Highly enantioselective electrophilic amination and Michael addition of cyclic β-ketoesters induced by lanthanides and (S,S)-ip-pybox: The mechanism
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High enantioselection is obtained in Michael additions of cyclic β-ketoesters in the presence of lanthanium triflates and (S,S)-ip-pybox. Intermediates based on simultaneous coordination of the lanthanide to both (S,S)-ip-box and β-ketoester (in keto and enolate forms) are detected by means of ESI mass spectrometry and NMR experiments, and a possible mechanism is proposed through theoretical calculations. © 2007 American Chemical Society.