A Chiral Dicationic [8]Circulenoid: Photochemical Origin and Facile Thermal Conversion into a Helicene Congener
Abstrakt
Circulene-like species has been transformed, for the first time, into its helical counterpart by exclusive application of heat. Synthesis, structure, and properties of the chiral dicationic [8]circulenoid are reported.
The presented results are significant from several further perspectives: 1) no nitrogen-based cationic circulene compound has been reported before; 2) a rare saddle-shaped circulene system with order higher than [7] is presented; 3) the synthetic sequence leading to the chiral [8]circulenoid 1 based on the key [6+6] photocycloaddition is particularly succinct as it requires only five synthetic steps and no chromatographic purification. In this context, it is notable that photochemical strategies towards circulenes have remained overlooked so far.