A broad range of N-carbamoyl aziridines were obtained and then treated by the diethyl phosphonate anion to afford α-methylene-gem-bisphosphonate aziridines. Study of the reaction's scope and additional experiments indicate that the transformation proceed via a new mechanism involving the chelation of lithium ion. This last is crucial for the reaction to occur and disfavors the aziridine ringopening. A phosphonate-phosphate rearrangement from a -hydroxybisphosphonate aziridine intermediate is also proposed for the first time. This reaction provides a simple and convenient method for the synthesis of highly functionalized phosphonylated aziridine motif.