Ligand-Switchable Directing Effects of Tethered Alkenes in Nickel-Catalyzed Additions to Alkynes
作者:Karen M. Miller、Timothy F. Jamison
DOI:10.1021/ja0446799
日期:2004.12.1
Nickel-catalyzed reductive couplings of aldehydes with alkynes that contain tethered olefins are described, in which the degree and sense of regioselectivity are controlled by the length of the tether and the presence or absence of an additive. When the alkyne and alkene are separated by four bonds, very high (>95:5) regioselectivities are observed. Use of a monodentate phosphine as an additive leads
描述了醛与包含系链烯烃的炔烃的镍催化还原偶联,其中区域选择性的程度和意义由系链的长度和添加剂的存在或不存在控制。当炔烃和烯烃被四个键分开时,观察到非常高(> 95:5)的区域选择性。使用单齿膦作为添加剂导致以相等和相反的选择性(5:> 95)形成相反的区域异构体。这些结果为在区域选择性决定步骤中远程烯烃和金属中心之间的相互作用提供了强有力的证据,并表明有和没有添加剂的反应通过根本不同的机制进行。