Nitrogen Heterocycles Research Articles

A Modular Approach for Accessing 3D Heterocycles via 1,2-Dicyanation of Planar N-Heteroarenes.

The rapid construction of three-dimensional (3D) heterocyclic frameworks is a key challenge in contemporary medicinal chemistry. The molecules with three-dimensional complexity hold a greater probability to improve clinical outcomes, solubility, selectivity for target proteins, and metabolic stability. However, the prevalence of flat molecules persists among new drug candidates, primarily owing to the multitude of chemical methods available for their synthesis. In principle, the dearomative functionalization of N-heteroarene allows for the conversion of readily available planar molecules into partially or fully saturated nitrogen heterocycles, which are most significant structural motifs of pharmaceuticals and natural products. Unfortunately, these reactions are very rare because of the inherent challenge imposed by heteroarenes' poor reactivity, rendering the process thermodynamically unfavorable. Herein, we report a modular approach for accessing 3D chemical space in translating planar heteroarenes into valuable 3D heterocycles via the installation of a highly versatile cyano group as a new vector. This approach is enabled by the in situ generation of reactive, non-symmetric iodane by combining cyanide anion and bench-stable PhI(OAc)2. This reaction represents a rare example of 1,2-dicyanation of N-heteroarenes that meets the numerous requirements for broad implementation in drug and agrochemical discovery.

A Modular Approach for Accessing 3D Heterocycles via 1,2‐Dicyanation of Planar N‐Heteroarenes

The rapid construction of three‐dimensional (3D) heterocyclic frameworks is a key challenge in contemporary medicinal chemistry. The molecules with three‐dimensional complexity hold a greater probability to improve clinical outcomes, solubility, selectivity for target proteins, and metabolic stability. However, the prevalence of flat molecules persists among new drug candidates, primarily owing to the multitude of chemical methods available for their synthesis. In principle, the dearomative functionalization of N‐heteroarene allows for the conversion of readily available planar molecules into partially or fully saturated nitrogen heterocycles, which are most significant structural motifs of pharmaceuticals and natural products. Unfortunately, these reactions are very rare because of the inherent challenge imposed by heteroarenes’ poor reactivity, rendering the process thermodynamically unfavorable. Herein, we report a modular approach for accessing 3D chemical space in translating planar heteroarenes into valuable 3D heterocycles via the installation of a highly versatile cyano group as a new vector. This approach is enabled by the in situ generation of reactive, non‐symmetric iodane by combining cyanide anion and bench‐stable PhI(OAc)2. This reaction represents a rare example of 1,2‐dicyanation of N‐heteroarenes that meets the numerous requirements for broad implementation in drug and agrochemical discovery.

Photochemical Decarboxylative Radical Alkylation/Cyclization Reaction to Fused Nitrogen Heterocycles by LiI/PPh3 Catalysis

Comprehensive SummaryA visible‐light‐induced decarboxylative radical cascade cyclization reaction between N‐(2‐cyanoaryl)‐acrylamides and alkyl N‐(acyloxy)phthalimide (NHPI esters) for the construction of phenanthridine derivatives has been developed. This approach utilizes lithium iodide (LiI) and triphenylphosphine (PPh3) as the redox catalysts and the alkyl radical is produced through the photoactivation of the electron donor‐acceptor (EDA) complex. A series of primary, secondary, and tertiary alkyl‐substituted phenanthridines are prepared in up to 82% yield without transition‐metal catalysts, chemical oxidants, or metal‐/organic dye‐based photocatalysts.

Metal‐Supported Heterogeneous Catalysts for the Synthesis of Nitrogen‐Containing Heterocycles: A Comprehensive Review

AbstractThe use of metals in the preparation of heterocycles has become increasingly popular due to several key advantages of metals as catalysts. These include recycling capability, eco‐friendliness, simplicity of catalyst preparation and separation, longer lifespan, abundance, and higher yields. As a result of their novel applications in organic, inorganic, medicinal, industrial, polymer chemistry, material sciences, nanotechnology, and biological processes, the utilization of nitrogen‐containing heterocycles has rapidly increased in recent years. Various nitrogen‐containing organic moieties are used in therapeutic processes to enhance effectiveness against several bacterial and viral diseases. This review covers the preparation of imidazoles, triazoles, tetrazoles, pyridine derivatives, azo compounds, pyrimidines, quinoxalines, and quinolines using metals as heterogeneous catalysts. It provides an overview of current methodologies for metal‐assisted heterogeneous catalytic reactions, including product yield, operating temperature, and solvents, among other factors. Heterogeneous catalyst‐mediated organic synthetic reactions offer several advantages, particularly in medicinal chemistry, pharmaceuticals, and industrial applications, by reducing time and energy consumption. This review emphasizes recent advancements in the fabrication of nitrogen heterocycles utilizing heterogeneous catalysts, taking into account various economic, eco‐friendly, and user‐friendly considerations. Additionally, it discusses the benefits, reaction conditions, and yields reported in the literature over the past six years.

Synthesis, Structure, and Properties of a Copper(II) Binuclear Complex Based on Trifluoromethyl Containing Bis(pyrazolyl)hydrazone.

A new complex of copper(II) with methyl-5-(trifluoromethyl)pyrazol-3-yl-ketazine (H2L) was synthesized with the composition [Cu2L2]∙C2H5OH (1). Recrystallization of the sample from DMSO yielded a single crystal of the composition [Cu2L2((CH3)2SO)] (2). The coordination compounds were studied by single-crystal X-ray diffraction analysis, IR spectroscopy, and static magnetic susceptibility method. The data obtained indicate that the polydentate ligand is coordinated by both acyclic nitrogen and heterocyclic nitrogen atoms. The cytotoxic activity of the ligand and complex 1 was investigated on human cell lines MCF7 (breast adenocarcinoma), Hep2 (laryngeal carcinoma), A549 (lung carcinoma), HepG2 (hepatocellular carcinoma), and MRC5 (non-tumor lung fibroblasts). The complex was shown to have a pronounced dose-dependent cytotoxicity towards these cell lines with LC50 values in the range of 0.18-4.03 μM.

Copper-Catalyzed, Intramolecular Amination of Unactivated C(sp3)-H Bonds through Radical Relay.

Although copper-catalyzed amination of activated C(sp3)-H bonds through radical relay has been developed, amination of unactivated C(sp3)-H bonds is rare. Herein, copper-catalyzed intramolecular amination of remote unactivated C(sp3)-H bonds is reported. The reaction is conducted in a mild and effective manner with moderate to good yields, demonstrating broad tolerance toward various functional groups and exhibiting complete regio- and chemoselectivities. This innovation supplies novel synthetic pathways for the construction of saturated nitrogenated heterocycles.

Optimizing sodium storage mechanisms and electrochemical performance of high Nitrogen-Doped hard carbon anode materials Derived from waste plastics for Sodium-Ion batteries

The development of high-performance hard-carbon (HC) anode materials for sodium-ion batteries was constrained by slow charge-transfer kinetics and sodium-storage mechanisms. In this paper, high nitrogen-doped (12.24 %) HC with an efficient interworking structure was synthesized in situ using waste plastics as precursors by utilizing the strong 2-D self-template effect of guanine. Elucidating the mechanism of sodium storage in heteroatom-doped carbon with coexisting heterocyclic and graphitic nitrogen, which synergistically enhances electrochemical activity, utilizing a range of in-situ and ex-situ characterization methods. Based on density functional theory (DFT), it has been discovered that the doping of pyrrole nitrogen (N5) and pyridinium nitrogen (N6) can effectively expand the interlayer spacing during the Na+ sodiated/de-sodiated process, thereby enhancing electrochemical activity. The optimized HC has increased the Na+ diffusion coefficient by 1.5 orders of magnitude (10-8.2 cm2 s−1 vs 10-9.76 cm2 s−1) and exhibits high reversible capacity (452 mAh/g@20 mA g−1), high rate performance (388mAh/g@500 mA g−1), superior cycling stability (87.6 % @500 mA g−1 after 2,000 cycles). The full cell exhibits good cyclic stability (91.87 %@100 mA g−1 after 2,00 cycles), while the designed pouch cell also demonstrates favorable cycle life (90.78 %@200 mA g−1 after 100 cycles).

Direct C4 and C2 C-H Amination of Heteroarenes Using I(III) Reagents via a Cross Azine Coupling.

Aminated nitrogen heterocycles are valuable motifs across numerous chemical industries, perhaps most notably in small molecule drug discovery. While numerous strategies for installing nitrogen atoms onto azaarenes exist, most require prefunctionalization and methods for direct C-H amination are almost entirely limited to position C2. Herein, we report a method for the direct C2 and C4 C-H amination of fused azaarenes via in situ activation with a bispyridine-ligated I(III) reagent, [(Py)2IPh]2OTf, or Py-HVI. Unlike commonly used N-oxide chemistry, the method requires no preoxidation of the azaarene and provides unprecedented direct access to C4 amination products. The resulting N-heterocyclic pyridinium salts can be isolated via simple trituration. The free amine can be liberated under mild Zincke aminolysis, or the amination and cleavage can be telescoped to a one-pot process. The scope of the method is broad; the conditions are mild and operationally simple, and the aminated products are produced in good to excellent yields. Computational studies provide insights into the mechanism of activation, which involves an unusual direct nucleophilic functionalization of an I(III) ligand, as well as a kinetic basis for the observed C2 and C4 amination products.

Synthesis of N-heterocycles through alcohol dehydrogenative coupling.

Nitrogen heterocycles are found in the structures of many biologically important compounds, as well as materials used in the synthesis of fine chemicals. Notably, ~59% of US Food and Drug Administration-approved small-molecule drugs contain nitrogen heterocycles. It is therefore meaningful to explore greener or more sustainable methods for their synthesis. The use of alcohols as reagents is attractive as they can be readily obtained from biomass derived natural resources. In the last two decades, alcohol dehydrogenative coupling reaction to synthesize various heterocycles were extensively explored which furnished hydrogen (H2) and water (H2O) as the two greener byproducts. In this protocol, we describe several efficient catalytic transformations to synthesize quinolines, 1,8-naphthyridines, quinoxalines, quinazolines, pyrimidines, benzimidazoles, pyrroles and pyridines, using alcohol as starting materials. We also describe the synthesis of several homogeneous iridium/ruthenium catalysts and heterogeneous cobalt/copper catalysts that can be used in these transformations. The reaction setup is simple; in a Schlenk/reaction tube with magnetic stir-bar, alcohol, corresponding coupling reagents (nucleophiles), catalyst, base and solvent (water or organic solvent such as toluene, dioxane or p-xylene) are added. The reaction mixture is refluxed at the specified temperature (110-150 °C)-either in air or under argon-to furnish these heterocycles. Synthesis of the catalysts takes 3-5 h and the coupling reactions take 4-5 h depending on the target product. The cobalt- and copper-based heterogeneous catalytic systems displayed an good catalyst recyclability.

Synthesis of fluorinated six-membered nitrogen heterocycles using microwave irradiation

Synthesis of fluorinated six-membered nitrogen heterocycles using microwave irradiation

Design, Docking, Synthesis, and In vitro Evaluation of Potent Anti-tubercular Agents Targeting DNA Gyrase

Background: Tuberculosis caused by Mycobacterium tuberculosis has been reported to infect about two-third of the global population and to continuously develop multidrug resistance. DNA gyrase, a type II topoisomerase, is a promising target of the quinolone class of drugs in the treatment of tuberculosis. Objective: The present study is focused on the design and synthesis of newer nitrogen heterocyclics containing indole, n-methyl piperazine, piperidine, and pyrrolidine ring structures. Methods: Initially designed compounds were evaluated for their affinity to the DNA gyrase target. The molecular docking performed using FlexX indicated compounds IIb5 (1-(R)-(4-hydroxyphenyl)(4- methylpiperazin-1-yl)methyl)-3-((S)-(4-hydroxyphenyl)(4-methylpiperazin-1-yl)methyl)urea and IIc5 ((1-(R)-(4-hydroxyphenyl)(4-methylpiperazin-1-yl)methyl)-3-((S)-(4-hydroxyphenyl)(4-methylpiperazin- 1-yl)methyl) thiourea to exhibit promising binding affinity (dock score of -15.01 and -13.77) respectively when compared to the reference MFX moxifloxacin (dock score -4.40) with the target 5BS8 (DNA gyrase). Further, the best 10 compounds were synthesized by one-pot synthesis employing the reaction of indole/N-methyl piperazine/piperidine/pyrrolidine with N-substituted benzaldehydes in the presence of acetamide/urea/thiourea to afford the compounds in 54.60% to 85.47% yield. The synthesized compounds were suitably characterized using chromatographic and spectroscopic tools. Results: In the microplate Alamar Blue assay (MABA), compounds IIb1, IIIc2, IIIb1, and IIb5 exhibited good minimum inhibitory concentrations of 1.6 μg/mL, 3.12 μg/mL, and 12.5 μg/mL, respectively, when compared to the standard rifampicin with 0.8 μg/mL inhibitory concentration. The MTB gyrase supercoiling assay performed using Mycobacterium tuberculosis gyrase supercoiling assay kit demonstrated compound IIb5 at a concentration of 300 μg/mL to show gyrase inhibition in comparison to MFX at 60 μg/mL. In the MTT assay performed using the human breast cancer cell line MCF-7, compounds IIc2, IIb5, and IIb1 showed IC50 values of 2.57 μM, 12.54 μM, and 12.75 μM, respectively, compared to doxorubicin (1.10 μM) at 7-48 hrs and 72 hrs of the study. Conclusion: Based on these observations, N-methyl piperazine class of compounds can serve as a lead/pharmacophore for the rational design of potent molecules against MTB gyrase to combat the growing issue of MDR-TB.

Microwave-Induced Synthesis of Bioactive Nitrogen Heterocycles.

There are many different applications of heterocyclic molecules in the pharmaceutical and materials science fields, which make them an important family of compounds. Among these heterocyclic compounds, nitrogen-containing heterocyclic (N-heterocyclic) compounds have attracted a lot of interest among researchers due to their various applications across a wide variety of fields. Many studies have been performed over the past few years to study the synthesis of N-heterocycles under different reaction conditions, such as solvent-free, catalytic, reactants immobilized on a solid support, one-pot synthesis, and microwave irradiation. It has been demonstrated by our research group that microwaves can be utilized for rapid and efficient synthesis of biologically active compounds. In this review, we provide an overview of the microwave-assisted non-catalytic and catalytic preparation of nitrogen-containing heterocycles, mostly polycyclic N-heterocycles, five-membered N-heterocycles, six-membered N-heterocycles, and fused N-heterocycles. Mostly in this article, we explore the microwave-assisted preparation of biologically important compounds, such as pyrimidines, thiazoles, imines, tetrazoles, steroidal derivatives, quinolines, indolizine, triazoles, beta-lactams, pyrroles and quinoxalines.

Nitrogen-Site Engineering in Covalent Organic Frameworks for H2O2 Photogeneration via Dual Channels of Indirect Two-Electron O2 Reduction.

Photocatalytic H2O2 production is a green and sustainable route, but far from meeting the increasing demands of industrialization due to the rapid recombination of the photogenerated charge carriers and the sluggish reaction kinetics. Effective strategies for precisely regulating the photogenerated carrier behavior and catalytic activity to construct high-performance photocatalysts are urgently needed. Herein, a nitrogen-site engineering strategy, implying elaborately tuning the species and densities of nitrogen atoms, is applied for H2O2 photogeneration performance regulation. Different nitrogen heterocycles, such as pyridine, pyrimidine, and triazine units, are polymerized with trithiophene units, and five covalent organic frameworks (COFs) with distinct nitrogen species and densities on the skeletons are obtained. Fascinatingly, they photocatalyzed H2O2 production via dominated two-electron O2 reduction processes, including O2-O2 •‒-H2O2 and O2-O2 •‒-O2 1-H2O2 dual pathways. Just in the air and pure water, the multicomponent TTA-TF-COF with the maximum nitrogen densities triazine nitrogen densities exhibited the highest H2O2 production rate of 3343µmol g-1 h-1, higher than most of other reported COFs. The theoretical calculation revealed the higher activity is due to the easy formation of O2 •‒ and O2 1 in different catalytic process. This study gives a new insight into designing photocatalysis at atomic level.

Electrochemical Generation of Nitrogen‐centered Radicals and its Application for the Green Synthesis of Heterocycles

AbstractElectrochemistry became a unique and powerful tool for the preparation of a plethora of valuable chemical species including functional materials, drug candidates and clinically approved pharmaceuticals. Organic electrosynthesis well satisfies main goals of green chemistry development and is considered as one of the useful approaches toward the creation of sustainable future. Since nitrogen heterocyclic scaffolds still retain their importance for the construction of novel materials and medications, one of the emerging trends in organic electrochemistry is the discovery of novel green and sustainable synthetic methods toward the assembly of heterocyclic subunits. In this regard, organic electrochemistry provides an efficient platform for environmentally benign generation of various nitrogen‐centered radicals which are prominent intermediates in the synthesis of nitrogen heterocycles. In this Review, recent developments in the creation of green synthetic methods for the construction of nitrogen heterocycles via electrochemical generation of nitrogen‐centered radicals are summarized. The special emphasis is devoted to the influence of solvent, electrodes and electrolytes on the electrochemical step, since these crucial parameters regulate the process efficiency.

Pyrolysis of polystyrene using low-cost natural catalysts: Production and characterisation of styrene-rich pyro-oils

This work aims to study the catalytic pyrolysis of polystyrene (PS) in order to obtain a styrene-rich liquid appealing for re-polymerisation processes. The process was performed in a fixed-bed reactor using low-cost materials such as ilmenite, olivine, calcium oxide (CaO) and dolomite as catalysts at 600 ºC. A non-catalytic test with sand was also conducted for comparison purposes. The resulting pyro-oil yield was between 89 and 96 wt%, and consisted mainly of styrene monomer, styrene dimer and styrene trimer, as well as other light aromatic compounds depending on the catalyst used. Olivine and CaO were capable to increase the styrene monomer concentration in the pyro-oil by about 10–12 % compared to non-catalytic pyrolysis, reaching up to 74.5 and 71.4 wt%, respectively. Furthermore, these catalysts reduced the concentration of styrene dimer and styrene trimer in the pyro-oil, which could be useful for further re-polymerisation processes. However, the presence of polyaromatics (PAHs) in the pyro-oils obtained from ilmenite, olivine and CaO was also identified, and other families such as mono-aromatics, di-aromatics, BTX, and nitrogen heterocyclic compounds were also increased in all pyro-oils obtained with catalysts compared to those obtained by non-catalytic pyrolysis. In addition, several inorganic species in the pyro-oil were reduced by the addition of the catalysts. This effect was observed after the addition of olivine and CaO, especially in the reduction of S, Mg, Ca and Fe. These results clearly demonstrate the potential of pyrolysis to convert PS waste into valuable building blocks for the production of new plastics.

The characteristic structural and functional dynamics of P. falciparum DHFR binding with pyrimidine chemotypes implicate malaria therapy design

Dihydrofolate reductase (DHFR) enzyme regulates de-novo folate synthesis in Plasmodium falciparum, hence a critical malaria drug target. Pyrimethamine inhibits DHFR, but resistance and lack of cross-species activity are key challenges. Therefore, this study is set to investigate more potent nitrogenous heterocyclic compounds against DHFR. Docking and MD simulations were employed to gain insight into the compounds’ binding free energies and conformational stabilities, while cross-species activity was determined using sequence alignment. Among the 500 screened compounds, PMD_01 (−12.2 kcal/mol), PMD_02 (−11.1 kcal/mol), PMD_03 (−10.7 kcal/mol), and PMD_04 (−10.7 kcal/mol) have the highest binding affinities against pfDHFR compared to pyrimethamine (−7.9 kcal/mol). Critical amino acids for binding interactions in the active site of pfDHFR include Leu45, Thr107, Ile164, and Thr170. PMD-bound systems showed higher binding free energy than pyrimethamine, except PMD_03. Hydrogen bonding interactions with Gly159, Ser101, Ser104, Ser160, Ile157, and Lys48 played significant roles in the binding interaction of these compounds as opposed to Asp53 in pyrimethamine. The four systems converged around 1.90 Å RMSD and showed more stability than pyrimethamine-bound and unbound pfDHFR. The pocket's residues across the four plasmodia were highly conserved, but Phe116 and Ile164 replaced Met in P. knowlesi and Tyr in the other species. PMD_01, PMD_02, PMD_03, and PMD_04 showed promising inhibition against pfDHFR and are, thus, potential antimalarial agents against plasmodia DHFR homologues.

Heterocyclic Nitrogen Compounds as Potential PDE4B Inhibitors in Activated Macrophages

Cyclic-nucleotide phosphodiesterases (PDEs) represent a superfamily of enzymes playing a pivotal role in cell signaling by controlling cAMP and cGMP levels in response to receptor activation. PDE activity and expression are linked to many diseases including inflammatory diseases. In light of their specific biochemical properties, PDE inhibition has attracted the interest of several researrs In this context, PDE4 inhibition induces anti-inflammatory effects. Piclamilast and rolipram, well-known PDE4 inhibitors, are endowed with common side effects. The selective phosphodiesterase 4B (PDE4B) inhibitors could be a promising approach to overcome these side effects. In the present study, six potential PDE4B inhibitors have been investigated. Through this study, we identified three PDE4B inhibitors in human macrophages activated by lipopolysaccharide. Interestingly, two of them reduced reactive oxygen species production in pro-inflammatory macrophages.

Bringing back Galium aparine L. from forgotten corners of traditional wound treatment procedures: an antimicrobial, antioxidant, and in-vitro wound healing assay along with HPTLC fingerprinting study

BackgroundThe wound healing process, restoring the functionality of the damaged tissue, can be accelerated by various compounds. The recent experimental analysis highlights the beneficial effects of phytochemicals in improving skin regeneration and wound healing. In traditional medicine, one of the widespread plants used for treating different injuries or skin afflictions is Galium aparine L. (GA). Besides, previously reported chemical compounds of GA suggested its therapeutic effects for the wound healing process, yet its regulatory effects on the cellular and molecular stages of the wound healing process have not been investigated.MethodsIn the present study, the phytochemical profile of the GA extract was analyzed using HPTLC fingerprinting, and further scientific evaluation of its phytochemicals was done. The wound-healing effects of GA extract were explored at the cellular and molecular levels while accounting for cell toxicity. The wound closure enhancing effect, antibacterial activity, and antioxidant activity were assessed.ResultsThe HPTLC fingerprinting of the GA extract proved its previously reported phytochemical profile including phenols, flavonoids, tannins, plant acids, ergot alkaloids, flavonoids, anthraquinones, terpenoids, sterols, salicin, lipophilic compounds, saponins, iridoids, and heterocyclic nitrogen compounds. Antimicrobial assessment, of the extract, indicated the more susceptibility of S. aureus to the inhibitory effects of GA rather than E. coli and S. epidermidis. DPPH test results revealed the antioxidant property of GA extract, which was comparable to ascorbic acid. The results of the viability assay showed no cytotoxicity effects on human umbilical endothelial cell (HUVEC) and normal human dermal fibroblast (NHDF) cell lines treated with different concentrations of whole plant extract and cell viability increased in a dose-dependent manner. The results of the scratch assay showed improved cell migration and wound closure.ConclusionsThis study shows the anti-oxidant, anti-microbial, and in vitro wound healing wound-healing effects of GA hydroalcoholic extract, which aligns with its use in traditional medicine. No cytotoxicity effects were shown. The results from this study can be the basis for further investigations such as animal models and phytochemical studies. Further evaluation of its effects on mechanisms and signaling pathways involved in the wound healing processes such as angiogenesis and cell proliferation can provide novel insights into the potential therapeutic effects of the GA extract.

Recent Discovery of Nitrogen Heterocycles from Marine-Derived Aspergillus Species.

Nitrogen heterocycles have drawn considerable attention because of their structurally novel and significant biological activities. Marine-derived fungi, especially the Aspergillus species, possess unique metabolic pathways to produce secondary metabolites with novel structures and potent biological activities. This review prioritizes the structural diversity and biological activities of nitrogen heterocycles that are produced by marine-derived Aspergillus species from January 2019 to January 2024, and their relevant biological activities. A total of 306 new nitrogen heterocycles, including seven major categories-indole alkaloids, diketopiperazine alkaloids, quinazoline alkaloids, isoquinoline alkaloids pyrrolidine alkaloids, cyclopeptide alkaloids, and other heterocyclic alkaloids-are presented in this review. Among these nitrogen heterocycles, 52 compounds had novel skeleton structures. Remarkably, 103 compounds showed various biological activities, such as cytotoxic, antimicrobial, anti-inflammatory, antifungal, anti-virus, and enzyme-inhibitory activities, and 21 compounds showed potent activities. This paper will guide further investigations into the structural diversity and biological activities of nitrogen heterocycles derived from the Aspergillus species and their potential contributions to the future development of new natural drug products in the medicinal and agricultural fields.

Efficient synthetic strategies for fused pyrimidine and pyridine derivatives: A review

AbstractPyrimidine and its derivatives play a paramount role in drug discovery as privileged pharmacophores with considerable chemical and biological significance and its presence in genes. This review aims to assemble a systematic evaluation of synthetic tactics of various fused pyrimidine derivatives containing nitrogen heterocycles such as pyridopyridines, pyridopyrimidines, and pyrimidopyrimidine from a pharmacological point of view and deliver an overview of methodologies presenting the chemistry of fused pyrimidine derivatives. The review details the importance of various catalysts and ring substitution using various electrophilic and nucleophilic reagents. These synthetic strategies were elaborated based on the different synthetic routes that lead to the specific type of pyrimidine and pyridine fused derivatives. The literature accumulates various developments in one‐pot condensation, the Knoevenagel–Michael addition mechanism, microwave and ultrasound irradiation, intramolecular cyclization, nano‐catalytic reactions, and so forth. Short reaction times, catalyst reusability, solvent‐free conditions, excellent yields, and stereo‐selectivity are some of the benefits of certain synthetic approaches.