Amination with PdNHC Complexes: Rate and Computational Studies Involving Substituted Aniline Substrates
作者:Ka Hou Hoi、Selçuk Çalimsiz、Robert D. J. Froese、Alan C. Hopkinson、Michael G. Organ
DOI:10.1002/chem.201102428
日期:2012.1.2
chloride to be electron poor, although oxidative addition is not rate limiting. Anilines couple best when they are electron rich, which would seem to discount deprotonation of the intermediate metal ammonium complex as being rate limiting in favour of reductive elimination. In previous studies with secondary amines using PEPPSI complexes, deprotonation was proposed to be the slow step in the cycle. These
使用N杂环卡宾基Pd络合物Pd-PEPPSI-IPr和Pd-PEPPSI-IPent(PEPPSI =吡啶,增强的前催化剂,制备,稳定和引发; IPr =二异丙基苯基咪唑鎓衍生物;已经研究了IPent =二异戊基苯基咪唑鎓衍生物)。速率研究表明对芳基氯的依赖是电子贫乏的,尽管氧化加成没有速率限制。当苯胺富含电子时,苯胺的耦合效果最佳,这似乎降低了中间金属铵络合物的去质子化,因为它限制了速率,有利于还原性消除。在先前使用PEPPSI配合物对仲胺进行的研究中,提出去质子化是该循环中的缓慢步骤。这些与机理有关的实验发现通过计算得到了证实。Pd-PEPPSI-IPr和受阻更严重的Pd-PEPPSI-IPent催化剂用于将失活的芳基氯化物与电子贫乏的苯胺偶联。尽管IPr催化剂反应缓慢,但IPent催化剂的性能非常好,再次显示了这种广泛使用的催化剂的高反应活性。