Reactions of N-methyl-N-(4-biphenylyl)nitrenium ion with electron-rich arenes:: Laser flash photolysis and product studies
Reactions of N-methyl-N-(4-biphenylyl)nitrenium ion with electron-rich arenes:: Laser flash photolysis and product studies
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DOI：
10.1021/ja011049n
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发表时间：
2002-04-10
影响因子：
15
通讯作者：
Falvey, DE
中科院分区：
文献类型：
--
作者：
Chiapperino, D;McIlroy, S;Falvey, DE
通过1-(N-methyl-N-4-biphenylyl)amino-2，4，6-trimethylpyridinium四氟硼酸盐的光解及其与各种给体取代芳烃(如1，3，5-三甲氧基苯、均三甲苯、1，4-二甲氧基苯、六甲苯等)的反应，生成了芳基氮离子N-甲基-N-(4-联苯基)氮离子。用产物分析和激光闪光光解对其进行了检测。一般来说，芳烃捕获短暂的硝离子会产生三种类型的产物：(1)母胺，N-甲基-N-4-联苯胺；(2)邻位加合物，其中环与硝离子中心邻位连接到芳环上；以及(3)N-加合物，其中硝离子氮连接到陷阱上。激光闪光光解研究表明，这些捕获反应的速率从10(4)到10(9)M-1 S(-1)不等，这取决于芳烃陷阱的结构。这些捕获速率常数与芳烃的单电子氧化电位无关，也与直接亲电取代得到的o-络合物的预期稳定性无关。我们认为，观察到的速率常数对应于芳基氮离子和芳烃陷阱之间初始形成的pi-络合物。然后，这个络合物形成观察到的产物。
An arylnitrenium ion, N-methyl-N-(4-biphenylyl)nitrenium ion, was generated through photolysis of 1-(N-methyl-N-4-biphenylyl)amino-2,4,6-trimethylpyridinium tetrafluoroborate, and its reactions with various donor-substituted arenes (e.g., 1,3,5-trimethoxybenzene, mesitylene, 1,4-dimethoxybenzene, hexamethylbenzene, etc.) were examined using product analysis and laser flash photolysis. In general, trapping of the short-lived nitrenium ion by the arenes leads to three types of products: (1) the parent amine, N-methyl-N-4-biphenylylamine; (2) an ortho-adduct, where the ring position ortho to the nitrenium ion center is bonded to the arene ring; and (3) an N-adduct, where the nitrenium ion nitrogen is bonded to the trap. Laser flash photolysis studies show that the rates of these trapping reactions vary from 10(4) to 10(9) M-1 s(-1), depending on the structure of the arene trap. These trapping rate constants do not correlate with the one-electron oxidation potential of the arene, nor with the expected stability of a o-complex derived from direct electrophilic aromatic substitution. It is argued that the observed rate constants correspond to initial formation of a pi-complex between the arylnitrenium ion and the arene trap. This complex then forms the observed products.