Perfluoroalkylation of simple inorganic molecules: A one step route to novel perfluoroalkylated compounds

Article abstract of DOI:10.1039/b205288c

Reactions of (CH₃)₃SiR_f (R_f = CF₃, C₂F₅) with NOCl, NO/NO₂, SO₂, CO₂, in the presence of caesium fluoride provide a one step synthetic route to perfluoroalkylated compounds in very good yields.

Full text of DOI:10.1039/b205288c

Perfluoroalkylation of simple inorganic molecules: A one step route to
novel perfluoroalkylated compounds
Rajendra P. Singh and Jean’ne M. Shreeve*
Department of Chemistry, University of Idaho, Moscow, ID 83844-2343, USA.
E-mail: jshreeve@uidaho.edu; Fax: +1 208-885-9146
Received (in Corvallis, OR, USA) 24th May 2002, Accepted 5th July 2002
First published as an Advance Article on the web 19th July 2002
Reactions of (CH3)3SiRf (Rf = CF3, C2F5) with NOCl, NO/
NO2, SO2, CO2, in the presence of caesium fluoride provide
a one step synthetic route to perfluoroalkylated compounds
in very good yields.
h reaction time, the yields of the anticipated nitroso compounds
were < 20%.
Although while not surprising, (perfluoroalkyl)trimethylsi-
lane did not react with nitric oxide, the presence of an equimolar
amount of nitrogen dioxide led to the formation of per-
fluoronitrosoalkane in < 15% yields. It is likely that the reaction
occurred because of the presence of NO+ resulting from the
equilibrium, NO + NO2 " N2O3 ? NO+NO22. The per-
fluoronitrosoalkanes were purified by low temperature trap-to-
trap distillation. Products were characterized by comparison
with the spectroscopic data reported in the literature.19,20
Perfluoroalkanesulfinic acids and their derivatives are useful
compounds in the preparation of wetting agents, impregnants,
or surfactants.25 Earlier perfluoroalkanesulfinic acids were
synthesized either by electrochemical methods26 or by the
reduction of perfluoroalkanesulfonic fluorides with hydrazine
hydrate in refluxing ether.27 While the yield of trifluor-
omethanesulfinic acid in the latter synthesis was not reported,
the overall yield reported for perfluorobutanesulfinic acid was
about 20%. Also, there is a report about the reaction of SO2 with
TMSCF3 in the presence of TBAF but the final oxidized product
is reported in 30% yield and no details of experimental and
characterization data are mentioned.28 We report a very facile,
efficient, and high yield synthesis of the caesium salts of
trifluoro and pentafluoroalkanesulfinic acids. Reactions of
(perfluoroalkyl)trimethylsilanes with SO2 and CsF in equimolar
ratios in monoglyme led to the formation of the caesium salt of
perfluoroalkanesulfinic acids in almost quantitative yields
(Scheme 2).‡ The salts were characterized by comparing the
spectroscopic data with the sodium and potassium salt of the
acids reported in the literature.29 These salts were converted
into the free acids in ~ 60% yields by reacting with anhydrous
HCl gas neat and characterized by comparing with the literature
data.27
The reactions of (perfluoroalkyl)trimethylsilane have been
extensively studied with carbonyl compounds but remain
unexplored with carbon dioxide. We have found that CO2 with
Me3SiRf (Rf = CF3, C2F5) in the presence of an equimolar
amount of CsF in monolyme produced RfCO22Cs+ in quantita-
tive yields.§ The reaction does not proceed in the absence of
solvent. Reaction with equimolar amounts of anhydrous HCl
neat gave trifluoroacetic acid in 90% yield and penta-
fluoropropionic acid in 85% yield (Scheme 2). Catalytic
amounts of CsF gave the products in traces. Even in the
presence of an excess perfluoroalkylating reagent (Me3SiRf),
only the monoaddition product was formed with no evidence for
interaction with the remaining carbonyl moiety. Reaction of
COS with Me3SiCF3 in the presence of CsF under identical
reaction conditions led to the formation of a mixture of
Straightforward and reliable synthetic methods for the in-
corporation of perfluoroalkyl groups are highly desirable.
(Perfluoroalkyl)trimethylsilanes are effective reagents that, in
the presence of fluoride ion, have been used for the introduction
of perfluoroalkyl groups into a variety of substrates, including
aldehydes, hydrocarbons, ketones, esters and sulfur-based
electrophiles.1–9 For nearly twenty years, (perfluoroalkyl-
)trimethylsilanes have been used in the synthesis of a variety of
perfluoroalkylated compounds which have found applications
in the fields of materials science, agrochemistry and pharma-
ceuticals.10–16 Our continuing interest in (perfluoroalkyl-
)trimethylsilane reagents prompted us to demonstrate applica-
tions with inorganic substrates. This methodology has allowed
us to prepare several valuable perfluoalkylated compounds in
good to excellent yields in a manner that is much simpler and
more straightforward than the traditional routes. The details of
the reactions are described as follows.
Perfluoronitrosoalkanes have been studied for their use as
monomers in the synthesis of nitroso rubbers and other novel
polymers.17 In the 1950s, the syntheses of polyfluoroalk-
ylnitroso compounds were first reported18–22 by Haszeldine and
Banus when a mixture of perfluoroalkyl iodide and nitric oxide
were subjected to ultraviolet irradiation in the presence of
mercury. In general, conversions did not exceed 50% and, in
addition, it was difficult to remove traces of unreacted iodide,
the presence of which could result in low molecular weight
polymers due to chain transfer reactions. Other methods
involved the photolysis or pyrolysis of a perfluoroacyl nitrite
which required rather drastic reaction conditions ( > 190 °C).23
In some of the syntheses, the toxic (CF3)2Cd compound has
been employed as the transfer reagent with products being
isolated in low yields.24
We now report a simple and efficient method to prepare
perfluoronitrosoalkanes in very good yield. The reaction of
(perfluoroalkyl)trimethylsilane (Me3SiRf, Rf = CF3, C2F5,)
with nitrosyl chloride in the presence of caesium fluoride led to
the formation of perfluoronitrosoalkanes in > 90% yields.†
Since the reaction did not proceed without solvent, ethylene
glycol dimethyl ether (monoglyme) was used. The reaction was
started at 2196 °C and the mixture was allowed to warm slowly
to 25 °C. The formation of the blue gaseous product (CF3NO or
C2F5NO) was complete within 3 h. Stoichiometric amounts of
caesium fluoride were required due to the simple metathetical
nature of the reactions (Scheme 1). However, with the higher
perfluoroalkyl homologues (Me3SiRf, Rf = C6F13, C7F15,
C8F17) the reaction was found to proceed slowly, and over an 8
Scheme 1
Scheme 2
1818
CHEM. COMMUN., 2002, 1818–1819
This journal is © The Royal Society of Chemistry 2002

CF3COSH and CF3CSOH.30 Carbon disulfide was reported to
react with Me3SiCF3.31
5 S. P. Kotun, J. D. O. Anderson and D. D. DesMarteau, J. Org. Chem.,
1992, 57, 1124.
6 J. Wiedemann, T. Heiner, G. Mloston, G. K. S. Prakash and G. A. Olah,
Angew. Chem., Int. Ed., 1998, 37, 820.
7 A. A. Kolomeitsev, V. N. Movchun, N. V. Kondratenko and Y. L.
Yagupolski, Synthesis, 1990, 1155.
8 R. P. Singh, R. L. Kirchmeier and J. M. Shreeve, J. Org. Chem., 1999,
64, 2579.
The present report describes a powerful and simple method
for the preparation of several fluorinated compounds with some
advantages in comparison with some other routes.
This work was supported by the National Science Foundation
(Grant No. CHE-9720365) and by the Petroleum Research
Fund, administered by ACS.
9 R. P. Singh, G. Cao, R. L. Kirchmeier and J. M. Shreeve, J. Org. Chem.,
1999, 64, 2873.
10 Organofluorine Chemistry: Principles and Commercial Applications,
eds. R. E. Banks, B. E. Smart and J. C. Tatlow, Plenum, New York,
1994.
Notes and references
† Caesium fluoride (0.30 g, 2.0 mmol) and ethylene glycol dimethyl ether
(1 mL) were added in a dry flask (100 mL), cooled to 2196 °C. The flask
was evacuated to remove any air or nitrogen gas. NOCl (2.0 mmol) was
transferred under vacuum followed by the condensation of Me3SiCF3 (2.0
mmol) at 2196 °C. The cold bath was removed. The formation of the blue
gas (CF3NO) commenced shortly after the reaction reached 25 °C. The
reaction mixture was stirred for 3 h. Based on the gas phase IR, all of the
NOCl was consumed. CF3NO was separated from other volatile compounds
by trap-to-trap distillation. It was isolated in 92% yield. Product was
characterized by comparing the spectroscopic data reported in the
literature.19 C2F5NO was prepared in the similar way in 85% isolated
yield.20
11 Biomedical Frontiers of Fluorine Chemistry, eds. I. Ojima, J. R.
McCarthy and J. T. Welch, ACS Symposium Series 639; American
Chemical Society, Washington, DC, 1996.
12 Organic Chemistry in Medicinal Chemistry and Biomedical Applica-
tions, ed. R. Filler, Elsevier, Amsterdam, 1993.
13 J. T. Welch and S. Eswaraksrishnan, Fluorine in Bioorganic Chemistry,
John Wiley and Sons, New York, 1991.
14 R. Filler and K. Kirk, Biological Properties of Fluorinated Compounds
inChemistry of Organic Fluorine Compounds II: A Critical Review, eds.
M. Hudlicky and A. E. Pavlath, ACS Monograph 187; American
Chemical Society, Washington, DC, 1995, pp. 1011.
15 Recent Developments in Fluorine-Containing AgrochemicalsinOrgano-
fluorine Chemistry: Principles and Commercial Applications, eds. R. E.
Banks, B. E. Smart and J. C. Tatlow, Plenum, New York, 1994, pp.
237.
16 R. W. Lang, Fluorinated AgrochemicalsinChemistry of Organic
Fluorine Compounds II; eds. M. Hudlicky and A. E. Pavlath, ACS
Monograph 187; American Chemical Society, Washington, DC, 1995,
pp. 1143.
17 D. A. Barr and R. N. Haszeldine, J. Chem. Soc., 1955, 1881.
18 R. N. Haszeldine, Nature, 1951, 168, 1028.
19 J. Jander and R. N. Haszeldine, J. Chem. Soc., 1954, 912.
20 R. N. Haszeldine, J. Chem. Soc., 1953, 2075.
21 J. Banus, Nature, 1953, 171, 173.
‡ In general, caesium fluoride was added in a flask and 1.5 equiv. of
Me3SiRf was added at 2196 °C followed by monoglyme. The mixture was
evacuated and 1.5 equiv. of sulfur dioxide were added. After warming
slowly to 25 °C the reaction mixture was stirred for 24 h. Removal of
volatile materials at reduced pressure gave the caesium salt of per-
fluoroalkylated sulfinic acids. CF3SO22Cs+: Yield, 95%; IR (nujol mull):
1260, 1219, 1190, 1121, 1026, 945, 801 cm21
285.63 (s); 13C NMR (DMSO-d6): d 125.5 (q, JC–F
C2F5SO22Cs+: Yield, 95%; IR (nujol mull): 1262, 1163, 1132, 1083, 1022,
.
19F NMR (DMSO-d6): d
=
360 Hz);
958, 801, 723 cm21
.
19F NMR (DMSO-d6): d 278.17 (s, 3F), 2131.91 (s,
2F); 13C NMR (DMSO-d6): d 120.3 (triplet of quartets, JC–F = 287.5 Hz,
JC–C–F = 34 Hz).
§ Prepared by the similar procedure as used for SO2 reaction.
22 J. Banus, J. Chem. Soc., 1953, 3775.
23 R. E. Banks, M. G. Barlow, R. N. Haszeldine and M. K. McCreath, J.
Chem. Soc., 1966, 1350.
CF3COO2Cs+: Yield: 95%. IR (nujol mull): 1665, 1456, 1417, 1205, 1228,
984, 828, 801, 720 cm21 19F NMR (DMSO-d6): d 273.35 (s, 3F); 13C
.
NMR (DMSO-d6): d 122.7 (q, JC–F = 293 Hz, CF3COO); 164.3 (q, JC–C–F
= 37.5 Hz, CF3COO). To the salt was added an equimolar amount of
anhydrous HCl and after the flask was agitated for 1 h, CF3COOH was
separated in 90% yield by distillation from caesium chloride and
characterized by comparing the spectroscopic data with authentic samples.
C2F5COO2Cs+: Yield: 95%. IR (nujol mull): 1689, 1455, 1366, 1322, 1195,
24 K. Ludovici, D. Naumann, G. Siegmund, W. Tyrra, H.-G. Varbelow and
H. Wrubel, J. Fluorine Chemistry, 1995, 73, 273.
25 H. W. Roesky, H. Niederpruem and M. Wechsberg, Ger. Offen. 2, 1973,
148, 597.
26 J. C. Folest, J. Y. Nedelec and J. Perichon, Synth. Commun., 1988, 18,
1491.
27 H. W. Roesky, Angew. Chem., Int. Ed., 1971, 10, 810.
28 Nucleophilic Perfluoroalkylation of Organic Compounds Using Per-
fluoroalkyltrialkylsilanesinSynthetic Fluorine, eds. G. A. Olah, R. D.
Chamber and G. K. S. Prakash, John Wiley, New York, 1992, pp.
227.
1113, 1024, 984, 935, 806, 730 cm21
.
19F NMR (DMSO-d6): d 281.30 (s,
3F), 2118.10 (s, 2F); 13C NMR (DMSO-d6): d 114.7 (quartet of troplet, 2F,
JC–F = 262 Hz, CF3CF2, JC–C–F, 37.5 Hz, = CF3CF2); 125.0 (triplet of
quartet, 3F, JC–F = 285 Hz, CF3CF2, JC–C–F, 37.5 Hz, CF3CF2, 163.8 (q,
JC–C–F = 22.5 Hz, CF3CF2COO).
29 H. W. Roesky and J. Holtschneider, J. Fluorine Chemistry, 1976, 7,
77.
1 G. K. S. Prakash and A. K. Yudin, Chem. Rev., 1997, 97, 757.
2 R. P. Singh and J. M. Shreeve, Tetrahedron, 2000, 56, 7613.
3 R. Krishnamurti, D. R. Bellew and G. K. S. Prakash, J. Org. Chem.,
1994, 56, 984.
4 D. W. Nelson, N. J. O’Reilly, J. Speier and P. G. Gassman, J. Org.
Chem., 1994, 59, 8157.
30 W. A. Sheppard and E. L. Muetterties, J. Org. Chem., 1960, 25, 180.
31 Y. L. Yagupolskii, V. N. Movchun, N. V. Kirij, D. Naumann, N.
Magiarosa and W. Tyrra, 16th International Symposium Fluorine
Chemistry, University of Durham, UK, July 16–21, 2000, Abstract No.
A38.
CHEM. COMMUN., 2002, 1818–1819
1819