Ring-cleavage reactions aziridine

Azetidine can be considered as a fairly typical cyclic amine. Strain in the four-membered ring is less than that in the three-membered aziridine system, and as a result azetidines show few, if any, of the exceptional properties associated with aziridines. Thus, ring cleavage reactions occur with greater ease than in larger ring cyclic amines, but much less readily than with aziridine for example, unlike aziridines, azetidines do not function as alkylating... 

When the aziridine nitrogen is substituted, Michael-type addition to the acetylene is not possible. Reactions are then usually preceded by ring cleavage with the formation of an azomethine ylid. The product obtained depends on the nitrogen substituent. Heine and co-workers 45,46 used m-l,2,3-triphenylaziridine (27) with DMAD, DEAD, EP, and EPP. The DMAD gave 98% of compound 28 after refluxing in toluene... 

The ring-opening reaction can also be induced by attack of oxygen-centered nucleophiles, as demonstrated by the facile ring cleavage of the unsymmetrical bicyclic aziridine 60 with methanol in the presence of boron trifluoride etherate to give the product of attack at the more-substituted aziridine carbon <2002T7355>. Indium triflate... 

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