Cu-Catalyzed iminative hydroolefination of unactivated alkynes en route to 4-imino-tetrahydropyridines and 4-aminopyridines

Current Market Potential and Prospects of Copper-based Pyridine Derivatives: A Review

Nicotine, minodronic acid, nicotinamide (niacin), zolpidem, zolimidine, and other pyridine-based chemicals play vital roles in medicine and biology. Pyridinecontaining drugs are widely available on the market to treat a wide range of human ailments. As a result of these advances, pyridine research is continually expanding, and there are now higher expectations for how it may aid in the treatment of numerous ailments. This evaluation incorporates data acquired from sources, like PubMed, to provide a thorough summary of the approved drugs and bioactivity data for compounds containing pyridine. Most of the reactions discussed in this article will provide readers with a deeper understanding of various pyridine-related examples, which is necessary for the creation of copper catalysis-based synthetic processes that are more accessible, secure, environmentally friendly, and practical, and that also have higher accuracy and selectivity. This paper also discusses significant innovations in the multi-component copper-catalyzed synthesis of N-heterocycles (pyridine), with the aim of developing precise, cost-effective, and environmentally friendly oxygenation and oxidation synthetic methods for the future synthesis of additional novel pyridine base analogs. Therefore, the review article will serve as a novel platform for researchers investigating copperbased pyridine compounds.

Copper-Catalyzed One-Pot Synthesis of N-Sulfonyl Amidines from Sulfonyl Hydrazine, Terminal Alkynes and Sulfonyl Azides

N-Sulfonyl amidines are developed from a Cu-catalyzed three-component reaction from sulfonyl hydrazines, terminal alkynes and sulfonyl azides in toluene at room temperature. Particularly, the intermediate N-sulfonylketenimines was generated via a CuAAC/ring-opening procedure and took a nucleophilic addition with the weak nucleophile sulfonyl hydrazines. In addition, the stability of the product was tested by a HNMR spectrometer.

Preparation of 1,2-substituted benzimidazoles via a copper-catalyzed three component coupling reaction

1,2-Substituted benzimidazoles were prepared by simply stirring a mixture of copper catalysts, N-substituted o-phenylenediamines, sulfonyl azides and terminal alkynes. Particularly, the intermediate N-sulfonylketenimine occurred with two nucleophilic addition and the sulfonyl group was eliminated via cyclization. In a way, sulfonyl azides and copper catalysts activated the terminal alkynes to synthesize benzimidazoles.

A facile access to N-sulfonylthioimidates and their use for the transformation to 3,4-dihydroquinazolines

N-Sulfonylthioimidates can be efficiently synthesized through one-pot three-component coupling of terminal alkynes, sulfonyl azides, and thiols by using a copper(i) catalyst in the presence of 4-dimethylaminopyridine. The proposed reaction is characterized by mild reaction conditions and tolerance of diverse functional groups. Additionally, the crucial pharmacophore of 3,4-dihydroquinazolines was synthesized using a one-pot synthetic strategy from N-sulfonylthioimidates.

Copper (triazole-5-yl)methanamine complexes onto MCM-41: the synthesis of pyridine-containing pseudopeptides through the 6-endo-dig cyclization of 1,5-enynes

An efficient approach for the synthesis of immobilized copper (triazole-5-yl)methanamine complexes onto MCM-41 (Cu@TZMA@MCM-41), as a novel recyclable nanocatalyst, is described. This nanocatalyst was used for the synthesis of pyridine-containing pseudopeptides through a sequential Ugi/nucleophilic addition/1,5-enyne cyclization reaction and elicited good-to-excellent yields. The nanocatalyst was fully characterized by SEM, EDS, TEM, BET, ICP-OES, TGA, and XRD techniques. Furthermore, the catalyst was recovered by simple filtration and could be used for at least 5 cycles without significant loss of activity.

Three-Component Approach to Pyridine-Stabilized Ketenimines for the Synthesis of Diverse Heterocycles

Ketenimines are versatile synthetic intermediates capable of performing novel transformations in organic synthesis. They are normally generated in situ due to their inherent instability and high level of reactivity. Herein, we report pyridine-stabilized ketenimine zwitterionic salts, which are prepared through click chemistry from readily accessible alkynes and sulfonyl azides. To demonstrate their synonymous reactivity to ketenimines, these salts have been utilized in a cascade sequence to access highly functionalized quinolines including the core structures of an antiprotozoal agent and the potent topoisomerase inhibitor Tas-103.

Metal-Free Method for Direct Synthesis of Functionalized β-Ketoenamines

A new method for direct synthesis of β-ketoenamines was developed by a BF₃·OEt₂-catalyzed cyclization of 1-iodoalkyne and α-keto acid followed by an amine-mediated ring-opening in one pot. Its metal-free conditions allowed the easy synthesis of those products bearing the transition metal-sensitive functional groups. Its three-component process achieved wide range of functionalized products.

An effective preparation of both 1,3-diketones and nitriles from alkynones with oximes as hydroxide sources

An effective phosphine-catalyzed protocol has been established for the syntheses of 1,3-diketones and nitriles from alkynones with oximes as hydroxide surrogates. This method features the use of a phosphine catalyst, compatibility with various functional groups and ambient temperature, which makes this approach very practical. A plausible mechanism was proposed.

One-Pot Synthesis of 4-Sulfonyliminotetrahydropyrimidin-2-one Derivatives through a Copper-Catalyzed Tandem Reaction

A novel and efficient synthesis of 4-iminotetrahydropyrimidin-2-one derivatives was developed through a Cu(I)-catalyzed three-component tandem reaction employing propargylamines, isocyanates, and sulfonyl azides as starting materials. A wide range of polysubstituted 4-sulfonyliminotetrahydropyrimidin-2-ones, which might be useful in biological chemistry and medicinal science, were conveniently and efficiently assembled in one pot.

A nickel-catalyzed anti-carbometallative cyclization of alkyne–azides with organoboronic acids: synthesis of 2,3-diarylquinolines

An anti-carbonickelative cyclization via reversible alkenylnickel E/Z isomerization of 2-azido phenyl propargyl alcohols with aryl boronic acids is achieved using Ni(acac)₂ as the catalyst to access 2,3-diaryl quinolines.

A copper-catalyzed three component reaction of aryl acetylene, sulfonyl azide and enaminone to form iminolactone via 6π electrocyclization

We developed a copper-catalyzed three component reaction of aryl acetylene, enaminone and sulfonyl azide to construct iminolactone via copper-catalyzed alkyne–azide cycloaddition (CuAAC), Michael addition of metalated ketenimine followed by elimination and 6π electrocyclization.

Base-promoted C–C bond cleavage for the synthesis of 2,3,4-trisubstituted pyrroles from N-propargyl β-enaminones

The synthesis of 2,3,4-trisubstituted pyrroles via base-promoted C–C bond cleavage reaction of N-propargyl β-enaminones is reported.

Copper-Promoted Regioselective Intermolecular Diamination of Ynamides: Synthesis of Imidazo[1,2-a]pyridines

A facile access to 3-heterosubstituted (3-oxazolidinonyl/indolyl/phenoxy) imidazo[1,2-a]pyridines from readily available 2-aminopyridines and electron-rich (internally activated) alkynes like ynamides/ynamines/ynol ethers is achieved via Cu(OTf)2-mediated intermolecular diamination under aerobic conditions. The reaction is highly regioselective, owing to internal electron bias, and thus led to a single regioisomer with heterosubstitution at C3.

Copper-Catalyzed Sulfonyl Azide-Alkyne Cycloaddition Reactions: Simultaneous Generation and Trapping of Copper-Triazoles and -Ketenimines for the Synthesis of Triazolopyrimidines

First simultaneous generation and utilization of both copper-triazole and -ketenimine intermediates in copper-catalyzed sulfonyl azide-alkyne cycloaddition reactions is achieved for the one-pot synthesis of triazolopyrimidines via a novel copper-catalyzed multicomponent cascade of sulfonyl azides, alkynes, and azirines. Significantly, the reaction proceeds under very mild conditions in good yields.

Ni-Catalyzed regio- and stereoselective addition of arylboronic acids to terminal alkynes with a directing group tether

Addition of arylboronic acids to directing group tethered acetylenes in a regio and stereoselective manner using an inexpensive catalytic system is achieved for the first time to access highly sought after allyl/homoallyl alcohol/amine units.

Regioselective three-component synthesis of 2,3-disubstituted quinolines via the enaminone modified Povarov reaction

The enaminone modified three-component Povarov reactions enable the regioselective synthesis of 2,3-disubstituted quinolines.

A stereoselective thiocyanate conjugate addition to electron deficient alkynes and concomitant cyclization to N,S-heterocycles

A regio- and stereoselective thiocyanate addition to ynones and the concomitant cyclizations of resultant vinyl thiocyanate to access thio-aza heterocycles are achieved using KSCN in AcOH without the need of any metal catalyst.

Base-catalyzed cascade synthesis of 2,3-dihydrofuro[2,3-b]pyridines and 2,3-dihydro-1H-pyrrolo[2,3-b]pyridines from N-propargylic β-enaminones

A novel protocol to prepare dihydrofuropyridine and dihydropyrrolopyridine derivatives from KOH-catalyzed reactions between N-propargylic β-enaminones and arylaldehydes or N-sulfonyl imines has been developed.