Heterocirculenes: synthetic progress and intrinsic properties
In this Feature Article, we summarize the synthetic progress of heterocirculenes, focusing on their structures and intrinsic properties. Various heterocirculenes have been synthesized to date, of which structural features are categorized on the basis of the numbers of annulated pentagons. From the viewpoint of key steps, the synthetic routes are classified into two methodologies, the annulative construction of the central eight-membered ring and the ring fusion of eight-membered ring precursors. Electronic and photophysical properties based on the structural features and the introduced heteroatoms of heterocirculenes are also described.