A novel catalytic pathway for perfluoroacyl peroxide synthesis

Article abstract of DOI:10.1021/ol016338v

matrix presented A new catalytic method for synthesis of bis(perfluoroacyl) peroxides (BPFAP) was elaborated by using hydrogen peroxide and perfluoroacyl anhydrides. The desired BPFAP were formed quantitatively in situ when perfluoroacyl anhydride was mixed with hydrogen peroxide (ratio ≥ 2:1) in the presence of a catalytic amount of the carboxylate R_fCOO^- M⁺. The essentially irreversible character of this process was shown experimentally and supported on the basis of DFT calculations. The synthesis of new acetyltrifluoroacetyl peroxides is also described.

Full text of DOI:10.1021/ol016338v

ORGANIC
LETTERS
2001
Vol. 3, No. 19
2997-2999
A Novel Catalytic Pathway for
Perfluoroacyl Peroxide Synthesis
,†
Pavel A. Krasutsky,* Igor V. Kolomitsyn,† and Robert M. Carlson‡
Natural Resources Research Institute, Duluth, Minnesota 55811-1442, and Department
of Chemistry, UniVersity of Minnesota Duluth, Duluth, Minnesota 55812
pkrasuts@d.umn.edu
Received June 23, 2001
ABSTRACT
A new catalytic method for synthesis of bis(perfluoroacyl) peroxides (BPFAP) was elaborated by using hydrogen peroxide and perfluoroacyl
anhydrides. The desired BPFAP were formed quantitatively in situ when perfluoroacyl anhydride was mixed with hydrogen peroxide (ratio g
2:1) in the presence of a catalytic amount of the carboxylate R COO- M+. The essentially irreversible character of this process was shown
f
experimentally and supported on the basis of DFT calculations. The synthesis of new acetyltrifluoroacetyl peroxides is also described.
The chemistry of fluoroalkanoyl peroxides is a well-
researched area in organic synthesis, with Hideo Sawada and
co-workers leading the effort.1 Fluoroalkanoyl peroxides
manifest unique properties that are attractive not just for
fundamental but also for applied chemistry. These peroxides
can be used as active radical initiators for the polymerization
of halogenated olefins2 and as reagents for perfluoroalkyla-
tion processes of polymers3 and monomers.1,4 It has been
shown that even polymeric hydrocarbon materials can be
perfluorinated with fluoroalkanoyl peroxides.5 Despite nu-
merous patents6 and publications7,8 devoted to fluoroalkanoyl
peroxide preparation, a convenient protocol for laboratory
or industrial application remained elusive. Generally, these
methods can be summarized (Scheme 1) as the use of
Scheme 1
perfluoroacyl chlorides or anhydrides in the presence of
water. Moreover, even if the reaction is performed under
phase transfer conditions,6f,7 the hydrolysis and loss of
starting reagents, as well as the loss of hydrolyzable bis-
(perfluoroacyl) peroxides (BPFAP),1 occurs in parallel
fashion. The formation of salt byproducts is also undesirable.
These literature observations, as well as our experience
with trifluoroperacetic acid (TFPAA),9 led to a research goal
of developing a nonaqueous, catalytic, high-yield, and waste-
free method for BPFAP synthesis. Understanding the mech-
anism for the reaction of H2O2 with RfCOOCORf was the
key to our success. The study of this seemingly obvious
† Natural Resources Research Institute.
‡ University of Minnesota Duluth.
(1) Sawada, H. Chem. ReV. 1996, 96, 1779. Sawada, H. J. Fluorine Chem.
2000, 105, 219.
(2) Young, D. M.; Thompsom, B. U.S. Patent 2,7000,662, 1955. E. I.
du Pont de Nemours & Co. Brit. 781,532, 1957. Carlson, D. P. ger., Offen.
1,806,426, 1969.
(3) Hayakawa, Y.; Nishida, M.; Kimoto, H.; Fujii, S.; Sawada, H. Polym.
Bull. 1994, 32, 661.
(4) Ogino, K.; Abe, M.; Morikawa, K.; Mitani, M.; Sawada, H.;
Matsumoto, T. J. Jpn. Soc. Colour M. 1992, 65, 205. Sawada, H.; Mitani,
M.; Minoshima, Y.; Nakayama, M. J. Jpn. Res. Institute M. Technol. 1994,
12, 185.
(5) Sawada, H.; Kita, M.; Yoshimizu, J.; Kyokane, T.; Kawase, Y.;
Hayakawa, K.; Yoshino, J. J. Fluorine Chem. 1997, 92, 51.
(6) (a) Young, D. M.; Stoops, W. N. U.S. Patent 2,792,423, 1957. (b)
Bullitt, O. H. U.S. Patent 2,559,630, 1951. (c) Dittman, A. L.; Wringson,
J. M. U.S. Patent 2,775,618, 1956. (d) Young D. M. Brit. 794,830, 1958.
(e) Miller, W. T.; Dittman, A. L.; Reed, S. K. U.S. Patent 2,580,359, 1951.
(f) Sawada, H.; Nakayama, M. JP Patent JP 01249752 A2 19891005, 1989.
(7) Zhao, C.; Zhou, R.; Pan, H.; Jin, X.; Qu, Y.; Wu, C.; Jiang, X. J.
Org. Chem. 1982, 47, 2009.
(8) Sawada, H.; Nakayama, M.; Yoshida, M.; Yoshida, T.; Kamigata,
N. J. Fluorine Chem. 1990, 46, 423.
(9) (a) Krasutsky, P. A.; Kolomitsyn, I. V.; Kiprof, P.; Carlson, R. M.;
Fokin, A. A. J. Org. Chem. 2000, 65, 3926. (b) Krasutsky, P. A.;
Kolomitsyn, I. V.; Kiprof, P.; Carlson, R. M.; Sydorenko, N. A.; Fokin, A.
A. J. Org. Chem. 2001, 66, 1701.
10.1021/ol016338v CCC: $20.00 © 2001 American Chemical Society
Published on Web 08/24/2001

10
reaction was performed with >95% H2O2 and freshly
corresponding perfluorocarboxylic peracid (RfCOOOH). The
rapid ion exchange process in polar perfluorocarboxylic acid
also facilitates the catalytic activity. This result supports
accepting a general scheme for BPFAP formation (Scheme
3).
distilled trifluoroacetic anhydride (TFAAn) with concentra-
tion ratios of [TFAAn]/[H2O2] ) 0-10 at room temperature.
19F NMR analyses of the reaction mixtures at different ratios
shows the stoichiometric formation of TFPAA (δ -74.3),
trifluoroacetic acid (TFAA, δ -77.7), and nonreacted
TFAAn (δ -77.1) when the ratio [TFAAn]/[H2O2] is greater
than 1. When the ratio was greater than 5, only traces of
bis(trifluoroacetyl) peroxide11 (BTFAP, δ -72.8) appeared
in the reaction mixture. Nonetheless, the presence of BTFAP
in the reaction media indicated the feasibility of BTFAP
formation. It was reasonable to infer that acidic or basic
catalysis could facilitate this ionic process. Acidic catalysts
(H2SO4, BF3) did not change the ratio of components.
However, the addition of trace amounts of sodium or
potassium salts of TFAA (less than 0.1% of the concentration
of H2O2), dramatically changed the product distribution. The
peak for TFPAA completely disappeared, and the peak for
BTFAP appeared when the ratio of [TFAAn]/[H2O2] was
greater than or equal to 2. The essentially irreversible
character of this catalytic, consecutive process was character-
ized by Figure 1. Figure 1 also demonstrates quantitative
transfer of active oxygen from H2O2 into TFAAn.
Scheme 3
The stoichiometry of the entire process (Scheme 3) shows
that the ratio of [bis(perfluoroacyl) anhydride]/[H2O2] should
be equal to 2 (if 100% H2O2) in order to receive the highest
concentration of BPFAP. If the ratio of [bis(perfluoroacyl)
anhydride]/[H2O2] is less than or equal to 1 (zone 1), an
equivalent amount of perfluorocarboxylic peracid and per-
fluorocarboxylic acid is formed. If this ratio is greater than
1 and less than 2 (zone 2), the solution would contain
perfluorocarboxylic peracid, BPFAP, and perfluorocarboxylic
acid. When this ratio is greater than 2 (zone 3), the solution
(10) Pizey, S. J. Synthetic Reagents; John Wiley & Sons: New York,
1985; Vol. 6, p 60.
(11) Kopitzky, R.; Willner, H.; Hermann, A.; Oberhammer, H. Inorg.
Chem. 2001, 40, 2693.
(12) General procedure for the preparation of a solution of bis-
(perfluoroacyl) peroxide (BPFAP) in the corresponding perfluorocarboxylic
acid: 95% H2O2 (1.70 g, 47.5 mmol H2O2) was added dropwise into a
well-stirred solution of RfCOOK (0.047 mmol) in freshly distilled bis-
(perfluoroacyl) anhydride (100 mmol) at 0 °C. After addition of the H2O2,
the reaction mixture was stirred for 10 min at 0 °C. A 31% (mol) solution
of BPFAP in perfluorocarboxylic acid was obtained. It is possible to use
less concentrated H2O2. In this case the solution of bis(perfluoroacyl)
peroxide in perfluorocarboxylic acid would be less concentrated to a
corresponding degree. For example 8% (mol) solution of BPFAP in
perfluorocarboxylic acid was obtained when 30% H2O2 (1.77 g, 15.6 mmol
H2O2) was added dropwise into a well-stirred solution of RfCOOK (0.047
mmol) in freshly distilled bis(perfluoroacyl) anhydride (100 mmol) at 0
°C. After addition of the H2O2, the reaction mixture was stirred for 10 min
at 0 °C. The concentration of BPFAP was measured by 19F NMR spectra.
19F chemical shifts are given relative to external CFCl3. BTFAP 19F NMR
(CF3COOH, 282.2 MHz): δ -72.8. Bis(pentafluoropropanonyl) peroxide
19F NMR (C2F5COOH, 282.2 MHz): δ -85.1, -121.3. Bis(heptafluoro-
butanoyl) peroxide 19F NMR (C3F7COOH, 282.2 MHz): δ -82.6, -118.4,
-128.2. Bis(nonafluoropentanoyl) peroxide 19F NMR (C4F9COOH, 282.2
MHz): -83.2, -117.9, -124.8, -127.5.
(13) Gaussian 98, revision A.5; Frisch, M. J.; Trucks, G. W.; Schlegel,
H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Zakrzewski, V. G.;
Montgomery, J., Jr. A.; Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam,
J. M.; Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.;
Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.;
Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman,
J. B.; Cioslowski, J.; Ortiz, J. V.; Stefanov, B. B.; Liu, G.; Liashenko, A.;
Piskorz, P.; Komaromi, I.; Gomperts, R.; Martin, R. L.; Fox, D. J.; Keith,
T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.;
Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.;
Andres, J. L.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian,
Inc.: Pittsburgh, PA, 1998.
Figure 1. Molar concentration of fluorine-containing products vs.
the ratio [TFAAn]/[H2O2] in the presence of CF3COO-.
The same observation was made for other perfluorinated
anhydrides (Rf ) C2F5, C3F7, C4F9).12 To clarify accurately
the energetic feasibility of this process, DFT computations
at the B3LYP/6-31G(d) level, as implemented in a Gaussian
98 program, were employed.13 The results of these calcula-
tions indicated that this process was energetically rather
favorable (Scheme 2).
Scheme 2
The efficiency of basic catalysis for this process is
understandable, because of the higher nucleophilicity of
perfluoropercarboxylate ion (RfCOOO-) compared to the
2998
Org. Lett., Vol. 3, No. 19, 2001

will contain BPFAP, bis(perfluoroacyl) anhydride, and
perfluorocarboxylic acid (see Figure 1). When freshly
distilled bis(perfluoroacyl) anhydride is used, the formation
of BPFAP was not observed.14 Knowledge about this
peculiarity of the reaction between H2O2 and bis(perfluoro-
acyl) anhydrides is very important for planning synthetic
operations. For instance, zone 1 may be explored for
epoxidation,15 Baeyer-Villiger16 reactions, and Criegee9
rearrangement processes. Zone 2 is rather unpredictable,
because two different processes are the possible (radical1-5
reactions may be caused by the presence of BPFAP). Zone
3 should be interesting for studying radical reactions of
BPFAP in the corresponding perfluorocarboxylic acid.
BTFAP manifests high stability in TFAA. Thus, the
concentration of a 28% solution of BTFAP in TFAA
remained essentially unchanged (26.5%) at -10 °C for 6
months. It is known that the stabilities of other BPFAP are
lower,8,17 but they are also sufficiently stable for industrial/
laboratory safe operations when maintained at -10 °C in
the corresponding perfluorinated acid.
can also be prepared9a by adding a solution of TFPAA in
TFAA at 0 °C into a solution of acetic acid in freshly distilled
1
TFAAn (method B, Scheme 4). H and 19F NMR analysis
of the reaction mixture shows the formation of acetyltrif-
luoroacetyl peroxide9a in a quantitative yield. The initial
active oxygen was preserved in both methods A and B.
Identical spectral data were obtained for acetyltrifluoroacetyl
peroxide, when the acyl cation was generated in TFPAA
(Scheme 5).9a This approach should be considered as the third
method for in situ acetyltrifluoroacetyl peroxide generation.
Scheme 5
A solution of acetyltrifluoroacetyl peroxide in TFAA was
stable at 0 °C without noticeable changes in the NMR spectra
or in the concentration of active oxygen. Attempts to use
methods A and B for other carboxylic acids (propanoic,
i-butanoic, pivalic, etc.) did not lead to stable peroxides
because of their rapid decomposition to the corresponding
trifluoroacetates (Scheme 6).
The synthesis of asymmetric alkyloylperfluoroacyl per-
oxides was the next logical step of the research. A literature
search showed the absence of any information on this area.
Our research was directed to the synthesis of acetyltrifluoro-
acetyl peroxide,9a as the first member of this class of
asymmetric perfluoroacyl peroxides. Two possible ways for
this peroxide synthesis were proposed on the basis of our
experience with re-esterification processes (Scheme 4). One
Scheme 6
Scheme 4
This new method for selective, nonradical decomposition
of alkanoyltrifluoroacetyl peroxides and the corresponding
mechanism will receive additional consideration in a fol-
lowing paper. At this point we may note that both methods
A and B (Scheme 6) do not require any basic catalysis. This
can be explained by the enhanced nucleophilicity19 of
carboxylic peracids compared to perfluorocarboxylic per-
acids.
method involves peracetic acid and TFAAn (A), and the other
involves TFPAA and acyltrifluoroacyl anhydride (B).9a The
DFT computational analysis at the B3LYP/6-31G(d) level13
(Scheme 4) shows that these reactions are energetically even
more favorable (∆∆E ) 1.09-1.38 kcal/mol) than described
in Scheme 2. These thermodynamic calculations were quite
promising for the preparation of acetyltrifluoroacetyl per-
oxide. A solution of peracetic acid, which was prepared by
the Swern procedure,18 was added at 0 °C into TFAAn in
TFAA (method A, Scheme 4). Acetyltrifluoroacetyl peroxide
Acknowledgment. Part of this work was supported by
the International Soros Fund (reg no. NCC000). We also
thank the Minnesota Supercomputer Institute and the UMD
Digital Imaging Laboratory (DIL) for allocation of computer
resources.
Supporting Information Available: 19F NMR spectral
characterization of bis(perfluoroacyl) peroxides and tables
containing absolute energies and x,y,z-coordinates of all
computed structures. This material is available free of charge
via the Internet at http://pubs.acs.org.
(14) TFAAn contains traces of sodium trifluoroacetate if stored for a
long time in glass. This concentration may be sufficient to effectively
catalyze BTFAP formation (Scheme 3).
(15) Jensen, A. J.; Luthman, K. Tetrahedron Lett. 1998, 39, 3213.
(16) Renz, M.; Meunier, B. Eur. J. Org. Chem. 1999, 737.
(17) Sawada, H. ReV. Heteroatom Chem. 1993, 50, 205. Sawada, H.;
Nakayama, M.; Kikuchi, O.; Yokoyama, Y. J. Fluorine Chem. 1990, 50,
393.
OL016338V
(18) Organic Peroxides; Swern, D., Ed.; Wiley-Interscience: New York,
1970; Vol. 1, pp 475-516.
(19) (a) Hjelmeland, L. M.; Loew, G. Tetrahedron 1977, 33, 1029. (b)
Fehr, C. Angew. Chem., Int. Ed. 1998, 37, 2407.
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