Structure, Conformation, and Stereodynamics of the Atropisomers of Highly Hindered Benzyl Ethers
作者:Daniele Casarini、Carmine Coluccini、Lodovico Lunazzi、Andrea Mazzanti
DOI:10.1021/jo0603173
日期:2006.6.1
the title compounds indicate that they adopt a synclinal (sc) conformation, in agreement with the prediction of ab initio computations. In the case of the most-hindered derivative (compound 4), the conformation is syn-periplanar (sp), as is also shown by X-ray diffraction. Such stereolabile sp- or sc-atropisomers exist as two conformational enantiomers: the corresponding enantiomerization barriers, covering
四种标题化合物的低温和NOE NMR光谱表明,与从头算的预测相一致,它们采用对折(sc)构象。在最受阻碍的导数(化合物4)的情况下,其构型是顺周平面(sp),这也可以通过X射线衍射看出。相应enantiomerization障碍,覆盖6.6至9.7千卡mol的范围内:此类stereolabile SP-或SC-阻转异构体作为两种对映异构体的构象存在- 1,可以为所有所检查的化合物进行测定。在两种情况下(化合物3和5),所述次要antiperiplanar(AP)阻转异构体也观察,并在sc向AP互屏障测量(11.7和11.9千卡摩尔-1)。另外,已经检测到异丙基和叔丁基取代基的旋转受限,并且已经确定了相应的屏障。