Mono- and diylide-substituted phosphines (YPhos): impact of the ligand properties on the catalytic activity in gold(i)-catalysed hydroaminations

Abstract

The monoylide-phosphines show a linear correlation between their donor strength and their activity in gold-catalysed hydroaminations, while steric congestions leads to lower activities of the diylide congeners despite their higher donor properties.

Towards the rational design of ylide-substituted phosphines for gold(i)-catalysis: from inactive to ppm-level catalysis

“…As such, the PPh 3 moiety always points towards the gold centre, suggesting that the ligand should be able to stabilize a cationic gold species by additional arenegold interactions. This was also observed for other YPhos gold complexes [10,11] and has become a more general design principle for ligands in gold catalysis including phosphines and N-heterocyclic carbenes. [7,18] Interestingly, the aryl substituents in the ylide-backbone of all LAuCl complexes rotate out of the P-C-P plane.…”

“…To examine the impact of the different aryl substituents on the activity of the complexes in gold(I) catalysed hydroaminations we chose the reaction of phenylacetylene with aniline as test reaction, since many other ligands have been tested in this transformation, thus allowing for a more detailed comparison. [10,11,14,[9][10][11][12][13][14][15][16][17][18][19][20]22] The reactions were conducted at mild conditions (50 °C) with low catalyst loadings of only 0.1 mol% LAuCl and NaBAr F 4 for halide abstraction. Surprisingly, only small changes were observed with the ligands 1-3 (Figure 4), suggesting that electronic changes in the aryl group have only little impact on the catalytic activity.…”

Phosphorus‐Containing Superbases: Recent Progress in the Chemistry of Electron‐Abundant Phosphines and Phosphazenes

“…[ 19 , 42 ] During research on ylide and yldiide compounds as ligands in transition metal complexes and the stabilization of reactive low‐valent main group elements, Gessner and co‐workers connected the strongly π‐donating ylidyl groups as substituents to a phosphorus atom and obtained electron‐abundant ylidylphosphines (YPhos). [ 108 , 109 , 110 , 111 , 112 ]…”

“…[19,42] During research on ylide and yldiide compounds as ligands in transition metal complexes and the stabilization of reactive low-valent main group elements, Gessner and co-workers connected the strongly π-donating ylidyl groups as substituents to a phosphorus atom and obtained electron-abundant ylidylphosphines (YPhos). [108,109,110,111,112] Three simple reaction paths A-C in Scheme 14 were presented to synthesize ylidylphosphines starting from alkylphosphonium salts, which can be easily prepared via reaction of the respective phosphine with alkylhalides (Scheme 14). [113,115] Depending on the nature of Z, double deprotonation with metal bases and subsequent nucleophilic substitution at halophosphines deliver the desired YPhos ligands 34a-e in moderate to high yields of 69-92 % (route A).…”

“…[108,109,114] The resulting ligands in Cy Y Me PCy 2 (34k-m) show elevated stability and a remarkable performance in palladium-catalyzed amination reactions of aryl chlorides at room temperature (Scheme 14). [108,109] YPhos ligands in general represent valuable electron-rich phosphines, which was demonstrated by their readily formation of transition metal complexes, such as gold(I) [106,111,115] or palladium [112][113][114] complexes, which have been successfully employed as catalysts in amination and hydroamination reactions, as well as alpha arylation with arylchlorides among others. [116] Scheme 11.…”