Reactions involving fluoride ion. Part 44.1 Synthesis, and chemistry of aromatics with bulky perfluoroalkyl substituents

Article abstract of DOI:10.1039/a808700h

The observable perfluoroalkyl carbanion la, generated by addition of fluoride ion to perfluoroalkene 1, reacts efficiently with benzyl bromide, and a range of related derivatives 3a-g, and this provides methodology for the preparation of aromatic rings wi

Full text of DOI:10.1039/a808700h

View Article Online / Journal Homepage / Table of Contents for this issue
Reactions involving fluoride ion. Part 44.1 Synthesis and chemistry
of aromatics with bulky perfluoroalkyl substituents
Richard D. Chambers,* Corinne Magron and Graham Sandford*
Department of Chemistry, University of Durham, South Road, Durham, UK DH1 3LE.
E-mail: r.d.chambers@durham.ac.uk
Received (in Cambridge) 6th November 1998, Accepted 11th December 1998
The observable perfluoroalkyl carbanion 1a, generated by addition of fluoride ion to perfluoroalkene 1, reacts
efficiently with benzyl bromide and a range of related derivatives 3a–g and this provides methodology for the
preparation of aromatic rings with large perfluoroalkyl substituents. Purification of the perfluoroalkylated products
4a–g was accomplished by selective extraction from the reaction medium by a perfluorocarbon fluid. Products
obtained upon nitration and bromination of 4a demonstrate that the orientation of electrophilic substitution in 4a is
controlled predominantly by the steric rather than electronic effects of the polyfluoroalkyl group. The methodology
was applied to the preparation of azo-dyes 15a–c that are completely soluble in perfluorocarbon fluids.
mediate perfluoroalkyl carbanions, e.g. 2a, can react with a
variety of electrophilic reagents leading to an extensive chem-
Introduction
The development of efficient methodology for the preparation
of organic molecules bearing perfluoroalkyl substituents is an
istry, which includes oligomerisations, negative Friedel–Crafts
reactions and rearrangements.16,17
important target because of the profound changes in physical,
In this paper, we describe the synthesis of a variety of per-
chemical and biological properties that can occur upon
fluoroalkylated benzyl systems using this methodology, in
which the electrophilic species are benzyl bromide or deriv-
atives, as a general route to the preparation of aromatic systems
containing bulky perfluoroalkyl substituents. Application of
these procedures to the synthesis of novel azo-dyes that are
completely soluble in perfluorocarbon fluids is described.
incorporation of a perfluoroalkyl group into an organic sub-
strate.2 For example, there are many pharmaceuticals and plant
protection agents3 which owe their enhanced biological activity
to the presence of a trifluoromethyl group in their structures.
Furthermore, long, highly lipophilic perfluoroalkyl chains can
impart valuable properties of oil (unique) and water repellency
to surfaces, leading to soil resistance, and this effect has been
exploited by the surfactant and textile treatment industries.4
Results and discussion
Perfluoroalkyl substituents can also markedly enhance the
We have established previously that perfluoroisopropyl anions
solubility of a substrate in perfluorocarbon fluids and this
2a, derived from the addition of fluoride ion to hexafluoro-
unusual property has been used to great effect recently in the
propene 2, can be trapped by a variety of electrophiles includ-
growing field of biphasic fluorous catalysis5,6 and fluorous
ing perfluoroalkenes16,17 and perfluoroheterocycles.18 However,
synthesis.7
our initial attempts at reaction between benzyl bromide 3a,
Although current methodology for the introduction of per-
hexafluoropropene 2 and fluoride ion, under a variety of condi-
fluoroalkyl substituents into organic molecules includes free
tions, were unsuccessful in that no perfluoroalkylated aromatic
radical8 (e.g. derived from perfluoroalkyl iodides), electro-
derivatives were obtained. Benzyl fluoride, derived from dis-
philic9 (e.g. ‘FITS’ reagents) and nucleophilic10 (e.g. CF3SiMe3)
placement of bromide by fluoride ion, and hexafluoropropene
perfluoroalkylating reagents, many established methodologies
dimer were obtained as the major products (Scheme 2).
are concerned with the preparation of trifluoromethyl
derivatives,11–13 while processes for the incorporation of longer
F3C
F3C
CF2CF3
F
chain perfluoroalkyl groups into aromatic systems remain less
developed.
CsF
+ CF2=CF-CF3
Ph
Br
Ph
F
+
In this series,1 we have been pursuing a ‘mirror image’ rela-
tionship between the role of fluoride ion in fluorocarbon chem-
istry with that of the proton in hydrocarbon chemistry. For
example, we established that addition of fluoride ion to some
perfluoroalkenes e.g. 1, can result in the preparation of stable,
observable perfluorinated carbanions14 1a (Scheme 1), and this
3a
2
(CF3)2CF
2a
Scheme 2
CF3
We deduced that these reactions were unsuccessful due to the
low concentration of perfluorocarbanion 2a in the reaction
mixture and, consequently, we explored the possibility of
increasing the concentration of perfluoroalkyl carbanions by
reacting preformed solutions of stable perfluorocarbanions
with benzyl bromide.
CF3
CF3
CF3CF3
F
CsF
C
CF2CF2CF3
Cs
CF3
1
1a
Scheme 1
chemistry can be considered to mirror the now classic develop-
ments by Olah and co-workers in carbocation chemistry.15
Several perfluoroalkyl carbanion species can be prepared by
the addition of fluoride ion to a fluoroalkene and the inter-
Solutions of perfluorocarbanion 1a were prepared by stirring
fluoroalkene 1 with dry caesium fluoride in sulfolane for 2
days at room temperature, after which 19F NMR analysis14 of
the reaction mixture indicated complete conversion to carb-
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290
283

View Article Online
Table 1 Perfluoroalkylation of benzyl bromide derivatives
anion 1a. Addition of 3a and heating at 60 ЊC for 6 days resulted
in the disappearance of carbanion 1a (as revealed by 19F NMR
analysis of a sample of the reaction mixture) and the appear-
ance of benzyl fluoride together with the perfluoroalkylated
product 4a (Scheme 3).
Br
RF
sulfolane
+
1a
60 °C, 6 d
R
R
3
4
RF = -C(CF3)2CF2CF2CF3
CF3
sulfolane
CF2CF2CF3
CF3
3a
+
1a
ArCH2Br 3
Product 4
Yield (%)
60 °C, 6 d
4a 58%
Br
RF
Scheme 3
34
Br
Br
4b
3b
Br
Isolation of perfluoroalkylated aromatic derivatives from
polar aprotic solvents such as sulfolane has, in the past, pre-
sented major practical difficulties.19,20 However, in this case, we
found that 4a could be selectively and completely extracted
from the sulfolane and benzyl fluoride impurity by a perfluoro-
carbon fluid, such as Fluorinert (3M Co.), because the large
perfluoroalkyl substituent renders the aromatic substrate 4a
preferentially soluble in such media while sulfolane is com-
pletely insoluble in the perfluorocarbon. This was established
by examination of the sulfolane layer by 19F NMR spectro-
scopy; only a residual fluorine signal corresponding to benzyl
fluoride could be detected. Removal of the perfluorocarbon
fluid by distillation gave crude perfluoroalkylated product 4a
which could be further purified by column chromatography.
A range of functionalised perfluoroalkylated benzyl deriv-
atives were prepared in a similar manner and 3-bromo-,
4-bromo-, 3-nitro- and 4-nitro-benzyl bromides 3c–f were
perfluoroalkylated efficiently (Table 1). However, perfluoro-
alkylation of 2-bromobenzyl bromide 3b gave lower yields of
product 4b, presumably due to steric hindrance by the bromine
atom ortho to the bromomethyl group.
RF
64
62
64
4c
3c
Br
Br
Br
3d
RF
4d
Br
Br
Br
RF
4e
3e
NO2
NO2
Br
3f
RF
4f
60
58
O2N
O2N
The possibility of incorporating two bulky perfluoroalkyl
chains into an aromatic substrate using this methodology was
demonstrated in reactions involving xylylene dibromides 5a–c.
By a similar process to that described above, reaction of 5a–c
with excess of carbanion 1a gave mixtures of the corresponding
bis-perfluoroalkylated products 6a–c and perfluoroalkyl fluor-
ide derivatives 7a–c (Table 2). 1,2-Xylylene dibromide 5a gave
predominantly the fluoride derivative 7a due to the steric hind-
rance of the large perfluoroalkyl group preventing attack by a
second carbanion 1a, whereas 1,3- and 1,4-xylylene dibromides
5b–c gave mainly the di-perfluoroalkylated derivatives 6b, c.
Similarly, the pyridyl system 8 gave a mixture of two products
9a,b upon reaction with carbanion 1a (Scheme 4).
Br
RF
3g
4g
ppm, a shift of about 1 ppm from the CH2 group in the
appropriate starting benzyl bromide derivative. Full assign-
ments of the 1H NMR spectra were accomplished with the aid
of NOE and H–1H COSY experiments. For example, in an
1
NOE experiment on a sample of 4b, irradiation of the methy-
lene resonance showed an enhancement of the signal at 7.43
ppm which must, therefore, be attributed to the hydrogen atom
on the aromatic ring ortho to the -CH2RF group (H-3). The
unambiguous assignment of H-3, combined with information
+
1a
N
sulfolane
60 °C, 6 d
Br
Br
8
1
derived from a H–1H COSY experiment, which shows the
+
N
N
coupling between H-3 and the other ring hydrogen atoms,
1
RF
RF
RF
F
allowed a full interpretation of the H NMR spectrum and
interpretation of the 13C NMR spectrum followed simply from
(20%)
(33%)
1
a subsequent H–13C HETCOR experiment. Spectral data for
9a
9b
all products 4,6,7,9 synthesised by the present methodology
could be interpreted similarly.
RF = -C(CF3)2CF2CF2CF3
Scheme 4
Characterisation of the products
Chemistry of perfluoroalkylated derivatives
All products were fully characterised by elemental analysis,
mass spectrometry and NMR spectroscopy. The 19F NMR
spectra of all products consisted of four resonances at around
Ϫ62, Ϫ80, Ϫ106 and Ϫ125 ppm, with relative intensities of
6:3:2:2 respectively, consistent with the presence of the
-C(CF3)2CF2CF2CF3 group. In the 1H NMR spectra, the
methylene groups appear as characteristic singlets at around 3.5
We were interested in evaluating the effect of the -CH2RF group
on the reactivity of the aromatic ring in electrophilic substitu-
tion reactions.
Nitration of 4a by nitronium tetrafluoroborate in sulfolane21
gave a mixture of the ortho, meta and para nitro derivatives in
the ratio 1:3.8:3.8 (Scheme 5). Since both the meta-4e and
para-4f nitro derivatives had been prepared unambiguously
284
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290

View Article Online
Table 2 Polyperfluoroalkylation of xylylene dibromides
dominantly ortho and para products, but in this case, electro-
philic substitution occurs at all three possible sites and gives
similar amounts of the meta and para derivatives. Thus, it
appears that the RFCH2- group imparts little net electron-
donating or electron-withdrawing effect on the aromatic ring,
(also, see pKa measurements below) and the ratio of isomers
obtained must be largely governed by steric control, the least
hindered sites, meta and para, being most reactive. It is well
known that the steric demand of a substituent can have a great
effect on the ratios of isomers produced upon electrophilic sub-
stitution; for example compare ratios of isomers obtained in the
nitration of toluene and tert-butylbenzene.23
Br
+
1a
CH2Br
sulfolane
60 °C, 6 d
5
CH2RF
CH2F
CH2RF
+
CH2RF
6
7
RF = -C(CF3)2CF2CF2CF3
To confirm the lack of an overall electronic influence of the
RFCH2- group on the aromatic ring, we compared the pKa
values of the benzoic acid derivatives 10 with other related
acids. The acids 10 were prepared (Scheme 5) by selective
debromometallation of the bromobenzene derivatives 4c,d
using tert-butyllithium and reaction with solid carbon
dioxide.24 Surprisingly, deprotonation at the benzylic sites did
not occur, as observed in attempted deuterium exchange
reactions.
ArCH2Br
Products (% yield)
Br
Br
RF
RF
RF
F
(12%)
(66%)
5a
6a
7a
The pKa values of acids 10 and a series of related substituted
benzoic acid derivatives were measured, following literature
methods,25 in a dioxane–water solvent system at 24 ЊC, and the
results are depicted in Scheme 6. These measurements confirm
Br
RF
RF
Br
RF
F
5b
(56%)
(21%)
6b
7b
CO2H
CF3
CH2RF
CH3
Br
RF
RF
Br
RF
F
5c
CO2H
(59%)
(22%)
CO2H
5.98
CO2H
6.34
6c
7c
5.82
6.14
6.46
6.58
CH3
pKa
6.48
previously (Table 1), the identity of the products and the ratio
of isomers obtained were simple to deduce by GC–MS.
Also, bromination of 4a by bromine catalysed by ferric brom-
ide22 gave ortho-, meta- and para-bromobenzene derivatives in
the ratio 1:2:3 (Scheme 5).
CF3
F
CH2RF
CO2H
CO2H
CO2H
CO2H
RF
sulfolane
RF = -C(CF3)2CF2CF2CF3
+ NO2BF4
4a
30 °C, 1 h
Scheme 6
NO2
61%, o : m: p 1 : 3.8 : 3.8
that the -CH2RF group imparts little overall electronic influence
on the aromatic ring, as the pKa of 10b is identical with benzoic
acid itself, and is a result consistent with the observed orien-
tation of the electrophilic substitution reactions discussed
above.
RF
FeBr3
+ Br2
4a
The perfluoroalkylated acids 10 could be converted to the
corresponding acid chlorides 11 upon reaction with thionyl
chloride26 and esterification of 11a with cyclohexanol also
proceeded very efficiently to give 12 (Scheme 7). Cyclohexanol
can be considered as a model for cellulose and, therefore, we
consider that this series of reactions demonstrates that the
present methodology could be applied to the introduction of
perfluoroalkyl groups onto surfaces which can be rendered
nucleophilic for use in textile treatment.
Br
81%, o : m: p 1 : 2 : 3
ButLi, CO2
Et2O, –78 °C
RF
RF
Br
HOOC
4c m-Br
4d p-Br
10a m-COOH, 60%
10b p-COOH, 64%
Perfluoroalkylated anilines 13 were prepared (Scheme 7) by
reduction of the nitrobenzene derivatives 4e, f using hydrogen
and a platinum on carbon catalyst.27 The corresponding diazo-
nium salts formed efficiently upon reaction of the anilines with
nitrous acid and were coupled with several activated aromatic
substrates 14a–c to form three azo-dye derivatives (Scheme 8)
15a–c respectively.26 The azo-dyes were all shades of orange
in colour (extinction coefficients included in Experimental
RF = -C(CF3)2CF2CF2CF3
Scheme 5
Of course, we would expect an electron-withdrawing sub-
stituent attached to an aromatic ring to give mainly meta
derivatives and an electron-donating substituent to give pre-
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290
285

View Article Online
Packard 5890 series II gas chromatograph. Accurate mass
measurements were performed by the EPSRC Mass Spectro-
metry Service, Swansea, UK. IR spectra were recorded on a
Perkin-Elmer 1600 FT-IR spectrometer while elemental analy-
ses were obtained on either a Perkin-Elmer 240 or a Carlo Erba
Elemental Analyser. Melting points and boiling points were
recorded at atmospheric pressure and are uncorrected. Column
chromatography was performed using silica gel (Merck No.
9385) and silica plates (Merck) were used for TLC analysis. The
pKa values of acids 10 were measured using a Beckman research
pH meter in 1,4-dioxane–water (1:1 v/v) solution at 24 ЊC
according to literature methods.25
RF
RF
SOCl2
2 h
ClOC
HOOC
10a m-COOH
11a m-COCl, 80%
11b p-COCl, 82%
10b p-COOH
RF
–HCl
+
12
(91%)
11a
OH
O
O
RF
H2, Pt/C
EtOH, room temp.
Perfluoroalkylation reactions
RF
O2N
General procedure. A flask was charged with perfluoro-2-
methylpent-2-ene 1, dry caesium fluoride and sulfolane. The
solution was stirred continuously at 30–35 ЊC for 40 h and
monitored by 19F NMR until quantitative conversion of 1 to
the perfluoroalkyl-carbanion 1a was observed;14 δF (sulfolane)
Ϫ41.2 [6F, s, (CF3)2C], Ϫ79.7 (3F, s, CF3CF2), Ϫ92.0 (2F, s,
CF2CF2CF3), Ϫ125.4 (2F, s, CF2CF3). The aromatic bromide
(3a–g, 5a–c, 8) was added slowly under nitrogen to the mixture
which was then heated with stirring at 65 ЊC for 6 days. The
mixture was filtered and extracted by a perfluorocarbon fluid
such as Fluorinert FC-84 (3M Co.) (2 × 30 ml). The solvent
was cautiously removed by distillation under reduced pressure
to afford perfluoroalkylated product which could be further
purified by column chromatography on silica gel if required.
H2N
4e m-NO2
4f p-NO2
13a m-NH2, 85%
13b p-NH2, 82%
RF = -C(CF3)2CF2CF2CF3
Scheme 7
CH2RF
OH
HCl, NaNO2
N
N
13b
+
15a
(53%)
OH
14a
[(Perfluoro-2-methylpentan-2-yl)methyl]benzene 4a. Com-
pound 1 (16.8 g, 56 mmol), caesium fluoride (7.9 g, 52 mmol)
and benzyl bromide 3a (5.6 g, 33 mmol) in sulfolane (40 ml)
gave, after column chromatography using n-hexane–light
petroleum (1:1) as eluant, [(perfluoro-2-methylpentan-2-yl)-
OH
OH
N
N
HCl, NaNO2
15b
(48%)
CH2RF
methyl]benzene 4a14,28 (7.5 g, 58%) as a pale yellow liquid; νmax
/
+
13a
cmϪ1 3041 (Ar-H), 2964 (C-H), 1263 (C-F); δH 3.36 (2H, s,
CH2), 7.11 (5H, s, Ph); δF Ϫ62.7 [6F, s, C(CF3)2], Ϫ80.5 (3F, s,
CF2CF3), Ϫ106.4 (2F, s, CF2CF2CF3), Ϫ123.4 (2F, s, CF2CF3);
m/z (EIϩ) 410 (Mϩ, 4%), 91 (100), 69 (12).
SO3Na
SO3Na
14b
CH3
CH3
N
N
2-[(Perfluoro-2-methylpentan-2-yl)methyl]bromobenzene 4b.
Compound 1 (16.2 g, 54 mmol), caesium fluoride (7.9 g, 52
mmol) and 2-bromobenzyl bromide 3b (8.6 g, 34.6 mmol) in
sulfolane (40 ml) gave 2-[(perfluoro-2-methylpentan-2-yl)-
methyl]bromobenzene 4b (5.6 g, 34%) as a pale yellow liquid; bp
230–233 ЊC (Siwoloboff) (Found: C, 31.7; H, 1.2. C13H6BrF13
requires C, 31.9; H, 1.2%); νmax/cmϪ1 1220–1272 (C-F); δH 3.84
(2H, s, CH2), 7.13 (1H, t, 3J 7.9, H-5), 7.25 (1H, t, 3J 7.6, H-4),
7.43 (1H, d, 3J 7.9, H-3), 7.59 (1H, d, 3J 7.9, H-6); δF Ϫ61.5 [6F,
s, C(CF3)2], Ϫ80.6 (3F, s, CF2CF3), Ϫ107.9 (2F, s, CF2CF2CF3),
CN
HCl, NaNO2
CN
OH
15c
+
13a
(51%)
O
N
OH
O
N
CH2RF
Bu
14c
Bu
R
F = -C(CF3)2CF2CF2CF3
Scheme 8
section) and the presence of the large perfluoroalkyl group in
the structure of each azo-dye 15a–c, renders the dyes completely
soluble in perfluorocarbon fluids, such as Fluorinert (3M Co).
To the best of our knowledge, 15a–c represent the first azo-dyes
that are completely soluble in perfluorocarbon media.
2
Ϫ122.7 (2F, s, CF2CF3); δC {H} 31.7 (s, CH2), 61.9 [sept, JCF
25, C(CF3)2], 109.8 (tsex, 1JCF 272, 2JCF 37, CF2CF3), 115.1 (tt,
2
1
2
1JCF 270, JCF 33, CF2CF2CF3), 117.9 (qt, JCF 289, JCF 34,
1
CF2CF3), 122.2 [q, JCF 290, C(CF3)2], 127.1 (s, C-1), 127.2 (s,
C-4), 129.7 (s, C-5), 131.6 (s, C-2), 132.6 (s, C-3), 133.7 (s, C-6);
m/z (EIϩ) 490 (Mϩ, 12%), 488 (Mϩ, 13%), 171 (94), 169 (100),
109 (15), 90 (21), 69 (14).
Experimental
All starting materials were either obtained commercially
(Aldrich) or prepared by literature procedures, and all solvents
were dried before use. Sulfolane was distilled under vacuum
from sodium and stored over 4 Å molecular sieves under a
nitrogen atmosphere. NMR spectra were recorded in deuterio-
chloroform unless otherwise stated on either a Varian Gemini
200, a Varian VXR 400S or a Bruker AC250 NMR spectro-
meter with tetramethylsilane and trichlorofluoromethane as
internal standards. In 19F NMR spectra, upfield shifts are
quoted as negative. Coupling constants (J) are given in Hz.
Mass spectra were recorded on either a VG 7070E spectrometer
or a Fissons VG Trio 1000 spectrometer coupled with a Hewlett
3-[(Perfluoro-2-methylpentan-2-yl)methyl]bromobenzene 4c.
Compound 1 (16.2 g, 54 mmol), caesium fluoride (7.9 g, 52
mmol) and 3-bromobenzyl bromide 3c (8.5 g, 34.2 mmol)
in sulfolane (40 ml) gave 3-[(perfluoro-2-methylpentan-2-
yl)methyl]bromobenzene 4c (13.2 g, 64%) as a pale yellow
liquid; bp 234–236 ЊC (Siwoloboff) (Found: C, 31.8; H, 1.2.
C13H6BrF13 requires C, 31.9; H, 1.2%); νmax/cmϪ1 1220–1268
(C-F); δH 3.49 (2H, s, CH2), 7.16 (1H, t, 3J 7.6, H-5), 7.22 (1H,
3
3
d, J 7.2, H-4), 7.44 (1H, d, J 8.4, H-6), 7.45 (1H, s, H-2);
δF Ϫ62.5 [6F, s, C(CF3)2], Ϫ80.4 (3F, s, CF2CF3), Ϫ106.1 (2F, s,
CF2CF2CF3), Ϫ123.1 (2F, s, CF2CF3); δC {H} 32.1 (s, CH2), 61.7
286
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290

View Article Online
[sept, 2JCF 24, C(CF3)2], 109.8 (tsex, 1JCF 272, 2JCF 37, CF2CF3),
(C-F), 739 and 701 (C-H); δH 3.67 (2H, s, CH2), 7.34–7.48 (3H,
1
2
1
114.9 (tt, JCF 270, JCF 33, CF2CF2CF3), 117.7 (qt, JCF 290,
m, Ar-H), 7.73–7.80 (4H, m, Ar-H); δF Ϫ62.2 [6F, s, C(CF3)2],
Ϫ80.1 (3F, s, CF2CF3), Ϫ105.9 (2F, s, CF2CF2CF3), Ϫ122.8 (2F,
s, CF2CF3); δC {H} 32.8 (s, CH2), 61.6 [sept, 2JCF 25, C(CF3)2],
109.7 (tsex, 1JCF 270, 2JCF 37, CF2CF3), 114.9 (tt, 1JCF 270, 2JCF
1
2JCF 34, CF2CF3), 122.0 [q, JCF 290, C(CF3)2], 122.3 (s, C-1),
129.7 (s, C-5), 130.2 (s, C-4), 131.5 (s, C-6), 133.3 (s, C-3), 134.7
(s, C-2); m/z (EIϩ) 490 (Mϩ, 11%), 488 (Mϩ, 10), 171 (92), 169
(100), 109 (23), 90 (35), 69 (17).
1
2
33, CF2CF2CF3), 117.7 (qt, JCF 289, JCF 34, CF2CF3), 122.1
1
[q, JCF 291, C(CF3)2], 126.3, 126.5, 127.5, 127.8, 127.9, 128.3,
128.8, 131.2, 132.8, 133.0 (all s, all Ar-C); m/z (EIϩ) 460 (Mϩ,
4-[(Perfluoro-2-methylpentan-2-yl)methyl]bromobenzene 4d.
Compound 1 (16.2 g, 54 mmol), caesium fluoride (7.9 g, 52
mmol) and 4-bromobenzyl bromide 3d (8.9 g, 36 mmol) in sul-
folane (40 ml) gave 4-[(perfluoro-2-methylpentan-2-yl)methyl]-
bromobenzene 4d (10.8 g, 62%) as a pale yellow liquid; bp
244 ЊC (Siwoloboff) (Found: C, 31.9; H, 1.2. C13H6BrF13
requires C, 31.9; H, 1.2%); νmax/cmϪ1 1269 (C-F), 1220 (C-F),
700 (C-Br); δH 3.49 (2H, s, CH2), 7.16 (2H, AX, JAX 8.4, H-2),
7.44 (2H, AX, JAX 8.4, H-3); δF Ϫ62.9 [6F, s, C(CF3)2], Ϫ80.8
(3F, s, CF2CF3), Ϫ106.6 (2F, s, CF2CF2CF3), Ϫ123.6 (2F, s,
12%), 141 (100), 115 (15), 71 (10).
1,2-Bis[(perfluoro-2-methylpentan-2-yl)methyl]benzene 6a and
1-fluoromethyl-2-[(perfluoro-2-methylpentan-2-yl)methyl]-
benzene 7a. Compound 1 (12.3 g, 41 mmol), caesium fluoride
(6.0 g, 39.4 mmol) and 1,2-xylylene dibromide 5a (3.23 g, 12.3
mmol) in sulfolane (30 ml) gave, after column chromatography
on silica gel using n-hexane–light petroleum (bp 40–60 ЊC)
(1:1) as eluant, 1,2-bis[(perfluoro-2-methylpentan-2-yl)methyl]-
benzene 6a (1.1 g, 12%) as a pale yellow liquid; bp 264 ЊC
(Siwoloboff); RF 0.4 (Found: Mϩ, 742.021000. C20H8F29
requires Mϩ, 742.021084); δH 3.65 (2H, s, CH2), 7.2–7.4 (4H, m,
Ar-H); δF Ϫ61.7 [6F, s, C(CF3)2], Ϫ80.4 (3F, s, CF2CF3), Ϫ107.6
(2F, s, CF2CF2CF3), Ϫ123.0 (2F, s, CF2CF3); δC 27.3 (s, CH2),
60.5 [m, C(CF3)2], 108.4 (tsex, 1JCF 272, 2JCF 33, CF2CF3), 113.9
(tt, 1JCF 270, 2JCF 34, CF2CF2CF3), 116.5 (qt, 1JCF 290, 2JCF 34,
2
CF2CF3); δC {H} 32.1 (s, CH2), 62.4 [sept, JCF 24, C(CF3)2],
109.6 (tsex, 1JCF 272, 2JCF 38, CF2CF3), 114.8 (tt, 1JCF 270, 2JCF
1
2
32, CF2CF2CF3), 117.5 (qt, JCF 289, JCF 33, CF2CF3), 121.9
1
[q, JCF 290, C(CF3)2], 122.5 (s, C-1), 129.9 (s, C-4), 131.4
(s, C-3), 133.1 (s, C-2); m/z (EIϩ) 488 (Mϩ, 3%), 490 (Mϩ, 3), 201
(11), 181 (15), 169 (100), 151 (15), 109 (21), 69 (85).
1
CF2CF3), 120.9 [q, JCF 291, (CF3)2C], 127.1 (s, C-4), 130.5 (s,
3-[(Perfluoro-2-methylpentan-2-yl)methyl]nitrobenzene
4e.
C-1), 131.3 (s, C-3); m/z (EIϩ) 423 (Mϩ Ϫ C6F13, 42%), 181 (27),
123 (86), 104 (42), 93 (17), 69 (100), and 1-fluoromethyl-2-
(perfluoro-2-methylpentan-2-yl)benzene 7a (3.6 g, 66%) as a
pale yellow liquid; bp 180 ЊC (Siwoloboff); RF 0.2 (Found: C,
38.2; H, 1.9. C14H8F14 requires C, 38.0; H, 1.8%); λmax(n-hexane)/
nm (ε/dm3 molϪ1 cmϪ1) 221 (1331), 267 (285); νmax/cmϪ1 3038
(Ar-H), 2924 (C-H), 1275–1220 (C-F), 734 (C-H); δH 3.75 (2H,
Compound 1 (31.0 g, 107 mmol), caesium fluoride (15.0 g, 99
mmol) and 3-nitrobenzyl bromide 3e (13.5 g, 62.6 mmol) in
sulfolane (40 ml) gave 3-[(perfluoro-2-methylpentan-2-yl)-
methyl]nitrobenzene 4e (18.2 g, 64%) as a pale yellow liquid; bp
>250 ЊC (decomp., Siwoloboff) (Found: C, 34.5; H, 1.3; N,
3.0. C13H6F13NO2 requires C, 34.3; H, 1.3; N, 3.0%); νmax/cmϪ1
1537 (N᎐O), 1353 (N᎐O), 1243 (br, C-F); δ (CD3CN) 3.80
᎐
᎐
2
H
s, CH2), 5.48 (2H, d, JHF 47, CH2F), 7.3–7.4 (4H, m, Ar-H);
(2H, s, CH2), 7.58 (1H, t, 3J 8.0, H-5), 7.75 (1H, d, 3J 7.6, H-4),
δF Ϫ61.5 [6F, s, C(CF3)2], Ϫ80.6 (3F, s, CF2CF3), Ϫ107.6 (2F, s,
3
8.19 (1H, d, J 8.8, H-6), 8.2 (1H, s, H-2); δF (CD3CN) Ϫ62.8
2
CF2CF2CF3), Ϫ122.8 (2F, s, CF2CF3), Ϫ205.3 (1F, t, JHF 47,
[6F, s, C(CF3)2], Ϫ81.0 (3F, s, CF2CF3), Ϫ106.4 (2F, s,
CF2CF2CF3), Ϫ123.3 (2F, s, CF2CF3); δC {H} (CD3CN) 32.6 (s,
2
CH2F); δC {H} 28 (s, CH2), 62.0 [sept, JCF 24, C(CF3)2], 82.7
1
1
2
(d, JCF 164, CH2F), 109.8 (tsex, JCF 272, JCF 38, CF2CF3),
2
1
2
CH2), 61.7 [sept, JCF 24, C(CF3)2], 110.6 (tsex, JCF 272, JCF
1
2
1
115.1 (tt, JCF 270, JCF 33, CF2CF2CF3), 117.8 (qt, JCF 289,
1
2
37, CF2CF3), 115.9 (tt, JCF 270, JCF 33, CF2CF2CF3), 118.6
2JCF 34, CF2CF3), 122.2 [q, JCF 290, C(CF3)2], 128.2 (s, C-2),
1
1
2
1
(qt, JCF 289, JCF 34, CF2CF3), 123.0 [q, JCF 290, C(CF3)2],
124.3 (s, C-6), 127.4 (s, C-2), 130.5 (s, C-5), 134.1 (s, C-3), 139.0
(s, C-4), 149.0 (s, C-1); m/z (EIϩ) 455 (Mϩ, 14%), 169 (17), 151
(25), 136 (62), 109 (100), 90 (20), 78 (38), 69 (77).
128.7 (s, C-4), 129.1 (d, 4JCF 3, C-5), 130.4 (d, 3JCF 7, C-6), 132.3
(s, C-3), 136.5 (d, JCF 15, C-1); m/z (EIϩ) 442 (Mϩ, 1%), 123
2
(100, Mϩ Ϫ C6F13).
1,3-Bis[(perfluoro-2-methylpentan-2-yl)methyl]benzene 6b and
1-fluoromethyl-3-[(perfluoro-2-methylpentan-2-yl)methyl]-
4-[(Perfluoro-2-methylpentan-2-yl)methyl]nitrobenzene
4f.
Compound 1 (41 g, 141 mmol), caesium fluoride (20 g, 133
mmol) and 4-nitrobenzyl bromide 3f (18.6 g, 86 mmol) in sul-
folane (40 ml) gave 4-[(perfluoro-2-methylpentan-2-yl)methyl]-
nitrobenzene 4f (23.4 g, 60%) as a pale yellow liquid; bp >250 ЊC
(decomp., Siwoloboff) (Found: C, 34.6; H, 1.2; N, 3.2.
C13H6F13NO2 requires C, 34.3; H, 1.3; N, 3.1%); νmax/cmϪ1 1609
benzene 7b. Compound 1 (16.0 g, 53 mmol), caesium fluoride
(7.98 g, 53 mmol) and 1,3-xylylene dibromide 5b (4.25 g, 16
mmol) in sulfolane (40 ml) gave, after column chromatography
on silica gel using n-hexane–light petroleum (bp 40–60 ЊC)
(1:1) as eluant, 1,3-bis[(perfluoro-2-methylpentan-2-yl)methyl]-
benzene 6b (6.8 g, 56%) as a pale yellow liquid; bp 286 ЊC
(Siwoloboff); RF 0.4 (Found: C, 32.0; H, 0.8. C20H8F26 requires
C, 32.3; H, 1.1%); λmax(n-hexane)/nm (ε/dm3 molϪ1 cmϪ1) 220
(1039), 261 (209); νmax/cmϪ1 3030 (br, Ar-H), 1264–1218 (C-F),
736 and 708 (C-H); δH 3.50 (4H, s, CH2), 7.2 (4H, m, Ar-H);
δF Ϫ62.9 [6F, s, C(CF3)2], Ϫ80.8 (3F, s, CF2CF3), Ϫ106.5 (2F, s,
CF2CF2CF3), Ϫ123.5 (2F, s, CF2CF3); δC {H} 32.8 (s, CH2),
(C᎐C), 1530 (N᎐O), 1351 (N᎐O), 1242 (br, C-F); δ (CD3CN)
᎐
᎐
᎐
H
3.78 (2H, s, CH2), 7.58 (2H, AX, JAX 8.8, H-3), 8.16 (2H, AX,
JAX 8.8, H-2); δF (CD3CN) Ϫ62.8 [6F, s, C(CF3)2], Ϫ81.0 (3F, s,
CF2CF3), Ϫ106.4 (2F, s, CF2CF2CF3), Ϫ123.3 (2F, s, CF2CF3);
2
δC {H} (CD3CN) 32.7 (s, CH2), 62.4 [sept, JCF 24, C(CF3)2],
1
2
1
109.6 (tsex, JCF 272, JCF 38, CF2CF3), 114.7 (tt, JCF 270,
2JCF 32, CF2CF2CF3), 117.5 (qt, JCF 289, JCF 33, CF2CF3),
121.9 [q, 1JCF 290, C(CF3)2], 124.1 (s, C-2), 133.9 (s, C-3), 139.6
(s, C-4), 148.8 (s, C-1); m/z (EIϩ) 455 (Mϩ, 27%), 151 (16), 136
(100), 109 (96), 89 (29), 78 (34), 69 (34).
1
2
2
1
2
61.8 [sept, JCF 25, C(CF3)2], 110.0 (tsex, JCF 271, JCF 38,
1
2
CF2CF3), 115.1 (tt, JCF 270, JCF 33, CF2CF2CF3), 117.9 (qt,
1JCF 289, JCF 34, CF2CF3), 122.3 [q, JCF 289, C(CF3)2], 128.3
(s, C-2), 131.5 (s, C-6), 131.7 (s, C-1), 135.1 (s, C-5); m/z (EIϩ)
742 (Mϩ, 1%), 423 (100), 253 (12), 235 (26), 185 (36), 165 (11),
104 (39), and 1-fluoromethyl-3-[(perfluoro-2-methylpentan-2-
yl)methyl]benzene 7b (1.5 g, 21%) as a pale yellow liquid; bp
207 ЊC (Siwoloboff); RF 0.2 (Found: C, 37.7; H, 1.6. C14H8F14
requires C, 38.0; H, 1.8%); λmax(n-hexane)/nm (ε/dm3 molϪ1
cmϪ1) 222 (1245), 267 (296); νmax/cmϪ1 3030br (Ar-H), 1263–
1218 (C-F), 734 and 707 (C-H); δH 3.56 (2H, s, CH2), 5.35 (2H,
d, 2JHF 48, CH2F), 7.3 (4H, m, Ar-H); δF Ϫ62.7 [6F, s, C(CF3)2],
Ϫ80.5 (3F, s, CF2CF3), Ϫ106.3 (2F, s, CF2CF2CF3), Ϫ123.3 (2F,
2
1
2-[(Perfluoro-2-methylpentan-2-yl)methyl]naphthalene
4g.
Compound 1 (7.3 g, 24.3 mmol), caesium fluoride (3.8 g, 25
mmol) and 2-bromomethylnaphthalene 3g (3.0 g, 13.5 mmol)
in sulfolane (40 ml) gave 2-[(perfluoro-2-methylpentan-2-yl)-
methyl]naphthalene 4g (3.6 g, 58%) as a pale yellow liquid; bp
284 ЊC (Siwoloboff) (Found: C, 44.3; H, 2.0. C17H9F13 requires
C, 44.3; H, 1.9%); λmax(n-hexane)/nm (ε/dm3 molϪ1 cmϪ1) 224
(19145), 276 (5744); νmax/cmϪ1 3064 (br, C-H), 1263–1218
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290
287

View Article Online
s, CF2CF3), Ϫ208.8 (1F, t, 2JHF 48, CH2F); δC {H} 32.6 (s, CH2),
Electrophilic substitution reactions
2
1
61.6 [sept, JCF 21, C(CF3)2], 84.2 (d, JCF 167, CH2F), 109.7
Nitration. A mixture consisting of 4a (2.1 g, 5 mmol) and
nitronium tetrafluoroborate (0.7 g, 5 mmol) in sulfolane (40 ml)
was stirred for 2 h at 30 ЊC. The mixture was extracted with
Fluorinert FC-84 (2 × 30 ml). The solvent was removed by
distillation under reduced pressure to afford crude product
(2.2 g). GC–MS analysis showed that the product consisted of
three isomers, 2-[(perfluoro-2-methylpentan-2-yl)methyl]nitro-
benzene 4h, 4e and 4f, in the ratio 1:3.8:3.8. Column chroma-
tography on alumina using hexane as eluant gave a mixture of
nitrobenzene derivatives 4e,f,h (1.42 g, 61%) as a pale yellow
liquid; spectral data were consistent with those obtained above
and no further separation and purification was attempted.
1
2
1
2
(tsex, JCF 271, JCF 37, CF2CF3), 114.9 (tt, JCF 270, JCF 33,
1
2
CF2CF2CF3), 117.7 (qt, JCF 289, JCF 33, CF2CF3), 122.1 [q,
1JCF 290, C(CF3)2], 127.3 (d, 3JCF 6, C-2), 128.6 (d, 4JCF 1, C-5),
130.6 (d, 3JCF 6, C-6), 131.5 (s, C-3), 131.9 (s, C-4), 136.5 (d, 2JCF
17, C-1); m/z (EIϩ) 442 (Mϩ, 5%), 123 (100).
1,4-Bis[(perfluoro-2-methylpentan-2-yl)methyl]benzene 6c and
1-fluoromethyl-4-[(perfluoro-2-methylpentan-2-yl)methyl]-
benzene 7c. Compound 1 (16.2 g, 54 mmol), dry caesium fluor-
ide (8.1 g, 53 mmol) and 1,4-xylylene dibromide 5c (4.25 g, 16
mmol) in sulfolane (45 ml) gave, after column chromatography
on silica gel using n-hexane–light petroleum (bp 40–60 ЊC)
(1:1) as eluant, 1,4-bis[(perfluoro-2-methylpentan-2-yl)methyl]-
benzene 6c (7.1 g, 59%) as a pale yellow liquid; bp 294 ЊC
(Siwoloboff); RF 0.4 (Found: C, 32.3; H, 0.9. C20H8F26 requires
C, 32.3; H, 1.1%); λmax(n-hexane)/nm (ε/dm3 molϪ1 cmϪ1) 222
(1064), 266 (326); νmax/cmϪ1 1263–1220 (C-F), 732 and 701
(C-H); δH 3.54 (4H, s, CH2), 7.26 (4H, s, Ar-H); δF Ϫ62.8 [6F, s,
C(CF3)2], Ϫ80.7 (3F, s, CF2CF3), Ϫ106.3 (2F, s, CF2CF2CF3),
Ϫ123.3 (2F, s, CF2CF3); δC {H} 32.3 (s, CH2), 61.6 [sept,
2JCF 25, C(CF3)2], 109.8 (tsex, 1JCF 271, 2JCF 38, CF2CF3), 114.9
(tt, 1JCF 270, 2JCF 33, CF2CF2CF3), 117.7 (qt, 1JCF 289, 2JCF 33,
Bromination. Bromine (0.3 g, 2.3 mmol) was added slowly to
a hot (80 ЊC), stirred mixture of 4a (1 g, 2.4 mmol) and ferric
bromide. The solution was heated at reflux temperature until
evolution of hydrogen bromide had ceased and then the reac-
tion mixture was cooled, filtered and dissolved in pentane. The
pentane solution was washed successively with 6  hydrochloric
acid (20 ml), 10% sodium bisulfite (20 ml), and saturated
sodium chloride (20 ml). After drying (MgSO4), the solvent was
cautiously distilled under reduced pressure to afford a mixture
of 4b, 4c and 4d (0.97 g, 81%) in the ratio 1:2:3 by GC–MS
analysis; spectral data were consistent with those obtained
above and no further separation and purification was
attempted.
1
CF2CF3), 122.1 [q, JCF 290, C(CF3)2], 131.1 (s, C-1), 131.4 (s,
C-2); m/z (EIϩ) 423 (Mϩ Ϫ C6F13, 64%), 181 (12), 104 (100), 93
(15), 69 (74), and 1-fluoromethyl-4-[(perfluoro-2-methylpentan-
2-yl)methyl]-benzene 7c (1.5 g, 22%) as a pale yellow liquid; bp
212 ЊC (Siwoloboff); RF 0.2 (Found: C, 37.7; H, 1.6. C14H8F14
requires C, 38.0; H, 1.8%); νmax/cmϪ1 3038 (Ar-H), 2964 (C-H),
1263–1220 (C-F), 732 and 701 (C-H); δH 3.49 (2H, s, CH2), 5.30
Preparation of benzoic acid derivatives 10
General procedure. tert-Butyllithium (1.7  in hexanes) was
added to a solution of 4 in cold (Ϫ78 ЊC) diethyl ether under
dry nitrogen. After stirring for 1 h, solid carbon dioxide was
added and the mixture was allowed to warm to room temper-
ature. The reaction mixture was extracted with 2  NaOH
(2 × 30 ml) and then the aqueous phase was acidified with 2 
HCl. A white solid precipitated which was isolated by filtration.
Recrystallization from hexane gave pure samples of benzoic
acid derivatives 10.
2
(2H, d, JHF 48, CH2F), 7.26 (4H, s, Ar-H); δF Ϫ62.7 [6F, s,
C(CF3)2], Ϫ80.4 (3F, s, CF2CF3), Ϫ106.4 (2F, s, CF2CF2CF3),
2
Ϫ123.4 (2F, s, CF2CF3), Ϫ209.4 (1F, t, JHF 48, CH2F); m/z
(EIϩ) 442 (Mϩ, 1%), 123 (100, Mϩ Ϫ C6F13), 103 (12).
2,6-Bis[(perfluoro-2-methylpentan-2-yl)methyl]pyridine
9a
and 2-fluoromethyl-6-[(perfluoro-2-methylpentan-2-yl)methyl]-
pyridine 9b. Compound 1 (13.2 g, 44 mmol), caesium fluoride
(6.5 g, 42.7 mmol) and 2,6-bis-(bromomethyl)pyridine 8 (3.6 g,
13.5 mmol) in sulfolane (40 ml) gave, after column chrom-
atography on silica gel using light petroleum (bp 40–60 ЊC) as
eluant, 2,6-bis[(perfluoro-2-methylpentan-2-yl)methyl]pyridine
9a (1.9 g, 20%) as a pale yellow liquid; bp 277 ЊC (Siwoloboff);
RF 0.36 (Found: C, 30.6; H, 0.9; N, 2.0. C19H7F26N requires C,
30.7; H, 0.9; N, 1.9%); δH 3.67 (4H, s, CH2), 7.22 (2H, d, 3J 7.6,
H-3), 7.61 (1H, t, 3J 7.9, H-4); δF Ϫ62.6 [6F, s, C(CF3)2], Ϫ80.3
(3F, s, CF2CF3), Ϫ106.0 (2F, s, CF2CF2CF3), Ϫ123.0 (2F, s,
3-[(Perfluoro-2-methylpentan-2-yl)methyl]benzoic acid 10a.
tert-Butyllithium (2.6 ml, 4.5 mmol) and 4c (1.1 g, 2 mmol) in
diethyl ether (30 ml) gave 3-[(perfluoro-2-methylpentan-2-
yl)methyl]benzoic acid 10a (0.62 g, 60%) as white crystals; mp
81–83 ЊC (Found: C, 36.8; H, 1.4. C14H7F13O2 requires C, 37.0;
H, 1.5%); δH 3.84 (2H, s, CH2), 7.50 (1H, t, 3JHH 7.6, H-5), 7.60
3
3
4
(1H, d, JHH 8.0, H-4), 8.00 (1H, dd, JHH 7.9, JHH 1.2, H-6),
8.07 (1H, s, H-2); δF Ϫ62.7 [6F, s, C(CF3)2], Ϫ80.8 (3F, s,
CF2CF3), Ϫ106.2 (2F, s, CF2CF2CF3), Ϫ123.2 (2F, s, CF2CF3);
m/z (EIϩ) 454 (Mϩ, 63%), 437 (27), 201 (11), 181 (11), 151 (15),
135 (100), 109 (41).
2
CF2CF3); δC {H} 34.9 (s, CH2), 61.1 [sept, JCF 24, C(CF3)2],
109.5 (tsex, 1JCF 272, 2JCF 38, CF2CF3), 114.7 (tt, 1JCF 270, 2JCF
1
2
32, CF2CF2CF3), 117.5 (qt, JCF 289, JCF 33, CF2CF3), 121.9
1
[q, JCF 290, C(CF3)2], 124.6 (s, C-3), 136.5 (s, C-4), 151.6 (s,
4-[(Perfluoro-2-methylpentan-2-yl)methyl]benzoic acid 10b.
tert-Butyllithium (2.4 ml, 4.5 mmol) and 4d (1.0 g, 2 mmol) in
diethyl ether (40 ml) gave 4-[(perfluoro-2-methylpentan-2-
yl)methyl]benzoic acid 10b (0.6 g, 64%) as white crystals; mp
135–138 ЊC (Found: C, 37.0; H, 1.5. C14H7F13O2 requires C,
C-2); m/z (EIϩ) 743 (Mϩ, 2%), 574 (11), 424 (24), 255 (13), 235
(18), 181 (16), 119 (10), 105 (12), 69 (100), and 2-fluoromethyl-
6-[(perfluoro-2-methylpentan-2-yl)methyl]pyridine 9b (1.7 g,
33%) as a pale yellow liquid; bp 230 ЊC (Siwoloboff); RF 0.16
(Found: C, 35.2; H, 1.6; N 3.2. C13H7F14N requires C, 35.2; H,
1.6; N, 3.1%); νmax/cmϪ1 2960 (C-H), 1596 (C᎐C), 1581 (C᎐N),
37.0; H, 1.5%); νmax/cmϪ1 3100 (br, OH), 1683 (C᎐O), 1176–
᎐
᎐
᎐
1326 (C-F and C–O); δH 3.86 (2H, s, CH2), 7.56 (2H, AX, JAX
7.9, H-3), 8.03 (2H, AX, JAX 8.4, H-2); δF Ϫ62.6 [6F, s,
C(CF3)2], Ϫ80.8 (3F, s, CF2CF3), Ϫ106.3 (2F, s, CF2CF2CF3),
Ϫ123.2 (2F, s, CF2CF3); m/z (EIϩ) 454 (Mϩ, 8%), 151 (11), 135
(100), 109 (22), 107 (65), 90 (22), 69 (56).
1461 (C᎐C), 1268–1214 (C-F); δ 3.71 (2H, s, CH ), 5.43 (2H, d,
᎐
H
2
2JHF 46, CH2F), 7.25 (1H, dd, 3JHH 7.6, 4JHF 4.0, H-2), 7.40 (1H,
3
3
d, JHH 7.6, H-4), 7.70 (1H, t, JHH 7.6, H-3); δF Ϫ62.8 [6F, s,
C(CF3)2], Ϫ80.6 (3F, s, CF2CF3), Ϫ106.2 (2F, s, CF2CF2CF3),
Ϫ123.2 (2F, s, CF2CF3), Ϫ222.9 (1F, t, 2JHF 46, CH2F); δC {H}
34.9 (s, CH2), 62.4 [sept, JCF 24, C(CF3)2], 84.1 (d, JCF 169,
CH2F), 109.6 (tsex, JCF 272, JCF 38, CF2CF3), 114.7 (tt, JCF
2
1
Preparation of benzoyl chloride derivatives 11
1
2
1
2
1
2
270, JCF 32, CF2CF2CF3), 117.6 (qt, JCF 289, JCF 33,
CF2CF3), 119.3 (d, JCF 5, C-3), 121.9 [q, JCF 290, C(CF3)2],
General procedure. A mixture containing 10 and thionyl
chloride was heated at reflux temperature for 2 h or until the
evolution of hydrogen chloride and sulfur dioxide had ceased.
Distillation of the crude reaction mixture under reduced
pressure gave the benzoyl chloride derivative 11.
3
1
2
124.7 (s, C-5), 137.0 (s, C-4), 151.3 (s, C-6), 156.2 (d, JCF 22,
C-2); m/z (EIϩ) 443 (Mϩ, 24%), 274 (24), 254 (37), 235 (11), 186
(16), 181 (14), 124 (94), 69 (100).
288
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290

View Article Online
3-[(Perfluoro-2-methylpentan-2-yl)methyl]benzoyl
chloride
C-2), 120.7 (s, C-4), 123.1 [q, 1JCF 290, C(CF3)2], 129.6 (s, C-5),
11a. Compound 10a (0.51 g, 1.2 mmol) and thionyl chloride
(30 ml) gave 3-[(perfluoro-2-methylpentan-2-yl)methyl]benzoyl
chloride 11a (0.42 g, 80%) as a colourless liquid; bp 60 ЊC (4
mmHg) (Found: C, 35.4; H, 1.4. C14H6ClF13O requires: C, 35.5;
H, 1.3%); νmax/cmϪ1 1775 (C᎐O), 1242 (br C-F); δ 3.97 (2H, s,
149.2 (s, C-2), 152.9 (s, C-NH2); m/z (EIϩ) 425 (Mϩ, 2%), 106
(100), 69 (11).
4-[(Perfluoro-2-methylpentan-2-yl)methyl]aniline 13b. Com-
pound 4f (5.1 g, 11 mmol), 10% Pt on activated carbon (0.5 g)
and ethanol (50 ml) gave 4-[(perfluoro-2-methylpentan-2-
yl)methyl]aniline 13b (3.9 g, 82%) as a yellow liquid; bp 230 ЊC
(Found: C, 37.0; H, 2.1; N, 3.6. C13H8F13N requires C, 36.7; H,
᎐
H
3
3
CH2), 7.69 (1H, t, JHH 7.9, H-5), 7.80 (1H, d, JHH 7.6, H-4),
3
4
8.16 (1H, dd, JHH 7.9, JHH 1.2, H-6), 8.20 (1H, br s, H-2); δF
Ϫ62.7 [6F, s, C(CF3)2], Ϫ80.5 (3F, s, CF2CF3), Ϫ106.4 (2F, s,
CF2CF2CF3), Ϫ123.4 (2F, s, CF2CF3); m/z (EIϩ) 437 (Mϩ Ϫ Cl,
100%), 181 (15), 153 (21), 118 (11), 109 (35), 90 (21).
1.9; N, 3.3%); νmax/cmϪ1 3370 (N–H), 1626 (C᎐C), 1520 (N–H),
᎐
1241 (br C-F); δH (acetone-d6) 3.56 (2H, s, CH2), 6.63 (2H, AX,
JAX 8.4, H-2), 7.03 (2H, AX, JAX 7.9, H-3); δF (acetone-d6)
Ϫ62.7 [6F, s, C(CF3)2], Ϫ80.9 (3F, s, CF2CF3), Ϫ106.3 (2F, s,
CF2CF2CF3), Ϫ123.2 (2F, s, CF2CF3); δC (acetone-d6) 32.8 (s,
4-[(Perfluoro-2-methylpentan-2-yl)methyl]benzoyl
chloride
11b. Compound 10b (0.54 g, 1.2 mmol) and thionyl chloride
(30 ml) gave 4-[(perfluoro-2-methylpentan-2-yl)methyl]benzoyl
chloride 11b (0.46 g, 82%) as a colourless liquid; bp 70 ЊC (4
mmHg) (Found: C, 35.3; H, 1.3. C14H6ClF13O requires: C, 35.5;
H, 1.3%); δH 3.93 (2H, s, CH2), 8.15 (2H, AX, JAX 8.0, H-3),
7.70 (2H, AX, JAX 8.0, H-2); δF Ϫ62.6 [6F, s, C(CF3)2], Ϫ80.8
(3F, s, CF2CF3), Ϫ106.2 (2F, s, CF2CF2CF3), Ϫ123.2 (2F, s,
CF2CF3); m/z (EIϩ) 437 (Mϩ Ϫ Cl, 76%), 181 (25), 153 (13), 137
(43), 125 (16), 118 (44), 109 (70).
1
2
CH2), 62.0 [m, C(CF3)2], 110.4 (tsex, JCF 272, JCF 38,
1
2
CF2CF3), 114.7 (s, C-2), 115.9 (tt, JCF 270, JCF 25,
1
2
CF2CF2CF3), 118.6 (qt, JCF 289, JCF 33, CF2CF3), 123.1
1
[q, JCF 291, C(CF3)2], 133.1 (s, C-4), 149.2 (s, C-3), 152.7 (s,
C-NH2); m/z (EIϩ) 425 (Mϩ, 6%), 106 (100).
Preparation of azo-dyes 15
General procedure. The aniline derivative 13 was dissolved in
a mixture consisting of hot water (7 ml) and 10% HCl (1.5 ml).
Sodium nitrite (0.16 g) in water (2 ml) was added to the cold
(0 ЊC), stirred solution at a rate that ensured that the temper-
ature of the mixture remained below 5 ЊC and then a solution
of the coupling agent in 10% aq. NaOH (2 ml) was added
slowly. Coupling occurred rapidly and a dark orange solid
precipitated within a few minutes. The mixture was cooled in
ice and the azo-dye 15 was collected by filtration and purified
by column chromatography on silica gel.
Esterification
Cyclohexyl 3-[(perfluoro-2-methylpentan-2-yl)methyl]benz-
oate 12. A mixture consisting of 11a (0.50 g, 1.2 mmol),
cyclohexanol (25 ml) and conc. hydrochloric acid (2 ml) was
heated at reflux temperature for 14 h. Distillation of the reac-
tion mixture gave cyclohexyl 3-[(perfluoro-2-methylpentan-2-
yl)methyl]benzoate 12 (0.58 g, 91%) as a viscous, colourless
liquid; bp 200 ЊC (Found: C, 45.1; H, 3.4. C20H17F13O2 requires
C, 44.8; H, 3.2%); νmax/cmϪ1 2938 (br C-H), 1721 (C᎐O), 1591
᎐
Azo-dye 15a. Compound 13b (1.0 g, 2.3 mmol) and β-
naphthol 14a (0.31 g, 2.2 mmol) gave, after purification by col-
umn chromatography using methanol–water as the eluant, dye
15a (0.7 g, 53%) as a bright orange solid; mp 110–115 ЊC (Mϩ,
580.08200. C26H13F13N2O requires Mϩ, 580.08203); λmax(CH3-
CN)/nm (ε/dm3 molϪ1 cmϪ1) 199 (120359), 250 (16249), sh 420
(7999), sh 500 (7999); νmax/cmϪ1 3412 (O–H), 3062 (C-H), 2968
(C᎐C), 1338–1200 (br C-O and C-F); δ (CD3CN) 1.2–1.9
᎐
H
(10H, m, cyclohexyl CH2), 3.74 (2H, s, CH2RF), 4.98 (1H, m,
CH-O), 7.46 (1H, t, 3JHH 7.9, H-5), 7.58 (1H, d, 3JHH 7.0, H-4),
3
7.97 (1H, d, JHH 6.4, H-6), 8.02 (1H, s, H-2); δF (CD3CN)
Ϫ62.8 [6F, s, C(CF3)2], Ϫ80.8 (3F, s, CF2CF3), Ϫ106.2 (2F, s,
CF2CF2CF3), Ϫ123.2 (2F, s, CF2CF3); δC (CD3CN) 24.2, 26.2
and 32.1 (all s, all cyclohexyl CH2), 32.9 (s, CH2RF), 61.3 [sept,
2JCF 24, C(CF3)2], 74.0 (s, CH–O), 110.6 (tsex, 1JCF 272, 2JCF 37,
(C-H), 1622 (C᎐C), 1517–1454 (br N᎐N), 1330–1145 (N–C and
᎐
᎐
1
2
C-F); δH 3.8 (2H, s, CH2), 6.6–8.6 (10H, m, Ar-H); δF Ϫ62.6
[6F, s, C(CF3)2], Ϫ80.8 (3F, s, CF2CF3), Ϫ106.2 (2F, s,
CF2CF2CF3), Ϫ123.2 (2F, s, CF2CF3); m/z (EIϩ) 444 (20), 425
(25), 385 (11), 265 (23), 169 (11), 124 (100).
CF2CF3), 115.9 (tt, JCF 270, JCF 33, CF2CF2CF3), 118.6 (qt,
2
1
1JCF 289, JCF 34, CF3), 123.1 [q, JCF 290, C(CF3)2], 129.5 (s,
C-5), 130.0 (s, C-4), 132.1 (s, C-6), 132.5 (s, C-3), 133.6 (s, C-2),
137.0 (s, C-1), 166.0 (s, C᎐O); m/z (EIϩ) 456 (Mϩ, 55%), 438
᎐
(70), 217 (33), 135 (32), 118 (49), 109 (31), 99 (20), 82 (100).
Azo-dye 15b. Compound 13a (0.5 g, 1.17 mmol) and 4-
hydroxynaphthalene-1-sulfonic acid sodium salt hydrate 14b
(0.27 g, 1.1 mmol) gave, after column chromatography using
methanol–water as the eluant, dye 15b (0.7 g, 48%) as a bright
orange solid; mp 195–200 ЊC; λmax(CH3CN)/nm (ε/dm3 molϪ1
Preparation of aniline derivatives 13
General procedure. A mixture consisting of the nitrobenzene
derivative 4e,f, 10% Pt on activated carbon and ethanol was
stirred under a positive pressure (3 bar) of hydrogen gas at
room temperature overnight. The solution was cautiously fil-
tered to remove the catalyst and evaporation of ethanol
afforded the desired aniline derivative 13 which did not require
further purification.
cmϪ1) 198 (184812), sh 235 (11331), 350 (2331), 490 (3716); νmax
/
cmϪ1 3470 (br O–H), 3084 (br C-H), 1620 (br C᎐C), 1593–1577
᎐
(br N᎐N), 1270–1158 (N–C and C-F); δ 3.8 (2H, s, CH ), 7.0–
᎐
H
2
8.6 (8H, m, Ar-H); δF Ϫ62.6 [6F, s, C(CF3)2], Ϫ80.7 (3F, s,
CF2CF3), Ϫ106.3 (2F, s, CF2CF2CF3), Ϫ123.0 (2F, s, CF2CF3);
m/z (ES, EIϩ) 660 (Mϩ, 20%), 659 (100), 425 (48), 223 (40).
3-[(Perfluoro-2-methylpentan-2-yl)methyl]aniline 13a. Com-
pound 4e (5.1 g, 11.2 mmol), 10% Pt on activated carbon (0.5 g)
and ethanol (50 ml) gave 3-[(perfluoro-2-methylpentan-2-
yl)methyl]aniline 13a (4.0 g, 85%) as a yellow liquid; bp 238 ЊC
(Found: C, 36.8; H, 2.0; N, 3.3. C13H8F13N requires C, 36.7; H,
Azo-dye 15c. Compound 13a (0.5 g, 1.17 mmol) and 1-n-
butyl-6-hydroxy-5-cyano-4-methyl-2-pyridone 14c (0.27 g, 1.1
mmol) gave, after column chromatography using methanol–
water as the eluant, dye 15c (0.7 g, 51%) as an orange solid;
mp 75–80 ЊC (Mϩ, 642.130000. C24H19F13N4O2 requires Mϩ,
642.130043); λmax(CH3CN)/nm (ε/dm3 molϪ1 cmϪ1) 199
(1369732), sh 263 (55401), 420 (7035); νmax/cmϪ1 3450 (br O–H),
1.9; N, 3.3%); νmax/cmϪ1 3373 (N-H), 1624 (C᎐C), 1497 (N–H),
᎐
1243 (br C-F); δH 3.56 (2H, s, CH2), 6.57 (1H, d, 3JHH 7.2, H-4),
3
6.66 (1H, d, JHH 7.6, H-6), 6.69 (1H, br s, H-2), 7.02 (1H, t,
3JHH 7.9, H-5); δF Ϫ62.7 [6F, s, C(CF3)2], Ϫ80.9 (3F, s, CF2CF3),
Ϫ106.3 (2F, s, CF2CF2CF3), Ϫ123.2 (2F, s, CF2CF3); δC 33.3 (s,
2959 (C-H), 2235 (C᎐N), 1698–1640 (C᎐O and C᎐C), 1525 (br
᎐
᎐
᎐
᎐
N᎐N), 1280–1145 (N–C and C-F); δ Ϫ62.6 [6F, s, C(CF3)2],
᎐
F
2
1
2
CH2), 62.5 [sept, JCF 24, C(CF3)2], 109.1 (tsex, JCF 272, JCF
Ϫ80.8 (3F, s, CF2CF3), Ϫ106.2 (2F, s, CF2CF2CF3), Ϫ123.2 (2F,
37, CF2CF3), 114.9 (s, C-6), 115.2 (tt, JCF 270, JCF 33,
CF2CF2CF3), 118.0 (qt, JCF 285, JCF 34, CF2CF3), 118.4 (s,
s, CF2CF3); m/z (CIϩ) 643 (Mϩ ϩ 1, 4%), 253 (17), 237 (15), 220
1
2
1
2
(9).
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290
289

View Article Online
14 A. E. Bayliff and R. D. Chambers, J. Chem. Soc., Perkin Trans. 1,
1988, 201.
15 G. A. Olah, G. K. S. Prakash and J. Sommer, Superacids, Wiley-
Interscience, New York, 1985.
16 R. D. Chambers, Fluorine in Organic Chemistry, John Wiley and
Sons, New York, 1973.
Acknowledgements
We thank Dr G. C. Nicholson and the 3M Company for fund-
ing (studentship to C. M.) and the Royal Society (University
Research Fellowship to G. S.).
17 R. D. Chambers and M. R. Bryce, in Comprehensive Carbanion
Chemistry, ed. E. Buncell and T. Durst, Elsevier, Amsterdam, 1987,
vol. 5, p. 271.
18 R. D. Chambers and C. R. Sargent, Adv. Heterocycl. Chem., 1981,
28, 1.
19 R. D. Chambers, R. P. Corbally and W. K. R. Musgrave, J. Chem.
Soc., Perkin Trans. 1, 1972, 1281.
20 R. D. Chambers, M. Y. Gribble and E. Marper, J. Chem. Soc.,
Perkin Trans. 1, 1973, 1710.
21 G. A. Olah, K. K. Laali and G. Sandford, Proc. Natl. Acad. Sci.
U.S.A., 1992, 89, 6670.
22 E. T. McBee, R. A. Sanford and P. J. Graham, J. Am. Chem. Soc.,
1950, 72, 1651.
23 G. A. Olah, R. Malhotra and S. C. Narang, Nitration. Methods and
Mechanism, VCH Publishers, New York, 1989.
24 J. Porwisiak and M. Schlosser, Chem. Ber., 1996, 129, 233.
25 A. V. Willi, Helv. Chim. Acta., 1957, 40, 2019.
26 B. S. Furniss, A. J. Hannaford, P. W. G. Smith and A. R. Tatchell,
Vogel’s Textbook of Practical Organic Chemistry, Longman,
Harlow, UK, 1989.
References
1 For Part 43, see R. D. Chambers, S. Nishimura and G. Sandford,
J. Fluorine Chem., 1998, 91, 63.
2 Organofluorine Chemistry. Principles and Commercial Applications,
ed. R. E. Banks, B. E. Smart and J. C. Tatlow, Plenum Press, New
York, 1994.
3 D. Cartwright, in Organofluorine Chemistry. Principles and
Commercial Applications, ed. R. E. Banks, B. E. Smart and J. C.
Tatlow, Plenum Press, New York, 1994, p. 237.
4 N. S. Rao and B. E. Baker, in Organofluorine Chemistry. Principles
and Commercial Applications, ed. R. E. Banks, B. E. Smart and J. C.
Tatlow, Plenum Press, New York, 1994, p. 321.
5 I. T. Horvath and J. Rabai, Science, 1994, 266, 72.
6 B. Cornils, Angew. Chem., Int. Ed. Engl., 1997, 36, 2057.
7 A. Studer, S. Hadida, R. Ferritto, S. Y. Kim, P. Jeger, P. Wipf and
D. P. Curran, Science, 1997, 275, 823.
8 W. R. Dolbier, Top. Curr. Chem., 1997, 192, 97.
9 T. Umemoto, Chem. Rev., 1996, 96, 1757.
10 G. K. S. Prakash and A. K. Yudin, Chem. Rev., 1997, 97, 757.
11 B. Langlois, in Organofluorine Chemistry. Principles and Commercial
Applications, ed. R. E. Banks, B. E. Smart and J. C. Tatlow, Plenum
Press, New York, 1994, p. 221.
27 D. Parker, K. Senanayake, J. Vepsaillainen, S. Williams, A. S.
Batsanov and J. A. K. Howard, J. Chem. Soc., Perkin Trans. 2, 1997,
1445.
28 K. N. Makarov, L. L. Gervits and I. L. Knunyants, J. Fluorine
Chem., 1977, 10, 157.
12 M. A. McClinton and D. A. McClinton, Tetrahedron, 1992, 48,
6555.
13 R. D. Chambers and J. Hutchinson, in Comprehensive Organic
Functional Group Transformations, ed. A. R. Katritzky, O. Meth-
Cohn and C. W. Rees, Pergamon, Oxford, 1995, vol. 6, p. 1.
Paper 8/08700H
290
J. Chem. Soc., Perkin Trans. 1, 1999, 283–290