Expanding the Corannulene Surface

Corannulene is the simplest example within the class of polynuclear aromatic compounds with curved surfaces that are related by carbon framework to the i fullerenes. These aromatic hydrocarbons possess bowl-shaped geometries, consist 

A C2gH,4 hydrocarbon was recently prepared, also by flash vacuum pyrolysis. This interesting reaction, which may involve a benzyne type intermediate, represents the first synthesis of a benzocorannulene.  

Although there are a number of Cjq hydrocarbons, those of greatest interest will be the ones that possess relatively high symmetry (27-29). And despite considerable interest in their synthesis, semibuckminsterfullerenes remained elusive until recently. 

As would be expected, semibuckminsterfiillerene 27 is predicted to adopt a bowl-shaped conformation by ab initio 3-21G calculations. However, while 27 is a fascinating compound, it does not represent a symmetrical half of the buckmin-sterfullerene surface. That is, when the carbon framework of 27 is removed from 

As with corannulene, conventional routes for the preparation of 28 have been unsuccessful, due no doubt to the strain associated with this molecule nevertheless. 

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