Reaction of tropone hydrazones with heterocumulenes such as isocyanate,ketene, and sulfene

Tropone benzoyl- and tosylhydrazones underwent the [8+2] cycloaddition reaction with isocyanates to afford the cyclohepta[d]imidazolin-2-one derivatives. This means that these hydrazones behaved as 8-amino-8-azaheptafulvenes. Also, the tropone hydrazones reacted with phenylketene and phenylsulfene in more complicated manners.