作者:Jan Breitenfeld、Jesus Ruiz、Matthew D. Wodrich、Xile Hu
DOI:10.1021/ja4051923
日期:2013.8.14
nickel-based catalysts have been reported for cross-coupling reactions of nonactivated alkyl halides. The mechanistic understanding of these reactions is still primitive. Here we report a mechanistic study of alkyl-alkyl Kumada coupling catalyzed by a preformed nickel(II) pincer complex ([(N2N)Ni-Cl]). The coupling proceeds through a radical process, involving two nickel centers for the oxidative addition of alkyl
许多镍基催化剂已被报道用于非活化烷基卤化物的交叉偶联反应。对这些反应的机理理解仍然很原始。在这里,我们报告了由预先形成的镍 (II) 钳形配合物 ([(N2N)Ni-Cl]) 催化的烷基-烷基 Kumada 偶联的机理研究。偶联通过自由基过程进行,涉及两个用于烷基卤氧化加成的镍中心。催化作用在格氏试剂中为二级,在催化剂中为一级,在卤代烷中为零级。一种瞬态物质,[(N2N)Ni-烷基(2)](烷基(2)-MgCl),被确定为负责卤代烷活化的关键中间体,其形成是转换的决定步骤催化。
Ligand-Controlled Cobalt-Catalyzed Regio-, Enantio-, and Diastereoselective Oxyheterocyclic Alkene Hydroalkylation
developed as an efficient method for C(sp3)–C(sp3) coupling with broad substrate availability and high functional group compatibility. However, auxiliary groups, a conjugated group or a chelation-directing group, are commonly required to attain high regio- and enantioselectivities. Herein, we reported a ligand-controlled cobalt-hydride-catalyzed regio-, enantio-, and diastereoselective oxyheterocyclic