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

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 C60 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‐C61 methyl butyrate, which indicates that these new derivatives possess higher LUMO energy levels.

Phosphine Organocatalysis

“…After working with DMAD and fullerenes, Chuang further explored the reactivities of fullerenes with more elaborate alkyne systems in the presence of various phosphines . For ynoate–enoate systems, a formal [3 + 2] annulation occurred with fullerenes (Scheme ).…”

α(δ')-Michael Addition of Alkyl Amines to Dimethyl (E)-hex-2-en-4-ynedioate: Synthesis of α,β-Dehydroamino Acid Derivatives

“…It occurs through the zwitterionic carbenoid species formation by the attack of phosphine on the β-carbon of the allenoate substrates. In the case of the activated enyne substrate 2 , our group has reported the α-addition of phosphine and subsequent reactions of the resulting 1,3-dipolar species with various electrophilic substrates [26,27]. Although we observed the exclusive α-addition of phosphine to enyne 2 through product analysis, we still speculated about the possibility of nucleophilic addition to β-carbon of enyne 2 with other nucleophiles.…”

New frontiers in the transition-metal-free synthesis of heterocycles from alkynoates: an overview and current status

“…Scheme 100 illustrates the mechanistic pathway for the formation of product 389 in line with the literature precedents. [340][341][342][343] Addition of PPh 3 385 to hex-2-en-4-ynedioate 387 furnished 1,3-dipolar zwitterionic intermediate 394 followed by the addition to isatinylidene malononitrile 384 leading to the formation of adduct 395. Subsequently, an intramolecular Michael addition of the carbanion to the 1,3-diene holding a stronger electron-deficient triphenylphosphanyl cation afforded the cyclized intermediate 396.…”