Stereospecific synthesis of bicyclic diaziridines: 4a-chloro-; 4e,6a- and 4a,6e-dichloro-5-methoxycarbonyl-1,6-diazabicyclo[3.1.0]hexanes

Amination of 2-methoxycarbonyl-3-chloro-1-pyrroline 1 with H₂NOSO₃H occurs predominantly from the anti side with respect to chlorine to afford the bicyclic diaziridine 2 with axial orientation of the 4-chloro substituent. Chlorination of 2 takes place exclusively in the 6-endo position to give 3a. 4,6-Dichlorodiaziridine is transformed from chair 3a into boat 3b as a result of endo–exo isomerization.