Synthesis of Benzo[a]fluorene, Benzo[c]fluorene, and Benzo[j]fluoranthene via a Lewis Acid‐Catalyzed Prins‐Type Cycloaromatization: Application to the Total Synthesis of Viridistratin A

Abstract

Synthesis of benzo[a]fluorene, benzo[c]fluorene, and benzo[j]fluoranthene have been accomplished from readily accessible enol ether precursors via a Lewis acid‐catalyzed Prins‐type cycloaromatization. Mechanistically, it was proposed that Lewis acids catalyze the generation of oxonium species, which accelerate subsequent annulation and aromatization. This protocol offers the benefit of an operationally simple, transition‐metal‐free, and air‐tolerant reaction condition, enabling gram‐scale syntheses of the desired products. The total synthesis of viridistratin A further supported this synthetic strategy for establishing polycyclic aromatic hydrocarbon architectures.