Chain-Amplified Photochemical Fragmentation of <i>N</i>-Alkoxypyridinium Salts: Proposed Reaction of Alkoxyl Radicals with Pyridine Bases To Give Pyridinyl Radicals
作者:Deepak Shukla、Shashishekar P. Adiga、Wendy G. Ahearn、Joseph P. Dinnocenzo、Samir Farid
DOI:10.1021/jo301975j
日期:2013.3.1
N-alkoxypyridiniums, which leads to N–O bond cleavage and alkoxyl radical formation, is highly chain amplified in the presence of a pyridine base such as lutidine. Density functional theory calculations support a mechanism in which the alkoxyl radicals react with lutidine via proton-coupled electron transfer (PCET) to produce lutidinyl radicals (BH•). A strong electron donor, BH• is proposed to reduce
在吡啶碱基(如二甲基吡啶)的存在下,光诱导的电子转移至N-烷氧基吡啶鎓,导致N-O键断裂和烷氧基自由基的形成,被高度链扩增。密度泛函理论计算支持了一种机制,其中烷氧基与二甲基吡啶通过质子偶合电子转移(PCET)反应,生成鲁替丁基(BH •)。提议使用强电子给体BH •还原另一个烷氧基吡啶鎓阳离子,从而导致链扩增,量子产率接近200。动力学数据和计算结果支持形成第二种更强的还原剂:BH •与氢之间的氢键配合物。另一个基础分子(BH •···B)。四种吡啶鎓盐(带有N-甲氧基和N-乙氧基取代基的4-苯基和4-氰基)反应的量子产率数据的全局拟合导致了一组一致的动力学参数。反应的链性质允许从稳态动力学和独立确定的链终止速率常数确定速率常数。的反应速率常数CH 3 ö •与二甲基吡啶以形成BH •,ķ 1,是〜6×10 6中号-1小号-1 ; CH 3 CH 2 O •的碳原子比大约大9倍。CD的反应3