Preparative separations and racemizations of enantiomeric diaziridines

Preparative separations or enrichments of enantiomers of diaziridines 1, 2, and 5 were achieved by liquid chromatography on triacetylcellulose, (+)-1 and (+)-2 being isolated almost pure (Table 1). Enantiomeric purities were determined by ¹H NMR in the presence of the optically active auxiliary compound (+)-Eu(hfbc)₃. The barriers to nitrogen inversion in 1 and 4 were determined and its lower limit in the nitrogen unsubstituted diaziridine 3 was estimated.