Gold(III) (C^N) complex-catalyzed synthesis of propargylamines via a three-component coupling reaction of aldehydes, amines and alkynes

Gold and silver catalysis: from organic transformation to bioconjugation

A summary of gold (including AuNPs, Au(i) and Au(iii) complexes) and silver(i) catalysis and their application in bioconjugation reactions.

Bis-cyclometallated gold(III) complexes as efficient catalysts for synthesis of propargylamines and alkylated indoles

Stable bis-cyclometallated gold(III) complexes were developed as efficient catalysts for organic transformation reactions by using two strategies: (1) construction of distorted square planar gold(III) complexes and (2) dual catalysis by gold(III) complexes and silver salts.

Silver and gold-catalyzed multicomponent reactions

Silver and gold salts and complexes mainly act as soft and carbophilic Lewis acids even if their use as σ-activators has been rarely reported. Recently, transformations involving Au(I)/Au(III)-redox catalytic systems have been reported in the literature. In this review we highlight all these aspects of silver and gold-mediated processes and their application in multicomponent reactions.

Mild gold-catalyzed three-component dehydrogenative coupling of terminal alkynes to amines and indole-2-carboxaldehyde

A mild gold-catalyzed three-component dehydrogenative coupling of terminal alkynes to amines and indole-2-carboxaldehyde has been developed, which provides a practical synthetic strategy for the synthesis of indole derivatives.

Gold-catalyzed three-component annulation: efficient synthesis of highly functionalized dihydropyrazoles from alkynes, hydrazines, and aldehydes or ketones

Polysubstituted dihydropyrazoles were directly obtained by a gold-catalyzed three-component annulation. This reaction consists of a Mannich-type coupling of alkynes with N,N'-disubstituted hydrazines and aldehydes/ketones followed by intramolecular hydroamination. Cascade cyclization using 1,2-dialkynylbenzene derivatives as the alkyne component was also performed producing fused tricyclic dihydropyrazoles in good yields.

Enantioselective synthesis of cyclic carbamimidates via a three-component reaction of imines, terminal alkynes, and p-toluenesulfonylisocyanate using a monophosphine gold(I) catalyst()

A racemic Au(I)-catalyzed three-component reaction has been developed to prepare cyclic carbamimidates from imines, terminal alkynes, and sulfonylisocyanates. This reaction exploits the carbophilic π-acidity of gold catalysts to first activate an alkyne toward deprotonation and secondly, to activate the internal alkyne generated toward intramolecular O-cyclization. Unlike similar previously reported multicomponent gold-catalyzed reactions, the stereocenter generated during the alkynylation is preserved in the product. This trait was exploited by developing an enantioselective variant, using an unusual trans-1-diphenylphosphino-2-arylsulfamidocyclohexane ligand. Moderate to excellent levels of enantioselectivity were obtained using a variety of N-arylbenzylidene anilines (41-95% ee, 18 examples).

The development of catalytic nucleophilic additions of terminal alkynes in water

One of the major research endeavors in synthetic chemistry over the past two decades is the exploration of synthetic methods that work under ambient atmosphere with benign solvents, that maximize atom utilization, and that directly transform natural resources, such as renewable biomass, from their native states into useful chemical products, thus avoiding the need for protecting groups. The nucleophilic addition of terminal alkynes to various unsaturated electrophiles is a classical (textbook) reaction in organic chemistry, allowing the formation of a C-C bond while simultaneously introducing the alkyne functionality. A prerequisite of this classical reaction is the stoichiometric generation of highly reactive metal acetylides. Over the past decade, our laboratory and others have been exploring an alternative, the catalytic and direct nucleophilic addition of terminal alkynes to unsaturated electrophiles in water. We found that various terminal alkynes can react efficiently with a wide range of such electrophiles in water (or organic solvent) in the presence of simple and readily available catalysts, such as copper, silver, gold, iron, palladium, and others. In this Account, we describe the development of these synthetic methods, focusing primarily on results from our laboratory. Our studies include the following: (i) catalytic reaction of terminal alkynes with acid chloride, (ii) catalytic addition of terminal alkynes to aldehydes and ketones, (iii) catalytic addition of alkynes to C=N bonds, and (iv) catalytic conjugate additions. Most importantly, these reactions can tolerate various functional groups and, in many cases, perform better in water than in organic solvents, clearly defying classical reactivities predicated on the relative acidities of water, alcohols, and terminal alkynes. We further discuss multicomponent and enantioselective reactions that were developed. These methods provide an alternative to the traditional requirement of separate steps in classical alkyne reactions, including the pregeneration of metal acetylides with stoichiometric, highly basic reagents and the preprotection of sensitive functional groups. Accordingly, these techniques have greatly enhanced overall synthetic efficiencies and furthered our long-term objective of developing Grignard-type reactions in water.

Efficient and General Synthesis of 3-Aminoindolines and 3-Aminoindoles via Copper-Catalyzed Three Component Coupling Reaction

An efficient three component coupling (TCC) reaction toward a variety of 3-aminoindoline and 3-aminoindole derivatives has been developed. This cascade transformation proceeds via the copper-catalyzed coupling reaction between 2-aminobenzaldehyde, secondary amine, and alkyne leading to propargylamine intermediate, which, under the reaction conditions, undergoes cyclization into the indoline core. The latter, upon treatment with a base, smoothly isomerizes into indole. Alternatively, indole can directly be synthesized in a one-pot sequential reaction.

1H, 13C, 15N and 195Pt NMR studies of Au(III) and Pt(II) chloride organometallics with 2-phenylpyridine

(1)H, (13)C, (15)N and (195)Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2')-chelated, deprotonated 2-phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl(2)], trans(N,N)-[Pt(2ppy*)(2ppy)Cl] and trans(S,N)-[Pt(2ppy*)(DMSO-d(6))Cl] (formed in situ upon dissolving [Pt(2ppy*)(micro-Cl)](2) in DMSO-d(6)) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective (1)H, (13)C and (15)N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Delta(1H)(coord) = delta(1H)(complex) - delta(1H)(ligand), Delta(13C)(coord) = delta(13C)(complex) - delta(13C)(ligand), Delta(15N)(coord) = delta(15N)(complex) - delta(15N)(ligand)), as well as (195)Pt chemical shifts and (1)H-(195)Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen-adjacent H(6) protons and metallated C(2') atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds.