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To overcome the challenges associated with the toxicity of the majority of organic solvents for the liquid phase synthesis of solid electrolytes toward the human body and environment, we demonstrate the synthesis of tin-based sulphide electrolytes using water, which is the most environmentally friendly solvent. ortho-Thiostannate, i.e., Li4SnS4, was obtained from a mixture of Li2S, Sn, and S using aqueous solution synthesis. Furthermore, Li10SnP2S12, a superionic conductor, was obtained by mixing an aqueous solution of Li4SnS4 and tetrahydrofuran suspension of Li3PS4, which exhibited the highest ionic conductivity (5.9 × 10−3 S cm−1 at 25 °C) in liquid-phase synthesis. This study successfully demonstrates that water can be efficiently used to synthesize sulphide electrolytes instead of conventional organic solvents. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) are gaining rapid prominence in numerous biocatalysis processes due to their green characteristics, biodegradability, low cost, and simple preparation compared to harsh organic solvents and toxic ionic liquids. However, natural enzymes tend to show activity reduction, even inactivation in the presence of many DESs. Here, we present the first rational design approach to achieve enzymes resistant to both DESs and high temperatures. Using the interaction pattern between DESs and BSLA (Bacillus subtilis lipase A, our model enzyme) derived from all-atom molecular dynamics (MD) simulations, we formulated a solvation-guided engineering strategy. This was established after assessing 33 structural, solvation, and energy observables. We rationally designed and experimentally tested 36 single substitutions, of which 28 (a 77.78% success rate) exhibited improvements in at least two DES cosolvents: choline chloride (ChCl) : acetamide, tetrabutylphosphonium bromide (TBPB) : ethylene glycol (EG), and ChCl : EG. Additionally, through stepwise recombination, we identified two robust BSLA variants, D64H/R107L/E171Y and D64H/R142L, showing stability improvements of up to 4.4-fold and 3.2-fold in three DESs and at 50 °C, respectively. Further MD studies demonstrated that (i) the restricted overall structure but fine-tuned local flexibility and (ii) increased water but decreased DES molecules at substituted sites are two main factors contributing to the enhanced multiple DES resistance. Overall, solvation-guided engineering offers an efficient and rational approach for designing lipases tolerant to DES cosolvents and elevated temperatures, with a considerable potential for adaptation to other enzymes. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) has enormous potential for transforming the way organic solvents are purified and recovered in the chemical industry. Apart from conventional thin film composite (TFC) nanofiltration membrane fabrication methods, a greener, simpler, and more efficient approach has been utilized to fabricate OSN membranes. Oxidative polymerization of an aqueous solution of a pyrrole monomer on a hydrolyzed/crosslinked polyacrylonitrile (H-PAN/C-PAN) support yielded a dense polypyrrole (PPy) skin layer consisting of a conjugated carbonaceous polyaryl network. The presence of multiple amino groups (>NH) in the PPy chain develops extensive hydrogen bonding with the –COOH and –NH groups present in the H-PAN/C-PAN support. The shift in the ATR-FTIR peaks of PPy upon deposition on the H-PAN/C-PAN support confirmed the interaction between PPy and the H-PAN/C-PAN support. When the OSN performance of the fabricated membranes was studied, the PPy@C-PAN/PETP membrane showed a better performance in terms of rejection of model solutes including charged and neutral molecules compared to the PPy@H-PAN/PETP membrane. Both membranes rejected >99% of Rose Bengal, Congo red, and Eriochrome black T used as model solutes in the current study. For the neutral molecules, PPy@H-PAN@PETP was able to reject 44% of triphenylbenzene (TPB) and >99% of hexaphenylbenzene (HPB), whereas PPy@C-PAN@PETP rejected 72% of TPB and >99% of HPB. In the case of methylene blue, a rejection of 48% was found for PPy@H-PAN/PETP while a rejection of 82% was recorded for PPy@C-PAN/PETP. Moreover, the permeance of n-hexane was found to be 9.3 L m−2 h−1 bar−1 for PPy@H-PAN/PETP and 3.3 L m−2 h−1 bar−1 for the PPy@C-PAN/PETP membrane. [ABSTRACT FROM AUTHOR]

Extraction of compounds with different physicochemical properties from a complex matrix usually involves several individual steps and requires large volumes of organic solvents. In this pioneering study, we propose a comprehensive two-step supercritical fluid extraction using carbon dioxide, ethanol, and water. This novel approach allows the extraction of non-polar and polar analytes within one run in two consecutive steps. Indeed, the first step with a dominant amount of CO2 with only 2% cosolvent allowed the selective extraction of non-polar volatile terpenes only in 20 min. The conditions were then automatically switched. Increasing the cosolvent volume in the extraction solvent up to 44% (v/v) resulted in the extraction of more polar compounds, including flavonoids and phenolic acids, in 60 min. Importantly, switching the supercritical fluid extraction (SFE) conditions does not require any manual intervention but results in two separate fractions containing target compounds with distinctly different physicochemical properties. The novel method was verified in terms of repeatability, accuracy, precision, and greenness. Two-step SFE was applied to seven plant species differing in volatile terpenes and phenolic profiles. The results proved that this concept is suitable for the analysis of complex plant samples. In addition, it enables a reduction in the toxic solvents consumption, extraction time, and manual intervention required for traditional extraction approaches when isolating different groups of metabolites. [ABSTRACT FROM AUTHOR]

This study presents a novel environmentally friendly approach for synthesizing a water-compatible superhydrophilic molecularly imprinted resin on graphene oxide (SMIR/PGO). In the design of SMIR/PGO, dopamine (DA) serves a dual role: (1) self-polymerizing on the GO surface to form polydopamine, which acts as an environmentally friendly bridge for covalently grafting SMIR and (2) acting as green hydrophilic monomers, replacing traditional phenolic monomers to obtain SMIR. The dual role of DA eliminates the need for tedious steps such as separation, washing, and drying of intermediate materials, facilitating a simple one-pot synthesis. Additionally, hexamethylenetetramine (HMTA) replaces the traditional crosslinker formaldehyde, thereby avoiding direct contact with the carcinogenic formaldehyde. The NH3 produced by HMTA decomposition acts as a catalyst, obviating the need for additional catalysts in the synthesis of SMIR/PGO. This one-pot synthesis occurs in an aqueous matrix and entirely avoids the use of organic solvents, aligning with green chemistry principles and ensuring compatibility with aqueous solutions. Consequently, SMIR/PGO combines the high specific surface area of GO, the multifunctionality of polydopamine, and the excellent water compatibility and high selectivity of SMIR. This combination provides multiple adsorption interactions to achieve selective extraction of chlorogenic acid in the aqueous matrix. This environmentally friendly synthetic strategy offers an efficient means of designing superhydrophilic molecularly imprinted materials with exceptional recognition and adsorption capabilities in aqueous environments. [ABSTRACT FROM AUTHOR]

Thin-film selective layers fabricated via interfacial polymerization (IP) form the core of membrane-based water purification and desalination, as well as other molecular separations. The monomers and organic solvents used in the reaction are for the most part toxic chemicals, likely to be banned in the near future, for environmental protection. There is, therefore, a growing need to find alternative, sustainable, materials that can produce adequate membranes for industrial applications, fabricated via IP. The present work summarizes recent studies on fabricating RO/NF/OSN membranes via IP using sustainable solvents and/ or monomers, in comparison to the toxic chemicals used to fabricate polyamide, the chosen polymeric material for the commercial selective membrane layer. The properties of these ‘green’ materials are described, as well as the properties of the resultant membranes, discussing possible limitations in the fabrication techniques and the benefits of the process. Furthermore, an eco-scale score is calculated for representative membranes, demonstrating the utility of this tool for assessing the ‘greenness’ of the fabricated membranes. Overall, the presented literature shows that there is a great potential for fabricating more sustainable and scalable membranes. However, studies exhibit various limitations, for example, no standardization for performance tests and performance criteria for every membrane type, which prevents accurate and true comparisons among different membranes. Suggestions are made, where applicable, for future work to add aspects that assess the potential of fabricated membranes to future industrial applications. Finally, and most importantly, there is still a need for improved fundamental understanding of IP, with which to facilitate the search of alternative sustainable materials for membrane fabrication with desired properties. [ABSTRACT FROM AUTHOR]

MOF-74 or M2(dhtp) (M = metal ions, dhtp = 2,5-dihydroxyterephthalic acid), as a typical class of metal–organic frameworks (MOF), have garnered considerable interest due to their abundant unsaturated metal sites. However, environmental and economic limitations caused by the extensive use of organic solvents in traditional syntheses hinder their industrial applications. Although water as a green solvent is considered to be the best candidate solvent, water-based MOFs often have poor crystallinity and long synthesis time, and controlling the particle size is difficult. Herein, a water-based strategy is proposed to synthesize high-quality MOF-74–Co with controllable particle sizes in a rotating packed bed (RPB) reactor using high-gravity technology. MOF-74–Co could be rapidly prepared in the RPB, and shows a smaller and more uniform particle size, higher crystallinity, and larger specific surface area, as compared to the counterpart prepared in a traditional stirred tank reactor. Further adopting acetic acid as a modulator, the as-prepared MOF-74–Co has the highest BET surface area (1599 m2 g−1) in the reported literature so far and simultaneously possesses a high space–time yield (293 kg m−3 day−1). High-quality MOF-74–Zn and MOF-74–Ni can also be prepared, proving the generality of this strategy. Furthermore, the small-sized MOF-74–Co-78 nm exhibits a faster adsorption rate and a larger saturation adsorption capacity (298 mg g−1) for CO2 compared with large-sized samples. This study not only advances the field of green synthesis of MOFs but also paves the way for efficient manufacturing processes in MOF-74 synthesis for CO2 adsorption. [ABSTRACT FROM AUTHOR]

The selective oxidation of alcohols has drawn significant attention in heterogeneous catalysis with the increasing use of Pickering interfacial catalysis (PIC) for green transformations of alcohols. However, it is still highly desirable to design and develop a solid catalyst with easy separation and recycling, made from abundant resources through a simple synthesis route, for the selective oxidation of alcohols. In this study, ferrite nanoparticles, synthesized via a hydrothermal process, were employed to act as a stabilizer and catalyst in PIC for the oxidation of benzyl alcohol using H2O2. The ferrite nanoparticles exhibited higher catalytic performance in PIC than in acetonitrile. The turnover number (TON) of the nanocatalyst in PIC was found to be 1.5–4 times higher than that in acetonitrile, and the reaction constant in PIC (kPIC = 0.712 h−1) was almost twice that in acetonitrile (kCH3CN = 0.310 h−1) for MnFe2O4 nanoparticles. Moreover, other alcohols could also be oxidized with moderately high conversion and selectivity in PIC. Significantly, the ferrite nanocatalyst could be easily separated from PIC using a magnet for reuse, achieving 88% BzOH conversion after five cycles. The use of hazardous organic solvents was avoided in PIC, making it a more advanced, green and sustainable reaction system. [ABSTRACT FROM AUTHOR]

The interpretability and accuracy of deep-learning-based predictive models play a pivotal role in accelerating computer-aided green product design considering environmental, health, and safety (EH&S) impacts. Recently, molecular graph-based hybrid representation methods have demonstrated comparable or superior abilities to other molecular representations. However, existing molecular graph-based hybrid representation methods incorporate only 2D-based atom-level, bond-level, or molecule-level features while neglecting the molecular geometry, also known as 3D spatial structure information, which is crucial for determining molecular properties. Moreover, existing molecular graph-based hybrid representations lack consideration of knowledge in the chemistry domain, which can improve the interpretability of the predictive models. To this end, a 3D multi-hierarchical representation-based deep neural network (3D-MrDNN) architecture, simultaneously integrating directed message passing neural network learned representation, chemically synthesizable fragment features, and molecular 3D spatial information, is established for the prediction of EH&S properties. The results of predictive performance and ablation studies indicate that the proposed model exhibits decent predictive ability for EH&S properties. Chemically synthesizable fragments are utilized to integrate chemical knowledge into the proposed 3D-MrDNN architecture, the interpretability of which enables chemists to find the key molecular fragments for designing target products with better EH&S performance. [ABSTRACT FROM AUTHOR]

Aldoxime dehydratases (Oxds) have received considerable attention recently due to their application in the asymmetric synthesis of nitriles without cyanide by catalyzing the dehydration of aldoxime. However, the low stability of Oxds remains a huge obstacle to achieving high conversions and productivities of hydrophobic substrates. OxdPsp was immobilized on a macroporous adsorption resin (IOP) via an ATPS coupled with in situ immobilization. IOP-catalyzed dehydration of 2-phenylpropanal oxime (1) to prepare (S)-2-phenylpropanenitrile ((S)-2) was successfully performed with 95.7% yield, 94.1% ee and 98.6% conversion. The enriched (S)-nitrile (ee 94.1%) was obtained by using (E)-enriched aldoximes (E/Z = 97/3) as the substrate, which is consistent with the Gröger enantiopreference rule. A kinetic model to predict the dehydration catalyzed by IOP was established with an average deviation of 7.6%. The IOP-catalyzed dehydration reaction follows a sequential mechanism including substrate and product inhibition. Developing a kinetic model is a key step in the application of artificial intelligence in chemical engineering. After three recycling steps of IOP, the yield of (S)-2 still reached 83.6%, indicating that the stability of IOP was greatly enhanced, which was attributed to employing an organic solvent with a higher lg P value as the working medium and the immobilization protocol. [ABSTRACT FROM AUTHOR]

With allyl compounds being a valuable chemical commodity, it is important to understand the sustainability aspects of the Tsuji-Trost reaction in terms of productivity (reactivity-coupled utility), environmental impact (including health hazards), and economic burden and benefits of commercially available allylic precursors under varying conditions. However, comprehensive literature searches reveal that no such study is publicly accessible; the majority of the literature focuses only on the synthetic utility of a few allylic precursors. In this context, we undertook a study for sustainability assessment of 26 allyl precursors (with diverse ionisable partners) by simulating an allylic amination reaction in an alternative reaction medium, water (vs. an organic solvent, OS), under Earth-abundant nickel (vs. traditional palladium) catalysis. The study was accomplished through: (1) conducting reactivity-utility profiling of allylic precursors; (2) identifying the major side reactions occurring with allylic precursors (water vs. OS); and (3) determining green metrics (E-factor, atom economy, atom efficiency, RME, and EcoScale) of the amination process linked with allylic precursors. The key highlights of the study include the following: (a) water is as diverse as an organic solvent in facilitating the Tsuji-Trost allylic amination; (b) diverse allylic precursors could be employed in water as well as in an organic solvent to realize allylic amination; (c) nickel catalysis is a viable alternative to palladium for allylic amination with distinct superiority in the water medium while using an allyl alcohol and allyl amine (trans-N-allylation). Further advancing sustainability and catalysis, we demonstrated for the first time a fully catalytic 'in-water' allylic amination reaction using an allylic alcohol and a Ni(II)-catalyst with features like scale-up synthesis (up to 10 g), catalytic usage of a reductant, etc. The authors propose this work as a sustainability guide to steer further research and developments in academia and industry related to allylation chemistries. [ABSTRACT FROM AUTHOR]

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]

An effective approach to separate chiral (2S,4S)-1-(tert-butoxy carbonyl)-4-(methoxymethyl) pyrrolidine-2-carboxylic acid ((2S,4S)-TBMP)) from mixed (2S,4S)-TBMP and (2S,4R)-1-(tert-butoxy carbonyl)-4-(methoxymethyl) pyrrolidine-2-carboxylic acid ((2S,4R)-TBMP), an important intermediate for the anti-HCV drug Velpatasvir, was developed for the first time, eliminating the need for salinization and dissociation processes and several organic solvents with water. Conceivable binding modes were set up by Gaussian calculation, and the separation process was designed and studied based on the calculation. The results showed that only the monohydrate of (2S,4S)-TBMP could be crystallized since three hydrogen bonds were formed between (2S,4S)-TBMP and water, which resulted in more stability and isomer separation. Compared to the original approach, our new approach exhibits a remarkable 17.4% increase in yield, a 43.3% rise in atom economy (AE), a 43.3% improvement in reaction mass efficiency (RME), and a substantial 32.0 g g−1 reduction in process mass intensity (PMI). An industrial-scale implementation was set up successfully according to the new approach, achieving a batch capacity of 100 kg. [ABSTRACT FROM AUTHOR]

5-Hydroxymethylfurfural (5-HMF) is the key to unlocking the potential of biomass materials to transform into fuels, materials, and chemicals. In this study, an effective biphasic reaction system composed of a reaction phase (aqueous phase) and an extraction phase (organic phase) was used for the conversion of fructose to 5-HMF. Deep eutectic solvents (DESs) composed of different hydrogen bond donors and hydrogen bond acceptors, the ionic liquid [BMIM]Cl, aqueous choline chloride, aqueous betaine hydrochloride, and ethylamine hydrochloride were used as the reaction phase, and different organic solvents, such as methyl isobutyl ketone (MIBK), dimethyl sulfoxide (DMSO), toluene, ethyl butyrate, and gamma-valerolactone (GVL), were used as the organic phase. Experiments were conducted under optimal conditions simulated using the reaction surface method to obtain the maximum 5-HMF yield. The highest yields of 5-HMF obtained in reactions with DESs were 67.86%, 68.69%, and 71.40% for ChCl : OA, ChCl : Lac, and EaCl : Lac, respectively. However, adding dimethyl sulfoxide and betaine hydrochloride aqueous solution to the fructose conversion system resulted in a maximum yield of 90.42% ± 1.46% of 5-HMF without the use of catalysts. This study also demonstrated that betaine hydrochloride could be effectively reused four times. A 5-HMF yield of at least 80% indicates a green process suited towards sustainable development. [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]

This tutorial review aims to describe the status of the scaling up of organosolv treatment. It is a process where various lignocellulosic materials are fractionated, selective depolymerization mechanisms are catalyzed, and their main components (polysaccharides, lignin and extractives) can be extracted, separated and isolated using liquid organic solvents such as alcohols, ketones and proton-donating acid molecules. Organosolv fractionation can be applied to several renewable biomasses, allows the production of pure species systems to prepare valuable chemicals, polymers and biomaterial compositions with a related environmental impact, lower than that of classical industrial plants, and optimizes the resource carbon efficiency. However, the high energy consumption for the recovery after dissolution, input costs and feedstock flexibility robustness are slowing down the piloting of commercial operations. As a critical indicator evaluation, a summary of reasons why engineering organosolv is still extremely interesting, together with an overview of the most important organosolv technologies, describing current equipment scale range economics, limitations and market research opportunities, is presented in detail. A variety of sources (wood, straw, bagasse, wastes...), media (water, methanol, ethanol, formates, acetates...) and products (biogas, bioethanol, (nano)cellulose, glucose, furans...) are comparatively benchmarked. Existing (model) validated, demonstrational or patented configurations are collected, listing strengths as well as challenges. [ABSTRACT FROM AUTHOR]

Organophosphorus compounds containing hydrolytically and metabolically stable C(sp3)– and C(sp2)–P bonds are widely used as reagents, ligands, pesticides, herbicides, flame retardants, surface modifiers, and antiviral and anticancer drugs. These applications rely on efficient C(sp3)– and C(sp2)–P bond-forming reactions. However, currently available C(sp2)–P cross-coupling protocols require high catalyst loadings and temperatures, as well as environmentally unsustainable and harmful organic solvents (e.g., N,N-dimethylformamide, DMF). Herein, we disclose a conceptually novel strategy for performing multimetallic Pd/Ni- and dual-ligand Pd-catalyzed C(sp2)–P cross-coupling reactions in aqueous micelles under mild and environmentally friendly conditions. Micellar catalysis in water enables C(sp2)–P cross-coupling while avoiding environmentally unsustainable organic solvents, thereby reducing organic waste generation. Such micellar C(sp2)–P cross-coupling reactions tolerate various functional groups and provide access to structurally diverse (hetero)aryl (thio)phosphonates, phosphinates and phosphine oxides using inexpensive commercial materials and catalysts. Moreover, C(sp2)–P cross-coupling reactions of medically relevant substrates and drugs under late-stage functionalization settings and multistep one-pot processes highlight the potential applications of this experimental paradigm. [ABSTRACT FROM AUTHOR]

Porous hollow spherical particles benefit from special structural features and fascinating physicochemical properties resulting in widespread application. Particularly in pharmaceutical engineering, they have significant advantages for direct compression and drug combination. However, their large-scale application is severely hindered by the limitations of traditional production methods in terms of the use of complex equipment, high energy consumption and high organic solvent usage. In this work, we have developed an oiling-out directional agglomeration method to produce porous hollow indomethacin spherical particles by a simple heating–quenching–drying operation without the use of organic solvents and templating agents. Compared to commercial flake crystals, the indomethacin spherical products have higher average tensile strength (471% increase) and higher plastic deformability, i.e. better tabletability and compressibility. More importantly, nifedipine is successfully loaded into porous hollow indomethacin spherical particles based on molecular polarity differences. The composite particles with a core–shell structure exhibit excellent powder properties, tableting and anti-degradation performance, while also achieving sequential release of drugs. This contribution provides the basis for the development of drug formulation strategies and the design of functional crystalline materials. [ABSTRACT FROM AUTHOR]

The solvent effect has been widely explored in small molecule reactions. However, understanding of the solvent effect on the degradation of thermosetting polymers, especially when it comes to mixed solvents, remains largely elusive. Here the effect of mixed solvents on the oxidative degradation of typical epoxy thermosets is presented. An enhancement effect of the swelling and diffusion was observed in mixed solvents of water and organic solvents, with a higher interaction energy. Besides, the introduction of an organic solvent can enhance the oxidation activities of an oxidant cerium ammonium nitrate aqueous solution. The multiple effects greatly promote the degradation of epoxy thermosets and complete degradation was even achieved at room temperature. This unconventional result reveals the synergistic effects of mixed solvents in polymer degradation and opens a new insight on polymer recycling. It is expected to guide polymers to achieve high value-added recovery and conversion with low energy consumption. [ABSTRACT FROM AUTHOR]

Oligonucleotides are generally manufactured via a solid-phase nucleotide elongation process utilizing a four-step or three-step reaction cycle consisting of detritylation, coupling, sulfurization/oxidation and optional capping. Following each step, the solid support is rinsed with solvent to remove residual reagent and to prepare the growing oligonucleotide chain for the next synthetic manipulation. Reported herein is an investigation of the impact of column-washing operations on the quality of oligonucleotide synthesis in the three-step cycle process. Also described is a more sustainable synthetic protocol without column-washing after the coupling and sulfurization steps that provides material of similar quality compared to material from standard washing protocols. This improvement allows for an approximate 70% reduction in wash solvent use for a typical 18 to 20-mer oligonucleotide. For every kilogram of an oligonucleotide synthesized, >300 L of organic solvents are saved and Process Mass Intensity (PMI) for synthesis steps is decreased from >890 to ∼530. [ABSTRACT FROM AUTHOR]

Supramolecular polymers (SPs) based on macrocyclic host molecules as copolymer monomers are considered a promising class of advanced materials due to their satisfactory tunable properties and host–guest characteristics. Deep eutectic solvents (DESs) have been developed as green solvents to supersede conventional organic solvents and ionic liquids (ILs). By referring to the formation mechanism and macroscopic properties of DESs, the green strategy to develop solvent-free SPs by incorporating the concept of DESs is considered feasible, which enhances the performance of SPs and requires no solvents. Investigating the combination of DESs and macrocyclic host molecules (represented by cyclodextrins, CDs) to develop deep eutectic supramolecular polymers (DESPs) has been a novel subject in recent years. Researchers have prepared DESPs including supramolecular deep eutectic solvents (SUPRADESs) based on CDs/CD derivatives, supramolecular deep eutectic adhesives/gels, and supramolecular composite materials based on inorganic carrier-modified CDs formed with polymeric DESs (PDESs) and have conducted a preliminary exploration of their properties and applications. Based on the urgent need for further research on the combination of CDs as macrocyclic copolymer monomers and DESs, this review aims to summarize relevant definitions, properties, characterization, and applications of CD-based DESPs that have emerged from recent studies. It is hoped that it would promote the cross-development of green chemistry and supramolecular polymers. [ABSTRACT FROM AUTHOR]

Protection of amine groups by amide formation is still among the preferred strategies for multifunctional molecular synthesis despite its waste production, especially the enormous quantities of organic solvents used. In this study, we present a fast, cheap and eco-friendly method for amine group protection involving amide bond formation using choline chloride as a hydrogen bond acceptor and the starting amine as a hydrogen bond donor through the generation of "in situ" amine-based deep eutectic solvents. This novel approach avoids the use of toxic solvents, both during reaction and the work-up phase, thus representing a sustainable alternative to classic amine protection procedures. [ABSTRACT FROM AUTHOR]

Taking advantage of the facile dissolution of chitosan in the green [EMIM][OAc]/GVL-based organic electrolyte solution (OES) and the satisfactory ionic conductivity of the OES, a one-pot strategy for the preparation of a sustainable chitosan/nano-SiO2 nanocomposite organic ionogel electrolyte (CSOIE) was successfully demonstrated through the integration of in situ physical cross-linking via hydrogen bonding using nano-SiO2 and a solution-gel transition induced by moisture after the dissolution of chitosan in the OES. The [EMIM][OAc]/GVL OES not only acted as an efficient solvent for chitosan dissolution, but also ensured high ionic conductivity of the organic ionogel electrolyte and desired electrochemical performance in the assembled flexible supercapacitors over a wide working temperature range. It was found that the storage modulus of the chitosan/nano-SiO2 nanocomposite organic ionogel electrolyte (CSOIE) increased with an increase in the content of nano-SiO2, and the introduction of nano-SiO2 particles into the gel matrix enhanced the mechanical properties and ionic conductivity simultaneously. The as-prepared C8S2OIE sample exhibited high ionic conductivity over a wide temperature range (2.3, 24.3 and 60.3 mS cm−1 at −25, 25 and 80 °C, respectively), and a desirable compressive stress of 1.52 MPa at 25 °C. The assembled flexible supercapacitor using the C8S2OIE sample displayed excellent capacitive performance and temperature-dependent specific capacitance (72.8, 84.6 and 113.2 F g−1 at −25, 25 and 80 °C at 0.1 A g−1, respectively), and long-term stability after 10 000 charge–discharge cycles. It is believed that the satisfactory mechanical properties of the as-prepared CSOIE can be ascribed to both the physically cross-linked chitosan chains via hydrogen bonding and chain entanglement, as well as hydrogen bonding interactions between chitosan chains and nano-SiO2 particles; moreover, the physical interactions were beneficial for the formation of desirable ion channels, thus enabling outstanding electrochemical properties. Consequently, the findings provide significant insights for the design and preparation of sustainable organic ionogel electrolytes using natural polymers, and the outstanding performance of the as-prepared CSOIE suggests significant potential applications in flexible energy storage and conversion devices in the future. [ABSTRACT FROM AUTHOR]

A series of modified polysaccharide polymers were prepared via a solvent-free synthesis involving heterogeneous Schiff base reaction of carboxymethyl chitosan (CMCS) with diverse aldehydes: hexanal, citral, benzaldehyde, 4-methoxybenzaldehyde, 4-chlorobenzaldehyde, and trans-cinnamaldehyde. The prepared CMCS derivatives were extensively studied in terms of their physicochemical, mechanical and morphologic properties. The presented solvent-free method allows multicycle preparation of the desired products. The properties of products prepared by the new method and traditional solvent-based synthesis were compared. The new process meets the essential requirements of green chemistry by diminishing waste products and eliminating organic solvents, while maximizing the use of the involved reagents. Being easily adjusted to suit various substituents, this method offers a potential platform for a formation of new materials and promotes environmentally friendly industrial practices. [ABSTRACT FROM AUTHOR]

The pernicious impact of plastic originating from petroleum-based sources has been an increasing threat to our environment. Amongst several strategies tested and implied to manage these plastic wastes, one promising alternative is switching to biodegradable polymers. Polyhydroxyalkanoates (PHAs) are a class of microbial polyesters that are biodegradable, biocompatible and an attractive alternative for future packaging applications. They offer an approach to carbon neutrality and support a more sustainable industrialization. However, as these microbial polymers are stored intracellularly, development of downstream processes for extraction and purification are essential and are the most cost-intensive steps. A major drawback in most of the existing state-of-the-art is the use of harsh organic solvents which contributes to the non-eco-friendliness of the processes. This work proposes an alternative, sustainable PHA downstream process comprising the use of a green solvent. Biomass with an intracellular PHA content of ca. 49% (gPHA/gVSS) produced by mixed cultures was used in this study. A new hydrophobic natural deep eutectic solvent (hydrophobic NADES), Thymol : Vanillin (8 : 2 molar ratio) was synthesised and used as the extraction solvent while 1-heptanol was used as the purification solvent. Also, different intensities of sonication were applied to assist the cell wall rupture for the efficient release of PHAs. The optimised process yielded ∼99% polymer purity and recovery of ∼42% and did not alter the polymer composition. Furthermore, after successful extraction and purification of PHA, the organic solvents (hydrophobic NADES and 1-heptanol) used can be recycled or reused as per end-user requirements. [ABSTRACT FROM AUTHOR]

The severe formation of humins during the conversion of high-concentration fructose is a crucial bottleneck restricting the large-scale production of 5-hydroxymethylfurfural (HMF) from fructose. Herein, we report an efficient catalytic system for the conversion of high-concentration (10.0–60.0 wt%) fructose into HMF by creating micro-reactors with cetyltrimethylammonium bromide (CTAB) in a mixed solvent of 1,4-dioxane and water (DIO–H2O), wherein the formation of humins is remarkably restrained. The micro-reactors were composed of reversed micelles constructed by the assembly of amphiphilic CTAB in the mixed solvent (VDIO/VH2O = 95/5). The confinement of fructose and bromine anions within the hydrophilic moiety of the micro-reactors enabled facile interactions between fructose and Br− ions, thereby enlarging the promotional effect of Br− ions on fructose-to-HMF dehydration via accelerating the deprotonation of oxocarbenium ion intermediates. Afterwards, the hydrophobic moiety assisted in the transfer of HMF into the organic solvent outside the micro-reactor protected HMF from further rehydration or condensation to humins. The competitive degradation and condensation of oxocarbenium ion intermediates to humins were significantly mitigated, resulting in high HMF yield (70.3%) and TOF (186.0 h−1) after reacting high-concentration (50.0 wt%) fructose at 140 °C within 15 min. This work highlights the utilization of a multifunctional micro-reactor to fix the reaction zone and facilitate mass transfer, thereby providing a valuable guidance for designing effective catalytic systems for future HMF biorefineries. [ABSTRACT FROM AUTHOR]

Catalytic depolymerization of lignin to value-added compounds is receiving increasing interest as part of the circular bioeconomy. This work describes the selective depolymerization of alkali lignin to vanillin at room temperature using metal-based ionic liquids (MBILs) as catalysts in an aqueous medium. Using a reaction mixture of 20 wt% lignin, and 5 wt% [BMIM][FeCl4] catalyst in water, 12.5 wt% of volatile aromatic products were obtained of which 105 mg g−1 of vanillin could be extracted with 85% selectively. For this first, we optimized various solvents (ionic liquids; ILs, deep eutectic solvents; DESs, conventional organic solvents, and water) as reaction media and found water to be the best for lignin depolymerization. Following this, we optimized the effect of time, temperature, and catalyst loading on lignin conversion, product yield, and selectivity. We found that high solubility of alkali lignin in the water results in alkali lignin hydrolysis and subsequent conversion by [BMIM][FeCl4] via heterolytic cleavage of Cα–Cβ bond along with β-O-4 to facilitate higher vanillin production. The purity and structure of extracted vanillin have been confirmed by GC-MS, 1H, and 13C NMR analysis, whereas lignin depolymerization has been confirmed from 1H NMR, 13C NMR, SEM, FT-IR, 2D-HSQC, TGA, and PXRD. [ABSTRACT FROM AUTHOR]

Development of an anhydrous homogeneous method for the cyanoethylation of cellulose is highly desirable. In this study, a series of cyanoethyl cellulose (CEC) composites were homogeneously prepared via the Michael addition of acrylonitrile (AN) to the activated hydroxyl group of cellulose in a novel CO2 switchable solvent. The cellulose was dissolved in this solvent generating a nucleophilic cellulose carbonate intermediate, which is able to react with AN directly via Michael addition and results in CEC with a tunable degree of substitution (DS) by varying reaction conditions, such as temperature, reaction time, and the feeding ratio of acrylonitrile. The obtained CEC samples have DS values ranging from 0.12 to 1.03. The solubility of the CEC samples varies with DS values. This organic and anhydrous CO2 switchable solvent system enables the preparation of CEC with high quality without side reactions induced by water and much easier down-stream treatment, which is superior to other homogeneous counterparts. This study suggests a new platform for the synthesis of novel cellulose derivatives by Michael addition in the CO2 switchable solvent system in the future. [ABSTRACT FROM AUTHOR]

Lignin nanoparticles have emerged during the past decade as well-defined and renewable nanomaterials for fundamental and applied research. However, the presently known methods for the preparation of lignin nanoparticles rely on the use of organic solvents and energy intensive water evaporation processes. Here we present organic solvent-free production of spherical lignin nanoparticles by neutralization of alkaline solution of poorly water-soluble lignins in the presence of sodium lignosulfonate. We show that by combining these two predominant technical lignins it is possible to achieve colloidally stable lignin nanoparticle dispersions at concentrations exceeding 30 wt%. We further demonstrate versatility of the process by using ethanol organosolv lignin, soda lignin, and lignosulfonates from different sources. The lignin nanoparticle dispersions exhibit shear-thinning behaviour and undergo gelation within well-defined pH and concentration regions. Such flowable lignin dispersions mark a breaktrough towards scalable processing of lignin towards sustainable bio-based chemicals and materials. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) have generated great interest as promising green alternatives to replace conventional solvents due to their application-specific tunability, nonflamability, variable viscosity, low vapor pressure, and chemical (and thermal) stability. However, their greenness or sustainability remains unclear and requires rigorous quantification. This work uses life-cycle assessment (LCA) to evaluate the potential environmental impacts incurred from the production of a representative choline chloride (ChCl)/urea DES, reline. The environmental profile of reline is compared with that of common organic solvents (methanol, ethanol, dichloromethane (DCM), and ethyl acetate) on the basis of their utilization as a solvent for the oxidation of alcohol to the ketone; acetophenone. The results indicate that, in general, the DES imparts lower environmental impacts than DCM and ethyl acetate but has higher impacts than methanol and ethanol. Chemical constituent materials (urea, trimethylamine, hydrochloric acid, and ethylene oxide) required for the synthesis of reline DES contribute significantly to its life-cycle environmental impacts when compared to auxiliary processes. In addition to reline, the LCA of four other ChCl-based DESs is performed by substituting urea (hydrogen bond donor in the reline) with ethylene glycol, glycerol, citric acid, or glucose. ChCl/citric acid DES, the so-called natural deep eutectic solvent, imposes the highest environmental impacts among the studied ChCl-based DESs. This is partly due to the high water consumption and carbon dioxide emission during fermentation to synthesize the citric acid. Our study challenges the greennesses of DESs but more research with better data is required to corroborate our findings as some key inputs were modeled from a commercial patent. [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]

Post-synthetic functionalisation of commodity polymers such as polyethylene (PE) is an increasingly important strategy for giving waste plastics new 'lease-of-lives' as functional polymers. In particular, installing oxygenated functional groups such as alcohols and ketones is valuable due to their chemical versatility for further chemical modifications. However, this is especially challenging for PE due to its unreactive nature, and often requires hazardous and environmentally damaging chlorinated solvents owing to PE's excellent solvent resistance. Herein, we demonstrate a highly selective method to install isolated carbonyl groups on PE using only benzaldehyde and O2 as a terminal oxidant, without the need for stoichiometric organic oxidants or any hazardous organic solvents. This process relies on the aerobic auto-oxidation of benzaldehyde to benzoic acid, generating reactive radical intermediates in the process that are responsible for both C–H activation and exclusive carbonyl formation. Our method is compatible with copper(II) oxidation catalysts to enhance the extent of PE oxidation, and can also minimise the waste produced as the benzoic acid side product can be easily isolated and reused for different applications. The versatility of carbonyl-containing PEs for further chemical derivatisation offers many exciting options for transforming waste PE into diverse polymeric materials for a materials circular economy. [ABSTRACT FROM AUTHOR]

Efficient amide formation is of high importance for the chemical and pharmaceutical industry. The direct biocatalytic one-pot transformation of acids into amides without substrate activation is a highly desirable but highly challenging reaction; this is why in general the acid is activated using additional reagents before amide formation occurs. In particular, amidation of α-amino acids is challenging and in general requires protection strategies for the amino functionality. A further challenge is the low solubility of the unprotected amino acids in organic solvents. Furthermore, the amidation process is prone to racemisation as observed for the acyl chloride derivative. These three challenges may be addressed using biocatalysis. Here the enzyme catalyzed, racemization-free amidation of unprotected L-proline with ammonia in an organic solvent is described. Comprehensive reaction, solvent and enzyme engineering allowed obtaining high L-prolinamide concentrations. For instance at 145 mM substrate concentration, 80% conversion was achieved employing an immobilized CalB variant and ammonia in 2-methyl-2-butanol at 70 °C. A twofold increase in L-prolinamide formation was achieved employing the immobilized and engineered enzyme variant CalBopt-24 T245S compared to wild type CalB. In contrast to chemical processes, racemization, halogenated solvents and waste are avoided/minimized and atom efficiency is significantly improved from 45.5% to 86.4%. The excellent optical purity of the obtained product (ee >99%) and the stability of immobilized CalB pave the way for an innovative industrial process to produce L-prolinamide, a key intermediate in drug synthesis. [ABSTRACT FROM AUTHOR]

High-purity glycolic acid (GA) is a necessary building block unit of medical materials which provides a promising value-added utilization of ethylene glycol (EG). Almost all currently applied commercial processes for GA crystallization depend on organic solvent assistance, such as flammable and combustible alcohols, ketones, and alkanes, with great pitfalls of high industrial production cost and safety issues. The green and effective bioconversion technology, based on the resting cell catalysis of EG to GA by Gluconobacter oxydans, grabs the spotlight. However, the efficient separation of purified GA crystals from the fermentation broth in an economical manner is still a big challenge owing to their strong hydrophilicity. In this study, a roundabout strategy was proposed and established to prepare high-purity GA by taking full advantage of the poor hydrophilicity and easy crystallization of calcium glycolate (CG). By processing-module integration, we designed a novel and prospective bio-based technology to integrate resting cell catalysis and the crystallization step, acidification step, and electrodialysis purification step - named RC&CR-AF-ED technology - to achieve continuous and efficient GA bio-preparation. Herein, we first prepared CG crystals, followed by their in situ separation from the fermentation broth, which somewhat relieved the GA end-product inhibition of resting cell catalysis and promoted productivity. Furthermore, the high-purity CG was obtained by the recrystallization operation and acidified to GA solution with sulfuric acid, from which high-purity GA was finally prepared by electrodialysis separation. In contrast to the conventional industrial technology, this roundabout strategy is environmentally friendly for high-grade GA bio-production from EG without any organic solvent processing. [ABSTRACT FROM AUTHOR]

The first 'in-water' nickel-catalyzed chemoselective C3-allylation of (NH)-indoles employing allylic alcohols under mild conditions is reported here. Different indoles and allylic alcohols were found compatible with excellent chemo- (C vs. N: >99%; C2vs. C3: >98%), regio- (linear vs. branch: >99%), and stereo-selectivity (E vs. Z: >99%) and functional group tolerance. The use of water not only provides sustainability by eliminating the need for organic solvent as reaction media but it also activates allylic alcohols via hydrogen bond networking and stabilizes the consequent hydroxide ion (strong solvation effect) resulting in facile oxidative addition, and thereof the formation of electrophilic π-allylNi complexes leading to C3-allyl indoles. The study further highlights the first Hydrogen-bond assisted intermolecular N → C allylic migration via π-allylNi complexation and reports the first synthesis of allyl indoles using allylamine as electrophilic precursors. [ABSTRACT FROM AUTHOR]

Aromatic and heteroaromatic ketones bearing an α-methine proton can be deprotonated and mono-allylated in minutes in the complete absence of an organic solvent to arrive at the corresponding products in high isolated yields. Applications to synthetic targets including both MK-7 and MK-9, as well as coenzyme Q9 (CoQ9), utilizing this new technology are documented. [ABSTRACT FROM AUTHOR]

Compared to the existing literature route to the lapatinib, a greener sequence has been developed as a representative example showcasing the technologies that are available today for applications to targets in the fine chemicals industry. Thus, a 5-step, 3-pot sequence to the targeted antitumor agent is presented that is done mainly in recyclable water, as opposed to the literature process which is done entirely in various organic solvents. Highlighting this work is the use of only 500 ppm of a Pd catalyst, as opposed to the 92 000 ppm (9.2 mol%) utilized previously. [ABSTRACT FROM AUTHOR]

Pregna-1,4,9(11),16(17)-tetraene-3,20-dione (pregnatetraenedione) is the most useful precursor for the synthesis of corticosteroids in industry. However, the production of pregnatetraenedione is still a complex and expensive process. Here, we proposed a greener and more economical route for the synthesis of pregnatetraenedione, which was achieved via the conversion of phytosterols to an uncommon steroid compound, 9a-hydroxy-3-oxo-4,17(20)-pregna-diene-20-carboxylic acid (9-OHPDC), by an engineered Mycolicibacterium neoaurum. 9-OHPDC is a metabolite of sterols obtained by partially degrading its C17 side-chain and hitherto it is difficult to exclusively produce due to its complex metabolic process. In this study, we systematically investigated the determinants related to the generation of 9-OHPDC in the metabolic process of phytosterols and developed a 9-OHPDC-producing strain with the methyl-esterified 9-OHPDC (9-OHPDC-M) as the main product by metabolic engineering. The production of 9-OHPDC and 9-OHPDC-M respectively reached 9.86 g L-1 and 1.27 g L-1 in about 6 days and the total mole yield was more than 85.9%. Using 9-OHPDC-M as a synthon, subsequently, a four-step chemical process for the synthesis of pregnatetraenedione was designed and verified, which was composed of the following steps: hydrolysis of 9-OHPDC-M to 9-OHPDC, decarboxylation rearrangement, dehydration and A1 dehydrogenation. From phytosterols to pregnatetraenedione, the combined microbial and chemical process showed a total weight yield of up to 35.4%, significantly higher than that of the current industrial routes. In addition, compared with the current routes, the new synthesis route has the advantages of shorter reaction steps, milder reaction conditions, reduced use of organic solvents and abandonment of toxic catalysts. In a word, this study provided a green route for the production of pregnatetraenedione, which can be used for corticosteroid production in industry. [ABSTRACT FROM AUTHOR]

Volatile organic solvents are used in almost every industry currently in operation. Their key advantage, being easily removed from products, is overshadowed by the issues associated with their vapour emissions, inhalation risks, smog formation, and flammability. There is, therefore, a dire need for replacement solvents that are much less volatile and yet are as easily removed from products. Switchable-hydrophilicity solvents (SHS) meet this need. SHS are solvents that alternate between water-miscible and water-immiscible states upon the application of a trigger. Carbon dioxide functions as the trigger, as it acidifies the solution and causes protonation of the switchable solvent, which in the past has almost always been a liquid amine. Anionic SHS (ASHS) systems, a recently discovered variation on the idea of an SHS, consist of a hydrophobic carboxylic acid paired with a water-soluble base. In these systems, the low miscibility carboxylic acid (in its neutral state) is combined with a base dissolved in water. Avery small number of ASHS have been reported, but they can only function in the presence of an amine and an unacceptably large excess of water. We sought an SHS that has as little toxicity as possible, and for that reason, we preferred one that contains no amine at all. We now report that the combination of branched carboxylic acids and a substoichiometric quantity of either NaHCO3 or NaOH forms an SHS with very little toxicity and does not require a large excess of water. Two applications of these new switchable solvents are described. [ABSTRACT FROM AUTHOR]

The synthesis of 2,5-furandicarboxylic acid (FDCA) for the production of the sustainable bioplastic polyethylenefuroate (PEF) represents a topic of strong scientific and commercial interest. However, despite extensive research, the development of an efficient process for the synthesis of FDCA still faces difficult challenges. The principle cause is the strong dependence of the reactions involved on the solvent employed and difficulties in isolating the intermediate 5-HMF, leading to issues in performing the oxidation step which is favoured only in water, while 5-HMF formation is promoted in ionic liquids and other organic solvents. In this study we exploited ionic liquids as efficient solvents for the synthesis of HMF from sugars with MnO2 as catalysts for the in situ oxidation of HMF into a dialkylimidazolium furan carboxylate ([dbmim]-FDC). The advantage in forming the imidazolium salt instead of the diacid form lies in the easier separation of this compound from the reaction mixture at low concentration (<2%) through antisolvent addition (ethanol) and its conversion into FDCA through acidification. This process represents a new efficient methodology to isolate FDCA directly from sugars such as glucose and fructose at isolated yield higher than 80% from these substrates, representing a step forward for the development of a technoeconomically efficient process for the production of biobased plastics. [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]

Covalent organic frameworks (COFs), as an emerging crystalline porous material, have drawn considerable attention in many fields. Therefore, facile preparations of COFs using green and mild methods are necessary and worthwhile goals. In this study, four COFs with different morphologies were successfully synthesized by adopting 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTP) as ligands via a green reaction medium composed of polyethylene glycol 400(PEG-400) and water (H2O). In addition, the versatility of this green reaction medium in the synthesis of other COFs was also investigated. More importantly, we have preliminarily explored the mechanism by which PEG-based aqueous solutions modulate the morphology of COFs. This unique strategy not only avoids the use of higher temperatures and harmful organic solvents but also opens up a new idea for the morphological regulation of COFs to a certain extent. [ABSTRACT FROM AUTHOR]

A general visible-light-induced catalyst-/additive-free strategy was developed for the construction of various aroylated heterocycles (55 examples, up to 95% yield, including modification of pharmaceuticals and natural products) such as thioflavones, benzimidazo[2,1-a]isoquinolin-6(5H)-ones, indolo[2,1-a]isoquinolin-6(5H)ones, quaternary 3,3-dialkyl 2-oxindoles, quinoxalin-2(1H)-ones, and benzo[e][1,2,3]oxathiazine 2,2-dioxides in a green solvent (dimethyl carbonate) under air and room temperature conditions. This practical acylation process was achieved using 4-acyl-1,4-dihydropyridines (acyl-DHPs) as acylating reagents under mild conditions, avoiding the use of catalysts, bases, additional oxidants, and traditional organic solvents. [ABSTRACT FROM AUTHOR]

In order to replace conventional organic solvents with more benign equivalents such as ionic liquids or eutectic solvents, in this work we attempt to develop a simple and ecofriendly process using these alternative solvents for the extraction of astaxanthin and β-carotene from Phaffia rhodozyma biomass, which could simultaneously be used as a colorant and plasticizer agent for the preparation of bioactive starch-based biodegradable films without further purification. The use of cholinium-based eutectic solvents appears to be a promising solution envisioning the development of functionalized carotenoid-rich biofilms. [ABSTRACT FROM AUTHOR]

The present report focuses on the solvent effect on furfural production from xylose in biphasic systems with methods including combined experiments, molecular dynamics (MD) simulations and density functional theory (DFT) calculations. Six most effective and commonly used biphasic solvents for furfural production were comparatively analyzed and discussed based on the kinetic study, partition coefficient, degradation behavior of furfural in organic solvents, distribution of solvent molecules around xylose/furfural molecules, hydrogen bonding, moving trajectories of xylose/furfural, and the solvation free energy. During the hydrothermal reaction of xylose to furfural in biphasic systems, it was found that the conversion efficiency of biphasic systems can be ordered as DCM/H2O > 2-MTHF/H2O > 2-butanol/H2O ≈ MIBK/H2O > CPME/H2O > toluene/H2O according to the xylose conversion and furfural yield, which are dominated by the solvation free energy (ΔGsol) of furfural in organic solvents, and also be affected by three other factors, namely, the maximum solubility of furfural in organic solvents, the ΔGsol value of organic solvents in water, and the side reaction of furfural in organic solvents. The degradation rate of furfural in 2-butanol was detected to be the fastest, and molecular dynamics simulation data showed that the hydrogen bonding between furfural and 2-butanol may accelerate the degradation of furfural. DCM has excellent extraction ability for furfural, and the maximum furfural yield in the DCM/H2O system (81.64%) is much higher than that in other systems during the hydrothermal reaction without additional catalysts. [ABSTRACT FROM AUTHOR]

The Suzuki–Miyaura coupling reaction of electron-poor aryl chlorides in the synthesis of crop protection-relevant active ingredients in water is disclosed. Optimisation of the reaction conditions allowed running the reaction with 50 ppm of Pd-catalyst loading without an additional organic solvent in the cross-coupling reaction step in short reaction times. The system was optimised for the initial cross-coupling step of the large scale produced fungicides Boscalid, Fluxapyroxad and Bixafen up to 97% yield. It is also shown that the Suzuki–Miyaura reaction can be easily scaled up to 50 g using a simple product separation and purification using environmentally benign solvents in the work-up. To show the usability of this method, it was additionally applied in the three-step synthesis of the desired active ingredients. [ABSTRACT FROM AUTHOR]

The fabrication of lead halide perovskites involves different types of organic solvents, which are not only harmful to the environment but also expensive. Herein, we present an ultimately green process to prepare CH3NH3PbBr3 (MAPbBr3) nanowires without using any organic solvents, acids, and alkalis. According to the formula of Pb(OH)Br, only PbBr2 and water are used to synthesize Pb(OH)Br. Subsequently, the Pb(OH)Br nanowires are converted into MAPbBr3 nanowires via a thermal evaporation technique (i.e., exposing Pb(OH)Br nanowires to MABr vapor). The prepared MAPbBr3 nanowires show comparable optical properties to those prepared using organic solvents. Such an ultimately green fabrication method can alleviate the environmental concerns and reduce the cost of perovskite commercialization. [ABSTRACT FROM AUTHOR]

We show the effective conversion of xylose into furfural, with a selectivity >90 mol%, in an aqueous–organic three-solvent system, which is composed of an apolar aromatic solvent, a polar organic solvent and acidic water and helps in catalyzing the formation of furfural. We couple this with a pre-extraction step of xylose as a boronic diester into a promising integrated process for valorising a diluted xylose hydrolysate. This process promises facile recovery of furfural and good recycling of all solvent components. The use of the boronic diester was found to be irrelevant for obtaining high selectivity, as its hydrolysis under the reaction conditions is fast. Surprisingly, the >90 mol% selectivity requires the three-solvent system to transition from biphasic to monophasic under the reaction conditions. Phenylboronic acid (PBA) used to extract xylose was found to be instrumental to this transition; PBA-lean media (<20 mM PBA) remain biphasic under the reaction conditions and deliver only 70 mol% selectivity. Water partial pressure measurements across the phase transition temperature confirm the occurrence of the phase transition. The increase of the apolar nature of the reaction medium when transitioning from biphasic to monophasic operation, reached upon mixing of the aromatic solvent with the water–polar organic phase, is likely responsible for the improved selectivity. The presence of an aromatic solvent in the mixture is important, probably due to its interaction with PBA that is instrumental to achieving the phase transition. A 1 : 1 : 1 toluene–sulfolane–water (pH = 1) mixture and [PBA] > 20 mM resulted in the highest observed xylose-to-furfural selectivity (95 mol%). [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DES) are attracting great attention as a green alternative to hazardous organic solvents for the extraction of valuable bioactive compounds from agricultural and processing waste. In this study, the simultaneous extraction and de-glycosylation of quercetin derivatives from apple pomace was achieved by using various DES made of choline chloride and different types of carboxylic acids. The content of quercetin derivatives was similar in DES and conventional methanol extracts, but their relative amounts were distinctively different due to de-glycosylation during DES extraction. Chromatographic and spectroscopic analyses allowed the determination of the structures of the glycosylated quercetins, and revealed that the proportion of the quercetin aglycon in DES extracts can be controlled by the DES composition, extraction temperature and duration of extraction. Of all quercetin glycoconjugates present, quercetin-3-O-α-arabinofuranoside was more prone to de-glycosylation during DES extraction than any other quercetin derivative. Furthermore, the antioxidant activity of the DES extracts was higher than that of methanol extracts, likely due to the increase of quercetin aglycon content during extraction. These data show the potential to extract and de-glycosylate quercetin derivatives in a single step using green DES to generate bioactive preparations with enhanced activity. [ABSTRACT FROM AUTHOR]