Radical clocks and electron transfer. Comparison of crown ether effects on the reactivity of potassium and magnesium towards 1-bromo-2-(3-butenyl)benzene. The incidence of homogeneous versus heterogeneous electron transfer on selectivity
作者:Hassan Hazimeh、Jean-Marc Mattalia、Caroline Marchi-Delapierre、René Barone、Norma S. Nudelman、Michel Chanon
DOI:10.1002/poc.986
日期:2005.12
reactivity is emphasized. This paper shows that caution should be taken when radical clocks are used to study reactions at the metal–solution interface. More specifically, the non-observation of rearranged products from the radical clock (even for the very rapid ones) under these conditions does not necessary imply that there is no radical intermediate along the dominant reaction channel. This pattern of reactivity
在存在和不存在各种添加剂的情况下,在室温和低温下,研究了芳基原子钟1-溴-2-(3-丁烯基)苯1Br的标题前体在THF中对钾和镁的反应。添加剂是顺式-二环己基-18-冠-6或叔-丁醇。第一个通过形成碱形成可溶钾,第二个从自由基环化中区分碳负离子。加入1BR钾件产量的THF悬浮液中显着低的量的从自由基环化得到的产物,在对比的量报道Bunnett和贝克威思的组为67%氨的33%的反应叔丁醇介质。用钾碎片在THF中获得的环化产物的量与镁与1Br反应中观察到的量相同在THF中。这种相似性使我们可以放弃先前提出的三元组假说,该假说是为说明格利雅试剂形成中芳基卤化物自由基钟的环化产物量出乎意料的低而提出的。将冠醚加到THF反应介质中引起钾和镁的对比作用。对于钾,观察到自由基环化的显着增加,而当溶剂是二乙醚时,冠的添加抑制了格氏试剂的形成,而当它是THF时,更有效地抑制了格利雅试剂的形成。观察到的效果是