Synthesis of C60(O)3: an open-cage fullerene with a ketolactone moiety on the orifice.

Four isomers are currently known for the trioxygenated fullerene derivative C(60)(O)(3), three regioisomers with all of the oxygen addends as epoxy groups and the unstable ozonide isomer with a 1,2,3-trioxlane ring. Here we report the synthesis of an open-cage isomer for C(60)(O)(3) with a ketolactone moiety embedded into the fullerene skeleton through a three-step procedure mediated by fullerene peroxide chemistry. Two fullerene skeleton carbon-carbon bonds are cleaved in the process. The open-cage derivative C(60)(O)(3) can be converted back to C(60) through deoxygenation with PPh(3). Single crystal X-ray structure confirmed the open-cage structure.