Recent Advances in Catalytic Asymmetric Transformations of Bicyclobutane: A Versatile Building Block for Enantiopure Bioisosteric Molecules

Bridged bicyclic scaffolds such as bicyclo[2.1.1]hexanes (BCHs) and bicyclo[3.1.1]heptanes (BCHeps) have emerged as valuable bioisosteres for ortho- and meta-substituted arenes in contemporary drug design. These three-dimensional frameworks offer enhanced conformational rigidity and superior physicochemical properties compared to their planar aromatic counterparts. The precise control of stereochemistry in these scaffolds is paramount, as chirality profoundly influences biological activity and pharmacokinetic profiles. Strain-release transformations of bicyclo[1.1.0]butanes (BCBs) represent particularly efficient and atom-economical synthetic approaches to access these architectures. Despite significant advances in this field, catalytic asymmetric methodologies employing BCBs remain notably underdeveloped. This perspective highlights recent breakthroughs in asymmetric transformations of BCBs, with particular emphasis on innovative stereoselective catalytic strategies. We systematically analyze emerging chiral catalyst systems and unique activation modes that enable precise enantiocontrol in BCB functionalization, highlighting their potential applications in medicinal chemistry.