Inorganic Base Research Articles

High mechanical strength conductive inorganic–organic composite membranes for chiral separation and in situ cleaning

Enantiomeric separation based on membrane techniques has the advantages of energy efficiency, sustainable operation, and no additives, but there are no commercially available chiral membranes. The main reasons restricting the development of chiral membranes are separation specificity, poor mechanical properties, and membrane fouling. Therefore, we developed a novel chiral membrane with a stainless steel mat mesh as the base and β-cyclodextrin blended in cellulose acetate as the functional layer. The organic layer was loaded on the inorganic base by nonsolvent-induced phase inversion, and the two post treatments were optimized. The results indicate that the optimal percent enantiomeric excess (ee%) was 96.98 ± 5.22 % for d,l-tryptophan, 46.38 ± 1.65 % for d,l-phenylalanine, 11.50 ± 2.52 % for (RS)-propranolol, and 5.16 ± 0.88 % for (RS)-warfarin. The mechanical properties of stainless steel chiral composite membranes are better than those of other chiral membranes, and the Young's modulus values reached 3234 MPa. In addition, ultrasonic cleaning and electrolytic cleaning were successfully tested to solve the membrane fouling problem, and a comparative study indicated that electrolytic cleaning has low energy consumption and is a fast and effective cleaning method that can achieve flux recovery. These results indicate that conductive chiral membranes can achieve long-term separation of chiral compounds and have great potential for industrial applications.

Recent advances in the utilization of glycerol for the production of lactic acid by catalysis

AbstractIn this review, the research progress on catalytic conversion of glycerol to lactic acid or lactate esters and the reaction mechanisms with different catalysis systems are summarized. Both homogeneous catalysts, including inorganic bases and metal complexes, and heterogeneous catalysts, including metal oxides, molecular sieves, polyoxometalates and noble and non‐noble metals, are discussed. In particular, the influence of catalyst components, the physical and chemical properties of the catalysts and additives and solvents on the catalytic performances are highlighted. In comparison, nano‐metal particles or bimetal catalysts could achieve good catalytic performance, in which the alloy and synergistic effects might form under certain conditions. For further improvement of the sustainable transformation of glycerol to lactic acid or lactate esters, attention should still be paid to rational design of novel cost‐effective, high‐efficiency and green catalytic systems. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.

Selective Oxidation of Furfural at Room Temperature on a TiO2-Supported Ag Catalyst

The catalytic performance of the Ag/TiO2 catalyst was evaluated in the oxidation of furfural (FF) to furoic acid (FA) in an alkaline aqueous solution under 15 bar of air in a batch reactor. The catalytic activity, yield, and stability of the catalyst were compared as a function of different reaction parameters including temperature (25–110 °C), nature of the atmosphere, base equivalent (nbase/nFF = 0.25–3), and nature of the inorganic bases used (NaOH, NaHCO3, and Na2CO3). Under optimum conditions, the yield of FA (96%) was achieved at room temperature, with an excellent carbon balance (>98%). The recyclability of the catalyst was also studied and the catalytic activity of the Ag/TiO2 catalyst slightly declined due to an increase in particle size as confirmed by TEM studies.

Discovery of KOH/BrCH2SO2F as Water‐Removable System for Clean, Mild and Robust Synthesis of Amides and Peptides

AbstractHerein we described an efficient, practical, and robust protocol for amides and peptides synthesis from carboxylic acids and amines using the combination of bromomethanesulfonyl fluoride (BMSF) with inorganic base KOH as a water‐removable system. This method is featured with broad substrate scope, excellent functional group compatibility, high yields, operational simplicity, and easy purification, which will exert great potential in amide and peptide synthesis.

Transition-metal-free reaction sequence on solid base: One-pot synthesis of quinoline derivatives catalyzed by Mg-Al hydrotalcite

Quinoline derivatives are important intermediates in the production of pharmaceutical products. Recently, a modified Friedländer quinoline synthesis using stable 2-aminobenzyl alcohols and ketones over transition metal catalysts and inorganic bases have been investigated. In this study, we found that only simple Mg-Al hydrotalcite (HT) was active toward the modified Friedländer quinoline synthesis. Various HT samples were prepared by the co-precipitation method under several pH and Mg-Al ratio conditions. Mg-Al HT prepared at pH 11 exhibited the highest activity among the HT samples and other solid base catalysts. Kinetic and spectroscopic analyses revealed that quinoline formation occurs via base-catalyzed hydrogen transfer between 2-aminobenzyl alcohol and a ketone, followed by the cyclization of the corresponding aldehyde intermediate with a ketone. Mg-Al HT showed wide applicability toward the one-pot synthesis quinoline using various alcohols and ketones and afforded the corresponding products in high yield.

Highly Ordered Supramolecular Assembled Networks Tailored by Bioinspired H-Bonding Confinement for Recyclable Ion-Transport Materials

Highly Ordered Supramolecular Assembled Networks Tailored by Bioinspired H-Bonding Confinement for Recyclable Ion-Transport Materials

Recent Advances in Base-assisted Michael Addition Reactions

Abstract: The Michael addition is an important, highly efficient, and atom-economical method for the diastereoselective and enantioselective C-C bond formation. MA used in the synthesis of natural products and drugs is tandem sequenced reactions. An important tandem sequence of Michael and Aldol additions is the Robinson annulation. MA is a versatile reaction employed for efficient bond formation between electron-poor olefins as Michael acceptors with varied nucleophiles as Michael donors. Apart from being involved in C-C bond formation, MA is also employed in the formation of C-X bond (X=O, N, S, P etc.) giving rise oxa-, aza-, thia-, phospha-Michael addition products. In recent years many articles have been published on MA. The mechanism of MA gives an insight into the reaction is initiated by the base. The present review provides comprehensive information on recent advancements in base-assisted Michael addition reactions including varied organic and inorganic bases, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-Diazabicyclo[2.2.2]octane (DABCO), 4-dimethylaminopyridine (DMAP), triethylamine (Et3N), tributylamine (Bu3N), N,N-diisopropylethylamine (DIEPA), diethylamine (NHEt2), guanidine derivatives, and bifunctional thiourea. A variety of inorganic bases including metal alkoxides, metal acetates, metal hydroxides, metal hydrides, metal carbonates, metal halides, and triphenylphosphine (TPP) can also be successfully used in Michael reactions.

An Efficient Bifunctional Ionic Liquid [BIL] as Solvent and Catalyst System for O-Alkylation of Phenols Under Solvent-Free Conditions: An Environmental Benign Approach

Background: Bifunctional ionic liquid [BIL] was found to be a highly effective catalyst for ether synthesis without any inorganic base or solvent. Using this protocol, different aryl substitutions were reacted with different phenols in good to excellent yields. The BIL is reusable without any loss in catalytic activity for nine consecutive cycles. The Williamson reaction is a convenient renovation in fine chemical synthesis since the ethers are important in both bulk and fine industrial chemicals preparation and academic applications. Method: The mixture of the phenol (1mmol), alcohol (1.2 mmol), and BIL ionic liquid (0.3 mol%) was added to a round-bottomed flask (100 mL) with continuous stirring for 1 hour. Objective: The aim of this study is to highlight the use of BIL to synthesize mixed ethers using substituted phenols and to study the reusability in the next cycle. Results: The products obtained were phenol and substituted phenols containing withdrawing substituents in respectable yields. However, the reactions involving substituted phenols containing electron-donating groups often afford the corresponding products in low yields. Conclusion: BIL is found to be an effective catalyst in the etherification of various unsymmetrical ethers under mild conditions. Bifunctional ionic liquid as a solvent and catalyst will show real rewards by providing a ‘green’ method with the safer procedure, less reaction time periods, mild conditions, easy separation, and ionic liquid recycle.

Nano-bio effects: Interaction of ZnO and DNA-bases

In this study, we report on the complex formation and characterization of nano-bio conjugates synthesized by the sol–gel chemical method. The nano-bio conjugates, consisting of inorganic ZnO nanoparticles (NPs) and organic nitrogenous bases of DNA (Thymine and Cytosine), are investigated using electron microscopies, molecular vibrational analysis and X-ray spectroscopies. In this experimental investigation, we used two basic nitrogenous bases of DNA – Cytosine, and Thymine. The X-ray diffraction patterns of both ZnO NP and the nanoconjugate (NJ) reveal a highly phase pure ZnO structure with negligible changes in the unit cell dimensions. The Raman peaks due to the molecular vibration of C2=O7 and C4=O8 sites of Thymine and C=O and N-H sites in Cytosine are shifted due to the cation affinity after the interaction with ZnO NPs. The shifted XPS spectra towards higher binding energies of the NJ divulge the atomic level interaction between the DNA bases and ZnO NPs at the surface. Moreover, the formation of NJs reduces the surface defect states of the ZnO NPs and increases the fluorescence properties by quenching the oxygen vacancy concentration. Thus, the current study on the interfacial properties of organic–inorganic conjugate materials opens new frontiers for developing novel nano-bio conjugate materials and their integration for targeted drug delivery, biomolecular sensing and therapeutic tools medicine applications.

Crystal Engineering of Ionic Cocrystals Sustained by the Phenol-Phenolate Supramolecular Heterosynthon.

Although crystal engineering strategies are generally well explored in the context of multicomponent crystals (cocrystals) formed by neutral coformers (molecular cocrystals), cocrystals comprised of one or more salts (ionic cocrystals, ICCs) are understudied. We herein address the design, preparation, and structural characterization of ICCs formed by phenolic moieties, a common group in natural products and drug molecules. Organic and inorganic bases were reacted with the following phenolic coformers: phenol, resorcinol, phloroglucinol, 4-methoxyphenol, and 4-isopropylphenol. Nine ICCs were crystallized, each of them sustained by the phenol–phenolate supramolecular heterosynthon (PhOH···PhO–). Such ICCs are of potential utility, and there are numerous examples of phenolic compounds that are biologically active, some of which suffer from low aqueous solubility. The propensity to form ICCs sustained by the PhOH···PhO– supramolecular heterosynthon was evaluated through a combination of Cambridge Structural Database (CSD) mining, structural characterization of nine novel ICCs, and calculation of interaction energies. Our analysis of these 9 ICCs and the 41 relevant entries archived in the CSD revealed that phenol groups can reliably form ICCs through charge-assisted PhOH···PhO– interactions. This conclusion is supported by hydrogen-bond strength calculations derived from CrystalExplorer that reveal the PhOH···PhO– interaction to be around 3 times stronger than the phenol–phenol hydrogen bond. The PhOH···PhO– supramolecular heterosynthon could therefore enable crystal engineering studies of a large number of phenolic pharmaceutical and nutraceutical compounds with their conjugate bases.

Efficient pKa Determination in a Nonaqueous Solvent Using Chemical Shift Imaging.

pKa is an important property of a molecule which impacts many fields, such as drug design, catalysis, reactivity, and environmental toxicity. It is often necessary to measure pKa in nonaqueous media due to the poor solubility of an analyte in water, for example, many compounds of pharmaceutical interest. Although NMR methods to measure pKa in water are well established, determining pKa in organic solvents is laborious and problematic. We present an efficient one-shot method to determine the pKa of an analyte in an organic solvent in a single measurement. Diffusion of an acid into a basic solution of the analyte and a set of pH indicators establishes a pH gradient in the NMR tube. The chemical shift of a pH sensitive resonance of the analyte and the pH of the solution are then determined simultaneously as a function of position along the pH gradient by recording a chemical shift image of the NMR tube. The pKa of the analyte is then determined using the Henderson–Hasselbalch equation. The method can be implemented in any laboratory with a gradient equipped NMR high-field spectrometer and is demonstrated for a range of pharmaceutical compounds and inorganic phosphazene bases.

An inorganic base stripping approach to synthesize N-doped Ti3C2 quantum dots as fluorescence nanoprobe for the simultaneous detection of Co2+ and Ag+ ions

N-doped Ti3C2 quantum dots (N-Ti3C2 QDs) as the fluorescent nanoprobe were synthesized through inorganic base (i.e. KOH) stripping and solvothermal approach. The N-Ti3C2 QDs displayed well-monodispersed near-spherical particles with average size of 2.3 nm, exhibited brightly blue emission and good stability, and possessed 14.46% of fluorescent quantum yield. Upon addition of Co2+ or Ag+ ions, the fluorescence (FL) of N-Ti3C2 QDs could be quenched significantly. Mechanism investigation indicated that the inner filter and static extinguishing effects are responsible for the Co2+ or Ag+ ions induced FL quenching of the N-Ti3C2 QDs. Based on above outcomes, we developed a simple N-Ti3C2 QDs based fluorescent assay for the simultaneous determination of Co2+ and Ag+ ions, with a low detection limit of 0.21 and 0.10 μM, respectively. The assay was used to determine the content of Co2+ and Ag+ in real samples. This work will provide another way for the synthesis of fluorescent N-Ti3C2 QDs and exploited their application in simultaneous detection of Co2+ and Ag+.

Sequential Nucleophilic Addition and Regioselective Ring‐Expansion Reactions of α‐Diazophosphonates with Isatins: Access to 4‐Phosphonylated‐3‐hydroxyquinolin‐2(1H)‐ones

AbstractA sequential protocol of α‐diazophosphonates with isatins to access a series of α‐diazo‐β‐hydroxyphosphonate derivatives via the inorganic base catalysis was reported. The resulting α‐diazo‐β‐hydroxyphosphonates could then be readily transformed to 4‐phosphonylated‐3‐hydroxyquinolin‐2(1H)‐ones with moderate to excellent yields through a catalyst‐free regioselective ring‐expansion rearrangement. Control experiment demonstrates that intramolecular cyclization pathway is more reasonable for the ring‐expansion process. In addition, a benzo[b]thiophene‐derived isatin featured with the inhibition of SARS‐CoV Mpro was also suitable for this transformation and generated the corresponding scaffolds with potential anti‐virus activities for further development.

Growth behavior of β form DL-methionine crystal in the presence of inorganic acids and bases additives: A combination of experiments and molecular dynamics simulation study

Crystal habit plays an important role in processing efficiency and product quality of DL-methionine (DL-met). In this paper, β form DL-met crystals with small aspect ratio are acquired by adding inorganic acids or bases during cooling or evaporation crystallization. Crystal growth experiments were performed to study the effect of additives on β form DL-met growth behavior. It is observed that increasing inorganic acid leads to a decrease while increasing inorganic base leads to a decrease first and then an increase in the growth rate of face (111), increasing inorganic acid leads to an increase then a decrease while increasing inorganic base leads to an increase in the growth rate of face (20–2). Molecular dynamics (MD) simulation is also carried out to predict the crystal habit and further study the mechanism, namely specific adsorption and solvation disruption, of additives on crystal growth. The influence of additives on crystal growth depends on the chemical nature of both crystal faces and additives and the concentration of additives.

Diarylation of N- and O-nucleophiles through a metal-free cascade reaction

Diarylation of N- and O-nucleophiles through a metal-free cascade reaction

The Mizoroki‐Heck Reaction in Tunable Aryl Alkyl Ionic Liquids

AbstractWe report the use of imidazolium based tunable aryl alkyl ionic liquids (TAAILs) as solvents in the Mizoroki–Heck reaction. Different commercially available palladium sources, inorganic bases, TAAILs and reaction conditions were tested for the synthesis of trans‐stilbene using bromobenzene and styrene. A variety of different stilbene derivatives were synthesized with exclusive formation of the (E)‐isomers and isolated yields up to 97 %. We were able to optimize the reaction conditions using only 0.25 mol% of Pd(OAc)2 as the catalyst and a reaction time of 4 hours. No additional ligands or additives are used in the reaction. The catalytic system using TAAILs achieved higher yields than commercially available imidazolium and phosphonium ionic liquids, demonstrating the potential of tailored ionic liquids as a reaction medium for the Mizoroki–Heck reaction.

Formation of two isomers in the replacement reactions of bay area dibromine atoms in perylene diimides

Three reaction mechanisms were reported in the replacement reaction of bay area dibromine atoms in perylene diimide derivatives in previous studies. However, the effect of the reaction solvents and intermediate compound (perylene diimide radical anion) on the reaction mechanisms and product structure had not been reported. Here, we report the role of the reaction solvents and the perylene diimide radical anion in replacement reactions of bay area dibromine atoms of perylene diimide. Two isomers in the replacement reactions of bay area dibromine atoms in perylene diimides were found when using proton solvents (such as ethanol), and presenting the about 41% 1-bromo-7- ethoxy substituted perylene diimide derivative changed into 1,6- diethoxy substutent perylene diimide derivative in double substituted reaction. In polar non-proton solvents, inorganic base (K2CO3) can induce dibromo perylene diimide to form its radical anion. Further, the substitution reactions is a SN1 mechanism in proton solvents, and the substitution reactions is belong to a SN2 and SRN1 mechanism in polar non-proton solvents.

METHODS FOR EXTRACTION AND ISOLATION OF AGATHISFLAVONE FROM Poincianella pyramidalis

Agathisflavone is a natural biflavone with restricted occurrence in plants. This biflavone presents several biological activities and can be important to developing new drugs. Obtaining such a molecule on a large scale for in vivo tests is a challenge. To date, there are no reports regarding its synthesis; thus, it is important to improve and develop methods for the purification of this bioactive compound from natural sources. Previous studies indicated that the leaves of Poincianella pyramidalis (Leguminosae) had agathisflavone predominantly. However, obtaining this compound requires some steps of chromatographic procedures and extraction with organic solvents. This paper compares four procedures for the purification of agathisflavone from its leaves, two by traditional chromatographic techniques and by complexation with inorganic bases. The purification in the automatic flash chromatography in two steps provides a high-yield extraction; the two procedures using alkaline extraction and the traditional method reduced to three steps provided the compound with similar yields. The biflavone was identified by TLC, and HPLC analysis showed that it was isolated with > 99% of purity. Thus, the applied methodologies provided the purification of this compound employing less volume of solvents, the number of chromatographic column procedures, and time-consuming, with increased yields

Fire performance of fly-ash-based geopolymer concrete: Effect of burning temperature on mechanical and microstructural properties

Prolonged exposure of concrete to high temperatures, as in fire occurrences, can cause physio-chemical changes that reduce strength and durability, as well as degradation to the microstructure. Geopolymer has emerged as an alternative binder for concrete that is fire-resistant due to its inorganic base and ceramic-like properties. Notwithstanding the high fire resistance of geopolymer concrete, its application in buildings has to consider potential deficiencies during fire occurrences. The present study evaluates the residual compressive strength and microstructural properties of fly-ash-based geopolymer concrete with exposure to fire at burning temperatures of 500 and 1200 °C relative to OPC-based concrete. Increment in mechanical strength for geopolymer concrete were observed during the exposure to fire at 500 °C due to further geopolymerization but eventually reduced in strength at 1200 °C. The matrix of the geopolymer concrete is denser, hence indicating a higher structural integrity relative to OPC-based concrete, as well a higher thermal stability.

Copper(ii) complexes of quinoline-based ligands for efficient photoredox catalysis of atom transfer radical addition (ATRA) reaction

Cu(ii)·1Q is efficient in ATRA reactions with perhaloalkanes, revealing the role of common additives (AIBN or inorganic base).