Oximes of 3,7-dimethylocta-2,6-dienal: Green synthesis, preparative separation of all diastereomers and complete assignment of 1H and 13C NMR spectra
作者:Niko S. Radulović、Magdalena M. Tasić、Marko Z. Mladenović
DOI:10.1016/j.molstruc.2020.129427
日期:2021.3
Abstract A mixture of four diastereomeric oximes was prepared starting from citral, an inexpensive mixture of neral and geranial ((Z)- and (E)-3,7-dimethylocta-2,6-dienal, respectively), in a solvent-free mechano-chemical reaction with NH2OH•HCl/NaOH, at room temperature. All stereoisomeric oximes ((1E,2E), (1Z,2E), (1E,2Z), and (1Z,2Z)) were isolated in pure state by isocratic silica-gel column chromatography
摘要 以柠檬醛为原料制备了四种非对映异构肟的混合物,柠檬醛是一种廉价的橙花醛和香叶醛(分别为 (Z)- 和 (E)-3,7-二甲基辛基-2,6-二烯醛)的混合物),在无溶剂中在室温下与 NH2OH•HCl/NaOH 发生机械化学反应。所有立体异构肟 ((1E,2E)、(1Z,2E)、(1E,2Z) 和 (1Z,2Z)) 均通过等度硅胶柱色谱法以纯态分离。首次在两种氘代溶剂中通过 1D 和 2D NMR 光谱分离和单独表征肟。它们的光谱被完全分配并相互比较。属于 -CH2CH2- 部分的高阶多重态的偶联常数值由(迭代)自旋模拟确定。对所有非对映异构体的 NOESY 光谱的仔细分析表明,肟在 CDCl3 中形成了氢键加合物。在肟化条件下,共轭烯醛中C2-C3双键的构型没有改变。柠檬醛的纯肟在 CDCl3 或 DMSO-d6 中长时间放置导致 C=N 键异构化,同时保持共轭 C=C 键构型不变。