Xanthene[n]arenes: Exceptionally Large, Bowl-Shaped Macrocyclic Building Blocks Suitable for Self-Assembly

A new class of macrocycles denoted as “xanthene­[n]­arenes” was synthesized. In contrast to most other macrocycles, they feature a conformationally restricted bowl shape due to the attached alkyl groups at the linking methylene units. This facilitates the synthesis of cavitands and the self-assembly to molecular capsules via noncovalent interactions. The derivatization potential of the novel macrocycles was demonstrated on the xanthene[3]­arene scaffold. Besides a deep cavitand and an oxygen-embedded zigzag hydrocarbon belt[12]­arene, a modified macrocycle was synthesized that self-assembles into a hydrogen-bonded tetrameric capsule, demonstrating the potential of xanthene­[n]­arenes as a new set of macrocyclic building blocks.