ORGANIC
LETTERS
2003
Vol. 5, No. 19
3423-3425
Manganese/Bicarbonate-Catalyzed
Epoxidation of Lipophilic Alkenes with
Hydrogen Peroxide in Ionic Liquids
Kit-Ho Tong, Kwok-Yin Wong, and Tak Hang Chan*
Department for Applied Biology and Chemical Technology and the Open Laboratory
for Chiral Technology, Institute of Molecular Technology for Drug DiscoVery and
Synthesis, The Hong Kong Polytechnic UniVersity, Hung Hom, Hong Kong SAR, China
Received June 23, 2003
ABSTRACT
Effective epoxidation of lipophilic alkenes using hydrogen peroxide was accomplished with the manganese sulfate/bicarbonate catalytic system
in an ionic liquid at room temperature.
In view of the industrial importance of epoxides, environ-
mentally friendly methods for the epoxidation of alkenes
have been a subject of current research interest. Much
attention has been focused on the use of hydrogen peroxide
as a green oxidant because it is cheap and gives water as
the only byproduct.11 Many catalytic systems based on
different metals have been employed in conjunction with
hydrogen peroxide for the epoxidation of alkenes.22 Note-
worthy among them are the recent reports by Burgess, which
showed that a catalytic amount of manganese sulfate with
sodium bicarbonate is quite effective in promoting the
epoxidation of alkenes with hydrogen peroxide in aqueous
media.33 Since both the manganese and the bicarbonate salts
are inexpensive and relatively nontoxic, the reaction may
have practical applications. A common drawback for most
reactions in aqueous media is the fact that an organic
cosolvent is often required for water-insoluble lipophilic
substrates. In the case of manganese/bicarbonate-catalyzed
epoxidation of lipophilic alkenes, cosolvents such as DMF
or t-BuOH were used. This defeats the aim of reducing the
environmental burden of volatile organic contaminants.
Recently, the use of ionic liquids as environmentally
benign solvents for a broad range of chemical processes has
been advocated.4 This is due to a number of intriguing
properties of ionic liquids: high thermal and chemical
stability, no measurable vapor pressure, nonflammability, and
high loading capacity. In many cases, the ionic liquids can
be recycled. Numerous catalytic reactions, including bio-
catalytic reactions, can be carried out in ionic liquids.5
Epoxidation reactions in ionic liquids have been explored.
In two reports where Mn complexes were used as catalysts,
CH2Cl2 was used as a cosolvent and halogenated oxidants
as the oxidizing agent; both were undesirable on environ-
mental grounds.6 When aqueous hydrogen peroxide was used
as the oxidant with other catalysts, either the substrates were
limited to electrophilic alkenes with strongly electron-
withdrawing substituents,7 hydrolysis of the epoxide was
(4) (a) Ionic Liquids. Industrial Applications to Green Chemistry; Rogers,
R. D., Seddon, K. R., Ed.; ACS Symposium Series 818; American Chemical
Society: Washington, DC, 2002. (b) Wasserscheid, P.; Welton, T. Ionic
Liquids in Synthesis; Wiley-VCH: Weinheim, 2003.
(5) For examples, see: (a) Sheldon, R. A.; Lau, R. M.; Sorgedrager, M.
J.; van Rantwijk, F.; Seddon, K. R. Green Chem. 2002, 4, 147. (b) Bortolini,
O.; Conte, V.; Chiappe, C.; Fantin, G.; Fogagnolo, M.; Maietti, S. Green
Chem. 2002, 4, 94. (c) Lau, R. M.; van Rantwijk, F.; Seddon, K. R.; Sheldon,
R. A. Org. Lett. 2000, 2, 4189.
(1) For recent review, see: Grigoropoulou, G.; Clark, J. H.; Elings, J.
A. Green Chem. 2003, 5, 1.
(2) Lane B. S.; Burgess, K. Chem. ReV. 2003, 103, 2457.
(3) (a) Lane, B. S.; Burgess, K. J. Am. Chem. Soc. 2001, 123, 2933. (b)
Lane, B. S.; Vogt, M.; DeRose, V. J.; Burgess, K. J. Am. Chem. Soc. 2002,
124, 11946.
(6) (a) Song, C. E.; Roh, E. J. Chem. Commun. 2000, 837. (b) Li, Z.;
Xia, C. G. Tetrahedron Lett. 2003, 44, 2069.
(7) Bortolini, O.; Conte, V.; Chiappe, C.; Fantin, G.; Forgagnolo, M.;
Maietti, S. Green Chem. 2002, 4, 94.
10.1021/ol035163h CCC: $25.00 © 2003 American Chemical Society
Published on Web 08/22/2003