An efficient and novel method for the deamination of trans-1-alkyl (H or benzoyl)-2-aroyl aziridines in a completely stereo-controlled reaction in the presence of N-bromosuccinimide/cerium (IV) ammonium nitrate is described. In comparison with the previous reported work, this reaction reveals a substituent-reactivity relationship and important role for the substituent on C1 and C2 in determining whether deamination or oxidation reaction takes place.