Department of Chemistry, The University of Alabama, Box 870336, Tuscaloosa, Alabama 35487-0336, USA.
J Org Chem. 2013 May 17;78(10):4649-64. doi: 10.1021/jo400435z. Epub 2013 May 6.
Trineopentylphosphine (TNpP) in combination with palladium provides a highly effective catalyst for the Buchwald-Hartwig coupling of sterically demanding aryl bromides and chlorides with sterically hindered aniline derivatives. Excellent yields are obtained even when both substrates include 2,6-diisopropyl substituents. Notably, the reaction rate is inversely related to the steric demand of the substrates. X-ray crystallographic structures of Pd(TNpP)2, [Pd(4-t-Bu-C6H4)(TNpP)(μ-Br)]2, and [Pd(2-Me-C6H4)(TNpP)(μ-Br)]2 are reported. These structures suggest that the conformational flexibility of the TNpP ligand plays a key role in allowing the catalyst to couple hindered substrates. The Pd/TNpP system also shows good activity for the Suzuki coupling of hindered aryl bromides.
三正戊基膦（TNpP）与钯结合为空间位阻大的芳基溴化物和氯化物与空间位阻大的苯胺衍生物的 Buchwald-Hartwig 偶联提供了一种非常有效的催化剂。即使两个底物都包含 2,6-二异丙基取代基，也能获得优异的产率。值得注意的是，反应速率与底物的空间位阻成反比。报道了 Pd(TNpP)2、[Pd(4-t-Bu-C6H4)(TNpP)(μ-Br)]2 和 [Pd(2-Me-C6H4)(TNpP)(μ-Br)]2 的 X 射线晶体结构。这些结构表明，TNpP 配体的构象灵活性在允许催化剂偶联受阻底物方面起着关键作用。Pd/TNpP 体系对于受阻芳基溴化物的 Suzuki 偶联也表现出良好的活性。
