Tropanes as Scaffolds for Phosphorus-Olefin Ligands and Their Application in Asymmetric Catalysis
作者:Sandra Vlahovic、Nicole Schädel、Stefan Tussetschläger、Sabine Laschat
DOI:10.1002/ejoc.201201539
日期:2013.3
reaction with various substrates. The most promising results in both reactions were achieved with ligands 11 and 15, which contain a chiral alkene/achiral P-unit or an achiral alkene/chiral P moiety, respectively, and where the metal is complexed on the exo side of the tropene skeleton. In contrast, ligands with an endo coordination mode showed only low (13) or no activity (12) in all of the 1,4-additions
托烷衍生的磷-烯烃杂化配体带有 P-单元(手性 BINOL 衍生单元/非手性 PPh2-单元)与托烯骨架(手性/非手性)的各种组合已被合成并用于 Cu 催化的共轭 1,4-二乙基锌与环烯酮的加成以及在 Rh 催化的苯基硼酸(Hayashi-Miyaura 反应)与环状和非环烯酮的 1,4-加成中。而在 Cu 催化的反应中,只获得了中等的产率和 ee 值(高达 49% ee),而在 Hayashi-Miyaura 反应中观察到高达 97% ee 与各种底物。两个反应中最有希望的结果是用配体 11 和 15 实现的,它们分别包含一个手性烯烃/手性 P 单元或一个非手性烯烃/手性 P 部分,并且金属络合在 tropene 骨架的外侧. 相比之下,具有内配位模式的配体在所有 1,4-添加中仅显示低活性 (13) 或无活性 (12)。NMR 和 ESI-MS 实验表明溶液中存在两种阳离子 [RhI(15)2]+