Solvent-Dependent Divergent Functions of Sc(OTf)3 in Stereoselective Epoxide-Opening Spiroketalizations

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• 作者：Indrajeet Sharma ; Jacqueline M. Wurst ; Derek S. Tan
• 刊名：Organic Letters
• 出版年：2014
• 出版时间：May 2, 2014
• 年：2014
• 卷：16
• 期：9
• 页码：2474-2477
• 全文大小：311K
• 年卷期：v.16,no.9(May 2, 2014)
• ISSN：1523-7052

文摘

A stereocontrolled synthesis of benzannulated spiroketals has been developed using solvent-dependent Sc(OTf)₃-mediated spirocyclizations of exo-glycal epoxides having alcohol side chains. In THF, the reaction proceeds via Lewis acid catalysis under kinetic control with inversion of configuration at the anomeric carbon. In contrast, in CH₂Cl₂, Br酶nsted acid catalysis under thermodynamic control leads to retention of configuration. The reactions accommodate a variety of aryl substituents and ring sizes and provide stereochemically diverse spiroketals.