Ring Expansion of Donor-Acceptor Cyclopropane via Substituent Controlled Selective N-Transfer of Oxaziridine: Synthetic and Mechanistic Insights

A distinctive N-substituent controlled electrophilic N-transfer of oxaziridines with donor-acceptor cyclopropanes in the presence of MgI2 is reported. Contrary to earlier reports, the oxaziridine having bulkier N-substituents can also give N-transferred product instead of the O-transferred one. Interestingly, the oxaziridines having alpha-H containing N-substituents lead to the pyrrolidine derivatives through [3 + 2] cycloaddition. A mechanistic reasoning for this divergent reactivity 18 depicted by density functional theory calculations and validated through energy decomposition analysis.