Transition states of the retro-ene reactions of allylic diazenes.

[reaction: see text] Density functional theory studies of intramolecular retro-ene reactions of allyldiazenes show that the reaction is a concerted process involving a six-center cyclic transition state. The activation barriers for deazetization for X = H, Me, F, Cl, and Br (3a-e) are 2.4, 40.2, 22.3, 9.3, and 8.8 kcal/mol, respectively.