作者:Ashkharuhi G. Aleksanyan、Robert M. Hakobyan、Aleksan G. Shahkhatuni、Astghik A. Shahkhatuni、Hovhannes S. Attaryan
DOI:10.1002/jhet.4529
日期:2022.11
without change of initial 3-or 5-methyl configuration. However, once the group attached to the nitrogen was removed, two individual isomers gained back their tautomeric properties and became the same mixture of tautomers, as expected. Close monitoring by NMR spectroscopy vividly demonstrates the loss and then reverting of tautomeric properties of 3(5)-pyrazole derivatives along the set of chemical transformations
互变异构是吡唑的关键特征,它与吡唑中两个氮之间的氢转移有关。学术界普遍接受的是,除了某些极端条件外,3(5)-取代吡唑衍生物的互变异构体不能作为单独的化合物分离。在这里,利用 N-取代抑制互变异构化并允许它们分离和分离的事实,合成、分离和进一步修饰了 3(5)-吡唑的 N-丙酸酯的单个异构体,并进一步修改了数次而不改变初始 3-或 5-甲基构型。然而,一旦去除了与氮相连的基团,两个单独的异构体就恢复了它们的互变异构体特性,并成为相同的互变异构体混合物,正如预期的那样。通过 NMR 光谱的密切监测生动地证明了 3(5)-吡唑衍生物的互变异构特性的损失,然后沿着旨在可能分离两个互变异构体的化学转化集恢复。未能分离它们再次证明溶液中互变异构体的动态平衡是3(5)-甲基吡唑的固有特性。