Enantioselective Conversion of Achiral Cyclohexadienones to Chiral Cyclohexenones by Desymmetrization

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• 作者：Yixin Han ; Simon Breitler ; Shao-Liang Zheng ; E. J. Corey
• 刊名：Organic Letters
• 出版年：2016
• 出版时间：December 2, 2016
• 年：2016
• 卷：18
• 期：23
• 页码：6172-6175
• 全文大小：371K
• ISSN：1523-7052

文摘

The enantioselective reduction of prochiral 4,4-disubstituted 2,5-cyclohexadienones to chiral 2-cyclohexenones has been accomplished by the use of a carefully selected chiral bisphosphine–CuI complex and diisobutylaluminum hydride–hexamethylphosphoric triamide complex. This reagent has provided access to a key bicyclic intermediate for the total synthesis of the natural enantiomer of the pentacyclic sesterterpene retigeranic acid that involves spatial discrimination between CH₃ and CH₂CH₂R substituents, an operation that has been elusive previously. In addition, a second method for desymmetrization is described using catalytic enantioselective [4 + 2]-cycloaddition of cyclopentadiene to prochiral 4,4-disubstituted 2,5-cyclohexadienones.