Photochemical generation of aziridinium imides: are Als bystanders or perpetrators in the ene reaction?

A non-equilibrating mixture of two aziridinium imides (AIs) resulting from the photoaddition of N-methyl-1,2,4-triazoline-3,5-dione and cycloheptene has been prepared. Warming the AIs produces only the product of the expected ene reaction with no back-reaction to starting materials. Even though one of the pair does not have the geometry necessary for hydrogen abstraction, both AIs disappear at essentially the same rate, showing that AIs cannot be the direct precursors of the ene product.