A Michael Alternative to Cyclopentene Annulations

Abstract
Intramolecular cyclopentene annulations involving carbenoidmediated cyclopropanations (Eq. 1), followed by the nucleophilic ring opening of vinylcyclopropanes have been studied extensively2 and have been applied successfully to the synthesis of triquinane terpenes.3 More recently, intermolecular [2 + 3] annulations of enones (Eq. 2), have also been studied4 and applied in the synthesis of these terpenes.5