Azirines aziridines, 2-alkoxy

The reaction of 34, which contains a secondary hydrogen alpha to the hydrazone, with sodium isopropoxide gave a mixture of alkoxy-aziridines (35 and 36). On heating, 35 and 36 partially eliminated isopropanol to give the 1-azirine (37). 

Nucleophilic attack on azirines at the C=N double bond is useful for the preparation of substituted aziridines. The C=N bond is more electrophilic than a normal imine due to the strain of the three-membered ring. Nucleophilic additions to 3-alkoxy- and 3-amino-2//-azirines are especially well studied, e.g., Scheme 36. Many of these reactions involve assistance by protonation of the nitrogen. 

The Neber rearrangement of oxime 0-sulfonates to 2//-azirines (or a-amino ketones, after aqueous acid workup) has been reviewed, together with the modified Neber , involving /V,/V,A-trimethylhydrazonium iodides.With an excess of base, the a-amino acetal can be formed from the 2//-azirine via the unstable 2-alkoxy aziridine. 

A review on the base-promoted rearrangement of oxime 0-derivatives, commonly O-sulfonates, and the similar reaction of AA A-trimethylhydrazonium iodides to give 2H-azirines or, upon subsequent aqueous acidic workup, a-amino ketones has been reported. With excess base, a-amino ketal is formed from the 2//-azirine via an unstable 2-alkoxy aziridine which can be isolated or hydrolysed in situ to a-amino ketone. ... 

---