Regio- and Enantioselective Catalytic Monoepoxidation of Conjugated Dienes: Synthesis of Chiral Allylic cis-Epoxides

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• 作者：Jawahar L. Jat ; Saroj Ranjan De ; Ganesh Kumar ; Adeniyi Michael Adebesin ; Shyam K. Gandham ; John R. Falck
• 刊名：Organic Letters
• 出版年：2015
• 出版时间：February 20, 2015
• 年：2015
• 卷：17
• 期：4
• 页码：1058-1061
• 全文大小：341K
• ISSN：1523-7052

文摘

Ti(IV)-salan 4 catalyzes the diastereo- and enantioselective monoepoxidation of conjugated dienes using 30% H₂O₂ at rt or below even in the presence of other olefins and adjacent stereocenters. Its enantiomer, ent-4, provides access to the opposite diastereomer or enantiomer. The resultant chiral allylic epoxides, and the triols derived from them, are versatile synthetic intermediates as well as substructures present in many bioactive natural products. The epoxidation is highly specific for Z-olefins. For 1-acyl(silyl)oxypenta-2,4-dienes, epoxidation of the distal olefin is generally favored in contrast to the adjacent regioselectivity characteristic of Sharpless, peracid, and other directed epoxidations of hydroxylated dienes.