Vinylcyclopropanes as All-Carbon 1,5-Dipoles: A Reactivity Switch for Palladium-Catalyzed (5 + 4) Cycloadditions.

Azonanes were prepared by a palladium-catalyzed (5 + 4) cycloaddition between activated vinylcyclopropanes and 1-azadienes. During this process, the vinylcyclopropane partner displayed an unusual reactivity and behaved as an all-carbon 1,5-dipole. A N,N-bidentate ligand was required to inhibit the formation of thermodynamic (3 + 2) cycloadducts.