Construction of Isoxazolidin-5-ones with a Tetrasubstituted Carbon Center: Enantioselective Conjugate Addition Mediated by Phase-Transfer Catalysis

Abstract : An efficient enantioselective Michael reaction of readily available α‐substituted N‐Boc isoxazolidin‐5‐ones is described under phase transfer conditions with up to 95:5 er. The organocatalytic process is promoted by a low catalytic loading of a commercially available N‐spiro quaternary ammonium salt. This sequence opens an entry to chiral heterocyclic platforms displaying a β‐amino carbonyl motif with an α‐all‐carbon quaternary stereogenic center. The methodology was also successfully extended to the asymmetric amination reaction using an azodicarboxylate electrophile.