Cation-triggered switchable asymmetric catalysis with chiral Aza-CrownPhos.
Angew Chem Int Ed Engl
; 54(14): 4334-7, 2015 Mar 27.
Article
em En
| MEDLINE
| ID: mdl-25677923
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 OFFâ
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).
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MEDLINE
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En
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Angew Chem Int Ed Engl
Ano de publicação:
2015
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Article