Bicyclopentene addend on fullerene: epoxidation and cis-bromine addition
Bromine adds cis to the double bond in the addend of the fullerene–cyclopentadiene adduct, so that both bromines are directed away from the cage. The epoxide, formed by peracetic acid oxidation of the double bond of the addend, also points away from the cage. These results are attributed to a combination of steric hindrance and polar repulsion by the fullerene cage, the first time such effects have been reported to control addition. The epoxide appears to extrude CO during mass spectrometry to give a cyclobutane derivative of fullerene.