Current Green Chemistry - Volume 12, Issue 3, 2025

Nitrogen-containing acyclic, cyclic, and heterocyclic compounds and their derivatives have received increasing attention as a source of therapeutic agents. Oximes are an interesting class of Nitrogen-containing compounds possessing a wide variety of applications. Over the last decade, the interest in oximes and their derivatives has intensified. Many oxime derivatives using several preparation methods have been developed and evaluated for their biological activities. Due to their importance, oximes are subjected to many chemical transformations with the use of different chemicals to obtain numerous new derivatives. As a part of the continuing interest in oxime derivatives, we aim in this review to explore the green chemistry principles for the synthesis of oxime derivatives, as it offers promising pathways to more sustainable synthesis techniques that minimize waste and energy consumption and avoid hazardous methods. Additionally, it could inspire and stimulate researchers from various disciplines, such as chemists, biologists, and materials scientists to explore new applications for oximes derivatives.

The review paper presents an overview of the emerging trends in the synthesis of 2-iminopyrans. Iminopyran derivatives have shown significant potential in various fields such as pharmacology, cosmetics, and agrochemicals. Among the functionalized iminopyrans, 2-iminopyrans have gained significant attention due to their diverse biological activities and crucial role as intermediates in chemical synthesis. However, the traditional approach has limitations such as low yields and long reaction times. The paper explores the recent advancements in the synthesis of 2-iminopyrans, particularly emphasizing the reaction mechanisms involved, of these compounds. The review aims to spark readers' interest in developing more practical and environmentally friendly synthetic routes by providing a roadmap for synthesizing 2-iminopyrans.

Molecules of natural origin play a profound role in drug discovery and development since natural products derived from Mother Nature, particularly from plants are employed as satisfactory precursors for important medicines. The total synthesis of complex natural products endures as a dynamic field of chemical research as the demand for bioactive natural products and secondary metabolites is gradually enhancing owing to their great application in the area of synthetic organic chemistry and the biological community. It is very useful in ascertaining the hypothetical complex structure of such molecules in the laboratory since different biologically potent secondary metabolites are derived in small quantities frequently. The total synthesis of natural products using organocatalysis as the key step(s) has earned momentum recently because of high chemical efficiency, low toxicity, simple accessibility, low cost, and eco-friendly of organocatalysts due to the absence of a metal atom as well as the popularity of asymmetric catalysis research. This greener strategy is capable enough to execute the transformations at ambient temperature as per the sixth principle of green chemistry which is dedicated to the “Design for Energy Efficiency”. Cinchona alkaloids, chiral secondary and primary amines, guanidine and guanidiniums, N-heterocyclic carbenes, etc. are important organocatalysts in the field of the total synthesis of natural products and related compounds. Thus, the present review aims to deal with the total synthesis of natural products at room temperature as crucial intermediate(s) and it also offers an overview of natural sources, structures, and biological activities of natural products for the first time modishly.

Quinoline is a biologically important class of N-based heterocyclic compound. It has attracted the attention of the researchers since the 19^th century. The researchers have identified more than 600 quinoline compounds to date. Further, these exhibit several biological activities such as antibacterial, antifungal, antimalarial, antiviral, anti-inflammatory, antiparasitic, insecticidal, and other activities. Microwave-assisted synthesis is a promising green technique for synthesizing organic and heterocyclic compounds. The present review provides an overview of the literature available on microwave-promoted synthetic methodologies for the synthesis of quinoline derivatives that have appeared in the last ten years. Since the major goal of this work is to highlight the sustainable nature of microwave-promoted methods, the green features of each research report are presented. It covers recent synthetic strategies both under homogeneous and heterogeneous catalytic approaches. Significant decreases in reaction times, enhancement in overall yields, and greater atom economy can be observed in the documented research. We believe that this work will definitely help in the search for novel and environmentally benign routes for the synthesis of quinoline-related potential lead molecules.

A convenient and general method has been developed for the synthesis of fully and diversely functionalized pyrans via one-pot three-component reactions of various aryl or heteroaryl aldehydes, malononitrile, and 1,3-dimethyl/1,3-diethyl-acetonedicarboxylates in the presence of a catalytic amount of sodium formate as an efficient organocatalyst in aqueous ethanol at room temperature. All the scaffolds were synthesized in excellent yields within 2.5 hours. Under the same reaction conditions, fully and diversely functionalized spiro-pyrans were also synthesized in excellent yields from the reaction of isatin, malononitrile, and 1,3-dimethyl/1,3-diethyl-acetonedicarboxylates. All the products were isolated pure just by simple filtration. Synthesis of fully and diversely functionalized biologically promising pyrans, excellent yields, use of organocatalyst, less toxic solvent, no column chromatographic purification, and energy efficiency are some of the major advantages of this newly developed protocol.

The increasing environmental challenges posed by non-degradable plastics have spurred the development of biodegradable polymers as sustainable alternatives. This review explores the biodegradation processes, highlighting the role of microorganisms in breaking down polymers, and outlines the chemical transformations involved. Various factors influencing biodegradability, such as temperature, pH, and microbial species, are examined. The review also provides a detailed analysis of biodegradability testing standards set by ASTM, OECD, and ISO to assess the environmental impact of these materials. Synthesis techniques for biodegradable polymers from both natural and synthetic sources are discussed, along with their industrial applications in packaging, agriculture, medicine, and more. Key findings suggest that biodegradable polymers offer a viable solution to reducing pollution, carbon emissions, and reliance on petroleum-based products. The future direction for research emphasizes enhancing material properties and expanding applications to foster a sustainable approach to addressing global environmental concerns.

The concept of bioelectricity has been known for over half a century. Its modern application in the form of a battery or fuel cell utilizing microbes and degradable organic molecules opens up a new domain of energy production in the form of Microbial fuel cells (MFC). This technology not only supports the sustainable development goals by being green and but also facilitates the utilization of a wide range of biosubstrates, leading to coupled applications like wastewater treatment, desalination, etc. The development of viable models of MFC and their possible scale-up for use is a major focus of the researchers as the global energy crisis increases and the search for alternatives widens. The construction, configuration, electrodes, electrolytes, and microorganisms used play a very relevant role in determining the performance, longevity, and utility of MFC. Furthermore, exploration of the underlying biochemical mechanisms and influence of MFC components on it leading to variabilities in coulombic efficiencies and power output are key areas underlying its development. This review attempts to present a cohesive summary of important achievements in the development of MFC research attempted globally.

The objective of this work is to study MOFs with ligands containing thienothiophene groups as linkers and evaluate their practical application as sorbents for mercury removal from water. This evaluation will be compared with MOFs containing 2,6-naphthalenedicarboxylic acid and terephthalic acid linkers.

The study of Hg²⁺ sorption from solutions was carried out by shaking the MOFs (10 mg) with the solution at 25°C for 24 hours. Determination of chemical elements in solutions was performed using an Agilent 8800 triple quadrupole ICP-MS spectrometer (ICP-QQQ) equipped with an octopole reaction-collision cell in a standard configuration.

Within 24 hours, 97.8% of Hg²⁺ ions were removed from the solution, even at an initial Hg²⁺ concentration as low as 1 mg∙L^-1. An important part of the work was studying the possibility Zr-ttdc regeneration for repeated use. Using iodide solution as a desorbing agent proved more productive, ensuring the desorption of Hg²⁺ through competitive complex formation due to the high stability constants of the corresponding mercury complexes. With a 0.1 M potassium iodide solution at pH 6.5, 99% of the sorbed mercury was desorbed in one desorption cycle.

The efficiency of [Zr6O4(OH)4([3.2-b]ttdc)6] in adsorbing mercury from aqueous solutions was thoroughly evaluated and compared to [Zr6O4(OH)4(bdc)6] and [Zr6O4(OH)4(2.6-ndc)6], which lack sulfur-containing linkers. The findings highlight the potential of functionalized MOFs for water purification as well as application in analytical chemistry for the concentration of mercury. Notably, [Zr6O4(OH)4([3.2-b]ttdc)6] demonstrated stability in water in a wide pH range, underscoring its promise for diverse environmental chemistry applications.