The application of novel methodology for the synthesis of o-, m-, and p-(SF5-perfluoroethyl) benzene derivatives

Article abstract of DOI:10.1016/S0022-1139(03)00086-1

The reaction of o-, m-, and p-F₂C=CFC₆ H₄X with SF₅Br produces an intermediate adduct, F₅SCF₂CFBrC₆H₄X, which, on treatment with AgBF₄, affords the first useful, high yield preparation of o-, m-, and p-F₅SCF₂ CF₂C₆H₄X.

Full text of DOI:10.1016/S0022-1139(03)00086-1

Journal of Fluorine Chemistry 122 (2003) 251–253
Short communication
The application of novel methodology for the synthesis of o-, m-,
and p-(SF5-perfluoroethyl) benzene derivatives
R.W. Wintera, R. Dodeana, J.A. Smitha, R. Anilkumarb, D.J. Burtonb,1, G.L. Garda,*
aDepartment of Chemistry, Portland State University, 1719 SW 10th Avenue, Portland, OR 97207, USA
bDepartment of Chemistry, University of Iowa, Iowa City, IA 52242, USA
Received 6 January 2003; received in revised form 5 March 2003; accepted 5 March 2003
Abstract
The reaction of o-, m-, and p-F2C¼CFC6H4X with SF5Br produces an intermediate adduct, F5SCF2CFBrC6H4X, which, on treatment with
AgBF4, affords the first useful, high yield preparation of o-, m-, and p-F5SCF2CF2C6H4X.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: SF5-fluoroalkyl aromatics; Sulfur hexafluoride derivatives; Trifluorostyrenes
1. Introduction
There are many known meta-, para- and several ortho-
derivatives of SF5C6H5 [13–15]. However, only a relatively
small number of meta-F5SCF2CF2C6H4X derivatives has
been prepared; there are no known ortho- or para-deriva-
tives [16,17]. In our laboratories, we have developed several
synthetic pathways for preparing F5SCF2CF2C6H5 [17,18];
the first method involves a multistep procedure for making
F5SCF2CF2I (1), which in turn is reacted with benzene while
the second method is a two-step process in which SF5Br is
reacted with CF2¼CFC6H5 and the addition product is then
treated with AgBF4. With F5SCF2CF2C6H5 (2), electrophilic
aromatic substitution reactions occur giving exclusively
meta derivatives. When aromatic compounds other than
benzene, such as toluene, are reacted with (1), only very
low yields of F5SCF2CF2-aryl products are obtained. Con-
sequently, this pathway did not lead to ortho- and para-
analogs.
The properties of organic compounds are often signifi-
cantly enhanced or modified by the incorporation of per-
fluoroalkyl groups [1–3]. Although a large body of work has
been published with compounds containing perfluoroalkyl
groups, only a small number of compounds containing an
F5S-group or F5S(CF2)n-groups has been prepared and
investigated, even though useful properties that range from
liquid crystals to pesticides to dielectrics are enhanced by
incorporation of the F5S-moiety [4]. In the liquid crystal
field, the F5S-group as a polar terminal group has produced a
new class of liquid crystals that have both very strong
dielectric anisotropy and moderately high clearing points
[5]. The first reported organic superconductor contained an
F5S-group [6]. Since this initial report, a number of F5S-
containing materials ranging from superconductivity to
metallic conductivity to semiconductivity have been
reported [7,8]. Polymeric F5S-containing imides with low
dielectric constants (2.51–3.00) have potential use in the
electronics industry [9]. When the surfactant properties of
the F5S-group have been compared to similar F3C-contain-
ing analogs, the F5S-group has been found to be superior for
lowering aqueous surface tension [10], and polymers con-
taining the F5S-moiety have exhibited fluorinated surfaces
with low wettability [11,12].
2. Results
The above limitations prompted us to seek a new, more
general route to the functionalized F5SCF2CF2C6H4X (o, m,
p) derivatives. The recent report of a low-cost general route
for the preparation of o-, m-, and p-trifluorostyrene deriva-
tives [19] (Scheme 1) suggested a general entry into the
preparation of o-, m-, and p-SF5CF2CF2C6H4X (Scheme 2).
Since the substituent in the styrene precursor can be ortho,
meta, or para, the F5S-analogs (4) can contain a variety of
ortho, meta or para atoms or groups. Interestingly, no
deactivating effect of ortho substituents in either reaction
* Corresponding authors. Fax: þ1-503-725-9525.
E-mail addresses: donald-burton@uiowa.edu (D.J. Burton),
gardg@pdx.edu (G.L. Gard).
1 Co-corresponding author. Fax: þ1-319-35-1270.
0022-1139/$ – see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-1139(03)00086-1

252
R.W. Winter et al. / Journal of Fluorine Chemistry 122 (2003) 251–253
Scheme 1. The preparation of trifluorostyrene derivatives [19].
tyrenes proceeded faster with alkyl or halogen substituents
(p-CH3, o-CH(CH3)2, o-F, m-Br, p-Br, and p-Cl) and less
readily with electron withdrawing substituents (o-CF3,
p-CF3, and p-NO2). Similar reactivity patterns were found
in the conversion of 3 to 4.
In conclusion, we have developed a simple, general route
to F5SCF2CF2C6H4X derivatives, where X can be a variety
of o, m, and p atoms or groups. This methodology avoids
S2F10, and since S2F10 is prepared from SF5Br, saves one
additional step, avoids the use of C2F4, and provides entry to
any pattern of aromatic substitution.
Scheme 2. The preparation of F5SCF2CF2C6H4X derivatives.
scheme was observed. Tables 1 and 2 summarize these
results.
For both reaction steps, a range of reactivities was
found—estimated by reaction times and temperatures for
complete reaction. The addition of SF5Br to the trifluoros-
3. Experimental
The reactant SF5Br was prepared using SF4, BrF3, Br2,
and CsF [20].
Table 1
Preparation of F5SCF2CFBrC6H4X (3)
A typical experimental procedure is described below.
The reactions were carried out in a 30 ml Carius tube
equipped with a Kontes PTFE valve and a PTFE coated
stirring bar. After evacuation, the Carius tube was filled with
argon. The trifluorostyrene derivative, dissolved in pentane
(1–2 g of the styrene in 3–5 ml pentane), and CH2Cl2 (5 ml)
were added to the Carius tube. After cooling to À196 8C, the
vessel was evacuated and up to 2 mol-equivalents of SF5Br
were added via vacuum transfer. The Carius tube was then
placed in a 0 8C circulating water bath under three 90 W sun
lamps at a distance of 15–20 cm. Completion of the reaction
was marked by a change of color from light yellow to red-
brown. The absence of a vinyl stretching frequency (1756–
1790 cmÀ1) in the infrared spectrum confirmed the total
consumption of the trifluorostyrene derivative. The pentane
and CH2Cl2 were removed by rotary evaporation and the
product isolated by silica gel chromatography (hexane as
eluant). Hexane and any residual solvents were removed
under vacuum to give the pure product (3). For example,
1.0 g (5.7 mmol) o-F-trifluorostyrene in 3 ml pentane, 5 ml
CH2Cl2, and 1.53 g (7.4 mmol) SF5Br were added to a 30 ml
Carius tube. The mixture was irradiated for 17 h at 0 8C. The
product was isolated by silica gel chromatography; yield
was 82%.
To a 30 ml Carius tube equipped with a Kontes Teflon
valve and a Teflon coated stirring bar, was added AgBF4.
Anhydrous CH2Cl2 (5 ml) was transferred to the Carius tube
under vacuum, and a ꢀ0.5 molar equivalent amount of 3 was
added under an argon atmosphere. The reaction mixture was
usually stirred at room temperature or with heating (cf.
Table 2). When GC–MS analysis indicated total consump-
tion of 3, the reaction mixture was cooled to room tempera-
ture, the solid phase removed by vacuum filtration and the
solid washed with 2–3 ml of CH2Cl2. The CH2Cl2 fractions
hv
!
Entry
F2C¼CFC6H4X þ F5SBr
3
CH2Cl2=0ꢁC
X
Conditions
Yield of 3 (%)a,b
1
2
3
4
5
6
7
8
9
m-Br
18 h
25 h
20 h
48 h
20 h
51 h
17 h
18 h
18 h
53
53
52
41
22c
80
82
74
67
p-Br
p-Cl
p-CH3
p-CF3
p-NO2
o-F
o-CF3
o-CH(CH3)2
a Isolated yield of 3.
b All products gave satisfactory 19F, 1H NMR and HRMS data
consistent with the assigned structure.
c Low yield due to volatility of product.
Table 2
Preparation of F5SCF2CF2C6H4X (4)
CH2Cl2
!
Entry
3 þ AgBF4
4
X
Conditions
Yield of 4 (%)a,b
1
2
3
4
5
6
7
8
9
m-Br
44 h/RT
99
98
97
38c
96
67
93
99
89
p-Br
21 h/0 8C ! RT
20 h/0 8C ! RT
2/3 h/80 8C
p-Cl
p-CH3
p-CF3
p-NO2
o-F
28 h/100 8C
46 h/138 8Cd
22.5 h/0 8C
o-CF3
o-CH(CH3)2
3 h/100 8C
4.5 h/À78 8C ! RT
a Isolated yield of 4.
b All products gave satisfactory 19F, 1H NMR and HRMS data
consistent with the assigned structure.
c Low yield due to loss in the filtration process.
d Boiling xylene (solvent).

R.W. Winter et al. / Journal of Fluorine Chemistry 122 (2003) 251–253
253
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were combined and separated by silica gel chromatogra-
phy—solvent removed under vacuum to give pure 4, iden-
[4] R. Winter, G.L. Gard, Functionalization of pentafluoro-l6-sulfanyl
(SF5) olefins and acetylenes, in: J.S. Thrasher, S.H. Strauss (Eds.),
Inorganic Fluorine Chemistry Towards the 21st Century, ACS
Symposium Series #555, Washington, DC, 1994 (Chapter 8).
[5] P. Kirsch, M. Bremer, A. Taugerbeck, T. Wallmichrath, Angew.
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1
tified by IR, 19F and H NMR and HRMS. For example,
0.98 g (2.6 mmol) of the above o-F adduct, 5.2 ml CH2Cl2,
and 0.89 g (4.6 mmol) AgBF4 were added to a 30 ml Carius
tube under an argon atmosphere. The reaction mixture was
stirred for 22.5 h at 0 8C; the solid phase was removed by
vacuum filtration and washed with small amounts of
CH2Cl2. The filtrate was passed through a short column
of silica gel in order to remove any polar constituents and the
eluate was concentrated under vacuum at À24 8C. The yield
of the product was 93%.
[6] U. Geiser, J.A. Schlueter, H.H. Wang, A.M. Kini, P.P. Sche, H.I.
Zakowicz, M.L. Van Zile, J.D. Dudek, J.M. Williams, J. Renn, M.H.
Whangbo, P.G. Nixon, R.W. Winter, G.L. Gard, J. Am. Chem. Soc.
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[7] J.A. Schlueter, B.H. Ward, U. Geiser, H.H. Wang, A.M. Kini, J.P.
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Mohtasham, G.L. Gard, Chem. Mater. 11 (2001) 2008.
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Parakka, S.Y. Thomas, J.M. Williams, P.G. Nixon, R.W. Winter, G.L.
Gard, H.-J. Koo, M.H. Whangbo, Chem. Mater. 12 (2000) 343.
[9] T.L. St. Clair, A.K. St. Clair, J.S. Thrasher, US Patent 5,220,070
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Acknowledgements
[10] J.C. Hansen, P.M. Savu, US Patent 5,286,352 (1994).
[11] R. Winter, P.G. Nixon, G.L. Gard, D.G. Castner, N.R. Holcomb, Y-H.
Hu, D.W. Grainger, Chem. Mater. 11 (1999) 3044.
We (PSU, UI) are grateful to the National Science Foun-
dation (CHE-9904316 and CHE-9820769) for support of
´
this work. We wish to thank Jeff Morre (Mass Spectrometry
[12] P.G. Nixon, R. Winter, D.G. Castner, N.R. Holcomb, D.W. Grainger,
G.L. Gard, Chem. Mater. 12 (2000) 3108.
Laboratory, Oregon State University, Corvallis, Oregon) for
obtaining the high resolution mass spectra (HRMS).
[13] W.A. Sheppard, J. Am. Chem. Soc. 84 (1962) 3064.
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