Aromatic compounds Bergman cyclization

The main use of this reaction is for the synthesis of bowl-shaped polycyclic aromatic hydrocarbons and fullerenes [325], Exploring the boundaries of these reactions resulted in the synthesis of compounds of different geometry, tt-electron structure, aromaticity, and with the presence of heteroatoms [324]. Various cross-conjugated enediynes exert anionic cycloaromatization to form fulvene and fulvalene anions and even heterocycles. In accordance with the concept of aromaticity, the anionic Bergman type cyclization is preferred to the classical Bergman cycloaromatization of linear enediynes. This anionic cyclization differs considerably from the classical Bergman cyclization and related cycliza-tions, as well as from other dianionic cyclizations [326]. 

Aral et al. investigated the photochemistry of the linear shaped aromatic enediynes (186) and (187). The quantum yield of both ( )- (Z) and (Z) ( ) isomerizations considerably decreased in (186) and (187) because of an increase in the number of photochemical processes that yielded nonfluorescent excited species. The compound (188) showed characteristic charge-transfer absorption due to the strong donor-acceptor chromo-phores. The enediynes (189) on Au nanoparticles underwent Bergman-type cyclization leading to a polymerized coating via biradical intermediates. 

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