Synthesis of dihydrotropone derivatives using an anionic 8π-electrocyclic reaction.

A new method to synthesise functionalised cycloheptatrienes was established using the anionic 8π-electrocyclic reaction of β-ketoester-derived dienyne substrates. The cyclised products were converted to a variety of cycloheptatriene derivatives including tropones. Using this method, a concise, first total synthesis of (-)-orobanone, a natural sesquiterpenoid, was achieved.