Hickey Matthew, Goeddel David, Crane Zackary, Shi Yian
Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA.
Proc Natl Acad Sci U S A. 2004 Apr 20;101(16):5794-8. doi: 10.1073/pnas.0307548101. Epub 2004 Apr 6.
Asymmetric epoxidation of various styrenes using carbocyclic oxazolidinone-containing ketone 3 has been investigated. High enantioselectivity (89-93% enantiomeric excess) has been attained for this challenging class of alkenes. Mechanistic studies show that substituents on the ketone catalyst can have electronic influences on secondary orbital interactions, which affects the competition between spiro and planar transition states and, ultimately, enantioselectivity. The results described herein not only reveal the potential of chiral dioxirane catalyzed asymmetric epoxidation as a viable entry into this important class of olefins but also further enhance the understanding of the mechanistic aspects of chiral ketone-catalyzed asymmetric epoxidation.
使用含碳环恶唑烷酮的酮3对各种苯乙烯进行不对称环氧化反应已得到研究。对于这类具有挑战性的烯烃，已实现了高对映选择性（对映体过量89 - 93%）。机理研究表明，酮催化剂上的取代基可对二级轨道相互作用产生电子影响，这会影响螺环和平面过渡态之间的竞争，并最终影响对映选择性。本文所述结果不仅揭示了手性二氧杂环丙烷催化不对称环氧化作为进入这类重要烯烃的可行途径的潜力，还进一步加深了对手性酮催化不对称环氧化机理方面的理解。
