Me3SiCF3/AgF/Cu - A new reagents combination for selective trifluoromethylation of various organic halides by trifluoromethylcopper, CuCF3

Article abstract of DOI:10.1016/j.jfluchem.2011.07.025

An alternative copper halide-free route to obtain highly reactive trifluoromethylcopper species has been developed via the reaction of silver fluoride and trimethyl(trifluoromethyl)silane followed by a redox transmetallation with elemental copper. The composition of the reactive intermediate was investigated by means of UV/Vis/NIR, ESR, ¹⁹F NMR spectroscopy and ESI mass spectrometry. "Trifluoromethylcopper" prepared by the oxidative transmetallation route exhibits excellent reactivity and selectivity in substitutions of iodine or bromine bond to aromatic or heterocyclic compounds for trifluoromethyl groups without any additional catalyst.

Full text of DOI:10.1016/j.jfluchem.2011.07.025

Journal of Fluorine Chemistry 133 (2012) 67–71
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Me3SiCF3/AgF/Cu—A new reagents combination for selective trifluoromethylation
§
of various organic halides by trifluoromethylcopper, CuCF3
a
b,
a
a,**
*
, Aleksej I. Mushta , Wieland Tyrra , Yurii L. Yagupolskii ,
Mikhail M. Kremlev
Dieter Naumann b, Angela Moller c
¨
a Institute of Organic Chemistry, National Academy of Sciences of the Ukraine, Murmanskaya St. 5, UA-02094 Kyiv, Ukraine
b Department fu¨r Chemie, Institut fu¨r Anorganische Chemie, Universita¨t zu Ko¨ln, Greinstr. 6, D-50939 Ko¨ln, Germany
c Department of Chemistry, University of Houston, Houston, TX 77204-5003, USA
A R T I C L E I N F O
A B S T R A C T
Article history:
An alternative copper halide-free route to obtain highly reactive trifluoromethylcopper species has been
developed via the reaction of silver fluoride and trimethyl(trifluoromethyl)silane followed by a redox
transmetallation with elemental copper. The composition of the reactive intermediate was investigated
by means of UV/Vis/NIR, ESR, 19F NMR spectroscopy and ESI mass spectrometry. ‘‘Trifluoromethylcop-
per’’ prepared by the oxidative transmetallation route exhibits excellent reactivity and selectivity in
substitutions of iodine or bromine bond to aromatic or heterocyclic compounds for trifluoromethyl
groups without any additional catalyst.
Received 24 June 2011
Received in revised form 24 July 2011
Accepted 27 July 2011
Available online 5 August 2011
Keywords:
Copper
ß 2011 Elsevier B.V. All rights reserved.
Silver
Trifluoromethylation, C–C coupling
1. Introduction
have been proved to act as excellent reagents for the introduction
of perfluoroalkyl groups into organic molecules. Further innovative
It is well-known that pharmaceutical and agricultural chemi-
cals containing trifluoromethyl groups often exhibit unique
biological activities [1]. Therefore, the introduction of trifluor-
approaches target the trifluoromethylation of organic halides
under mild conditions by using trialkyl(trifluoromethyl) silanes
and copper(I) iodide in the presence of a suitable fluoride anion
source (e.g. CsF, KF, [NMe4]F) [7] even allowing multiple extensive
trifluoromethyl group transfer [8]. The very first methods used
expensive or toxic reagents such as CF3I and Hg(CF3)2 or have been
carried out in autoclaves. The latter appear to be more convenient
and environmentally more friendly using Zn(CF3)Br – a reagent
easily prepared from CF3Br [9], a gas formerly used in fire
extinguishers – and Me3SiCF3 [10] in the meantime the widely
used compound, as recently demonstrated in reactions with a
copper alkoxide–carbene complex [11]. Surveys on metal-mediat-
ed trifluoromethylation reactions in general [12] and on trifluor-
ometylations of aryl and heteroaryl halides with copper reagents
were recently presented [13]. While preparing this manuscript, we
became aware of a closely related work dealing with silver-
supported copper catalyzed trifluoromethylation of iodoarenes
with CuCF3 generated from AgCF3 and copper iodide [14].
omethyl groups into organic molecules
– designed for the
development of model systems – has recently emerged as one
of the most attractive research areas in synthesis and reactivity
studies.
‘‘Trifluoromethylcopper’’, although the real reactive species and
the reaction mechanisms are not yet fully understood, can be
generated by various methods. For example, Kobayashi et al.
directly prepared it by the reaction of trifluoroiodomethane with
‘‘activated’’ copper in DMF [2] or HMPA [3]. Yagupolskii et al. [4]
generated it using Hg(CF3)2 as a trifluoromethyl source by
transmetallation to copper. Trifluoromethylcopper has also been
prepared through in situ metathesis of (trifluoromethyl)cadmium
or zinc reagents with copper(I) salts [5]. In a previous publication,
we demonstrated that Zn(CF3)Br and derivatives are suitable
reagents to prepare both CuCF3 and CuC2F5 species [6]. The latter
The oxidative properties of trifluoromethyl silver [15] encour-
aged us to investigate its reactions with copper starting from
commercially available trimethyl (trifluoromethyl) silane, silver(I)
fluoride and copper powder. A comparative and more general route
to perfluoroorganocopper reagents, CuRf (Rf = n-C3F7, n-C4F9, C6F5),
generated via the corresponding perfluoroorganosilver reagents,
§
Silver compounds in synthetic chemistry. Part 6.
* Corresponding author. Tel.: +49 221 4703276; fax: +49 221 4703276.
** Co-corresponding author.
E-mail address: tyrra@uni-koeln.de (W. Tyrra).
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.07.025

68
M.M. Kremlev et al. / Journal of Fluorine Chemistry 133 (2012) 67–71
AgRf, and elemental copper through redox transmetallations will
be presented in a forthcoming publication.
The great attention and importance of catalytic trifluoromethy-
lation of organic substrates with copper reagents is best expressed
by the fact that numerous publications [6,14,16] were released
within the last one and a half year.
2 AgCF3 + Cu
2 CuII(CF3)2
CuII(CF3)2 + 2 Ag
"(CF3)2CuIICuII(CF3)2"
CuI[CuIII(CF3)4]
"(CF3)2CuIICuII(CF3)2"
2. Results and discussion
Scheme 1.
Trifluoromethylsilver is conveniently accessible from room
temperature reactions of silver(I) fluoride and trimethyl(tri-
fluoromethyl)silane in an appropriate solvent, such as acetoni-
trile, propionitrile or DMF [15] (Eq. (1)); the properties of AgCF3
as an effective oxidative trifluormethylating reagent has been
demonstrated in several examples [15]. However, effective
trifluoromethylation of organic substrates by AgCF3 is limited
to reactions with acyl chlorides [17] and dithiuram disulfides; for
the latter reactions, different reaction mechanisms may be
considered [18].
by the fact that the ESR signals are very weak and broad.
Furthermore, the ESR resonance positions are not typical for
monomeric CuII species. These observations guide us to formulate a
mechanistic approach as outlined in Scheme 1. A final, very rapid
rearrangement would lead to the non-magnetic mixed-valent
species CuI[CuIII(CF3)4] (d10/d8).
In ESI mass spectra of the ‘‘Cu(III) precipitate’’ prepared in
propionitrile and (for measurements purposes) diluted with
acetonitrile, the following ions were detected (m/z): negative
mode: 339.07 [Cu(CF3)4]ꢀ (100%); 658.97 [Cu(EtCN)CH2CNCu
AgF þ ðCH3Þ3SiCF3 ! AgCF3 þ ðCH3Þ3SiF
(1)
After 2 h, mixtures of AgCF3 and elemental copper yielded
reactive ‘‘trifluoromethylcopper’’ species which were used for
further transformations (Eq. (2)).
(CF3)4CH2CNCu(EtCN)]ꢀ (40%); 719.00 K[Cu(CF3)4]2 (16%) (It has
ꢀ
to be noted that potassium and sodium ions are often incorporated
in such ions for lack of inertness in performing such experiments.);
positive mode: 145.07 [Cu(MeCN)2]+ (24%); 159.00 [Cu(EtCN)-
MeCN–H]+ (92%); 161.05 [Cu(EtCN)MeCN]+ (36%); 173.08
[Cu(EtCN)2]+ (88%); 338.87 [Cu3(MeCN)(EtCN)2–5H]+ (100%);
340.87 [Cu3(MeCN)(EtCN)2–3H]+ (44%); 441.79 [Cu4(MeC-
N)2(EtCN)2–6H]+ (48%); 539.20 [Cu5(MeCN)4EtCN]+ (4%).
‘‘Trifluoromethylcopper’’ 1 prepared in propionitrile reacts with
1-chloro-2,4-dinitrobenzene, 4-iodonitrobenzene, 4-nitrobenzy-
liodide, ethyl-4-bromobenzoate and 2,6-di(bromomethyl)pyridine
to give the corresponding trifluormethylated products 2–6 in good
yields (Eq. (4)).
AgCF3 þ Cu ! CuCF3 þ Ag
(2)
We suggest, in analogy to equilibria of AgRf and Ag[Ag(Rf)2]
[15,19], similar species of general composition ‘‘Ag(CF3)2Cu’’ as
reactive intermediates, with Ag+ acting as the halide interceptor
and ‘‘Cu’’ as the reactive center. 19F NMR spectroscopic investiga-
tions prove the most reactive derivative in the reaction mixtures
being the trifluoromethylcopper species 1.
Time dependent 19F NMR spectra reveal, the signals of AgCF3
(ꢀ23.9 ppm), the argentate [Ag(CF3)2]ꢀ (ꢀ26.4 ppm) and the less
reactive [AgIII(CF3)4]ꢀ (ꢀ33.0 ppm) (minor intensity) were domi-
nant after addition of Me3SiCF3 to a well stirred solution of AgF in
EtCN. These signals decreased more and more in intensity after
addition of copper powder to the reaction mixture in favor of the
broad signals of CuCF3 (ꢀ28 ppm), [Cu(CF3)2]ꢀ (ꢀ32 ppm), and
[CuIII(CF3)4]ꢀ (ꢀ35 ppm) [5,20].
NO2
NO2
Cl
NO2
NO2
F3C
NO2
2
For better understanding, trifluoromethylcopper was prepared
from copper(I) bromide, trimethyl(trifluoromethyl)silane and
cesium fluoride in propionitrile with the aim to compare the
intermediately formed trifluoromethylcopper obtained via both
routes (Eq. (3)).
59%
54%
I
NO2
F3C
3
NO2
IH2C
(4)
Me3SiCF3 þ CsF þ CuBr ꢀ! CuCF3 þ Me3SiF þ CsBr
(3)
EtCN
F3CCH2
NO2
CuCF3
1
EtCN
However, 19F NMR spectra of copper species generated by both
methods were identical.
4
COOC2H5
5
60%
Br
COOC2H5
CH2Br
F3C
Storage of trifluoromethylcopper obtained from trifluoro-
methylsilver and copper powder in propionitrile or DMF at
ambient temperature for 12 h led to the formation of a precipitate
with the anion [CuIII(CF3)4]ꢀ which was insoluble in most organic
solvents without any definite knowledge of the cation (Ag+ is
involved anyhow). The formation of this anion is not yet
understood. Time-dependent UV/Vis/NIR measurements of
CuII(CF3)2 in DMF show the asymmetric absorbance band around
650–700 nm characteristic for d–d transitions (Cu2+). We note that
within 12 h the concentration of CuII (monitored via the relative
absorbance maxima) is reduced by a factor of 2. Overall all spectra
become slightly red-shifted and loose the distinct shoulder at
72%
N
BrH2C
N
F3C
CF3
53%
6
It should be pointed out that reactions leading to compounds 4
and 6 occur at sp3 hybridized carbon atoms, while all the other
occur at carbon atoms of the aromatic ring systems.
Furthermore, trifluoromethylcopper 1 directly prepared in
DMF exhibited enhanced reactivity in comparison with similar
derivatives prepared in propionitrile. For example, trifluoro-
methylcopper in propionitrile did not allow any bromine
substitution in 2-bromopyridine by a trifluoromethyl group.
In contrast, treatment of trifluoromethylcopper prepared in
DMF reacts with 2-bromopyridine and even 2-bromopyrimidine
higher energies. Slower reaction times indicating
a further
mechanistic step follow and a plateau is reached after 30 h.
However, the speculation that the intermediate CuII(CF3)2 (d9)
undergoes dimerization to ‘‘(CF3)2CuIICuII(CF3)2’’ is only supported

M.M. Kremlev et al. / Journal of Fluorine Chemistry 133 (2012) 67–71
69
Table 1
We investigated the interactions of trifluoromethylcopper 1 in
DMF with unactivated iodo-containing aromatics, namely, iodo-
Reaction temperatures and times (19F NMR control) of ‘‘trifluoromethylcopper’’ (1,
DMF) with selected organic substrates until complete consumption of ‘‘CuCF3’’.
benzene and iodopentafluoro-benzene.
a,a,a-trifluorotoluene 10
Product numbers
Starting compound
Temperature (8C)
Time (h)
was obtained in 83% yield upon treatment of trifluoromethylcopper
with iodobenzene. A mixture of perfluorotoluene 11, pentafluor-
obenzene 12 and perfluorobiphenyl 13 in a 48:32:20 ratio was
isolated from the reaction of trifluoromethylcopper with iodopenta-
fluorobenzene in DMF. The latter reaction demonstrated that
trifluoromethylcopper can also react with organic compounds
containing positively charged iodine. Probably due to the ion-radical
character of trifluoromethylcopper in DMF, as well as the fact that
also copper species in the oxidation states II and even III [6] are likely
to be involved, may account for the reduced selectivity here.
Reaction temperatures and times are summarized in Table 1.
7
2-Bromopyridine
90
20
75
20
50
5
12
4
8
2-Bromopyrimidine
2,6-Dibromopyridine
Iodobenzene
9
10
6
11–13
Iodopentafluorobenzene
3
under formation of 2-trifluoromethylpyridine 7 and 2-trifluoro-
methylpyrimidine 8 in 79% and 75% yield, respectively. Under
similar conditions, CuCF3 (1, DMF) reacted with 2,6-dibromo-
pyridine in an 1:1 molar ratio to give a mixture of di- and mono-
trifluoromethyl substituted compounds whereas upon treat-
ment in a 2:1 molar ratio, 2,6-bis(trifluoromethyl)pyridine 9
was isolated in 92% yield.
It is noteworthy that in the contrast to reactions of trifluor-
omethylcopper in EtCN (1, EtCN), reactions of trifluoromethyl-
copper in DMF (1, DMF) with organic substrates decrease
selectivity resulting in considerable amounts of pentafluoroethyl-
and heptafluoropropyl-derivatives.
N
Br
N
79%
CF3
7
N
N
Br
N
CF3
8
N
75%
For example, treatment of trifluoromethylcopper (1, DMF)
with 3-bromopyridine at 90 8C for 5 h gave
Br
N
Br
(6)
CuCF3
1
a mixture of
DMF
F3C
N
3-(trifluoromethyl)pyridine, 3-(pentafluoroethyl)pyridine and
3-(heptafluoropropyl)pyridine in a 59:37:4 ratio (19F NMR).
The reaction of trifluoromethylcopper in DMF (1, DMF) with
5-bromopyrimidine under similar conditions led to formation
of a mixture of trifluoromethyl-, pentafluoroethyl- and per-
fluoropropyl-derivatives in a ratio 56:41:3, respectively. (Eq. (5))
CF3
92%
9
CF3
C6H5I
10
84%
C6F5I
C6F5CF3
11
C F H
C F C F
+
+
6
5
6
5
6
5
12
13
Br
F3C
C3F7
+
C2F5
DMF
N
N
+
N
N
CuCF3
1
+
o
90 C, 5 h
37
4
59
(5)
Br
F3C
C2F5
+
C3F7
DMF
N
N
N
N
+
CuCF3
1
+
N
N
90o C, 5 h
N
N
3
56
41
Formation of pentafluoroethylcopper during the reaction of
bromine containing organic compounds with trifluoromethyl-
copper (1, DMF) may be explained by the catalytic influence of
copper(I) bromide continuously formed during the reactions. The
ability of Ag+ ions as halides interceptors appeared to be reduced
in these cases. A targeted experiment with addition of copper(I)
bromide to trifluoromethylcopper (1, DMF) led only to the
formation of bromotrifluoromethane. However, heating of
trifluoromethylcopper (1, DMF) to 80 8C after adding a small
quantity (about 10%) of copper(I) bromide and stirring for 3.5 h
allowed its quantitative conversion into pentafluoroethylcopper.
The reaction of trifluoromethylcopper (1, DMF) with an
aliphatic 1-iodododecane proceeded more or less unselective with
conversion of the CF3 group into a C2F5 moiety or dehydrohalo-
genation finally giving a mixture of CF3ꢀ, C2F5ꢀ, CH2Fꢀ and
fluorocontaining aliphates and olefins, beside minor quantities of
CF3H, C2F5H, and n-C3F7H.
3. Conclusion
‘‘Trifluoromethyl copper’’ prepared by a copper halide-free
route via redox transmetallation from trifluoromethyl silver and
elemental copper exhibits excellent reactivity and selectivity in the
substitution of iodine and bromine atoms bonded to aromatic or
heterocyclic compounds even at sp3 hybridized carbon atoms
without any necessity of an additional catalyst. All observations
indicate an interplay of copper compounds in oxidation states I, II
and III as reactive intermediates with copper and silver halides
being finally the halide interceptors. Further, intensive research is
necessary to come up to a comprehensive understanding of these
reactions.

70
M.M. Kremlev et al. / Journal of Fluorine Chemistry 133 (2012) 67–71
4. Experimental
4.1. General
4.2.1.4. 4-Trifluoromethylbenzoic acid ethyl ester (5). Colourless
liquid. Yield 0.63 g (72%), b.p. 90–92 8C (13.33 mbar). lit. b.p. 78–
80 8C (5.0 Torr) [21]. 19F NMR,
d
(ppm): ꢀ63.6 (s, CF3); 1H NMR,
d
3
(ppm): 1.40 (t, 3H, CH3, JH,H = 7.2 Hz), 4.38 (q, 2H, CH2,
3
Schlenk techniques were used throughout all manipulations.
Purifications were carried out in ambient atmosphere. NMR
spectra of unprecedented, isolated compounds were recorded on a
Bruker Avance II 300 (1H, 300.1 MHz; 19F, 282.4 MHz; 13C,
75.4 MHz) spectrometer in CDCl3 solutions unless quoted.
External standards were used in all cases (1H, 13C: Me4Si; 19F:
3JH,H = 7.2 Hz), 7.58 (d, 2H, H-3,5, JH,H = 9.0 Hz), 7.90 (d, 2H, H-
3
2,6, JH,H = 9.0 Hz).
4.2.1.5. Bis-2,6-(2,2,2-trifluoroethyl)pyridine (6). Colourless liquid.
Yield 0.51 g (53%), b.p. 65–67 8C (1.6 ꢁ 10ꢀ2 mbar). 19F NMR,
d
d
1
3
(ppm): ꢀ64.8 (t, 2CF3, JF,C = 278 Hz, JF,H = 11 Hz); 1H NMR,
CCl3F). Chemical shifts (
d
) are given in ppm; couplings (J) in Hz.
(ppm): 3.63 (q, 4H, 3JF,H = 11 Hz); 7.33 (d, 2H, H-3,5); 7.72 (t, 1H, H-
Visible melting points were determined using a Stuart melting
point apparatus SMP10. All compounds are characterized by
melting or boiling points, elemental analyses and NMR spectro-
scopic data. For known compounds, only melting or boiling points
as well as 1H and 19F NMR data are listed, while values of
elemental analyses are not given here. Copper(I) bromide was
prepared using the method reported in [6]. AgF was purchased
from Apollo, Me3SiCF3 from ABCR. All organic reagents were
obtained from Aldrich or Acros and used without any further
purification after NMR spectroscopic measurements to validate
the quality. UV/Vis/NIR spectra were recorded on a CARY05E
(Varian) spectrophotometer in absorbance mode using quartz
glass sample holders. ESR measurements were carried out on an x-
Band Biospin Spectrometer (Bruker).
4). 13C NMR, (ppm): 125.4 (q, 2C (CF3), 1JF,C 278 = Hz), 42.7 (q, 2C
d
(CH2), 2JF,C = 29 Hz), 150.9 (q, 2C, C-2,6, 3JF,C = 3 Hz), 123.6 (q, 2C, C-
4
3,5, JF,C ꢂ 1 Hz), 137.4 (s, C-4). MS (20 eV, m/e): 243 (100%, M+);
223 (32%, M+–HF); 203 (20%, M+–2HF); 174 (12%, M+–CF3).
4.2.2. Method B
To a well stirred mixture of AgF (1.27 g, 10 mmol) in 10 ml of
DMF, Me3SiCF3 (1.7 g, 12 mmol) was added at room temperature.
The mixture was stirred for 20 min and copper powder (1.0 g,
15 mmol) was added. After stirring for 4 h, the formation of CuCF3
was complete. The corresponding halogen containing compound
(9 mmol) (in the case of 2,6-dibromopyridine, 4.5 mmol) was
added and the reaction mixture was stirred under conditions
surveyed in Table 1. The reaction was terminated unless signals of
CuCF3 were no longer detected in the 19F NMR spectra. The
mixture was filtered from the solid precipitate and poured into
50 ml of water. The organic layer was extracted with diethyl ether
and dried over MgSO4. Ether was evaporated and the remainder
was distilled under reduced pressure or crystallized.
4.2. General procedure for the preparation of ‘‘trifluoromethylcopper’’
and its reactions
4.2.1. Method A
To a well stirred mixture of AgF (0.51 g, 4 mmol) in 5 ml of
propionitrile Me3SiCF3 (0.57 g, 4 mmol) was added at room
temperature. The mixture was stirred for 20 min and copper
powder (0.51 g, 8 mmol) was added. After stirring for 4 h, the
formation of ‘‘CuCF3’’ was complete. The corresponding halogen
containing aromatic derivative (4 mmol) was added and the
reaction mixture was stirred for up to 6 h at ambient temperature
and for additional 12 h at 75–80 8C. The reaction was terminated
after signals of CuCF3 were no longer detected in the 19F NMR
spectra. The mixture was filtered from precipitates and 15 ml of
diethyl ether were added. The mixture was washed with water and
dried over MgSO4. The solvent was evaporated and the remainder
was crystallized or distilled from the organic phase under reduced
pressure.
4.2.2.1. 2-(Trifluoromethyl)pyridine (7). Colourless liquid. Yield
1.15 g (79%), b.p. 138–139 8C, lit. b.p. 138–140 8C [22]. 19F NMR,
(ppm) (CDCl3): ꢀ68.2 (s, CF3, 1JF,C = 274 Hz, 2JF,C = 34 Hz); 1H NMR,
d
d
(ppm): 7.68 (d, 1H, H-3); 7.89 (t, 1H, H-4); 7.51 (t, 1H, H-5); 8.74 (d,
1H, H-6). 13C NMR,
d(ppm): 121.5 (q, CF3); 148.3 (s, C-2);120.2 (q, C-
3, 3JF,C = 3 Hz); 137.4 (s, C-4); 126.4 (s, C-5); 150.0 (s, C-6).
4.2.2.2. 2-Trifluoromethylpyrimidine (8). Colourless liquid. Yield
1.0 g (75%), b.p. 42 8C (1.1 ꢁ 10ꢀ1 mbar), lit. b.p. 60 8C (10 mm Hg)
1
[23]. 19F NMR,
d
(ppm) (CDCl3): ꢀ70.6 (s, CF3, JF,C = 275 Hz,
3
2JF,C = 37 Hz); 1H NMR,
7.55 (t, 1H, H-5). 13C NMR,
d
(ppm): 8.95 (d, 2H, H-4,6, JH,H = 5 Hz);
(ppm): 119.4 (q, CF3); 156.7 (s, C-2);
d
123.1 (s, C-5); 158.0 (s, C-4,6).
4.2.1.1. 2,4-Dinitro(trifluoromethyl)benzene (2). Colourless crys-
4.2.2.3. 2,6-Bis(trifluoromethyl)pyridine (9). Colourless crystals.
tals. Yield 0.56 g (59%), m.p. 46–48 8C (pentane), lit. m.p. 48 8C
Yield 0.99 g (92%), m.p. 56–57 8C (hexane), lit. m.p. 55–56 8C
1
1
[4]. 19F NMR,
d
(ppm): ꢀ60.3 (s, CF3, JF,C = 275 Hz,); 1H NMR,
d
C
[24]. 19F NMR,
d
(ppm) (CDCl3): ꢀ68.1 (s, 2CF3, JF,C = 275 Hz,
(ppm): 8.13 (m, 1H, H-6), 8.61 (m, 1H, H-5), 8.76 (m, 1H, H-3). 13
2JF,C = 36 Hz); 1H NMR,
8.13 (t, 1H, 3JH,H = 7.5 Hz, H-4). 13C NMR,
148.8 (q, 2C, C-2,6); 123.1 (2C, C-3,5); 139.3 (1C, C-4).
d
(ppm): 7.92 (d, 2H, 3JH,H = 7.5 Hz, H-3,5);
NMR,
d
(ppm): 121.0 (q, CF3, 1JF,C = 275), 128.8 (q, C-1, 2JF,C = 35 Hz),
d
(ppm): 121.9 (q, 2CF3);
148.7 (s, C-2), 120.6 (s, C-3), 150.1 (s, C-4), 127.0 (s, C-5), 129.9 (q,
3
C-6, JF,C = 5 Hz).
4.2.2.4.
a, a, a-Trifluoromethylbenzene (10). Colourless liquid.
4.2.1.2. 4-Nitro(trifluoromethyl)benzene (3). Colourless crystals.
Yield 0.41 g (54%), m.p. 40–41 8C (pentane), lit. m.p. 40–41 8C
Yield 1.8 g (84%), b.p. 101–102 8C, lit. b.p. 101–103 8C [25]. 19F
1
2
NMR,
d
(ppm) (CDCl3): ꢀ62.8 (s, CF3, JF,C = 272 Hz, JF,C = 32 Hz);
[4]. 19F NMR,
d
(ppm): ꢀ63.2 (q, CF3, JF,C = 273 Hz, JF,C = 33 Hz,
4JF,H = 0.8 Hz, 5JF,H = 0.8 Hz); 1H NMR,
(ppm): 7.86 (m, 2H, H-2,6),
8.38 (m, 2H, H-2,6). 13C NMR,
1H NMR,
d(ppm): 7.67 (s, 2H, H-2,6); 7.52 (s, 2H, H-3,5); 7.57 (s, 1H,
1
2
d
H-4). 13C NMR,
d
(ppm): 124.1 (q, CF3); 130.7 (s, C-1); 125.2 (q, C-
1
3
d
(ppm): 123.0 (q, CF3, JF,C = 273,
2,6, JF,C = 4 Hz); 128.7 (s, C-3,5); 131.7 (s, C-4).
2JF,C = 33 Hz), 136.2 (q, C-1, JF,C = 33 Hz), 126.8 (q, C-2,6,
3JF,C = 4 Hz), 124.1 (s, C-3,5) 150.0 (s, C-4).
2
4.2.2.5. Mixture of perfluorotoluene (11) and pentafluorobenzene
(12). Colourless liquid. Yield 1.6 g, b.p. of the mixture 96–100 8C.
4.2.1.3. 4-Nitro-(2,2,2-trifluoroethyl)benzene (4). Colourless crys-
tals. Yield 0.49 g (60%), m.p. 63–65 8C (pentane), lit. m.p. 65 8C [4].
Perfluorotoluene (11). 19F NMR,
d
(ppm) (CDCl3): ꢀ56.1 (m, 3F,
CF3), ꢀ139.5 (m, 2F, F-2,6), ꢀ153.6 (m, 2F, F-3,5), ꢀ146.8 (m, 1F, F-4).
19F NMR,
d
(ppm): ꢀ65.3 (t, CF3, 3JF,H = 10.7 Hz); 1H NMR,
d
(ppm):
Pentafluorobenzene (12). 19F NMR,
d
(ppm) (CDCl3): ꢀ138.6 (m,
3.50 (q, 2H, CH2, 3JH,F = 10.7 Hz), 7.50 (d, 2H, H-3,5, 3JH,H = 8.7 Hz),
2F. F-2,6), ꢀ159.5 (m, 2F, F-3,5), ꢀ162.0 (m, 1F, F-4). 1H NMR,
d
3
8.20 (d, 2H, H-2,6, JH,H = 8.7 Hz).
(ppm): 6.9 (m, 1H, H-1).

M.M. Kremlev et al. / Journal of Fluorine Chemistry 133 (2012) 67–71
71
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4.2.2.6. Decafluorobiphenyl
(13). Colourless
crystals.
Yield
0.41 g, m.p. 68–70 8C (hexane), lit. m.p. 69 8C [26]. All analytic
data are in full agreement with earlier published material.
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4.3. Trifluoromethylcopper prepared from Me3SiCF3, cesium fluoride
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A
well stirred mixture of trimethyltrifluoromethylsilane
(0.29 g, 2 mmol), CuBr (0.14 g, 1 mmol), 15-crown-5 (0.88 g,
4 mmol) and propionitrile (10 ml) was cooled to ꢀ60 8C and then
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Acknowledgement
H. Morimoto, T. Tsubogo, N.D. Litvinas, J.F. Hartwig, Angew. Chem. Int. Ed. 50
(2011) 3793–3798;
We are indebted to the DFG (grant 436 UKR 113) for financial
support of our work. We thank Dr. Mathias Scha¨fer (Institute of
Organic Chemistry, University of Cologne) for recording the ESI
mass spectra.
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