A Chiral Gold Nanocluster Au20 Protected by Tetradentate Phosphine Ligands

The chirality of a gold nanocluster can be generated from either an intrinsically chiral inorganic core or an achiral inorganic core in a chiral environment. The first structural determination of a gold nanocluster containing an intrinsic chiral inorganic core is reported. The chiral gold nanocluster [Au₂₀(PP₃)₄]Cl₄ (PP₃=tris(2‐(diphenylphosphino)ethyl)phosphine) has been prepared by the reduction of a gold(I)–tetraphosphine precursor in dichloromethane solution. Single‐crystal structural determination reveals that the cluster molecular structure has C₃ symmetry. It consists of a Au₂₀ core consolidated by four peripheral tetraphosphines. The Au₂₀ core can be viewed as the combination of an icosahedral Au₁₃ and a helical Y‐shaped Au₇ motif. The identity of this Au₂₀ cluster is confirmed by ESI‐MS. The chelation of multidentate phosphines enhances the stability of this Au₂₀ cluster.     

Direct Evidence for Intermolecular Oxidative Addition of σ(SiSi) Bonds to Gold

Oxidative addition plays a major role in transition‐metal catalysis, but this elementary step remains very elusive in gold chemistry. It is now revealed that in the presence of GaCl₃, phosphine gold chlorides promote the oxidative addition of disilanes at low temperature. The ensuing bis(silyl) gold(III) complexes were characterized by quantitative ³¹P and ²⁹Si NMR spectroscopy. Their structures (distorted Y shape) and the reaction profile of σ(Si? Si) bond activation were analyzed by DFT calculations. These results provide evidence for the intermolecular oxidative addition of σ(Si? Si) bonds to gold and open promising perspectives for the development of new gold‐catalyzed redox transformations.     

Dehydrogenative Meyer–Schuster‐Like Rearrangement: A Gold‐Catalyzed Reaction Generating an Alkyne

Easily accessible propargylic esters are converted to the inverted alkynyl ketones in an oxidative gold‐catalyzed reaction. Gagosz’s catalyst in combination with PhI(OAc)₂ is the best system for this conversion and 18 examples with yields up to 80 % are reported. The results indicate that the triple bond in the product is formed by elimination from a vinylgold intermediate. In a formal sense the new conversion overall is a dehydrogenative Meyer–Schuster rearrangement.     

Zn2+‐Regulated Self‐Sorting and Mixing of Phosphates and Carboxylates on the Surface of Functionalized Gold Nanoparticles

Herein, we describe the self‐sorting of phosphate‐ and carboxylate‐containing molecules on the surface of monolayer‐protected gold nanoparticles. Self‐sorting is driven by selective interactions between the phosphate probe and Zn²⁺ complexes in one monolayer; these interactions force the carboxylate probe to move to a second type of nanoparticle. This process effectively separates the probes and causes their localization in well‐defined spaces surrounding the nanoparticles. The removal/addition of Zn²⁺ metal ions from the system is used to convert the system from an ordered to a disordered state and vice versa. The possibility to control the location and transport of populations of molecules in a complex mixture creates new perspectives for the development of innovative complex catalytic systems that mimic nature.     

One‐Pot Synthesis of 2,5‐Dihydropyrroles from Terminal Alkynes,Azides, and Propargylic Alcohols by Relay Actions of Copper,Rhodium, and Gold

Relay actions of copper, rhodium, and gold formulate a one‐pot multistep pathway, which directly gives 2,5‐dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper‐catalyzed 1,3‐dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1‐sulfonyl‐1,2,3‐triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α‐allenyl‐α‐amino ketones. Finally, a gold catalyst prompts 5‐endo cyclization to produce 2,5‐dihydropyrroles.     

Gold‐Catalyzed Cycloisomerization of 1,6,8‐Dienyne Carbonates and Esters to cis‐Cyclohepta‐4,8‐diene‐Fused Pyrrolidines

A synthetic approach that provides access to cis‐cyclohepta‐4,8‐diene‐fused pyrrolidines efficiently through Au^I‐catalyzed cycloisomerization of 1,6,8‐dienyne carbonates and esters at a low catalyst loading of 2 mol % is reported. Starting carbonates and esters with a pendant alkyl group on the terminal alkenyl carbon center were found to favor tandem 1,2‐acyloxy migration/cyclopropanation followed by Cope rearrangement of the resulting cis‐3‐azabicyclo[3.1.0]hexane intermediate. On the other hand, substrates containing a terminal diene or starting materials in which the distal alkene moiety bears a phenyl substituent were observed to undergo competitive but reversible 1,3‐acyloxy migration prior to the nitrogen‐containing bicyclic ring formation. The delineated reaction mechanism also provides experimental evidence for the reversible interconversion between the oft‐proposed organogold intermediates obtained in this step of the tandem process.     

1,2‐N‐Migration in a Gold‐Catalysed Synthesis of Functionalised Indenes by the 1,1‐Carboalkoxylation of Ynamides

Unique α‐hemiaminal ether gold carbene intermediates were accessed by a gold‐catalysed 1,1‐carboalkoxylation strategy and evolved through a highly selective 1,2‐N‐migration. This skeletal rearrangement gave functionalised indenes, and isotopic labelling confirmed the rare C?N bond cleavage of the ynamide moiety. The effect of substituents on the migration has been explored, and a model is proposed to rationalise the observed selectivity.