Lone-Pair-Induced Topicity Observed in Macrobicyclic Tetra-thia Lactams and Cryptands: Synthesis, Spectral Identification, and Computational Assessment
作者:Tia L. Walker、Ian S. Taschner、Sharath Chandra M、Michael J. Taschner、James T. Engle、Briana R. Schrage、Christopher J. Ziegler、Xinfeng Gao、Steven E. Wheeler
DOI:10.1021/acs.joc.8b01382
日期:2018.9.7
The synthesis of a rigid macrobicyclic N,S lactam L1 and a topologically favored in/in N,S cryptand L2 are reported with X-ray structure analysis, dynamic correlation NMR spectroscopy, and computational analysis. Lactam L1 exhibits two distinct rotameric conformations (plus their enantiomeric counterparts) at 25 °C, as confirmed via NMR spectroscopy and computational analysis. Coalescence of the resonances
通过X射线结构分析,动态相关NMR光谱和计算分析报道了刚性大双环N,S内酰胺L1和N / S隐窝L2内/中的拓扑结构的合成。内酰胺L1在25°C下表现出两个不同的旋转异构体构型(及其对映体对应物),这已通过NMR光谱学和计算分析得到了证实。在115°C时观察到L1共振的合并,从而实现了完整的核与频率相关性。将计算研究与实验数据相结合,确定了与孔微扰有关的拓扑平衡和相对能量/应变。由于N 2的构象应变增加在S 2模板中,L2中的氮孤对引起独特的跨环相互作用,从而导致在热动力学上有利于在/在螺状外消旋体中。首选拓扑结构,空间起伏和L2的电子定位相结合,可诱导通过胺赋予的手性环境,其反演势垒的计算值为10.3 kcal mol –1。