Diazirines chemical properties

The proof of the three-membered structure of the diazirines concludes the discussion on the three-membered ring structure of the aliphatic diazo compounds. The knowm linear aliphatic diazo compounds and the newly prepared cyclic diazo compounds (diazirines) are two independent classes of compounds completely different in their physical and chemical properties. An interconversion of the linear and cyclic diazo compounds has not so far been possible. 

Diazirines are a reliable source of carbenes, and this property has dominated their application in the last decade. In particular, there has been considerable use of diazirines in macromolecular systems, both chemical and biological, and this is the subject of a recent review <2005SFM178>. Synthetic applications are documented in Section 1.11.6. 

The protonated diaziridine is more easily reducible than the diazirine, which has too weakly basic properties to be protonated in aqueous solution. In alkaline medium in which both are unprotonated, the diazirine is the more easily reducible. This explains why it has been difficult to obtain good yields of diaziridine by chemical and catalytic reduction of a diazirine if such a reduction is to result in a high yield of diaziridine, it must be performed in an alkaline medium. 

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