Configurational stability of pyramidal nitrogen in spiro-oxaziridines

Several optically active spiro-oxaziridines, whose stabilities were sufficient to obtain nitrogen inversion barriers without decomposition, have been synthesized. The magnitude of these barriers is markedly dependent on the nature of both nitrogen and carbon ring substituents. The relatively small solvent effect on the rate of racemization is attributed to the low basicity of the nitrogen atom and also to steric inhibition of solvation. Nitrogen inversion at ambient temperature in one oxaziridine was observed.