|
Summary of Research Projects (Supports in 2003
Fiscal Year)
| Subjects |
Catalytic Asymmetric Reaction by Stereochemical Control Based
on CH/π Interaction |
| Representative researcher |
Kyushu University Ryoichi KUWANO |
| Reaction pathway of the
nucleophilic attack of malonaldehyde enolate to (π-allyl)palladium
complex was traced by means of DFT and MO study. The theoretical
studies suggested that the counter cation on the enolate
induced a dipole along an allylic carbon-palladium bond.
Interaction between the cation and the induced dipole contributes
stabilization of one transition state of this reaction. The
MO study on the reaction of 2-acetylcyclohexanone enolate
with (π-allyl)palladium
ligated by (R)-2,2'-bis(diphenylphosphino)biphenyl suggested
the presence of CH/π interaction between the enolate
and the phosphine ligand. The CH/π interaction was expected
to involve the control of stereochemistry in the catalytic
asymmetric reaction. The chiral palladium complex generated
in situ from [Pd(η3-allyl)Cl]2 and (R)-BINAP is a highly
enantioselective catalyst for the catalytic asymmetric alkylation
of 1,3-diketones with allylic acetates. The reaction provided
chiral 2,2-dialkyl-1,3-diketones with 64-89% ee in high yields.
The enantiomeric excesses are strongly affected by the γ-substituent
of allylic substrates. The alkylation of 2-acetylcyclohexanone
with allyl acetate proceeded with 64% ee, while cinnamyl
acetate gave the corresponding product with 85% ee. A variety
of unsymmetrical 1,3-diketones were alkylated with cinnamyl
acetate in high enantioselectivity by use of the BINAP-palladium
catalyst. |
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