Merzliakov Dmitry A, Alexeev Michael S, Topchiy Maxim A, Yakhvarov Dmitry G, Kuznetsov Nikolai Yu, Maximov Anton L, Beletskaya Irina P
A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninsky Prospect 29, Moscow 119991, Russia.
Federal Research Center Kazan Scientific Center of Russian Academy of Sciences, Lobachevskogo St. 2/31, Kazan 420111, Russia.
Molecules. 2025 Jan 10;30(2):248. doi: 10.3390/molecules30020248.
In this study, the homogeneous carboxylation of potassium, sodium, and lithium phenolates in DMSO solution at 100 °C by the Kolbe-Schmitt reaction was investigated. The impact of water, phenolate concentration, and cation nature on the yield of products and reaction selectivity was demonstrated. Based on the patterns observed, it was concluded that a complex cluster mechanism governs the carboxylation reaction in the solution. The use of a homogeneous reaction medium allowed for convenient testing of various additives to assess their impact on the reaction. Basic additives such as sodium salts of mesitol, -butylcalix[4]arene, sodium isopropyl, and -butyl cabonates were found to enhance the reaction, increasing the yield of hydroxybenzoic acids by 20% (to 61.6%). The main product in the DMSO solution was identified as 4-hydroxybenzoic acid, in contrast to the classical Kolbe-Schmitt method which typically yields 2-hydroxybenzoic (salicylic) acid. The use of C NMR spectroscopy enabled the observation of a "carbonate complex" in the solution for the first time, with the carbonate carbon displaying a chemical shift value of 142 ppm, an unusual finding for stable carbonates, and located between the signals of free dissolved CO and carboxylate derivatives.
在本研究中，研究了在100℃下，通过科尔贝-施密特反应，在二甲基亚砜（DMSO）溶液中，钾、钠和锂的酚盐的均相羧化反应。证明了水、酚盐浓度和阳离子性质对产物收率和反应选择性的影响。基于观察到的模式，得出结论：一种复杂的簇机制控制着溶液中的羧化反应。使用均相反应介质便于测试各种添加剂，以评估它们对反应的影响。发现碱性添加剂，如均三甲苯的钠盐、对叔丁基杯[4]芳烃、异丙基钠和对叔丁基碳酸盐，可促进反应，使羟基苯甲酸的收率提高20%（达到61.6%）。与通常生成2-羟基苯甲酸（水杨酸）的经典科尔贝-施密特方法不同，DMSO溶液中的主要产物被鉴定为4-羟基苯甲酸。使用碳-13核磁共振（¹³C NMR）光谱首次观察到溶液中的“碳酸盐配合物”，碳酸盐碳的化学位移值为142 ppm，这对于稳定的碳酸盐来说是一个不寻常的发现，且位于游离溶解的一氧化碳和羧酸盐衍生物的信号之间。
