Backbone-Modified <i>C</i><sub>2</sub>-Symmetrical Chiral Bisphosphine TMS-QuinoxP*: Asymmetric Borylation of Racemic Allyl Electrophiles
作者:Hiroaki Iwamoto、Yu Ozawa、Yuta Takenouchi、Tsuneo Imamoto、Hajime Ito
DOI:10.1021/jacs.0c08899
日期:2021.5.5
electrophiles was also achieved using (R,R)-5,8-TMS-QuinoxP* (up to 90% ee, s = 46.4). An investigation into the role of the silyl groups on the ligand backbone using X-ray crystallography and computational studies displayed interlocking structures between the phosphine and silyl moieties of (R,R)-5,8-TMS-QuinoxP*. The results of DFT calculations revealed that the entropy effect thermodynamically destabilizes
已开发出一种新的C 2 -对称P -chirogenic 双膦配体,在配体骨架上具有甲硅烷基取代基,( R , R )-5,8-TMS-QuinoxP*。该配体对环状烯丙基亲电试剂的直接对映会聚硼酸化显示出比其母体配体 ( R , R )-QuinoxP*更高的反应性和对映选择性(例如,对于哌啶类底物:95% ee 与 76% ee)。使用 ( R , R )-5,8-TMS-QuinoxP* (高达 90% ee, s= 46.4)。使用 X 射线晶体学和计算研究对配体骨架上甲硅烷基的作用进行了调查,结果显示 ( R , R )-5,8-TMS-QuinoxP*的膦和甲硅烷基部分之间存在互锁结构。DFT 计算结果表明,熵效应在热力学上破坏了催化循环中休眠的二聚体物种以提高反应性。此外,在直接对映收敛的情况下,详细的计算表明碳-碳双键具有明显的对映选择性识别,这实际上不受烯丙基位置手性的影