Lithium−Sulfoxide−Lithium Exchange for the Asymmetric Synthesis of Atropisomers under Thermodynamic Control
作者:Jonathan Clayden、David Mitjans、Latifa H. Youssef
DOI:10.1021/ja017702o
日期:2002.5.1
introduces a sulfoxide substituent ortho to the stereogenic Ar-CO axis of an aromatic amide. The sulfoxide exerts a powerful conformational bias on the axis, such that after rapid equilibration at ambient temperature essentially only one of two diastereoisomeric Ar-CO atropisomers is populated. Sulfoxide-lithium exchange by treatment with t-BuLi regenerates the ortholithiated amide in an enantiomerically pure
正锂化和与对甲苯亚磺酸 (-)-薄荷酯的反应在芳族酰胺的立体异构 Ar-CO 轴邻位引入亚砜取代基。亚砜在轴上施加强大的构象偏差,因此在环境温度下快速平衡后,基本上只有两种非对映异构 Ar-CO 阻转异构体中的一种被填充。通过用 t-BuLi 处理的亚砜-锂交换以对映体纯和构象稳定的形式再生原锂化酰胺。因此,有机锂的快速亲电捕获产生高度对映异构富集的阻转异构叔芳香酰胺。整个过程,包括锂暂时取代亚砜到锂,相当于热力学控制下的动态分辨率。