Synthesis of NHC Ligands Containing a Sulfoxide Moiety and Their Use in Cross-Coupling via a Au(I)/(III) Catalytic Cycle

Abstract

We designed and synthesized a new series of NHCs with a sulfoxide moiety as a hemilabile ligand. We investigated the catalytic activities of Au(I)-NHC complexes in the strong oxidant-free cross-coupling of iodoarenes with 1,3,5-trimethoxybenzene. We ascertained that the sulfoxide moiety is critical for the Au(I)/(III) catalytic cycle.

Hemilabile MIC^N ligands allow oxidant-free Au(i)/Au(iii) arylation-lactonization of γ-alkenoic acids

“…53,54 The 1,2-heteroarylation of alkenes was also achieved using external alcohols and amines. [54][55][56] Interestingly, (MeDalphos)AuCl catalyst has proven to be a key factor in the development of other transformations such as 1,2-diarylation of alkenes In contrast to the known PˆN ligands, the use of bidentate CˆN or C^O ligands 61 remains scarcely explored, and the few representative examples are described in Scheme 1b. Cadierno and Michelet studied the catalytic activity of a (NHCˆN)Au(III) complex containing a N-heterocyclic carbene ligand (NHC) with a pyridinium side arm in the cyclization of g-alkynoic acids (Scheme 1b), 62 while Messerle and coworkers explored the dihydroalkoxylation and hydroamination catalyzed by a Au(III) complex bearing a NHC ligand with two pendant pyrazole arms (Scheme 1b).…”

“…In contrast to the well-known P^N ligands, the use of bidentate C^N or C^O ligands 61 remains scarcely explored, and the few representative examples are depicted in Scheme 1b . Cadierno and Michelet studied the catalytic activity of a (NHC^N)Au( iii ) complex containing a N -heterocyclic carbene ligand (NHC) with a pyridinium side arm in the cyclization of γ-alkynoic acids ( Scheme 1b ), 62 while Messerle and coworkers explored the dihydroalkoxylation and hydroamination catalyzed by a Au( iii ) complex bearing a NHC ligand with two pendant pyrazole arms ( Scheme 1b ).…”

Heart of gold: enabling ligands for oxidative addition of haloorganics in Au(i)/Au(iii) catalysed cross-coupling reactions

“…51 Au( i )/Au( iii ) will no doubt see a growing body of bidentate ligands applied to Au( i )/Au( iii ) catalysis such as the very recent application of the sulfoxide moiety. 52 Au-mediated cross-coupling reactions can also provide a unique platform for the synthesis of molecules and ligands in studies identifying organocatalytic and transition-metal catalysed alternatives to Pd-catalysts, where minute Pd-impurities have misled researchers in the past. 53 Elimination of synthetic steps involving Pd-catalysis would mitigate these instances, providing a useful technique to prevent Pd-contamination and mechanism convolution in future reactions.…”

Consolidation of the Oxidant‐Free Au(I)/Au(III) Catalysis Enabled by the Hemilabile Ligand Strategy

“…In parallel to hemilabile (P^N) ligands facilitating Au(I)/Au(III) cross‐coupling catalysis, there is a growing interest in exploring other types of hemilabile ligands within the scientific community. While examples of (C^O) ligands are scanty, [8aa,34] the utilization of hemilabile (C^N) ligands is thriving [8ae,af] . In 2022, Ribas and co‐workers reported a groundbreaking study employing a hemilabile mesoionic carbenes (MIC) ligand featuring a pendant pyridine or pyrimidine group.…”