Ligand-Enabled Oxidative Fluorination of Gold(I) and Light-Induced Aryl–F Coupling at Gold(III)

Abstract

MeDalphos Au(I) complexes featuring aryl, alkynyl, and alkyl groups readily react with electrophilic fluorinating reagents such as N-fluorobenzenesulfonimide and Selectfluor. The ensuing [(MeDalphos)Au(R)F] + complexes have been isolated and characterized by multinuclear NMR spectroscopy as well as X-ray diffraction. They adopt a square-planar contra-thermodynamic structure, with F trans to N. DFT/IBO calculations show that the N lone pair of MeDalphos assists and directs the transfer of F + to gold. The [(MeDalphos)Au(Ar)F] + (Ar = Mes, 2,6-F 2 Ph) complexes smoothly engage in C−C cross-coupling with PhCCSiMe 3 and Me 3 SiCN, providing direct evidence for the oxidative fluorination/ transmetalation/reductive elimination sequence proposed for F + -promoted gold-catalyzed transformations. Moreover, direct reductive elimination to forge a C−F bond at Au(III) was explored and substantiated. Thermal means proved unsuccessful, leading mostly to decomposition, but irradiation with UV−visible light enabled efficient promotion of aryl−F coupling (up to 90% yield).The light-induced reductive elimination proceeds under mild conditions; it works even with the electron-deprived 2,6-difluorophenyl group, and it is not limited to the contra-thermodynamic form of the aryl Au(III) fluoride complexes.

Photosensitized Reductive Elimination of Gold(III) to Enable Esterification of Aryl Iodides with Carboxylic Acids

“…Therefore, the experimental conditions necessary to trigger the key C–O bond formation were successfully identified. Although ester formation could be achieved (24%) under direct irradiation conditions for 18 h without the photocatalyst [ BP ] (Figure C(iv)), which is consistent with the photosensitization pathway, ester formation seems to be greatly enhanced in the presence of the photocatalyst (Figure C(v)). , Very recently, a light-induced reductive elimination to forge aryl–F at aryl-Au(III) fluoride complexes was just reported by Bourissou …”

Organometallic Oxidative Addition Complexes for S-Arylation of Free Cysteines

“…In order to test the limits of these bioconjugation reactions further, expansion of ligands and utilization of other metals for OA complexes may result in additional tools, particularly with the aid of computational understanding of the mechanism. Notably, OA complexes can be potentially accessed not only through a direct oxidative addition process of an aryl-based electrophile but also indirectly via other routes. − …”