8110
A. Wolfson et al. / Tetrahedron Letters 43 (2002) 8107–8110
ILs with RuCl2(PPh3)3 complex was also tested (Table
2). Though expectedly10 the reactivity of aliphatic alco-
hols was lower than that of aromatic alcohols, the
reaction was performed successfully without any over-
oxidation of the formed aldehyde to the corresponding
acid. It is clear that the reaction in Aliquat is faster
than in tetramethylammonium hydroxide, except for
the oxidation of benzyl alcohol. The difference in activ-
ity between the two ILs is more pronounced in the
oxidation of aliphatic alcohols.
5. Lenz, R.; Ley, S. V. J. Chem. Soc., Perkin Trans. 1 1997,
3291.
6. Hinzen, B.; Ley, S. V. J. Chem. Soc., Perkin Trans. 1
1997, 1907.
7. Bleloch, A.; Johnson, B. F. G.; Ley, S. V.; Price, A. J.;
Shephard, D. S.; Thomas, A. W. Chem. Commun. 1999,
1907.
8. Matsumoto, M.; Ito, S. J. Chem. Soc., Chem. Commun.
1981, 907.
9. Hanyu, A.; Takezawa, E.; Sakaguchi, S.; Ishii, Y. Tetra-
hedron Lett. 1998, 39, 5557.
The aerobic oxidation of several aliphatic and aromatic
alcohols into the corresponding aldehydes and ketones
with ruthenium catalysts has been successfully demon-
strated in commercially available ILs. The reaction is
fast and selective under mild conditions and does not
require the addition of co-catalyst, while allowing facile
isolation of the product and re-use of the complex. The
activity in the oxidation of several alcohols in the
presently reported catalytic systems is much higher than
that of other aerobic oxidations in ILs, even with lower
catalyst loading and devoid of any additive. Even when
compared with the highly efficient catalytic oxidation of
alcohols with the combination of a RuCl2(PPh3)3 com-
plex and TEMPO, the activity of the new catalytic
system is very high.
10. Dijksman, A.; Arends, I. W. C. E.; Sheldon, R. A. Chem.
Commun. 1999, 1591.
11. Dijksman, A.; Gonza´les, A. M.; Mairta, A.; Payeras, I.;
Arends, I. W. C. E.; Sheldon, R. A. J. Am. Chem. Soc.
2001, 123, 6826.
12. Welton, T. Chem. Rev. 1999, 99, 8.
13. Sheldon, R. A. Chem. Commun. 2001, 23, 2399.
14. Olivier-Bourbigou, H.; Mangna, L. J. Mol. Cat 2002,
182–183, 419.
15. Xu, L.; Chen, W.; Xiao, J. Organometallics 2000, 19,
1123.
16. Herrmann, W. H.; Bohm, V. P. W. J. Organomet. Chem.
1999, 572, 141.
17. Guernik, S.; Wolfson, A.; Herskowitz, M.; Greenspoon,
N.; Geresh, S. Chem. Commun. 2001, 22, 2314.
18. Howart, J. Tetrahedron Lett. 2000, 41, 6627.
19. Ley, S. V.; Ramarao, C.; Smith, M. D. Chem. Commun.
2001, 2278.
Acknowledgements
20. Farmer, V.; Welton, T. Green Chem. 2002, 4, 97.
21. Ansai, I. A.; Gree, R. Org. Lett. 2002, 4, 1507.
22. Gaillon, L.; Bedioui, F. Chem. Commun. 2001, 16, 1458.
23. Owens, G. S.; Abu-Omar, M. M. Chem. Commun. 2000,
13, 1165.
24. Typical reaction procedure: 0.3 mmol substrate and 3
mmol catalyst were added to a glass vial with 1.5 g IL.
The mixture was stirred at 80°C for 5 min and then
flushed with oxygen for 2 min. The product was extracted
by addition of 3×5 mL n-octane and mixing at 80°C for
5 min.
S.W. acknowledges a fellowship from KU Leuven.
A.W. is grateful for a postdoctoral fellowship in the
frame of the IAP-network in supramolecular chemistry
and catalysis, sponsored by the Belgian Federal Gov-
ernment. The research is done in the frame of the same
network.
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