Reversible nucleophilic addition can lower the observed enantioselectivity in palladium-catalyzed allylic amination reactions with a variety of chiral ligands

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• 作者：Nicholas S. Caminiti ; Madison B. Goodstein ; Isabelle N.-M. Leibler ; Bryan S. Holtzman ; Zitong B. Jia ; Michael L. Martini ; Nathaniel C. Nelson ; Richard C. Bunt ; ^{rbunt@middlebury.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Enantioselective ; Palladium catalysis ; Allylic amination ; Reversibility ; Chiral ligand
• 刊名：Tetrahedron Letters
• 出版年：2015
• 出版时间：30 September 2015
• 年：2015
• 卷：56
• 期：40
• 页码：5445-5448
• 全文大小：540 K

文摘

Palladium-catalyzed allylic amination is an important synthetic reaction that is also frequently used as a benchmark for the design and evaluation of new chiral ligands. The effect of reversible nucleophilic addition on the reaction of benzylamine with (E)-1,3-diphenylallyl ethyl carbonate (1) in CH₂Cl₂ was examined with 12 different chiral ligands across a range of scaffolding types. In 8 out of 12 cases the observed ee was significantly higher when DBU or Cs₂CO₃ was added to suppress the proton-driven reversibility. For chiral ligand screening with this test reaction, adding DBU or Cs₂CO₃ provides a better measure of the ligand’s inherent enantioselectivity.