persulfuric acid (Caro’s acid) in their pioneering work on
the oxidation of ketones to esters. Oxone is very efficient
in the Baeyer-Villiger oxidation,5 but it requires an
aqueous reaction medium that leads to extensive hy-
drolysis of the reaction products. This side process can
be minimized, but not completely avoided, by using
biphasic conditions in the presence of a phase-transfer
catalyst6 or by using the sylilated derivative of peroxo-
monosulfuric acid.7
Baeyer-Villiger Oxidation with Potassium
Peroxomonosulfate Supported on Acidic
Silica Gel
Mar´ıa E. Gonza´lez-Nu´n˜ez, Rossella Mello,
Andrea Olmos, and Gregorio Asensio*
Departamento de Quı´mica Orga´nica, Universidad de
Valencia, Avda. V. Andre´s Estelle´s s/n,
46100 Burjassot, Valencia, Spain
In this context, the use of Oxone supported on a solid
inorganic matrix under anhydrous conditions could avoid
undesired hydrolysis of the esters formed in the Baeyer-
Villiger reaction, provided that the supported peracid
remains reactive. Caro’s acid supported on silica has been
prepared8 by treating silica with a mixture of potassium
persulfate and concentrated sulfuric acid, but no details
were provided concerning the nature of the supported
active species. It has been reported that this reagent can
be used in a variety of transformations such as the
oxidation of thiols to disulfides8h and of sulfides to
sulfoxides,8e aromatization of 1,4-dihydropyridines,8c and
the conversion of oximes,8f hydrazones, and semi-
carbazones8b to carbonyl compounds, although other
reactions, such as the deacetalization of carbonyl com-
pounds8a or deprotection of silyl ethers,8d could be at-
tributed to the strongly acidic character of the reagent
rather than to its oxidizing capability. Recently, it has
been reported that the surface of wet alumina9a or
silica9b,c can activate Oxone for oxygen-transfer reactions
to ketones,9a sulfides,9b and amines.9c However, the
approach described in these reports9 does not actually
involve supported Oxone, but rather the existence in the
medium of a heterogeneous mixture of wet silica or
alumina, the inorganic triple salt (2KHSO5‚KHSO4‚
K2SO4) and the substrates.
Received August 2, 2005
Potassium peroxomonosulfate deposited onto silica SiO2‚
KHSO5 efficiently reacts with ketones in dichloromethane
at room temperature to give the corresponding esters or
lactones in quantitative yields. This method avoids hydroly-
sis of the reaction products. The Baeyer-Villiger reaction
is catalyzed by potassium hydrogensulfate present in the
supported reagent.
The Baeyer-Villiger oxidation of ketones 1 into esters
and lactones 2 is an important transformation in organic
synthesis,1 particularly for ring-expansion in the synthe-
sis of natural products and the preparation of monomers
for polymerization. The most common reagents for per-
forming these transformations are organic peracids1 such
as m-chloroperbenzoic acid or trifluoroperacetic acid (eq
1). However, the hazards associated with these reagents
have prompted the search for alternative approaches,
such as the use of catalysts that activate hydrogen
peroxide or dioxygen,2 which circumvent both the envi-
ronmental and safety issues associated with the classical
Baeyer-Villiger oxidation.
We report here that anhydrous potassium peroxo-
monosulfate supported on silica (SiO2‚KHSO5) efficiently
oxidizes a variety of ketones 1 to the corresponding esters
or lactones 2 in quantitative yields at room temperature.
The Baeyer-Villiger reaction is catalyzed by potassium
hydrogensulfate present in the supported reagent. This
method also avoids hydrolysis of the reaction products.
Potassium peroxomonosulfate supported on silica was
obtained by mixing a ca. 2 M aqueous solution of the
(5) Kennedy, R. J.; Stock, A. M. J. Org. Chem. 1960, 25, 1901.
(6) Camporeale, M.; Fiorentino, M.; Mello, R.; Curci, R. XVII
National Meeting of Organic Chemistry; Italian Chemical Society:
Fiuggi,Italy, 1987.
(7) Adam, W.; Rodr´ıguez, A. J. Org. Chem. 1979, 44, 4969-4970.
(8) (a) Lakouraj, M. M.; Tajbakhsh, M.; Khojasteh, V.; Gholami, M.
H. Phosphorous, Sulfur Silicon Relat. Elem. 2004, 179, 2645. (b)
Tajbakhsh, M.; Lakouraj, M. M.; Gholami, M. H.; Ramzanian-Lehmali,
F. Phosphorous, Sulfur Silicon Relat. Elem. 2004, 179, 1731. (c)
Tajbakhsh, M.; Lakouraj, M. M.; Khojasteh, V. Phosphorous, Sulfur
Silicon Relat. Elem. 2004, 179, 463. (d) Lakouraj, M. M.; Tajbakhsh,
M.; Khojasteh, V. Phosphorous, Sulfur Silicon Relat. Elem. 2003, 178,
1865. (e) Lakouraj, M. M.; Movassagh, B.; Ghodrati, K. Synth.
Commun. 2002, 32, 847. (f) Movassagh, B.; Lakouraj, M. M.; Ghodrati,
K. Synth. Commun. 2000, 30, 4501. (g) f) Movassagh, B.; Lakouraj,
M. M.; Ghodrati, K. Synth. Commun. 2000, 30, 2353. (h) Movassagh,
B.; Lakouraj, M. M.; Ghodrati, K. Synth. Commun. 1999, 29, 3597.
(9) (a) Hirano, M.; Oose, M.; Morimoto, T. Chem. Lett. 1991, 331-
332. (b) Kropp, P. J.; Breton, G. W.; Fields, J. D.; Tung, J. C.; Loornis,
B. R. J. Am. Chem. Soc. 2000, 122, 4280-4285. (c) Fields, J. D.; Kropp,
P. J. J. Org. Chem. 2000, 65, 5937.
Potassium peroxomonosulfate triple salt3 (2KHSO5‚
KHSO4‚K2SO4) (Oxone, caroate) is a good alternative to
organic peracids in the Baeyer-Villiger reaction since it
is inexpensive and safe. In fact, Baeyer and Villiger used4
(1) Krow, G. R. Org. React. 1993, 43, 251. (b) Renz, M.; Meunier, B.
Eur. J. Org. Chem. 1999, 737.
(2) (a) tenBrink, G.-J.; Arends, I. W. C. E.; Sheldon, R. A. Chem.
Rev. 2004, 104, 4150. (b) Strukul, G. Angew. Chem., Int. Ed. 1998, 37,
1198-1209. Bolm, C. In Advances in Catalytic Processes; Doyle, M.
P., Ed.; JAI Press: Greenwich, 1997; Vol. 2, p 43.
(3) Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis; Wiley:
New York, 1967; Vol. 1, p 952.
(4) Baeyer, A.; Villiger, V. Ber. Dtsch. Chem. Ges. 1899, 32, 3265.
10.1021/jo051614v CCC: $30.25 © 2005 American Chemical Society
Published on Web 11/23/2005
J. Org. Chem. 2005, 70, 10879-10882
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