Mini-Reviews in Organic Chemistry - Volume 21, Issue 6, 2024

Diphenyl ethers (DPEs) are mainly produced by microorganisms and plants. The chemical structure of DPEs is relatively simple, and all of these compounds have the structure of biphenyl ethers in their chemical structure, the difference being the difference in the substituents on the benzene ring. Several recent studies have shown antibacterial, antioxidant, antitumor, antitumor, antihemolytic, neuroprotective, and anti-Alzheimer effects. DPEs could be candidate compounds for the treatment of Alzheimer's disease, by inhibiting the aggregation of Aβ42. Many DPEs from natural products exhibit good biological activity and they play an important role in the control of microbial infections. Diphenyl ethers have a wide range of applications and research value in the fields of pesticides, pharmaceuticals, textiles, household products, and public health. In this paper, we review the research progress of diphenyl ethers isolated from marine and plant endophytic sources in recent years, including their biosynthesis, and lay the foundation for further utilization and development.

2-Oxindole unit is one of the most important scaffolds found in several alkaloids, natural products, antitumor agents, pharmaceutically important compounds, etc. Molecules containing the 2- oxindole moiety were first isolated from the cat claw plant, widely distributed in the Amazon jungle. It has now been demonstrated that these molecules are present in a wide range of chemicals derived from plant sources. The capacity of 2-oxindole to be altered by various chemical groups to provide unique biological activities can be attributed to its function as a chemical framework for creating and developing biological medications. Since the development of its first synthetic methodology, several research groups have developed protocols for producing 2-oxindole core and its bioactive derivatives. These include the traditional method and the transition/non-transition metal-catalyzed pathway for the synthesis of C3-non-substituted/C3-mono-substituted/C3-di-substituted core. Among those, C3-substitution-free 2-oxindole core synthesis is quite a challenging task, as C3-centre is very reactive. Syntheses of C3-substitution-free 2-oxindole cores have been less explored compared to other substituted 2-oxindole derivatives. In this review article, we have mainly focused on showcasing the transition metal-catalyzed synthetic methodology for the synthesis of 2-oxindoles with no substitution at C3-centre.

According to the European Environment Agency, the textile industry is responsible for 20% of global water pollution due to dyeing and finishing products, thus facing severe environmental challenges. It is essential to design more biocompatible and sustainable treatment processes capable of removing dyes from industrial wastewater to fight this environmental hazard. Chemical industries must change traditional chemical-based concepts to more environmentally friendly and greener processes to remove pollutants, including dyes. Enzymatic bioremediation is a smart tool and a promising alternative for environmental pollutant degradation. The use of enzymes in dye decolourization makes the process a green and clean alternative to conventional chemical treatments. Moreover, enzymemediated biocatalysis decreases the formation of toxic by-products compared to chemical reactions. The most used enzyme for the decolourization of dyes is laccase. Laccase is a multicopper oxidase found in diverse organisms such as fungi. It promotes the oxidation of phenolic compounds and has a wide range of substrate specificity, making it a promising enzyme for removing different dyes used by the textile industry, including recalcitrant aromatic dyes. The present article gives a comprehensive revision of textile dye decolourization, its types, recent developments in laccase-mediated dye bioremediation technologies, the mechanism of biocatalysis, and their limitations and challenges. Emphasis on the chemical pathways of laccase reaction mechanisms for dye bioremediation processes is also provided. In addition, a brief overview of textile industries and the respective traditional treatment processes for textile wastewater is presented.

Laccase (Benzenediol: oxygen oxidoreductase; E.C.1.10.3.2), a multicopper oxidase that is a known lignin-degrading enzyme, can catalyse an ample array of substrates, from phenolic, nonphenolic compounds, aromatic amines, diamines, heterocyclic compounds to organic/inorganic metal compounds, etc., bestowed they have not too high redox potentials. Despite many laccase-producing organisms like bacteria, insects, plants, and animals, white rot filamentous fungi are the best producers of this enzyme. In the presence of laccase, pesticides (fungicides, herbicides, insecticides, etc.) of various chemical compositions (organophosphates, organochlorines, carbamates, pyrethrin & pyrethroids, etc.) are oxidized into the water with collateral reduction of four electrons of molecular oxygen with various efficiencies. Bioremediation efficiency can be increased in the presence of various natural or synthetic mediators, viz. ABTS, violuric acid, 1- hydroxy benzotriazole, vanillin, syringaldehyde, PEG, etc. Immobilized laccase on various supporting materials increased the enzyme's stability, reliability, and reusability for continuous application, particularly for industrial processes. The present review discusses the structure, catalytic cycle, general mechanism of oxidation, and various scopes and challenges of pesticide degradation by this multifaceted biocatalyst which could lead to a green sustainable environment.

Sensor arrays contain a group of sensors, improve observations with new dimensions, provide better estimations, and additional parameters in comparison to the individual selective sensor. The array-based sensing technique provides good performance to respond to various gaseous or liquid analytes. Room temperature ionic liquids (RTILs) (melting point <25°C) and Group of uniform materials based on organic salts (GUMBOS) (melting point =25-250°C) are organic ionic salts, composed of an oppositely charged pair of bulky organic cations and bulky organic/inorganic anion and shows interesting tunable physicochemical properties. In this review article, we will discuss the sensing performance of ILs- and GUMBOS-based sensor arrays. ILs-based sensor arrays have been used in electrochemical gas sensing, solvent discrimination, colorimetric gas sensing, sensing of organic compounds, optoelectronic sensing of vapors and solutions, and vapour sensing through IL/QCM systems. GUMBOS-based sensor arrays have been employed in vapour sensing through the GUMBOS/QCM method, detection, and discrimination of proteins.

Several thieno [2,3-h] /[3,2-h] quinolines and thieno [2,3-f] /[3,2-f] quinolines (TQs) are discussed in this review from a few perspectives, including various preparation and processing methods employing cutting-edge machinery. The preparation of (TQs), from 4-(5)aminobenzothiophene, 2(3)chloromethylthiophene, 2(3)thienylboric acid, and other chemical reagents is illustrated via a number of chemical procedures in this review. The formation of (TQs) was clarified using the Michael addition, Photocyclization, Skraup reaction, Ullmann-Fetvadjian process, Suzuki-Miyaura and Sonogashira reaction, aza-Diels-Alder reaction, and Friedel-Crafts reaction.

Heterocyclic compounds are amongst the most promising and versatile classes of biologically important molecules. One of the heterocycle molecules is pyrazole with a five-membered heterocyclic ring with two neighboring nitrogen. Pyrazole and its derivatives have shown a broad range of biological applications like antibacterial, antifungal, antiviral, anti-inflammatory, anti-cancerous, and herbicidal activities. The study of synthetic routes suggests three broad ways: cyclo-condensation of hydrazine and its derivatives on 1,3 difunctional systems, dipolar cycloadditions, and multicomponent reactions. The synthesis of pyrazoles involves the usage of a conventional catalyst and more progressive and efficient nanoparticles as catalysts. The use of nanocatalysts is grabbing the attention of researchers owing to their more efficacy and reproducibility, low cost, reusability, ease of production, etc. The current review is an epigrammatic study on the importance of pyrazole as a biologically important moiety, recent advances in the three aforementioned routes to synthesize pyrazole and its derivatives, and a brief on the importance of nanocatalysts.