Exploiting Noninnocent (E,E)-Dibenzylideneacetone (dba) Effects in Palladium(0)-Mediated Cross-Coupling Reactions: Modulation of the Electronic Properties of dba Affects Catalyst Activity and Stability in Ligand and Ligand-Free Reaction Systems
作者:Ian J. S. Fairlamb、Anant R. Kapdi、Adam F. Lee、Gerard P. McGlacken、Felix Weissburger、André H. M. de Vries、Lizette Schmieder-van de Vondervoort
DOI:10.1002/chem.200600473
日期:2006.11.24
The reactivity of palladium(0) complexes, [Pd(0) (2)(dba-n,n'-Z)(3)] (n,n'-Z=4,4'-F; 4,4'-CF(3); 4,4'-H; 4,4'-MeO) and [Pd(0)(dba-n,n'-Z)(2)] (n,n'-Z=4,4'-CF(3); 4,4'-H; 3,3',5,5'-OMe), used as precursor catalysts with suitable donor ligands (e.g. phosphines, N-heterocyclic carbenes), has been correlated in several palladium(0)-mediated cross-coupling processes. Increasing the electron density on the
钯(0)配合物[Pd(0)(2)(dba-n,n'-Z)(3)](n,n'-Z = 4,4'-F; 4,4' -CF(3); 4,4'-H; 4,4'-MeO)和[Pd(0)(dba-n,n'-Z)(2)](n,n'-Z = 4, 4'-CF(3); 4,4'-H; 3,3',5,5'-OMe)与合适的供体配体(例如膦,N-杂环卡宾)一起用作前体催化剂几个钯(0)介导的交叉偶联过程。在大多数这些方法中,增加dba-n,n'-Z配体的芳基部分的电子密度会增加总体催化活性。此效果主要源自L(n)Pd(0)-eta(2)-dba相互作用的不稳定(在dpi-pi *协同结合中,n = 1或2),这最终增加了可用于一般催化循环(氧化加成)的第一步中与卤化芳基反应的催化活性L(n)Pd(0)的总体浓度。dba-n,n'-Z配体的芳基部分上电子密度的降低可稳定Pd(0)-eta(2)-dba相互作用,从