Bidding - the International Association of the Catalysis Societies

C&EN Volume 78, Number 21, p. 8-9 (May 22, 2000)
Epoxidation Catalyst Immobilized In Ionic Liquid
Chemists in South Korea have employed a room-temperature ionic liquid to immobilize, recover, and
recycle a homogeneous chiral catalyst that is used for the asymmetric epoxidation of alkenes.
Principal research scientist Choong Eui Song and research scientist Eun Joo Roh at the Korea Institute of
Science & Technology, Seoul, immobilized a catalyst known as Jacobsen's chiral (salen)- manganese(III)
epoxidation catalyst in the air- and moisture-stable ionic liquid 1-butyl-3-methylimidazolium
hexafluorophosphate, [bmim][PF 6 ]. They showed that the immobilized catalyst can be recycled five times
when used for the asymmetric epoxidation of 2,2-dimethylchromene and other alkenes with only a slight
decrease in enantioselectivity and activity [Chem. Commun., 2000, 837].
"Song and Roh describe remarkable results in a very exciting new field--oxidation chemistry in ionic
liquids," notes Peter Wasserscheid, chemistry lecturer at the University of Technology, Aachen, in
Germany, whose own research includes catalytic reactions in ionic liquids. "Their work gives a clear hint
that selective oxidation may be another area where the unique solvent properties of ionic liquids can
make a difference."
Immobilized chiral catalysts offer practical advantages over soluble catalysts by facilitating separation of
the catalyst from reagents and products after the reaction and by simplifying catalyst recycling, Song and
Roh point out. However, most immobilization techniques, such as anchoring a catalyst to a solid support,
usually require structural modification of the catalyst and can lead to partial loss of activity or
enantioselectivity or both.
"Although several attempts to immobilize Jacobsen's (salen)Mn(III) epoxidation catalyst have been made,
no successful procedure has been reported until now," Song tells C&EN. "We have shown that Jacobsen's
catalyst in a reaction medium containing [bmim][PF 6 ] exhibits comparable enantioselectivities in
asymmetric epoxidation of alkenes to those obtained without an ionic liquid.
"One of the major novelties of this immobilization technology using ionic liquids is that the
homogeneous chiral catalyst can be used without any structural modification," he continues. "Moreover,
we observed remarkable rate enhancement for the asymmetric epoxidation of 2,2-dimethylchromene in
the presence of [bmim][PF 6 ]."
Song and Roh showed that epoxidation of the alkene was complete in two hours, whereas the same
reaction without an ionic liquid required six hours.
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