A highly efficient and convergent approach for the synthesis of octalone 1, the focal intermediate for the synthesis of several sesquiterpenoids, was developed based on the cationic cyclization strategy of the functionalized oxabicyclic template 5. A highly efficient and convergent approach for the synthesis of octalone 1, the focal intermediate for the synthesis of several sesquiterpenoids, was developed based on the cationic cyclization strategy of the functionalized oxabicyclic template 5.