An improved and facile preparation of ω-SF5-(perflouroethyl)benzene (SF5CF2CF2C6H5)

Article abstract of DOI:10.1016/S0022-1139(02)00225-7

A high-yield preparation of SF₅CF₂CF₂C₆H₅ has been achieved via a two-step process: α,β,β-trifluorostyrene reacts with SF₅CF₂CF₂C₆H₅ (2) in high

Full text of DOI:10.1016/S0022-1139(02)00225-7

Journal of Fluorine Chemistry 118 (2002) 157–159
Short communication
An improved and facile preparation of o-SF -(perfluoroethyl)benzene
5
(
SF CF CF C H )
5 2 2 6 5
1
R.W. Winter , G.L. Gard
Department of Chemistry, Portland State University, Room 262, 1719 SW 10th Avenue, P.O. Box 751, Portland, OR 97207-0751, USA
*
Received 10 July 2002; received in revised form 5 September 2002; accepted 9 September 2002
Abstract
A high-yield preparation of SF CF CF C H has been achieved via a two-step process: a,b,b-trifluorostyrene reacts with SF Br to give the
5
2
2
6
5
5
intermediate product SF
yield.
5
CF
2 6 5 4 5 2 2 6 5
CFBrC H (1) which, when treated with AgBF in methylene chloride, produces SF CF CF C H (2) in high
#
2002 Elsevier Science B.V. All rights reserved.
Keywords: SF -fluoroalkyl aromatics; Sulfur hexafluoride derivatives
5
1
. Introduction
The replacement of fluorine in SF with organic substi-
tuents leads to compounds of the general formula RSF5.
heating SF CF CF I with a large excess of benzene for
5 2 2
14 days (145 8C in a 300 ml stirred Parr Bomb reactor);
yield 74.4% [9,11]. The SF CF CF I was prepared from
S F , ICF CF I and F C=CF [12] and the S F in turn
2 10 2 2 2 2 2 10
6
5
2
2
Organosulfur pentafluorides (RSF ) have a number of useful
5
from SF Br [13].
5
properties that include low wettability, low dielectric con-
stant, high thermal stability, high chemical resistance, low
refractive index and low surface energy [1–4]. The interest in
Therefore, in order to prepare SF CF CF C H (2), it is
5 2 2 6 5
advantageous to have a method that directly uses SF Br to
5
give an intermediate precursor that is easily and quickly
converted to the desired product.
RSF chemistry, where R is an aromatic group, has extended
5
to the fine chemical industry [5]; for example, Aldrich
Chemical Company, Oakwood Products Inc., Fluorochem,
USA, and Lancaster Synthesis Inc. now sell 3(4)-nitrophe-
nylsulfur pentafluoride. Also, patents incorporating the phe-
nylsulfur pentafluoride group have been issued [6].
2. Results
The preparation of SF CF CF C H is carried out in the
5
2
2 6 5
A starting point for preparing SF -aromatic derivatives
5
following two steps (Eqs. (1) and (2)):
involves using one of the primary reagents, SF C H ,
6 5
5
hn
SF OC H and more recently, SF (CF ) C H (n ¼ 2, 4,
SF Br þ CF ¼CFC H !SF CF CFBrC H
(1)
5
6
5
5
2 n
6
5
5
2
6
5
5
2
6
5
ð1Þ
6
, 8) [7–9]. In addition to the synthesis of SF (CF ) C H
5 2 n 6 5
(
a number of derivatives of SF CF CF C H (2); m-
n ¼ 2, 4, 6, 8), our laboratories have successfully prepared
5
2
2
6
5
CH Cl2
2
SF5CF2CFBrC6H5 þ AgBF4 ! SF5CF2CF2C6H5
SF CF CF C H X (X: NO , NH , N , NHC(O)CH , OH, I,
2
5
2
2
6
4
2
3
3
ð2Þ
Br, SO Cl, SO H, SO Na) [10,11]. Also, the preparation and
2
3
3
þ AgBr þ BF3
(2)
polymerization of m-SF CF CF C H Z (Z: OC(O)CH=CH
2
5
2
2
6
4
and CH=CH ) have been achieved [11].
2
In Eq. (2), the reaction is accompanied by the formation of
AgBr precipitate and a vigorous evolution of gaseous BF3.
The intermediate product (1) is a liquid at room tempera-
ture. Bromine in a benzylic position shows increased activity
that promotes halogen exchange. The infrared spectrum
Previously, we reported a multi-step and time-consuming
method for preparing SF CF CF C H (2) that involved
5
2
2 6 5
*
contains the characteristic absorption bands for the SF -
5
Corresponding author. Tel.: þ1-503-725-4274; fax: þ1-503-725-3888.
ꢀ
1
group (stretching bands at 853–917 cm and one of the
E-mail address: gardg@pdx.edu (G.L. Gard).
1
Co-corresponding author.
ꢀ1
deformation bands at 597 cm ) along with additional bands
0022-1139/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 2 ) 0 0 2 2 5 - 7

158
R.W. Winter, G.L. Gard / Journal of Fluorine Chemistry 118 (2002) 157–159
ꢀ
1
that support the assigned structure. The stretching bands for
the CF CF-group gives rise to strong absorption bands in the
The IR spectrum contained the following bands (cm ):
3070 (w), 3040 (vw), 1500 (w), 1453 (m), 1210 (ms, sh),
1195 (s), 1121 (m), 1095 (m), 1072 (ms), 1026 (wm), 917
(s), 876 (vs), 853 (s), 793 (m), 773 (m), 735 (m), 708 (vs),
2
095–1195 cm region. The 19F NMR spectrum for (1)
shows for the SF -group the expected AB pattern. The axial
ꢀ
1
1
5
4
fluorine atom (A) of the SF is a triplet of a nine-line pattern
5
694 (wm), 682 (m), 673 (ms), 640 (m), 624 (m), 597 (vs).
1
(
j , 70.6 ppm) and the equatorial fluorine atoms (B) is a
The H NMR spectrum (CDCl ) showed the following
3
A
19
skewed doublet (j , 47.3 ppm). The F NMR spectrum for
peaks: d ¼ 7:60 ppm (center of multiplet), 2H; d ¼
B
1
9
the CF -group is a complex AB pattern from which the
appropriate SF F –CF coupling (J
7:42 ppm (center of multiplet), 3H. F NMR spectrum
(CDCl ): SF (AB ): j ¼ 70:6 ppm (triplet of a nine-line
2
ꢁ 5:4 Hz) has been
4
A
2
ACF2
3
5
4
A
determined. This result along with integration of peak areas
provide evidence that the SF -group is attached to CF as
pattern), 1.0F; j ¼ 47:3 ppm (skewed doublet), 4.0F;
B
JAB ¼ 149 Hz, JACF ꢂ 5:4 Hz. j
¼ ꢀ85:8 ppm, center
5
2
2
CF
2
would be expected for a radical chain type addition product.
The major mass spectral peaks for (1) contain the parent
ion; additional peaks are found supporting the assigned
(AB system of multiplet), 2.0F; j ¼ ꢀ84:3 and ꢀ87.3 ppm;
JAB ¼ 200 Hz, doublet splitting is present in multiplets,
J ꢂ 5:5 Hz ¼ JFSF CF ; j
¼ ꢀ131:0 ppm (poorly resolv.
4
2
CFBr
þ
structure; in particular, the strong (M–Br) peak (56%) and
þ
multiplet), 1.0F, J ꢂ 11 Hz.
the strong (SF CF ) peak (45%) are found. The molecular
5
The major mass spectral peaks include (m/z, ion,
2
þ þ
rel.%): 366/364, (M) , 0.5%; 285, (M–Br) , 56%; 237/
weight of compound (1) was determined to seven significant
places by high-resolution mass spectrometry (HRMS).
þ þ
239, (M–SF ) , 9.1/8.8%; 177, (SF CF ) , 45%; 159,
5 5 2
19
1
þ
(MH–Br–SF ) , 9%; 158, (M–Br–SF ) , 100%; 157, (M–
5
þ
The spectral properties of SF CF CF C H ( F, H, IR)
5
5
2
2
6
5
þ þ
H–Br–SF ) , 8%; 127, (SF ) , 72%; 108, (CFC H ) , 16%;
5 5 6
þ
and GC–MS (R value and ion spectrum) matched an
f
5
þ þ
107, (CFC H ) , 21%; 89, (SF ) , 11%.
6 4 3
authentic sample [9].
þ
High-resolution mass spectrum: m ¼ 363:91706. Cal-
1
2
1
19 32 79
culated for C8 H5 F8 S Br: m ¼ 363:91676.
.2. Preparation of SF CF CF C H (2)
3
. Experimental
3
5
2
2 6 5
The reactant SF Br was prepared using SF , BrF , Br and
2
5
4
3
CsF [14]. The a,b,b-trifluorostyrene was obtained from the
SynQuest laboratories and was used as received. This mate-
rial is also readily prepared by the method of Burton [15];
additional syntheses are found in a review article by Nikitina
To a 150 ml Carius vessel equipped with a Teflon stirring
bar and a Kontes Teflon valve, containing 2.51 g
(12.9 mmol) of AgBF , 4.31 g (11.8 mmol) of (1) in
4
20.0 ml of CH Cl was added with stirring. A vigorous
2
2
[
[
16]. AgBF was prepared from AgF and BF in benzene
4
reaction occurred with the release of BF . The reaction,
3
3
17]. The infrared spectra of the reactants and products were
after stirring for 45 min in an ambient-temperature water
bath, was found to be complete (GC–MS spectrum showed
only (2) to be present). The reaction mixture was suction-
filtered and the filter cake washed with 20 ml of CH Cl ; the
obtained on a Perkin-Elmer 2000 FTIR operating at 1.0
cm resolution using KBr windows, 19F NMR spectra on a
ꢀ
1
Varian EM-390 spectrometer operating at 84.67 MHz, and
1
2
2
H NMR spectra on a Nicolet NM-500 (500 MHz). Mass
filtrate was passed through a short column of Kieselgel
(10 g) and eluted with CH Cl . The bulk of the solvent
spectra were obtained using a Hewlett-Packard HP5890
series II Gas Chromatograph equipped with a HP5970 mass
selective detector operating at 70 eV and a 30 m DB-5
column. The precise molecular weight was determined on
a Kratos MS 50TC; chemical ionization with methane.
2
2
was removed using a rotary evaporator; the residue was
transferred into a cold trap at ꢀ196 8C which when warmed
from ꢀ35 to ꢀ40 8C is pumped on in order to remove any
remaining solvent. The product residue (3.32 g, 10.9 mmol,
1
9
yield of 92%) was found to be identical in all aspects ( F,
1
3
.1. Preparation of SF CF CFBrC H (1)
5
H NMR, IR spectrum, GC–MS-identical R values and
f
5
2
6
spectra) with an authentic sample of SF CF CF C H [9].
5
2
2 6 5
To a 150 ml Carius vessel equipped with a Teflon stirring
bar and a Kontes Teflon valve, 4.80 g (30.3 mmol) of
F C=CFC H in 45 ml of CH Cl , and 11.6 g (56 mmol) of
2
Acknowledgements
6
5
2
2
SF Br were added via a vacuum transfer. This mixture was
5
stirred and irradiated (250-W sunlamp at a distance of 35 cm)
in an ice-bath. During irradiation, one-half of the solution
level was above the ice-bath. After 1.5 h, the mixture turned
brownish. The solution was irradiated for an additional 1.0 h;
GC–MS analysis showed the reaction to be complete. The
solvent was removed at atmospheric pressure; distillation of
the residue gave 7.89 g (21.6 mmol) of a clear, light peach-
color, product (1); bp 82–85 8C/11–12 Torr (71% yield).
We are grateful to the National Science Foundation (CHE-
9904316) for support of this work.
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