Spiroketal-Based Diphosphine Ligands in Pd-Catalyzed Asymmetric Allylic Amination of Morita–Baylis–Hillman Adducts: Exceptionally High Efficiency and New Mechanism

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• 作者：Xiaoming Wang ; Peihua Guo ; Zhaobin Han ; Xubin Wang ; Zheng Wang ; Kuiling Ding
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：January 8, 2014
• 年：2014
• 卷：136
• 期：1
• 页码：405-411
• 全文大小：414K
• ISSN：1520-5126

文摘

Exceptionally high activity (with a TON up to 4750) of the palladium complexes of SKP ligand was discovered in the catalysis of asymmetric allylic amination of MBH adducts with aromatic amines. A comprehensive mechanistic study indicates that the unique structural features of the SKP ligand, with a long P路路路P distance in its solid-state structure, were favorable for allowing two P atoms to play a bifunctional role in the catalysis. Herein, one of the P atom forms a C鈥揚 蟽-bond with the terminal carbon atom of allyl moiety as a Lewis base, and an alternative P atom coordinates to Pd atom. The cooperative action of organo- and organometallic catalysis discovered in the present catalytic system is most likely responsible for its high activity, as well as excellent regio- and enantioselectivities. The mechanism disclosed in the present catalytic system is distinct from most of the currently recognized mechanisms for Pd-catalyzed allylic substitutions.