Helicenes, with their unique helical structures, have long captured the interest of synthetic chemists, not only as end products, but also as versatile platforms for further chemical transformations. However, transforming [6]helicene into planar coronene typically requires harsh conditions and poses significant challenges. Herein, we demonstrate that replacing the terminal benzene ring of [6]helicene with a thiophene ring enables its photochemical transformation into coronene. Sulfur oxidation of the thiophene ring enables the corresponding thermal transformation, and the terminal tetrafluorination of the opposite benzene ring further accelerates this process, yielding 1,2-difluorocoronene, as confirmed by X-ray crystallography. The transformation begins with an intramolecular Diels–Alder reaction, whose activation energy is significantly lowered by these structural changes. Our findings underscore the utility of strategic modifications such as sulfur oxidation and fluorination in promoting this "helix-to-disc" conversion and opening new avenues for synthesizing functional polycyclic aromatics.

中文翻译：

---

硫氧化和氟化促进硫杂[6]螺旋烯向晕烯的螺旋-盘转化


螺旋烯以其独特的螺旋结构，长期以来一直引起合成化学家的兴趣，不仅作为最终产品，而且作为进一步化学转化的多功能平台。然而，将[6]螺烯转化为平面晕苯通常需要苛刻的条件并带来重大挑战。在此，我们证明用噻吩环取代[6]螺烯的末端苯环使其能够光化学转化为晕苯。 X射线晶体学证实，噻吩环的硫氧化能够发生相应的热转变，而相反苯环的末端四氟化进一步加速了这一过程，产生1,2-二氟晕苯。该转变始于分子内狄尔斯-阿尔德反应，这些结构变化显着降低了其活化能。我们的研究结果强调了硫氧化和氟化等战略修饰在促进这种“螺旋到盘”转化并为合成功能性多环芳烃开辟新途径方面的效用。