8180
N. Shefer et al. / Tetrahedron Letters 48 (2007) 8178–8181
the process. Unreacted fluorine should be captured by a
O
[O]
[O]
[O]
simple trap containing a base such as soda lime located at
the outlet of the glass reactor. If elementary precautions
are taken, work with fluorine is simple and we have never
experienced difficulties.
ArSO3H
ArSH
ArS-SAr
ArS-SAr
-H2O
O
B
A
[O] = HOF CH3CN
General procedure for producing HOFÆCH3CN: A mixture
of 10–20% F2 in nitrogen was used throughout this work.
The gas mixture was prepared in a secondary container
prior to the reaction13 and passed at a rate of about
400 mL per minute through a cold (ꢀ15 °C) mixture of
100 mL CH3CN and 10 mL H2O in a regular glass reactor.
The development of the oxidizing power was monitored by
reacting aliquots with an acidic aqueous solution of KI.
The liberated iodine was then titrated with thiosulfate. The
typical concentrations of the oxidizing reagent were
around 0.4–0.6 mol/L.
Scheme 4. The mechanism for the oxidation of thiols or disulfides with
HOFÆCH3CN.
for studies of the ultimate degradation fate of these
acids.29 The heavy oxygen atoms are not interchange-
able with the common 16O isotope found in air or regu-
lar water as evident from mass spectra taken after the
acids had been in prolonged contact with air and water.
The HRMS of 4a (CI) (m/z): calcd from C7H8O3S,
179.039975 (MH)+, found: 179.040067 and for 4c calcd
from C7H8O2S, 161.040816 (MH)+, found: 161.040981
clearly demonstrate this point.
7. Rozen, S.; Bareket, Y. J. Org. Chem. 1997, 62, 1457–1462.
8. Rozen, S.; Bareket, Y. J. Chem. Soc., Chem. Commun.
1994, 1959.
9. Harel, T.; Amir, E.; Rozen, S. Org. Lett. 2006, 8, 1213–
1216.
10. Amir, E.; Rozen, S. Angew. Chem., Int. Ed. 2005, 44,
7374–7378.
11. (a) Rozen, S.; Carmeli, M. J. Am. Chem. Soc. 2003, 125,
8118–8119; (b) Carmeli, M.; Rozen, S. J. Org. Chem. 2006,
71, 4585–4589.
12. Golan, E.; Rozen, S. J. Org. Chem. 2003, 68, 9170–9172.
13. Dayan, S.; Kol, M.; Rozen, S. Synthesis 1999, 1427–1430.
14. (a) Rozen, S.; Dayan, S. Angew. Chem., Int. Ed. 1999, 38,
3471–3473; (b) Rozen, S.; Carmeli, M. J. Org. Chem. 2005,
70, 2131–2134.
The mechanism for this oxidation reaction, portrayed in
Scheme 4, involves the formation of the respective disul-
fides (A), which are then converted into thiosulfonates
(B), both of which were observed when only 2.5 mol
equiv of HOFÆCH3CN were used. It should be
mentioned, however, that other pathways, especially
for aliphatic thiols have also been proposed.24
In conclusion, the efficiency of this method, its simplic-
ity, short reaction times, high yield and the purity of
the products are excellent features. Considering the
commercial availability of premixed fluorine/nitrogen
mixtures and the technical ease of the reaction (no spe-
cial equipment is needed),6 this method may become a
method of choice for many cases where the alternatives
are not good enough.
15. (a) Rozen, S. Eur. J. Org. Chem. 2005, 2433–2447; (b)
Rozen, S. Acc. Chem. Res. 1996, 29, 243–248.
16. General procedure for sulfonic acid preparation: The
requisite mercaptan (0.01 mol) was dissolved in methylene
dichloride (20 ml) and cooled to 0 °C. HOFÆCH3CN
(0.07 mol) was then added slowly to the stirred mercaptan
solution. After a few seconds the solvent was removed
under reduced pressure. Because the compounds are
hygroscopic the products were kept in an evacuated
1
desiccator in the presence of P2O5 for an hour before H
NMR spectra were recorded at 200 and 400 MHz and 13
C
Acknowledgement
NMR at 50 and 100 MHz. The IR spectra were recorded
in KBr on an FTIR spectrophotometer. The MS were
measured under CI or EI conditions. The spectral and
physical properties of known products were compared
with those reported in the literature. In every case excellent
agreement was obtained.
This work was supported by the Israel Science
Foundation.
17. (a) Smith, K.; Hou, D. J. Org. Chem. 1996, 61, 1530–1532;
(b) Freeman, F.; Angeletakis, C. N. Org. Magn. Reson.
1983, 21, 86–93.
18. Loew, O. G. J. Org. Chem. 1976, 41, 2061–2064.
19. (a) Ishii, Y.; Matsunaka, K.; Sakaguchi, S. J. Am. Chem.
Soc. 2000, 122, 7390–7391; (b) Ferguson, R. R.; Crabtree,
R. H. J. Org. Chem. 1991, 56, 5503–5510.
20. Stone, G. C. H. J. Am. Chem. Soc. 1936, 58, 488–489.
21. Wallace, T. J.; Schriesheim, A. Tetrahedron 1965, 21,
2271–2280.
22. Kol, M.; Rozen, S. J. Org. Chem. 1993, 58, 1593–1595.
23. Zoller, U. In The Chemistry of Sulphinic Acids, Esters
and their Derivatives. Patai, S., Ed.; 1990; pp 185–
215.
24. Gu, D.; Harpp, D. N. Tetrahedron Lett. 1993, 34, 67–70.
25. Spectroscopic data of 7a: 1H NMR (400 MHz, MeOD)
8.23 (d, J = 7.5, 1H), 7.78 (d, J = 7.5, 1H), 7.64 (t, J = 7.5,
1H), 7.58 (t, J = 7.5, 1H); 13C NMR (100 MHz, MeOH)
144.2, 133.1, 131.8, 131.0, 128.3 (q, J = 6.4), 128.1 (q,
J = 32.4), 124.8 (q, J = 273.2); 19F NMR (376 MHz,
MeOD) ꢀ59.5 (s, 3F); IR (KBr) 3500 (br) (OH), 1271
References and notes
1. Weberndoerfer, V.; Brunnmueller, F.; Eisert, M.; Bermes,
R. U.S. Patent 4,560,745, 1985; Chem. Abstr. (for the
appl.) 1982, 96, 574.
2. Tian, S. H.; Shu, D.; Wang, S. J.; Xiao, M.; Meng, Y. Z.
Fuel Cells 2007, 7, 232–237.
3. Boesten, W. H. J.; Quaedflieg, P. J. L. M. PCT Int. Appl.
WO 9849133, 1998; Chem. Abstr. 1998, 129, 739.
4. (a) Levene, P. A.; Mikeska, L. A. J. Biol. Chem. 1927, 75,
587–605; (b) Levene, P. A.; Mikeska, L. A. J. Biol. Chem.
1925, 65, 515–518; (c) Vivian, D. L.; Reid, E. E. J. Am.
Chem. Soc. 1935, 57, 2559–2560.
5. Cerfontain, H.; Lambrechts, H. J. A.; Schaasberg, Z. R.
H.; Coombes, R. G.; Hadjigeorgion, P.; Tucker, G. P. J.
Chem. Soc., Perkin Trans. 2 1985, 659–667.
6. General procedure for working with fluorine: Fluorine is a
strong oxidant and a corrosive material. It should be used
only with an appropriate vacuum line.13 For the occa-
sional user, however, various premixed mixtures of F2 in
inert gases are commercially available, thereby simplifying