Copper Salts as Additives in Gold(I)‐Catalyzed Reactions

Abstract

Statt Silber: CuI‐ und CuII‐Salze können Ag‐Additive bei AuI‐katalysierten Reaktionen ersetzen. Reaktivitätsstudien und NMR‐Experimenten zufolge bildet sich durch Anionenmetathese von CuYn (Y=OTf, BF4, PF6, SbF6) mit [R3PAuCl] das Produkt [R3PAu]Y. Der Prozess ist langsam, weshalb kein schneller Zerfall der aktiven Spezies erfolgt; dies ermöglicht Reaktionen im Großmaßstab, selbst bei hohen Temperaturen und bei niedriger Konzentration des Goldkomplexes.

Activation of an Au−Cl Bond by a Pendent SbIII Lewis Acid: Impact on Structure and Catalytic Activity

“…In both of these cases, catalyst activation is rapid and irreversible. Although the resultant active catalysts are highly active, they are often fragile, decomposing to catalytically inactive [L 2 Au] + and metallic gold . Additionally, the use of silver salt‐mediated anion metathesis method requires the removal of AgX, which may itself be catalytically active, from the reaction mixture.…”

“…In an effort to address the stability of gold catalysts, a number of novel strategies have been developed. An area of particular focus towards this end has been the replacement of silver salts with alternative Lewis acids that act as chloride scavengers . In addition to avoiding the use of silver salts, the use of alternative Lewis acids may facilitate slow, reversible activation of the gold precatalyst, thus improving the robustness of the system.…”

“…In addition to avoiding the use of silver salts, the use of alternative Lewis acids may facilitate slow, reversible activation of the gold precatalyst, thus improving the robustness of the system. An example of such a system is provided by Gandon, who demonstrated that addition of a substoichiometric amount of Cu(OTf) 2 to Ph 3 AuCl promotes the electrophilic cyclization of enynes . Gandon has also extended this strategy to main group Lewis acids, including In III , Si IV , and Bi III salts …”

Synthesis of N-heterocycles through cyclization-triggered tandem additions to alkynes and the study of promoters in ionic reactions.

“…105 Recently, Lafolle and Gandon reported the use of Cu(OTf)2 to activate L-AuCl. 106 The aforementioned non-silver activation methods have limitations. First of all, gold precatalysts like L-Au-CH3 and L-Au-OH have only been synthesized successfully for a limited set of ligands.…”

Mechanistic insights and functionalization of alkynes in homogeneous gold catalysis.

“…[68][69][70][71][72][73][74] In most gold catalyzed reactions, catalyst loadings in the 1-5% range are the norm. [14][15][16][17][18] One reason for the low turnover numbers (TON) is the relatively fast decay of cationic gold and its conversion into non-reactive species (e.g., Au [75][76][77][78][79] Despite this drawback, there has been no comprehensive systematic investigations on the decay of homogeneous gold catalysis, a stark contrast with the extensive work reported on catalyst deactivation in heterogeneous catalysis. 80 In this chapter, we answer some fundamental and intriguing questions on gold(I) decay, such as the effects of starting material, nucleophile, solvent, counterion and additives, and we offer a probable pathway for gold(I) decay.…”