2H-Azirines from a concerted addition of alkylcarbenes to nitrile groups.

Photolysis of aziadamantanes in the presence of fumaronitrile (FN) unexpectedly afforded conjugated 2H-azirines resulting from addition of the carbene to the CN triple bond. This represents the first example of a direct azirine formation starting from an alkylcarbene for which a concerted pathway is postulated. The novel outcome of the reaction is favored by the prior formation of a carbene-alkene complex, a type of adduct that only recently has been described.