Bifunctional Ligand Enables Efficient Gold‐Catalyzed Hydroalkenylation of Propargylic Alcohol

The synthesis and characterization of original NHC ligands based on an imidazo[1,5-a]pyridin-3-ylidene (IPy) scaffold functionalized with aflanking barbituric heterocycle is described as well as their use as tunable ligands for efficient gold-catalyzed CÀN, CÀO, and CÀCb ond formations.H igh activity,regio-, chemo-, and stereoselectivities are obtained for hydroelementation and domino processes,u nderlining the excellent performance (TONs and TOFs) of these IPy-based ligands in gold catalysis.The gold-catalyzed domino reactions of 1,6-enynes give rise to functionalizedh eterocycles in excellent isolated yields under mild conditions.T he efficiency of the NHC gold 5 Me complex is remarkable and mostly arises from acombination of steric protection and stabilization of the cationic Au I active species by ligand 1 Me . Scheme 2. Gold-catalyzed intermolecularaddition of amine and carboxylic acids to phenylacetylene and 1-dodecyne.Scheme 3. Au-catalyzed domino cyclization/nucleophilic addition of 1,6-enynesw ith various nucleophiles. [a] in CH 2 Cl 2 ;n .i. not isolated.

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An Original L‐shape, Tunable N‐Heterocyclic Carbene Platform for Efficient Gold(I) Catalysis

Tang

Benaissa

Huynh

et al. 2019

Angewandte Chemie

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Au⋅⋅⋅H−C Hydrogen Bonds as Design Principle in Gold(I) Catalysis

et al. 2021

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Secondary ligand–metal interactions are decisive in many catalytic transformations. While arene–gold interactions have repeatedly been reported as critical structural feature in many high‐performance gold catalysts, we herein report that these interactions can also be replaced by Au⋅⋅⋅H−C hydrogen bonds without suffering any reduction in catalytic performance. Systematic experimental and computational studies on a series of ylide‐substituted phosphines featuring either a PPh3 (PhYPhos) or PCy3 (CyYPhos) moiety showed that the arene‐gold interaction in the aryl‐substituted compounds is efficiently compensated by the formation of Au⋅⋅⋅H−C hydrogen bonds. The strongest interaction is found with the C−H moiety next to the onium center, which due to the polarization results in remarkably strong interactions with the shortest Au⋅⋅⋅H−C hydrogen bonds reported to date. Calorimetric studies on the formation of the gold complexes further confirmed that the PhYPhos and CyYPhos ligands form similarly stable complexes. Consequently, both ligands showed the same catalytic performance in the hydroamination, hydrophenoxylation and hydrocarboxylation of alkynes, thus demonstrating that Au⋅⋅⋅H−C hydrogen bonds are equally suited for the generation of highly effective gold catalysts than gold‐arene interactions. The generality of this observation was confirmed by a comparative study between a biaryl phosphine ligand and its cyclohexyl‐substituted derivative, which again showed identical catalytic performance. These observations clearly support Au⋅⋅⋅H−C hydrogen bonds as fundamental secondary interactions in gold catalysts, thus further increasing the number of design elements that can be used for future catalyst construction.

show abstract

An Original L‐shape, Tunable N‐Heterocyclic Carbene Platform for Efficient Gold(I) Catalysis

et al. 2019

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The synthesis and characterization of original NHC ligands based on an imidazo[1,5‐a]pyridin‐3‐ylidene (IPy) scaffold functionalized with a flanking barbituric heterocycle is described as well as their use as tunable ligands for efficient gold‐catalyzed C−N, C−O, and C−C bond formations. High activity, regio‐, chemo‐, and stereoselectivities are obtained for hydroelementation and domino processes, underlining the excellent performance (TONs and TOFs) of these IPy‐based ligands in gold catalysis. The gold‐catalyzed domino reactions of 1,6‐enynes give rise to functionalized heterocycles in excellent isolated yields under mild conditions. The efficiency of the NHC gold 5Me complex is remarkable and mostly arises from a combination of steric protection and stabilization of the cationic AuI active species by ligand 1Me.

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Bifunctional Ligand Enables Efficient Gold‐Catalyzed Hydroalkenylation of Propargylic Alcohol

Cited by 7 publications

References 59 publications

An Original L‐shape, Tunable N‐Heterocyclic Carbene Platform for Efficient Gold(I) Catalysis

An Original L‐shape, Tunable N‐Heterocyclic Carbene Platform for Efficient Gold(I) Catalysis

Au⋅⋅⋅H−C Hydrogen Bonds as Design Principle in Gold(I) Catalysis

An Original L‐shape, Tunable N‐Heterocyclic Carbene Platform for Efficient Gold(I) Catalysis

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