Bifunctional nickel precatalysts of amido-functionalized N-heterocyclic carbenes for base-free Michael reaction under ambient conditions
作者:Sachin Kumar、Anantha Narayanan、Mitta Nageswar Rao、Mobin M. Shaikh、Prasenjit Ghosh
DOI:10.1016/j.jorganchem.2011.09.007
日期:2012.1
bifunctional nickel precatalysts, [1-(R)-3-N-(benzylacetamido)imidazol-2-ylidene]2 Ni [R = Me (1b), i-Pr (2b), and CH2Ph (3b)], containing a Lewis acidic metal site and a Lewis basic amido-N site in a pendent ligand sidearm, have been successfully designed for base-free Michaeladdition reaction. Specifically, the nickel (1–3)b complexes catalyzed the highly desired base-free Michaeladdition reactions
一系列新的双功能镍预催化剂[1-(R)-3- N-(苄基乙酰胺基)咪唑-2-基] 2 Ni [R = Me(1b),i -Pr(2b)和CH 2 Ph(3b)]已经成功地设计了用于悬空的配体侧臂中的路易斯酸性金属位点和路易斯碱性酰胺基-N位点的无碱迈克尔加成反应。具体地,镍(1 - 3)b该配合物在环境温度下,在空气中以很高的收率催化了非常需要的代表性环状5元β-二羰基和β-酮酯底物与各种活化的烯烃化合物的无碱迈克尔加成反应。镍(1-3)b配合物是由相应的咪唑鎓氯化物盐(1-3)a与NiCl 2 •6H 2 O在K 2 CO 3为碱的情况下以55-73%的反应合成的屈服。对镍配合物进行的密度泛函理论(DFT)研究表明,在这些配合物中存在强的Ni–NHCσ相互作用。