Stepwise and Cascade Synthesis of 9,10‐Diaroylphenanthrenes From Tetraarylthiophenes by Electronically Guided Bond Making and Breaking Under a Scholl‐Type Reaction

The Scholl reaction has long stood as a powerful tool for forging C-C bonds in polycyclic aromatic hydrocarbons (PAHs) yet controlling regioselectivity and accessing new reactivity remains a formidable challenge. Here, we unveil a strategically designed platform that exploits electronic tuning within tetraarylthiophenes (TATs) to achieve highly selective [c]-face oxidative cyclodehydrogenation, delivering phenanthro[9,10-c]thiophenes in exceptional yields, a pathway previously inaccessible. Beyond annulation, we uncover a novel oxidative ring-opening reaction, wherein these phenanthrothiophenes undergo selective C─S bond cleavage to yield 9,10-diaroylphenanthrenes-a transformation unprecedented in thiophene chemistry under Scholl-type reaction. Remarkably, we integrate both steps into a one-pot cascade protocol, streamlining direct synthesis from TATs to complex diketone architectures in notable yields. Mechanistic studies, including radical trapping and EPR spectroscopy, point out toward radical (cation/anion) pathways governing these transformations. This dual reactivity-from ring construction to ring cleavage-spotlights new horizons in Scholl chemistry, expanding synthetic access to diverse PAH frameworks and edition of functional edges, that may have potential applications as functional materials in organic electronics.