Water-Promoted Synthesis of Enaminones: Mechanism Investigation and Application in Multicomponent Reactions

Conjugated bis(enaminones) as effective templates for rotaxane assembly and their post-synthetic modifications

The development of efficient methods for the synthesis of mechanically interlocked compounds is currently considered a major challenge in supramolecular chemistry. Twofold vinylogous fumaramides, a class of conjugated bis(enaminones), successfully achieve the assembly of hydrogen-bonded amide-based rotaxanes, with a templating ability comparable to that of their parent fumaramide-based systems, showcasing full conversions and impressive yields up to 92%. Computational calculations offer a compelling explanation for the remarkable efficiency of these bis(enaminones) in driving the synthesis of unprecedented rotaxanes. The reactivity of these interlocked species was thoroughly investigated, revealing that a one-step double stopper-exchange process can be successfully performed while preserving the mechanical bond. This approach facilitates the formation of controllable rotaxanes, including a three-station molecular shuttle, whose assembly via a clipping methodology is highly unselective. The internal translational motion of this latter species has been successfully controlled in a reversible way by means of a cycloaddition/retrocycloaddition sequence.

Oxidative Free-Radical C(sp2)-H Bond Chlorination of Enaminones with LiCl: Access to Highly Functionalized α-Chlorinated Enaminones

An oxidative free-radical C(sp2)-H bond chlorination strategy of enaminones has been developed by using LiCl as a chlorinating reagent and K2S2O8 as an oxidant. This transformation provides a new and straightforward synthetic methodology to afford highly functionalized α-chlorinated enaminones with a Z-configuration in good to excellent yields.

The most Recent Compilation of Reactions of Enaminone Derivatives with various Amine Derivatives to Generate Biologically Active Compounds

Heterocyclic derivatives serve as the fundamental components of both natural and synthetic drugs. Enaminones play a crucial role as foundational units in the synthesis of numerous bioactive heterocyclic compounds, including pyrazoles, pyridines, oxazoles, isoxazoles, as well as fused heterocyclic structures like indoles, carbazoles, quinolines, acridines, and phenanthridines. These diverse heterocyclic rings are well-known for their various therapeutic activities, encompassing anticancer, anti-inflammatory, antimicrobial, antidepressant, and antiviral properties. By reacting with nitrogenbased nucleophiles, enaminones can generate bioactive azoles, azines, and their fused systems. This study focuses on the recent advancements in enaminone reactions with (a) nitrogen-based nucleophiles, such as aliphatic amines, derivatives of aniline, heterocyclic amines, hydroxylamine, hydrazine derivatives, guanidine derivatives, urea, and thiourea derivatives, and (b) nitrogen-based electrophiles, such as diazonium salts. These reactions have led to the synthesis of a wide range of bioactive fused heterocyclic compounds from 2010 to the end of 2022.

Synthesis of 4-Alkylated 1,4-Dihydropyridines: Fe(II)-Mediated Oxidative Cascade Cyclization Reaction of Cyclic Ethers with Enaminones

Syntheses of highly functionalized 4-alkylated 1,4-dihydropyridines (1,4-DHPs) from cyclic ethers and enaminones via iron(II)-mediated oxidative free radical cascade C(sp3)-H bond functionalization/C(sp3)-O bond cleavage/cyclization reaction have been first developed. This novel synthetic strategy offers an alternative method for the construction of 1,4-DHPs by using esters as the C4 sources, as well as expands the application of ethers in heterocycle synthesis.

Fe3O4@Glycerol-Cu as a novel heterogeneous magnetic nanocatalyst for the green synthesis of 2-amino-4H-chromenes

In the present study, the Fe₃O₄@Glycerol-Cu complex supported magnetically as a nanoparticle was prepared by grafting. Firstly, Fe₃O₄ NPs were synthesized by FeCl₃.6H₂O and FeCl₂.4H₂O according to the reported method, and subsequently, the prepared MNP with 3-chloropropyltrimethoxysilane. After that, the support-glycerol was functionalized on the surface of MNP-(CH₂)₃Cl for graft and stabilization of copper metal. Our purpose is to use the Fe₃O₄@Glycerol-Cu as a green, recoverable, novel, and affordable nanocatalyst in the effective synthesis of 2-amino-4H-chromenes. FT-IR, XRD, TGA, BET, VSM, TEM, and SEM-EDX techniques were examined to characterize this nanocatalyst. This result demonstrates that copper and organic compounds have appropriately reacted, with the support of MNP-(CH₂)₃Cl, and the crystalline structure have preserved in the MNP-(CH₂)₃Cl/Glycerol-Cu nanocatalyst confirmed the formation of the base Cu complex grafted on the surface of the nanoparticles. Finally, as can be seen, the nanoparticle size is 5-15 nm. This heterogeneous nanocatalyst illustrated excellent recyclable behavior, and can be used several times without notable reduction of its activity.

Versatile Synthetic Platform for 1,2,3-Triazole Chemistry

1,2,3-Triazole scaffolds are not obtained in nature, but they are still intensely investigated by synthetic chemists in various fields due to their excellent properties and green synthetic routes. This review will provide a library of all synthetic routes used in the past 21 years to synthesize 1,2,3-triazoles and their derivatives using various metal catalysts (such as Cu, Ni, Ru, Ir, Rh, Pd, Au, Ag, Zn, and Sm), organocatalysts, metal-free as well as solvent- and catalyst-free neat syntheses, along with their mechanistic cycles, recyclability studies, solvent systems, and reaction condition effects on regioselectivity. Constant developments indicate that 1,2,3-triazoles will help lead to future organic synthesis and are useful for creating molecular libraries of various functionalized 1,2,3-triazoles.

Metal-free synthesis of β-aminoketones by the reductive hydroamination of ynones

This study describes a cascade method for the synthesis of β-aminoketones through the reductive hydroamination of alkynes under very mild metal-free conditions. It allows for the rapid conversion of ynones and amines into corresponding β-aminoketones with a broad substrate scope and diverse functionalities. This straightforward and easy-to-handle reaction process can be successfully applied for the synthesis of Proroxan and Propipocaine, offering a potential option for the synthesis of drug molecules with the β-aminoketone skeleton.

Synthesis of 3,3-Dihalogenated 2-Aminochromanones via Tandem Dihalogenation and Cyclization of o-Hydroxyarylenaminones with NXS (X = Cl or Br)

An unprecedented method for the synthesis of dichlorinated and dibrominated 2-amino-substituted chromanones is developed by employing enaminones and NCS/NBS as starting materials under microwave irradiation. The reactions proceed quickly to deliver products without using any catalyst or additive, thus providing practical access to 3,3-dihalogenated 2-aminochromanones.

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

A comprehensive account of recent advances in the synthesis of imidazopyridines, assisted through transition-metal-catalyzed multicomponent reactions, C-H activation/functionalization and coupling reactions are highlighted in this review article. The basic illustration of this review comprises of schemes with concise account of explanatory text. The schemes depict the reaction conditions along with a quick look into the mechanism involved to render a deep understanding of the catalytic role. At some instances optimizations of certain features have been illustrated through tables, i.e., selectivity of catalyst, loading of the catalyst and percentage yield with different substrates. Each of the reported examples has been rigorously analyzed for reacting substrates, reaction conditions and transition metals used as the catalyst. This review will be helpful to the chemists in understanding the challenges associated with the reported methods as well as the future possibilities, both in the choice of substrates and catalysts. This review would be quite appealing to a wider range of organic chemists in academia and industrial R&D sectors working in the field of heterocyclic syntheses. In a nutshell, this review will be a guiding torch to envisage: (i) the role of various transition metals in the domain dedicated towards method development and (ii) for the modifications needed thereof in the R&D sector.

DMFDMA catalyzed synthesis of 2-((Dimethylamino)methylene)-3,4-dihydro-9-arylacridin-1(2H)-ones and their derivatives: in-vitro antifungal, antibacterial and antioxidant evaluations

A series of 3,4-dihydro-9-arylacridin-1(2H)-ones was synthesized and enaminone function was introduced at the C-2 position using DMFDMA catalyst which in turn successfully converted into pyrazole, isoxazol, 1-phenyl-1H-pyrazole by treating it with reagents such as hydrazine, hydroxylamine and phenylhydrazine. These newly synthesized compounds were evaluated for their antibacterial activity against a series of Gram-Positive bacteria including Staphylococcusaureus, Bacilluscereus, StaphylococcusaureusMLS16 and Gram-Negative bacteria including Klebsiellaplanticol, Escherichiacoliand Pseudomonasaeruginosaand also against fungal strains including Candidaalbicans, Candidaparapsilosis, Candidaglabrata, Candidaaaseri, Aspergillusnigerand Issatchenkiahanoiensis. The compounds3aand6aexhibited considerable antifungal activity (MIC value 0.007 and 0.006 μM) against Candidaalbicansand Aspergillusnigerrespectively. The compound4ashowed excellent antibacterial activity towards EscherichiaColi(MIC = 0.003 μM) and the compound5afound to show prominent DPPH radical scavenging activity with EC50value 16.85±1.5μg mL−1.

Tunable Synthesis of Disulfide-Functionalized Enaminones and 1,4-Thiazines via the Reactions of Enaminones and β-Aminoethanethiol

The reactions of β-aminoethanethiol with N,N-dimethyl enaminones are performed to selectively provide disulfide-functionalized enaminones and 1,4-thiazines. By performing the reaction in water and catalyst-free conditions, the transamination and oxidative S-S coupling between the two substrates take place to give disulfide-functionalized enaminones. On the other hand, by using identical starting materials, the employment of the CuI catalyst in dimethyl sulfoxide enables the selective generation of 1,4-thiazines via tandem transamination and C(sp2)-H bond thiolation.

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.

Base-Promoted Synthesis of N-Substituted 1,2,3-Triazoles via Enaminone-Azide Cycloaddition Involving Regitz Diazo Transfer

The domino reactions between NH-based secondary enaminones and tosyl azide have been developed for the synthesis of various N-substituted 1,2,3-triazoles by employing t-BuONa as the base promoter. Through a key Regitz diazo-transfer process with tosyl azide, the reactions proceed efficiently at room temperature with good substrate tolerance.

Synthesis and biological evaluation of new pyranopyridine derivatives catalyzed by guanidinium chloride-functionalized γ-Fe2O3/HAp magnetic nanoparticles

Herein, we described the synthesis of γ-Fe₂O₃@HAP-GndCl MNPs as an efficient and recyclable nanocatalyst for synthesis of new pyranopyridine derivatives under solvent-free condition and then evaluated for theirs antioxidant and antifungal activities.

Synthesis of β,β-diaryl propiophenones via palladium-catalyzed domino arylboronation, elimination and enone hydroarylation of enaminones

The first example of a domino reaction involving enaminone C–N conversion-based arylation has been realized as an efficient new route toward the synthesis of β,β-diaryl propiophenones.

Regioselective three-component reactions of enaminones, 2-aminopyridines and enals for the synthesis of 1,2-dihydropyridines

A novel regioselective, metal-free and broadly applicable three-component approach for the synthesis of 1,2-dihydropyridines has been established.

ZnCl2-catalyzed chemoselective cascade reactions of enaminones with 2-furylcarbinols: a versatile process for the synthesis of cyclopenta[b]pyrrole derivatives

A ZnCl₂-catalyzed cascade reaction of enaminones with 2-furylcarbinols offers a chemo- and diastereo-selective access to functionalized cyclopenta[b]pyrrole derivatives.