Quinoline: A Novel Solution for Next-Generation Pesticides, Herbicides, and Fertilizers

Quinoline is a nitrogen-containing heterocycle compound widely used in the medical industry for its pharmacological properties, such as its antimalarial, antimicrobial, antiparasitic, anti-inflammatory, and anticancer activities. Beyond its medical significance, quinoline shows promising applications in agriculture as a safe and effective pesticide, herbicide, and fertilizer. This review explores the evolution of quinoline research, beginning with its history and synthesis and transitioning to its biological activities and their relevance in agriculture. It then highlights the potential applications of quinoline in modern agriculture, such as pesticides, herbicides, and fertilizers, for increasing crop yields and resilience while reducing crop waste. Moreover, it discusses formulation strategies that can enhance the efficacy of quinoline. Finally, the review addresses potential challenges, such as toxicity and environmental impact, underscoring the need for further research to harness quinoline's full potential in sustainable agriculture.

Quinoline Synthesis: Nanocatalyzed Green Protocols-An Overview

Heterocyclic compounds are of great interest in our daily lives. They are widely distributed in nature and are synthesized in laboratories. Heterocycles play an important role in the metabolism of all living cells, including vitamins and coenzyme precursors like thiamine and riboflavin. Furthermore, heterocyclic systems are essential building blocks for creating innovative materials with intriguing electrical, mechanical, and biological properties. Also, more than 85% of all biologically active chemical entities comprise a heterocycle. As a result, heterocycle synthesis piqued researchers' curiosity, and in recent decades, chemists have concentrated more on nitrogen-containing cyclic nuclei in structures. Quinoline and its derivatives exhibit several biological functions, including antimicrobial, anticancer, antimalarial, anti-inflammatory, antihypertensive, and antiasthmatic effects. In addition, over a hundred quinoline-based drugs are available to treat a variety of disorders. Because of its biological importance, researchers developed one-pot synthetic methods employing effective acid/base catalysts (Lewis acids, Brønsted acids, and ionic liquids), reagents, and transition-metal-based catalysts. These methods have some downsides, including longer reaction times, harsher reaction conditions, creation of byproducts, costly catalysts, use of hazardous solvents, an unacceptable economic yield, and catalyst recovery. Researchers' focus has switched to creating environmentally friendly and effective methods for the synthesis of quinoline derivatives as a result of these methodologic shortcomings. Because of its special qualities, the use of nanocatalysts or nanocomposites offers an option for the effective synthesis of quinolines. This review focuses on the published research articles on nanocatalysts to synthesize substituted quinoline derivatives. This review covers all contributions until May 2024, focusing on quinoline ring building and mechanistic issues. With the aid of this review, we anticipate that synthetic chemists will be able to develop more effective methods of synthesizing quinolines.

Ts2O Promoted Deoxygenative C-H Dithiocarbonation of Quinoline N-Oxides with Potassium O-Alkyl Xanthates

A simple, efficient, and practical method for the synthesis of S-quinolyl xanthates was developed via Ts2O-promoted deoxygenative C-H dithiocarbonation of quinoline N-oxides with various potassium O-alkyl xanthates. The reaction performed well under transition-metal-free, base-free, and room-temperature conditions with wide substrate tolerance. Employing potassium O-tert-butyl xanthate (tBuOCS2K) as a nucleophile, some valuable quinoline-2-thiones were unexpectedly obtained in a one-pot reaction without any additional base.

Trifluoromethyl-β-dicarbonyls as Versatile Synthons in Synthesis of Heterocycles

Trifluoromethyl group relishes a privileged position in the realm of medicinal chemistry because its incorporation into organic molecules often enhances the bioactivity by altering pharmacological profile of molecule. Trifluoromethyl-β-dicarbonyls have emerged as pivotal building blocks in synthetic organic chemistry due to their facile accessibility, stability and remarkable versatility. Owing to presence of nucleophilic and electrophilic sites, they offer multifunctional sites for the reaction. This review covers a meticulous exploration of their multifaceted role, encompassing an in-depth analysis of mechanism, extensive scope, limitations and wide-ranging applications in diverse organic synthesis, covering the literature from the 21st century. This comprehensive review encapsulates the applications of trifluoromethyl-β-dicarbonyls and their synthetic equivalents as precursors of complex and diverse heterocyclic scaffolds, fused heterocycles and spirocyclic compounds having medicinal and material importance. Their potent synthetic utility in cyclocondensation reactions with binucleophiles, cycloaddition reactions, C-C bond formations, asymmetric multicomponent reactions using classical/solvent-free/catalytic synthesis have been presented. Influence of unsymmetrical trifluoromethyl-β-diketones on regioselectivity of transformation is also reviewed. This review will benefit the synthetic and pharmaceutical communities to explore trifluoromethyl-β-dicarbonyls as trifluoromethyl building blocks for fabrication of heterocyclic scaffolds having implementation into drug discovery programs in the imminent future.

Six-Membered Aromatic Nitrogen Heterocyclic Anti-Tumor Agents: Synthesis and Applications

Cancer stands as a serious malady, posing substantial risks to human well-being and survival. This underscores the paramount necessity to explore and investigate novel antitumor medications. Nitrogen-containing compounds, especially those derived from natural sources, form a highly significant category of antitumor agents. Among these, antitumor agents with six-membered aromatic nitrogen heterocycles have consistently attracted the attention of chemists and pharmacologists. Accordingly, we present a comprehensive summary of synthetic strategies and clinical implications of these compounds in this review. This entails an in-depth analysis of synthesis pathways for pyridine, quinoline, pyrimidine, and quinazoline. Additionally, we explore the historical progression, targets, mechanisms of action, and clinical effectiveness of small molecule inhibitors possessing these structural features.

Copper-Catalyzed Synthesis of N-Fused Quinolines via C(sp3)-H Activation-Radical Addition-Cyclization Cascade

A novel copper-catalyzed cyclization reaction for the synthesis of pyrazolo[1,5-a]quinoline, triazolo[1,5-a]quinoline, and pyrrolo[1,2-a]quinoline derivatives is described. The process is initiated by di-tert-butyl peroxide-mediated C(sp3)-H activation to generate the α-functionalized radical, which supervenes a cascade radical addition/cyclization sequence to access the N-fused quinolines in good yields with broad functional group tolerance.

Copper catalysed oxidative cascade deamination/cyclization of vinyl azide and benzylamine for the synthesis of 2,4,6-triarylpyridines

A highly efficient one-pot method for the synthesis of 2,4,6-triaryl pyridines has been developed via cascade deamination and annulation. Copper triflate and molecular iodine easily promoted the oxidative cyclization reaction of vinyl azide and benzylamine to access a wide variety of substituted pyridine substrates under an oxygen atmosphere. The presence of benzyl amine enables the cyclization process by providing the aryl functionality and the nitrogen source. Moreover, a broad range of substrates with good functional group tolerance, avoidance of external oxidants, excellent product yields, operational simplicity and mild conditions are the notable advantages of the present protocol.

FeCl3-Catalyzed Decyanative [4 + 2] Annulation of α-Aminonitriles with Alkynes: Access to 2,4-Diaryl Quinolines in Batch and Continuous-Flow Processes

FeCl₃-catalyzed decyanation of α-aminonitriles followed by a [4 + 2] annulation with terminal alkynes has been developed to synthesize 2,4-diaryl quinolines. A broad range of aniline, aldehyde, and arylacetylene derivatives were well tolerated to access 2,4-diaryl quinolines in moderate to good yields. The control experiment studies suggested that the reaction proceeds through a nonradical pathway involving Povarov-type [4 + 2] annulation from the in situ generated iminium species. The synthetic application of this strategy (i) includes gram-scale synthesis and (ii) a continuous-flow process for a few representative compounds in a shorter reaction time (22 min) and (iii) worked well with styrene as a proof of concept.

Halogen cation-promoted and solvent-regulated electrophilic cyclization for the regioselective synthesis of 3-haloquinolines and 3-halospirocyclohexadienones

A novel approach for the production of halogen cations through the reaction of halogens with silver ions is described in this paper. On this basis, the regioselective synthesis of 3-haloquinolines and 3-halospirocyclohexadienones is realized through solvent regulation. The gram-scale reaction and the compatibility of complex substrates demonstrate the synthetic potential of this protocol, which will be an appealing strategy in organic synthesis.

Mechanistic Insights into Tf2O-Promoted Electrophilic Activation of 2-Propynamides and a New Synthesis of 2,4-Disubstituted Quinolines

Direct evidence explaining why 2-propynamides have never been used as substrates in Tf₂O-promoted electrophilic activations was obtained. Furthermore, a new method for the synthesis of structurally special 2,4-disubstituted quinolines was developed, by which the substituent at position 2 of quinolines can be diversified easily.

Regio- and diastereoselective transition metal-free hydroalkylation of N-allenyl sulfonamides by push-pull 2-alkynylquinolines

We describe a novel and efficient synthetic strategy to construct the linear homoallylic quinolone structures through the intermolecular addition of 2-alkynylquinoline to N-allenyl sulfonamides. We developed the regio- and diastereoselective transition metal-free hydroalkylation of 1,2-dienes by a structure containing a push-pull system. Moreover, the present work was carried out with a high atom economy, mild reaction conditions, and moderate to high yields.

Transition-metal-free approach to quinolines via direct oxidative cyclocondensation reaction of N,N-dimethyl enaminones with o-aminobenzyl alcohols

A transition-metal-free method for the construction of 3-substituted or 3,4-disubstituted quinolines from readily available N,N-dimethyl enaminones and o-aminobenzyl alcohols is reported. The direct oxidative cyclocondensation reaction tolerates broad functional groups, allowing the efficient synthesis of various quinolines in moderate to excellent yields. The reaction involves a C (sp3)-O bond cleavage and a C=N bind and a C=C bond formation during the oxidative cyclization process, and the mechanism was proposed.

2-(4-Chlorophenyl)-4-(3,4-dimethoxy-phenyl)-6-methoxy-3-methylquinoline

A 2,4-diarylquinoline derivative, 2-(4-chlorophenyl)-4-(3,4-dimethoxyphenyl)-6-methoxy-3-methylquinoline, was synthesized in a conventional two-step procedure from p-anisidine, p-chlorobenzaldehyde and methyl isoeugenol as available starting reagents through a sequence of BF3·OEt2-catalyzed Povarov cycloaddition reaction/oxidative dehydrogenation aromatization processes under microwave irradiation conditions in the presence of a green oxidative I2-DMSO system. The structure of the compound was fully characterized by FT-IR, 1H and 13C-NMR, ESI-MS, and elemental analysis. Its physicochemical parameters (Lipinski’s descriptors) were also calculated using the Molinspiration Cheminformatics software. The diarylquinoline molecule obtained is an interesting model with increased lipophilicity and thus permeability, an important descriptor for quinoline-based drug design. Such types of derivatives are known for their anticancer, antitubercular, antifungal, and antiviral activities.

Elastase inhibitory activity of quinoline Analogues: Synthesis, kinetic mechanism, cytotoxicity, chemoinformatics and molecular docking studies

Herein, we have synthesized quinoline united various Schiff base derivatives (Q1-Q13) and systematically characterized them using diverse analytical practices such as ¹H NMR, ¹³C NMR, FT-IR and LC-MS respectively. All of the target compounds that have been synthesized were tested for elastase inhibition, and the findings were compared to the standard drug oleanolic acid. Among the entire series, compound Q11 (IC₅₀ = 0.897 ± 0.015 µM) exhibit most promising elastase inhibitory activity than oleanolic acid (Standard) having an IC₅₀ value of 13.426 ± 0.015 µM. Also, the utmost effectivecompound Q11 was used for kinetic mechanism investigation based on in-vitro data, from which it has been concluded that compound Q11 inhibits elastase competitively. Furthermore, utilizing the MTT test approach, the most effective compounds were assessed for cytotoxicity on B16F10 melanoma cells. From the cytotoxicity experiment, the most potent compound did not display any hazardous response against B16F10 melanoma cells despite being treated at high concentrations. Additionally, the molecular docking study was settled to govern the binding interaction pattern among an enzyme and inhibitors.

Study and application of graphene oxide in the synthesis of 2,3-disubstituted quinolines via a Povarov multicomponent reaction and subsequent oxidation

The carbocatalyzed synthesis of 2,3-disubstituted quinolines is disclosed. This process involved a three-component Povarov reaction of anilines, aldehydes and electron-enriched enol ethers, which gave the substrate for the subsequent oxidation. Graphene oxide (GO) was exploited as a heterogeneous, metal-free and sustainable catalyst for both transformations. The multicomponent reaction proceeded under simple and mild reaction conditions, exhibited good functional group tolerance, and could be easily scaled up to the gram level. A selection of tetrahydroquinolines obtained was subsequently aromatized to quinolines. The multistep synthesis could also be performed as a one-pot procedure. Investigation of the real active sites of GO was carried out by performing control experiments and a by full characterization of the carbon material by X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (ssNMR).

Cascade synthetic strategies opening access to medicinal-relevant aliphatic 3- and 4-membered N-heterocyclic scaffolds

Cascade reactions are often 'employed' by nature to construct structurally diverse nitrogen-containing heterocycles in a highly stereoselective fashion, i.e., secondary metabolites important for pharmacy. Nitrogen-containing heterocycles of three- and four-membered rings, as standalone and bicyclic compounds, inhibit different enzymes and are pharmacophores of approved drugs or drug candidates considered in many therapies, e.g. anticancer, antibacterial or antiviral. Domino transformations are in most cases in line with modern green chemistry concepts due to atom economy, one-pot procedures often without use the protective groups, time-saving and at markedly lower costs than multistep transformations. The tandem approaches can help to obtain novel N-heterocyclic scaffolds, functionalized according to structural requirements of the target in cells, taking into account the nature of functional group and stereochemistry. On the other hand cascade strategies allow to modify small N-heterocyclic rings in a systematic way, which is beneficial for structure-activity relationship (SAR) analyses. This review is focused on the biological relevance of the N-heterocyclic scaffolds with smaller 3- and 4-membered rings among approved drugs and leading structures of drug candidates. The cascade synthetic strategies offering N-heterocyclic scaffolds, at relatively good yields and high stereoselectivity, are discussed here. The review covers mainly years from 2015 to 2021.

Tandem construction of biological relevant aliphatic 5-membered N-heterocycles

Nature often uses cascade reactions in a highly stereocontrolled manner for assembly structurally diverse nitrogen-containing heterocyclic scaffolds, i.e. secondary metabolites, important for medicinal chemistry and pharmacy. Five-membered nitrogen-containing heterocycles as standalone rings, as well as spiro and polycyclic systems are pharmacophores of drugs approved in various therapies, i.a. antibacterial or antiviral, antifungal, anticancer, antidiabetic, as they target many key enzymes. Furthermore, a large number of pyrrolidine derivatives are currently considered as drug candidates. Cascade transformations, also known as domino or tandem reactions, offer straightforward methods to build N-heterocyclic libraries of the great structural variety desired for drawing SAR conclusions. The tandem transformations are often atom economic and time-saving because they are performed as the one-pot, so no need for purification after each 'virtual' step and the limited necessity of protective groups are characteristic for these processes. Thus, the same results as in classical multistep synthesis can be achieved at markedly lower costs and shorter time, which is in line with modern green chemistry rules. Great advantage of cascade reactions is often reflected in their high regio- and stereoselectivities, enabling the preparing of the heterocyclic compound better fitted to the expected target in cells. This review reveals the biological relevance of N-heterocyclic scaffolds based on saturated 5-membered rings since we showed a number of examples of approved drugs together with the recent biologically attractive leading structures of drug candidates. Next, novel cascade synthetic procedures, taking into account the structure of the reactants and reaction mechanisms, enabling to obtain biological-relevant heterocyclic frameworks with good yields and relatively high stereoselectivity, were reviewed and compared. The review covers the advances of designing biological active N-heterocycles mainly from 2018 to 2021, whereas the synthetic part is focused on the last 7 years.

Recent developments in the synthesis of nitrogen-containing heterocycles from β-aminovinyl esters/ketones as CC-N donors

Nitrogen-containing heterocycles are ubiquitous fragments of numerous natural products, pharmaceuticals, designed bioactive drug candidates and agrochemicals. During the past few decades, these compounds have received considerable attention from the synthetic chemistry community, and great efforts have been focused on the development of concise and efficient methods for the synthesis of these heterocyclic skeletons. In this review, we summarize a diverse range of synthetic methods employing β-aminovinyl esters(ketones) as key CC-N-synthons to furnish useful bioactive heterocyclic frameworks, such as quinolines, pyridines, pyrazines, pyrroles, indoles, oxazoles, imidazoles, thiazoles, isothiazoles, pyrazoles, triazoles, and azepines, thus offering new opportunities and expanding the toolbox of synthetic chemistry reactions.

Metal-free, one-pot synthesis of 2-styrylquinolines via Friedländer annulation and sp3 C–H activation using 1,3-dimethylurea and l-tartaric acid (3 : 1) as a deep eutectic solvent

Functionalized 2-styrylquinolines are prepared using DMU + l-(+)-tartaric acid as deep eutectic solvent. DFT calculations supported the experimental results on role of DES as catalyst. The absorption-emission spectra indicating that these compounds can be useful as fluorescent probes.

Ammonium iodide-catalyzed radical-mediated tandem cyclization of aromatic aldehydes, arylamines and 1,4-dioxane

We have developed a novel approach for the construction of 2-((2-arylquinolin-4-yl)oxy)ethan-1-ol derivatives involving a radical-mediated tandem cyclization reaction.

Electrochemical Selective C3-Thiolation of Quinolines

An electrochemical method has been developed to achieve C3-thiolation of quinoline compounds. This new strategy highlights the maximum atom economy, direct conversion and also the use of simple and readily...

Visible-Light-Induced Multicomponent Cascade Cycloaddition of N-Propargyl Aromatic Amines, Cyclobutanone Oxime Esters, and K2S2O5: Access to Cyanoalkylsulfonylated Quinolines

A visible-light-induced cascade cyanoalkylsulfonylation/cyclization/aromatization of N-propargyl aromatic amines with K₂S₂O₅ and cyclobutanone oxime esters for the construction of cyanoalkylsulfonylated quinolines is developed. This cascade transformation features mild reaction conditions, a broad substrate scope, and excellent functional group compatibility, providing a convenient route toward cyanoalkylsulfonylated quinolines via the formation of a C-C bond and two C-S bonds in one step.

Regioselective Functionalization of Quinolines through C-H Activation: A Comprehensive Review

Quinoline is a versatile heterocycle that is part of numerous natural products and countless drugs. During the last decades, this scaffold also became widely used as ligand in organometallic catalysis. Therefore, access to functionalized quinolines is of great importance and continuous efforts have been made to develop efficient and regioselective synthetic methods. In this regard, C-H functionalization through transition metal catalysis, which is nowadays the Graal of organic green chemistry, represents the most attractive strategy. We aim herein at providing a comprehensive review of methods that allow site-selective metal-catalyzed C-H functionalization of quinolines, or their quinoline N-oxides counterparts, with a specific focus on their scope and limitations, as well as mechanistic aspects if that accounts for the selectivity.

Environmentally Friendly Nafion-Catalyzed Synthesis of Substituted 2-Ethyl-3-Methylquinolines from Aniline and Propionaldehyde under Microwave Irradiation

Herein, we report a facile synthetic methodology for the preparation of 2,3-dialkylquinolines from anilines and propionaldehydes. This cyclization involved environmentally friendly Nafion® NR50 as an acidic catalyst with microwave irradiation as the heating source. A series of substituted 2-ethyl-3-methylquinolines were prepared from various anilines and propionaldehyde derivatives through this protocol with good to excellent yields. Some new chemical structures were confirmed by X-ray single-crystal diffraction analysis and the related data were provided. The plausible reaction mechanism studies are also discussed.

Direct C-H aminocarbonylation of N-heteroarenes with isocyanides under transition metal-free conditions

A C-C bond forming amide synthesis through direct C-H aminocarbonylation of N-heteroarenes with isocyanides was developed. The reaction was mediated by an inorganic persulfate salt under transition metal-free conditions. Mechanistic studies suggested a radical pathway for this reaction without the participation of H₂O and O₂. This method also showed merits of substrate availability, easy operation and atom economy. It provided an efficient route for straightforward synthesis of N-heteroaryl amides.

Synthetic and medicinal perspective of quinolines as antiviral agents

In current scenario, various heterocycles have come up exhibiting crucial role in various medicinal agents which are valuable for mankind. Out of diverse range of heterocycle, quinoline scaffold have been proved to play an important role in broad range of biological activities. Several drug molecules bearing a quinoline molecule with useful anticancer, antibacterial activities etc have been marketed such as chloroquine, saquinavir etc. Owing to their broad spectrum biological role, various synthetic strategies such as Skraup reaction, Combes reaction etc. has been developed by the researchers all over the world. But still the synthetic methods are associated with various limitations as formation of side products, use of expensive metal catalysts. Thus, several efforts to develop an efficient and cost effective synthetic protocol are still carried out till date. Moreover, quinoline scaffold displays remarkable antiviral activity. Therefore, in this review we have made an attempt to describe recent synthetic protocols developed by various research groups along with giving a complete explanation about the role of quinoline derivatives as antiviral agent. Quinoline derivatives were found potent against various strains of viruses like zika virus, enterovirus, herpes virus, human immunodeficiency virus, ebola virus, hepatitis C virus, SARS virus and MERS virus etc.

Development of an efficient, one-pot, multicomponent protocol for synthesis of 8-hydroxy-4-phenyl-1,2-dihydroquinoline derivatives

A one-pot quick and efficient multicomponent reaction has been developed for the synthesis of a new series of functionalized 8-hydroxy-4-phenyl-1,2-dihydroquinoline derivatives using 30 mol% ammonium acetate in ethanol as solvent. This economical protocol run smoothly to give variety of quinoline derivatives in 55% to 98% yield from inexpensive reagents and catalyst in mild reaction conditions. Various spectroscopic techniques like FTIR, 1H NMR and 13C NMR, MALDI-TOF-MS, and EI-MS were used to study and confirm their structure.

Palladium(ii)-catalyzed three-component tandem reactions: synthesis of multiply substituted quinolines

The three-component tandem reaction of 2-aminobenzonitriles, arylboronic acids and ketones as available reagents allowing the synthesis of polysubstitution quinolines is reported.

A comprehensive review on the biological interest of quinoline and its derivatives

Amongst heterocyclic compounds, quinoline is an advantaged scaffold that appears as a significant assembly motif for the development of new drug entities. Quinoline and its derivatives tested with diverse biological activity constitute an important class of compounds for new drug development. Therefore, many scientific communities have developed these compounds as intent structure and evaluated their biological activities. The present, review provides brief natural sources of quinoline and including a new extent of quinoline-based marketed drugs. This review also confers information about the biological activities of quinoline derivatives such as antibacterial, antifungal, antimycobacterial, antiviral, anti-protozoal, antimalarial, anticancer, cardiovascular, CNS effects, antioxidant, anticonvulsant, analgesic, anti-inflammatory, anthelmintic and miscellaneous activities.

Divergent Syntheses of Indoles and Quinolines Involving N1-C2-C3 Bond Formation through Two Distinct Pd Catalyses

Pd-catalyzed annulative couplings of 2-alkenylanilines with aldehydes using alcohols as both the solvent and hydrogen source have been developed. These domino processes allow divergent syntheses of two significant N-heterocycles, indoles and quinolines, from the same substrate by tuning reaction parameters, which seems to invoke two distinct mechanisms. The nature of the ligand and alcoholic solvent had a profound influence on the selectivity and efficiency of these protocols. Particularly noteworthy is that indole formation was achieved by overcoming two significant challenges, regioselective hydropalladation of alkenes and subsequent reactions between the resulting Csp³-Pd species and less reactive imines.

7-Hydroxy-4-phenyl-1, 2-dihydroquinoline derivatives: synthesis via one-pot, three-component reaction and structure elucidation

We have developed a new and facile one pot three component protocol catalyzed by ammonium acetate for construction of new functionalized 7-hydroxy-4-phenyl-1,2-dihydroquinoline derivatives. A variety of quinoline derivatives were obtained in good to excellent yield from inexpensive reagents and catalyst in mild reaction conditions that provide atom economy and cost efficacy. Various spectroscopic techniques like FTIR, ¹HNMR and ¹³CNMR were employed to study their structure while mass of the synthesized compounds were confirmed through MALDI-TOF-MS and EI mass spectrometry.

Nanomaterial assisted bulk scale synthesis of 2-methyl-6-nitroquinoline

Quinolines are an interesting class of moieties with various medicinal chemistry uses. The most prominent is their ability to be used as the last line of therapy for bacterial and viral infections including recent COVID-19. The synthesis of quinoline is through a cyclization reaction and overall reaction yields are about 20%. The bulky ring and the associated crowding of functional groups limit the catalyst options. In this publication, the use of Fe₃O₄@SiO₂ for enhancing yield improvements, especially for heterocyclics is reported. The use of the 40 nm sized silica functionalized magnetite nanoparticles seems to help in both condensation and cyclization steps of representative 2-methyl-6-nitroquinoline. Reaction time reduction due to surface enabled catalysis of nanoparticles is 110 min to 80 min. The reaction yield has doubled due to the presence of catalyst and the mechanism suggests this drastic result is due to stabilization of unstable intermediate on the acidic surface of the silica coating. This near homogeneous catalysis of 40 nm sized, silica functionalized, magnetite nanoparticles have far reaching applications in bulk drug industry for drugs like chloroquine & hydroxychloroquine, the two essential drugs for prophylactic use for COVID-1.

Synthesis of cyclopentaquinolinone and cyclopentapyridinone from ortho-alkynyl-N-arylaldehyde via superbase-promoted C-N, C-O and C-C bond formation

An environmentally benign, transition metal-free, superbase-mediated intramolecular annulation of o-alkynylaldehydes with primary amines forms highly functionalized amino-substituted cyclopentaquinolinones and cyclopentapyridinones via C-N, C-C, and C[double bond, length as m-dash]O bond formation. Contrary to the traditional approaches of ring closures, a different mode of annulation is disclosed. The protocol involves the in situ generations of imine intermediate followed by potassium hydroxide-promoted intramolecular cyclization and subsequent dimethyl sulfoxide induced dehydrogenation leads to the formation of N-heterocycles. X-ray crystallographic studies support the assigned structures of the amino-fused N-heterocycles.

Copper-catalyzed synthesis of aminoquinolines from β-(2-aminophenyl)-α,β-ynones using DMF as dual synthon

A new and efficient method has been developed for the synthesis of 4-aminoquinoline through aerobic Cu(i)-catalyzed cyclization of β-(2-aminophenyl)-α,β-ynones. Under the optimized conditions, DMF could serve as a methine source to introduce C2 carbon and a nitrogen source to incorporate amino functionality in the 4th position. Mechanistic studies using 13C- and DMF-d7 revealed that the methine group was derived from a methyl substituent.

A Review on Recent Advances in Nitrogen-Containing Molecules and Their Biological Applications

The analogs of nitrogen-based heterocycles occupy an exclusive position as a valuable source of therapeutic agents in medicinal chemistry. More than 75% of drugs approved by the FDA and currently available in the market are nitrogen-containing heterocyclic moieties. In the forthcoming decade, a much greater share of new nitrogen-based pharmaceuticals is anticipated. Many new nitrogen-based heterocycles have been designed. The number of novel N-heterocyclic moieties with significant physiological properties and promising applications in medicinal chemistry is ever-growing. In this review, we consolidate the recent advances on novel nitrogen-containing heterocycles and their distinct biological activities, reported over the past one year (2019 to early 2020). This review highlights the trends in the use of nitrogen-based moieties in drug design and the development of different potent and competent candidates against various diseases.

Silver-catalyzed direct C-H oxidative carbamoylation of quinolines with oxamic acids

A silver-catalyzed efficient and direct C-H carbamoylation of quinolines with oxamic acids to access carbamoylated quinolines has been developed through oxidative decarboxylation reaction. The reaction proceeds smoothly over a broad range of substrates with excellent functional group tolerance and excellent yields under mild conditions.