Gold-Catalyzed Intermolecular Alkyne Hydrofunctionalizations—Mechanistic Insights

Leung, Chin Hin; Baron, Marco; Biffis, Andrea

doi:10.3390/catal10101210

Cited by 40 publications

(26 citation statements)

References 133 publications

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“…While palladium has historically dominated this field, other transition metals have arisen as efficient and orthogonal alternatives. Gold has been typically exploited in catalysis mostly for its Lewis acidity, [27] however, a number of studies have demonstrated the involvement of its redox chemistry in several cross‐coupling reactions using external oxidants, photoredox catalytic cycles or chelating/hemilabile ligands. [ 2c , 2d , 4f , 28 ] Further developments in this still young area of gold‐promoted cross‐coupling reactions have been hampered by the scarce mechanistic understanding of the individual steps along the proposed catalytic cycles.…”

Section: Discussionmentioning

confidence: 99%

C−C Cross‐Couplings from a Cyclometalated Au(III) CN Complex: Mechanistic Insights and Synthetic Developments

Bonsignore

Thomas

Rigoulet

et al. 2021

Chemistry A European J

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In recent years, the reactivity of gold complexes was shown to extend well beyond π-activation and to hold promises to achieve selective cross-couplings in several CÀ C and CÀ E (E = heteroatom) bond forming reactions. Here, with the aim of exploiting new organometallic species for crosscoupling reactions, we report on the Au(III)-mediated C-(sp 2 )À C(sp) occurring upon reaction of the cyclometalated complex [Au(C CH2 N)Cl 2 ] (1, C CH2 N = 2-benzylpyridine) with AgPhCC. The reaction progress has been monitored by NMR spectroscopy, demonstrating the involvement of a number of key intermediates, whose structures have been unambiguously ascertained through 1D and 2D NMR analyses ( 1 H, 13 C, 1 H-1 H COSY, 1 H-13 C HSQC and 1 H-13 C HMBC) as well as by HR-ESI-MS and X-ray diffraction studies. Furthermore, crystallo-graphic studies have serendipitously resulted in the authentication of zwitterionic Au(I) complexes as side-products arising from cyclization of the coupling product in the coordination sphere of gold. The experimental work has been paralleled and complemented by DFT calculations of the reaction profiles, providing valuable insight into the structure and energetics of the key intermediates and transition states, as well as on the coordination sphere of gold along the whole process. Of note, the broader scope of the cross-coupling at the Au(III) C CH2 N centre has also been demonstrated studying the reaction of 1 with C(sp 2 )-based nucleophiles, namely vinyl and heteroaryl tin and zinc reagents. These reactions stand as rare examples of C(sp 2 )À C(sp 2 ) cross-couplings at Au(III).

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Section: Discussionmentioning

confidence: 99%

C−C Cross‐Couplings from a Cyclometalated Au(III) CN Complex: Mechanistic Insights and Synthetic Developments

Bonsignore

Thomas

Rigoulet

et al. 2021

Chemistry A European J

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“…DFT studies vigorously promoted the investigations of mechanism for Au(I)‐catalyzed hydroamination [59–62] and gave the general information of intermediate bonding, N‐nucleophile types in the dehydrogenation step and the energetics of the whole catalytic cycle. Based on the mechanism of gold(I) catalyzed hydroamination, [63–66] the triangular tri‐gold species were proposed to firstly interact with an terminal alkyne and form a catalytically active cationic Au(I)‐alkyne complex in situ. For gold catalyzed functionalization of terminal alkynes like hydroamination or hydrophenoxylation, di‐gold σ, π‐acetylide complexes are more and more considered as the activated intermediates due to their easy access and properties [67–77] .…”

Section: Resultsmentioning

confidence: 99%

Syntheses of Triangular Gold Complexes and Their Applications in Hydroamination Reaction

Sun

et al. 2021

Eur J Inorg Chem

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Triangular all‐metal complexes have aroused our research interest due to their unique structural and properties. Herein, through the facile reduction of μ3‐oxo complex [μ3‐O(PPh3Au)3]+BF4− (1), we synthesized and isolated the triphenylphosphine stabilized triangular tri‐gold complex [(PPh3Au)3]+BF4− (2) for the first time (yield=90 %). Both complexes showed interesting photochemical sensitivity to temperatures and solvents. The cyclic voltammetry of these complexes showed one single oxidation process in CH3CN. These tri‐gold complexes (2 mol % based on the complex itself) were further applied in the catalytic hydroaminations for substituted phenylacetylenes with anilines and gave the corresponding imine products with great catalytic reactivity and regioselectivity without aiding any promoters or additives. When the loading of the tri‐gold complexes was decreased to 1.0 mol%, 95 % and 97 % of conversions were obtained using 1 and 2, respectively. When further decreased the catalyst loading to 0.5 mol% in preparative scale, 83 % and 80 % of isolated yields were achieved, respectively. This method presented great significance for the syntheses of a series of imine‐containing pharmaceutical intermediates even in preparative scale. Moreover, the investigations of catalytic mechanisms of this reaction indicated that these tri‐gold complexes played important roles as efficient pre‐catalysts in hydroaminations.

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“…With the help of known information on the hydroalkoxylation reaction, numerous research groups have focused their efforts on the intermolecular hydrophenoxylation of (13) Gold catalysts bearing N-heterocyclic carbene (NHC) ligands are currently being studied due to their high catalytic activity in the alkyne hydroalkoxylation field [32]. However, gold catalysts containing NHC ligands in the presence of alkyne compounds can form π-complexes with an electrophilic character [33] and are capable to carry out a nucleophilic attack by nucleophiles such as alcohols or amines to obtain vinyl amines or ethers [34]. In addition, current reports have revealed that the steric demand from NHC ligands and the solvent effect play a significant role in gold-mediated catalysis.…”

Section: Hydroalkoxylationmentioning

confidence: 99%

Towards Dual-Metal Catalyzed Hydroalkoxylation of Alkynes

et al. 2021

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Poly (vinyl ethers) are compounds with great value in the coating industry due to exhibiting properties such as high viscosity, soft adhesiveness, resistance to saponification and solubility in water and organic solvents. However, the main challenge in this field is the synthesis of vinyl ether monomers that can be synthetized by methodologies such as vinyl transfer, reduction of vinyl phosphate ether, isomerization, hydrogenation of acetylenic ethers, elimination, addition of alcohols to alkyne species etc. Nevertheless, the most successful strategy to access to vinyl ether derivatives is the addition of alcohols to alkynes catalyzed by transition metals such as molybdenum, tungsten, ruthenium, palladium, platinum, gold, silver, iridium and rhodium, where gold-NHC catalysts have shown the best results in vinyl ether synthesis. Recently, the hydrophenoxylation reaction was found to proceed through a digold-assisted process where the species that determine the rate of the reaction are PhO-[Au(IPr)] and alkyne-[Au(IPr)]. Later, the improvement of the hydrophenoxylation reaction by using a mixed combination of Cu-NHC and Au-NHC catalysts was also reported. DFT studies confirmed a cost-effective method for the hydrophenoxylation reaction and located the rate-determining step, which turned out to be quite sensitive to the sterical hindrance due to the NHC ligands.

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Gold-Catalyzed Intermolecular Alkyne Hydrofunctionalizations—Mechanistic Insights

Cited by 40 publications

References 133 publications

C−C Cross‐Couplings from a Cyclometalated Au(III) CN Complex: Mechanistic Insights and Synthetic Developments

C−C Cross‐Couplings from a Cyclometalated Au(III) CN Complex: Mechanistic Insights and Synthetic Developments

Syntheses of Triangular Gold Complexes and Their Applications in Hydroamination Reaction

Towards Dual-Metal Catalyzed Hydroalkoxylation of Alkynes

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