One-step Preparation of N-Unprotected Aziridines from 2H-Azirines by Addition of Ketene Silyl Acetals Catalyzed by Lewis Acids

The nucleophilic addition of ketene silyl acetals 2 into 2H-azirines 1 proceeded in the presence of Lewis acids such as InX3 or Sc(OTf)3 to give N-unprotected aziridines 3. The mild Lewis acidity of the catalyst is important for the achievement of this coupling. The generated aziridine 3 could then be transformed into either oxazolines or γ–amino carbonyls.