Zirconium(IV)-modified silica gel: Preparation, characterization and catalytic activity in the synthesis of some biologically important molecules

Copper borate (CuB4O7)-promoted multi-component green synthesis of 2,4,5-triarylimidazole derivatives and evidence of in situ conversion of copper borate (CuB4O7) into Cu(OAc)2 in the presence of NH4OAc

A green, efficient, and straightforward methodology for the three-component synthesis of 2,4,5-triarylimidazole has been developed under solvent-free conditions using unconventional CuB₄O₇ as a promoter. This green approach encouragingly provides access to a library of 2,4,5-tri-arylimidazole. Also, we have been able to isolate the compound (5) and (6) in situ, which provides an insight into the direct conversion of CuB₄O₇ into copper acetate in the presence of NH₄OAc under solvent-free condition. The main advantage of this protocol includes an easy reaction procedure, short reaction time, and easy work up of the product without using any tedious separation method.

Supported Metal Catalysts for the Synthesis of N-Heterocycles

Nitrogen-containing heterocycles are important scaffolds for a large number of compounds with biological, pharmaceutical, industrial and optoelectronic applications. A wide range of different methodologies for the preparation of N-heterocycles are based on metal-catalyzed cyclization of suitable substrates. Due to the growing interest in Green Chemistry criteria over the past two decades, the use of supported metal catalysts in the preparation of N-heterocycles has become a central topic in Organic Chemistry. Here we will give a critical overview of all the solid supported metal catalysts applied in the synthesis of N-heterocycles, following a systematic approach as a function of the type of support: (i) metal catalysts supported on inorganic matrices; (ii) metal catalysts supported on organic matrices; (iii) metal catalysts supported on hybrid inorganic-organic matrices. In particular, we will try to emphasize the effective heterogeneity and recyclability of the described metal catalysts, specifying which studies were carried out in order to evaluate these aspects.

Natural vs. Synthetic Phosphate as Efficient Heterogeneous Compounds for Synthesis of Quinoxalines

Natural phosphate (NP) and synthetic fluorapatite phosphate (SFAP) were proposed as stable, inexpensive, readily available and recyclable catalysts for the condensation of 1,2-diamines with 1,2-dicarbonyls in methanol to afford quinoxaline at room temperature. NP provided as high as 92-99% yield for quinoxalines in short reaction times (i.e., 1-45 min), while SFAP created quinoxalines with 87-97% yield in 60-120 min. From the chemical analyses, X-ray fluoresecency, X-ray diffraction, energy dispersive X-ray and Fourier-transform infrared spectroscopy methods, two main phases (CaO, P2O5) appeared in NP together with other low content phases (SiO2, Fe2O3). Compared to other phases, apatite (CaO and P2O5 as Ca10(PO4)6) played a major role in the catalytic activity of NP. SFAP with similar Ca/P atomic ratio showed a relatively lower catalytic activity than NP for the condensation of 1,2-diamine with 1,2-dicarbonyl in methanol at ambient temperature. To investigate the recyclability of catalysts, the surface properties of NP and 6-recycled NP were investigated using scanning electron microscopy, energy dispersive X-ray and Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods. Some differences were observed in NP and 6-recycled NP's particle size, surface area, the volume and size of pores, and the content of elements; nevertheless, the use-reuse process did not noticeably change the catalytic property of NP.

Novel Synthetic Routes to Prepare Biologically Active Quinoxalines and Their Derivatives: A Synthetic Review for the Last Two Decades

Quinoxalines, a class of N-heterocyclic compounds, are important biological agents, and a significant amount of research activity has been directed towards this class. They have several prominent pharmacological effects like antifungal, antibacterial, antiviral, and antimicrobial. Quinoxaline derivatives have diverse therapeutic uses and have become the crucial component in drugs used to treat cancerous cells, AIDS, plant viruses, schizophrenia, certifying them a great future in medicinal chemistry. Due to the current pandemic situation caused by SARS-COVID 19, it has become essential to synthesize drugs to combat deadly pathogens (bacteria, fungi, viruses) for now and near future. Since quinoxalines is an essential moiety to treat infectious diseases, numerous synthetic routes have been developed by researchers, with a prime focus on green chemistry and cost-effective methods. This review paper highlights the various synthetic routes to prepare quinoxaline and its derivatives, covering the literature for the last two decades. A total of 31 schemes have been explained using the green chemistry approach, cost-effective methods, and quinoxaline derivatives' therapeutic uses.

An insight into medicinal chemistry of anticancer quinoxalines

Quinoxalines are benzopyrazines containing benzene and pyrazine rings fused together. In the recent past, quinoxalines have attracted Medicinal Chemists considerably for their syntheses and chemistry due to their distinct pharmacological activities. Diverse synthetic protocols have been developed via multicomponent reactions, single pot synthesis and combinatorial approach using efficient catalysts, reagents, and nano-composites etc. Further, the versatility of the quinoxaline core and its reasonable chemical simplicity devise it extremely promising source of bioactive compounds. Therefore, a wide variety of bioactive quinoxalines has been realised as antitumour, antifungal, anti-inflammatory, antimicrobial, and antiviral agents. Already, a few of them are clinical drugs while many more are under various phases of clinical trials. Present review focuses on chemistry and pharmacology (both efficacy and safety) of quinoxalines and also provides some insight in to their structure-activity relationship.

Nickel stabilized by triazole-functionalized carbon nanotubes as a novel reusable and efficient heterogeneous nanocatalyst for the Suzuki–Miyaura coupling reaction

The synthesis of a MWCNT-grafted nickel catalyst through “click” reaction of azide-functionalized carbon nanotubes with propargyl alcohol, for the Suzuki–Miyaura coupling reaction.

Inorganic-organic hybrid silica based tin complex as a novel, highly efficient and recyclable heterogeneous catalyst for the one-pot preparation of spirooxindoles in water

In the present study, a tin complex immobilized on silica gel as a novel, green, highly efficient and heterogeneous reusable catalyst was synthesized by grafting 2-amino benzamide onto the silica gel surface as a result of the reaction between isatoic anhydride and 3-aminopropyl-functionalized silica gel, followed by complexing with tin chloride. The resulting organic-inorganic hybrid material was evaluated in the one-pot three-component synthesis of spiro[indoline-pyrazolo[4',3':5,6]pyrido[2,3-d]pyrimidine]trione derivatives in water via the condensation reaction of isatins, barbituric acids, and 1H-pyrazol-5-amines. All the reactions were completed in short reaction times and all the products were obtained in high to excellent yields with high purity. In addition, the synthesized novel catalyst could be separated from the reaction mixture by simple filtration and can be reused up to seven runs without significant loss in activity.

Magnetically retrievable silica-based nickel nanocatalyst for Suzuki–Miyaura cross-coupling reaction

A new magnetically recoverable silica-based nickel nanocatalyst was synthesized, characterized and applied for the first time as a catalyst in Suzuki–Miyaura cross-coupling reaction.

Shape-dependent catalytic activity of Fe3O4 nanostructures under the influence of an external magnetic field for multicomponent reactions in aqueous media

Fe₃O₄ nanostructures were synthesized under external magnetic field, shown shape-dependent catalytic activity for the synthesis of imidazole derivatives in water.

Quinoline-2-carboimine copper complex immobilized on amine functionalized silica coated magnetite nanoparticles: a novel and magnetically retrievable catalyst for the synthesis of carbamates via C–H activation of formamides

A novel and magnetically recoverable nanocatalytic system consisting of a magnetic silica based copper complex has been fabricated and applied in the synthesis of carbamates via C–H activation of formamides.

Silica nanospheres supported diazafluorene iron complex: an efficient and versatile nanocatalyst for the synthesis of propargylamines from terminal alkynes, dihalomethane and amines

A novel silica nanosperes supported diazafluorene iron complex has been fabricated and found to be effective in three-component coupling reaction of terminal alkynes, dichloromethane and amines.

An efficient protocol for the synthesis of quinoxaline derivatives at room temperature using recyclable alumina-supported heteropolyoxometalates

We report a suitable quinoxaline synthesis using molybdophosphovanadates supported on commercial alumina cylinders as catalysts. These catalysts were prepared by incipient wetness impregnation. The catalytic test was performed under different reaction conditions in order to know the performance of the synthesized catalysts. The method shows high yields of quinoxaline derivatives under heterogeneous conditions. Quinoxaline formation was obtained using benzyl, o-phenylenediamine, and toluene as reaction solvent at room temperature. The CuH₂PMo₁₁VO₄₀ supported on alumina showed higher activity in the tested reaction. Finally, various quinoxalines were prepared under mild conditions and with excellent yields.

Synthesis and anti-oxidant activity of (5E,9E)-16-(substituted)-7,8-dihydro-16λ(5) -dibenzo[d,l][1,3,7,10,2]dioxadiazaphosphacyclotridecine-16-ones

A new class of biologically active 13-membered phosphorus-macroheterocycles (6a-l) were conveniently synthesized from 1,2-bis(salicylidene amino)-phenylene (1), by treating with phosporusoxychloride (3) and followed by reacting with various aromatic thiols and amines (5f-l) in one path, and in another path 1 was directly treated with various phosphorodichloridates (2a-e) in the presence of triethylamine at 0-10°C under N(2) atmosphere in THF. All the title compounds were confirmed by analytical and spectral data (IR, (1) H-, (13) C-, (31) P-NMR, and mass spectra) and screened for anti-oxidant activity. Among these compounds, 6k, 6e, and 6l containing nitro, fluoro, and chloro groups as substituents on the phenyl ring exhibited high anti-oxidant activity with effective inhibitory concentration (IC(50) ) values.