Stereoelectronic stabilization in non-chair conformations of substituted-2,3-dihydro-1,4-benzod ioxepins
作者:Alain Lachapelle、Maurice St-Jacques
DOI:10.1016/s0040-4020(01)86008-7
日期:1988.1
NMR in two solvent systems of different polarity. The aromatic signals were found to be quite sensitive to the nature of the seven-membered cyclic geometries and were used as “conformational probes”. The results show that the chair (C) conformation is the only form detected at -120°C for the parent compound 5 and its 3-methyl derivative 6 whereas the twist-boat (TB) conformation becomes predominant
在13 C和1下研究了2,3-二氢-1,4-苯并二恶英(5)及其3-取代的衍生物6-9在两种极性不同的溶剂体系中的1 H动态NMR。发现芳族信号对七元循环几何结构的性质非常敏感,并被用作“构象探针”。结果表明,对于母体化合物5及其3-甲基衍生物6,椅子(C)构象是在-120°C时检测到的唯一形式,而对于三个衍生物3,3,扭转舟(TB)构象则占主导地位。 -立体,立体电子相互作用的结果是-二甲基7、3-甲氧基8和3,3-甲基甲氧基9。此外,在8的情况下,检测到的TB形式的详细几何形状反映了竞争性立体电子(异头和薄纱)效果的相对重要性。