Cu/<i>N</i>-Oxyl-catalyzed aerobic oxidative esterification to oxalic acid diesters from ethylene glycol <i>via</i> highly selective intermolecular alcohol oxidation
Cu/<i>N</i>-Oxyl-catalyzed aerobic oxidative esterification to oxalic acid diesters from ethylene glycol <i>via</i> highly selective intermolecular alcohol oxidation
复制标题
Cu/<i>N</i>-Oxyl 催化有氧氧化酯化乙二醇<i>通过</i>高选择性分子间醇氧化生成草酸二酯
DOI：
10.1039/d1gc04001d
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发表时间：
2022
期刊：
影响因子：
9.8
通讯作者：
Yamaguchi Kazuya
中科院分区：
文献类型：
--
作者：
Morino Yusuke;Yatabe Takafumi;Suzuki Kosuke;Yamaguchi Kazuya
理想的绿色酯化反应之一是氧氧化酯化反应，只使用化学计量比的不同醇，通过分子间选择性醇氧化，然后添加其他醇形成半缩醛，半缩醛氧化到酯。然而，氧化酯化合成草酸二酯的研究尚未见报道，这可能是由于分子间醇氧化的选择性难以控制以及乙二醇醇/半缩醛对氧化催化剂的络合作用所致。在本文中，我们描述了在CuCl/tetramethylethylenediamine/1，5-dimethyl-9-azanoradamantane N-氧基催化剂的作用下，即使在其他脂肪族伯醇存在的情况下，乙二醇酯选择性氧化乙二醇醇/半缩醛生成各种草酸酯的高效氧氧化酯化反应。值得注意的是，使用理想的乙二醇和伯醇/仲醇的化学计量比，绿色反应效果很好。深入的实验研究和理论计算表明，乙二醇醇/半缩醛与铜(II)物种的优先双齿配位以及有效的两电子/一质子转移使高选择性氧化酯化成为可能。
One of the ideal green esterification reactions is aerobic oxidative esterification using only a stoichiometric amount of different alcohols via intermolecular selective alcohol oxidation followed by hemiacetal formation by the addition of the other alcohol and hemiacetal oxidation to esters. However, oxalic acid diester synthesis via oxidative esterification has not been reported to date, possibly owing to the difficulty of selectivity control of intermolecular alcohol oxidation and the chelating effects of ethylene glycol-derived alcohols/hemiacetals on inhibiting oxidation catalysts. Herein, using a CuCl/tetramethylethylenediamine/1,5-dimethyl-9-azanoradamantane N-oxyl catalyst, we describe a highly efficient aerobic oxidative esterification reaction of ethylene glycol to various oxalic acid diesters via selective oxidation of ethylene glycol-derived alcohols/hemiacetals even in the presence of other aliphatic primary alcohols. Notably, the green reaction works well using an ideal stoichiometric ratio of ethylene glycol and primary/secondary alcohols. Thorough experimental investigation and theoretical calculations revealed that highly selective oxidative esterification is enabled by the preferential bidentate coordination of ethylene glycol-derived alcohols/hemiacetals to the Cu(II) species, followed by efficient two-electron/one-proton transfer.