Silver(I)-Catalyzed C–X, C–C, C–N, and C–O Cross-Couplings Using Aminoquinoline Directing Group via Elusive Aryl-Ag(III) Species

Abstract

Cross-coupling transformations are a powerful tool in organic synthesis. It is known that this kind of transformations undergoes 2-electron redox processes and, for this reason, silver has been nearly forgotten as catalyst for cross-couplings since silver is mainly considered as a 1-electron redox metal. Herein, we disclose effective Ag(I)-catalyzed cross-coupling transformations using bidentate aminoquinoline as a directing group towards different nucleophiles to form CC , C-N and CO bonds. DFT calculations indicate the feasible oxidative addition of L 1-I substrate via Ag(I)/Ag(III) catalytic cycle. Furthermore, ion spectroscopy experiments suggest a highly reactive aryl-Ag(III) that in absence of nucleophiles reacts to form an intermolecular cyclic product [5d-Ag(I)-CH 3 CN], which in solution forms 5a. This work proves that silver can undergo 2-electron redox processes in cross-coupling reactions like Pd and Cu.

C(sp2)-CF3 Reductive Elimination from Well-Defined Argentate(III) Complexes [nBu4N][Ag(Ar)(CF3)3]

“…Silver, unlike its congeners copper and gold or its neighbors nickel, palladium, and platinium, is perhaps one of the least understood late transition metals. Specifically, recently, several silver-mediated or catalytic carbon–carbon or carbon–heteroatom bond-forming cross-coupling reactions were reported. Yet, the mechanisms of these coupling reactions remain elusive.…”

Origin of the different reactivity of the high-valent coinage-metal complexes [RCuIIIMe3]− and [RAgIIIMe3]− (R = allyl)

“…This provides experimental evidence that the silver-mediated transformation proceeds via a i/iii oxidation state sequence just as its copper analogue. 13 In line with this, Ribas, Roithová and co-workers have demonstrated that silver(i)-catalyzed cross-coupling reactions involve 2-electron redox processes 5,6 similar to the corresponding copper(i) chemistry. 1,14,15 Despite these similarities between copper-and silver-mediated C−C coupling reactions, the reaction between LiMMe 2 •LiI and RX reveals a striking difference for M = Cu and Ag (X = Cl, I for M = Cu, Ag, respectively).…”

“…1,2 In contrast, analogous silver-mediated transformations are by far not that well established, 3,4 but the potential of silver to mediate the formation of carbon−carbon bonds has become a greater focus of attention just recently. [5][6][7][8][9][10] While the usefulness of organoargentates in stoichiometric alkylation reactions was questioned on the basis of theoretical calculations and gas-phase experiments in the past, 11,12 a collaboration between a few of us and the Ogle group has recently shown that a LiAgMe 2 •LiI reagent indeed undergoes a cross-coupling reaction with allyl iodide in THF. 7 By means of rapid-injection (RI) NMR spectroscopy, the argentate(iii) complex [RAgMe 3 ] − (R = allyl) formed from [AgMe 2 ] − was identified as the key intermediate in this reaction.…”

Identifying reactive intermediates by mass spectrometry

“…Another example comes from the eld of reaction development and concerns silver-catalysed C-O and C-N coupling reactions. 54 The group of Ribas envisaged catalytic cycle based on silver(I) complexes. They designed a reaction starting with a silver(I) complex which undergoes oxidative addition with an aryl iodide to form a silver(III) intermediate.…”