Remote Stereoelectronic Effects in Pyrrolidone- and Caprolactam-Substituted Phenols: Discrepancies in Antioxidant Properties Evaluated by Electrochemical Oxidation and H-Atom Transfer Reactivity
Remote Stereoelectronic Effects in Pyrrolidone- and Caprolactam-Substituted Phenols: Discrepancies in Antioxidant Properties Evaluated by Electrochemical Oxidation and H-Atom Transfer Reactivity
复制标题
DOI：
10.1021/acs.joc.2c00207
复制
发表时间：
2022-04-15
影响因子：
3.6
通讯作者：
Syroeshkin, Mikhail A.
中科院分区：
文献类型：
--
作者：
Akyeva, Anna Ya;Kansuzyan, Artem, V;Syroeshkin, Mikhail A.
新的抗氧化剂通常通过两种主要方法进行评估，即，提供电子的能力和拦截自由基的能力。我们通过评价11种同时含有抗氧化剂部分（单酚和多酚）和辅助药效团（吡咯烷酮和己内酰胺）的化合物的性质来比较这些方法。添加几种常用的抗氧化剂，如丁基化羟基甲苯（BHT），2，3，5-三甲基苯酚（TMP），槲皮素和二氢槲皮素锡进行比较。用循环伏安法测定了它们与DPPH自由基的反应速率和氧化电位。虽然这些方法测试不同的化学性质，但它们的结果并不完全一致。然而，也有一些例外，这两种方法给出了相反的预测!其中之一是单酚和多酚的不同行为：多酚与DPPH的反应速度比氧化电位相似的单酚快一个数量级。第二个例外是苄基位置上的"旁观者"内酰胺环的大小。虽然具有七元内酰胺环的酚类更难氧化，但空间上无阻碍的化合物与DPPH的反应速度比类似的五元内酰胺快约2倍。对计算方法的局限性，特别是单参数计算方法的局限性进行了评价和讨论
New antioxidants are commonly evaluated via two main approaches, i.e.,the ability to donate an electron and the ability to intercept free radicals. We comparedthese approaches by evaluating the properties of 11 compounds containing bothantioxidant moieties (mono- and polyphenols) and auxiliary pharmacophores(pyrrolidone and caprolactam). Several common antioxidants, such as butylatedhydroxytoluene (BHT), 2,3,5-trimethylphenol (TMP), quercetin, and dihydroquerce-tin, were added for comparison. The antioxidant properties of these compounds weredetermined by their rates of reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicaland their oxidation potentials from cyclic voltammetry. Although these methods test different chemical properties, their resultscorrelate reasonably well. However, several exceptions exist where the two methods give opposite predictions! One of them is thedifferent behavior of mono- and polyphenols: polyphenols can react with DPPH more than an order of magnitude faster thanmonophenols of a similar oxidation potential. The second exception stems from the size of a"bystander"lactam ring at the benzylicposition. Although the phenols with a seven-membered lactam ring are harder to oxidize, the sterically nonhindered compoundsreact with DPPH about 2xfaster than the analogousfive-membered lactams. The limitations of computational methods, especiallythose based on a single parameter, are also evaluated and discussed