Facile Access to Cyclopentadienes via Catalytic Intramolecular Palladium-Ene Reaction of 2,4-Pentadienyl Acetates

Abstract

We have recently disclosed a palladium-catalyzed Trost–­Oppolzer type Alder-ene reaction of 2,4-pentadienyl acetates for the synthesis of highly substituted cyclopentadienes and cyclopentene-fused aromatics. The overall transformation also represents an acid-free iso-Nazarov type cyclization. Herein, we provide the hypothesis and ­rationale behind this work, while highlighting the seminal contributions of Trost, Oppolzer and others towards the development of the palladium-ene reaction.