The rearrangement of 2-(1,6-methano[10]annulenyl)-3,3-dimethylmethylenecyclopropane: A computational study

A detailed theoretical study on the rearrangement of 2-(1,6-methano[10]annulenyl)-3,3-dimethylmethylenecyclopropane 1 to a mixture of two diastereomeric 1,6-methano[10]annulenylisopropylidenecyclopropanes, 3 and 5, is presented in this paper. The computational results reproduce experimental findings and confirm the conjecture that the rearrangement proceeds through the biradical intermediate 2, which is greatly stabilized by the 1,6-methano[10]annulenyl group and is long-lived enough to undergo a rotation before ring closure. In addition, the origin of the stereochemistry observed in the rearrangement has been discussed.