Dienamine-Induced Divinylcyclopropane-Cycloheptadiene Rearrangements

Abstract

Sigmatropic rearrangements constitute an important group of pericyclic reactions. In contrast to cycloaddition reactions, examples of catalytic variants of electrocyclic reactions and sigmatropic rearrangements are still scarce in the chemical literature. Herein, we report the first organocatalytic Cope rearrangement of in situ-generated divinylcyclopropanes. The reactive motif was generated by condensation of 4-(2-vinylcyclopropyl)but-2-enal derivatives with a secondary amine catalyst to form a transient dienamine. The cycloheptadiene products could be obtained in high yield and excellent diastereoselectivity. Importantly, the reaction was demonstrated to be stereospecific, proceeding under mild conditions, while exhibiting broad functional group tolerance.

Keywords: Cope rearrangement; cycloheptadienes; cyclopropanes; organocatalysis; pericyclic reactions.