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).
Tungsten-Catalyzed Asymmetric Epoxidation of Allylic and Homoallylic Alcohols with Hydrogen Peroxide
作者:Chuan Wang、Hisashi Yamamoto
DOI:10.1021/ja411379e
日期:2014.1.29
A simple, efficient, and environmentally friendly asymmetricepoxidation of primary, secondary, tertiary allylic, and homoallylic alcohols has been accomplished. This process was promoted by a tungsten–bishydroxamic acid complex at room temperature with the use of aqueous 30% H2O2 as oxidant, yielding the products in 84–98% ee.
伯、仲、叔烯丙醇和高烯丙醇的简单、高效和环境友好的不对称环氧化已经完成。该过程在室温下由钨-双异羟肟酸配合物促进,使用 30% H2O2 水溶液作为氧化剂,产生 84-98% ee 的产物。