Acceleration of Pd-Catalyzed Amide N-Arylations Using Cocatalytic Metal Triflates: Substrate Scope and Mechanistic Study
作者:Joseph Becica、Graham E. Dobereiner
DOI:10.1021/acscatal.7b01317
日期:2017.9.1
comparison with iodobenzene (PhI). The observation of an aryl halide dependence on rate and various qualitative kinetic experiments are consistent with a mechanism in which ligand exchange of halide for amide (“transmetalation”) is turnover limiting. The mechanism may be different depending on whether PhBr or PhI is used as a coupling partner. Oxidative addition complexes (xantphos)Pd(Ph)(X) (X = Br, I;
助催化三氟甲磺酸金属盐助剂加速了酰胺与芳基卤化物的钯/黄磷催化的交叉偶联。一项对氮亲核试剂的调查显示,当Al(OTf)3时,各种N-芳基酰胺产品的收率都有所提高除了某些例外,它被用作催化添加剂。初始催化速率表明,与溴代碘苯(PhI)相比,使用溴代苯(PhBr)时路易斯酸的加速作用更为明显。芳基卤化物对速率的依赖性以及各种定性动力学实验的观察结果与卤化物配体交换为酰胺(“过渡金属化”)受到限制的机理是一致的。该机制可能会有所不同,具体取决于将PhBr或PhI用作偶联伴侣。制备了氧化加成络合物(xantphos)Pd(Ph)(X)(X = Br,I; xantphos = 4,5-双(二苯基膦基)-9,9-二甲基x吨),可能是催化的中间体; 与Yb(OTf)3的不同相互作用 在溶液中类似于催化机理的卤化物依赖性,我们提出该机理源自催化过程中可逆的路易斯酸介导的卤化物抽象。