Steric and Electronic Effects on the Configurational Stability of Residual Chiral Phosphorus-Centered Three-Bladed Propellers: Tris-aryl Phosphanes
作者:Simona Rizzo、Tiziana Benincori、Valentina Bonometti、Roberto Cirilli、Patrizia R. Mussini、Marco Pierini、Tullio Pilati、Francesco Sannicolò
DOI:10.1002/chem.201201182
日期:2013.1.2
tris‐aryl phosphanes, structurally designed to exist as residual enantiomers or diastereoisomers, bearing substituents differing in size and electronic properties on the aryl rings, were synthesized and characterized. Their electronic properties were evaluated on the basis of their electrochemical oxidation potential determined by voltammetry. The configurational stability of residual phosphanes, evaluated
合成并表征了一系列结构上设计为作为残留对映异构体或非对映异构体,在芳基环上带有尺寸和电子性质不同的取代基的三三芳基膦。根据通过伏安法测定的电化学氧化电位,评估了它们的电子性能。通过在手性固定相上通过动态HPLC或/和通过动态1 H和31 P NMR光谱评估,残留膦的构型稳定性相当适中(约18–20 kcal mol -1的壁垒),低得多比相应的氧化膦所显示的要大(约25–29 kcal mol -1的势垒)。首次以对映纯状态分离了三芳基膦的残留对映体,并通过单晶异常X射线衍射分析为其分配了绝对构型。在这种情况下,消旋障碍也可以通过CD信号衰减动力学来计算。进行了详细的计算研究,以弄清螺旋反转机理。计算表明,三芳基膦的低构型稳定性可归因于出乎意料的容易的磷锥体反转,这取决于叶片上存在的取代基,即使在构成单个残留立体异构体的四个构象异构体中最稳定的情况下也可能发生。