Hydroxy-amide Functionalized Azolium Salts for Cu-Catalyzed Asymmetric Conjugate Addition: Stereocontrol Based on Ligand Structure and Copper Precatalyst
作者:Naoatsu Shibata、Misato Yoshimura、Haruka Yamada、Ryuichi Arakawa、Satoshi Sakaguchi
DOI:10.1021/jo300472r
日期:2012.4.20
designed and synthesized for Cu-catalyzed asymmetric conjugate addition reaction. The (CH2)2-bridged hydroxy-amide functionalized azolium ligand precursors 2, in addition to the previously reported CH2-bridged azolium salts 1, have been prepared from readily available enantiopure β-amino alcohols. The combination of a Cu species with 1 or 2 efficiently promoted the 1,4-addition reaction of cyclic enones
已经设计并合成了一系列羟基酰胺官能化的偶氮盐,用于铜催化的不对称共轭加成反应。除了先前报道的CH 2-桥连的氮鎓盐1之外,还已经由容易获得的对映纯β-氨基醇制备了(CH 2)2-桥联的羟基酰胺官能化的azo鎓配体前体2。Cu种类与1或2的组合有效地促进了环状烯酮与二烷基锌的1,4-加成反应。例如,在催化量的Cu(OTf)存在下,2-cyclohepten-1-one(17)与Bu 2 Zn的反应图2和图1给出了(S)-3-丁基环庚酮(20),产率为99%,ee为96%。在另一方面,当反应物的Cu(OTF)的影响下,进行2具有组合2,(- [R )- 20优先于(小号) - 20在98%的产率和80%的ee值获得。以这种方式,通过控制手性配体的结构来切换对映异构性。另外,通过将具有相同配体的Cu预催化剂从Cu(OTf)2改变为Cu(acac)2也可以实现对映选择性的逆转。Cu(acac)2与CH的结合17与Bu