Quaternary Alkyl Ammonium Salt-Catalyzed Transformation of Glycidol to Glycidyl Esters by Transesterification of Methyl Esters,ACS Catalysis

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Quaternary Alkyl Ammonium Salt-Catalyzed Transformation of Glycidol to Glycidyl Esters by Transesterification of Methyl Esters
ACS Catalysis ( IF 11.3 ) Pub Date : 2018-01-11 00:00:00 , DOI: 10.1021/acscatal.7b03303
Shinji Tanaka ₁ , Takuya Nakashima ₁ , Toshie Maeda ₁ , Manussada Ratanasak ₂ , Jun-ya Hasegawa ₂ , Yoshihiro Kon ₁ , Masanori Tamura ₁ , Kazuhiko Sato ₁

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Catalytic transformation of glycidol while maintaining its epoxide moiety intact is challenging because the terminal epoxide that interacts with the hydroxyl group via a hydrogen bond is labile for the ring-opening reaction. We found that a quaternary alkyl ammonium salt catalyzes the selective transformation of glycidol to glycidyl esters by transesterification of methyl esters. The developed method can be applied to the synthesis of multiglycidyl esters, which are valuable epoxy resin monomers. Mechanistic studies revealed the formation of a binding complex of glycidol and quaternary alkyl ammonium salt in a nonpolar solvent and the generation of the alkoxide anion as a catalyst through the ring-opening reaction of the epoxide. Computational studies of the reaction mechanism indicated that the alkoxide anion derived from glycidol tends to abstract the proton of another glycidol rather than work as a nucleophile, initiating the catalytic transesterification. Payne rearrangement of the deprotonated glycidol, which produces a destabilized base that promotes nonselective reactions, is energetically unfavorable due to the double hydrogen bond between the anion and diol. The minimal interaction between the quaternary alkyl ammonium cation and the epoxide moiety inhibited the random ring-opening pathway leading to polymerization.

中文翻译：

季烷基烷基铵盐催化的甲基酯的酯交换反应将缩水甘油转化为缩水甘油酯

缩水甘油的催化转化同时保持其环氧化物部分完整是具有挑战性的，因为通过氢键与羟基相互作用的末端环氧化物对于开环反应是不稳定的。我们发现季烷基铵盐通过甲酯的酯交换反应催化缩水甘油缩水合为缩水甘油酯。所开发的方法可用于多缩水甘油酯的合成，多缩水甘油酯是有价值的环氧树脂单体。机理研究表明，在非极性溶剂中缩水甘油与季烷基铵盐的结合络合物的形成，以及通过环氧化物的开环反应生成了作为催化剂的醇盐阴离子。对反应机理的计算研究表明，由缩水甘油产生的醇盐阴离子趋向于提取另一缩水甘油的质子，而不是作为亲核试剂起作用，从而引发了催化酯交换反应。由于阴离子和二醇之间存在双氢键，因此产生质子化的缩水甘油缩水甘油酯的Payne重排会产生不利于能量的不利反应，从而促进非选择性反应。季烷基铵阳离子和环氧化物部分之间的最小相互作用抑制了导致聚合的无规开环途径。由于阴离子和二醇之间的双氢键，在能量上不利。季烷基铵阳离子和环氧化物部分之间的最小相互作用抑制了导致聚合的无规开环途径。由于阴离子和二醇之间的双氢键，在能量上不利。季烷基铵阳离子和环氧化物部分之间的最小相互作用抑制了导致聚合的无规开环途径。

更新日期：2018-01-11

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