Evidence for the Cyclic CN2 Carbene in Solution

Diazirinylidene (c-CN2) is formally the simplest of the N-heterocyclic carbenes. The intermediacy of this elusive species in the fragmentation of butyl 3-bromodiazirine-3-car­box­ylate (1a) with pent-4-en-1-ols and their sodium alkoxides in DMF is supported by the formation of 2-oxa­bicyclo­[4.1.0]­heptanes and di­pen­tenoxy­methanes. These products result from an intramolecular [2 + 1] cycloaddition and O–H insertion, respectively, of penten­oxy­methyl­enes suggested to originate from the reaction of the electrophilic c-CN2 with an alkoxide ion. The reaction of 1a with primary or secondary amines in methanol affords the corresponding 3-bromo­diazirine-3-carbox­amides.