Recent Progress in (3+3) Cycloadditions of Bicyclobutanes to Access Bicyclo[3.1.1]heptane Derivatives

Abstract The synthesis of bicyclo[3.1.1]heptane (BCHeps) derivatives, which serve as three-dimensional (3D) bioisosteres of benzenes and are the core skeleton of several terpene natural products, is garnering growing interest. The (3+3) cycloadditions of bicyclobutanes (BCBs) represent an attractive method for efficiently accessing (hetero)BCHep skeletons with 100% atom economy. Herein, we give a brief summary of recent achievements in this approach for the synthesis of diverse BCHep derivatives, emphasizing our recent progress in the initial palladium-catalyzed (3+3) cycloadditions of bicyclobutanes with vinyl oxiranes. 1 Introduction 2 Radical (3+3) Cycloaddition Reaction 3 Polar (3+3) Cycloaddition Reaction 4 Palladium-Catalyzed Enantioselective (3+3) Cycloaddition Reaction 5 Conclusion