Expansion and contraction: Shaping the porphyrin boundary via diradical reactivity

► Approach to periphery modification centered on the application of diradicals generated through unique diyne-ene and diazo-keto functionalization at the β,β′-position of the macrocycle. ► Diradical adds across the adjacent phenyl rings of the meso-positions to extend the aromaticity across three rings. ► Dione or diazo-keto functionalization and subsequent reaction with nucleophiles in the presence of Ag+, generates acetals that lead to modified chemical properties additional reactivity potential at the periphery - diazoketochlorin photolysis leads to rapid N2 extrusion and initial carbene formation. ► Wolff ring-contracted ketene, is detectable, demonstrating that the out-of-plane electronic configuration is initially generated and reacts to give the nucleophile-quenched species, as well as relaxing to form exocyclic ring addition and other radical-based products. ► Synthetic opportunities to markedly modulate macrocycle electronic structure in a highly asymmetric manner to form truly distinct porphyrinoid constructs.