Catalytic Enantioselective Epoxidation of Homoallylic Alcohols by Chiral Zirconium Complexes
摘要:
Catalytic enantioselective epoxidation of homoallylic alcohols using Zr(Ot-Bu)(4) and tartrate ester (or tartramide) has been developed. In the Zr(Ot-Bu)(4)/diisopropyl tartrate-catalyzed epoxidation, the reverse of the enantiofacial preference was observed, depending on the Zr/ligand ratios of 1:1 or 1:2.
Zirconium(IV)- and Hafnium(IV)-Catalyzed Highly Enantioselective Epoxidation of Homoallylic and Bishomoallylic Alcohols
作者:Zhi Li、Hisashi Yamamoto
DOI:10.1021/ja100951u
日期:2010.6.16
enantioselective epoxidation of homoallylic alcohols and bishomoallylic alcohols, which used to be quite difficult substrates for other types of asymmetricepoxidation reactions. The performance of the catalyst was improved by adding polar additive and molecular sieves. For homoallylic alcohols, the reaction could provide epoxy alcohols in up to 83% yield and up to 98% ee, while, for bishomoallylic alcohols, up
A new chiral tethered 8-quinolinol-based ligand class is developed. The binuclear titanium complex of the ligand operates through a novel mechanism allowing for the regio- and stereoselective epoxidation of primary and tertiary homoallylic alcohols (up to 98% ee), as well as first examples of 2-allylic phenols (up to 92% ee). The new catalyst system also promotes the asymmetric oxidation of gamma-hydroxypropyl sulfides giving an important class of chiral sulfoxides that have been inaccessible to date (up to 95% ee).