Considering the aforementioned results, we put forth a potential mechanism of the epoxidation process (Scheme 6). First, the oxime is activated to form the corresponding iminologous pseudohalohydrin A. The lifetime of C should be short, thus facile fragmentation is expected due to the strain associated with small cyclic nitrilium ions, and the stability of its rearrangement to arrive at ketones 2. Based on the stereospecificity observed in the formation of (±)-trans-and (±)-cis-3r, the oxygen atom of C may attack the stereogenic carbon to kick off the nitrile leaving group to give 3 with stereoretention in a stepwise fragmentation process. However, due to the short lifetime of C and the favorable fragmentation to give D, this pathway is unlikely. Instead, the anionic oxygen atom in A likely undergoes direct intramolecular substitution to expel the oxime functional group by C-C cleavage in a concerted iminologous ring-closure to directly afford 3. This pathway is more likely due to the equatorial oxygen atom being situated antiperiplanar to the breaking C-C bond as seen in the X-ray crystal structure of (±)-cis-1r. Scheme 6. Proposed mechanism for the formation of ketonitiriles, epoxynitriles and dihydroisoxazoles via the activation of iminologous diols 1 with TsCl.