Mechanism of Electrochemical Generation and Decomposition of Phthalimide- N -oxyl
Mechanism of Electrochemical Generation and Decomposition of Phthalimide- N -oxyl
复制标题
邻苯二甲酰亚胺-N-氧基的电化学生成与分解机理
DOI：
10.1021/jacs.1c04181
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发表时间：
2021
影响因子：
15
通讯作者：
Stephenson, Corey R.
中科院分区：
文献类型：
--
作者：
Yang, Cheng;Farmer, Luke A.;Pratt, Derek A.;Maldonado, Stephen;Stephenson, Corey R.
邻苯二甲酰亚胺-N-氧自由基（PINO）是一种高效的氢原子转移（HAT）催化剂，可由N-羟基邻苯二甲酰亚胺（NHPI）通过电化学反应生成。然而，催化剂分解限制了其应用。本文详细研究了PINO在电化学条件下的生成和分解机理。伏安数据，从本体电解观察，和计算研究表明两个主要方面。首先，通过多位点协同质子-电子转移（MS-CPET）从NHPI发生碱促进的PINO形成。第二，PINO分解发生在至少两个二阶路径上，其中一个被基大大增强。在PINO催化氧化中的最佳催化效率发生在碱的存在下，所述碱的相应共轭酸具有在1011 -15范围内的pKa，这在促进PINO形成和使其衰减最小化之间达到平衡。
PhthalimideN-oxyl (PINO) is a potent hydrogen atom transfer (HAT) catalyst that can be generated electrochemically fromN-hydroxyphthalimide (NHPI). However, catalyst decomposition has limited its application. This paper details mechanistic studies of the generation and decomposition of PINO under electrochemical conditions. Voltammetric data, observations from bulk electrolysis, and computational studies suggest two primary aspects. First, base-promoted formation of PINO from NHPI occurs via multiple-site concerted proton–electron transfer (MS-CPET). Second, PINO decomposition occurs by at least two second-order paths, one of which is greatly enhanced by base. Optimal catalytic efficiency in PINO-catalyzed oxidations occurs in the presence of bases whose corresponding conjugate acids have pKa’s in the range of ∼11–15, which strikes a balance between promoting PINO formation and minimizing its decay.