Monodentate Trialkylphosphines: Privileged Ligands in Metal-catalyzed Crosscoupling Reactions

Abstract

Phosphines are widely used ligands in transition metal-catalyzed reactions. Arylphosphines, such as triphenylphosphine, were among the first phosphines to show broad utility in catalysis. Beginning in the late 1990s, sterically demanding and electronrich trialkylphosphines began to receive attention as supporting ligands. These ligands were found to be particularly effective at promoting oxidative addition in cross-coupling of aryl halides. With electron-rich, sterically demanding ligands, such as tri-tertbutylphosphine, coupling of aryl bromides could be achieved at room temperature. More importantly, the less reactive, but more broadly available, aryl chlorides became accessible substrates. Tri-tert-butylphosphine has become a privileged ligand that has found application in a wide range of late transition-metal catalyzed coupling reactions. This success has led to the use of numerous monodentate trialkylphosphines in cross-coupling reactions. This review will discuss the general properties and features of monodentate trialkylphosphines and their application in cross-coupling reactions of C–X and C–H bonds.

Enolizable Ketones as Activators of Palladium(II) Precatalysts in Amine Arylation Reactions

“…Palladium-catalyzed cross-coupling reactions have become ubiquitous methods for the construction of C–C and C–heteroatom bonds in both academic and industrial syntheses. Significant effort has been devoted to the development of optimized supporting ligands that provide highly active catalysts across a broad range of substrates, including sterically demanding trialkylphosphines, 2-biarylphosphines, and N-heterocyclic carbenes . Many synthetic protocols rely on generating the active catalyst species under the reaction conditions (in situ) through the combination of a ligand, or ligand precursor, and a palladium source.…”

Synthesis of 3-aryl-1-phosphinoimidazo[1,5-a]pyridine ligands for use in Suzuki–Miyaura cross-coupling reactions

“…7,8 Monophosphine ligands have found widespread use in metal-catalyzed cross-coupling reactions. [9][10][11][12][13] Privileged ligands such as Buchwald's biarylphosphines, [14][15][16][17] Stradiotto's biaryl P-N phosphines, [18][19][20][21] Fu/Koie/Shaughnessy's trialkylphosphines, 7,8,22 Hartwig's ferrocenes, 23,24 Ackermann's diaminochlorophosphines, 25,26 Beller's bis(adamantyl)phosphines 27 and N-aryl(benz)imidazolyl-or N-pyrrolyl-monophosphines, [28][29][30] Kwong's indolyl-based monophosphines, [31][32][33][34][35] Zhang's ClickPhos ligands, 36,37 Singer's bippyPhos ligands, 38,39 Rodriguez/Tang's oxaphospholes, 40,41 and Verkade's proazaphosphatranes 42,43 have found wide-spread use in Suzuki-Miyaura, Corriu-Kumada, Heck, Negishi, Sonagashira, carbon-heteroatom cross-coupling and Buchwald-Hartwig amination reactions (Fig. 1).…”

Amines as Activating Ligands for Phosphine Palladium(II) Precatalysts: Effect of Amine Ligand Identity on the Catalyst Efficiency

“…9b, c Hazari developed 1-( t Bu)indenyl complexes (2) that do not undergo this comproportionation reaction, which results in higher activity catalysts. 16 N,C-Palladacycle precatalysts developed by Buchwald, known as G1−G4 precatalysts (3,4), have become widely used. 10 These complexes are primed to undergo reductive elimination upon deprotonation of a coordinated amine.…”

“…Early work focused on identifying privileged classes of ligands that provide effective cross-coupling catalysts. These privileged ligand classes include bulky trialkylphosphines, 2-biarylphosphines, and N -heterocyclic carbene (NHC) ligands . The electron-donating nature of these ligands promotes oxidative addition of unreactive bonds.…”