08 December 2009 - Fullerenes

quadrannulene  Circulenes are closed rings consisting of benzene rings. As of this month the smallest possible ring is no longer 5 but 4 thanks to research by a big multinational team headed by Benjamin King (University of Nevada, Reno) (Bhola et al. 2009 DOI). The compound on the right is called a quadrannulene in reference to corannulene. It was synthesized from the tetraalkyne on the left by cyclotrimerization with bistrimethylsilylacetylene followed by oxidation with the ferrocenecompound Cp2FePF6 in an irrelevant yield of 2%. The molecule is a geodesic polyarene and bowl shaped with the 4 double bonds radiating from the cyclobutane ring heavily pyramidalized although the compound itself is very stable (moderately air stable, stable up to 170 °C). Interestingly the carbon framework of this molecule can be found in the hypothetical octahedral 4,6-C24-fullerene.