Nonradical Reactions of p-Benzyne Diradicals.

Enediynes undergo electrocyclization to p-benzyne diradicals. Although such diradicals ordinarily react by radical pathways, they can also be trapped by nucleophilic addition, a pathway supported by computations. The product of that addition is a "naked" aryl anion that is unselective toward protonation. A cyclohexeno-substituted enediyne was synthesized and found to be more amenable to further derivatization and mechanistic study. Moreover, it was shown to undergo automerization, rearrangement to a degenerate form of the original enediyne.