Metathesis Reactions of Formaldehyde Acetals – Experimental and Computational Investigation of Isomeric Families of Cyclophanes under Dynamic Conditions
作者:Roberta Cacciapaglia、Stefano Di Stefano、Luigi Mandolini、Paolo Mencarelli、Franco Ugozzoli
DOI:10.1002/ejoc.200700906
日期:2008.1
The acid-catalyzed transacetalation of cyclophane formaldehyde acetals incorporating m-xylylene units (m-Ci) generates a well behaved dynamic library of oligomeric macrocycles. Effective Molarities (EM) relating to the formation of the lower cyclic oligomers (i = 2–4) were estimated from equilibrium concentrations measured under conditions closely approaching the critical monomer concentration. Comparison
包含间二甲苯单元 (m-Ci) 的环烷甲醛缩醛的酸催化转缩醛反应生成了一个表现良好的低聚大环动态库。根据在接近临界单体浓度的条件下测量的平衡浓度估计与较低环状低聚物(i = 2-4)形成相关的有效摩尔浓度 (EM)。与有关异构对环芳 p-Ci 形成的现有 EM 数据的比较表明,间环芳 m-Ci 更稳定,稳定性差异对于 i = 2 特别显着。分子模型表明 COCOC 部分在环状结构中的掺入结构强制偏离最稳定的 g+g+/g–g– 构象。与实验结果一致,对于二聚对环芳烷 p-C2,这种偏差最大,并且随着两个系列中环尺寸的增加而趋于减小。分子建模还表明,异二聚体 m,p-C2 的稳定性与 m-C2 的稳定性相当,这再次与 m-C2 和 p-C2 混合物的交叉实验结果一致。允许平衡。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany