MnO2 on hydroxyapatite: A green heterogeneous catalyst and synthesis of pyran-carboxamide derivatives

Talc as a natural mineral catalyst for the one pot-three component synthesis of benzo[f]chromene, dihydropyrano[3,2-c]chromene, and tetrahydrobenzo[b]pyran derivatives under different conditions

Talc is a natural mineral catalyst known by the chemical composition of MgSi4O10(OH)2. which in its pure state consists of 31.88% magnesium oxide, 63.37% silicon oxide, and 4.75% water. The abundance of this material, the ease of extraction, and its properties have made talc an important mineral in industries. In this article, this material, which was extracted directly from the mine, after decontamination, was used for the synthesis of benzo[f]chromene, dihydropyrano[3,2-c]chromene, and tetrahydrobenzo[b]pyran derivatives. The results demonstrated that the catalyst exhibited excellent catalytic performance, leading to the production of products with yields of 79-95%. Additionally, the heterogeneity of the reaction was confirmed through a hot filtration test. Notably, this catalyst presents notable benefits, such as its easy recovery and ability to be reused for a minimum of six successive cycles, a simple work-up procedure, and the attainment of high product yields. Structural and morphological analyzes of the talc were done using Fourier Transform Infrared Spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Energy-dispersive X-ray Spectroscopy (EDS-map) and Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM) techniques.

MnO2 Doped with Ag Nanoparticles and Their Applications in Antimicrobial and Photocatalytic Reactions

A wide range of nanoparticles have been produced for photocatalysis applications. Nonetheless, degrading organic dyes requires nanoparticles that are efficient and excellent. As a photocatalyst, pure manganese oxide (MnO2) was prepared via a sol–gel method using silver (Ag) nanoparticles of transition metal oxide. In addition to X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX), the crystal structure and elemental composition were analysed. According to XRD data, the transition metal of MnO2 oxide is highly pure and has a small crystallite size. The presence of functional groups was confirmed and clarified using Fourier-transform infrared spectra (FTIR). By irradiating the transition pure and doped MnO2 photocatalysts with visible light, the UV-vis, μ-Raman, and surface areas were determined. As a result, of using the photocatalysts with aqueous methylene blue (MB) solutions under visible light irradiation, the MnO2 doped with Ag nanoparticles demonstrated high degradation efficiencies and were utilised to establish heterogeneous photocatalysis dominance. In this paper, we demonstrate that the photocatalytic efficiency of transition metal oxides is exclusively determined by the particle size and surface area of nano-sized materials. Due to their high surface charge ratio and different surface orientations, have the highest photocatalytic efficiency. Generally, MnO2 doped with Ag nanoparticles is resistant to bacteria of both Gram-positive and Gram-negative types (B. sublittus and Escherichia coli). There is still a need for more research to be performed on reducing the toxicity of metal and metal oxide nanoparticles so that they can be used as an effective alternative to antibiotics and disinfectants, particularly for biomedical applications.

Recent Progress in the Multicomponent Synthesis of Pyran Derivatives by Sustainable Catalysts under Green Conditions

Pyrans are one of the most significant skeletons of oxygen-containing heterocyclic molecules, which exhibit a broad spectrum of medicinal applications and are constituents of diverse natural product analogues. Various biological applications of these pyran analogues contributed to the growth advances in these oxygen-containing molecules. Green one-pot methodologies for synthesising these heterocyclic molecules have received significant attention. This review focuses on the recent developments in synthesising pyran ring derivatives using reusable catalysts and emphasises the multicomponent reaction strategies using green protocols. The advantages of the catalysts in terms of yields, reaction conditions, and recyclability are discussed.

Recent Progresses in the Multicomponent Synthesis of Dihydropyridines by Applying Sustainable Catalysts Under Green Conditions

The synthesis of dihydropyridines, valuable molecules with diverse therapeutic properties, using eco-friendly heterogeneous catalysts as a green alternative received significant consideration. By selecting appropriate precursors, these compounds can be readily modified to induce the desired properties in the target product. This review focused on synthesising diverse dihydropyridine derivatives in single-pot reactions using magnetic, silica, and zirconium-based heterogeneous catalytic systems. The monograph describes preparation techniques for various catalyst materials in detail. It covers facile and benign magnetic, silica, zirconium-based, and ionic liquid catalysts, exhibiting significant efficacy and consistently facilitating excellent yields in short reaction times and in a cost-effective way. Most of the designated protocols employ Hantzsch reactions involving substituted aldehydes, active methylene compounds, and ammonium acetate. These reactions presumably follow Knoevenagel condensation followed by Michael addition and intra-molecular cyclisation. The multicomponent one-pot protocols using green catalysts and solvents have admirably increased the product selectivity and yields while minimising the reaction time. These sustainable catalyst materials retain their viability for several cycles reducing the expenditure are eco-friendly.

Advances in Pyranopyrazole Scaffolds' Syntheses Using Sustainable Catalysts-A Review

Heterogeneous catalysis plays a crucial role in many chemical processes, including advanced organic preparations and the design and synthesis of new organic moieties. Efficient and sustainable catalysts are vital to ecological and fiscal viability. This is why green multicomponent reaction (MCR) approaches have gained prominence. Owing to a broad range of pharmacological applications, pyranopyrazole syntheses (through the one-pot strategy, employing sustainable heterogeneous catalysts) have received immense attention. This review aimed to emphasise recent developments in synthesising nitrogen-based fused heterocyclic ring frameworks, exploring diverse recyclable catalysts. The article focused on the synthetic protocols used between 2010 and 2020 using different single, bi- and tri-metallic materials and nanocomposites as reusable catalysts. This review designated the catalysts' efficacy and activity in product yields, reaction time, and reusability. The MCR green methodologies (in conjunction with recyclable catalyst materials) proved eco-friendly and ideal, with a broad scope that could feasibly lead to advancements in organic synthesis.

A plant-mediated synthesis of nanostructured hydroxyapatite for biomedical applications: a review

The engineering of calcium-based phosphate materials at the nanoscale gains several unique properties compared to the bulky state. The effort to scale down, e.g., from bulky state to nanoscale in order to control the morphology and improve structural properties requires the use of varying reagents that can be detrimental to the environment. A typical example of these materials is hydroxyapatite (HAp), one of the well-known calcium phosphate materials, which has a close resemblance to human bone tissue. HAp has valuable applications in catalysis, drug delivery, bone and dental implant formation, and adsorption. Hydroxyapatite-based nanomaterials synthesized through conventional routes make use of reagents that are not environmental friendly and are very costly. Since the current research trends are geared towards producing/synthesizing nanomaterials through an eco-friendly approach, there is the need to consider the techniques and reagents involved in the synthesis of HAp. This review touches on the possible replacement of such synthetic chemical reagents, synthesis routes, and toxic capping agents with plant extracts for synthesizing HAp-based nanomaterials for multi-functional applications. The influence of biomolecules from plants on synthesized HAps and the attainable mechanism during these green approaches are discussed. Viable future modifications of the methods used to obtain extracts from plants are also studied.