Cation‐Triggered Switchable Asymmetric Catalysis with Chiral Aza‐CrownPhos1. (11th February 2015)

• Record Type: Journal Article
• Authors: Ouyang, Guang‐Hui; He, Yan‐Mei; Li, Yong; Xiang, Jun‐Feng; Fan, Qing‐Hua
• Is Part Of: Angewandte Chemie. Volume 127:Number 14(2015)
• Page Start: 4408
• Page End: 4411
• Publication Date: 2015-02-11
• Subjects: Asymmetrische Katalyse -- Hydrierungen -- Kationen -- Kronenverbindungen -- Wirt‐Gast‐System; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201411593
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: An aza‐crown ether, modified phosphoramidite ligand, has been designed and synthesized. The ON/OFF reversible switch of catalytic activity for its rhodium catalyst was thoroughly investigated in the asymmetric hydrogenation of dehydroamino acid esters modulated by host–guest interactions. In the OFF state, the catalyst is almost inactive (less than 1 % conversion) because of the formation of an intermolecular sandwich complex by two aza‐crown ether moities and the cationic rhodium metal center. In using alkali‐metal‐cations as the trigger, the catalytic activity was turned ON and consequently resulted in full conversions and excellent enantioselectivities (up to 98 % ee ).