The synthesis and characterization of four phosphorus macrocycles (1–4) are reported. The X-ray crystal structures of compounds 1–4 and solvate 1·H2O show the molecules in asymmetric conformations with at least one methyl group of the phenoxy substituents oriented toward the centre of the macrocyclic cavity. Variable-temperature 1H NMR experiments show that in solution the molecules exist mainly as rapidly interconverting conformers. In the 18-membered ring 1, the dynamic process results in the enantiomerization of asymmetric conformers with a barrier of 8 kcal mol–1.‡ The 21-membered ring 3 is more flexible and exists in several conformations.
报告了四种
磷大环(1-4)的合成和表征。化合物 1-4 和溶质 1-
H2O 的 X 射线晶体结构显示,分子呈不对称构象,苯氧基取代基中至少有一个甲基朝向大环空腔的中心。变温 1H NMR 实验表明,在溶液中,分子主要以快速相互转化的构象存在。在 18 元环 1 中,动态过程导致了不对称构象的对映体转化,转化障碍为 8 kcal mol-1。