Highly Enantioselective Michael Additions of Indole to Benzylidene Malonate Using Simple Bis(oxazoline) Ligands: Importance of Metal/Ligand Ratio

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• 作者：Ramesh Rasappan ; Markus Hager ; Anja Gissibl ; Oliver Reiser
• 刊名：Organic Letters
• 出版年：2006
• 出版时间：December 21, 2006
• 年：2006
• 卷：8
• 期：26
• 页码：6099 - 6102
• 全文大小：83K
• 年卷期：v.8,no.26(December 21, 2006)
• ISSN：1523-7052

文摘

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Simple bis(oxazoline) ligands, especially azabis(oxazolines), can catalyze the copper-catalyzed addition of indoles to benzylidene malonatesin up to >99% ee, provided that excess of chiral ligand is avoided. The paradigm followed in many asymmetric catalyses that an excess ofchiral ligand with respect to the metal should improve enantioselectivity because a background reaction by free metal is suppressed, is notapplicable here, which might call for revisiting some of the many copper(II)-bis(oxazoline)-catalyzed processes known.