Modular Phosphite–Oxazoline/Oxazine Ligand Library for Asymmetric Pd-Catalyzed Allylic Substitution Reactions: Scope and Limitations—Origin of Enantioselectivity
作者:Montserrat Diéguez、Oscar Pàmies
DOI:10.1002/chem.200701636
日期:2008.4.18
A library of phosphite-oxazoline/oxazine ligands L1-L15 a-h has been synthesized and screened in the Pd-catalyzed allylic substitution reactions of several substrate types. These series of ligands can be prepared efficiently from easily accessible hydroxyl amino acid derivatives. Their modular nature enables the substituents/configurations in the oxazoline/oxazine moiety, alkyl backbone chain and in
已合成了亚磷酸酯-恶唑啉/恶嗪配体L1-L15ah的文库,并在Pd催化的几种底物类型的烯丙基取代反应中进行了筛选。这些系列的配体可以由容易获得的羟基氨基酸衍生物有效地制备。它们的模块性质使恶唑啉/恶嗪部分,烷基主链和亚磷酸二芳基酯部分中的取代基/构型易于系统地变化。因此,通过仔细选择配体组分,在广泛的单和双取代线性受阻和不受阻衬板和环状底物范围内,获得了很高的区域和对映选择性(ee值高达99%)和良好的活性。对Pd-pi-烯丙基中间体的NMR研究提供了对配体参数对对映选择性起源的影响的更深刻的理解。这也表明亲核攻击主要发生在反式为亚磷酸酯部分的烯丙基末端碳原子上。