Synthesis and Applications of Carbohydrate-Based Organocatalysts

Organocatalysis is a very useful tool for the asymmetric synthesis of biologically or pharmacologically active compounds because it avoids the use of noxious metals, which are difficult to eliminate from the target products. Moreover, in many cases, the organocatalysed reactions can be performed in benign solvents and do not require anhydrous conditions. It is well-known that most of the above-mentioned reactions are promoted by a simple aminoacid, l-proline, or, to a lesser extent, by the more complex cinchona alkaloids. However, during the past three decades, other enantiopure natural compounds, the carbohydrates, have been employed as organocatalysts. In the present exhaustive review, the detailed preparation of all the sugar-based organocatalysts as well as their catalytic properties are described.

Quinoxaline as Ubiquitous Structural Fragment: An update on the recent development of its Green Synthetic Approaches

: Quinoxaline is a versatile heterocyclic moiety that possesses a wide range of biological activities. Therefore, many researchers have been performing the synthesis of quinoxaline derivatives on a daily basis. In addition, high demands for their synthesis often result in an increased generation of different waste chemicals. However, to minimize the utilization and generation of toxic organic substances, the present review focuses on the various green synthetic approaches for the synthesis of quinoxaline and its derivatives. Moreover, due to the quick manufacturing of novel medications using a quinoxaline scaffold, multiple study reports are published in a short period of time. Therefore, to fully comprehend the current state of the quinoxaline scaffold in medicinal chemistry, it is necessary to combine recent findings with previous understanding. Besides, compared to conventional methods, these green methods minimize the use and generation of harmful chemicals and improve reaction efficiency in terms of product yields, purity, energy consumption, and post-synthetic procedures. Therefore, in this review, we have attempted to shed light on various green synthetic strategies leading to the synthesis of quinoxaline scaffold and its derivatives, such as ultrasound irradiation, microwave irradiation, grindstone technique, environmentally benign solvents/catalysts based, and reactant immobilized on a solid support, etc.

Applications of Ionic Liquids in Green Catalysis: A Review of Recent Efforts

: Ionic Liquids (ILs) in their neoteric form have emerged to be a potential ‘green’ alternative of traditional Volatile Organic Compounds (VOCs) as solvents in different fields of industries and academia. Recent investigations on the development of multi-faceted applications of ionic liquids have revealed that they really stand for “environmentally-benign” solvents as far as their impact on the ecology is concerned. This caused them to be an exciting and lucrative subject to explore more and more, and many research groups are involved in the manifestation of their inherent undisclosed legacy. Recently, there has been a huge jump in search of an alternative to conventional metal catalysts in academia as well as in industries due to their pollution-evoking roles. Scientists have explored multiple numbers of homogeneous or heterogeneous mixtures of catalysts incorporating ionic liquids to reduce the extent of contamination in our global environment produced due to catalytic synthesis and chemical transformations. In this review, we have put our concentration on some beneficial and recently explored aspects of the successful implementation of Ionic Liquids in different forms in several fields of catalysis as a ‘green’ alternative catalyst/co-catalyst/solvent for catalysis to replace or minimize the lone and hazardous use of metal and metallic compounds as catalysts as well as chemicals like mineral acids or VOCs as solvents. Here, our study focuses on the inevitable role of ILs in several catalytic reactions like cycloaddition of CO2, electrolytic reduction of CO2, biocatalytic or enzymatic reactions, some of the important organic conversions, and biomass to biofuel conversion as catalysts, cocatalysts, catalyst activator, and solvents.

Foundry-compatible high-resolution patterning of vertically phase-separated semiconducting films for ultraflexible organic electronics

Solution processability of polymer semiconductors becomes an unfavorable factor during the fabrication of pixelated films since the underlying layer is vulnerable to subsequent solvent exposure. A foundry-compatible patterning process must meet requirements including high-throughput and high-resolution patternability, broad generality, ambient processability, environmentally benign solvents, and, minimal device performance degradation. However, known methodologies can only meet very few of these requirements. Here, a facile photolithographic approach is demonstrated for foundry-compatible high-resolution patterning of known p- and n-type semiconducting polymers. This process involves crosslinking a vertically phase-separated blend of the semiconducting polymer and a UV photocurable additive, and enables ambient processable photopatterning at resolutions as high as 0.5 μm in only three steps with environmentally benign solvents. The patterned semiconducting films can be integrated into thin-film transistors having excellent transport characteristics, low off-currents, and high thermal (up to 175 °C) and chemical (24 h immersion in chloroform) stability. Moreover, these patterned organic structures can also be integrated on 1.5 μm-thick parylene substrates to yield highly flexible (1 mm radius) and mechanically robust (5,000 bending cycles) thin-film transistors.

A Review on Green Synthesis and Biological Activities of Nitrogen and Oxygen Containing Heterocycles

Heterocycles are unique precursors for the synthesis of various pharmaceuticals and agrochemicals particularly those possessing N- or O- moieties. The development of methods to prepare heterocycles is of great importance in synthesis of organic compounds, especially the heterocycles which can be found in natural products. The synthesis of nitrogen and oxygen containing heterocycles viz. coumarins, dihydropyrimidinones, imidazoles, isoxazoles and benzimidazoles represented an attractive and demanding work for chemists as these nucleus has found extensive applications in several fields such as material science, analytical chemistry and most importantly in medicinal chemistry. Organic synthesis has been attracted towards the development of new environmental friendly procedures to achieve the goals of green chemistry. The fundamental aspects of green chemistry are use of biocatalysts and environmental benign solvents under mild conditions. The present review article summarized the green synthetic methods and biological activities of nitrogen and oxygen containing heterocycles.

Liquid-Phase Exfoliation of Biochars in Green Solvents and Correlation with Solvent Parameters

<div> <div> <div> <div> <p>Liquid-phase exfoliation (LPE) is a process frequently used to overcome the interactions between layers in layered materials to produce small sheets of material, with remarkable properties and high value applications. Materials are prepared via direct or indirect sonication in a solvent that must be able to effectively disperse and stabilize the sheets produced. Unfortunately, the preferred solvents for exfoliation processes are often toxic and possess several health risks. In this work, we show that LPE in greener solvents can be used to access nanostructures of biochar and further improve the applications of this renewable and bio-based material. Herein, pristine and oxidized biochars prepared from hardwood and softwood biomass waste (e.g. sludge, bark, and sawdust) are exfoliated in a range of solvents to allow the identification of benign alternatives that could afford highly concentrated dispersions. The majority of biochar nanostructures produced after exfoliation are stacked nanosheets containing between 2-8 layers (average 15 nm thickness). Correlations between effective LPE of biochar in solvents and different solvent parameters, including Kamlet-Taft, were established and allowed greener solvents to be used. Surface modification of biochars (e.g. via oxidation) has potential to increase their dispersibility in more benign solvents. LPE of oxidized biochars is more efficient in hydrogen-bond accepting solvents due to the increased concentration of carboxylic acid and alcohol functional groups on the surface of particles, when compared to non- functionalized biochars. Dispersions containing 0.20-0.75 mg/mL exfoliated oxidized biochar were obtained in solvents such as polyethylene glycols, glycerol formal and e-caprolactone. Moreover, LPE of pristine biochars in dimethyl carbonate, ethyl acetate, and solketal gave similar yields to more commonly used solvent for this process, N-methyl-2-pyrrolidone (NMP) a known reprotoxic molecule. </p> </div> </div> </div><br></div>