Efficient removal of sparfloxacin antibiotic from water using sulfonated graphene oxide: Kinetics, thermodynamics, and environmental implications

Pharmaceutical contamination poses a significant threat to global health. Due to their high solubility in water, antibiotics are difficult to remove. This study produced and used sulfonated graphene oxide (SGO) to adsorb sparfloxacin from aquatic environments. UV-Visible, Fourier transform infrared (FTIR), X-ray diffraction (XRD), XPS, SEM, TEM, EDX, particle size, Thermogravimetric analysis (TGA), and acid-base titration were used to characterize synthesized SGO particles. The BET technique determined SGO's surface area (32.25 m2/g). The calculated pHPZC of SGO was 2.5. Sparfloxacin adsorption onto SGO was analyzed using adsorption duration, medium pH, adsorbent dosages, antibiotic concentration, cations, and solution temperature. The pseudo-second-order kinetic model better described experimental kinetic data than the pseudo-first-order and Elovich models. Equilibrium isotherm data supported the Langmuir model, revealing a peak absorption capacity of 1428.57 μmol/g at 25 °C. The kinetic and isotherm models' applicability was assessed using error analysis. A thermodynamic analysis revealed an endothermic, spontaneous adsorption process with a change in entropy (ΔS) of 114.15 J/mol K and enthalpy (ΔH) of 8.44 kJ/mol. A regeneration analysis showed that SGO adsorption efficiency topped 86.4 % after five cycles.

Magnetic poly(1,8-diaminonaphthalene)-nickel nanocatalyst for the synthesis of antioxidant and antibacterial isoxazole-5(4H)-ones derivatives

A magnetic poly (1,8-diaminonaphthalene)-nickel (PDAN-Ni@Fe₃O₄) composite as a multifunctional nanocatalyst was prepared in several steps including (I) synthesis of poly (1,8-diaminonaphthalene) (PDAN), (II) modification of PDAN with NiSO₄ (PDAN-Ni) and (III) preparation of magnetic nanocatalyst by iron (I and II) salts in the existence of PDAN-Ni complex (PDAN-Ni@Fe₃O₄). Fourier-transform infrared spectroscopy (FTIR), elemental analysis (CHNSO), vibrating-sample magnetometer (VSM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), field emission scanning electron microscope (FESEM), ultraviolet-visible (UV-vis), and thermogravimetric analysis (TGA) were applied to characterize the prepared nanocatalyst. The PDAN-Ni@Fe₃O₄ was applied as an environmentally friendly nanocatalyst for the isoxazole-5(4H)-ones synthesis via a one-pot reaction between aryl/heteroaryl aldehyde, hydroxylamine hydrochloride, and β-ketoester. The nanocomposite was also used for the synthesis of some new alkylene bridging bis 4-benzylidene-3-methyl isoxazole-5(4H)-ones. The catalyst's reusability, and the antioxidant and antibacterial activities of both catalyst and products, were studied. Results showed that the nanocatalyst and isoxazole-5(4H)-ones have antioxidant activity of 75% and 92%, respectively. In addition, the antibacterial test showed that the nanocatalyst and isoxazole-5(4H)-ones have highly active versus Staphylococcus aureus and Escherichia coli bacteria. The reusability and stability of the nanocatalyst, a medium to higher product yield and conversion, a faster reaction time, and the use of green solvents were a few benefits of this study.

β-Cyclodextrin: a green supramolecular catalyst assisted eco-friendly one-pot three-component synthesis of biologically active substituted pyrrolidine-2-one

A green, novel and eco-efficient synthetic route towards the synthesis of highly substituted bio-active pyrrolidine-2-one derivatives was demonstrated using β-cyclodextrin, a water-soluble supramolecular solid as a green and eco-benign catalyst at room temperature under water-ethanol solvent medium. The exploration of the green catalyst β-cyclodextrin for the metal-free one-pot three-component synthesis of a wide range of highly functionalized bio-active heterocyclic pyrrolidine-2-one moieties from easily available aldehydes and amines explains the superiority and uniqueness of this protocol.

Carbocatalysis: a metal free green avenue towards carbon–carbon/heteroatom bond construction

Indeed, all the heterocycles comprises of either “C–C, C–N, C–S or C–O” bonds in their skeleton and construction of these bonds has laid the foundation stone of organic chemistry. The present researchers are continually attempting to develop new strategies for synthesizing miscellaneous structurally divergent molecular entities and these bond forming reactions are the fundamental tools. As a consequence, a colossal upheaval is witnessed in development of benign and sustainable synthetic routes for green bond-forming reactions envisaging carbon–carbon/heteroatom. This chapter is aimed towards highlighting the recent developments perceived in “C–C, C–N, C–S or C–O” bondconstruction especially emphasising greener perspectives i.e. carbocatalysis.

Catalytic applications of graphene oxide towards the synthesis of bioactive scaffolds through the formation of carbon–carbon and carbon–heteroatom bonds

During the past several decades, metal-based catalysis is one of the major and direct approaches for the synthesis of organic molecules. Nowadays, materials containing predominantly carbon element which are termed as carbocatalysts, become the most promising area of research to replace transition metal catalysts. In this context of carbocatalysis, the use of graphene oxide (GO) and GO-based materials are under spotlight due to their sustainability, environmental benignity and large scale-availability. The presence of oxygen containing functional groups in GO makes it benign oxidant and slightly acidic catalyst. This chapter provides a broad discussion on graphene oxide (GO) as well as its preparation, properties and vast area of application. The catalytic activity of GO has been explored in different organic transformations and it has been recognized as an oxidation catalyst for various organic reactions.

β-Cyclodextrin: a supramolecular catalyst for metal-free approach towards the synthesis of 2-amino-4,6-diphenylnicotinonitriles and 2,3-dihydroquinazolin-4(1H)-one

β-Cyclodextrin, a green and widespread supramolecular catalyst, has been explored as a highly proficient promoter for the metal-free one-pot multi-component synthesis of a vast range of highly functionalized bioactive heterocyclic moiety, 2-amino-4,6-diphenylnicotinonitriles and 2,3-dihydroquinazolin-4(1H)-one, from easily available precursor aldehydes. The main endeavor of these protocols is to explore this organic supramolecule in one-pot multi-component synthesis. Absence of metal catalyst or toxic acid and harsh reaction conditions, excellent functional group tolerance, inexpensive, greener and environmentally safe protocol are the key advantages of this work.

Magnetization of biochar nanoparticles as a novel support for fabrication of organo nickel as a selective, reusable and magnetic nanocatalyst in organic reactions

Waste recycling is important process in green chemistry and economic efficiency. Herein, magnetized biochar nanoparticles were modified under green and environmentally friendly method and further were applied as reusable catalyst in organic reactions.

Asymmetric Synthesis of Isoxazol-5-ones and Isoxazolidin-5-ones

Isoxazol-5-ones and isoxazolidin-5-ones represent two important classes of heterocycles, with several applications as bioactive compounds and as versatile building blocks for further transformations. Unlike the parent aromatic isoxazoles, the presence of one or two stereocenters in the ring renders their asymmetric construction particularly important. In this review, starting from the description of general features and differences between these two related compound families, we present an overview on the most important enantioselective synthesis strategies to access these heterocycles. Both chiral metal catalysts and organocatalysts have recently been successfully employed for this task and some of the most promising approaches will be discussed.

1 Introduction

2 Isoxazol-5-ones as Nucleophiles

2.1 Isoxazol-5-ones as C-Nucleophiles

2.2 Isoxazol-5-ones as N-Nucleophiles

2.3 Isoxazol-5-ones as C-Nucleophiles in Cyclization Processes

3 Asymmetric Construction of Isoxazolidin-5-ones

3.1 Enantioselective α-Functionalizations of Isoxazolidin-5-ones

4 Arylideneisoxazol-5-ones in Conjugated Addition

5 Conclusions

[18-C-6H3O+]: an in-situ generated macrocyclic complex and an efficient, novel catalyst for synthesis of pyrano[2,3-c]pyrazole derivatives

Synthesis of small aromatic heterocycles is of greater importance in the organic chemistry due to their vibrant applications in pharmaceuticals, agrochemicals and veterinary products. Pyranopyrazoles are one such class of heterocycles associated with numerous applications. Hence herein we report a multicomponent crown ether catalyzed, ultrasound irradiated methodology to make different functionalized pyranopyrazoles in a single step. This technique involves the in-situ generation of [18-C-6H₃O⁺][OH⁻] complex, which in turn activates the aromatic aldehyde and aids in the facile nucleophilic addition.

Graphene-based carbocatalysts for carbon-carbon bond formation

Organic transformations are usually catalyzed by metal-based catalysts. In contrast, metal-free catalysts have attracted considerable attention from the viewpoint of sustainability and safety. Among the studies in metal-free catalysis, graphene-based materials have been introduced in the reactions that are usually catalyzed by transition metal catalysts. This review covers the literature (up to the beginning of April 2020) on the use of graphene and its derivatives as carbocatalysts for C-C bond-forming reactions, which are one of the fundamental reactions in organic syntheses. Besides, mechanistic studies are included for the rational understanding of the catalysis. Graphene has significant potential in the field of metal-free catalysis because of the fine-tunable potential of the structure, high stability and durability, and no metal contamination, making it a next-generation candidate material in catalysis.