Gold-catalyzed 1,3-transposition of ynones

Gold-Catalyzed Oxidative Cyclization/C-C Bond Cleavage of Ynones with External Nucleophiles: Synthesis of Linear Functionalized N-Tosylamides

A gold-catalyzed oxidative cyclization/nucleophilic addition/C-C bond cleavage reaction of ynones with various nucleophiles has been developed. This methodology allows for the formation of highly functionalized linear N-Ts amides with broad substrate scope, high efficiency, and general tolerance of functional groups. A wide range of nucleophiles such as alcohols, water, and amines including aryl and alkyl amines are compatible with the current method. The C-C triple bond cleavage of the ynone substrate was observed during the process.

Advances in Selected Heterocyclization Methods

This Account summarizes efforts in our group toward synthesis of heterocycles in the past decade. Selected examples of transannulative heterocyclizations, intermediate construction of reactive compounds en route to these important motifs, and newer developments of a radical approach are outlined.

An Approach to Functionally Embellished o-Alkynylbenzoates or Furan-3(2H)-ones from Diynones and DMAD: Controlled Divergence and Product Selectivity

The discovery of reaction regime controlled product diversification in a one-pot reaction between diynones and dimethyl-1,3-acetonedicarboxylate (DMAD) to selectively furnish either functionally unique pentasubstituted o-alkynylbenzoates or fully substituted furan-3(2H)-ones is delineated. The potential of these two versatile platforms to enter new utilitarian chemical space has also been explored.

Synthesis of γ-Pyrones and N-Methyl-4-pyridones via the Au Nanoparticle-Catalyzed Cyclization of Skipped Diynones in the Presence of Water or Aqueous Methylamine

Supported Au nanoparticles on TiO₂ catalyze the hydration/6-endo cyclization of skipped diynones to γ-pyrones in aqueous dioxane, via triple bond activation. The isomeric 3(2H)-furanones which could be formed through a competing and often prevailing 5-exo cyclization pathway using homogeneous ionic Au(I) catalysts were not seen. The reaction does not proceed via the initial 1,3-transposition of the skipped diynones to their corresponding conjugated 1,3-diynone isomers. If aqueous methylamine is added, N-methyl-4-pyridones are exclusively formed in 69-79% yields via an analogous hydroamination/Au-catalyzed 6-endo cyclization pathway.

Gold-Catalyzed Cyclization of Ynones Involving cis-Hydrofunctionalizations: Rapid Assembly of C-, O-, or S-Functionalized Pyrroles by a Single Methodology

A gold-catalyzed cyclization of conjugated ynones with various nucleophiles such as indoles, alcohols, and thiols has been developed. The reaction provides a new and efficient protocol for the synthesis of functionalized pyrroles with wide versatility and functional group compatibility. Remarkably, for indolyl, alkoxy, or sulfenyl pyrroles, all could be constructed efficiently by this single methodology. In addition, cis-hydrofunctionalizations of ynones are involved in these reactions.

Gold-Catalyzed Oxidative Cyclization Involving Nucleophilic Attack to the Keto Group of α,α'-Dioxo Gold Carbene and 1,2-Alkynyl Migration: Synthesis of Furan-3-carboxylates

A multicomponent strategy for the synthesis of functionalized furan-3-carboxylates based on gold-catalyzed oxidative cyclization of diynones with alcohols or water has been developed. Mechanistic studies revealed that a rare nucleophilic attack to the carbonyl group of the α,α'-dioxo gold carbene instead of the carbene center and 1,2-alkynyl group migration were involved in this transformation. This method offers several advantages such as mild conditions, high regio- and chemoselectivity, and wide functional group compatibility.

The mechanism of the gold(I)-catalyzed Meyer-Schuster rearrangement of 1-phenyl-2-propyn-1-ol via 4-endo-dig cyclization

With the aim of rationalizing the experimental counterion- and solvent-dependent reactivity in the gold(i)-catalyzed Meyer-Schuster rearrangement of 1-phenyl-2-propyn-1-ol, a computational mechanistic study unraveled the unexpected formation of a gold-oxetene intermediate via commonly unfavorable 4-endo-dig cyclization triggered by the counterion in low polarity solvents.

Regiodivergent Hydration-Cyclization of Diynones under Gold Catalysis

Skipped diynones, efficiently prepared from biomass-derived ethyl lactate, undergo a tandem hydration-oxacyclization reaction under gold(I) catalysis. Reaction conditions have been developed for a switchable process that allows selective access to 4-pyrones or 3(2H)-furanones from the same starting diynones. Further application of this methodology in the total synthesis of polyporapyranone B was demonstrated.

De Novo Ring-Forming Consecutive Four-Component Syntheses of 4-Pyrazolyl-1,2,3-triazoles from (Triisopropylsilyl)butadiyne as a C4 Building Block

4-Pyrazolyl-1,2,3-triazoles can be readily synthesized in a one-pot fashion and moderate yield by employing a consecutive four-component process consisting of a sequentially Pd-Cu-catalyzed alkynylation-cyclocondensation-desilylation-CuAAC process. Most distinctly, (triisopropylsilyl)butadiyne is employed as a four-carbon building block in this one-pot de novo formation of both heterocyclic moieties.

Where does Au coordinate to N-(2-pyridiyl)benzotriazole: gold-catalyzed chemoselective dehydrogenation and borrowing hydrogen reactions

Pyridyltriazole gold(i) complexes proved to be an efficient precatalyst for the most challenging gold-catalyzed borrowing hydrogen reaction and dehydrogenation of alcohols and amines.

Cu(i)-Catalyzed stereoselective synthesis of trisubstituted Z-enol esters via interrupting the 1,3-O-transposition reaction

An efficient Cu(i)-catalyzed stereoselective synthesis of trisubstituted Z-enol esters via interrupting the 1,3-O-transposition process is reported, which provided a convenient approach to highly functionalized Z-enol esters.

Palladium-catalyzed carbonylative Sonogashira coupling of aryl diazonium salts with formic acid as the CO source: the effect of 1,3-butadiene

An efficient carbonylative cross-coupling of aryl diazonium salts with terminal alkynes using formic acid as the CO source has been developed. And 1,3-butadiene was found to play a crucial role in this transformation.

Gold-catalysed reactions of diynes

In this critical review the reactivity patterns observed with different types of diyne substrates in gold catalysis are discussed. Apart from the many examples from homogeneous catalysis, the few examples from heterogeneous gold catalysis are also included. With a proper arrangement of the two alkynes unique and exciting reactivity patterns like 1,3-carbonyl transpositions, carbene transfer reactions, cascade annulations, macrocyclisations or the formation of gold vinylidene intermediates are observed. These reactions are of interest for organic synthesis, for pharmaceutical and medicinal chemistry and for material science.

Stable yet reactive cationic gold catalysts with carbon based counterions

Widely applicable cationic gold catalysts with a carbon based counterion.