Fullerene C70 as Photoredox Catalyst for the Synthesis of Pyrrolo[2,1‑a]isoquinolines via 1,3‐Dipolar Cycloaddition‐Aromatization Sequence

Herein, we introduce fullerene (C70) as an effective photoredox catalyst for the construction of a highly functionalised pyrrolo[2,1-a]isoquinoline framework via 1,3-dipolar cycloaddition-aromatisation reaction sequence. The ability of C70 to efficiently harvest visible light, its long-triplet state lifetime, good photostability, and strong singlet oxygen generation potential (Ф≈1), make it an efficient photoredox catalyst. Upon photoirradiation, C70 promotes the formation of singlet oxygen and superoxide radical via energy transfer (EnT) and single electron transfer (SET) mechanism, which acts as a potential oxidant in the formation of azomethine ylide through the oxidation-deprotonation tandem process, which further participates in [3 + 2]-cycloaddition reaction protocol with alkene/alkyne to give the corresponding pyrrolo[2,1-a]isoquinolines. Interestingly, this protocol allows the activation of a wide range of substrates giving access to a diverse library of 48 well-decorated pyrrolo[2,1-a]isoquinolines with good functional group tolerance.