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Summary of Research Projects (Supports in 2004
Fiscal Year)
| Subjects |
Development of a New Method for Catalytic Removal of
Allyl Protecting Groups |
| Representative researcher |
Research Center for Materials Science,Nagoya University
Masato KITAMURA |
| A new catalytic
system consisting of [CpRu(CH3CN)3]PF6 and
2-quinolinecarboxylic acid has been found, through combinatorial
screening based on "redox-mediated donor-acceptor bifunctional
catalyst" concept, to show high reactivity and chemoselectivity
toward the cleavage of stable allyl ether C-O bond. The reaction
proceeds in alcoholic solvents without any need for additional
nucleophiles such as amines, metal hydrides, and metal enolates
that are required for the conventional Pd-based methods.
The coproduct is only volatile ether. The simple and clean
condition has realized the operational simplicity as well
as the easy isolation of deprotected products. The advantage
is particularly significant in the synthesis of bio-related
polar oligomers. Success in the isolation of the Ru(IV)-π-allyl
intermediate has led to the development of robust catalyst,
which can be stored in a usual vial for at least six months
without any decomposition. With the air and moisture stable
catalyst, not only allyl ethers but also allyl esters have
been successfully cleaved with up to 1000000 turn over number.
Preliminary study on mechanism has revealed the importance
of combination of a Ru salt of strong acid with a week acid
COOH to achieve the bifunctional ability. The present method
should open a new way to protecting group chemistry. |
|
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