Microwave Assisted Reactions of Azaheterocycles Formedicinal Chemistry Applications

Current strategies in design and synthesis of antifungals hybrid and chimeric diazine derivatives

In the last decades fungal infections became a major threat to human health having an unacceptably occurrence, a high rate of mortality and the number of patients at risk for these infections continue to increase every year. An effective, modern and very useful strategy in antifungal therapy is represented by the use of chimeric and hybrid drugs, most of them being with azaheterocycle skeleton. In this review, we present an overview from the last five years of the most representative achievements in the field of chimeric and hybrid diazine derivatives with antifungal properties. Within this work we emphasize the most relevant data concerning the synthesis, design, Structure Activity Relationships (SAR) correlations and antifungal activity of the main classes of diazine: 1,2-diazine (pyridazine), 1,3-diazine (pyrimidine), 1,4-diazine (pyrazine) and their fused derivatives.

Site-selective benzylic C-H hydroxylation in electron-deficient azaheterocycles

Benzylic C-H bonds can be converted into numerous functional groups, often by mechanisms that involve hydrogen atom transfer as the key bond breaking step. The abstracting species is most often an electrophilic radical, which makes these reactions best suited to electron-rich C-H bonds to achieve appropriate polarity matching. Thus, electron deficient systems such as pyridine and pyrimidine are relatively unreactive, and therefore underrepresented in substrate scopes. In this report, we describe a new method for heterobenzylic hydroxylation-essentially an unknown reaction in the case of pyrimidines-that makes use of an iodine(III) reagent to afford very high selectivity towards electron-deficient azaheterocycles in substrates with more than one reactive position and prevents over-oxidation to carbonyl products. The identification of key reaction byproducts supports a mechanism that involves radical coupling in the bond forming step.

Recent advances in microwave-assisted multicomponent synthesis of spiro heterocycles

Spiro heterocycle frameworks are a class of organic compounds that possesses unique structural features making them highly sought-after targets in drug discovery due to their diverse biological and pharmacological activities. Microwave-assisted organic synthesis has emerged as a powerful tool for assembling complex molecular architectures. The use of microwave irradiation in synthetic chemistry is a promising method for accelerating reaction rates and improving yields. This review provides insights into the current state of the art and highlights the potential of microwave-assisted multicomponent reactions in the synthesis of novel spiro heterocyclic compounds that were reported between 2017 and 2023.

Hybrids Diazine: Recent Advancements in Modern Antimicrobial Therapy

Nowadays, antimicrobial therapies have become a very challenging issue because of a large diversity of reasons such as antimicrobial resistance, over consumption and misuse of antimicrobial agents, etc. A modern, actual and very useful approach in antimicrobial therapy is represented by the use of hybrid drugs, especially combined five and six-membered ring azaheterocycles. In this review, we present an overview of the recent advanced data from the last five years in the field of hybrid diazine compounds with antimicrobial activity. In this respect, we highlight here essential data concerning the synthesis and antimicrobial activity of the main classes of diazine hybrids: pyridazine, pyrimidine, pyrazine, and their fused derivatives.

Antitumor Activity of PEGylated and TEGylated Phenothiazine Derivatives: Structure–Activity Relationship

The paper aims to investigate the antitumor activity of a series of phenothiazine derivatives in order to establish a structure–antitumor activity relationship. To this end, PEGylated and TEGylated phenothiazine have been functionalized with formyl units and further with sulfonamide units via dynamic imine bonds. Their antitumor activity was monitored in vitro against seven human tumors cell lines and a mouse one compared to a human normal cell line by MTS assay. In order to find the potential influence of different building blocks on antitumor activity, the antioxidant activity, the ability to inhibit farnesyltransferase and the capacity to bind amino acids relevant for tumor cell growth were investigated as well. It was established that different building blocks conferred different functionalities, inducing specific antitumor activity against the tumor cells.

Hybrid Azine Derivatives: A Useful Approach for Antimicrobial Therapy

Nowadays, infectious diseases caused by microorganisms are a major threat to human health, mostly because of drug resistance, multi-drug resistance and extensive-drug-resistance phenomena to microbial pathogens. During the last few years, obtaining hybrid azaheterocyclic drugs represents a powerful and attractive approach in modern antimicrobial therapy with very promising results including overcoming microbial drug resistance. The emphasis of this review is to notify the scientific community about the latest recent advances from the last five years in the field of hybrid azine derivatives with antimicrobial activity. The review is divided according to the main series of six-member ring azaheterocycles with one nitrogen atom and their fused analogs. In each case, the main essential data concerning synthesis and antimicrobial activity are presented.

The Crystal Structure of 3-Amino-1-(4-Chlorophenyl)-9-Methoxy-1H-Benzo[f]Chromene-2-Carbonitrile: Antimicrobial Activity and Docking Studies

Compound 3-amino-1-(4-chlorophenyl)-9-methoxy-1H-benzo[f]chromene-2-carbonitrile (4), was synthesized via the reaction of 7-methoxynaphthalen-2-ol (1), 4-chlorobenzaldehyde (2), and malononitrile (3) in an ethanolic piperidine solution under microwave irradiation. The synthesized pyran derivative 4 was asserted through spectral data and X-ray diffraction. The molecular structure of compound 4 was established unambiguously through the single crystal X-ray measurements and crystallized in the Triclinic, P-1, a = 8.7171 (4) Å, b = 10.9509 (5) Å, c = 19.5853 (9) Å, α = 78.249 (2)°, β = 89.000 (2)°, γ = 70.054 (2)°, V = 1717.88 (14) Å3, Z = 4. The target molecule has been screened for antibacterial and antifungal functionality. Compound 4 exhibited favorable antimicrobial activities that resembled the reference antimicrobial agents with an IZ range of 16–26 mm. In addition, MIC, MBC, and MFC were assessed and screened for molecule 4, revealing bactericidal and fungicidal effects. Lastly, a molecular docking analysis was addressed and conducted for this desired molecule.

Microwave-assisted rapid conjugation of horseradish peroxidase-dextran aldehyde with Schiff base reaction and decolorization of Reactive Blue 19

Microwave irradiation has become a routine technique in homogeneous and effective heating in organic synthesis. However, its application in enzyme-containing reactions is limited since it can cause denaturation of the enzyme. In this study, we have briefly investigated the effect of microwave heating on the conjugation reaction of horseradish peroxidase (HRP) with aldehyde derivative of dextran (D-CHO). The reaction was irradiated by microwave at 50 °C for 5 min. The conjugate was confirmed via GPC, in which the conjugates of HRP and D-CHO coexist with free unbound HRP molecules. Activity studies of HRP revealed that there is a small decrease in conjugate activity relative to the free enzyme after a short bioconjugation reaction with microwave irradiation. In decolorization studies of the textile dye Reactive Blue 19 (RB19), 99% of RB19 was decolorized through the free enzyme at 35 °C while the decolorization of the dye was 96% at 25-35 °C by the conjugate, which is a critical result showing clearly that the HRP conjugated via D-CHO is not denatured and still active after microwave-assisted reaction. This phenomenon is due to the multiple point conjugation of D-CHO on the surface of HRP and locking the 3D structure which may prevent changes in the secondary or tertiary structure of the enzyme. The results reveal that microwave irradiation can be used in production of covalently modified enzymes.

Microwave-assisted photooxidation of sulfoxides

We demonstrated microwave-assisted photooxidation of sulfoxides to the corresponding sulfones using ethynylbenzene as a photosensitizer. Efficiency of the photooxidation was higher under microwave irradiation than under conventional thermal heating conditions. Under the conditions, ethynylbenzene promoted the oxidation more efficiently than conventional photosensitizers benzophenone, anthracene, and rose bengal. Ethynylbenzene, whose T1 state is extremely resistant to intersystem crossing to the ground state, was suitable to this reaction because spectroscopic and related reported studies suggested that this non-thermal effect was caused by elongating lifetime of the T1 state by microwave. This is the first study in which ethynylbenzene is used as a photosensitizer in a microwave-assisted photoreaction.

[3 + n] Cycloaddition Reactions: A Milestone Approach for Elaborating Pyridazine of Potential Interest in Medicinal Chemistry and Optoelectronics

During the last few decades, pyridazine derivatives have emerged as privileged structures in heterocyclic chemistry, both because of their excellent chemistry and because of their potential applications in medicinal chemistry and optoelectronics. This review is focused on the recent advances in [3 + n] cycloaddition reactions in the pyridazine series as well as their medicinal chemistry and optoelectronic applications over the last ten years. The stereochemistry and regiochemistry of the cycloaddition reactions are discussed. Applications in optoelectronics (in particular, as fluorescent materials and sensors) and medicinal chemistry (in particular, antimicrobials and anticancer) are also reviewed.

Recent Advancement of Ullmann Condensation Coupling Reaction in the Formation of Aryl-Oxygen (C-O) Bonding by Copper-Mediated Catalyst

Transition metal-catalyzed chemical transformation of organic electrophiles and organometallic reagents belong to the most important cross coupling reaction in organic synthesis. The biaryl ether division is not only popular in natural products and synthetic pharmaceuticals but also widely found in many pesticides, polymers, and ligands. Copper catalyst has received great attention owing to the low toxicity and low cost. However, traditional Ullmann-type couplings suffer from limited substrate scopes and harsh reaction conditions. The introduction of homogeneous copper catalyst with presence of bidentate ligands over the past two decades has totally changed this situation as these ligands enable the reaction promoted in mild condition. The reaction scope has also been greatly expanded, rendering this copper-based cross-coupling attractive for both academia and industry. In this review, we will highlight the latest progress in the development of useful homogeneous copper catalyst with presence of ligand and heterogeneous copper catalyst in Ullmann type C-O cross-coupling reaction. Additionally, the application of Ullmann type C-O cross coupling reaction will be discussed.

Green Synthesis, SC-XRD, Non-Covalent Interactive Potential and Electronic Communication via DFT Exploration of Pyridine-Based Hydrazone

Ultrasound-based synthesis at room temperature produces valuable compounds greener and safer than most other methods. This study presents the sonochemical fabrication and characterization of a pyridine-based halogenated hydrazone, (E)-2-((6-chloropyridin-2-yl)oxy)-N′-(2-hydroxybenzylidene) acetohydrazide (HBPAH). The NMR spectroscopic technique was used to determine the structure, while SC-XRD confirmed its crystalline nature. Our structural studies revealed that strong, inter-molecular attractive forces stabilize this crystalline organic compound. Moreover, the compound was optimized at the B3LYP/6-311G(d,p) level using the Crystallographic Information File (CIF). Natural bonding orbital (NBO) and natural population analysis (NPA) were performed at the same level using optimized geometry. Time-dependent density functional theory (DFT) was performed at the B3LYP/6-311G (d,p) method to calculate the frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP). The global reactivity descriptors were determined using HOMO and LUMO energy gaps. Theoretical calculations based on the Quantum Theory of Atoms in Molecules (QT-AIM) and Hirshfeld analyses identified the non-covalent and covalent interactions of the HBPAH compound. Consequently, QT-AIM and Hirshfeld analyses agree with experimental results.