A novel photorearrangement of a cyclohexadiene derivative of C60.

[reaction: see text] Photorearrangement of tetraalkoxycarbonyl-substituted cyclohexadiene derivatives of C(60) yields not only well-known bis(fulleroid) but also bis(methano)fullerene. Existence of a labile and structurally new intermediate is observed in the reaction mixture. The discovery of the compound suggests the existence of another possible pathway giving those two products other than the widely accepted [4 + 4]/[2 + 2 + 2] mechanism.