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October 19, 2025The Journal of Organic Chemistry2 citations

How to Form Two Bonds in Three Ways: Reaction Trinity of σ,π-Heterosymmetric Diradicals

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HCHaonan ChengYZYun ZengXZXiaofan Zhang

Key Points

  • Three competing pathways for σ,π-heterosymmetric diradicals include hydrogen abstraction and nucleophilic interactions.
  • The σ-radical preferentially abstracts hydrogens, indicating its strong reactive nature in chemical environments.
  • Rearrangement into enyne-allene highlights the impact of electronegative groups on diradical formation.
  • The study combines experimental results with computational analysis to explore diradical reactions.

Abstract

σ,π-Heterosymmetric diradicals are typically formed through the Myers–Saito cyclization of enyne-allene, featuring distinct chemical environments for the two radicals. In this study, maleic hydrazide was introduced at the ene position of enediyne molecules, leveraging the electron-withdrawing properties of these groups to facilitate the rearrangement of enediyne into enyne-allene, which subsequently leads to the generation of σ,π-heterosymmetric diradicals through cycloaromatization. Based on experimental results and computational analysis, we identified three competing reaction pathways for σ,π-heterosymmetric diradicals: (1) hydrogen atom abstraction by diradicals, (2) interactions of π-radicals with nucleophiles, and (3) interactions of σ-radicals with nucleophiles. In path 1, both radical centers can readily abstract hydrogens, with the σ-radical, showing a clear preference. In paths 2 and 3, the distortion of the core aromatic ring during the nucleophilic reaction leads to the disruption of the orthogonality of the radical orbitals through the formation of a Möbius-like conjugated framework, providing an efficient pathway for electron transfer and thereby facilitating both diradical quenching and nucleophilic addition.

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Cite This Study

Cheng et al. (2025) studied this question.

synapsesocial.com/papers/68f43efb854d1061a58ac297https://doi.org/10.1021/acs.joc.5c01539
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