FRAGMENTS OF FULLERENES - NOVEL SYNTHESES, STRUCTURES AND REACTIONS

The utility of high-temperature gas-phase cyclization reactions for co nstructing bowl-shaped polycyclic aromatic hydrocarbons related to C-6 0 was first demonstrated by our simple synthesis of corannulene, 1. Th is strategy has subsequently been extended to the preparation of large r fullerene fragments and promises to play a central role in future sy ntheses of even more spectacular molecular bowls, baskets and tubes. I somerization reactions of benzenoid hydrocarbons at high temperatures in the gas phase have also been studied and are now known to occur by reversible benzene ring contractions to fulvene intermediates. The rel ationship of these small molecule rearrangements to the mechanisms of fullerene production and isomerization (''annealing'') is discussed. F inally, the conversion of simple benzenoid hydrocarbons to fragments o f fullerenes containing five-membered rings with two hydrogens fewer i s shown to be a common high-temperature reaction of bay region polycyc lic aromatic compounds, and a preliminary mechanistic proposal is offe red along with supporting experimental evidence.