All things retro: Pyrrolidinofullerenes undergo a retro‐cycloaddition reaction to afford the corresponding fullerene (C60, C70, or an endohedral C80 metallofullerene; see scheme) in quantitative yield upon treatment with an excess of a dipolarophile (maleic anhydride or N‐phenylmaleimide) in o‐dichlorobenzene. The reaction works efficiently with higher fullerenes and has allowed the isolation of one of the constitutional isomers of Sc3N@C80.

Unprecedented reactions involving the highly reactive double bonds of the fullerene sphere undergoing cobalt-catalyzed [2+2+1], thermally induced [2+2], and ene cycloadditions have been researched in a systematic way. In addition, the highly efficient retro-cycloaddition processes of fulleropyrrolidines (Prato cycloadducts) and fulleroisoxazolines are also discussed in detail. These new reactions in fullerene chemistry reveal that the unique scenario presented by the convex and highly reactive surface in fullerenes has not yet been appropriately exploited, and that it is still possible to create new and fascinating structures.

Isoxazolino[4,5:1,2][60]- and -[70]fullerenes undergo an efficient retro-cycloaddition reaction to pristine fullerene by thermal treatment in the presence of an excess of a dienophile and Cu(II) catalysis, which can be selectively used in the presence of malonate or pyrrolidine cycloadducts. Trapping experiments using N-phenylmaleimide as dipolarophile have shown that the reaction mechanism occurs by thermal removal of the nitrile oxide 1,3-dipole, in a process which is favored by the presence of Cu(II) as the catalyst. The ESI-MS study supports the observed retro-cycloaddition process for both C60 and C70 derivatives. In contrast to previous electrochemical retro-cycloaddition processes observed in fulleropyrrolidines, isoxazolinofullerenes were stable under oxidative conditions.

Going retro: Controlled‐potential electrolysis (CPE) is employed as a synthetic tool in the selective removal of addends from fullerene adducts. Reductive CPE has been extensively used in the retro‐cyclopropanation of fullerenes without affecting pyrrolidine addends also present. Now oxidative CPE for the selective removal of pyrrolidine addends in the presence of methano adducts is reported (see scheme).

Im Rückwärtsgang: Potentialgesteuerte Elektrolyse (CPE) dient als Methode für das selektive Entfernen von Addenden aus Fullerenaddukten. Reduktive CPE wurde bereits vielfach zur Retro‐Cyclopropanierung von Fullerenen genutzt, ohne dass Pyrrolidinaddenden beeinflusst wurden. Jetzt wird die oxidative CPE zum selektiven Entfernen von Pyrrolidinaddenden in Gegenwart von Methanoaddukten vorgestellt (siehe Schema).