Sustainable Synthesis of 4,7-Dihydro-4,7-ethano-2H-isoindoles—Key Building Blocks to Benzoporphyrins

Chem. Eur. J.  2026, e70979.

Benzoporphyrins, π extended porphyrin analogues, exhibit remarkable potential for optoelectronic and theragnostic applications, yet have remained largely confined to fundamental studies owing to the challenging synthesis of masked isoindole precursors. Here, we report a concise, scalable three-step synthesis of 4,7-dihydro-4,7-ethano-2H-isoindole, a key building block of the benzoporphyrin framework. Subsequent functionalization affords the corresponding α-ester derivative, enabling controlled access to diverse, lower-symmetry benzoporphyrin architectures. Compared with previous multistep strategies, this scalable route markedly reduces cost, waste generation, and synthetic complexity, representing the most practical synthetic approach to date. This advance enhances the synthetic accessibility of benzoporphyrins and paves the way for their broader implementation in molecular materials and biomedical applications.