Isolation and Characterization of Unsymmetrical C<INF>60</INF>Me<INF>5</INF>O<INF>3</INF>H, a Cage-Opened Bisepoxide Ketone:  Tautomerism Involving a Fullerene Cage Bond

<UFIGR ID="ol0100531n00001">Bisepoxide ketone C<INF>60</INF>Me<INF>5</INF>O<INF>3</INF>H, possessing a nine-membered hole in the cage, has been isolated from the reaction of C<INF>60</INF>Cl<INF>6</INF> with methyllithium followed by hydrolysis. It is a tautomer of the recently isolated bisepoxide fullerenol, this tautomerism being the first example involving a cage C−C bond, and may be driven by cage strain. Like the fullerenol, the ketone gives a high C<INF>58</INF>⁺ fragmentation ion intensity during EI mass spectrometry.