Ruprecht-Karls-Universität Heidelberg, Organisch-Chemisches Institut, Heidelberg, Germany.
Chirality. 2013 Feb;25(2):126-32. doi: 10.1002/chir.22125. Epub 2012 Dec 22.
We investigated the stereodynamics of 5,5'-substituted tropos BIPHEP ligands (2,2'-bis(diphenylphosphino)-biphenyls) by enantioselective dynamic high-performance liquid chromatography (DHPLC) to elucidate the influence of the substitution pattern and electronics of the substituents (methyl, methoxy, and hydroxyl groups). By temperature-dependent dynamic HPLC measurements the activation parameters ΔG(╪), ΔH(╪), and ΔS(╪) could be determined with high precision, revealing that the activation barrier of these 5,5'-substituted BIPHEP ligands ranges in a narrow band between 87.8 and 93.0 kJ mol(-1), making them highly attractive as deracemizable dynamic chiral ligands in asymmetric catalysis. Interestingly, the activation parameters are highly influenced by a hydroxyl or methoxy group in the 5,5'-position of the BIPHEP ligands.
我们通过对映选择性动态高效液相色谱法（DHPLC）研究了 5,5'-取代的外消旋 BIPHEP 配体（2,2'-双（二苯基膦基）联苯）的立体动力学，以阐明取代基的取代模式和电子效应（甲基、甲氧基和羟基）的影响。通过与温度相关的动态 HPLC 测量，可以高精度地确定这些 5,5'-取代的 BIPHEP 配体的活化参数 ΔG(╪)、ΔH(╪)和 ΔS(╪)，结果表明这些配体的活化能垒在 87.8 和 93.0 kJ mol(-1)之间的狭窄范围内，这使得它们成为不对称催化中极具吸引力的可拆分动态手性配体。有趣的是，BIPHEP 配体的 5,5'-位上的羟基或甲氧基基团高度影响活化参数。
