Application of Chiral Olefin Ligands in Asymmetric Catalysis

As a novel class of potential ligands, chiral olefin ligands have attracted much attention.Chiral olefin ligands exhibit higher activity and selectivity than the traditional nitrogen, phosphine, oxide ligands in some reactions, and solved some problems that other ligands could not do.To enhance the coordination of the olefin ligands and the metal, heteroatoms were introduced to its backbone, several hybrid olefin ligands have been developed to increase the diversity of the ligands for further expanding the application of chiral olefin ligands.In this review, the recent advances in the development of chiral diene ligands, chiral phosphine olefin ligands and chiral sulfur olefin ligands, and their application in transition-metal catalyzed asymmetric reactions are reviewed.Keywords chiral olefin ligand; asymmetric catalysis; chiral diene ligand; chiral P/alkene ligand; chiral S/alkene ligand 烯烃 [1] 作为配体有着悠久的历史, 广泛存在于各类 过渡金属络合物中.然而这些络合物通常不太稳定, 烯 烃容易从金属上解离, 被其它强配位配体取代, 因此这 些络合物通常作为重要的催化剂前体应用于反应中, 而 利用手性烯烃配体 [2] 调控反应的活性和对映选择性极具 挑战性.直到 2003 年, Hayashi 等 [3a] 报道了首例 C 2 对称的手 性[2.2.1]降冰片二烯衍生物 1 作为手性配体, 用于金属 铑催化的芳基硼试剂对不饱和酮或不饱和酯的 1,4-加成 反应, 得到了非常高的催化活性和对映选择性.随后, Carreira 等 [3b] 报道的 C 1 对称的手性[2.2.2]双烯 2, 在铱催 化的烯丙基碳酸酯的动力学拆分反应中也得到了优秀 的结果.从此手性烯烃配体的开发引起了化学家们的重 视, 围绕着不对称催化而设计的手性烯烃配体陆续出 现, 在诱导不对称催化反应中取得很好的效果.这些手 性双烯配体在有些反应中甚至表现出比传统氮、磷、氧 配体更高的活性和选择性, 实现了一些利用其它类型配 体难以实现的化学转化, 由此可见, 手性烯烃配体是一 类具有重要应用前景的新型配体.