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We report a ruthenium-catalyzed (2 + 2) intramolecular cycloadclition of allenes and alkenes. We have found that the use of the ruthenium complex nH2Cl2(PiPr3)2., which has previously gone unnoticed in catalytic applications, is crucial for the observed reactivity. The reaction proceeds under mild conditions and is fully diastereoselective, providing a practical entry to a variety of bicydo[3.2.O]heptane skeletons featuring cyclobutane rings. [ABSTRACT FROM AUTHOR]

The article describes the [4+3] intramolecular cycloaddition of alkylidenecyclopropanes and dienes using a palladium catalyst. According to the authors, the cycloaddition reaction allows the synthesis of appealing, stereochemically rich 5,7-fused bicyclic systems from readily dienylidenecyclopropanes. They mention that the success of reaction is restricted to dienes blocked in a cisoid conformation and activated by the presence of electron-withdrawing substituents.