Selective Electrochemical Retro‐Cycloaddition Reaction of Pyrrolidinofullerenes

Abstract

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).

Mass Spectrometry Studies of the Retro-Cycloaddition Reaction of Pyrrolidino and 2-Pyrazolinofullerene Derivatives Under Negative ESI Conditions

“…The stabilization in the eliminated azomethine ylide, specially produced by the electronwithdrawing character of the methoxycarbonyl group on the C2 position of the pyrrolidine ring (Compound 6), accelerates the thermal reaction. The results obtained from the electrochemical reactions of pyrrolidinofullerenes indicate that these compounds are unstable towards electro- chemical oxidation undergoing easily a retro-cycloaddition process [47]. We can conclude that the retro-cycloaddition reaction in N-H pyrrolidinofullerenes takes place either by thermal or oxidative reactions or under spectrometric conditions, affording similar results.…”

“…The CO extrusion forms a N-alkyl derivative which can undergo a further retrocycloaddition either under thermal [36] or under mass spectrometry conditions. The difference of thermal reactivity between N-acyl and N-alkylpyrrolidinofullerenes is so remarkable that they could find synthetic usefulness in the selective preservation of N-benzoyl derivatives in the presence of N-alkylpyrrolidines, provided that benzoylation of these rings is a reversible reaction [47]. The cycloreversion of N-alkylpyrrolidinofullerenes is easily achieved not only by heating but also under microwave irradiation or using ionic liquid phases in quantitative yield [48].…”

Chemical, Electrochemical, and Structural Properties of Endohedral Metallofullerenes

“…While the second wave is similar to the first oxidation wave of the nonderivatized Er 3 N@C 80 , the first oxidation was addend-based and led to the removal of the addend from the carbon sphere. [148] The [5,6] derivative exhibited very similar anodic behavior, but showed a contrasting cathodic behavior with three reversible reduction waves. Remarkably the [5,6] (Table 9).…”

“…The oxidation of Sc 3 N@C 80 -(Mes 2 Si) 2 CH 2 led to the removal of the addend from the carbon cage, as in the case of pyrrolidino adducts of C 60 and Sc 3 N@C 80 . [148] Interestingly, the redox potentials of these compounds directly reflected the electronic properties of the addend. The highly electron accepting fluorine atoms shifted the first oxidation and first reduction towards more anodic potentials, whereas the electron-donating silicon atoms shifted the first reduction potential to more negative potentials.…”

“…The ferrocenyl pyrrolidine based oxidations were found to be irreversible, a probable consequence of the electrochemical retrocycloaddition. [148] The redox potentials measured for these compounds are reported in Table 11.…”