Reactions In Organic Media Research Articles

Preparation and Characterization of Magnetic Material/Chitosan Composite Modified with Glycidyl-Trimethylammonium Chloride

Glycidyl-trimethylammonium chloride (GTMAC) containing quaternary ammonium (QA) groups is commonly used as a base catalyst for any organic reaction. This research prepared a novel composite of GTMAC attached to chitosan-coated magnetic material (MM/Chi/GTMAC) using a precipitation method. The effect of chitosan and GTMAC contents on MM/chi/GTMAC properties was studied, where the chitosan content varied from 0, 0.3, 0.5, 1.0, and 3.0 mol, and GTMAC varied from 0, 0.3, 0.8, 1.0, 1.5, and 3 mL with the constant mass of MM (0.4640 g). The physicochemical and morphological properties were characterized with FTIR, SEM-EDX, XRD, TGA, UV-vis, AAS, and zeta-sizer, and the magnetic strength was simply tested with an external magnet. The result showed that a mixture containing chitosan and GTMAC of 0.358 g and 1.5 mL was an optimum composition, in which MM/chi(0.5)/GTMAC(1.5) has high thermal stability, low chitosan and Fe solubility, and optimum content of QA (0.284 mol/g) without loss of magnetic strength. The higher the amount of chitosan, the lower the magnetic properties, and the higher the GTMAC did not increase the QA content. Therefore, the composite produced has the potential to be a novel heterogeneous base catalyst that is quickly recovered from any organic reaction media.

OBTENÇÃO DE AMINAS PRIMÁRIAS A PARTIR DA REDUÇÃO DE NITROCOMPOSTOS AROMÁTICOS VIA PROTOCOLOS DE REAÇÕES SUSTENTÁVEIS PARTE II: EM MEIO ORGÂNICO

SYNTHESIS OF PRIMARY AMINES FROM THE REDUCTION OF AROMATIC NITRO COMPOUNDS THROUGH SUSTAINABLE REACTION PROTOCOLS PART II: REACTIONS IN ORGANIC MEDIA. The reduction of nitroarenes is the main methodology to produce anilines, important precursors of building blocks, dyes, and drugs. Continuing our goal of describing sustainable methodologies for the reduction of nitroarenes to their respective anilines, herein we compile selected reaction protocols, using organic medium, reported from 2017 to 2023, in order to provide a comprehensive and complementary view of the new processes and catalysts developed during this period.

Photochemical cyclopropanation in aqueous micellar media - experimental and theoretical studies.

While in nature, reactions occur in water-based confined compartments, for a long time, water has been often regarded as an unsuitable medium for organic reactions. We have, however, found that photochemical cyclopropanation of styrenes with diazo compounds or their precursors can be performed in micellar systems. COSMO-RS studies revealed that the reactivity correlates with the predicted critical micelle concentration (CMC), with higher CMC values delivering higher yields.

Application of Deep Eutectic Solvents in Formation of Carbon‐Carbon and Carbon‐Heteroatom Bond by Cross‐Coupling Reactions

AbstractDeep eutectic solvents (DESs), known as the emerging organic reaction medium in the 21st century, have many advantages such as cheap, readily available, non‐pollution, and biodegradable. Its good properties make it an alternative to volatile organic solvents. The insights in to carbon‐carbon and carbon‐heteroatom bond formations and their applications since 2017 are encapsulated, which not only highlighting the significant achievements pertaining to the important role of DESs as solvents but also including popular named organic reactions for cross‐coupling reactions relating to the nature of DESs and the core optimum conditions. The review also encompasses a brief overview of the current situation and future development of DESs.

Biotransformations with Imine Reductases: Design of a Practical Process Avoiding an Extractive Work‐Up by Entrapment of Water and Enzymes in an Immobilized Phase

AbstractA process concept for the asymmetric biocatalytic reduction of heterocyclic imines addressing the efficiency of the reaction as well as downstream‐processing steps was studied by utilizing a “heterogenized aqueous phase”, which contains the needed enzymes and cofactor within a superabsorber (polyacrylate) network, for the biotransformation. The immobilized biocatalytic system, which comprises an imine reductase (IRED), NADPH and an alcohol dehydrogenase for cofactor‐recycling, enables to run the reaction in pure organic medium. Thus, instead of an extractive work‐up as typical solution for biotransformations in aqueous medium, which, however, can be tedious due formation of emulsions, this type of IRED‐catalyzed process leads to a simplified work‐up consisting only of a decantation of the liquid organic reaction medium with the product from the heterogenized aqueous biocatalyst system. Exemplified for the (R)‐enantioselective reduction of 1‐methyl‐3,4‐dihydroisoquinoline by the IRED of Streptomyces viridochromogenes as a model reaction, a process was developed leading to 98 % conversion, 88 % yield and >99 % ee at a substrate concentration of 40 mM.

Enzymatic Synthesis and Molecular Modelling Studies of Rhamnose Esters Using Lipase from Pseudomonas stutzeri.

Rhamnolipids are becoming an important class of glycolipid biosurfactants. Herein, we describe for the first time the enzymatic synthesis of rhamnose fatty acid esters by the transesterification of rhamnose with fatty acid vinyl esters, using lipase from Pseudomonas stutzeri as a biocatalyst. The use of this lipase allows excellent catalytic activity in the synthesis of 4-O-acylrhamnose (99% conversion and full regioselectivity) after 3 h of reaction using tetrahydrofuran (THF) as the reaction media and an excess of vinyl laurate as the acyl donor. The role of reaction conditions, such as temperature, the substrates molar ratio, organic reaction medium and acyl donor chain-length, was studied. Optimum conditions were found using 35 °C, a molar ratio of 1:3 (rhamnose:acyldonor), solvents with a low logP value, and fatty acids with chain lengths from C4 to C18 as acyl donors. In hydrophilic solvents such as THF and acetone, conversions of up to 99–92% were achieved after 3 h of reaction. In a more sustainable solvent such as 2-methyl-THF (2-MeTHF), high conversions were also obtained (86%). Short and medium chain acyl donors (C4–C10) allowed maximum conversions after 3 h, and long chain acyl donors (C12–C18) required longer reactions (5 h) to get 99% conversions. Furthermore, scaled up reactions are feasible without losing catalytic action and regioselectivity. In order to explain enzyme regioselectivity and its ability to accommodate ester chains of different lengths, homology modelling, docking studies and molecular dynamic simulations were performed to explain the behaviour observed.

Geomimetic Hydrothermal Synthesis of Polyimide-Based Covalent Organic Frameworks.

Despite its abundance, water is not widely used as a medium for organic reactions. However, under geothermal conditions, water exhibits unique physicochemical properties, such as viscosity and a dielectric constant, and the ionic product become similar to those of common organic solvents. We have synthesized highly crystalline polyimide-based covalent organic frameworks (PICs) under geomimetic hydrothermal conditions. By exploiting triphenylene-2,3,6,7,10,11-hexacarboxylic acid in combination with various aromatic diamines, PICs with various pore dimensions and crystallinities were synthesized. XRD, FT-IR, and DFT calculations revealed that the solubility of the oligomeric intermediates under hydrothermal conditions affected the stacking structures of the crystalline PICs. Furthermore, the synthesized PICs demonstrate promising potential as an anode material in lithium-ion batteries owing to its unique redox-active properties and high surface area.

Geomimetic Hydrothermal Synthesis of Polyimide‐Based Covalent Organic Frameworks

AbstractDespite its abundance, water is not widely used as a medium for organic reactions. However, under geothermal conditions, water exhibits unique physicochemical properties, such as viscosity and a dielectric constant, and the ionic product become similar to those of common organic solvents. We have synthesized highly crystalline polyimide‐based covalent organic frameworks (PICs) under geomimetic hydrothermal conditions. By exploiting triphenylene‐2,3,6,7,10,11‐hexacarboxylic acid in combination with various aromatic diamines, PICs with various pore dimensions and crystallinities were synthesized. XRD, FT‐IR, and DFT calculations revealed that the solubility of the oligomeric intermediates under hydrothermal conditions affected the stacking structures of the crystalline PICs. Furthermore, the synthesized PICs demonstrate promising potential as an anode material in lithium‐ion batteries owing to its unique redox‐active properties and high surface area.

Design of Novel Uncharged Organic Superbases: Merging Basicity and Functionality.

ConspectusOne of the constant challenges of synthetic chemistry is the molecular design and synthesis of nonionic, metal-free superbases as chemically stable neutral organic compounds of moderate molecular weight, intrinsically high thermodynamic basicity, adaptable kinetic basicity, and weak or tunable nucleophilicity at their nitrogen, phosphorus, or carbon basicity centers. Such superbases can catalyze numerous reactions, ranging from C-C bond formation to cycloadditions and polymerization, to name just a few. Additional benefits of organic superbases, as opposed to their inorganic counterparts, are their solubility in organic reaction media, mild reaction conditions, and higher selectivity. Approaching such superbasic compounds remains a continuous challenge. However, recent advances in synthetic methodology and theoretical understanding have resulted in new design principles and synthetic strategies toward superbases. Our computational contributions have demonstrated that the gas-phase basicity region of 350 kcal mol-1 and even beyond is easily reachable by organosuperbases. However, despite record-high basicities, the physical limitations of many of these compounds become quickly evident. The typically large molecular weight of these molecules and their sensitivity to ordinary reaction conditions prevent them from being practical, even though their preparation is often not too difficult. Thus, obviously structural limitations with respect to molecular weight and structural complexity must be imposed on the design of new synthetically useful organic superbases, but strategies for increasing their basicity remain important.The contemporary design of novel organic superbases is illustrated by phosphazenyl phosphanes displaying gas-phase basicities (GB) above 300 kcal mol-1 but having molecular weights well below 1000 g·mol-1. This approach is based on a reconsideration of phosphorus(III) compounds, which goes along with increasing their stability in solution. Another example is the preparation of carbodiphosphoranes incorporating pyrrolidine, tetramethylguanidine, or hexamethylphosphazene as a substituent. With gas-phase proton affinities of up to 300 kcal mol-1, they are among the top nonionic carbon bases on the basicity scale. Remarkably, the high basicity of these compounds is achieved at molecular weights of around 600 g·mol-1. Another approach to achieving high basicity through the cooperative effect of multiple intramolecular hydrogen bonding, which increases the stabilization of conjugate acids, has recently been confirmed.This Account focuses on our efforts to produce superbasic molecules that embody many desirable traits, but other groups' approaches will also be discussed. We reveal the crucial structural features of superbases and place them on known basicity scales. We discuss the emerging potential and current limits of their application and give a general outlook into the future.

Micro-Aqueous Organic System: A Neglected Model in Computational Lipase Design?

Water content is an important factor in lipase-catalyzed reactions in organic media but is frequently ignored in the study of lipases by molecular dynamics (MD) simulation. In this study, Candida antarctica lipase B, Candida rugosa lipase and Rhizopus chinensis lipase were used as research models to explore the mechanisms of lipase in micro-aqueous organic solvent (MAOS) media. MD simulations indicated that lipases in MAOS systems showed unique conformations distinguished from those seen in non-aqueous organic solvent systems. The position of water molecules aggregated on the protein surface in MAOS media is the major determinant of the unique conformations of lipases and particularly impacts the distribution of hydrophilic and hydrophobic amino acids on the lipase surface. Additionally, two maxima were observed in the water-lipase radial distribution function in MAOS systems, implying the formation of two water shells around lipase in these systems. The energy landscapes of lipases along solvent accessible areas of catalytic residues and the minimum energy path indicated the dynamic open states of lipases in MAOS systems differ from those in other solvent environments. This study confirmed the necessity of considering the influence of the microenvironment on MD simulations of lipase-catalyzed reactions in organic media.

Multifunctional Melamine Foam Assisted Lead Halide Perovskites for Highly Efficient and Long‐Term Photocatalytic CO2 Reduction Under Pure Water

Application of lead halide perovskites in CO2 photoreduction in pure H2O medium is restricted, owing to the inherent instability and high toxicity of lead. Herein, 3D melamine foam (MF) with an interconnected porous structure is selected as a multifunctional assistance to solve these problems. Three‐dimensionality of MF can avoid direct touches of CsPbX3 (X = Br, I) with liquid H2O, preventing damage of H2O. Porosity of MF can accelerate H2O evaporation by its strong adsorption and photothermal effects, which will overcome the drawback of low CO2 solubility in aqueous solution, achieving a quick and sufficient mixture of CO2 with H2O vapor. These functions contribute to realize highly efficient CO2 reduction by CsPbX3 in pure H2O medium. The best products and electron consumption yields of the composite reach 42.08 and 161.84 μmol g−1 h−1, respectively, which surpass most of the other CsPbX3‐related works in H2O or organic reaction media. MF/CsPbBr3 also presents long‐term stability, with product yields not showing any obvious decrease after continuous reaction for 104 h. Moreover, strong adherence of MF toward perovskites allows a good recoverability of CsPbX3, avoiding pollution of lead leakage to the environment.

Deep Eutectic Solvent Choline Chloride/p-toluenesulfonic Acid and Water Favor the Enthalpy-Driven Binding of Arylamines to Maleimide in Aza-Michael Addition.

Deep eutectic solvents (DESs) have been considered "the organic reaction medium of the century" because they can be used as solvents and active catalysts in chemical reactions. However, experimental and theoretical studies are still needed to provide information on the structures of DESs, the kinetics and thermodynamics properties, the interactions between the DESs and the substrates, the effect of water on the DES supramolecular network and its physicochemical properties, and so forth. This information is very useful to understand the essence of the processes that take place in the catalysis of chemical reactions and, therefore, to help in the design of a DES for a specific reaction and sample. This article shows a systematic study of the impact of DES choline chloride/p-toluenesulfonic acid and DES choline chloride/p-toluenesulfonic acid-water in the aza-Michael addition of arylamines to maleimide to obtain aminopyrrolidine-2,5-dione derivatives. The derivatives are obtained under very mild reaction conditions with good yield. The global reaction is exothermic, spontaneous, permitted by enthalpy, and prohibited for entropy. The calculated potential energy surface shows a reaction mechanism of six steps controlled by enthalpy (except the last step that is controlled by entropy). The water incorporated in the supramolecular DES complex stabilizes the transition states and favors the enthalpy-driven binding. A set of H/D exchange NMR experiments validates the transition state existing in the fourth stage of the mechanism.

Photoelectrochemistry for Measuring the Photocatalytic Activity of Soluble Photosensitizers

AbstractWe introduce a rapid method to test the photocatalytic activity of singlet‐oxygen‐producing photosensitizers using a batch cell, a LED laser and a conventional potentiostat. The strategy is based on coupling of photo‐oxidation of hydroquinone and simultaneous electrochemical reduction of its oxidized form at a carbon electrode in an organic solvent (methanol). This scheme gives an immediate response and avoids complications related to long‐term experiments such as oxidative photo‐degradation of photosensitizers and singlet oxygen traps by reactive oxygen species (ROS). Among the tested compounds, a fluoro‐substituted subphthalocyanine showed the highest photocurrent and singlet oxygen quantum yield (ΦΔ) in comparison to phenoxy‐ and tert‐butyl‐substituted analogues, whereas the lowest photocurrents and yields were observed for aggregated and dimeric phthalocyanine complexes. The method is useful for fast screening of the photosensitizing activity and represents the first example of one‐pot coupling of electrochemical and photocatalytic reactions in organic media.

Convergent Cascade Catalyzed by Monooxygenase-Alcohol Dehydrogenase Fusion Applied in Organic Media.

With the aim of applying redox-neutral cascade reactions in organic media, fusions of a type II flavin-containing monooxygenase (FMO-E) and horse liver alcohol dehydrogenase (HLADH) were designed. The enzyme orientation and expression vector were found to influence the overall fusion enzyme activity. The resulting bifunctional enzyme retained the catalytic properties of both individual enzymes. The lyophilized cell-free extract containing the bifunctional enzyme was applied for the convergent cascade reaction consisting of cyclobutanone and butane-1,4-diol in different microaqueous media with only 5 % (v/v) aqueous buffer without any addition of external cofactor. Methyl tert-butyl ether and cyclopentyl methyl ether were found to be the best organic media for the synthesis of γ-butyrolactone, resulting in about 27 % analytical yield.

Dramatically Enhanced Stability of Silver Passivated Dicalcium Nitride Electride: Ag-Ca2N

Electrides have received considerable attention due to their exotic properties. However, the high reactivity with oxygen and moisture immediately decomposed electrides in an ambient air environment. Here we passivated dicalcium nitride electride (Ca2N:e–) with silver via a wet chemical approach (Ag-Ca2N), significantly enhancing stability up to 17 min at room temperature in an ambient air environment. The Ca2N:e– was employed as a reducing agent due to the low work function (2.6 eV), high mobility, and high electron concentration facilitating electron transfer to Ag+ ion in an aprotic cosolvent. Moreover, the noble metal surface passivation (thickness: 55 nm) was achieved with negligible increase in work function of Ag-Ca2N (2.78 eV). The optimized molar ratio of AgNO3/Ca2N:e– was 0.5. The enhanced stability of Ag-Ca2N in organic reaction medium enabled successful aldol condensation reaction outside the glovebox, with a high α,β-unsaturated ketone yield of 75.4%, without involving environmentally harmful strong acid or base. The enhanced stability and low work function may realize practical economic applications of Ag-Ca2N.

Surface-controlled Nb2O5 nanoparticle networks for fast Li transport and storage

Hybrid supercapacitors are successfully introduced to reduce the gap between high-capacity battery electrodes and high-power capacitor electrodes in case of electrochemical energy storage devices. Niobium pentoxide (Nb2O5) has attracted great interest for hybrid supercapacitors because of its moderate capacity and excellent cycle performance. However, its low electronic conductivity is still a major problem. Carbon is usually incorporated to address this limitation. Here, we report the Nb2O5 nanoparticle networks to facilitate electronic transport via continuous connection of materials. Additionally, the high surface area of the nanoparticles is maintained. The Nb2O5 nanoparticle network was synthesized using a simple solvothermal reaction in organic media. The materials characterization was performed using X-ray diffraction analysis, and scanning and transmission electron microscopies. The charge storage mechanism of the synthesized Nb2O5 material was investigated by cyclic voltammetry. In galvanostatic charge–discharge tests, the synthesized Nb2O5 nanoparticle network electrode exhibited stable cycle performance and remarkable rate capability without carbon incorporation.

Investigating the structural properties of the active conformation BTL2 of a lipase from Geobacillus thermocatenulatus in toluene using molecular dynamic simulations and engineering BTL2 via in-silico mutation.

The discovery or development of thermoalkalophilic lipases that show high levels of catalytic activity in organic solvents would have important industrial ramifications. However, this goal is yet to be achieved because organic solvents induce structural changes in lipases that suppress their catalytic abilities. A deep understanding of these structural changes to lipases in the presence of organic solvents is required before strategies can be devised to stop them from occurring. In this work, we investigated the effects of an organic reaction medium, toluene, on the structure of the Bacillus thermocatenulatus lipase BTL2 using MD simulation. The main aims were to identify the regions of the protein that are particularly sensitive to the presence of an organic solvent, and how the presence of a hydrophobic medium affects the overall stability of the enzyme. Upon analyzing how the behavior of the enzyme differed in aqueous and hydrophobic media, it was found that many significant zones of the protein suffer in the presence of an organic solvent, which increases the rigidity of the system. This was readily apparent when we investigated important noncovalent interactions (salt bridges) and probed how distances between the atoms of the catalytic triad Ser114, Asp318, and His359 change in the presence of toluene. Moreover, the high tendency for the system to destabilize in toluene was explained by the results of FoldX calculations. Calculations showed that the addition of a small amount of water to the hydrophobic reaction environment should restore the required flexibility of BTL2. The insights gained from the analysis of our simulations allowed us to propose a modification of BTL2, the G116P mutation, that should result in the structural behavior of BTL2 in organic solvent being closer to that of BTL2 in water.

Assessing the Potential Mechanisms of Isomerization Reactions of Isoprene Epoxydiols on Secondary Organic Aerosol.

Laboratory and field measurements have demonstrated that isoprene epoxydiol (IEPOX) is the base component of a wide range of chemical species found in isoprene-derived secondary organic aerosol (SOA). To address newly raised questions concerning the chemical identities of IEPOX-derived SOA, the results of laboratory experiments carried out in bulk aqueous and organic media and analyzed via nuclear magnetic resonance spectroscopy and computed free energies of possible products are reported. The IEPOX nucleophilic addition product 2-methyltetrol was found to react too slowly in aqueous solution to explain the previous observation of tetrahydrofuran-based species. The IEPOX isomerization reactions in organic media were shown to mainly produce 3-methyltetrahydrofuran-2,4-diols, which were also established by the computational results as one of the most thermodynamically favorable possible IEPOX reaction products. However, these isomerization reactions were found to be relatively slow as compared to nucleophilic addition reactions, indicating that their occurrence on ambient SOA might be limited to low water content situations. No evidence was found for the production of the C5 alkene triols or 3-methyltetrahydrofuran-3,4-diols previously reported for IEPOX reaction on SOA as analyzed via the gas chromatography/electron ionization-quadrupole mass spectrometry with prior trimethylsilyl derivatization method.

DEGRADATION OF POLY(ETHYLENETEREPHTALATE) WASTE TO OBTAIN OLIGOMERS USING A ZINC COMPLEX AS CATALYST

Thermal degradation of Poly(ethylene terephthalate) (PET) bottles waste was carried out by glycolysis using triethyleneglycol (TEG) as nucleophilic agent and N 1 ,N 2-bis(2-aminobenzyl)-1,2-diaminoethane zinc(II) (ABEN), in order to test this compound as catalyst in the degradation of PET until to obtain short chains of polyester (oligomers). The depolymerization processes was tested at 180, 190 and 210 °C, and two molar ratios of PET:TEG (1:1.3 and 1:2.6), the amount of catalyst used was fixed at 1% in relation to PET, the best experiment of PET glycolysis was found at 190 °C during two hours in a mass relation PET:TEG 1:1.3. All products were analyzed by Fourier transform infrared spectroscopy (IR), gel permeation chromatography (GPC) and differential scanning calorimetry (DSC), the behavior of the reaction rate was studied for the best experiment by measuring the amount of degraded PET at different glycolysis time. The degradation of PET was favored with the use of ABEN, which accelerates the reaction, obtaining oligomers in the absence of an organic solvent or reaction medium, this is the most efficient catalyst found so far. The oligomers were obtained with molecular weight between 900 and 1500 g mol-1 depending on the reaction time, 60 min was the less time of the total glycolysis of PET. Also was found that the molecular weight of the oligomers increased along the glycolysis, due to the recombination with TEG and ethylene glycol produced in degradation.

Analysis of Aspergillus sp. lipase immobilization for the application in organic synthesis

Nowadays, for the industrial implementations, especially in the area of organic synthesis, immobilized enzymes are preferred over their soluble forms. Present study aimed to find fast, cost-efficient, and effective way of lipase immobilization for the use in organic media. Lipase from Aspergillus sp. (Resinase A 2X) was immobilized utilizing cross-linking of enzyme aggregates, covalent immobilization on magnetite particles and adsorption-immobilization using pyrolyzed sugar industry waste product as a novel type of carrier. Covalently- and adsorption-immobilized preparations exhibited greater specific activities (5.61±0.18U/mg and 14.2±0.63U/mg, respectively) in organic reaction media than the soluble form of the enzyme (0.06±0.01U/mg). Enzyme immobilized on the sugar industry waste pyrolyis product was determined as a best way to hyperactivate Resinase A 2X and was chosen for the synthesis of flavor and fragrance compound 2-phenylethyl butanoate. Furthermore, in order to optimize 2-phenylethyl butanoate synthesis conditions, central compositional experimental plan was designed using RSM. It showed that in optimal reaction conditions (4.5h at 40.7°C, with 0.1M of substrate) conversion higher than 90% can be achieved. Studies of the operational stability showed enhanced reusability of adsorption-immobilized lipase (with each cycle, efficiency of the 2-PB synthesis diminished by 20–30%). The use of the sugar industry waste pyrolysis product as a carrier provides a novel, cheap, fast, cost-efficient and eco-friendly way of immobilization with some crucial points to be noted for the best productivity.