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The exponentially increasing use of hazardous traditional organic solvents and catalysts for more accessible synthesis of important heterocycles useful for humankind in various fields, such as medicine, materials science, and agrochemicals, is having devastating impacts on the environment, are directly or indirectly affecting the structure and productivity of ecosystems. This has shifted the focus of the scientific community towards using eco-friendly and greener solvents, catalysts, materials, and methods for sustainable growth. As a result, there is a drive to change traditional techniques to environmentally sustainable processes by following the principle's of green chemistry. In this connection, the use of hazardous organic solvents and catalysts for synthesizing 1,2,3-triazoles is a global concern. Thus, newer methodologies were designed using eco-friendly catalysts and benign solvents such as ionic liquids (ILs) or water. The use of ILs in organic synthesis as a solvent and catalyst has attracted tremendous attention in recent years owing to their superior physiochemical properties, such as low vapor pressure, non-volatility, non-flammability, excellent conductivity, and electrochemical and thermal stability, thereby, increasing the reactivity, selectivity, catalyst recyclability, and other properties. In this review, authors have critically screened, divided, and summarized research articles into two significant sections: firstly, the synthesis of 1,2,3-triazoles from alkynes using ILs and secondly, the synthesis of 1,2,3-triazoles from substrate molecules other than alkynes using ILs. It is hoped that this review will stimulate scientists to adopt environmentally sustainable ILs as green solvents and catalysts for the synthesis of 1,2,3-triazole-based compounds. [ABSTRACT FROM AUTHOR]

Some of the latest technological developments involving chemistry in water are discussed. Although each advance bears little-to-no relationship to the others, in the composite they highlight the seemingly unlimited opportunities for discovering nature's secrets using water as the reaction medium. Thus, in addition to the environmental aspects driving this research, the benefits to be realized in making this switch away from reactions run in organic solvents and into an aqueous medium are clearly indicative of the future of synthetic organic chemistry. [ABSTRACT FROM AUTHOR]

N,N-Dimethylformamide (DMF) and N-methylpyrrolidinone (NMP) are two of the common organic solvents which are facing increasing restrictions in terms of chemical safety and environmental regulations. Thus, seeking greener alternatives to replace them becomes an urgent need. Cyrene™ has recently evolved as one of the greener alternatives in many applications. However, its high viscosity greatly limits its broader applications. In this study, a series of Cyrene™ blends, a solvent system created by blending Cyrene™ with other common organic solvents, were developed and studied to address the Cyrene™'s viscosity issue. The material stability and applications in organic syntheses, i.e. HATU amide coupling, Suzuki coupling, Sonogashira coupling, N-alkylation, SNAr reaction, aldimine reaction and 2-pyridyl homocoupling, are also investigated to demonstrate the usefulness of these Cyrene™ blends. [ABSTRACT FROM AUTHOR]

Dihydrolevoclucosenone (Cyrene is its market name) is a biomass-derived solvent that can be produced in only two steps from biomass, while being biodegradable, non-mutagenic and non-toxic. Its "green" profile combined with its physical properties makes Cyrene a plausible substitute for a number of widely used toxic organic solvents. The first attempt to assess Cyrene as a solvent dates back to 2014 and since then, numerous research groups have opted for this promising alternative. Cyrene has successfully been employed as a solvent in materials chemistry, peptide chemistry, organic synthesis and many more research fields, which are going to be discussed in the context of this review. [ABSTRACT FROM AUTHOR]

Transition metal mediated C–H functionalization has been highly relevant in organic synthesis for decades. However, sustainability as an inherent feature in such transformations remains under-developed. Through a varied approach, we have explored metal-centered catalysis practiced via mechanochemistry and under microwave-irradiation, both strictly without the use of any toxic organic solvents. In some sections of this report, we shed light upon C–H functionalizations carried out in the universal and clean solvent water, as well as in neat, solvent-devoid conditions. Different metal centers like Pd, Rh, Ru, Cu, Fe, Co and a spectrum of mechanistic pathways that have accomplished these reactions in an unconventional but green protocol, are discussed extensively. This serves as an attempt to address the challenges in environmental preservation while carrying out organic reactions, and to encourage innovative versatile ideas. Our review collectively presents the endeavours that have introduced hazard-free methodologies in these C–H activation pathways. [ABSTRACT FROM AUTHOR]

Selenium-catalysed oxidations are highly sought after in organic synthesis and biology. Herein, we report our studies on the on water selenium mediated oxidation of anilines. In the presence of diphenyl diselenide or benzeneseleninic acid, anilines react with hydrogen peroxide, providing direct and selective access to nitroarenes. On the other hand, the use of selenium dioxide or sodium selenite leads to azoxyarenes. Careful mechanistic analysis and 77Se NMR studies revealed that only Se(IV) species, such as benzeneperoxyseleninic acid, are the active oxidants involved in the catalytic cycle operating in water and leading to nitroarenes. While other selenium-catalysed oxidations occurring in organic solvents have been recently demonstrated to proceed through Se(VI) key intermediates, the on water oxidation of anilines to nitroarenes does not. These findings shed new light on the multifaceted nature of organoselenium-catalysed transformations and open new directions to exploit selenium-based catalysis. [ABSTRACT FROM AUTHOR]

The production of fluorescent polymer dots (PDs) from biomass compounds usually requires additional toxic reagents or external energy input, due to which the facile and green fabrication strategies are still highly desirable. Herein, we report the general and modular preparation of natural polyphenol-based fluorescent PDs via a one-pot co-polymerization reaction under a mild condition. The use of natural polyphenols as the starting materials has completely prevented the use of organic solvents and harsh chemicals, whereas the high reactivity of natural polyphenols allowed the facile and modular fabrication of fluorescent PDs without any external energy input and sophisticated organic synthesis. The luminescence properties of the resulting PDs were dependent on the structure of natural polyphenols, and it was found that PDs possessed good photostability and biocompatibility. In addition, PDs showed high selectivity towards copper ions among cations, anions, and biomolecules, which were further employed to detect copper ions in living cells and environmental water samples. Thus, this strategy offers a green and facile route for the design and preparation of natural molecule-based PDs for biomedical and environmental applications. [ABSTRACT FROM AUTHOR]

Reducing or eliminating organic solvent use in pharmaceutical manufacturing is perhaps the most effective way to reduce the environmental, health, and safety impacts of drug substance manufacturing. With this in mind, we have developed a process to manufacture an investigational 5-HT4 receptor agonist that is conducted almost entirely in water, including multiple controlled isolations. Key transformations carried out in aqueous media include a benzimidazole cyclization, amide bond formation, reductive amination, and a selective oxidation of an aliphatic alcohol. Compared to the first-generation manufacturing process using organic solvents, the aqueous process described here uses 77% less material inputs, 94% less organic solvent, and, surprisingly, 48% less water, while improving overall yield from 35% to 56%. [ABSTRACT FROM AUTHOR]

Here we report for the first-time various organic transformations such as aldol condensation, oxidation, nucleophilic substitutions, protection, acylations and coupling reactions using a mechanochemical approach at a controlled temperature using a single synthesis platform. Almost minimal solvents or solvent-free conditions are used, making it a very efficient and clean synthesis of various products. A jacketed screw reactor when operated at different temperatures (0 °C to 160 °C) and over a range of rotation speeds for changing the residence time (15 s–300 s) helped to achieve maximum conversion. This approach is also extended to the synthesis using substrates having different substitutions, heterocycles and steric hindrance. [ABSTRACT FROM AUTHOR]

Glycolaldehyde is a biomass-derived chemical compound available from cellulose or glucose. Until now, little attention has been devoted to its use towards value-added chemicals. To explore novel transformations of glycolaldehyde, in this work, a three-component reaction of glycolaldehyde, indole and a 1,3-dicarbonyl compound was developed to synthesize a class of 3-(indol-3-yl)-2,3-dihydrofurans. Using glycolaldehyde diethyl acetal as a glycolaldehyde source, the reaction can be performed in organic solvents, and two catalytic systems were proved to be effective: (a) Sc(OTf)3/nitromethane and (b) Ni(ClO4)2·6H2O/acetonitrile. However, these conditions applied to the direct use of the bio-based glycolaldehyde aqueous solution did not provide the dihydrofurans efficiently. To enable the use of an aqueous solution of glycolaldehyde, a hitherto unreported deep eutectic solvent (DES) was developed by using FeCl3·6H2O and meglumine (N-methylglucamine) as precursors. The FeCl3·6H2O/meglumine DES was characterized by FTIR, TGA and DSC, and the obtained results demonstrated unambiguously the formation of a DES. This DES was found to be an efficient and water-compatible promoting medium for the abovementioned three-component reaction. A variety of 3-(indol-3-yl)-2,3-dihydrofurans were synthesized in good yields. The FeCl3·6H2O/meglumine DES system can also be recycled without significant loss of activity. [ABSTRACT FROM AUTHOR]

Correction for 'Continuous flow solvent free organic synthesis involving solids (reactants/products) using a screw reactor' by Brijesh M. Sharma et al., Green Chem., 2019, 21, 5639–5646, https://doi.org/10.1039/C9GC02447F. [ABSTRACT FROM AUTHOR]

Traditional organic chemistry, and organic synthesis in particular, relies heavily on organic solvents, as most reactions involve organic substrates and catalysts that tend to be water-insoluble. Unfortunately, organic solvents make up most of the organic waste created by the chemical enterprise, whether from academic, industrial, or governmental labs. One alternative to organic solvents follows the lead of Nature: water. To circumvent the solubility issues, newly engineered "designer" surfactants offer an opportunity to efficiently enable many of the commonly used transition metal-catalyzed and related reactions in organic synthesis to be run in water, and usually at ambient temperatures. This review focuses on recent progress in this area, where such amphiphiles spontaneously self-aggregate in water. The resulting micellar arrays serve as nanoreactors, obviating organic solvents as the reaction medium, while maximizing environmental benefits. [ABSTRACT FROM AUTHOR]

As regulations that restrict the use of organic solvents become more stringent, ball milling remains an attractive substitute for traditional organic synthesis. However, the mechanochemistry community does not have a purification pathway to complement the solvent-free, ball milling process. Functional resins have proven to be powerful synthetic tools that simplify purification, but traditional handling of these resins restricts their utility, as hazardous organic solvents are needed to swell the resin. Ball milling the functional resin exposes the functional groups as a function of surface area. This report details the use of ball milling and functional resins to perform an environmentally attractive version of the Wittig reaction. [ABSTRACT FROM AUTHOR]

The capture of carbon dioxide by ammonia in both aqueous and non-aqueous solutions was investigated at atmospheric pressure and 273 K under different operating conditions. The CO2capture is fast and efficient ranging between 78 and 99%, depending on both the NH3concentration and the solvent nature. The precipitation of solid mixtures of ammonium bicarbonate, ammonium carbonate and ammonium carbamate occurred in ethanol–water solution. Selective precipitation of ammonium carbamate was achieved by reacting gaseous CO2and NH3in anhydrous ethanol, 1-propanol or N,N-dimethylformamide (DMF) in a flow reactor that operates in continuous. In the second step of the process, the pure ammonium carbamate is used to produce urea with good yield (up to 54% on carbamate basis) at 393–413 K in the presence of inexpensive Cu(ii) and Zn(ii) catalysts. The yield of urea depends on several factors including the catalyst, the reaction temperature and the reaction time. Identification and quantification of urea in the reaction mixtures was obtained by analysis of its 13C NMR spectrum. A preliminary mechanistic interpretation of the catalytic reaction is also briefly presented and commented. [ABSTRACT FROM AUTHOR]

Tandem reactions of isothiocyanates (1) with 2-aminothiophenols (2), or isothiocyanates (1) with 2-aminophenols (4), were carried out rapidly and efficiently in water. A significant rate acceleration of the reaction between 1aand 2ain water compared with commonly used volatile organic solvents was observed. Through these reactions, a variety of structurally and pharmaceutically interesting 2-aminobenzothiazoles (3) and 2-aminobenzoxazoles (5) were synthesized in good yields. This novel synthetic approach toward 3and 5has advantages such as high efficiency, readily available starting materials, environmentally benign solvent, and highly simple and practical experimental procedures. [ABSTRACT FROM AUTHOR]

Selective oxidation is of immense importance in the synthesis of chemical intermediates and the epoxidation of alkenes by the electrophilic addition of oxygen to a carbon–carbon double bond remains one of the most significant challenges in oxidation catalysis. Although molecular oxygen is the most environmentally benign oxidant in many cases, far more reactive forms of oxygen are required to achieve reaction, and this can lead to by-products with a heavy environmental burden with respect to their disposal. We show that gold supported on graphite is a very effective catalyst for the epoxidation of cis-cyclooctene as long as catalytic amounts of a hydroperoxy species are present at the start of the reaction. Using mild solvent-free conditions the hydroperoxy initiator persists in solution for only a few minutes, being initially adsorbed on the catalyst surface. Subsequently, it decomposes to establish a reactive species that can propagate the selective oxidation process we observe. The observation of an induction period may in part be due to the adsorption of the radical initiator blocking surface sites as well as the establishment of the reactive species. We confirm that graphite is the best support and that tert-butyl hydroperoxide is the preferred initiator. We report extensive studies concerning the reusability of the gold/graphite catalyst as catalyst reusability is a key feature of green chemistry. The catalyst is found to be inhibited by the epoxide product but we demonstrate the effect of this is negligible for reused catalysts over a long reaction time. [ABSTRACT FROM AUTHOR]

A new simple, rapid and high yielding synthesis of various 5-substituted thiazoles by Suzuki–Miyaura cross-coupling reaction is described using microwave irradiation in aqueous medium without organic co-solvent in the presence of tetrabutylammonium bromide. [ABSTRACT FROM AUTHOR]

A simple and efficient procedure for the synthesis of 2-substituted benzimidazoles has been developed by a one-pot reaction of o-phenylenediamine with aromatic aldehydes in the presence of an ionic liquid, 1-methyl-3-pentylimidazolium tetrafluoroborate, [pmim]BF4at room temperature in open air without any organic solvent. The ionic liquid is recycled. A remarkable influence of the substituent on the imidazolium unit of the ionic liquid on the outcome of the reaction is observed. [ABSTRACT FROM AUTHOR]

Chemo-enzymatic oxidation of various N-alkylimines mediated by lipases produced the corresponding E- or a mixture of E- and Z-N-oxaziridines with moderate to very high yields (>99%) and good to excellent selectivities (70–100%) within 30 min to 6 h in various organic solvents at room temperature (25 °C) with urea-hydrogen peroxide (UHP) or aqueous hydrogen peroxide (AHP). The E/Zisomer ratio was critically dependent on the stereo-electronic nature of the substituents in the N-alkylimines. The influence of organic solvents, acyl donor and lipase mass was evaluated in these reactions. [ABSTRACT FROM AUTHOR]

A new method for lactone synthesis with bis(trimethylsilyl) peroxide as the oxidant and ionic liquids as solvents is reported. We propose two possibilities for the Baeyer–Villiger reaction course. The first of these is based on simply exchanging dichloromethane, the classical solvent for Baeyer–Villiger oxidation, for the ionic liquid bmimNTf2, which results in increased product yields. The second possibility is the elimination of the Baeyer–Villiger reaction catalyst and use of 1-butyl-3-methylimidazolium trifluoromethanesulfonate as both the solvent and catalyst. This method gives lactones in high yields with the possibility of ionic liquid recycling. [ABSTRACT FROM AUTHOR]

Ethyl L-lactate can be tuned with a cosolvent to create polarity conditions ideal for synthesizing aryl aldimines that crystallize directly out of solution within minutes under ambient conditions in excellent yields and requiring no further purification. [ABSTRACT FROM AUTHOR]