STRUCTURE OF A RING ENLARGED PRODUCT FROM THE BASE-INDUCED REARRANGEMENT OF DIBROMOMETHYLENEBENZONORBORNENE

The base-catalyzed rearrangement reactions of 2-bromomethylenebenzonor bornene 8 and 2,2-dibromomethylenebenzonorbornene 9 were studied. Reac tion of 8 with potassium tert-butoxide in THF gave only the enol ether 11 whose formation is rationalized via a carbene-cycloalkyne mechanis m. However, treatment of 9 with phenyllithium in THF at 40 degrees C g ave the ring-enlarged dibromide 13 whose structure is reported herein. The ring-enlarged product 13 is rationalized in terms of carbanionic rearrangement. Quantum mechanical calculations are consistent with the se observations.