Highly Enantioselective Electrophilic Amination and Michael Addition of Cyclic β-Ketoesters Induced by Lanthanides and (<i>S</i>,<i>S</i>)-ip-pybox: The Mechanism^⊥

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.