Approaches to prepare perfluoroalkyl and pentafluorophenyl copper couples for cross-coupling reactions with organohalogen compounds

Article abstract of DOI:10.1039/c5dt02925b

The reactions of iodoperfluoroalkanes C_nF_2n+1I (n = 2, 3, 4) and n-BuLi at low temperatures give NMR spectroscopic evidence for LiC_nF_2n+1 which were converted into LiCu(C_nF_2n+1)₂ derivatives upon treatment with 0.5 mol copper(i) bromide, CuBr. An alternative route to obtain perfluoroorgano copper couples, Cu(R_f)₂Ag (R_f = n-C₃F₇, n-C₄F₉, C₆F₅) was achieved from the reactions of the corresponding perfluoroorgano silver(i) reagents, AgR_f, and elemental copper through redox transmetallations. The composition of the resulting reactive intermediates was investigated by means of ¹⁹F NMR spectroscopy and ESI mass spectrometry. Perfluoro-n-propyl and perfluoro-n-butyl copper-silver reagents prepared by the oxidative transmetallation route exhibited good properties in C-C bond formation reactions with acid chlorides even under moderate conditions. Substitution of bromine directly bound to aromatics for perfluoroalkyl groups was achieved at elevated temperatures, while success in halide substitution reactions using lithium copper couples remained poor.

Full text of DOI:10.1039/c5dt02925b

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PAPER
Approaches to prepare perfluoroalkyl and
pentafluorophenyl copper couples for
cross-coupling reactions with organohalogen
compounds†
Cite this: DOI: 10.1039/c5dt02925b
Mikhail M. Kremlev,a Aleksej I. Mushta,a Wieland Tyrra,b Yurii L. Yagupolskii,*a
Dieter Naumannb and Mathias Schäferc
The reactions of iodoperfluoroalkanes CnF2n+1I (n = 2, 3, 4) and n-BuLi at low temperatures give NMR
spectroscopic evidence for LiCnF2n+1 which were converted into LiCu(CnF2n+1)2 derivatives upon treat-
ment with 0.5 mol copper(I) bromide, CuBr. An alternative route to obtain perfluoroorgano copper
couples, Cu(Rf)2Ag (Rf = n-C3F7, n-C4F9, C6F5) was achieved from the reactions of the corresponding
perfluoroorgano silver(I) reagents, AgRf, and elemental copper through redox transmetallations. The com-
position of the resulting reactive intermediates was investigated by means of 19F NMR spectroscopy and
ESI mass spectrometry. Perfluoro-n-propyl and perfluoro-n-butyl copper–silver reagents prepared by the
oxidative transmetallation route exhibited good properties in C–C bond formation reactions with acid
chlorides even under moderate conditions. Substitution of bromine directly bound to aromatics for
perfluoroalkyl groups was achieved at elevated temperatures, while success in halide substitution reac-
tions using lithium copper couples remained poor.
Received 29th July 2015,
Accepted 13th October 2015
DOI: 10.1039/c5dt02925b
www.rsc.org/dalton
Introduction
Diorgano lithium copper couples, generally written as LiR2Cu,
have been attracting remarkable attention as effective and
selective reagents for substitution of halogens by functional
groups in a variety of different substrates and have even been
used effectively in stereospecific synthesis.1
Scheme 1 Lithium and mixed lithium diorganocuprates.
Ethereal solutions of non-fluorine containing lithium di-
organocuprates are conveniently prepared at 0 °C under an
inert atmosphere via reactions of alkyllithium compounds and
copper iodide or bromide in molar ratios of 2 : 1; mixed
lithium diorganocuprates can be obtained by the reaction
of a monoorganocopper reagent with organolithium species
(Scheme 1).
Scheme 2 Synthesis of perfluoroalkyl copper compounds from perfl-
uoroorgano zinc and cadmium and copper iodide or bromide.
A
mixed fluorine containing lithium diorganocuprate
of methylcopper and pentafluorophenyllithium in diethyl
ether at −70 °C and was used in the reaction with benzoyl
chloride at ambient temperature. After routine work-up pro-
cedures, acetophenone (34%) and 2,3,4,5,6-pentafluorobenzo-
phenone (80%) were obtained.2
Perfluoroorgano copper species CuRf (Rf = CF3, C2F5,
n-C3F7, n-C4F9, C6F5) have been prepared by several
methods.3–6 Mainly perfluoroorgano zinc and cadmium were
used to prepare the corresponding copper reagents via halide
exchange reactions (Scheme 2).3a
Li(CH3)(C6F5)Cu – the only example of such a species to our
knowledge mentioned so far – was formulated in the reaction
aInstitute of Organic Chemistry, National Academy of Sciences of the Ukraine,
Murmanskaya St. 5, UA-02094 Kyiv, Ukraine. E-mail: Yagupolskii@ioch.kiev.ua
bDepartment für Chemie, Institut für Anorganische Chemie, Universität zu Köln,
Greinstr. 6, D-50939 Köln, Germany
cDepartment für Chemie, Institut für Organische Chemie, Universität zu Köln,
Greinstr. 4, D-50939 Köln, Germany
†This paper is dedicated to the memory of our colleague Dr Wieland Tyrra
(08.03.1961–29.11.2014) who sadly passed away during the preparation of this
article.
However, all reactions described so far did neither clearly
point out the formation of bis(perfluoroorgano)cuprates,
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[Cu(Rf)2]− nor of halogenocuprates [Cu(Rf)X]−, although these
derivatives are seen to be the reactive intermediates in nucleo-
philic substitution.3b On the basis of these results, equilibria
may be suggested as outlined below (Scheme 3).
Results and discussion
Synthesis of perfluoroorgano copper reagents
Perfluoroorgano lithium copper couples. Perfluoroorgano
The involvement of highly reactive copper(II) and copper(III) lithium reagents were prepared as intermediates from the reac-
in these reaction sequences especially for the higher perfluoro- tions of pentafluoroiodoethane, C2F5I (1), n-heptafluoroiodo-
alkyl and the pentafluorophenyl derivatives can neither be propane, n-C3F7I (2) or n-nonafluoroiodobutane, C4F9I (3) and
proved nor excluded.6
n-butyllithium in diethyl ether in the temperature range
The involvement of reactive copper species formed by the between −78 °C and −95 °C. Addition of half an equivalent of
system CuX/KF/Me3SiRf in aromatic substitutions is discussed CuBr at −95 °C (for 1 at −75 °C) and a comparison of 19F NMR
in the literature7 without any concrete formulation of the inter- chemical shifts of n-C3F7Li, n-C4F9Li, C3F7Cu, C4F9Cu and
mediately formed species.
copper couples 4–6 (Table 1) gave evidence for the formation
With the synthesis of trifluoromethyl copper compounds of the corresponding perfluoroalkyl lithium copper couples
via an oxidative route not involving any heavier halides a new 4–6 in approximately 80% yields (19F NMR) (Scheme 4). In the
route to CuCF3 reagents from elemental copper and AgCF3 mixtures of THF and DMF, couples 4–6 are stable up to −10 °C
starting from commercially available trimethyl(trifluoro- without any observable decomposition (19F NMR data),
methyl)silane, silver(I) fluoride and copper powder was however, in this temperature range couples 4–6 show only poor
described.8 An excellent synthetic route based on a non-halide reactivity towards halogen-containing aromatic and hetero-
starting material – CF3H – has been developed and is used cyclic compounds.
widely nowadays.9
In this work we present investigations of the preparation of
perfluoroorgano lithium copper and silver couples and a
comparison of their reactivity with perfluoroorganocopper
reagents, CuRf (Rf = n-C3F7, n-C4F9, C6F5), generated via the
Synthesis of perfluoroalkyl copper compounds from RfI and
elemental copper
Perfluoroalkylcopper derivatives were alternatively prepared
from the reactions of the corresponding iodoperfluoroalkanes
corresponding perfluoroorganosilver reagents AgRf and
and copper powder in DMF at 130 °C10 (Scheme 5) for a com-
elemental copper through redox transmetallation.
parative investigation by NMR spectroscopic means.
Perfluoroorgano silver copper couples. On the basis of
results achieved with redox transmetallations between AgCF3
and elemental copper,8a this work has been extended to investi-
gations involving silver/copper couples, Ag(Rf)2Cu, with Rf
being n-C3F7, n-C4F9 and C6F5 (9–11). In contrast with longer
Scheme 3 Equilibria in the synthesis of perfluoroalkyl copper
chain perfluoroalkyls the interaction of AgCF3 and elemental
compounds.
Table 1 Compilation of 19F NMR chemical shifts of perfluoroalkyllithium copper couples, perfluoroalkyl copper compounds, perfluoroalkyl silver
copper couples and perfluoroalkyl silver derivatives
No.
Compound
Solvent
T/°C
δ(α-CF2)
δ(β-CF2)
δ(γ-CF2)
δ(CF3)
4
5
6
7
Li(C2F5)2Cu
Li(n-C3F7)2Cu
Li(n-C4F9)2Cu
Cu(n-C3F7)
Cu[Cu(n-C3F7)2]
Cu(n-C4F9)
Cu[Cu(n-C4F9)2]
Ag(n-C3F7)2Cu
Ag(n-C3F7)2Cu
Ag(n-C4F9)2Cu
Ag(n-C4F9)2Cu
Ag(n-C3F7)
Mixturea
Mixturea
Mixtureb
DMF
DMF
DMF
DMF
EtCN
DMF
EtCN
−70
−70
−70
21
21
21
21
21
21
21
−111.8
−108.5
−108.2
−112.4
−116.5
−111.1
−119.0
−117.1
−118.3
−117.2
−116.1
−106.5
−111.5
−106.8
−112.1
−124.2
−121.2
−82.3
−80.6
−81.2
−79.2
−81.8
−81.0
−81.6
−79.8
−82.6
−80.9
−80.4
−78.6
−78.9
−81.2
−81.3
−78.6
−80.7
−122.5
−125.9
−125.0
−126.5
−123.8
−126.1
−126.9
−123.5
−125.4
−124.8
−123.0
−124.5
−125.4
−125.8
−127.2
−126.5
−115.3
8
−121.7
−122.4
9
10
−123.4
−122.9
DMF
21
DMFc
−30
−30
−30
−30
−70
−70
Ag[Ag(n-C3F7)2]
Ag(n-C4F9)
Ag[Ag(n-C4F9)2]
Li(n-C3F7)
DMFc
DMFc
−119.6
−122.2
DMFc
Mixtured
Mixtured
Li(n-C4F9)
−122.5
a Mixture: Et2O (15 mL)/n-hexane (5 mL)/THF (15 mL)/DMF (15 mL). b Mixture Et2O (10 mL)/n-hexane (3.6 mL)/THF (10 mL)/DMF (10 mL). c 30%
DMF-d7. d Et2O/n-hexane.
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Scheme 8 Equilibrium between the monomeric copper compound
Cu(Rf)·DMF and an ionic form Cu[Cu(Rf)2].
Scheme 4 Perfluoroorgano lithium copper couples.
Scheme 9 Perfluoroalkylhalogeno cuprates.
Scheme 5 Synthesis of perfluoroalkyl copper compounds from RfI and
elemental copper.
Cu(Rf)·DMF and an ionic form Cu[Cu(Rf)2] equilibrate with
each other in compounds 7 and 8 (Scheme 8).4
Chemical shifts of the α-fluorine atom in the 19F NMR
spectra of these compounds are in good agreement with those
reported for the CF2 groups in the 19F NMR spectra of
CuC2F5·DMF (−112.2 ppm) and [Cu(C2F5)2]− (−116.4 ppm),
indicating similar equilibria as outlined earlier.13
Scheme 6 Synthesis of perfluoroalkyl silver compounds from room
temperature reactions of silver(I) fluoride and trimethyl(perfluoro-
organo)silanes in an appropriate solvent such as acetonitrile, propio-
nitrile or DMF.
19F NMR spectra of compounds 5 and 6 significantly differ
from those of compounds 7 and 8 (cf. Table 1) indicating that
in these cases the monomeric species CuRf or presumably
adducts with lithium halides formulated as perfluoroalkylhalo-
geno cuprates, [Cu(Rf)X]− , might be dominating (Scheme 9).
Taking into account the influence of the solvent on chemi-
cal shifts as well as considering literature data,4,13 shifts of
α-CF2 groups of CuCF2Rf can be estimated to be −110 3 ppm
and those of [Cu(CF2Rf)2]− to be −116 3 ppm. As a conse-
quence of the data surveyed in Table 1, compounds 4–6 may
be understood as mainly neutral derivatives, CuCF2Rf, or
adducts with lithium halides, while 7 and 8 equilibrate in a
manner described in ref. 4 and 13. Compounds 9 and 10
exhibit a fluxional character in solution, wherein Ag[Cu-
(CF2Rf)2], Cu[Ag(CF2Rf)2], AgCF2Rf and CuCF2Rf exchange with
each other (Table 1). Data for the C6F5 derivatives are given in
Table 2. Equilibria between CuRf and LiRf for compounds 4–6
can nearly be excluded because in the 19F NMR spectra of
these compounds only signals from Li(Rf)2Cu were observed
[for example, the chemical shift of the α-CF2 group of
Li(C3F7)2Cu is −108.5 ppm].
Scheme 7 Preparation of perfluoroorgano silver copper couples.
copper led to the formation of CuCF3, probably, due to some
specific chemical properties of the trifluoromethyl group.8a
The silver derivatives themselves are conveniently accessible
from room temperature reactions of silver(I) fluoride
and trimethyl(perfluoroorgano)silanes11,12 in an appropriate
solvent such as acetonitrile, propionitrile or DMF (Scheme 6).
Reactions of AgRf and elemental copper within the reaction
times of 30 to 60 minutes gave silver copper couples which
were used for further investigations (Scheme 7).
Compounds 9–11 are stable in solution up to approximately
100 °C. Propionitrile, acetonitrile and DMF have been chosen
as solvents of choice due to the sufficient solubility of AgF in
these media.12
In the case of equilibria between CuRf [the chemical shift
of the α-CF2 group of C3F7Cu is −112.4 ppm] and LiRf [the
chemical shift of the α-CF2 group of LiC3F7 is −124.2 ppm] one
Attempts to use THF as a solvent gave no evidence for the
formation of perfluoroorgano silver copper couples due to the
too low solubility of silver fluoride in this medium.
10
Table 2 19F NMR data of AgC6F5,12 CuC6F5 and Ag(C6F5)2Cu (room
temperature)
19F NMR spectroscopic (4–11) and mass spectrometric
investigations (10–11)
Investigations of solutions of compounds 4–11 by 19F NMR
Compound
δ(F-2,6)
δ(F-4)
δ(F-3,5)
Solvent
AgC6F5
CuC6F5
Cu(C6F5)2Ag
−104.7
−113.4
−111.4
−157.0
−164.0
−158.7
−162.2
−165.3
−162.6
EtCN
CD3CN
EtCN
spectroscopy show that a monomeric copper compound
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Scheme 10 Hydrolysis of Ag(n-C4F9)2Cu.
Scheme 11 Reaction of silver copper couples (9–11) with organic
substrates.
must expect in 19F NMR spectra signals from both reagents
(see Table 1).
Additionally, the involvement of higher aggregates such as
[Cu2(CF2Rf)3]− and related ones seems to be plausible on the
basis of negative ESI mass spectrometric studies of the penta-
fluorophenyl derivative 11. Such behaviour is supported by the
results of A. Sundararaman et al.14 who intensively studied the
structural diversity of CuC6F5 in solution and in the solid
state. 19F NMR data (Table 2) as well as negative ESI mass
spectra especially for the pentafluorophenyl derivatives reveal
that these silver copper couples are best described as
Ag(Rf)2Cu.
Scheme 12 The reaction of couples
dinitrochlorobenzene.
9
and 10 with 2,4-
The perfluoroalkyl reagents are extremely sensitive to moist-
ure and air but cannot be handled for mass spectrometric
analyses under an absolute inert atmosphere. As a conse-
quence under the influence of moisture, ions such as
[Cu(OCOC2F5)2]−, [Ag(OCOC2F5)2]−, [Cu(C3F7)(OCOC2F5)]−, and
[Ag(C3F7)(OCOC2F5)]− were found as most intensive peaks in
the spectra of 9. Analogous peaks were detected in the mass
spectra of 10. Mass spectra of Cu(C6F5)2Ag exhibit ions of sig-
nificant intensities for [Ag(C6F5)2]− as well as [Cu(C6F5)2]− and
Scheme 13 Reactions of copper couple 10 with 4-bromotoluene and
4-bromoanisole.
−
higher aggregates such as [CumAgn(C6F5)
]
(m + n = 3,4;
m+n+1
m = 0–3, n = 0–4) while those of neat AgC6F5 are dominated by
the ion [Ag(C6F5)2]− and those of neat CuC6F5 by [Cu(C6F5)2]−
besides [Cu(OC6F5)(C6F5)]− and [Cu(OC6F5)2]−.15
The reaction of couple 9 with 2,4-dinitrochlorobenzene at
ambient temperature in propionitrile led to product 19 by
substitution of the chlorine atom (Scheme 12).
Hydrolysis of Ag(n-C4F9)2Cu (10)
Our attempts to study the reactions of couples 9 and 10
with 2,4-dinitrochlorobenzene in DMF led only to 2,4,2′,4′-
tetranitrobiphenyl 19. The chlorine atom in the 2,4-dinitro-
benzene is a very reactive leaving moiety and in DMF, probably,
a halogen–copper exchange process takes place; the intermedi-
Compounds 9 and 10 appear to be unaffected by water.
Stirring of 10 and water or 5% aqueous solution of potassium
hydroxide for 8 h gave no evidence of any kind of hydrolysis.
However, our attempt to prepare 10 as an adduct with tri-
phenylphosphine was accompanied by transformation of the
α-CF2 group into an OCO moiety with the final formation of
perfluorobutyric acid after acidic work-up procedures. Thus,
triphenylphosphine might work as a catalyst for such type of
hydrolysis (Scheme 10).
ate formation of
a 2,4-dinitrophenylcopper species may
forward the diaryl 19.
Couples 9 and 10 prepared in propionitrile did not react
with aromatic compounds containing electron-donating
methyl- or methoxy-groups; but in DMF 10 reacted with
4-bromotoluene or 4-bromoanisole to give 4-perfluorobutyl-
substituted aromatic compounds 20 and 21 in 46% and 52%
yields correspondingly (Scheme 13).
Chemical reactivity of perfluoropropyl (9), perfluorobutyl (10)
and perfluorophenyl (11) silver copper couples
Perfluoroorgano silver copper couples 9–11 react with acid
halides at ambient temperature for 2 h to give the corres-
ponding ketones in good yields (64–95%) (Scheme 11). We had
described16 earlier the preparation of such ketones by the reac-
Conclusions
tion of C6F5Ag with acid chlorides that was carried out at In conclusion, an approach toward the preparation of
75–80 °C for 12 h. This is the advantage of compound 11 over perfluoroalkyl and pentafluorophenyl copper reagents has
C6F5Ag.
been elaborated. Interactions of perfluoroorgano silver com-
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pounds and elemental copper gave silver copper couples, was added. After stirring for 20 min copper powder (4 mmol)
Cu(Rf)2Ag, in contrast to trifluoromethyl silver, which interacts was added and stirring was continued for 4 h. 19F NMR
with elemental copper giving the trifluoromethyl-copper spectroscopic data are summarized in Table 1.
species only.8a The silver copper couples 9–11 are stable in
Hydrolysis of the copper couple (10), perfluorobutyric acid (12)
solution up to approximately 100 °C and have good chemical
reactivity and are characterized by ease of handling.
To the copper couple (10) obtained in propionitrile as
described above were added triphenylphosphine (4 mmol) and
water (1 mL). The reaction mixture was stirred at ambient
temperature for 12 h and then extracted with 5% aqueous
KOH. The aqueous phase was extracted with diethyl ether, fil-
tered and acidified with 2% aqueous sulfuric acid. Perfluoro-
butyric acid was extracted with diethyl ether, the organic layer
was dried with MgSO4 and the solvent was evaporated.
Yield: (37%), bp 122–123 °C (in a capillary by the Siwoloboff
method), lit. bp 120 °C (735 mm Hg).20
Experimental section
Fluorine and proton NMR spectra are recorded on Bruker AC
1
200 and AMX 300 instruments (19F: 188.3 and H: 282.4 MHz
respectively) using CCl3F and TMS as external standards and,
unless mentioned, CDCl3 as the lock solvent. n-Iodoperfluoro-
alkanes were purchased from Merck-Schuchardt Co. The solu-
tion of n-BuLi in hexane was obtained from Aldrich; silver(I)
fluoride was from Apollo. All reactions involving organometal-
lic reagents were carried out under an inert atmosphere of pre-
purified nitrogen. Ether and tetrahydrofuran were distilled
from sodium ketyl immediately before use. N,N-Dimethyl-
formamide was freshly distilled under atmospheric pressure
prior to use. Cuprous bromide was prepared using the method
reported in ref. 6; trimethyl(perfluoroalkyl)silanes were syn-
thesized from RfI Me3SiCl and tetrakis(dimethylamino)ethyl-
ene following the Petrov procedure;17 Me3SiC6F5 was prepared
from Me3SiCl and Mg(C6F5)Br in THF in accordance with pub-
lished procedure.18 All other starting materials and applied
reagents were obtained from Fluka and Merck Chemicals.
19F NMR (200 MHz, CDCl3, CFCl3), δ (ppm): −81.3 (t, 4JF–F
=
4
9.1 Hz, 3F, CF3); −120.0 (t, JF–F = 9.1 Hz 2F, α-CF2); −127.5 (s,
2F, β-CF2). 19F NMR data match literature values.21
Reaction of silver copper couples (9–11) with organic
substrates. General procedure
To the silver copper couples (9–11) obtained as described
above, the corresponding organic substrate (2 mmol) was
added. The mixture was stirred at ambient temperature for 2 h
(for acid halides) or 6 h (for 2,4-dinitrochlorobenzene) and
poured into 2% aqueous sulfuric acid with ice. The organic
layer was extracted with diethyl ether. The extract was washed
with water and 5% aqueous Na2CO3 (for compounds 13–18),
dried over MgSO4, evaporated and the respective product was
either purified by distillation or crystallization.
Perfluoroalkyl lithium/copper couples (4–6). General
procedure
Phenyl-n-perfluoropropyl ketone (13)
To a mixture of the corresponding iodoperfluoroalkane (1–3)
(5 mmol) and diethyl ether (15 mL) at −95 °C n-BuLi in hexane
(5 mL of a 1.6 N solution) was added dropwise under stirring.
After stirring at this temperature for 20 min, cuprous bromide
(2 mmol) was added and stirring was continued for another
25 min followed by dropwise addition of tetrahydrofuran
(15 mL) and N,N-dimethylformamide [except for compound
(2)] (15 mL) while the reaction temperature did not exceed
−90 °C. The mixture was stirred for another 20 min; the com-
position was monitored by 19F NMR (fluorobenzene as the
internal standard) spectroscopy at −70 °C (for data see
Table 1).
Colourless liquid, yield: (64%), bp 170–172 °C, lit. bp
173.5 °C.22
1H NMR (300 MHz, CDCl3), δ (ppm): 7.56 (t, JH–H = 8 Hz,
3
3
3
2H, Ar-H-3,5); 7.70 (t, JH–H = 8 Hz, 1H, Ar-H-4) 8.07 (t, JH–H
=
10 Hz, 2H, Ar-H-2,6). 19F NMR, (200 MHz, CDCl3, CFCl3)
4
4
δ (ppm): −80.5 (t, JF–F = 9 Hz, 3F, CF3); −113.9 (m, JF–F
9 Hz, 2F, α-CF2); −126.1 (s, 2F, β-CF2).
=
Phenyl-n-perfluorobutyl ketone (14)
Colourless liquid, yield: (83%), bp 184–186 °C, lit. bp
188.5 °C.21
1H NMR, (300 MHz, CDCl3), δ (ppm): 7.53 (t, JH–H = 8 Hz,
3
Perfluoroalkyl copper (7,8)
3
3
2H, Ar-H-3,5); 7.65 (t, JH–H = 8 Hz, 1H, Ar-H-4); 8.14 (t, JH–H
=
8 Hz, 2H, Ar-H-2,6). 19F NMR, (200 MHz, CDCl3, CFCl3)
Perfluoropropylcopper (7) and perfluorobutylcopper (8) were
obtained from copper powder (12.5 mmol) and the corres-
ponding iodoperfluoroalkane (5 mmol) (2) and (3) in N,N-di-
methylformamide (5 mL) as described in ref. 19, method
A. 19F NMR spectroscopic data are given in Table 1.
4
4
δ (ppm): −81.4 (t, JF–F = 9 Hz, 3F, CF3); −113.3 (t, JF–F
=
10.9 Hz, 2F, α-CF2); −125.6 (m, 2F, β-CF2); −122.2 (m, 2F,
γ-CF2). 2,4-Dinitrophenylhydrazone, mp 133–135 °C (ethanol),
lit. mp 133–136 °C.23
Perfluoroorgano silver copper couples (9–11). General
2,3,4,5,6-Pentafluorobenzophenone (15)
procedure
Colourless crystals, yield: (94%), mp 32–33 °C (diethyl ether :
To a well-stirred mixture of silver fluoride (2 mmol) and pro- pentane 1 : 1), lit. mp 33–34 °C.22 1H NMR, (300 MHz, CDCl3),
3
3
pionitrile or DMF (5 mL) at room temperature the corres- δ (ppm): 7.51 (t, JH–H = 8 Hz, 2H, Ar-H-3,5); 7.67 (t, JH–H
=
ponding perfluoroalkyl or pentafluorophenyl silane (2 mmol) 8 Hz, 1H, Ar-H-4); 7.83 (t, 3JH–H = 8 Hz, 2H, Ar-H-2,6). 19F NMR,
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(200 MHz, CDCl3, CFCl3) δ (ppm): −140.2 (m, 2F, F-2,6); 4-Perfluorobutylanisole (21)
−150.8 (m, 1F, F-4); −160.2 (m, 2F, F-3,5).
Colourless liquid, yield: (52%), bp 202–204 °C (in a capillary by
1
the Siwoloboff method). H NMR, (300 MHz, CDCl3) δ (ppm):
3
4-Nitrophenyl-n-perfluoropropylketone (16)
3.85 (s, 3H, O-CH3), 7.40 (d, JH–H = 8 Hz, 2H, Ar-H-3,5); 7.51
3
(d, JHH = 8 Hz, 2H, Ar-H-2,6). 19F NMR, (200 MHz, CDCl3,
Colourless crystals, yield: (70%), mp 86–88 °C (pentane). 1H
NMR, (300 MHz, CDCl3), δ (ppm): 8.23 (d, 3JH–H = 6 Hz, 2H, Ar-
4
CFCl3) δ (ppm): −81.2 (t, JFF = 11 Hz, 3F, CF3); −109.4 (t,
4JF–F = 11 Hz, 2F, α-CF2,); −121.9 (m, 2F, β-CF2); −124.9 (m, 2F,
γ-CF2). 1H and 19F NMR data are identical to those given in ref.
27 and 28.
3
H-3,5); 8.38 (d, JH–H = 6 Hz, 2H, Ar-H-2,6). 19F NMR,
4
(200 MHz, CDCl3, CFCl3) δ (ppm): −80.3 (t, JF–F = 5.5 Hz, 3F,
4
CF3); −114.1 (q, JF–F = 5.5 Hz, 2F, α-CF2); −125.6 (s, 2F, β-CF2).
1H and 19F NMR data are identical to those given in ref. 24.
Acknowledgements
4-Nitrophenyl-n-perfluoropbutylketone (17)
Colourless crystals, yield: (81%), mp 92–94 °C (ether : pentane,
Generous financial support of this work by the DFG (grant
UKR 113) is gratefully acknowledged.
3
1 : 1). 1H NMR, (300 MHz, CDCl3), δ (ppm): 8.23 (d, JH–H
=
3
8 Hz, 2H, Ar-H-3,5); 8.38 (d, JH–H = 8 Hz, 2H, Ar-H-2,6). 19F
4
NMR, (200 MHz, CDCl3, CFCl3) δ (ppm): −81.2 (t, JF–F
=
4
11 Hz, 3F, CF3); −113.8 (t, JF–F = 11 Hz, 2F, α-CF2); −122.3 (m,
2F, β-CF2); −125.6 (m, 2F, γ-CF2). 1H and 19F NMR data are
identical to those given in ref. 24.
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3
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