Gold catalysis: domino reaction of en-diynes to highly substituted phenols

Environmentally Friendly Synthesis of Highly Substituted Phenols Using Enallenoates and Grignard Reagents

We developed an efficient and environmentally friendly methodology for selectively synthesizing highly substituted phenols using readily available enallenoates and Grignard reagents. This method consistently yields good to excellent results across over 60 examples, demonstrating the substrate scope and the exploration of phenol product derivatization, further extending the method's utility.

[2+2+1+1] Cycloaddition for de novo Synthesis of Densely Functionalized Phenols

A unique benzannulation strategy for regioselective de novo synthesis of densely functionalized phenols is described. Through metal-mediated formal [2+2+1+1] cycloaddition of two different alkynes and two molecules of CO, a series of densely functionalized phenols were obtained. The benzannulation strategy allows efficient regioselective installation up to five different substituents on a phenol ring. The resulting phenols have a substitution pattern different from those obtained from Dötz and Danheiser benzannulations.

Tandem cyclocondensation of 1,3-bis-sulfonylpropan-2-ones with arylaldehydes. One-pot synthesis of tris-sulfonyl 3-arylphenols

One-pot tandem piperidinium acetate-mediated cyclocondensation of 1,3-bis-sulfonylpropan-2-ones with arylaldehydes generates tris-sulfonyl 3-arylphenols in moderate to good yields in refluxing toluene under easy-operational reaction conditions.

Gold(I)-Catalyzed Reactivity of Furan-ynes with N-Oxides: Synthesis of Substituted Dihydropyridinones and Pyranones

The reactivity of "furan-ynes" in combination with pyridine and quinoline N-oxides in the presence of a Au(I) catalyst, has been studied, enabling the synthesis of three different heterocyclic scaffolds. Selective access to two out of the three possible products, a dihydropyridinone and a furan enone, has been achieved through the fine-tuning of the reaction conditions. The reactions proceed smoothly at room temperature and open-air, and were further extended to a broad substrate scope, thus affording functionalized dihydropyridinones and pyranones.

Gold Catalysis and Furans: A Powerful Match for Synthetic Connections

This review summarizes the advances made on the synthesis and functionalization of furans via gold catalysis during the period between 2016 and 2020. A separate section is dedicated to the tandem gold-catalyzed synthesis and functionalization of furans.

1 Introduction

2 Gold-Catalyzed Synthesis of Furans

2.1 Cycloisomerizations of Alkynyl and Cumulenyl Alcohols

2.2 Cycloisomerizations of Alkynyl and Allenyl Ketones

2.3 Reactions with External Oxidants

2.4 Miscellaneous

3 Gold-Catalyzed Functionalization of Furans

3.1 Cycloadditions

3.2 Furan Ring Decorations

3.3 Reactions Involving Furan Ring Opening

4 Gold-Catalyzed Tandem Synthesis and Functionalization of Furans­

4.1 Cycloisomerizations Followed by Gold-Catalyzed Cycloaddition

4.2 Cycloisomerizations to a Gold 1,3- or 1,4-Dipole and Intermolecular Annulation

4.3 Cycloisomerizations to a Gold Carbene and Intermolecular Trapping

5 Conclusion

[2 + 2 + 2] Cyclotrimerization with Propargyl Halides as Copartners: Formal Total Synthesis of the Antitumor Hsp90 Inhibitor AT13387

Heat shock protein 90 (Hsp90) inhibitors play a remarkable role in cellular growth, and they were shown to exhibit antitumor activity. The Hsp90 inhibitor AT13387 (onalespib) is under clinical trials for the treatment of refractory gastrointestinal stromal tumors. Recently, it was demonstrated that this compound also exhibits inhibition against bladder cancer. Here, we report isoindoline- and isoindolinone-based (halomethyl)benzenes via a [2 + 2 + 2] cyclotrimerization in the presence of catalytic amounts of Mo(CO)₆. This strategy has been extended to synthesize the key precursor of the Hsp90 inhibitor, AT13387.

Synthesis of C2-Symmetric gem-Difluoromethylenated Angular Triquinanes

A synthesis of symmetrical gem-difluoromethylenated angular triquinanes is described. The synthetic strategy involved sequential fluoride-catalyzed nucleophilic addition of PhSCF₂SiMe₃ (1) to 2,2-diallylated or 2,2-dipropargylated indane-1,3-diones 2 followed by stereoselective radical cyclization of the resulting adducts 3 to provide the cyclized gem-difluoromethylenated diquinanes 4 as a mixture of stereoisomers. Repeated addition of 1 to 4 followed by cyclization resulted in the stereoselective synthesis of the desired C₂-symmetric gem-difluoromethylenated angular triquinanes 6 in good yields with high stereoselectivity.

Synthesis of 2-aminopyridines via ruthenium-catalyzed [2+2+2] cycloaddition of 1,6- and 1,7-diynes with cyanamides: scope and limitations

A direct route to access 2-aminopyridines using Ru-catalyzed-[2+2+2] cycloaddition of 1,n-diynes with cyanamides is described in excellent yields and regioselectivities.

On the Gold-Catalyzed Generation of Vinyl Cations from 1,5-Diynes

Conjugated 1,5-diynes bearing two aromatic units at the alkyne termini were converted in the presence of a gold catalyst. Under mild conditions, aryl-substituted dibenzopentalenes were generated. Calculations predict that aurated vinyl cations are key intermediates of the reaction. A bidirectional approach provided selective access to the angular annulated product in high yield, which was explained by calculations.

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.

Enantioselective, Stereodivergent Hydroazidation and Hydroamination of Allenes Catalyzed by Acyclic Diaminocarbene (ADC) Gold(I) Complexes

The gold-catalyzed enantioselective hydroazidation and hydroamination reactions of allenes are presented herein. ADC gold(I) catalysts derived from BINAM were critical for achieving high levels of enantioselectivity in both transformations. The sense of enantioinduction is reversed for the two different nucleophiles, allowing access to both enantiomers of the corresponding allylic amines using the same catalyst enantiomer.

Exploring the gold mine: [Au]-catalysed transformations of enynals, enynones and enynols

This review highlights reactions of enynals, enynones and enynols using gold catalysis which often lead to cycloaddition or cyclisation products.

Gold(i)-catalyzed cycloisomerization of vinylidenecyclopropane-enes via carbene or non-carbene processes

Gold catalyzed cycloisomerization of aromatic ring tethered vinylidenecyclopropane-enes provides a divergent synthetic protocol for the construction of O-containing fused heterocycles through controllable carbene or non-carbene related processes. The carbene induced process features a new amphiphilic strategy to generate a gold carbene via a rearrangement of vinylidenecyclopropane. Whereas, the electronic effect of the ortho-substituents switches the reaction mode onto the non-carbene related process, from which five- or six-membered rings are selectively produced through allyl-migration.

Relationship between the anion/cation relative orientation and the catalytic activity of nitrogen acyclic carbene–gold catalysts

The role of the ligand in determining the ion pair structure of the [(NAC)Au(η²-3-hexyne)]⁺ BF₄⁻ catalysts and how the position of the anion (positions A, B and C) influences their catalytic performance in the intermolecular alkoxylation of alkynes have been studied.

Carbopalladation of bromoene-alkynylsilanes: mechanistic insights and synthesis of fused-ring bicyclic silanes and phenols

Palladium-catalyzed cyclizations of silylated bromoenynes lead to bicyclic cyclohexadienes that are precursors to enones and phenols. Novel cyclization pathways and mechanistic insights are also disclosed.