He Chao, Thomas Aaron M, Galimova Galiya R, Morozov Alexander N, Mebel Alexander M, Kaiser Ralf I
Department of Chemistry , University of Hawai'i at Manoa , Honolulu , Hawaii 96822 , United States.
Department of Chemistry and Biochemistry , Florida International University , Miami , Florida 33199 , United States.
J Am Chem Soc. 2020 Feb 12;142(6):3205-3213. doi: 10.1021/jacs.9b13269. Epub 2020 Jan 30.
The fulvenallene molecule (CH) has been synthesized via the elementary gas-phase reaction of the methylidyne radical (CH) with the benzene molecule (CH) on the doublet CH surface under single collision conditions. The barrier-less route to the cyclic fulvenallene molecule involves the addition of the methylidyne radical to the π-electron density of benzene leading eventually to a Jahn-Teller distorted tropyl (CH) radical intermediate and exotic ring opening-ring contraction sequences terminated by atomic hydrogen elimination. The methylidyne-benzene system represents a benchmark to probe the outcome of the elementary reaction of the simplest hydrocarbon radical-methylidyne-with the prototype of a closed-shell aromatic molecule-benzene-yielding nonbenzenoid fulvenallene. Combined with electronic structure and statistical calculations, this bimolecular reaction sheds light on the unusual reaction dynamics of Hückel aromatic systems and remarkable (polycyclic) reaction intermediates, which cannot be studied via classical organic, synthetic methods, thus opening up a versatile path to access this previously largely obscure class of fulvenallenes.
在单碰撞条件下，通过亚甲基自由基（CH）与苯分子（CH）在二重态CH表面上的基元气相反应合成了富烯丙二烯分子（CH）。生成环状富烯丙二烯分子的无势垒途径涉及亚甲基自由基加成到苯的π电子密度上，最终导致一个 Jahn-Teller 畸变的环庚三烯基（CH）自由基中间体以及通过氢原子消除终止的奇特的开环-闭环序列。亚甲基-苯体系是一个基准，用于探究最简单的烃基自由基——亚甲基与闭壳层芳香分子的原型——苯发生基元反应生成非苯型富烯丙二烯的反应结果。结合电子结构和统计计算，这个双分子反应揭示了休克尔芳香体系不同寻常的反应动力学以及非凡的（多环）反应中间体，而这些是无法通过传统有机合成方法进行研究的，从而开辟了一条通用途径来获取这类此前很大程度上尚不明确的富烯丙二烯。
