Counterion Effects in Homogeneous Gold Catalysis

Abstract

Homogeneous gold catalysis has received growing attention over the past few years, enabling the replacement of consolidated organic reactions with more simple, selective, and chemically sustainable alternatives. The fine-tunability of the electronic as well as steric properties of gold catalysts contributed substantially to the popularity of the research field, with robust applications in total synthesis and asymmetric catalysis. In this context, the metal counterions proved of pivotal importance in impacting both kinetics and selectivity of gold-assisted transformations. Despite the intrinsic difficulties in properly rationalizing and predicting the role of anions in complex reaction machineries, nowadays, some general trends are available. This review aims at presenting some leading examples of counterion-controlled gold catalysis, with particular emphasis on their structure–activity relationship.

Reaction Intermediates Kinetics in Solution Investigated by Electrospray Ionization Mass Spectrometry: Diaurated Complexes

“…TsOH here) can either suggest that the protodeauration step is the rate determining step, 44 or that there is active involvement of the anions in the initial deprotonation of adduct B to form neutral monoaurated intermediates. 45 Tosylate was suggested as particularly favorable anion. 46 respectively.…”

An Antimony(V) Dication as a Z‐Type Ligand: Turning on Styrene Activation at Gold

“…Given the weakly coordinating nature of the triflimide anion and its extensive use as ac ounteranion in goldmediated catalysis, [13] we became eager to test the catalytic properties of [4][NTf 2 ] 2 .W hen [4][NTf 2 ] 2 was generated in situ by addition of 3equivalents of AgNTf 2 to [2a] [Cl],w e observed rapid styrene polymerization (Scheme 2). [14] The emergence of such ar eactivity for ab is(phosphine)gold moiety such as that in [4][NTf 2 ] 2 is surprising and reflective of the reactivity enhancement achieved in the polycationic gold complex.…”

Formal Synthesis of (+)‐Laurencin by Gold(I)‐Catalyzed Intramolecular Dehydrative Alkoxylation

“…Since the active gold catalyst is formed in situ and it has been established that the silver salt counteranion can significantly affect its reactivity, [11] various silver salts were examined (Table 2). Based on the preliminary studies, optimization of the silver salt was accomplished with 10 mol% of IPrAuCl at 50 °C for 48 h. No reaction was observed with AgOTs and AgOAc (entries 1 and 2) and reactivity increased in the order of AgAsF 6 , AgBF 4 , AgSbF 6 and AgOTf, yielding up to 50% α,α′- cis -oxocene 3b .…”