Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune-411008, Maharashtra (India).
Angew Chem Int Ed Engl. 2014 Jun 23;53(26):6678-82. doi: 10.1002/anie.201403372. Epub 2014 May 14.
32π-Antiaromatic expanded isophlorins with a varying number of thiophene and furan rings adopt either planar, ring-inverted, or twisted conformations depending on the number of furan rings in the macrocycle. However, they exhibit identical reactivity with respect to their oxidation to aromatic 30π-dicationic species under acidic conditions. These 32π-antiaromatic macrocycles can also be oxidized with [Et3O(+)SbCl6(-)] and NOBF4 to generate dications, thus confirming ring oxidation of macrocycles. Furthermore, they can be reduced back to their parent 32π-antiaromatic state by triethylamine, Zn, or FeCl2. Single-crystal X-ray diffraction analysis confirmed a figure-eight conformation for a hexafuran system, which opens to a planar structure upon oxidation.
32π-反芳香扩环异紫檀素具有不同数目的噻吩和呋喃环，根据大环中环呋喃的数量，它们可以采取平面、环倒位或扭曲构象。然而，在酸性条件下，它们在氧化为芳香 30π-二阳离子物种方面表现出相同的反应性。这些 32π-反芳香大环也可以被[Et3O(+)SbCl6(-)]和 NOBF4 氧化生成二阳离子，从而证实了大环的环氧化。此外，它们可以通过三乙胺、Zn 或 FeCl2 还原回其母体 32π-反芳香状态。单晶 X 射线衍射分析证实了六呋喃体系的八字形构象，该构象在氧化时打开为平面结构。
