Trineopentylphosphine: A Conformationally Flexible Ligand for the Coupling of Sterically Demanding Substrates in the Buchwald–Hartwig Amination and Suzuki–Miyaura Reaction
2013
Raders, Steven M. | Moore, Jane N. | Parks, Jacquelynn K. | Miller, Ashley D. | Leißing, Thomas M. | Kelley, Steven P. | Rogers, Robin D. | Shaughnessy, Kevin H.
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.
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