Mechanistic Investigation into the Gold-Catalyzed Decarboxylative Cross-Coupling of Iodoarenes

Abstract

While many gold catalyzed reactions have been thoroughly developed, most are not thought to involve redox events at gold. In contrast, recent advances have demonstrated the feasibility of redox gold catalysis. This report describes a detailed mechanistic investigation of the gold catalyzed decarboxylative cross-coupling, which likely proceeds via a high valent Au(I/III) pathway. This investigation includes a kinetic analysis, stoichiometric experiments with Au(III) complexes, and DFT calculations. These data support a turnover limiting oxidative addition to form an Au(III) aryl complex, with an off cycle resting state. The dominant pathway appears to proceed through a silver mediated decarboxylation with a subsequent Ag(I) to Au(III) transmetalation. These data provide some rationale for the significant counterion effects between SbF6– and NTf2– and may explain why MeDalphos is not a superior ligand for the catalytic reaction.