卤代羰基叶立德:“推-拉”稳定作用对四苯基环戊二烯酮与卡宾的脱氧反应的影响(英文)

Halocarbonyl Ylide: the Effect of “Push-Pull”Stabilization on Deoxygenation of Tetraphenylcyclopentadienone in Carbene Reaction

研究了四苯基环戊二烯酮与三溴甲基苯基汞（二溴卡宾的前体化合物）的卡宾反应，发现该反应可给出比通常有立体障碍的酮要高得多的脱氧（以脱CO的形式）产率．本文从羰基叶立德中间体的“推-拉”稳定作用以及该中间体的构象和电子分布的角度出发，并结合产物分析对这一反常现象进行了讨论，发现在潜芳香结构的羰基化合物与二卤卡宾的反应中，有可能由于“推-拉”作用形成具有芳香结构的羰基是中间体，该中间体由于正负电荷及以较好的分散以及其接近0°／90°型的构象，有效地阻碍了分子间环加成和分子内电环化这两个竞争反应的进行，从而使脱氧途径成为该反应的主渠道．本项研究进一步揭示了一些尚未被人了解的反应规律，合理地解释了反应机理．

An unexpectedly high yield of carbon monooxide as a deoxygenationproduct of carbonyl compound was obtained in the reaction of tetraphenyl-cyclopentadienone with dibromocarbene using phenyl tribromomethyl mercury asthe carbene precursor. This unique phenomenon is rationalized in terms of thepush-pull stabilization gained from the interaction between the partially aromaticcyclopentadienide moiety and the positively charged dibromomethylene moiety inthe dihalocarbonyl Ylide-like transition state.