Diazirines as potent electrophilic nitrogen sources: application to the synthesis of pyrazoles.

Even after more than 50 years since its discovery, the electrophilic potential of diazirines was never truly exploited. This longstanding limitation has been resolved. N-Monosubstituted diaziridines and hydrazones are obtained by nucleophilic additions. They release, under hydrolysis conditions, the corresponding monosubstituted hydrazines. The latter were converted to pyrazoles in high yields. The adamantanone can be recovered in 80-100% yields. This work demonstrates the potential of diazirines as electrophilic nitrogen sources with recoverable protecting groups.