Current Organic Chemistry - Volume 25, Issue 3, 2021

One of the major challenges in chemistry confronted by the chemists is the replacement of conventional homogeneous catalysts by heterogeneous catalysts for the development of green, sustainable and economical chemical processes. Recently, carbón-based nanocomposites have attracted the attention of scientists due to their unique physical and chemical properties such as large surface area and pore volume, chemical inertness, high stability and high electrical conductivity. These NCs have been employed in energy storage, electronic devices, sensors, environmental remediation etc. Owing to the wide availability and low cost, carbón-based materials have been utilized as supports for transition metals and other materials. The carbón-based NCs offer a number of advantages such as high stability, easy recovery, reusability with often minimal leaching of metal ions, and green and sustainable approaches to heterogeneous catalysis for various organic transformations. Hence, they can be used as the substitute for the existing catalyst used for heterogeneous catalysis in industries. In this review, various processing methods for carbón-based nanocomposites and their applications as heterogeneous catalysts for organic transformations like hydrogenation, oxidation, coupling, and multi component reactions, have been discussed.

The heterocyclic molecules are medicinally important and are applied in different other fields. The environmentally benign synthetic method for the synthesis of this important group of compounds is always explored. Bimetallic nanoparticles are getting attention as heterogeneous catalysts for their synthesis. The bimetallic nanoparticles have been usually synthesized by chemical or physical methods or both in combination. Chemists are also using part of plants in the synthesis of bimetallic nanoparticles and these have been successful. The present review work will be going to enrich the existing literature by compiling the use of plant parts in the synthesis of bimetallic nanoparticles and their utility in the synthesis of heterocyclic molecules.

Mesoporous silica nanomaterials provide an extraordinary advantage for making new and superior heterogeneous catalysts because of their surface silanol groups. The functionalized mesoporous SBA-15, such as acidic, basic, BrÖnsted, lewis acid, and chiral catalysts, are used for a wide range of organic syntheses. The importance of the chiral ligands, which were immobilized on the SBA-15, was mentioned in this review to achieve chiral products as valuable target molecules. Herein, their synthesis and application in different organic transformations are reviewed from 2016 till date 2020.

The heterocycle ring tetrazole is an important moiety relevant to medicinal chemistry since it is present in some drugs with clinical importance. Its primary biological activity is being a bioisosteric analogue of the carboxylic acid and cis-amide groups. Its metabolic stability and other physicochemical properties make it an attractive structure for designing and synthesizing new pharmaceuticals. The biological activity of tetrazoles is quite extensive and includes antiviral, antibacterial, anticancer, antifungal, and antioxidant properties; all of them are discussed in this review. The most effective way to obtain tetrazoles is by azide derivatives, either in the starting materials by the cycloaddition [3 + 2] of organic azides and nitriles or by preparing a reactive imidoyl azide intermediate. The nucleophilic behavior of the azide group is discussed when the raw materials include isocyanides. Some other methods include alternative synthetic routes like thermolysis. This review also highlights some of the developments regarding the use of different heterogeneous catalysts to synthesize several tetrazole derivatives.

Biomass has attracted much attention because of its clean and renewable characteristics. The conversion of biomass into various fine chemicals and high value-added fuels is one of the important ways to solve the energy shortage and environmental pollution. 2,5-furan dicarboxylic acid (FDCA), a kind of important and promising new bio-based monomer, has attracted the attention of many researchers due to its wide applications in different industries. Therefore, many efforts have been made over various metal catalysts for FDCA production from this biomass-derived platform chemical, 5hydroxymethylfurfural (HMF). In this review, we introduced the reaction pathways of the aerobic oxidation of HMF to FDCA and summarized the recent progress of different catalysts and catalysis for HMF aerobic oxidation. Catalytic performance and reaction pathways are discussed in detail. Finally, conclusions and the remaining challenges are proposed and further prospects are presented in view of the technical aspects.

As a kind of renewable nanomaterial, nanocellulose displays excellent performances and exhibits wide application potentials. In general, nanocellulose has strong hydrophilicity due to the presence of abundant hydroxyl groups or the hydrophilic functional groups introduced during the preparation process. Although these hydrophilic groups benefit the nanocellulose with great application potential that is used in aqueous media (e.g., rheology modifier, hydrogels), they do hinder the performance of nanocellulose used as reinforcing agents for hydrophobic polymers and reduce the stability of the self-assembled nanostructure (e.g., nanopaper, aerogel) in a high-humidity environment. Thus, this review aims to summarize recent advances in the hydrophobic modification of nanocellulose, mainly in three aspects: physical adsorption, surface chemical modification (e.g., silylation, alkanoylation, esterification), and polymer graft copolymerization. In addition, the current limitations and future prospects of hydrophobic modification of nanocellulose are proposed.