2Paracyclophanes (pCps) are rigid scaffolds consisting of two aromatic rings held in a cofacial arrangement by ethylene bridges. This distinctive geometry enforces through‐space π−π interactions, confers unusual reactivity, ensures configurational stability, and imparts planar chirality onto the systems. While functionalization of the aromatic rings is well‐established, selective modification of the ethylene bridges remains a major synthetic challenge. This review surveys current strategies for the preparation of bridge‐functionalized pCps, including construction of the cyclophane core from substituted precursors, direct derivatization of the parent scaffold, and functionalization of strained or deck‐substituted derivatives. Particular emphasis is placed on exploiting bridge reactivity to access novel molecular architectures, especially via contractive annulation approaches. Representative examples demonstrate how radical, photochemical, and stepwise transformations enable the installation of diverse substituents, the formation of π‐extended motifs at bridge positions, and the assembly of unprecedented strained polycyclic systems. Despite notable progress, challenges in yield, selectivity, and scalability remain, and enantiopure bridge‐functionalized 2.2pCps are still largely unexplored. Continued methodological development is therefore expected to expand the utility of pCps as versatile building blocks for advanced materials, organometallic ligands, and catalytic systems, positioning the bridge as a strategic platform for accessing new structural and functional possibilities in contemporary cyclophane chemistry.
Sun et al. (Sun,) studied this question.