Bi(CF3)3/Cu(OCOCH3)2 - A new system for the synthesis of 2-trifluoromethylcycloalkan-1-ones, trifluoromethylanilines and phenyl(trifluoromethyl)sulfane

Article abstract of DOI:10.1016/S0022-1139(00)00339-0

Bi(CF₃)₃ reacts in the presence of equimolar amounts of Cu(OCOCH₃)₂ and 1-morpholinocyclopentene to give 1-morpholino-2-trifluoromethylcyclopentene in 83% yield. This compound as well as intermediately formed 1-morpholino-2-trifluoromethylcyclohexene can easily be converted into the corresponding cycloketones (78 and 41% yield) using the Swarts procedure. In absence of a copper(II) source, no reactions were observed. The reaction of the system Bi(CF₃)₃/Cu(OCOCH₃)₂ with N,N-diethylaniline gave an 1.7: 1 isomer mixture of 2-trifluoromethyl and 4-trifluormethyl-N,N-diethylanilines in 48% yield. With tetrabutylammonium thiophenolate, mixtures of phenyl(trifluoromethyl)sulfane and diphenyldisulfane were obtained. Mechanisms are discussed.

Full text of DOI:10.1016/S0022-1139(00)00339-0

Journal of Fluorine Chemistry 106 (2000) 217±221
Bi(CF3)3/Cu(OCOCH3)2 Ð a new system for the synthesis of
2-tri¯uoromethylcycloalkan-1-ones, tri¯uoromethylanilines
and phenyl(tri¯uoromethyl)sulfane
N.V. Kirija, S.V. Pasenoka, Yu. L. Yagupolskiia,1, W. Tyrrab, D. Naumannb,*
aInstitute of Organic Chemistry, Academy of Sciences of Ukraine, Murmanskaya Str. 5, UA-02094 Kiev, Ukraine
b
È È È È
Institut fur Anorganische Chemie, Universitat zu Koln, Greinstr. 6, D-50939 Koln, Germany
Received 23 June 2000; accepted 14 August 2000
Dedicated to Prof. Dr. Ralf Miethchen on the occasion of his 60th birthday.
Abstract
Bi(CF3)3 reacts in the presence of equimolar amounts of Cu(OCOCH3)2 and 1-morpholinocyclopentene to give 1-morpholino-2-
tri¯uoromethylcyclopentene in 83% yield. This compound as well as intermediately formed 1-morpholino-2-tri¯uoromethylcyclohexene
can easily be converted into the corresponding cycloketones (78 and 41% yield) using the Swarts procedure. In absence of a copper(II)
source, no reactions were observed.
The reaction of the system Bi(CF3)3/Cu(OCOCH3)2 with N,N-diethylaniline gave an 1.7: 1 isomer mixture of 2-tri¯uoromethyl and 4-
tri¯uormethyl-N,N-diethylanilines in 48% yield.
With tetrabutylammonium thiophenolate, mixtures of phenyl(tri¯uoromethyl)sulfane and diphenyldisulfane were obtained. Mechanisms
are discussed. # 2000 Elsevier Science S.A. All rights reserved.
Keywords: Bismuth; Copper(II); Tri¯uoromethyl; Fluorine; Synthesis
1. Introduction
comparative study, we found out that Bi(C6H5)3 and
Bi(CF3)3, gave benzophenone and a,a,a-tri¯uoroacetophe-
none, respectively, in better than 65% yield [12].
In extension of our previous work on reactions of tris(per-
¯uoroorgano)bismuth, we herein report on synthetic appli-
cations of Bi(CF3)3 in Cu(OCOCH3)2 mediated reactions
with different organic substrates.
The use of organobismuth reagents and especially aryl-
bismuth derivatives has been the subject of several reviews
[1±3]. There is a great number of publications gathering on
organobismuth(V) derivatives in different ®elds of organic
synthesis; however, the use of bismuth(III) compounds,
especially alkyl derivatives, is of limited scope to date.
Triphenylbismuth in the presence of Cu(II) ions was used
as an O- and N-phenylating reagent in reactions with
alcohols, phenols [4±7] and amines [8]. Palladium acetate
mediated reactions of Bi(C6H5)3 with acid chlorides in the
presence of triethylamine gave the corresponding phenones
in good yields [9] whereas reactions with acetyl chloride
without any catalyst gave only poor amounts of acetophe-
none [10]. N-phenylation was also observed in reactions of
Bi(C6H5)3 and isocyanide complexes of palladium [11]. In a
2. Results and discussion
2.1. The reaction of Bi(CF3)3 and Cu(OCOCH3)2
Bi(CF3)3 was used as a tri¯uoromethylating reagent in
reactions with AgONO2 to yield Ag[Ag(CF3)4] [13] and in
reactions with TeCl4 to give Te(CF3)2Cl2 as well as in further
metallorganic systems [14].
In CH3CN solution, Bi(CF3)3 and Cu(OCOCH3)2 react
giving Bi(CF3)2(OCOCH3) and Bi(CF3)(OCOCH3)2 as the
only species detectable in the 19F NMR spectra of the
reaction mixtures. After a period of 2 days, no resonances
of ¯uoroorganobismuth or copper(I) compounds were
detected in the 19F NMR spectra but CH3COF, CHF3,
* Corresponding author. Tel.: ‡49-221-4702292;
fax: ‡49-221-4705196.
E-mail addresses: d.naumann@uni-koeln.de, yurii@fluor-ukr.kiev.ua
(D. Naumann).
1 Co-corresponding author.
0022-1139/00/$ ± see front matter # 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 0 0 ) 0 0 3 3 9 - 0

218
N.V. Kirij et al. / Journal of Fluorine Chemistry 106 (2000) 217±221
CF3CH2CN, C2F4 and c-C3F6 were unambiguously identi-
®ed. A broadened singlet at 75.8 ppm might be assigned to
CH3C(O)CF3. Further signals of low intensity were detected
in the region between 58 and 83 ppm which could not be
assigned. CHF3, CO and CO2 absorption bands were
detected in the IR spectrum of the gas phase.
The change in colour from deep turquoise to pale brown
may be taken as a hint that all copper(II) ions had been
converted to lower oxidation state copper species.
The variety of reaction products reveals that copper(II)
species, probably Cu(CF3)(OCOCH3), had ®rst been formed
which decomposed by elimination of CF3 radicals and
di¯uorocarbene.
was present mainly the ®rst product shown in Scheme 1 was
formed; in the absence of the morpholino derivative only
CHF3 was detected. In both reactions, evidence was found
for the formation of traces of Bi(CF3)(OCOCH3)2. No
reactions were observed mixing Bi(CF3)3 and 1-morpholi-
nocycloalkenes. Altogether, these results implicate that
hypervalent copper species (hypervalent in the sense of
Cu(II) or Cu(III)) are the reactive tri¯uoromethylating
reagents in these systems.
Therefore, the mechanistic approaches formulated for the
arylation of alcohols, phenols and amines by triarylbismuth
have to be taken into account.
They are based on results of Barton et al. [8] and Dodonov
and coworkers [4±7]. Barton et al. studied reactions of
Bi(C6H5)3, Cu(OCOCH3)2 and primary amines. They sug-
gested in a primary step the formation of a bismuth(V)
compound, namely Bi(C6H5)3(OCOCH3)2, which reacts in
the presence of ``freshly'' generated copper(I) ions via a
copper(III) intermediate to give N-phenylated amines; this
mechanistic approach was supported by reactions with
hypervalent iodine compounds [22].
BiꢀCF3† ‡ CuꢀOCOCH3†
3
2
! BiꢀCF3†2ꢀOCOCH3† ‡ ‰CuꢀCF3†ꢀOCOCH3†Š
‰CuꢀCF3†ꢀOCOCH3†Š ! ꢁCF3 ‡ CuOCOCH3
‰CuꢀCF3†ꢀOCOCH3†Š !: CF2 ‡ ‰CuFꢀOCOCH3†Š
With the present knowledge on the stability of fluoroalk-
ylcopper(III) species, intermediate formation of trifluoro-
methylcopper(III) compounds can virtually be excluded
[15±19].
The ®nal results of the work of Dodonov et al. [5] with
alcohols were similar for products and yields.
Our results in estimating the oxidation potential of
Bi(CF3)3 (above 3.0 V in CH3CN) [14] and our failed
attempts to oxidize Bi(CF3)3 with elemental halogens,
XeF2 and [XeF][MF6] (M ˆ As, Ta) [23] together with
knowledge on the stability of ¯uoroalkylcopper(III) com-
pounds [15±19] show that these previous mechanistic
approaches are not plausible for the reactions investigated
by us. Therefore, we propose a different reaction sequence
on the basis of radical or possibly radical±ionic decay of
tri¯uoromethylcopper(II) intermediates (Scheme 2).
All reactions and manipulations were carried out in
commercially available glassware; therefore, the in¯uence
of daylight on the radical decay of intermediately formed
[Cu(CF3)(OCOCH3)] and Cu(OCOCH3)2 [24] has also to be
taken into account for the formation of radicals and the
reduction of Cu(II) ions.
2.2. The reaction of Bi(CF3)3/Cu(OCOCH3)2 and 1-
morpholinocycloalkenes
In a previous paper, we described the reactions of
Zn(CF3)Br CH3CN with 1-morpholinocycloalkenes giving
Á2
2-di¯uoromethyl-1-cyanomethyl derivatives [20]. By con-
trast, Wakselman and coworkers [21] obtained tri¯uoro-
methylcycloalkanones after acidic hydrolysis without
isolation of intermediates.
The overall reaction of Bi(CF3)3, Cu(OCOCH3)2 and 1-
morpholinocycloalkenes giving 1-morpholino-2-tri¯uoro-
methylcycloalkenes which are converted into the corre-
sponding cyclic ketones using the Swarts procedures may
be summarized as follows (Scheme 1).
The progress of the reaction was monitored by recording
19F NMR spectra either in presence of the organic substrate
or not. In both cases, the resonance of Bi(CF3)2(OCOCH3)
was identi®ed by the quartet splitting of the 13C-satellites
indicating the magnetic inequivalence of two CF3 groups
bond to the bismuth atom. When the morpholino derivative
This mechanism explains the formation of 1-morpholino-
2-tri¯uoromethylcycloalkenes.
The second reaction step, the acidic hydrolysis, is the ®nal
step of the Swarts reaction to convert enamines into ketones
(Scheme 3).
Scheme 1. Reaction sequence for the formation of 1-trifluoromethylcycloalkan-2-ones (n ˆ 1, 2).

N.V. Kirij et al. / Journal of Fluorine Chemistry 106 (2000) 217±221
219
Scheme 2. Proposed reaction sequence for the trifluoromethylation of 1-morpholinocycloalkenes with the system Bi(CF3)3/Cu(OCOCH3)2.
Changes of the colours of the reaction mixture of
Bi(CF3)3/Cu(OCOCH3)2/N,N-diethylaniline appear to be
noteworthy. The colour changed from bright turquoise via
dark blue or deep violet to become ®nally nearly colourless.
During the reaction period solids of white, red and grey
colour precipitated irrespective of stoichiometry and con-
ditions. Qualitative analysis exhibited the precipitate con-
sisted mainly of copper, bismuth, ¯uoride and acetate.
However, no explanation for this reaction and the phenom-
ena observed can be given.
Scheme 3. The acidic hydrolysis of 1-morpholinocycloalkenes (Swarts
procedure).
2.3. The reaction of Bi(CF3)3/Cu(OCOCH3)2 and N,N-
diethylaniline
2.4. The reaction of Bi(CF3)3/Cu(OCOCH3)2 and [(n-
C4H9)4N][SC6H5]
Bi(CF3)3 reacts with N,N-diethylaniline in the presence of
Cu(OCOCH3)2 to give a mixture of the 2-CF3-, 4-CF3-N,N-
diethylaniline and CHF3 in a ratio of 1.7:1:2.7. The ratio was
determined by integrating the 19F NMR signals of the
mixture in a gas-tight NMR tube. By contrast, the light-
induced reaction of Te(CF3)2 and the same substrate gave a
1:1:1:3 mixture of all three isomers and CHF3 [25].
Several different pathways are known for the synthesis of
C6H5SCF3 [26±28]. The reaction of the system investigated
is a new approach to C6H5SCF3. The room temperature
reaction of Bi(CF3)3/Cu(OCOCH3)2 and [(n-C4H9)4N]
[SC6H5] gave a product mixture of C6H5SCF3 and
The by-products formed were CH3COF, c-C3F6 and
Bi(CF3)(OCOCH3)2 as well as derivatives showing 19F
resonances between 65 and 76 ppm. Also a low-intensity
signal of the starting material, Bi(CF3)3, was detected.
Variation of stoichiometry and reaction conditions did not
lead to higher selectivity. From one reaction, an isomer
mixture of tri¯uoromethylanilines was isolated by GC in
48% yield (2-CF3:4-CF3 ˆ 1:7 : 1).
(C6H5S)2. On the basis of experimental results, two parallel
reactions must be formulated: radical tri¯uoromethylation
of the thiophenolate ion
ꢁ
C6H5S ‡ ꢁCF3 ! ‰C6H5SCF3Š
ꢁ
‰C6H5SCF3Š ‡ CuꢀOCOCH3†
2
! C6H5SCF3 ‡ CuOCOCH3 ‡ CH3COO

220
N.V. Kirij et al. / Journal of Fluorine Chemistry 106 (2000) 217±221
and oxidative coupling of two thiophenolate anions
mediated by copper(II) ions [29].
(0.98 mmol) 1-morpholinocyclopentene were added at
08C. The reaction mixture was stirred for 1 h at 08C and
an additional hour at ambient temperature. The residue was
®ltered off, and all volatile compounds were removed by
vacuum distillation at room temperature. The remaining
product was extracted with low-boiling petroleumbenzene.
After evaporation of the eluent, 1-morpholino-2-tri¯uoro-
methylcyclopentene remained as an analytically pure pale
yellow oil in 83% yield (0.18 g).
2C6H5S ‡ 2CuꢀOCOCH3†
2
! ꢀC6H5S† ‡ 2CuOCOCH3 ‡ 2CH3COO
Variation of reaction parameters did not give evidence for
the selective formation of C6H5SCF3.
2
3. Experimental
Elemental analysis [found (calculated)]: C 54.01 (54.29),
H 6.12 (6.38), N 6.25 (6.33), F 25.54 (25.76)%.
All reactions were carried out in a dry nitrogen atmo-
sphere using Schlenk techniques. The work-up procedures
did not require this technique.
N,N-Diethylaniline was purchased from Aldrich, Cu(O-
COCH3)2ÁH2O from Fluka and used after careful dehydra-
tion in vacuo. The following products were synthesized
according to literature procedures: 1-morpholinocyclopen-
tene and hexene [30], [(n-C4H9)4N][SC6H5] by analogy to
[31], Bi(CF3)3 [13,32]. All solvents were puri®ed according
to literature procedures [33].
NMR data (CDCl3): 19F: 69.2 ppm, s; 1H: 3.55 ppm, m,
4H; 2.74 ppm, m, 4H; 1.82±2.24 ppm, m, broad, 6H.
After hydrolysis with cold aqueous hydrochloric acid
(20%) and extraction with diethylether followed by evapora-
tion of the ether, 2-tri¯uoromethylcyclopentanone was
obtained in 78% yield (bp 74±788C at 25 Torr).
Elemental analysis [found (calculated)]: C 47.25 (47.38),
H 4.80 (4.64)%.
The NMR spectra agreed well with published data [34].
19F NMR spectra were recorded on Bruker spectrometers
WP 200 or AC 200 operating at 188.3 MHz, 1H NMR
spectra on a Gemini 200 spectrometer. Positive shifts denote
resonances occuring down®eld from the external standard
CCl3F (19F) and the internal standard [(CH3)3Si]2O (1H).
3.3. The system Bi(CF3)3/Cu(OCOCH3)2/1-
morpholinocyclohexene
The reaction was carried out by analogy to the method
described above. The complete reaction mixture was hydro-
lyzed with cold aqueous hydrochloric acid (20%). After
extraction with diethyl ether and evaporation of the solvent
2-tri¯uoromethylcyclohexanone was obtained as an oily
liquid in 41% yield with a boiling point of 94±968C
(33 Torr) (cf. literature data 80±828C (18 Torr) [21] and
90±928C (30 Torr) [35]). The NMR data were identical with
those given in [21,35].
3.1. The system Bi(CF3)3/Cu(OCOCH3)2/CH3CN
Bi(CF3)3 (0.14 g (0.33 mmol)) was added to a solution of
0.12 g (0.66 mmol) carefully dried Cu(OCOCH3)2 in 2 ml
CH3CN. The turquoise solution was stirred at ambient
temperature for several days. The course of the reaction
was monitored by recording 19F NMR spectra. After a
reaction time of 5 h, the spectrum was dominated by the
resonance of the starting material Bi(CF3)3 ( 33.7 ppm).
3.4. The system Bi(CF3)3/Cu(OCOCH3)2/N,N-
diethylaniline
Low-intensity
resonances
for
Bi(CF3)2(OCOCH3)
( 36.1 ppm) and Bi(CF3)(OCOCH3)2 ( 41.0 ppm) were
also detected. 19F NMR spectra recorded after 2 days,
A mixture of 0.22 g (0.53 mmol) Bi(CF3)3, 0.10 g
(0.55 mmol) Cu(OCOCH3)2 and 0.04 g (0.27 mmol) N,N-
diethylaniline in 5 ml CH3CN was stirred for 72 h at ambient
temperature. 19F NMR spectra were recorded to determine
the composition of the reaction mixture. Integrating the
signals of CHF3 and 2- as well as 4-tri¯uoromethylaniline
gave a ratio of approximately 1:1. The integrals of the two
tri¯uoromethylaniline isomers exhibited a ratio of 1.7:1
favouring the 2-isomer. The 19F NMR data agreed well with
those given in [25]. Further signals were detected for
CH3COF, Bi(CF3)3, Bi(CF3)(OCOCH3)2, c-C3F6; low-
intensity signals were covering the region between 65
and 76 ppm.
19
exhibited the signals of CH3COF (‡50.0 ppm, q; 3Jꢀ F-
1H† ˆ 7:0 Hz), CHF3 ( 78.9 ppm, d, 2Jꢀ F-1H† ˆ
19
19
79:3 Hz†, CF3CH2CN ( 64.3 ppm, t, 3Jꢀ F-1H ˆ
9:0 Hz†, C2F4 ( 133.0 ppm, s) and c-C3F6 ( 156.5 ppm,
s). One broad signal at 75.8 ppm, probably CH3C(O)CF3
or the corresponding ketal, as well as several low-intensity
signals covering the region between 58 and 83 ppm
could not be assigned. In the course of the reaction, the
colour of the reaction mixture changed from bright turquoise
to pale brown; a red-brown solid precipitated. The gas-phase
IR-spectrum (7 hPa, KBr-plates) showed only the absorption
bands of CHF3, CO2 and CO.
Variations of molar ratios and reaction times did not lead
to an increase in selectivity. During all reactions, marked
changes in colour were observed. In all cases, the originally
bright turquoise colour changed to dark blue or deep violet.
Irrespective of stoichiometry, white, intensive red or metal-
lic grey solids precipitated containing copper, bismuth,
3.2. The system Bi(CF3)3/Cu(OCOCH3)2/1-
morpholinocyclopentene
To a solution of 0.70 g (1.68 mmol) Bi(CF3)3 in 5 ml
CH3CN, 0.30 g (1.65 mmol) Cu(OCOCH3)2 and 0.15 g

N.V. Kirij et al. / Journal of Fluorine Chemistry 106 (2000) 217±221
221
[6] V.A. Dodonov, T.I. Starostina, Yu.L. Kuznetzova, A.V. Gushchin, Izv.
Akad. Nauk, Ser. Khim. (1995) 156
¯uoride and acetate as determined by qualitative analysis.
With extension of the reaction time, the mixtures became
vermilion, then colourless. However, in most cases the
content of tri¯uoromethylanilines did not exceed 1/5 of
all ¯uorine containing compounds (integration of the 19F
NMR spectra). Using a 10-fold entry, separation of tri¯uor-
omethylanilines was successful via GC. 2-Tri¯uoromethyl-
and 4-tri¯uoromethyl-N,N-diethylaminobenzene were iso-
lated in 48% yield (2-CF3:4-CF3 ˆ1.67:1).
[7] V.A. Dodonov, T.I. Starostina, Yu.L. Kuznetzova, A.V. Gushchin,
Russ. Chem. Bull. 44 (1995) 151.
[8] D.H.R. Barton, J.-P. Finet, J. Khamsi, Tetrahedron Lett. 28 (1987)
887.
[9] D.H.R. Barton, N. Ozbalik, M. Ramesh, Tetrahedron 44 (1988) 5661.
[10] F. Challenger, L.R. Ridgway, J. Chem. Soc. 121 (1922) 104.
[11] B. Crociani, M. Nicolini, T. Boschi, J. Organomet. Chem. 33 (1971)
C81.
[12] N.V. Kirij, S.V. Pasenok, Yu.L. Yagupolskii, D. Naumann, W. Tyrra,
J. Fluorine Chem. 69 (1994) 219.
[13] W. Tyrra, D. Naumann, J. Organomet. Chem. 334 (1987) 323.
[14] R. Schlengermann, Dissertation, UniversitaÈt zu KoÈln, 1994.
[15] M.A. Willert-Porada, D.J. Burton, N.C. Baenziger, J. Chem. Soc.,
Chem. Commun. (1989) 1633
3.5. The system Bi(CF3)3/Cu(OCOCH3)2/
tetrabutylammonium thiophenolate
A mixture of 0.66 g (1.59 mmol) Bi(CF3)3, 0.30 g
(1.65 mmol) Cu(OCOCH3)2 and 0.30 g (0.85 mmol) [(n-
C4H9)4N][SC6H5] in 5 ml CH3CN was stirred for 4 h at
ambient temperature. The mixture was extracted with
diethylether and ®nally washed with dilute aqueous NaOH
and water. The organic layer was dried with MgSO4. After
evaporating the solvent and the extracting reagent,
C6H5SCF3 was distilled in vacuo. C6H5SCF3 was identi®ed
[16] D. Naumann, T. Roy, K.-F. Tebbe, W. Crump, Angew. Chem. 105
(1993) 1555.
[17] D. Naumann, T. Roy, K.-F. Tebbe, W. Crump, Angew. Chem. Int. Ed.
Engl. 32 (1993) 1482.
[18] R. Eujen, B. Hoge, D.J. Brauer, J. Organomet. Chem. 519 (1996) 7.
[19] D. Naumann, T. Roy, B. Caeners, D. HuÈtten, K.-F. Tebbe, T. Gilles,
Z. Anorg. Allg. Chem. 626 (2000) 999.
[20] W. Tyrra, D. Naumann, S.V. Pasenok, Yu.L. Yagupolskii, J. Fluorine
Chem. 70 (1995) 181.
[21] M. Tordeux, C. Francese, C. Wakselman, J. Chem. Soc., Perkin
Trans. I (1990) 1951.
1
by 19F ( 43.1 ppm) [27,28] and H NMR spectroscopy as
well as its boiling point ((glass-capillary) 141±1428C) [36].
Signi®cant amounts of (C6H5S)2 were formed as the by-
product.
[22] T.P. Lockhart, J. Am. Chem. Soc. 105 (1983) 1940, and literature
cited therein.
[23] W. Tyrra, D. Naumann, Can. J. Chem. 67 (1989) 1949.
[24] E.M. Glebov, V.F. Plyusnin, V.P. Grivin, S.A. Krupoder, T.I.
Liskovskaya, V.S. Danilovich, J. Photochem. Photobiol. A: Chem.
133 (2000) 177.
Acknowledgements
[25] D. Naumann, S.V. Pasenok, W. Tyrra, Zh. Org. Khim. 29 (1993) 152.
[26] L.M. Yagupolskii, Aromatic and Heterocyclic Compounds with
Fluorine Containing Substituents, Naukova Dumka, Kiev, 1988, p. 98
ff.
We are indebted to the Deutsche Forschungsgemeinschaft
(DFG) and the Ukrainian Ministry of Sciences and Tech-
nology for ®nancial support. N.V. Kirij thanks the DFG and
S.V. Pasenok thanks the Heinrich-Hertz-Stiftung for grants.
[27] T. Billard, B.R. Langlois, Tetrahedron Lett. 37 (1996) 6865.
[28] T. Billard, S. Large, B.R. Langlois, Tetrahedron Lett 38 (1997) 65.
[29] E. Block, Reactions of Organosulfur Compounds, Academic Press,
New York, 1978, p.16 f.
[30] G. Stork, A. Brizzolara, H. Landesman, J. Szmuszkovicz, R. Terrell,
J. Am. Chem. Soc. 85 (1963) 207.
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