Microwave-assisted synthesis and investigation of xanthine oxidase inhibition of new phthalonitrile and phthalocyanines containing morpholino substituted 1,2,4-triazole-3-one

Recent advances in microwave-assisted synthesis of triazoles and their derivatives: a green approach toward sustainable development methods

Triazole, a nitrogen-containing five-membered heterocycle with two isomeric forms, 1,2,3-triazole and 1,2,4-triazole, has proven to be a valuable component in the pharmaceutical domain. Owing to its widespread utility in drug development, pharmaceutical and medicinal chemistry, several synthetic methods have been explored, such as different catalytic systems, solvents, and heating methodologies in recent years. However, some methods were associated with several limitations, such as harsh reaction conditions, high temperatures, low atom economy, and long reaction times. Conversely, the ongoing demand from the chemical industry has led to increased attention on overcoming these limitations and developing sustainable laboratory methods. In recent years, the microwave heating method in organic synthesis has evolved as a new, environmentally friendly approach with benefits such as atom economy, reduced use of hazardous chemicals, safer chemical design, few derivatives and enhanced energy efficiency. This review summarizes recent progress in microwave-assisted synthesis of triazoles (1,2,3-triazole and 1,2,4-triazole), with a comparative analysis between conventional methods and microwave-assisted methods in terms of reaction time, yield, green synthesis, sustainability and other relevant factors.

Phthalocyanines Synthesis: A State-of-The-Art Review of Sustainable Approaches Through Green Chemistry Metrics

Driven by escalating environmental concerns, synthetic chemistry faces an urgent need for a green revolution. Green chemistry, with its focus on low environmental impacting chemicals and minimized waste production, emerges as a powerful tool in addressing this challenge. Metrics such as the E-factor guide the design of environmentally friendly strategies for chemical processes by quantifying the waste generated in obtaining target products, thus enabling interventions to minimize it. Phthalocyanines (Pcs), versatile molecules with exceptional physical and chemical properties, hold immense potential for technological applications. This review aims to bridge the gap between green chemistry and phthalocyanine synthesis by collecting the main examples of environmentally sustainable syntheses documented in the literature. The calculation of the E-factor of a selection of them provides insights on how crucial it is to evaluate a synthetic process in its entirety. This approach allows for a better evaluation of the actual sustainability of the phthalocyanine synthetic process and indicates possible strategies to improve it.

Triazole derivatives as potential xanthine oxidase inhibitors: Design, enzyme inhibition potential, and docking studies

Considerable ingenuity has been shown in the recent years in the discovery of novel xanthine oxidase (XO) inhibitors that fall outside the purine scaffold. The triazole nucleus has been the cornerstone for the development of many enzyme inhibitors for the clinical management of several diseases, where hyperuricemia is one of them. Here, we give a critical overview of significant research on triazole-based XO inhibitors, with respect to their design, synthesis, inhibition potential, toxicity, and docking studies, done till now. Based on these literature findings, we can expect a burst of modifications on triazole-based scaffolds in the near future by targeting XO, which will treat hyperuricemics, that is, painful conditions like gout that at present are hard to deal with.

Recent Advances in Xanthine Oxidase Inhibitors

Uric acid is a product of purine nucleotide metabolism, and high concentrations of uric acid can lead to hyperuricemia, gout and other related diseases. Xanthine oxidase, the only enzyme that catalyzes xanthine and hypoxanthine into uric acid, has become a target for drug development against hyperuricemia and gout. Inhibition of xanthine oxidase can reduce the production of uric acid, so xanthine oxidase inhibitors are used to treat hyperuricemia and related diseases, including gout. In recent years, researchers have obtained new xanthine oxidase inhibitors through drug design, synthesis, or separation of natural products. This paper summarizes the research on xanthine oxidase inhibitors since 2015, mainly including natural products, pyrimidine derivatives, triazole derivatives, isonicotinamide derivatives, chalcone derivatives, furan derivatives, coumarin derivatives, pyrazole derivatives, and imidazole derivatives, hoping to provide valuable information for the research and development of novel xanthine oxidase inhibitors.

Targeting Melanocortin Receptors Using SNAr-Type Macrocyclization: A Doubly Orthogonal Route to Cyclic Peptide Conjugates

While a range of strategies exist to accomplish peptide macrocyclization, they are frequently limited by the need for orthogonal protection or provide little opportunity for structural diversification. We have evaluated an efficient macrocyclization method that employs nucleophilic aromatic substitution (S_NAr) to create thioether macrocycles. This versatile macrocyclization, orthogonal to conventional peptide synthesis, can be performed in solution on unprotected peptidomimetics or on resin-bound peptides with side-chain protection in place. We show that the electron-withdrawing groups present in the products can be further utilized in subsequent orthogonal reactions to alter the peptide properties or to add prosthetic groups. The macrocyclization strategy was applied to the design of melanocortin ligands, generating a library of potent melanocortin agonists that exhibit distinct subtype selectivity.

Synthesis, Characterization, and Enzyme Inhibition Properties of 1,2,4-Triazole Bearing Azinane Analogues

Considering the importance of acetylcholine esterase (AChE, BchE) and α-glucosidase in the treatment of Alzheimer's disease and diabetes mellitus, the synthesis of novel azinane triazole-based derivatives as effective acetylcholinesterase (AchE), α-glucosidase, urease, lipoxygenase (LOX), and butyrylcholinesterase (BChE) inhibitors is described. Azinane analogue (2) was merged with 1,2,4-triazole to acquire 1-(4-toluenesulfonyl)-4-(3-mercapto-4-methyl-4H-1,2,4-triazol-5-yl) piperidine (8) through a list of intermediates including 1-(4-toluenesulfonyl)-4-(ethoxycarbonyl) piperidine (3), 1-(4-toluenesulfonyl)-4-(2-hydrazinocarbonyl)piperidine (5), and 1-(4-toluenesulfonyl)-4-[1-(methyl amino thiocarbonyl)-2-hydrazinocarbonyl]piperidine (7). The target molecules, 1-(4-toluenesulfonyl)-4-[3-(N-alkyl/phenyl/aryl-2-ethanamoyl thio)-4-methyl-4H-1,2,4-triazol-5-yl] piperidine (12a-o), were achieved through the reaction of 8 with N-alkyl/phenyl/aryl-2-bromo ethanamides (11a-o) as electrophiles. These electrophiles were accomplished by a benign reaction of alkyl/phenyl/aryl amines (9a-o) and 2-bromo ethanoyl bromide (10). The spectral study of IR, 1D-NMR, and EI-MS corroborated the synthesized compounds. Methyl phenyl and methyl phenyl-substituted derivatives 12d and 12m with IC₅₀ = 0.73 ± 0.54; 36.74 ± 1.24; 19.35 ± 1.28; 0.017 ± 0.53; and 0.038 ± 0.50 μM are found to be the most potent AChE, α-glucosidase, urease, and BChE inhibitors. The high inhibition potential of synthesized molecules against AChE, α-glucosidase, urease, and BChEenzymes inferred their role in enzyme inhibition properties.

Synthetic heterocyclic derivatives as promising xanthine oxidase inhibitors: An overview

Inhibition of xanthine oxidase is an effective and most prominent therapeutic approach for the management of gout. Discovery of its association in the pathophysiology of diabetes, cardiovascular disorders, etc., widened its therapeutic horizons. Limited drug candidates in clinical practice along with side effects forced researchers to develop more efficacious and safer xanthine oxidase inhibitors for the management of gout and other disorders associated with xanthine oxidase hyperactivity. In this regard, this review focus on: (a) Various drug candidates in clinical practice and under clinical trials, (b) Development of various heterocyclic motifs as xanthine oxidase inhibitors in last two decades and (c) Various patented synthetic xanthine oxidase inhibitors.

Monoterpene-based metallophthalocyanines: Sustainable synthetic approaches and photophysical studies

Tetra-substituted zinc(II) and copper(II) phthalocyanines bearing peripheral alkoxy-monoterpene groups were prepared by conventional vs. non-conventional synthetic approaches (ultrasound and microwave irradiation). The synthesis of (1[Formula: see text]-(–)-myrtenol (a) and (1[Formula: see text],2[Formula: see text],5[Formula: see text]-([Formula: see text]-menthol (b) derived phthalonitrile precursors was performed through ipso-nitro aromatic substitution reactions, with optimal conditions being obtained using ultrasound irradiation, which allowed us to achieve full conversions in 4.5 h, with isolated yields up to 74%. The subsequent cyclotetramerization of monoterpene-based phthalonitriles was carried out using Zn(II) or Cu(II) salts as metal templates, and also using conventional and non-conventional heating methods. Microwave-assisted synthesis was shown to be the most efficient approach, providing complete conversions in 1 h, yielding the target monoterpene-based metallophthalocyanines in up to 70% isolated yields. Furthermore, photophysical and photochemical studies revealed that Zn(II) phthalocyanines possess fluorescence quantum yields in the range of [Formula: see text] 0.27–0.29, while Cu(II) phthalocyanines exhibited room temperature phosphorescence. In addition, the monoterpene-based Zn(II) phthalocyanines led to high singlet oxygen quantum yields ([Formula: see text] 0.55–0.69).

Microwave-Assisted Expeditious Synthesis of 2-Alkyl-2-(N-arylsulfonylindol-3-yl)-3-N-acyl-5-aryl-1,3,4-oxadiazolines Catalyzed by HgCl₂ under Solvent-Free Conditions as Potential Anti-HIV-1 Agents

A series of 2-alkyl-2-(N-arylsulfonylindol-3-yl)-3-N-acyl-5-aryl-1,3,4-oxadiazolines were expeditious prepared under microwave-assisted, catalyzed by HgCl₂ and solvent-free conditions. This method has the advantage of low catalyst loading and recovering catalyst, ease reaction and repaid reaction times, easy separation products and excellent yields, and more conducive to the large-scale synthesis products. Furthermore, compounds 3s, 3y, 3a', 3b', 3f', 3i', 3q', and 3r' exhibited more potent anti-HIV-1 activity with EC50 values of 3.35, 6.12, 3.63, 9.54, 1.79, 0.51, 3.00, and 4.01 μg/mL, and TI values of 32.66, >32.68, 31.22, 13.94, 24.27, 39.59, 26.01, and 24.51, respectively. Especially compound 3i' displayed the highest anti-HIV-1 activity with TI values of 39.59.

Morpholinyl dendrimer phthalocyanine: synthesis, photophysical properties and photoinduced intramolecular electron transfer

The photophysical properties of a novel series of morpholinyl dendrimer phthalocyanines exhibited dependence on the number of morpholinyl groups and the central ion. The photoinduced electron transfer from the morpholinyl units to phthalocyanine ring was evidenced.

Discotic liquid crystals of transition metal complexes, 54: Rapid microwave-assisted synthesis and homeotropic alignment of phthalocyanine-based liquid crystals

The most difficult problem on syntheses of the phthalocyanine-based liquid crystals is the long reaction time. In order to shorten the reaction time, we have developed novel Methods A, B and D, for the syntheses of phthalocyanine-based liquid crystals by using microwave heating and/or adding a phase transfer catalysis of Aliquat 336. A series of phthalocyanine derivatives C[Formula: see text]PcZn(1) ([Formula: see text] 10, 12, 14, 16 and 18: a, b, c and e) could be successfully synthesized in a dramatically short reaction time of 30–60 min using Methods A and B by microwave heating. On the other hand, anothor series of the derivatives C[Formula: see text](OH)PcZn (2a–2e) could not be synthesized by microwave heating. Therefore, all these derivatives were synthesized using conventional Method C by oil bath heating, but the reaction took a very long time (22.5–88 h). To shorten the reaction time, we have developed Method D by oil bath heating with adding a phase transfer catalyst of Aliquat 336. In this method, we successfully shortened the reaction time from 88 h to 3 h for the synthesis of the derivative 2a. Thus, the reaction time for oil bath heating can be also greatly shortened by adding the phase transfer catalyst of Aliquat 336. Furthermore, we have established from POM, DSC and temperature-dependent X-ray diffraction measurements that the derivative C[Formula: see text]PcZn (1a) shows a very rare pseudohexagonal columnar (Col[Formula: see text] phase, and that the derivatives C[Formula: see text]PcZn (1b–1e) and C[Formula: see text](OH)PcZn (2b–2e) exhibit spontaneous perfect homeotropic alignment in a large area between two glass plates in their Col[Formula: see text] phases.

Microwave-Assisted Syntheses of Bioactive Seven-Membered, Macro-Sized Heterocycles and Their Fused Derivatives

This review describes the recent advances in the microwave-assisted synthesis of 7-membered and larger heterocyclic compounds. Several types of reaction for the cyclization step are discussed: Ring Closing Metathesis (RCM), Heck and Sonogashira reactions, Suzuki-Miyaura cross-coupling, dipolar cycloadditions, multi-component reactions (Ugi, Passerini), etc. Green syntheses and solvent-free procedures have been introduced whenever possible. The syntheses discussed herein have been selected to illustrate the huge potential of microwave in the synthesis of highly functionalized molecules with potential therapeutic applications, in high yields, enhanced reaction rates and increased chemoselectivity, compared to conventional methods. More than 100 references from the recent literature are listed in this review.

Eco-friendly microwave synthesis of Mg(ii) phenoxy carboxylic acid coordination compounds with specific motifs driven by multiple hydrogen bonding

Four magnesium complexes with specific motifs driven by multiple hydrogen bonding were synthesized by microwave method. The design strategy presented here gave an insight into the further structural prediction of magnesium supramolecular assemblies.