A Radical-Anion Chain Mechanism Initiated by Dissociative Electron Transfer to a Bicyclic Endoperoxide: Insight into the Fragmentation Chemistry of Neutral Biradicals and Distonic Radical Anions
作者:David C. Magri、Mark S. Workentin
DOI:10.1002/chem.200701740
日期:2008.2.18
however, in competition with the second ET from the electrode, the distonic radical anion undergoes a beta-scission fragmentation yielding 1,4-diphenyl-1,4-butanedione radical anion and ethylene in a mechanism involving less than one electron. These observations are rationalized by an unprecedented catalytic radical-anion chain mechanism, the first ever reported for a bicyclic endoperoxide. The product
通过异质电化学技术研究了在N,N-二甲基甲酰胺中两个二苯基取代的双环内过氧化物的电子转移(ET)还原。该研究除评估先前未知的热化学参数外,还提供了影响OO键还原机理并决定二甲苯基自由基阴离子反应性的结构参数的见解。值得注意的是,标准还原电势和键离解能(BDEs)分别被评估为-0.55 +/- 0.15 V和20 +/- 3 kcal mol(-1),最后一个代表有史以来最低的BDEs。 。内过氧化物通过OO键的协同离解电子转移(DET)还原反应,生成二异氰酸基自由基阴离子中间体。1,4-二苯基-2,3-二氧杂双环的还原[2.2。2] oct-5-ene(1)通过总的双电子机理定量形成1,4-二苯基环己-2-烯-顺-1,4-二醇。相反,ET与1,4-二苯基-2,3-二氧杂双环[2.2.2]辛烷(2)产生1,4-二苯基环己烷-顺式1,4-二醇作为主要产物。但是,与来自电极的第二个ET竞争时,二