Silica-Supported Tantalum Catalysts for Asymmetric Epoxidations of Allyl Alcohols.
Tantalum good, titanium bad: This appears to be the case for silica-supported catalysts for the asymmetric epoxidation of allyl alcohols. Complexes such as [SiO-Ta(OEt)(4)] were prepared from silica and [Ta(=CHCMe(3))(CH(2)CMe(3))(3)], and in the presence of a tartrate and an alkyl hydroperoxide, these surface tantalum compounds lead to efficient and convenient catalysts for the asymmetric epoxidation of 2-propen-1-ol (R=H) and trans-2-hexen-1-ol (R=nPr; see reaction).
Meunier
D
Laboratoire de Chimie Organométallique de Surface, CPE-Lyon, 43, Boulevard du 11 Novembre 1918, F-69616 Villeurbanne Cedex (France).
Piechaczyk
A
de Mallmann A
Basset
JM