Oxaziridines 2a and 2b

The energy barrier for inversion of a tetrahedral (sp3) nitrogen atom is influenced by various structural features.

The diastereoisomeric oxaziridines 2a and 2b are configurationally stable at room temperature and separable by chromatography. They equilibrate on heating at 115 °C, with 2b predominant by about 4:1. Oxaziridines tend to be resistant to inversion at N due to both the strain of the three-membered ring and the inductive (sigma-attractor) effect of the endocyclic O atom.

Stereochemical inversion of pyramidal nitrogen in 2,3-dimethyl-3-benzyloxaziridine
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Proton-resonance studies of the inversion at tervalent nitrogen atoms, III. Separation of the invertomers of 2,3-dimethyl-3-benzyloxaziridine; A. Mannschreck, J. Linss and W. Seitz, Justus Liebigs Ann. Chem., 1969, 727, 224–227 (DOI: https://doi.org/10.1002/jlac.19697270126).