Guanidinium Ylide Mediated Aziridination: Identification of a Spiro Imidazolidine-Oxazolidine Intermediate

We successfully isolated a spiro imidazolidine-oxazolidine
intermediate in the reaction of guanidinium ylide mediated
aziridination using α-bromocinnamaldehyde. X-ray crystallographic analysis unambiguously revealed that the stereogenic centers of the spiro intermediate were in a trans
configuration. The role of the spiro compound as an
intermediate in the aziridination reaction was confirmed by
observation of its smooth chemical conversion into aziridine
products.