[3+2] Cycloaddition of Dialkyl (<i>E</i>)‐Hex‐2‐en‐4‐ynedioates to [60]Fullerene by Phosphane‐Promoted Tandem α(δ′)‐Michael Additions

Abstract

Abstract Organophosphanes promote the [3+2] cycloaddition reactions of dialkyl ( E )‐hex‐2‐en‐4‐ynedioates and [60]fullerene, giving a series of cyclopenteno‐fullerenes 3a – k bearing phosphorus ylides. This cycloaddition reaction is initiated by the attack of nucleophilic phosphanes at the α(δ′)‐C atom of the dialkyl ( E )‐hex‐2‐en‐4‐ynedioate, which generates a 1,3‐dipolar species. These 1,3‐dipoles then react with C 60 followed by intramolecular cyclization to give cyclopenteno‐fullerenes in moderate‐to‐good yields. In a cyclic voltmmetry study, these novel fullerenes show a larger cathodic shift in their first reduction potential relative to [6,6]phenyl‐C 61 methyl butyrate, which indicates that these new derivatives possess higher LUMO energy levels.