A convenient access to perfluoroalkyl selenoethers selenyl chlorides

Article abstract of DOI:10.1055/s-2001-16050

The treatment of diselenides with different perfluoroalkyl iodides in the presence of sodium hydroxymethanesulfinate led to perfluoroalkyl selenides in fair to good yields. The reaction between benzyl perfluorooctyl selenide chlorine, or sulfuryl chloride

Full text of DOI:10.1055/s-2001-16050

1260
LETTER
A Convenient Access to Perfluoroalkyl Selenoethers and Selenyl Chlorides
Emmanuel Magnier, Erica Vit, Claude Wakselman*
SIRCOB-CNRS, Bâtiment Lavoisier, Université de Versailles-Saint-Quentin, 45 avenue des Etats-Unis, 78035 Versailles, France
Fax 33 1 39 25 44 52; E-mail: wakselma@chimie.uvsq.fr
Received 22 May 2001
Work within our group has demonstrated that disulfides
Abstract: The treatment of diselenides with different perfluoro-
can be employed as precursors for perfluoroalkyl sulfides
alkyl iodides in the presence of sodium hydroxymethanesulfinate
led to perfluoroalkyl selenides in fair to good yields. The reaction
between benzyl perfluorooctyl selenide and chlorine, or sulfuryl
in the presence of sulfoxylate anion radicals.2,9 Aliphatic,
aromatic and heteroaromatic disulfides are susceptible to
chloride, gave rise to the corresponding selenyl chloride and repre- perfluoroalkylation by perfluoroalkyl halides in the pres-
sents an easy route to perfluoroalkylselenyl chlorides.
ence of sulfur dioxide radical anion. Among a variety of
precursors for sulfur dioxide radical anion, sodium hy-
droxymethanesulfinate, NaO2SCH2OH (Rongalite®),
proved to be one of the simplest and most efficient. It was
thus thought that a similar process should work with the
analogous diselenides (Scheme 1).
Key words: fluorinated alkyl halides, selenium derivatives, elec-
tron transfer, selenyl chloride, cleavage by chlorine
The introduction of the trifluoromethylthio group has be-
come an important field in organic chemistry.1 Both the
high lipophilicity and the electron-withdrawing abilities
of this substituent modify the properties of molecules and
its introduction is of great interest to the pharmaceutical
and fine chemical industries.2 The trifluoromethylseleno
group is considered to show similar effects and it is thus
very important to develop new approaches to perfluorom-
ethyl selenides and their homologues.
Scheme 1
Thus, treatment of diphenyl diselenide 1a with a range of
readily available perfluoroalkyl iodides gives rise to per-
fluoroalkyl selenides 2a-e (Table; entries 1, 2, 3, 4 and
5).10,11 This method is also efficient in the alkyl series as
benzyl- and methyl perfluoroalkyl selenides 2f-g are iso-
lated in excellent yields (entries 6 and 7).
Existing routes to perfluoroalkyl selenides are not numer-
ous and usually employ toxic or expensive reagents.
Moreover, these methods are often specific to trifluorom-
ethyl alkyl- and aryl selenides and are not suited to long
perfluoroalkyl chains. Some of them appear to be limited
to aromatic substituents. Their synthesis was first de-
scribed by Emeléus.3 Methyl- and ethyl trifluoromethyl
selenide were obtained by treatment of the corresponding
alkyl iodide with bis(trifluoromethylselenyl) mercury, the
latter prepared from selenium and mercury. Yagupolskii
has described two methods to obtain various aryl perfluo-
roalkyl selenides. The first involves treating arylselenols
or arylselenolates with perfluoroalkyl iodides (CF3I or
C3F7I) under irradiation.4 The second is the substitution of
different aryl iodides by toxic trifluoromethylseleno- and
pentafluorophenylselenocopper compounds prepared by
reaction between copper and the corresponding perfluoro
diselenides.5 More recently, Langlois has described two
efficient syntheses of aryl- and alkyl trifluoromethyl se-
lenides. The former were prepared by reaction of the sele-
nocyanates with Ruppert's reagent (CF3SiMe3).6 The
second approach involved the addition of either Ruppert's
reagent or the hemiaminal of trifluoroacetaldehyde to dis-
elenides.7 Finally, trifluoromethyl selenides are accessible
to the nucleophilic displacement of chlorine in trifluorom-
ethylselenyl chloride by various carbanions. This method
is efficient but is limited by the difficult preparation of the
latter compound.8a,b
The mechanism of this reaction is thought to involve gen-
eration of the perfluoroalkyl radical by reaction of the per-
fluoroalkyl halide with SO2 radical anion.9 A direct attack
of the perfluoroalkyl radical at the selenium-selenium
bond can give rise to the perfluoroalkyl selenide and to a
selenyl radical, which probably dimerizes (Scheme 2). In
all experiments, Rongalite® was added in portions over
several hours to the reaction. In theory, this allows for the
continuous production of sulfur dioxide radical anion and
should thus facilitate radical formation over a longer time
period. However, a selenide anion can be produced under
these conditions by in situ reduction of the diselenide.12
Thus, it is unclear as to whether the perfluoroalkyl radical
is formed from the halide by direct reaction with the sul-
foxylate radical anion or with the selenide anion.13 Never-
theless, diselenides can be formed again from
Scheme 2
Synlett 2001, No. 8, 1260–1262 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
A Convenient Access to Perfluoroalkyl Selenoethers and Selenyl Chlorides
1261
Table Preparation and NMR characteristics of perfluoroalkyl selenides 2a-g
a) Bruker AC300; solvent CDCl3; references: TMS and CFCl3.
alkylselenide anions and perfluoroalkyl halides, by analo-
gy with the behavior of alkylthiolates.14 Consequently, the
proposed mechanism (Scheme 2) seems reasonable, at
least for aliphatic diselenides.
Previous work in our laboratory described an efficient
synthesis of trifluoromethanesulfonyl chloride by oxida-
tive chlorination of benzyl trifluoromethyl sulfide in
aqueous medium.15 Thus, treatment of benzyl perfluo-
Scheme 3
rooctyl selenide 2g with chlorine under non oxidative con-
ditions (CCl4 as solvent) gives rise to a mixture of benzyl
chloride 4 and perfluorooctylselenyl chloride 3 in quanti-
tative yield.16a Interestingly, the same result is obtained
when compound 2g is treated with sulfuryl chloride in
dichloromethane. Cleavage of the carbon-selenium bond
is easy in the case of a benzyl substituent (Scheme 3).
parative GC and the selenyl chloride 3 was characterized
by NMR analysis (19F, 77Se) and HRMS.16 The crude mix-
ture can be used in further experiments without any puri-
fication (Scheme 3). Direct addition of sodium
diethylmalonate in ether in the previous mixture gives rise
to the corresponding selenoether 5.18
No trace of perfluorooctylselenyl trichloride was detected
by 77Se NMR.17 The crude mixture was purified by pre-
Synlett 2001, No. 8, 1260–1262 ISSN 0936-5214 © Thieme Stuttgart · New York

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E. Magnier et al.
LETTER
(10) Preparation of 2g : Dibenzyl diselenide (3.00 g, 8.82 mmol)
was dissolved in DMF (30 mL) under argon. Perfluorooctyl
iodide C8F17I (4.72 mL, 17.60 mmol), prewashed with a 10%
aqueous solution of Na2S2O5, was added followed by water (1
mL). Lastly sodium hydroxymethanesulfinate (4.07 g, 26.40
mmol) was added in portions over 3 h. The solution was
stirred at room temperature for 20 h. The mixture was
extracted with Et2O and the organic layer washed with
NaHCO3 (5% in H2O) and water, then dried over MgSO4, and
concentrated under reduced pressure. The product was
purified by flash chromatography on silica gel using pentane
as eluent (Rf : 0,70) to afford 8.25 g (80% calculated from
C8F17I) of 2g. See Table for 1H and 19F NMR. All compounds
were also characterized by mass spectra and 13C NMR.
(11) The poor yield obtained in the trifluoromethyl series is
explained by the difficulty to work with gaseous CF3I.
(12) Reich, H.J.; Chow, F.; Shah, S.K. J. Am. Chem. Soc. 1979,
101, 6638.
In summary, we have shown that aryl- and alkyl perfluo-
roalkyl selenides can be obtained in one step from dise-
lenides in a simple way and in good yields. We have also
developed a new access to perfluoroalkylselenyl chlo-
rides.
Acknowledgement
This work was supported by the Centre National de la Recherche
Scientifique. We thank Marie-José Pouet and Chantal Robert-La-
barre for help with 77Se NMR measurements, and Atofina for the
generous gifts of perfluoroalkyl halides.
References and Notes
(1) a) Hansch, C.; Leo, A.; Unger, C.H.; Kim, K.H.; Nikaitani, D.;
Lien, E.J. J. Med. Chem 1973, 16, 1207. b) Hansch, C.; Leo,
A.; Taft, R.W. Chem. Rev 1991, 91, 165. c) Yagupolskii,
L.M.; Yagupolskii, Yu.L. J. Fluorine. Chem. 1995, 72, 225.
d) Clark, J.H.; Wails, D.; Bastock, T.W. Aromatic
Fluorination, CRC Press, Boca Raton, 1996, p. 119.
(2) Clavel, J.-L.; Langlois, B.; Nantermet, R; Tordeux, M.;
Wakselman C.; Eur. Pat. 374,061 to Rhône-Poulenc Agro,
1990; Chem. Abstr. 1991, 114, 5483s.
(3) Emeléus, H.J.; Welcman, N. J. Chem. Soc. 1963, 1268.
(4) Volochtuk, V.G.; Boiko, V.N.; Yagupolskii, L.M. Zhur. Org.
Chim. 1977, 13, 2003.
(5) Kondratenko, N.V.; Kolomeytsev, A.A.; Popov, V.I.;
Yagupolskii, L.M. Synthesis 1985, 667.
(6) Billard, T.; Large, S.; Langlois, B.R. Tetrahedron Lett. 1997,
38, 65.
(7) a) Billard, T.; Langlois, B.R. Tetrahedron Lett. 1996, 37,
6865. b) Blond, G.; Billard, T.; Langlois, B.R. Tetrahedron
Lett. 2001, 42, 2473. c) Ruppert, I. J. Fluorine. Chem. 1985,
29, 98.
(8) a) Dale, J.W.; Emeléus, H.J.; Haszeldine, R.N. J.Chem. Soc.
1958, 2939. b) Treatment of trifluoromethyl iodide and
selenium under pressure at 260-280 °C gives rise to a mixture
of bis(trifluoromethyl) selenide (CF3)2Se and the diselenide
(CF3Se)2. After purification by distillation, the diselenide is
treated with chlorine to afford the desired compound.
(9) a) Wakselman, C.; Tordeux, M.; Clavel, J.-L.; Langlois, B. J.
Chem. Soc. Chem. Commun. 1991, 993. b) Clavel, J.-L.;
Langlois, B.; Nantermet, R.; Tordeux, M.; Wakselman, C. J.
Chem. Soc. Perkin Trans. I 1992, 3371.
(13) Uneyama, K.; Kitagawa, K. Tetrahedron Lett. 1991, 32, 375.
(14) Anselmi, A.; Blazejewski, J-C.; Tordeux, M.; Wakselman, C.
J. Fluorine. Chem. 2000, 105, 41.
(15) Tordeux, M.; Francese, C.; Wakselman, C. J. Fluorine. Chem.
1989, 43, 27.
(16) a) Preparation of 3 with chlorine : Benzyl perfluorooctyl
selenide 2g (3.00 g, 5.10 mmol) was dissolved in CCl4 (25
mL, 0.2 M). Chlorine was bubbled to this solution cooled at
0 °C during 10 min. After 30 min, distillation of the solvent
through a Vigreux column left a mixture of benzyl chloride 4
and of selenyl chloride 3. These compounds were separated by
preparative GC (Shimadzu GC-8A, with SE30 column on
chromosorb WAW 45/60, length 2,5 m) to afford 2.6 g (95%)
of 3. Retention times : 40 min for 3 and 17.5 min for 4. 19
F
NMR (288 MHz, CFCl3): = -81.5 (3F, m), -90.4 (2F, m), -
118.9 (2F, m), -122.1 (2F, m), -122.4 (4F, m), -123.3 (2F, m),
-126.8 (2F, m); 77Se NMR (57 MHz, SeMe2): = 1059;
HRMS m/z calcd for C8F17ClSe 533.8583, found 533.8579.
b) Preparation of 3 with sulfuryl chloride : Benzyl
perfluorooctyl selenide 2g (0.80 g, 1.35 mmol) was dissolved
in CH2Cl2 (7 mL, 0.2 M). Sulfuryl chloride (0.16 mL, 2.03
mmol) was added slowly at 0 °C and the temperature was
raised to room temperature for 1 h. Work-up and yield were
identical to those described above.
(17) a) Gombler, W. Z. Naturforsch. 1981, 36b, 535. b) The 77Se
NMR chemical shift for compound 3 is 1059 ppm which is
consistent with the litterature ( = 953 for CF3SeCl3 versus
1077 for CF3SeCl).
(18) Haas, A.; Praas, H-W. Chem. Ber. 1992, 125, 571.
Article Identifier:
1437-2096,E;2001,0,08,1260,1262,ftx,en;G07101ST.pdf
Synlett 2001, No. 8, 1260–1262 ISSN 0936-5214 © Thieme Stuttgart · New York