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Nucleophilic Addition to Diradicals Derived From Cycloaromatization of Maleimide‐Based Enediynes
Author(s) -
Zhang Mengsi,
Ma Hailong,
Li Baojun,
Sun Ke,
Lu Haotian,
Wang Wenbo,
Cheng Xiaoyu,
Li Xiaoxuan,
Ding Yun,
Hu Aiguo
Publication year - 2021
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.202100136
Subject(s) - diradical , chemistry , zwitterion , reactivity (psychology) , nucleophile , allene , stereochemistry , maleimide , computational chemistry , protonation , photochemistry , organic chemistry , molecule , singlet state , catalysis , medicine , ion , physics , alternative medicine , pathology , nuclear physics , excited state
Diradical chemistry, typified by the cycloaromatization of enediynes or enyne‐allenes, have been extensively explored due to the involved intriguing biological activity and unique mechanistic actions. Because of the essential Myers‐Saito cycloaromatization involved in the maleimide‐assisted rearrangement and cycloaromatization (MARACA) mechanism disclosed in our recent work, the important object of diradical/zwitterion dichotomy and the reactivity of thermally induced σ,π‐diradicals were investigated in this work through the combination of experimental and computational studies. Deuterium incorporation experiments demonstrated that the polar product was afforded from the MARACA strategy, in which the diradical and zwitterion reactivities from the cycloaromatization step could both lead to the closed‐shell product via the subsequent nucleophilic addition reaction and protonation. Using the density functional theory calculations, the unusual reactivity of the heterosymmetric diradicals to closed‐shell zwitterions was examined, and the addition of carbonyl moiety to α,3‐dehydrotoluene was allowed to occur via a nonplanar cyclic allene transition structure with a small barrier of 9.1 kcal/mol. The observed nonplanar geometry is essential for the necessarily symmetry‐breaking action, resulted in the continuous transformation from open‐shell diradical to closed‐shell zwitterion species during the addition process.