Lewis Acid Catalyzed Formal Intramolecular [3 + 3] Cross-Cycloaddition of Cyclopropane 1,1-Diesters for Construction of Benzobicyclo[2.2.2]octane Skeletons

A novel Lewis acid catalyzed formal intramolecular [3 + 3] cross-cycloaddition (IMCC) of cyclopropane 1,1-diesters has been successfully developed. This supplies an efficient and conceptually new strategy for construction of bridged bicyclo[2.2.2]­octane skeletons. This [3 + 3]­IMCC could be run up to gram scale and from easily prepared starting materials. This [3 + 3]­IMCC, together with our previously reported [3 + 2]­IMCC strategy, can afford either the bicyclo[2.2.2]­octane or bicyclo[3.2.1]­octane skeletons from the similar starting materials by regulating the substituents on vinyl group.