Radical Cation Cycloadditions of 2H-Azirines. Mechanistic Studies Concerning the Intermediate Radical Cation

Article abstract of DOI:10.1021/jo00068a048

The product of the ring opening of 3-aryl-substituted azirines under conditions of photoinduced electron transfer (PET) is shown to be not a nitrile ylide but a short-lived 2-azaallenyl radical cation.This species has been investigated by pulse radiolysis and γ-radiolysis techniques.The radical cation has an absorption band with λ_max at 485 nm.The lifetime of the radical cation is τ = 1.43 μs in n-butyl chloride.The rate constant for the reaction of the radical cation with the imine 9 is 7.8 x 10⁹ M^-1 s^-1. γ-Radiolysis in n-butyl chloride leads to the same products, i.e., an N-alkylated imidazole as in the case of PET.