The anormeric effect in seven-membered rings: a comformational study of 1-oxa and 3-oxa derivatives of benzocycloheptene by nmr
作者:S. Désilets、M. St-Jacques
DOI:10.1016/s0040-4020(01)86071-3
日期:1988.1
strong -anomeric effect while for , the Ca:Ce population (5:95) is opposite. Based on UV π→π* spectral characteristics, it is deduced that delocalization of the n electrons of oxygen into the aromatic ring is not the major factor governing this behavior. A large departure from coplanarity for the n-o* orbitals, revealed by the :-O-C-OMe torsional angle calculated for , explains the weakening of the -anomeric
已经通过13 C和1 H动态NMR方法研究了2-甲氧基衍生物和3-和1-苯并二恶英(分别为和)。结果显示存在两个构象异构体C a和C e(94:6),这是由于强烈的异头作用,而对于C a:C e群体(5:95)是相反的。根据UVπ→π *光谱特征,可以推断出氧的n个电子向芳香环的离域化不是控制此行为的主要因素。否*与共面性大相径庭轨道,通过计算出的--OC -OMe扭转角揭示,解释了-α-异头作用的减弱。最后,预期更强的异头作用有助于C e形式的C e的稳定性。