Approach to Seven-Membered Carbocycles via a Lewis Acid Catalyzed Intramolecular Michael Addition of Allenone.

A straightforward strategy for constructing seven-membered carbocycles by employing a Lewis acid catalyzed intramolecular Michael addition of allenones is reported. It offers atom-economic access to synthetically important furan-fused bi- or tricyclic frameworks containing seven-membered carbocycles, which are widely found in natural products possessing various bioactivities. A number of seven-membered carbocycle-containing polycyclic frameworks bearing diverse functional groups were prepared in good to excellent yields. Furthermore, the application potential of this strategy was exemplified by the construction of the key skeletons of Caribenol A and Frondosin B.