Lefèvre Guillaume, Jutand Anny
Ecole Normale Supérieure, Département de Chimie, UMR CNRS-ENS-UPMC 8640, 24 Rue Lhomond, 75231 Paris Cedex 5 (France), Fax: (+33) 1-4432-2502; Department of Chemistry, The University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada).
Chemistry. 2014 Apr 14;20(16):4796-805. doi: 10.1002/chem.201304716. Epub 2014 Mar 5.
The mechanism of the reactions of aryl/heteroaryl halides with aryl Grignard reagents catalyzed by [Fe(III)(acac)3] (acac=acetylacetonate) has been investigated. It is shown that in the presence of excess PhMgBr, [Fe(III)(acac)3] affords two reduced complexes: [PhFe(II)(acac)(thf)n] (n=1 or 2) (characterized by (1)H NMR and cyclic voltammetry) and PhFe(I)(acac)(thf) (characterized by cyclic voltammetry, (1)H NMR, EPR and DFT). Whereas [PhFe(II)(acac)(thf)n] does not react with any of the investigated aryl or heteroaryl halides, the Fe(I) complex PhFe(I)(acac)(thf) reacts with ArX (Ar=Ph, 4-tolyl; X=I, Br) through an inner-sphere monoelectronic reduction (promoted by halogen bonding) to afford the corresponding arene ArH together with the Grignard homocoupling product PhPh. In contrast, PhFe(I)(acac)(thf) reacts with a heteroaryl chloride (2-chloropyridine) to afford the cross-coupling product (2-phenylpyridine) through an oxidative addition/reductive elimination sequence. The mechanism of the reaction of PhFe(I)(acac)(thf) with the aryl and heteroaryl halides has been explored on the basis of DFT calculations.
研究了由[Fe(III)(acac)3]（acac = 乙酰丙酮）催化的芳基/杂芳基卤化物与芳基格氏试剂的反应机理。结果表明，在过量的PhMgBr存在下，[Fe(III)(acac)3]可生成两种还原配合物：[PhFe(II)(acac)(thf)n]（n = 1或2）（通过(1)H NMR和循环伏安法表征）和PhFe(I)(acac)(thf)（通过循环伏安法、(1)H NMR、EPR和DFT表征）。虽然[PhFe(II)(acac)(thf)n]不与任何研究的芳基或杂芳基卤化物反应，但Fe(I)配合物PhFe(I)(acac)(thf)通过内球单电子还原（由卤键促进）与ArX（Ar = Ph，4 - 甲苯基；X = I，Br）反应，生成相应的芳烃ArH以及格氏均偶联产物PhPh。相比之下，PhFe(I)(acac)(thf)与杂芳基氯（2 - 氯吡啶）反应，通过氧化加成/还原消除序列生成交叉偶联产物（2 - 苯基吡啶）。基于DFT计算探索了PhFe(I)(acac)(thf)与芳基和杂芳基卤化物反应的机理。
