Hydrogen atom abstraction by radical cations. The reactions of 9-substituted acridine radical cations with cyclohexa-1,4-diene†
摘要:
9-取代的吖啶基阳离子在二氯甲烷-Bu4NPF6(0.2 M)中与环己-1,4-二烯发生了简便的氢原子抽取反应。衍生物循环伏安法研究了反应的动力学,观察到反应符合 EC 机制(电荷转移后发生不可逆的一阶反应)。反应产物是质子化的吖啶底物和环己-1,4-二烯的二聚底物加合物。对 9-苯基吖啶和 9-苯基蒽自由基阳离子的反应进行了比较。前者会迅速抽取氢原子,而后者则会在没有亲核物的情况下缓慢二聚。研究表明,氮的 p 轨道上奇数电子的定位赋予了自由基阳离子的取氢活性。由于芳香环碳原子上没有自由 p 轨道,因此在炔自由基阳离子中观察不到氢原子抽取反应途径。
Hydrogen atom abstraction by radical cations. The reactions of 9-substituted acridine radical cations with cyclohexa-1,4-diene†
作者:Kishan L. Handoo、Jin-Pei Cheng、Vernon D. Parker
DOI:10.1039/b102285g
日期:——
9-Substituted acridine radical cations undergo facile hydrogen atom abstraction reactions with cyclohexa-1,4-diene in dichloromethane–Bu4NPF6 (0.2 M). The kinetics of the reaction were studied by derivative cyclic voltammetry and observed to conform to the EC mechanism (charge transfer followed by irreversible first-order reaction). The products of the reactions are the protonated acridine substrate and dimer–substrate adducts of cyclohexa-1,4-diene. A comparison is made between the reactions of 9-phenylacridine and 9-phenylanthracene radical cations. The former undergoes rapid hydrogen atom abstractions, while the latter slowly dimerizes in the absence of nucleophiles. It is suggested that localization of the odd electron in a p-orbital on nitrogen imparts the hydrogen abstraction activity of the radical cation. Since there are no free p-orbitals on the carbon atoms of the aromatic rings in arene radical cations the hydrogen atom abstraction
reaction pathway is not observed.
9-取代的吖啶基阳离子在二氯甲烷-Bu4NPF6(0.2 M)中与环己-1,4-二烯发生了简便的氢原子抽取反应。衍生物循环伏安法研究了反应的动力学,观察到反应符合 EC 机制(电荷转移后发生不可逆的一阶反应)。反应产物是质子化的吖啶底物和环己-1,4-二烯的二聚底物加合物。对 9-苯基吖啶和 9-苯基蒽自由基阳离子的反应进行了比较。前者会迅速抽取氢原子,而后者则会在没有亲核物的情况下缓慢二聚。研究表明,氮的 p 轨道上奇数电子的定位赋予了自由基阳离子的取氢活性。由于芳香环碳原子上没有自由 p 轨道,因此在炔自由基阳离子中观察不到氢原子抽取反应途径。