Intramolecular cyclization of ene-imine using dibutylzirconocene.
The reaction of ene-imine with Cp(2)ZrBu(2) was carried out. When a crude imine, which was prepared from ene-aldehyde and primary amine in the presence of MgSO(4), was treated with Cp(2)ZrBu(2) at room temperature overnight, cyclopentane derivative having trans-substituents was obtained in high yield along with a small amount of cyclopentane derivative having cis-substituents. Presumably, cis-zirconacycle is a thermodynamic product. Reactions using various ene-imines were carried out. In the case of ene-imine prepared from ene-aldehyde and (t)BuNH(2), only cyclopentane having cis-substituents was produced. In this reaction, chiral amine was used, and diastereoselective cyclization of ene-imine was carried out. As a result, cyclopentane derivative having cis-substituents was obtained in an optically active form after hydrogenolysis of the cyclized compound.
Makabe
Muneyoshi
M
Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Sato
Yoshihiro
Y
Mori
Miwako
M