Cation‐Triggered Switchable Asymmetric Catalysis with Chiral Aza‐CrownPhos1. Issue 14 (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 international edition. Volume 54:Issue 14(2015)
• Page Start: 4334
• Page End: 4337
• Publication Date: 2015-02-11
• Subjects: asymmetric catalysis -- cations -- crown compounds -- host‐guest systems -- hydrogenation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201411593
• Languages: English
• ISSNs: 1433-7851

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 ). Abstract : Quick on the trigger : A new kind of phosphoramidite ligand, modified by an aza‐crown ether, has been designed and synthesized. The activity of its rhodium catalyst can be reversibly switched "ON" and "OFF" in the asymmetric hydrogenation of dehydroamino acid esters by modulations derived from host–guest interactions.