 1,2,2-
trifluorostyrenes and 1-chloro-2,2-difluorostyrenes by a
highly efficient dehydrofluorination methodology. The
stereoselective syntheses of trifluoromethyl and pentafluor-
oethylsubstituted difluorostyrenes were achieved with
excellent E-selectivity by this dehyrofluorination method.
The stereoselectivity observed in the case of (E)-trifluor-
omethyl and pentafluoroethylsubstituted difluorostyrenes
was lost in the case of corresponding chloro-substituted
olefin, where both isomeric olefins were formed in
considerable amounts during the dehydrofluorination.
3. Experimental
1H, {1H}13C and 19F NMR spectra were recorded on a
Brucker AC-300 or a WM 360 Spectrometer. Chemical
shifts have been reported in ppm relative to an internal
reference (CDCl3, CFCl3 or TMS). Unless noted otherwise,
CDCl3 was used as the NMR lock solvent. Low resolution
mass spectra were obtained using a Voyeger GC–MS
Fig. 1. E-selectivity in the dehydrofluorination of ArCHFCF2RF and
ArCHClCF2RF.

1178
R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
Table 4
Synthesis of 1-chloro-1-phenyl-2,3,3,3-tetrafluoroprop-1-ene and 1-chloro-1-phenyl-2,3,3,4,4,4-hexafluorobut-1-ene by dehydrofluorination
RF
Isolated yield of
NMR yield
of styrene
Isolated yield
of styrene (%)
Ratio of product
styrenea PhCCl CFRF
PhCHClCF2RF (%)
CF3
81
89
95
97
87
84
89:11
75:25
CF3CF2
a
Ratio of isomers based on 19F NMR.
instrument operated at 70 eV in the electron impact mode,
using a 15 m CB-5 column. The reported fragment peaks
correspond to the most abundant ions, in addition to the
parent ion(s). High resolution mass spectra (HRMS) were
obtained by the University of Iowa High Resolution Mass
Spectrometry Facility. Column chromatography was carried
out using silica gel purchased from Em Science (Silica Gel
60, particle size 63–200 mm). Tetrahydrofuran was dried by
distillation from sodium benzophenone/ketyl at atmospheric
pressure immediately prior to use. N2 was used without
further purification. All other reagents and chemicals were
obtained from commercial sources and used directly. All the
ketones were synthesized by the literature procedure [27].
All boiling points were measured during distillation and are
uncorrected.
J = 282, 29 Hz), 89.2 (dq, J = 185, 34 Hz); GC–MS: 178
(M+) (14), 109 (45), 74 (83), 59 (100), 45 (86).
3.3. Synthesis of p-ClC6H4CHFCF3 (n.c.)
From 1-(4-chlorophenyl)-2,2,2-trifluoroethan-1-ol (16.6 g,
79.0 mmol) and DAST (12.7 g, 79.0 mmol) obtained 1-(4-
chlorophenyl)-1,2,2,2-tetrafluoroethane (14.1 g, 66.5 mmol)
in 84% yield.
b.p.: 42 8C/8 mm Hg.
19F NMR (CDCl3): d À79.3 (dd, J = 12, 5 Hz, 3F),
1
À195.1 (dq, J = 45, 13 Hz, 1F); H NMR (CDCl3): d 7.42
(m, 4H), 5.55 (dq, J = 44, 6 Hz, 1H); 13C NMR (CDCl3): d
136.6 (d, J = 3 Hz), 129.7 (s), 129.2 (s), 128.7 (d, J = 7 Hz),
122.2 (dq, J = 281, 28 Hz), 84.5 (dq, J = 185, 34 Hz).
HRMS: calcd for C8H5F435Cl 212.0016, found 212.0012;
calcd for C8H5F437Cl 213.9986, found 213.9979.
3.1. Typical procedure for the fluorination using
diethylaminosulfur trifluoride, synthesis of
tetrafluorophenylethanes
3.4. Synthesis of p-MeC6H4CHFCF3 (n.c.)
A 250 mL three-necked RB fitted with a nitrogen tee, low
temperature thermometer and septa was charged with
dichloromethane (40.0 mL) followed by 8.9 g (55.4 mmol)
DAST. The solution was cooled to À78 8C and a solution of
the trifluoroarylethanol (55.4 mmol) in dichloromethane
(30 mL) was added keeping the temperature around À70 8C.
The mixture was allowed to warm to room temperature and
stirred for 3–8 h. After the completion of the reaction
determined by 19F NMR analysis of the reaction mixture, the
mixture was quenched carefully with a saturated solution of
Na2CO3. The organic layer separated and washed with water
(3 mL Â 40 mL) followed by brine. Careful evaporation of
the solvent followed by distillation produced the fluorinated
product as colorless liquids (63–84%).
From 1-(4-methylphenyl)-2,2,2-trifluoroethan-1-ol (15.8g,
83.2 mmol) and DAST (13.4 g, 83.2 mmol) obtained 1-(4-
methylphenyl)-1,2,2,2-tetrafluoroethane (13.25 g, 69.0mmol)
in 83% yield.
b.p.: 41 8C/8mm Hg.
19F NMR (CDCl3): d À79.3 (dd, J = 14, 6 Hz, 3F),
À193.7 (dq, J = 45, 14 Hz, 1F); 1H NMR (CDCl3): d 7.33 (d,
J = 8, 2H), 7.21 (d, J = 8 Hz, 2H), 5.51 (dq, J = 44, 6 Hz,
1H), 2.35 (s, 3H); 13C NMR (CDCl3): d 140.9 (s), 129.6 (s),
127.5 (s), 127.4 (d, J = 7 Hz), 122.6 (dq, J = 281, 28 Hz),
89.7 (dq, J = 185, 34 Hz), 21.3 (s); GC–MS: 192 (M+) (66),
173 (11), 123 (100), 103 (19), 77 (25).
3.5. Synthesis of p-MeOC6H4CHFCF3 (n.c.)
3.2. Synthesis of C6H5CHFCF3
From 1-(4-methoxyphenyl)-2,2,2-trifluoroethan-1-ol
(11.25g, 54.6 mmol) and DAST (8.8 g, 54.6 mmol) obtained
From 1-phenyl-2,2,2-trifluoroethan-1-ol (22.0 g, 125.0
mmol) and DAST (20.2 g, 125.0 mmol) obtained 1-phenyl-
1,2,2,2-tetrafluoroethane (15.8 g, 88.7 mmol) in 72% yield.
b.p.: 128–129 8C, reported 133 8C [40].
1-(4-methoxyphenyl)-1,2,2,2-tetrafluoroethane
37.4 mmol) in 69% yield.
(7.78 g,
b.p.: 62 8C/8 mm Hg.
19F NMR (CDCl3): d À79.3 (dd, J = 14, 6 Hz, 3F),
À191.2 (dq, J = 44, 15 Hz, 1F); 1H NMR (CDCl3): d 7.38 (d,
J = 8 Hz, 2H), 6.94 (d, J = 9 Hz, 2H), 5.50 (dq, J = 44, 6 Hz,
1H), 3.80 (s, 3H); 13C NMR (CDCl3): d 161.4 (s), 129.1 (d,
J = 6 Hz), 127.5 (s), 122.8 (dq, J = 280, 31 Hz), 114.3 (s),
19F NMR (CDCl3): d À79.3 (dd, J = 13, 6 Hz, 3F),
1
À195.0 (dq, J = 43, 13 Hz, 1F); H NMR (CDCl3): d 7.45
(bs, 5H), 5.56 (dq, J = 44, 6 Hz, 1H); 13C NMR (CDCl3): d
130.7 (s), 130.4 (s), 129.0 (s), 127.4 (d, J = 5 Hz), 122.5 (dq,

R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
1179
89.0 (dq, J = 184, 33 Hz), 55.4 (s); GC–MS: 208 (M+) (58),
189 (12), 139 (100), 109(12), 96 (22), 43 (27). HRMS: calcd
for C9H8F4O 208.0511, found 208.0514.
1-naphthyl-1,2,2,2-tetrafluoroethane (8.25 g, 36.18 mmol)
in 72% yield.
b.p.: 95–96 8C/12 mm Hg.
19F NMR (CDCl3): d À77.9 (dd, J = 13, 6 Hz, 3F),
1
3.6. Synthesis of m-BrC6H4CHFCF3 (n.c.)
À194.9 (dq, J = 44, 13 Hz, 1F); H NMR (CDCl3): d 7.90
(m, 3H), 7.75 (d, J = 7 Hz, 1H), 7.46–7.57 (m, 3H), 6.39 (dq,
J = 43, 6 Hz, 1H); 13C NMR (CDCl3): d 133.7 (s), 131.2 (s),
130.7 (d, J = 2 Hz), 129.2 (s), 127.3 (s), 126.4 (d, J = 10 Hz),
126.2 (s), 126.0 (d, J = 6 Hz), 125.1 (s), 122.8 (dq, J = 282,
29 Hz), 122.6 (s), 86.5 (dq, J = 186, 35 Hz); HRMS: calcd
for C12H8F4 228.0562, found 228.0563.
From 1-(3-bromophenyl)-2,2,2-trifluoroethan-1-ol (20.7g,
81.4mmol) and DAST (13.1 g, 81.4 mmol) obtained 1-(3-
bromophenyl)-1,2,2,2-tetrafluoroethane (15.6, 60.9 mmol) in
76% yield.
b.p.: 58 8C/8 mm Hg.
19F NMR (CDCl3): d À79.3 (dd, J = 13, 5 Hz, 3F),
À196.0 (dq, J = 44,13 Hz, 1F); 1H NMR (CDCl3): d 7.60 (d,
3.10. Synthesis of 1-(2-thienyl)-1,2,2,2-
tetrafluoroethane (n.c.)
J = 7 Hz, 2H), 7.31 (m, 2H), 5.55 (dq, J = 44, 6 Hz, 1H); 13
C
NMR (CDCl3): d 133.8 (s), 132.5 (d, J = 20 Hz), 130.5 (s),
130.3 (d, J = 7 Hz), 125.9 (d, J = 6 Hz), 123.0 (s), 122.1 (dq,
J = 280, 27 Hz), 88.3 (dq, J = 190, 34 Hz). GC–MS: 258
(M+ + 2) (63), 256 (M+) (58), 189 (BP) (100), 187 (95), 127
(23), 108 (54), 107 (51). HRMS: calcd for C8H5F379Br35Cl
271.9215, found 271.9223, calcd for C8H5F379Br37Cl
273.9186, found 273.9174, calcd for C8H5F381Br35Cl
273.9195, found 273.9174, calcd for C8H5F381Br37Cl
275.9165, found 275.9139.
From 1-(2-thienyl)-2,2,2-trifluoroethan-1-ol (3.73 g,
20.5 mmol) and DAST (3.63 g, 22.5 mmol) obtained 1-(2-
thienyl)-1,2,2,2-tetrafluoroethane (2.6 g, 14.1 mmol) in 69%
yield.
b.p.: 32 8C/14 mm Hg.
19F NMR (CDCl3): d À79.1 (dd, J = 14.2, 7.2 Hz, 3F),
1
À177.7 (dq, J = 43.8, 14.1 Hz, 1F); H NMR (CDCl3): d
7.50 (d, J = 4.9 Hz, 1H), 7.30 (t, distorted, 1H), 7.08 (m,
1H), 5.80 (dq, J = 45, 6 Hz); 13C NMR (CDCl3): d 131.0 (d,
J = 23 Hz), 130.0 (d, J = 6 Hz), 129.1(d, J = 2 Hz), 127.1
(s), 121.8 (dq, J = 282, 31 Hz), 85.1 (dq, J = 187, 37 Hz);
HRMS: calcd for C6H4F4S 183.9970, found 183.9967.
3.7. Synthesis of m-F3CC6H4CHFCF3 (n.c.)
From 1-(3-trifluoromethylphenyl)-2,2,2-trifluoroethan-
1-ol (13.86 g, 56.8 mmol) and DAST (9.1 g, 56.8 mmol)
obtained 1-(3-trifluoromethylphenyl)-1,2,2,2-tetrafluoroeth-
ane (8.8 g, 35.7 mmol) in 63% yield.
3.11. Synthesis of C6H5CHFCF2CF3
b.p.: 29–31 8C/9 mm Hg.
From 2,2,3,3,3-pentafluoro-1-phenyl-propan-1-ol (10.77
g, 47.6 mmol) and DAST (8.05 g, 50.0 mmol) obtained
1,2,2,3,3,3-hexafluoro-1-phenyl-propane (6.92 g, 30.3 mmol)
in 64% yield [37].
19F NMR (CDCl3): d À63.4 (s, 3F), À77.3 (dd, J = 13,
6 Hz, 3F), À196.7 (dq, J = 43, 12 Hz, 1F); 1H NMR
(CDCl3): d 7.54–7.76 (m, 4H), 5.65 (dq, J = 44, 6 Hz, 1H);
13C NMR (CDCl3): d 135.0 (s), 131.5 (q, J = 32 Hz), 130.5
(d, J = 17 Hz), 130.0 (s), 129.5 (s), 127.4 (d, J = 11 Hz),
124.0 (m), 123.7 (dq, J = 279, 30 Hz), 88.4 (dq, J =
189, 35 Hz). HRMS: calcd for C9H5F7 246.0279 found
246.0278.
b.p.: 48 8C/15 mm Hg.
19F NMR (CDCl3): d À82.6 (d, J = 11 Hz, 3F), À123.3
(ddd, J = 284, 12, 4 Hz, 1F), 131.9 (ddd, J = 284, 19, 16 Hz,
1F), À196.1 (dm, J = 47 Hz, 1F); 1H NMR (CDCl3): d 7.44
(s, 5H), 5.70 (ddd, J = 44, 18, 5 Hz, 1H); 13C NMR (CDCl3):
d 130.6 (s), 129.8 (d, J = 20 Hz), 128.8 (s), 127.7 (d,
J = 7 Hz), 119.0 (tq, J = 287, 35 Hz), 111.5 (m), 89 (dq,
J = 186, 25 Hz); HRMS: calcd for C9H6F6 228.0374, found
228.0373.
3.8. Synthesis of m-O2NC6H4CHFCF3 (n.c.)
From 1-(3-nitrophenyl)-2,2,2-trifluoroethan-1-ol (5.34 g,
24.16 mmol) and diethylaminosulfur trifluoride (3.89 g,
24.16 mmol) obtained 1-(3-nitrophenyl)-1,2,2,2-tetrafluor-
oethane (4.2 g, 18.8 mmol) in 78% yield.
3.12. Synthesis of C6H5CHFCF2CF2CF3 (n.c.)
19F NMR (CDCl3): d À79.1 (dd, J = 13, 7 Hz, 3F),
From
2,2,3,3,4,4,4-heptafluoro-1-phenyl-butan-1-ol
1
À196.7 (dq, J = 43, 13 Hz, 1F); H NMR (CDCl3): d 8.36
(8.56g, 31.0mmol) and DAST (5.0 g, 31.0 mmol) obtained
1,2,2,3,3,4,4,4-octafluoro-1-phenyl-butane (6.35g, 22.8mmol)
in 74% yield.
(m, 2H), 7.82 (d, J = 8 Hz, 1H), 7.65–7.72 (m, 2H), 5.74 (dq,
J = 44, 6 Hz, 1H); HRMS: calcd for C8H5F4NO2 223.0556,
found 223.0257.
b.p.: 31 8C/12mm Hg.
19F NMR (CDCl3): d À81.4 (dd, J = 12, 2 Hz, 3F),
À120.4 (dm, J = 291 Hz, 1F), À127.0 (ddd, J = 37, 15, 6 Hz,
2F), À128.9 (dm, J = 291 Hz, 1F), À195.3 (dm, J = 45 Hz,
1F); 1H NMR (CDCl3): d 7.44 (s, 5H), 5.76 (ddd, J = 44, 19,
4 Hz, 1H); 13C NMR (CDCl3): d 130.7 (s), 129.8 (d,
3.9. Synthesis of C10H7CHFCF3 (n.c.)
From 1-naphthyl-2,2,2-trifluoroethan-1-ol
50.0 mmol) and DAST (8.05 g, 50.0 mmol) obtained
(11.3 g,

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J = 21 Hz), 128.8 (s), 128.0 (d, J = 7 Hz), 119.0 (tq, J = 287,
33 Hz), 112.0 (m), 111.1 (m), 89.0 (dq, J = 186, 25 Hz);
HRMS: calcd for C10H6F8 278.0342, found 278.0332.
followed by workup and distillation produced p-chloro-
1,2,2-trifluorostyrene as a colorless liquid in 72% (5.48 g,
28.5 mmol) yield.
b.p.: 40 8C/8 mm Hg.
3.13. Synthesis of C6H5CHFCF2Cl
3.17. Synthesis of p-MeC6H4CF CF2
From 2-chloro-2,2-difluoro-1-phenyl-ethan-1-ol (15.2 g,
79.0 mmol) and DAST (12.7 g, 79.0 mmol) obtained 2-
chloro-1-phenyl-1,2,2-trifluoroethane (10.8 g, 55.6 mmol)
in 71% yield.
Dehydrofluorination of 1-(4-methylphenyl)-1,2,2,2-tetra-
fluoroethane (5 g, 26.04 mmol) with LHMDS (31.6 mmol)
followed by workup and distillation obtained p-methyl-1,2,2-
trifluorostyrene (3.64 g, 21.6 mmol) in 81% yield.
b.p.: 45 8C/8 mm Hg.
b.p.: 38 8C/8 mm Hg; reported 95–97 8C/10 mm Hg [41].
19F NMR (CDCl3): d À66.0 (ddd, J = 170, 19, 8 Hz, 1F),
À67.0 (ddd, J = 169, 16, 6 Hz, 1F), À186.4 (dt, J = 43,
16 Hz, 1F); 1H NMR (CDCl3): 7.42 (m, 5H), 5.59 (dt,
J = 44, 8 Hz, IH); 13C NMR (CDCl3): d 131.0 (d, J = 20 Hz),
130.5 (s), 128.7 (s), 127.7 (d, J = 8 Hz), 126.3 (dt, J = 297,
31 Hz), À92.8 (dt, J = 190, 30 Hz).
3.18. Synthesis of p-MeOC6H4CF CF2
Dehydrofluorination of 1-(4-methoxyphenyl)-1,2,2,2-
tetrafluoroethane (5.2 g, 25.0 mmol) with LHMDS
(30.0 mmol) followed by workup and chromatography over
silica gel, eluting with 2% ethyl acetate/hexane, afforded p-
methoxy-1,2,2-trifluorostyrene as a colorless liquid in 82%
(3.85 g, 20.04 mmol) yield.
3.14. Typical procedure for the dehydrofluorination
using LHMDS, synthesis of 1,2,2-trifluorostyrenes
A 250 mL three-necked RB fitted with a nitrogen tee and
septum and a thermometer was charged with THF (15.0 mL)
and 1-aryl-1,2,2,2-tetrafluoroethane (26.1 mmol) under a N2
atmosphere. The solution was cooled to 15 8C and LHMDS
(generated from hexamethyldisilazane 6.6 mL (31.3 mmol)
and n-BuLi (12.6 mL, 31.3 mmol) in THF (15 mL) at 0 8C
was added slowly through a cannula. The progress of the
reaction was followed by 19F NMR and after complete
conversion, the reaction mixture was quenched with water
(35.0 mL) and pentane (40.0 mL) was added. The aqueous
and organic layers separated (emulsion formation could be
broken with diluted HCl) and the aqueous layer extracted
with pentane (2 Â 25 mL). The combined organic extracts
were washed with diluted HCl (4 Â 40 mL) and then with
water. The pentane extracts were dried over anhydrous
Na2SO4 and evaporated under mild vacuum without the loss
of volatile styrenes. The resulting solution on distillation
through a 10 mm vigreux column under vacuum or by
column chromatography over silica gel produced pure 1,2,2-
trifluorostyrenes. All the 1,2,2-trifluorostyrenes were fully
characterized and the spectral data were in agreement with
the styrenes prepared by alternative methods [20,21,31].
3.19. Synthesis of m-BrC6H4CF CF2
Dehydrofluorination of 1-(3-bromophenyl)-1,2,2,2-tetra-
fluoroethane (7.02 g, 27.4 mmol) with LHMDS (30.1
mmol) followed by workup and distillation produced m-
bromo-1,2,2-trifluorostyrene as a colorless liquid in 69%
(4.45 g, 18.9 mmol) yield.
b.p.: 57 8C/8 mm Hg.
3.20. Synthesis of m-F3CC6H4CF CF2
Dehydrofluorination of 1-(3-trifluoromethylphenyl)-
1,2,2,2-tetrafluoroethane (4.92 g, 20.0 mmol) with LHMDS
(24.0 mmol) followed by workup and distillation of the
crude product yielded styrene contaminated with hexam-
ethyldisilazane. Further purification by column chromato-
graphy over silica gel, eluting with pentane, produced m-
trifloromethyl-1,2,2-trifluorostyrene as a colorless liquid in
61% (2.78 g, 12.3 mmol) yield.
b.p.: 37–39 8C/8 mm Hg.
3.21. Synthesis of m-O2NC6H4CF CF2
3.15. Synthesis of C6H5CF CF2
Dehydrofluorination of 1-(3-nitrophenyl)-1,2,2,2-tetra-
fluoroethane (2.23 g, 10.0 mmol) with LHMDS (11.0 mmol)
followed by workup and chromatography over silica gel,
eluting with 2% ethyl acetate/hexane, produced m-nitro-
1,2,2-trifluorostyrene as low melting solid in 83% (1.68 g,
8.3 mmol) yield.
Dehydrofluorination of 1-phenyl-1,2,2,2-tetrafluor-
oethane (2.67 g, 15.0 mmol) with LHMDS (16.5 mmol),
followed by workup and column chromatography over silica
gel, eluting with pentane produced 1,2,2-trifluorostyrene as
a colorless liquid in 74% (1.75 g, 11.1 mmol) yield.
3.16. Synthesis of p-ClC6H4CF CF2
3.22. Synthesis of C10H7CF CF2
Dehydrofluorination of 1-(4-chlorophenyl)-1,2,2,2-tetra-
fluoroethane (8.4 g, 39.6 mmol) with LHMDS (43.5 mmol)
Dehydrofluorination of 1-naphthyl-1,2,2,2-tetrafluor-
oethane (4.20 g, 18.4 mmol) with LHMDS (22.1 mmol)

R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
1181
followed by workup and column chromatography over silica
3.26. Typical procedure for the preparation of 1-chloro-
1-phenyl-2,2,2-trifluoroethanes
gel, eluting with hexanes obtained 1-naphthyl-1,2,2-tri-
fluoroethene as a colorless liquid in 91% (3.47 g,
16.7 mmol) yield.
To a mixture of fluorinated alcohol (85.2 mmol) and
pyridine (93.7 mmol) was slowly added thionyl chloride
(93.7 mmol) and catalytic amount of DMF (ꢀ0.1 mol%).
The mixture was refluxed for 3–5 h and poured into cold
water (20 mL). The organic layer was separated and the
aqueous layer extracted with dichloromethane (3 Â 25 mL).
The combined organics extracts were washed with diluted
HCl (4 Â 40 mL), water (2 Â 40 mL), saturated sodium
bicarbonate (2 Â 40 mL) and brine. Evaporation of the
solvent yielded the crude product which was purified by
distillation [35].
19F NMR (CDCl3): d À102.0 (dd, J = 73, 33 Hz, 1F),
À117.6 (dd, J = 120, 76 Hz, 1F), À160.0 (dd, J = 118,
1
29 Hz, 1F); H NMR (CDCl3): d 7.75–8.1 (m, 3H), 7.35–
7.55 (m, 4H); 13C NMR (CDCl3): d 154.3 (ddd, J = 291, 276,
52 Hz), 133.7 (s), 131.3 (d, J = 5 Hz), 128.9 (q, J = 3 Hz),
128.5 (s), 127.7 (ddd, J = 255, 45, 21 Hz), 127.3 (s),
126.5 (s), 125.0 (s), 124.8 (d, J = 3 Hz), 123.7 (dd, J = 20,
5 Hz).
3.23. Synthesis of 1-(2-thienyl)-1,2,2-trifluoroethene
Dehydrofluorination of 1-(2-thienyl)-1,2,2,2-tetrafluor-
oethane (0.7 g, 3.80 mmol) with LHMDS (4.2 mmol),
followed by column chromatography over silica gel, eluting
with pentane, yielded 1-(2-thienyl)-1,2,2-trifluoroethene as
a colorless liquid in 69% (0.43 g, 2.62 mmol) yield.
3.27. Synthesis of C6H5CHClCF3
Following the general procedure, from 1-phenyl-2,2,2-
trifluoroethan-1-ol (15 g, 85.2 mmol), obtained 1-chloro-1-
phenyl-2,2,2-trifluoroethane as a colorless liquid in 84%
(13.8 g, 71.3 mmol) yield.
3.24. Synthesis of (E)-1-phenyl-1,2,3,3,3-
pentafluoroprop-1-ene
b.p.: 42 8C/8 mm Hg; reported 70–71 8C/27 mm Hg [35].
1
19F NMR (CDCl3): d À73.7 (d, J = 7 Hz, 3F); H NMR
(CDCl3): d 7.36–7.50 (m, 5H), 5.10 (q, J = 6 Hz, 1H); 13C NMR
(CDCl3): d 132.3 (s), 130.2 (s), 128.9 (s), 128.8 (s), 123.6 (q,
J = 280 Hz), 59.4 (q, J = 34 Hz); GC–MS: 196 (M+ + 2) (40),
194 (M+) (68), 159 (77), 125 (100), 109 (78), 89 (56).
Dehydrofluorination of 1,2,2,3,3,3-hexafluoro-1-phenyl-
propane (3.5 g, 15.35 mmol) with LHMDS (16.9 mmol),
followed by column chromatography over silica gel, eluting
with pentane, produced (E)-1-phenyl-1,2,3,3,3-pentafluor-
oprop-1-ene as a colorless liquid in 75% (2.40 g, 11.5 mmol)
yield [31,42].
3.28. Synthesis of p-ClC6H4CHClCF3
19F NMR (CDCl3): d À67.4 (dd, J = 22, 10 Hz, 3F),
Following the general procedure, from 1-(4-chlorophe-
nyl)-2,2,2-trifluoroethan-1-ol (9.0 g, 42.8 mmol), obtained
1-chloro-1-(4-chlorophenyl)-2,2,2-trifluoroethane as a col-
orless liquid in 84% (8.2 g, 35.9 mmol) yield.
b.p.: 60–61 8C/12 mm Hg; reported 95–95.5 8C/
24 mm Hg [35].
À146. 7 (dq, J = 130, 20 Hz), À169.9 (dq, J = 130, 9 Hz,
1
1F); H NMR (CDCl3): d 7.68 (m, 2H), 7.47 (m, 3H); 13C
NMR (CDCl3): d 151.5 (dd, J = 251, 37 Hz), 138.2 (ddq,
J = 249, 50, 29 Hz), 131.3 (d, J = 2.2 Hz), 128.9 (s), 127 (dd,
J = 22.6, 5.4 Hz), 126.6 (t, J = 8 Hz), 119.5 (ddq, J = 276,
36, 4 Hz); HRMS: calcd for C9H5F5 208.0311, found
208.0313.
1
19F NMR (CDCl3): d À73.7 (d, J = 6 Hz, 3F); H NMR
(CDCl3): d 7.35–7.44 (m, 4H), 5.07 (q, J = 7 Hz, 1H); 13C
NMR (CDCl3): d 136.4 (s), 130.7 (s), 130.1 (s), 129.2 (s),
123.3 (q, J = 279.4 Hz), 58.1 (q, J = 34 Hz); GC–MS: 232
(M+ + 4) (9), 230 (M+ + 2) (53), 228 (M+) (78), 195 (54),
193 (54), 193 (97), 163 (18), 161 (84), 159 (100, BP), 143
(83), 85 (74), 83 (88).
3.25. Synthesis of (E)-1-phenyl-1,2,3,3,4,4,4-
heptafluorobutene
Dehydrofluorination of 1,2,2,3,3,4,4,4-octafluoro-1-phe-
nyl-butane (3.82 g, 13.7 mmol) with LHMDS (15.1 mmol),
followed by column chromatography over silica gel, eluting
with pentane, produced (E)-1-phenyl-1,2,3,3,4,4,4-hepta-
fluorobut-1-ene as a colorless liquid in (2.80 g, 11.0 mmol)
80% yield [43].
3.29. Synthesis of p-MeC6H4CHClCF3
Following the general procedure, from 1-(4-methylphe-
nyl)-2,2,2-trifluoroethan-1-ol (5.9 g, 31.4 mmol), obtained
1-chloro-1-(4-methylphenyl)-2,2,2-trifluoroethane as a col-
orless liquid in 88% (5.65 g, 27.6 mmol) yield.
19F NMR (CDCl3): d À101.5 (dd, J = 77, 31 Hz), À116.2
1
(dd, J = 111, 74, 1F), 177.0 (dd, J = 110, 32 Hz, 1F); H
NMR (CDCl3): d 7.33 (d, J = 8 Hz, 2H), 2.35 (s, 3H); 13C
NMR (CDCl3): d 155.2 (d, J = 252, 37 Hz), 137.7 (ddt,
J = 249, 50, 30 Hz), 131.6 (s), 129.0 (d, J = 3 Hz), 127.5 (dd,
J = 26, 6 Hz), 126.8 (t, J = 9 Hz), 118.8 (dt, J = 76, 38 Hz),
119.9 (m); HRMS: calcd for C10H5F7 258.0270, found
258.0279.
b.p.: 50 8C/8 mm Hg; reported 89–90 8C/27 mm Hg [35].
1
19F NMR (CDCl3): d À73.7 (d, J = 6 Hz, 3F); H NMR
(CDCl3): d 7.37 (d, J = 8 Hz 2H), 7.20 (d, J = 8 Hz, 2H),
5.05 (q, J = 7 Hz, 1H), 2.3 (s, 3H); 13C NMR (CDCl3): d
140.3 (s), 129.5 (s), 129.3 (s), 128.6 (s), 123.5 (q,
J = 279 Hz), 58.7 (q, J = 34 Hz), 21.2 (s).

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3.30. Synthesis of p-MeOC6H4CHClCF3
3.34. Synthesis of 1-chloro-1-(2-thienyl)-2,2,2-
trifluoroethane (n.c.)
Following the general procedure, from 1-(4-methoxyphe-
nyl)-2,2,2-trifluoroethan-1-ol (9.0 g, 43.7 mmol), obtained 1-
chloro-1-(4-methoxyphenyl)-2,2,2-trifluoroethane as a color-
less liquid in 80% (7.9 g, 35.3 mmol) yield.
Following the general procedure, from 1-(2-thienyl)-
2,2,2-trifluoroethan-1-ol (3.23 g, 17.75 mmol) obtained 1-
chloro-1-(2-thienyl)-2,2,2-trifluoroethane as a colorless
liquid in 90% (3.2 g, 16.0 mmol) yield.
b.p.: 81–82 8C/12 mm Hg; reported 57.5–59.5 8C/
1 mm Hg [35].
b.p.: 56 8C/14 mm Hg.
1
1
19F NMR (CDCl3): d À73.9 (d, J = 7 Hz, 3F); H NMR
19F NMR (CDCl3): d À74.3 (d, J = 7 Hz, 3F); H NMR
(CDCl3): d 7.40 (d, J = 8, 2H), 6.90 (m, 2H), 5.05 (q,
J = 7 Hz, 1H), 3.78 (s, 3H); 13C NMR (CDCl3): d 160.9 (s),
130.1 (s), 124.2 (s), 123.5 (q, J = 279.1 Hz), 114.3 (s), 58.5
(q, J = 34.5 Hz), 55.3 (s); GC–MS: 226 (M+ + 2) (38), 224
(M+) (80), 190 (36), 189 (100), 157 (47), 155 (82), 139 (90),
77 (40).
(CDCl3): d 7.42 (dd, J = 7, 5 Hz, 1H), 7.24 (d, J = 7 Hz, 1H),
7.01 (dd, J = 5, 4 Hz, 1H), 5.42 (q, J = 7 Hz, 1H); 13C NMR
(CDCl3): d 134.2 (s), 129.7 (s), 128.7 (s), 127.2 (s), 123.2 (q,
J = 280 Hz), 57.9 (q, J = 36 Hz); HRMS: calcd for
C6H4F335ClS 199.9674, found 199.9674; calcd for
C6H4F337ClS 201.9645, found 201.9648.
3.35. Synthesis of C6H5CHClCF2CF3 (n.c.)
3.31. Synthesis of m-BrC6H4CHClCF3 (n.c.)
Following the general procedure, from 1-phenyl-
2,2,3,3,3-pentafluoropropan-1-ol (8.75 g, 38.7 mmol),
obtained 1-chloro-1-phenyl-2,2,3,3,3-pentafluoropropane
as a colorless liquid in 81% (7.62 g, 31.2 mmol) yield.
b.p.: 52 8C/15 mm Hg.
Following the general procedure, from 1-(3-bromophe-
nyl)-2,2,2-trifluoroethan-1-ol (10.2 g, 39.9 mmol), obtained
1-chloro-1-(3-bromophenyl)-2,2,2-trifluoroethane as a col-
orless liquid in 89% (9.7 g, 35.4 mmol) yield.
b.p.: 75–77 8C/9 mm Hg.
19F NMR (CDCl3): d À80.9 (s, 3F), À119.5 (dd, J = 269,
12 Hz, 1F), 120.2 (dd, J = 269, 12 Hz, 1F); 1H NMR
(CDCl3): d 7.35–7.49 (m, 5H), 5.15 (t, J = 13 Hz, 1H); 13C
NMR (CDCl3); d 132.3 (s), 130.4 (s), 129.3 (s), 129.0 (s),
119.0 (tq, J = 288, 35 Hz), 112.8 (tq, J = 260, 36 Hz), 57.7
(t, J = 24 Hz). HRMS: calcd for C9H6F535Cl 244.0078,
found 244.0081, calcd for C9H6F537Cl 246.0049, found
246.0046.
1
19F NMR (CDCl3): d À73.6 (d, J = 6 Hz, 3F); H NMR
(CDCl3): d 7.65 (s, 1H), 7.55 (d, J = 8 Hz, 1H), 7.41 (d,
J = 8 Hz, 1H), 7.25 (t, J = distorted, 1H); 13C NMR
(CDCl3): d 134.2 (s), 133.3 (s), 132.1 (s), 131.8 (s),
130.3 (s), 127.5 (s), 123.2 (q, J = 280 Hz), 57.9 (q,
J = 35 Hz).
3.32. Synthesis of m-F3CC6H4CHClCF3
3.36. Synthesis of C6H5CHClCF2CF2CF3 (n.c.)
Following the general procedure, from 1-(3-trifluoro-
methylphenyl)-2,2,2-trifluoroethan-1-ol (13.75 g, 56.35
mmol), obtained 1-chloro1-(3-trifluoromethylphenyl)-
2,2,2-trifluoroethane in 79% (11.6 g, 44.27 mmol) yield.
b.p.: 41–44 8C/9 mm Hg; reported 75.5–76.5 8C/
25 mm Hg [35].
Following the general procedure, from 1-phenyl-
2,2,3,3,4,4,4-heptafluorobutan-1-ol (7.0 g, 25.36 mmol),
obtained 1-chloro-1-phenyl-2,2,3,3,3-pentafluorobutane as
a colorless liquid in 89% (6.6 g, 22.44 mmol) yield.
b.p.: 54 8C/15 mm Hg.
19F NMR (CDCl3): d À63.4 (s, 3F), À73.9 (d, J = 6 Hz,
19F NMR (CDCl3): d À81.2 (t, J = 10 Hz, 3F), À116.2
1
3F); H NMR (CDCl3): d 7.76 (s, 1H), 7.69 (d, J = 8 Hz,
1
(m, 2F), 124.1 (s, 2F); H NMR (CDCl3): d 7.36–7.49 (m,
5H), 5.23 (t, J = 13 Hz, 1H); HRMS: calcd for C10H6F735Cl
2H), 7.55 (t, J = 8 Hz, 1H), 5.16 (q, J = 7 Hz, 1H). HRMS:
calcd for C9H5F635Cl 261.9984, found 261.9979; calcd for
C9H5F637Cl 263.9954, found 263.9957.
37
294.0046, found 294.0040; calcd for C10H6F7 Cl
295.0080, found 295.0052.
3.33. Synthesis of C10H7CHClCF3 (n.c.)
3.37. Synthesis of PhCHClCF2Cl
Following the general procedure, from 1-naphthyl-2,2,2-
trifluoroethan-1-ol (10.0 g, 44.2 mmol), obtained 1-chloro-
1-naphthyl-2,2,2-trifluoroethane as a colorless liquid in 85%
(9.2 g, 37.7 mmol) yield.
Following the general procedure, from 2-chloro-1-
phenyl-2,2-difluoroethan-1-ol (10.0 g, 52.0 mmol), obtained
1,2-dichloro-1-phenyl-2,2-difluoroethane as a colorless
liquid in 87% (9.5 g, 45.1 mmol) yield.
b.p.: 106–108 8C/12 mm Hg.
b.p.: 65 8C/8 mm Hg; reported 200 8C [44].
19F NMR (CDCl3): d À72.2 (bs, 3F); 1H NMR (CDCl3): d
7.81–7.97 (m, 4H), 7.45–7.62 (m, 3H), 6.06 (q, J = 6.3 Hz,
1H); HRMS: calcd for C12H7F235Cl (M+–HF) 224.0204,
found 224.0204.
19F NMR (CDCl3): d À58.0 (dd, J = 162, 6 Hz, 1F),
À61.3 (dd, J = 162, 11 Hz); 1H NMR (CDCl3): d 7.30–7.50
(m, 5H), 5.2 (q, J = 7 Hz, 1H); 13C NMR: 133.1 (s), 131.2
(s), 129.2 (s), 128.9 (s), 127.3 (t, J = 296 Hz), 64.6 (t,

R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
1183
J = 28 Hz); GC–MS: 212 (M+ + 2) (37), 210 (M+) (45), 175
(42), 140 (26), 139 (28), 125 (100), 89 (38).
3.43. Synthesis of m-BrC6H4CCl CF2
Dehydrofluorination of 1-chloro-1-(3-bromophenyl)-2,2,
2-trifluoroethane (5.44 g, 20.0 mmol) with LHMDS
(22.5 mmol), followed by workup and distillation produced
m-bromo-1-chloro-2,2-difluorostyrene as a colorless liquid
in 78% (3.91 g, 15.51 mmol) yield.
3.38. General procedure for the dehydrofluorination of
1-chloro-1-phenyl-2,2,2-trifluoroethane
The dehyrofluorination of 1-chloro-1-phenyl-2,2,2-tri-
fluoroethane was performed under conditions similar to the
dehydrofluorination of 1-phenyl-1,2,2,2-tetrafluoroethane.
b.p.: 75–77 8C at 12 mm Hg.
To
a
solution of 1-chloro-1-aryl-2,2,2-trifluoroethane
3.44. Synthesis of m-CF3C6H4CCl CF2
(25.0 mmol) in THF (25 mL), LHMDS (27.5 mmol) was
slowly added maintaining the temperature around 15 8C.
The reaction was worked up after completion and the crude
product obtained was purified either by fractional distillation
using an 8 cm vigreux column or by column chromato-
graphy. All the 1-chloro-2,2-trifluorostyrenes prepared were
fully characterized and were in agreement with the spectral
data of the styrenes prepared by an alternative method
[22,24].
Dehydrofluorination of 1-chloro-(3-trifluoromethylphe-
nyl)-2,2,2-trifluoroethane (4.56 g, 20.0 mmol) with LHMDS
(22.5 mmol), followed by workup and distillation produced
m-trifluoromethyl-1-chloro-2,2-difluorostyrene as a color-
less liquid in 68% (3.28 g, 13.6 mmol) yield.
b.p.: 51–53 8C at 12 mm Hg.
3.45. Synthesis of C10H7CCl CF2 (n.c.)
3.39. Synthesis of C6H5CCl CF2
Dehydrofluorination of 1-chloro-1-naphthyl-2,2,2-tri-
fluoroethane (3.66 g, 15.0 mmol) with LHMDS (17.25
mmol), followed by workup and chromatography over
silica gel, eluting with hexane, produced 1-chloro-1-
naphthyl-2,2-difluoroethene as a colorless liquid in 92%
(3.3 g, 13.8 mmol) yield.
Dehydrofluorination of 1-chloro-1-phenyl-1,2,2,2-tri-
fluoroethane (4.85 g, 25.0 mmol) with LHMDS (27.5
mmol), followed by workup and distillation afforded 1-
chloro-2,2-difluorostyrene as a colorless liquid in 74%
(3.2 g, 18.4 mmol) yield.
19F NMR (CDCl3): d À86.3 (d, J = 34 Hz, 1F), À88.4 (d,
1
b.p.: 42–44 8C at 9 mm Hg (reported 100 8C at
100 mm Hg).
J = 33 Hz, 1F); H NMR (CDCl3): d 7.99 (d, 2H), 7.85 (t,
distorted, 2H), 7.40–7.57 (m, 3H); 13C NMR (CDCl3): d
154.4 (dd, J = 290, 286 Hz), 133.9 (s), 131.3 (s), 130.7 (s),
129.0 (s), 128.9 (s), 127.9 (d, J = 3 Hz), 127.2 (s), 126. 6 (s),
125.4 (s), 124.7 (s), 90.5 (dd, J = 43.8, 23.3 Hz); HRMS:
C12H7F235Cl 224.0204, found 224.0205; calcd for
C12H7F237Cl 226.0175, found 226.0172.
3.40. Synthesis of p-ClC6H4CCl CF2
Dehydrofluorination of 1-chloro-1-(4-chlorophenyl)-
2,2,2-trifluoroethane (4.56 g, 20.0 mmol) with LHMDS
(22.5 mmol), followed by workup and distillation afforded
p-chloro-1-chloro-2,2-difluorostyrene as a colorless liquid
in 79% (3.3 g, 15.86 mmol) yield.
3.46. Synthesis of 1-chloro-1-(2-thienyl)-2,2-
difluoroethene
b.p.: 65–68 8C at 9 mm Hg.
Dehydrofluorination of 1-chloro-1-(2-thienyl)-2,2,2-tri-
fluoroethane (1.5 g, 7.5 mmol) with LHMDS (8.25 mmol),
followed by workup and chromatography over silica gel
produced 1-chloro-1-(2-thienyl)-2,2-difluoroethene as a
colorless liquid in 87% (1.18 g, 6.56 mmol) yield.
3.41. Synthesis of p-MeC6H4CCl CF2
Dehydrofluorination of 1-chloro1-(4-methylphenyl)-2,2,
2-trifluoroethane (4.16 g, 20.0 mmol) by LHMDS
(22.5 mmol), followed by workup and distillation produced
p-methyl-1-chloro-2,2-difluorostyrene as a colorless liquid
in 81% (3.05 g, 16.2 mmol) yield.
3.47. Synthesis of (E) and (Z) 1-chloro-1-phenyl-
2,3,3,3-tetrafluoroprop-1-ene (n.c.)
b.p.: 56–58 8C at 12 mm Hg.
Dehydrofluorination of 1-chloro-1-phenyl-2,2,3,3,3-pen-
talfluoropropane (3.8 g, 15.57 mmol) with LHMDS
(17.13 mmol), followed by workup and column chromato-
graphy over silica gel, eluting with hexane, produced 89:11
mixture of isomeric 1-chloro-1-phenyl-2,3,3,3-tetrafluoro-
propene as a colorless liquid in 87% (3.02 g, 13.5 mmol)
yield.
3.42. Synthesis of p-MeOC6H4CCl CF2
Dehydrofluorination of 1-chloro-1-(4-methoxyphenyl)-
2,2,2-trifluoroethane (4.48 g, 20.0 mmol) with LHMDS
(22.5 mmol), followed by workup and chromatography
over silica gel, eluting with 3% ethyl acetate/hexane,
afforded p-methoxy-1-chloro-2,2-difluorostyrene as a color-
less liquid in 73% (2.98 g, 14.6 mmol) yield.
19F NMR (CDCl3): for the major isomer: d À66.1 (d,
J = 7 Hz, 2.7F), À125.8 (q, J = 7 Hz, 0.9F); for minor

1184
R. Anilkumar, D.J. Burton / Journal of Fluorine Chemistry 126 (2005) 1174–1184
[10] D.R. James, US Patent, 4,335,137, Chem. Abstr. 97 (1982) 140228c.
[11] P. Massardo, G. Bettarini, G. Giovarruscio, P. Piccardi, F. Reggiori, V.
Caprioli, EP 123,302, Chem. Abstr. 102 (1985) 95427f.
[12] P. Massardo, F. Rama, P. Piccardi, V. Caprioli, EP 123,302, Chem.
Abstr. 106 (1987) 196060u.
isomer: À65.3 (d, J = 11 Hz, 0.3F), À120.0 (q, J = 12 Hz,
0.1F); 1H NMR (CDCl3): d 7.58 (m, 2H), 7.35–7.45 (m, 3H);
HRMS: calcd for C9H5F435Cl 224.0016, found 224.0015;
calcd for C9H5F437Cl 225.9986, found 225.9988.
[13] T.S. Nikitina, Russ. Chem. Rev. 59 (1990) 575–589.
[14] T. Narita, T. Hagiwara, H. Hamana, K. Shibasaki, I. Hiruta, J. Fluorine
Chem. 71 (1995) 151–153.
3.48. Synthesis of (E) and (Z) 1-chloro-1-phenyl-
2,3,3,4,4,4-hexafluorobut-1-ene (n.c.)
[15] T. Aoki, J. Watanabe, Y. Ishimoto, E. Oikawa, Y. Hayakawa, M.
Nishida, J. Fluorine Chem. 59 (1992) 285–288.
Dehydrofluorination of 1-chloro-1-phenyl-2,2,3,4,4,4-
heptafluorobutane (3.5 g, 11.9 mmol) with LHMDS
(13.1 mmol), followed by workup and column chromato-
graphy over silica gel, eluting with hexanes produced a 75: 25
mixture of isomeric 1-chloro-1-phenyl-2,3,3,4,4,4-hexafluor-
obutene as colorless liquid in 84% (2.75 g, 10.0 mmol) yield.
19F NMR (CDCl3): for the major isomer: d À84.1(dt,
J = 6, 2 Hz, 2.25F), À116.7 (dq, J = 9, 4 Hz, 1.5 F), À124.1
(m, 0.75F); for the minor isomer: À83.7 (dt, J = 9, 2 Hz,
0.75F), À115.0 (dq, J = 14, 3 Hz, 0.5F), À117.5 (m, 0.25F);
1H NMR (CDCl3): d 7.58 (m, 2H), 7.34–7.45 (m, 3H);
HRMS: calcd for C10H5F635Cl 273.9984, found 273.9988,
calcd for C10H5F637Cl 275.9954 found 275.9941.
[16] C. Stone, T.S. Daynard, L.-Q. Hu, C. Mah, A.E. Steck, J. New Mater.
Electrochem. Syst. 3 (2000) 43–50.
[17] C. Stone, A.E. Steck, PCT Int. Appl. WO 2001058576.
[18] T. Momose, T. Kitazumi, I. Ishigaki, J. Okamoto, J. Appl. Polym. Sci.
39 (1990) 1221–1230.
[19] R. Wodzki, A. Narebska, J. Ceynowa, Angew. Makromol. Chem. 106
(1982) 23–35.
[20] R. Anilkumar, D.J. Burton, Tetrahedron Lett. 43 (2002) 2731–2733.
[21] A. Raghavanpillai, D.J. Burton, J. Org. Chem. 69 (2004) 7083–
7091.
[22] R. Anilkumar, D.J. Burton, Tetrahedron Lett. 43 (2002) 6979–6982.
[23] R. Anilkumar, D.J. Burton, J. Fluorine Chem. 125 (2004) 561–
566.
[24] R. Anilkumar, D.J. Burton, J. Fluorine Chem. 126 (2005) 457–463,
835–843.
[25] R. Anilkumar, D.J. Burton, Tetrahedron Lett. 44 (2003) 6661–6664.
[26] W.J. Middleton, J. Org. Chem. 40 (1975) 574–578.
[27] K.T. Dishart, R. Levine, J. Am. Chem. Soc. 78 (1956) 2268–2270.
[28] X. Creary, J. Org. Chem. 52 (1987) 5026–5030.
[29] R. Stewart, K.C. Teo, Can. J. Chem. 58 (1980) 2491–2496.
[30] K. Ramesh, D.R. Bellew, S.G.K. Prakash, J. Org. Chem. 56 (1991)
984–989.
Acknowledgement
We are grateful to the National Science Foundation for
support of this research work.
[31] P.L. Heinze, D.J. Burton, J. Org. Chem. 53 (1988) 2714–2720.
[32] D.J. Burton, J. Fluorine Chem. 23 (1983) 339–357.
[33] I. Tellier, R. Sauvetre, J.F. Normant, J. Organomet. Chem. 303 (1986)
309–315.
References
[34] D.J. Burton, A.L. Anderson, R. Takei, H.F. Koch, T.L.R. Shih, J.
Fluorine Chem. 16 (1980) 229–235.
[1] T. Fuchikami, Yuki Gosei Kagaku Kyokai Shi 42 (1984) 775–785.
[2] Y. Takeuchi, Yuki Gosei Kagaku Kyokai Shi 46 (1988) 145–159.
[3] M. Shimizu, T. Hiyama, Angew. Chem. Int. Ed. 44 (2005) 214–231.
[4] J.T. Welch, Tetrahedron 43 (1987) 3123–3197.
[5] W.B. Motherwell, B.C. Tozer, J. Chem. Soc. Chem. Commun. (1989)
1437–1439.
[35] R. Fuchs, J.G. Park, J. Am. Chem. Soc. 79 (1957) 993–994.
[36] J.T. Welch, S. Esawakrishnan, Fluorine in Bioorganic Chemistry,
Wiley, New York, 1991.
[37] M. Kuroboshi, T. Hiyama, Chem. Lett. (1990) 1607–1610.
[38] M. Kuroboshi, N. Yamada, Y. Takebe, T. Hiyama, Tetrahedron Lett. 36
(1995) 6271–6274.
[6] P.M. Weintraub, A.K. Holland, C.A. Gates, W.R. Moore, R.J. Resvick,
P. Bey, N.P. Peet, Bioorg. Med. Chem. 11 (2003) 427–431.
[7] I.A. McDonald, M.J. Lacoste, P. Bey, M.G. Palfreyman, M. Ziena, J.
Med. Chem. 28 (1985) 186–193.
[39] D.J. Burton, J.A. Headley, J. Fluorine Chem. 18 (1981) 323–356.
[40] R.N. Haszeldine, A.J. Mitchinson, R. Rowland, A.E. Tipping, J.
Chem. Soc. Perkin. Trans. 1 (1976) 517–525.
[41] P. Capriel, G. Binsch, Tetrahedron 35 (1979) 2661–2668.
[42] W. Dmowski, J. Fluorine Chem. 18 (1981) 25–30.
[43] H.J. Frohn, V.V. Bardin, Z. Anorg. Allg. Chem. 630 (2004) 1022–
1024.
[8] J.R. McCarthy, D.P. Mathews, D.M. Stemerick, E.W. Huber, P. Bey,
B.J. Lippert, R.D. Snyder, P.S. Sunkara, J. Am. Chem. Soc. 112 (1991)
7439–7440.
[9] M. Fujita, T. Hiyama, Yuki Gosei Kagaku Kyokai Shi. 45 (1987) 664–
671.
[44] J.J. Drysdale, W.D. Phillips, J. Am. Chem. Soc. 79 (1957) 319–322.