Abstract: The indole nucleus is a well-known structural moiety, abundant in many natural products, pharmaceuticals, and specialty materials. There are various traditional routes to this synthetically important scaffold; among them, the Fischer indole method is the most dependable and versatile. However, traditional Fischer routes often use corrosive acids and non-green solvents and require high energy inputs, thereby overlooking environmental and sustainability aspects. In recent years, efforts have been made to develop greener pathways for the Fischer-indole reaction in line with green chemistry principles. The present review provides a comprehensive overview of green approaches to the Fischer-indole method, highlighting reactions mediated by water, ionic liquids, and other alternative green solvents, as well as solvent-free reactions, microwave-assisted reactions, recyclable catalyst-based reactions, and single-pot multicomponent protocols. Key aspects, including reaction efficiency and selectivity, catalyst regeneration, and waste minimization, are emphasized. The advantages and limitations of these green approaches are discussed, together with mechanistic insights into selected reactions, highlighting their potential to advance sustainable chemical practices and enable future applications.
Abstract: The increasing environmental challenges and the global demand for sustainable development have necessitated innovative and effective approaches in chemistry. This evolution has led to the development of a novel scientific and industrial concept known as “SMART Green Chemistry.” This review examines the future of green chemistry by highlighting the roles of three key elements—innovation, adaptability, and artificial intelligence (AI). Innovation drives the development of novel materials and the optimization of sustainable chemical reactions, while adaptive technologies enable continuous improvement in response to dynamic environmental and economic conditions. Meanwhile, AI offers significant potential in real-time decision-making, process automation, as well as predictive analytics, thereby enhancing resource management and waste reduction. Collectively, these approaches position SMART Green Chemistry as a framework that not only promotes sustainable operations but also redefines sustainability through data-driven decision-making. This transition aligns with global trends toward net-zero emissions and a circular economy. The integration of digital technologies with green chemistry is expected to accelerate molecular design, facilitate the discovery of green catalysts, and enable more efficient process development across industries such as pharmaceuticals, renewable energy, and environmental remediation. Ultimately, SMART Green Chemistry, supported by digital innovation and sustainability principles, represents a transformative approach to addressing pressing environmental challenges in an integrated and effective manner.
Abstract: Cross-coupling reactions are indispensable tools in the field of modern organic synthesis. However, they have traditionally relied on organic solvents and expensive transition-metal catalysts, both of which raise significant concerns regarding sustainability and environmental impact. This review highlights recent advances and emerging strategies for performing C-C cross-coupling reactions in water, emphasizing how these approaches align with the principles of green chemistry. Particular attention is given to key enabling technologies, including the development of water-soluble ligands, such as sulfonated phosphines, newly designed aminophosphines, and polyethylene glycol-based N-heterocyclic carbenes, which enhance catalyst compatibility with aqueous media. In addition, micellar catalysis has emerged as a powerful platform through the use of designer surfactants, enabling a wide range of transformations, including Suzuki-Miyaura, Sonogashira, Heck, and Negishi cross-couplings, to proceed efficiently in water. Heterogeneous catalytic systems and phase-transfer catalysis are also discussed as complementary strategies that facilitate cross-coupling reactions under aqueous conditions. The intrinsic advantages of water, including its non-toxic nature, low cost, abundance, and the unique hydrophobic effect that can accelerate chemical transformations, are critically evaluated alongside the remaining challenges, such as the limited solubility of organic substrates, catalyst deactivation, and the protodeboronation of boronic acids. Furthermore, mechanistic aspects unique to aqueous reaction media are examined together with industrial applications, including multi-kilogram-scale water-mediated cross-coupling processes developed by the pharmaceutical industry that demonstrate substantial reductions in waste generation and improvements in process efficiency. Finally, this review discusses current challenges, identifies future research directions, and highlights emerging trends, particularly the development of base-metal catalytic systems, which are expected to further expand the scope and sustainability of water-based C-C cross-coupling chemistry.
Abstract: The rapid increase in industrialization, technological and industrial hubs, and urbanization has raised serious environmental concerns; among them, water pollution has become a threat to the whole ecosystem. Currently, a variety of techniques are available for environmental engineering, such as adsorption, ion-exchange, chemical precipitation, etc. However, efficient and cost-effective treatment of water pollutants remains one of the World’s biggest challenges. In this context, dendrimer-based materials have recently attracted extensive research owing to their flexible synthesis, surface functional groups, free interior cavities, monodispersity, high solubility, low viscosity, scaffolding properties, biosafety, and the ability to assemble into nanoscale materials. This review provides a comprehensive overview of the synthesis strategies, structural characteristics, and functional properties of various dendrimer-based materials, with particular emphasis on their application in wastewater treatment through the adsorption of heavy metal ions. Additionally, this review identifies current limitations and knowledge gaps in the field, such as challenges related to large-scale synthesis, cost-effectiveness, regeneration, and long-term stability. Furthermore, future perspectives are discussed, focusing on the design of next-generation dendrimer systems with enhanced adsorption capacity, improved recyclability, and greater environmental compatibility. Overall, this review aims to provide a detailed and insightful resource to guide researchers in the rational design and fabrication of innovative dendrimer-based materials for sustainable water treatment applications.
Abstract: Over the last decade, visible-light-driven cross-coupling reactions have become a necessary alternative to traditional thermal methods across all types of cross-coupling. Herein, we delineate the highlights of recent progress in both transition metal-catalyzed and transition metal-free C‒S cross-coupling reactions under visible light-mediated conditions. In this review, we have discussed the pivotal roles of various transition-metal catalysts and photocatalysts in photo-redox C‒S cross-coupling reactions. The mechanistic pathway, green chemistry aspects, and the limitations are clearly discussed. Apart from transition-metal-based strategies, there are transition-metal-free visible-light-mediated C‒S cross-coupling approaches, which have gained significant attention owing to their green metrics. We have presented the various previous approaches that rely on organic photocatalysts or catalyst-free systems where visible light directly activates substrates to generate sulfur- or carbon-centered radicals, EDA (Electron Donor-Acceptor) complexes, halogen bond-assisted EDA complexes, or undergo reactions through the single-electron transfer (SET) and hydrogen atom transfer (HAT) mechanisms. The role of photocatalysts and visible light, the scope of substrates, and various green matrices are discussed in this review. The ongoing development of these two strategies is expected to further widen the substrate scope, improve mechanistic understanding, and enhance applicability in pharmaceutical and material chemistry.
