Sodium Triethylborohydride-Catalyzed Controlled Reduction of Unactivated Amides to Secondary or Tertiary Amines

Building hydrophobic substrate pocket to boost activity of laccase-like nanozyme through acetonitrile-mediated strategy

Nanozymes, as promising alternatives to natural enzymes, offer several advantages with biocatalytic functions but remain inferior in catalytic activity. It is crucial to focus on factors that affect the enzymatic activity of nanozymes and develop strategies to make them more competitive with natural enzymes. Herein, CuV2O5 nanorods are confirmed to own the intrinsic laccase-like activity, and an acetonitrile (MeCN)-mediated strategy is proposed for reaction acceleration by mimicking the enzymatic substrate pocket. In the presence of MeCN, the interaction between substrates and nanozymes gets efficiently promoted by the bridging function of cyano-group, where the utilization of Cu active sites is greatly improved due to the condensed hydrophobic substrate layers formed in the vicinity of CuV2O5 nanorods by the solvent effect of MeCN. Theoretical calculations also disclose that the addition of MeCN endows 2,4-dichlorophenol (2,4-DP) with a lower free-energy barrier in adsorption and activation on the surface of CuV2O5 nanozyme. Benefiting from the improved activity, a sensitive colorimetric sensing platform for 2,4-DP is constructed with the limit of detection as low as 0.48 μM. Our finding lays a theoretical foundation for achieving high-performance catalytical activity of the nanozymes based on the modulation of the reaction microenvironment, effectively alleviating the complex engineering process of nanozymes.

Synthesis and Anticancer Activity of 3,4-Diaryl-1,2-dihydro- and 1,2,3,4-Tetrahydroquinolines

Tetrahydroquinolines are key structures in a variety of natural products with diverse pharmacological utilities and other applications. A series of 3,4-diaryl-5,7-dimethoxy-1,2,3,4-tetrahydroquinolines were synthesized in good yield by reacting 3-aryl-5,7-dimethoxy-2,3-dihydroquinolin-4-ones with different Grignard reagents followed by the dehydration of the intermediate phenolic compounds. Subsequent reduction and deprotection were carried out to achieve the desired tetrahydroquinolone moiety. The lead compound 3c showed low micromolar inhibition of various cancer cell lines. Demethylation under different reaction conditions was also investigated to afford the corresponding monohydroxy analogues.

Hydroboration and hydrosilylation of alkenes catalyzed by an unsymmetrical magnesium methyl complex

The hydroboration and hydrosilylation of alkenes catalyzed by the unsymmetrical β-diketiminate magnesium methyl complex [(DippXylNacnac)MgMe (THF)] (1) have been reported. When complex 1 was employed as a highly efficient catalyst in the hydroboration of various alkenes with HBpin, only the anti-Markovnikov hydroboration products were obtained in high yields and with high regioselectivities under mild reaction conditions (60 °C). To our surprise, it showed different regioselectivities in the hydrosilylation of a range of alkenes with PhSiH3. Aromatic alkene substrates afforded the corresponding branched Markovnikov hydrosilylation products in high yields and with high regioselectivities; conversely, aliphatic alkenes produced the linear anti-Markovnikov products in moderate yields. This is completely consistent with the corresponding density functional theory (DFT) calculations. In addition, the practical utility was demonstrated via scale-up reactions of boronate esters and a preliminary plausible mechanism of hydroboration and hydrosilylation have been investigated as well.

Imine-Decorated Copper-Based Metal-Organic Framework for the Photodegradation of Methylene Blue

A low cost imine-decorated linker, 4,4'-(hydrazine-1,2-diylidenedimethylylidene)dibenzoic acid was utilized for the preparation of copper-based metal-organic framework (MOF) denoted as Cu-L via a solvothermal technique. The synthesized MOF material has been fully characterized by different analytical techniques such as Fourier-transform infrared (FT-IR) spectroscopy, powder X-Ray diffraction (PXRD), scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDX), nitrogen adsorption-desorption isotherm analysis, and thermogravimetric analysis (TGA). It has been found that the coordination of Cu2+ with L considerably reduced the band gap of the L of nearly about 1 eV, which is approximately 26% decline in total. Notably, a narrow band gap of the photocatalyst is an essential requirement for the proficient photodegradation of organic contaminants. An excellent optical properties and narrow band gap of (2.8 eV) of Cu-L ensure their suitability as a photocatalyst for the degradation of methylene blue (MB) dye. In the presence of Cu-L photocatalyst, 84.22% degradation of MB dye was observed after 150 min under sunlight exposure. It is the first time that imine-functionalized MOF was utilized for the degradation of MB dye under sunlight irradiation. For understanding the photodegradation of MB dye by the Cu-L photocatalyst, all the plausible mechanistic studies have been carried out in detail. Both theoretical (with the help of density functional theory (DFT) calculations) as well as experimental studies have been conducted to justify the possible mechanisms for the photodegradation of MB dye by Cu-L. The current work may open a new opportunity to construct a cheap MOF-based photocatalysts for fast degradation of dye contaminants.

3-Chloropropylbis(catecholato)silicate as a Bifunctional Reagent for the One-Pot Synthesis of Tetrahydroquinolines from o-Bromosulfonamides

Bis(catecholato)silicate salts are easily accessible reagents that can be used to install alkyl fragments through photoredox-enabled cross-coupling. These reagents can incorporate various functional groups including pendant alkyl halides. A halogenated organosilicate reagent was leveraged to develop a one-pot synthesis of tetrahydroquinolines from o-bromosulfonamides, where the bifunctional reagent participates in a nickel/photoredox cross-coupling followed by intramolecular nucleophilic substitution. The functional group tolerance of this cross-coupling strategy allowed for the preparation of a series of substituted tetrahydroquinolines.

DIBAL-H-mediated N-deacetylation of tertiary amides: synthesis of synthetically valuable secondary amines

A rapid DIBAL-H-mediated N-deacetylation of tertiary amides is described under mild conditions, affording synthetically valuable secondary amines in good to excellent yields.

Synthesis, Characterization, and Environmental Applications of Novel Per-Fluorinated Organic Polymers with Azo- and Azomethine-Based Linkers via Nucleophilic Aromatic Substitution

This study reports on the synthesis and characterization of novel perfluorinated organic polymers with azo- and azomethine-based linkers using nucleophilic aromatic substitution. The polymers were synthesized via the incorporation of decafluorobiphenyl and hexafluorobenzene linkers with diphenols in the basic medium. The variation in the linkers allowed the synthesis of polymers with different fluorine and nitrogen contents. The rich fluorine polymers were slightly soluble in THF and have shown molecular weights ranging from 4886 to 11,948 g/mol. All polymers exhibit thermal stability in the range of 350-500 °C, which can be attributed to their structural geometry, elemental contents, branching, and cross-linking. For instance, the cross-linked polymers with high nitrogen content, DAB-Z-1h and DAB-Z-1O, are more stable than azomethine-based polymers. The cross-linking was characterized by porosity measurements. The azo-based polymer exhibited the highest surface area of 770 m2/g with a pore volume of 0.35 cm3/g, while the open-chain azomethine-based polymer revealed the lowest surface area of 285 m2/g with a pore volume of 0.0872 cm3/g. Porous structures with varied hydrophobicities were investigated as adsorbents for separating water-benzene and water-phenol mixtures and selectively binding methane/carbon dioxide gases from the air. The most hydrophobic polymers containing the decafluorbiphenyl linker were suitable for benzene separation, while the best methane uptake values were 6.14 and 3.46 mg/g for DAB-Z-1O and DAB-A-1O, respectively. On the other hand, DAB-Z-1h, with the highest surface area and being rich in nitrogen sites, has recorded the highest CO2 uptake at 298 K (17.25 mg/g).

The Competition between 4-Nitrophenol Reduction and BH4- Hydrolysis on Metal Nanoparticle Catalysts

Assessing competitive environmental catalytic reduction processes via NaBH4 is essential, as BH4- is both an energy carrier (as H2) and a reducing agent. A comprehensive catalytic study of the competition between the borohydride hydrolysis reaction (BHR, releasing H2) and 4-nitrophenol reduction via BH4- on M0- and M/M' (alloy)-nanoparticle catalysts is reported. The results reveal an inverse correlation between the catalytic efficiency for BH4- hydrolysis and 4-nitrophenol reduction, indicating that catalysts performing well in one process exhibit lower activity in the other. Plausible catalytic mechanisms are discussed, focusing on the impact of reaction products such as 4-aminophenol and borate on the rate and yield of BH4- hydrolysis. The investigated catalysts were Ag0, Au0, Pt0, and Ag/Pt-alloy nanoparticles synthesized without any added stabilizer. Notably, the observed rate constants for the 4-nitrophenol reduction on Ag0, Ag-Pt (9:1), and Au0 are significantly higher than the corresponding rate constants for BH4- hydrolysis, suggesting that most reductions do not proceed through surface-adsorbed hydrogen atoms, as observed for Pt0 nanoparticles. This research emphasizes the conflicting nature of BH4- hydrolysis and reduction processes, provides insights for designing improved catalysts for competitive reactions, and sheds light on the catalyst properties required for each specific process.

Synthesis, Computational Studies, Antioxidant and Anti-Inflammatory Bio-Evaluation of 2,5-Disubstituted-1,3,4-Oxadiazole Derivatives

The 1,3,4-oxadiazole derivatives Ox-6a-f have been synthesized by incorporating flurbiprofen moiety with the aim to explore the potential of target molecules to decrease the oxidative stress. The title compounds Ox-6a-f were prepared by simple reactions in which a flurbiprofen -COOH group was esterified with methanol in an acid-catalyzed medium, which was then reacted with hydrazine to afford the corresponding hydrazide. The acid hydrazide was then cyclized into 1,3,4-oxadiazole-2-thiol by reacting with CS₂ in the presence of KOH. The title compounds Ox-6a-f were synthesized by the reaction of an -SH group with various alkyl/aryl chlorides, which involves an S-alkylation reaction. The structures of the synthesized Ox-6a-f derivatives were ascertained by spectroscopic data. The in silico molecular docking was performed against target proteins cyclooxygenase-2 COX-2 (PDBID 5KIR) and cyclooxygenase-1 COX-1 (PDBID 6Y3C) to determine the binding affinity of the synthesized compounds with these structures. It has been inferred that most of the synthesized compounds bind well with an active binding site of 5KIR compared to 6Y3C, and especially compound Ox-6f showed excellent binding affinity (7.70 kcal/mol) among all synthesized compounds Ox-6a-f. The molecular dynamic (MD) simulation has also been performed to check the stability of docking complexes of ligands with COX-2 by determining their root mean square deviation and root mean square fluctuation. Little fluctuation was observed in case of Ox-6f, which forms the most stable complex with COX-2. The comprehensive antioxidant potential of the synthesized compounds has been evaluated by determining their free radical scavenging activity, including DPPH, OH, nitric oxide (NO), and iron chelation assay. The derivative Ox-6f showed promising results with 80.23% radical scavenging potential at a dose of 100 µg/mL while ascorbic acid exhibited 87.72% inhibition at the same dose. The anti-inflammatory activity of the final products has also been performed, and inflammatory markers were assayed, such as a thiobarbituric acid-reducing substance, nitric oxide, interleukin-6 (IL-6), and COX-2. The derivatives Ox-6d and Ox-6f displayed higher anti-inflammatory activity, exhibiting 70.56% and 74.16% activity, respectively. The results were compared with standard ibuprofen, which showed 84.31% activity at the same dose, 200 µg/mL. The anti-inflammatory potential has been performed by following the carrageen-induced hind paw edema model, and results showed that derivative Ox-6f exhibited 79.83% reduction in edema volume compared to standard ibuprofen, which reduced 84.31% edema volume. As dry lab and wet lab results confirm each other, it has been deduced that derivative Ox-6f may serve as the lead structure to design potent compounds to address oxidative stress.

Photocatalysis in Water-Soluble Supramolecular Metal Organic Complex

As an emerging subset of organic complexes, metal complexes have garnered considerable attention owing to their outstanding structures, properties, and applications. In this content, metal-organic cages (MOCs) with defined shapes and sizes provide internal spaces to isolate water for guest molecules, which can be selectively captured, isolated, and released to achieve control over chemical reactions. Complex supramolecules are constructed by simulating the self-assembly behavior of the molecules or structures in nature. For this purpose, massive amounts of cavity-containing supramolecules, such as metal-organic cages (MOCs), have been extensively explored for a large variety of reactions with a high degree of reactivity and selectivity. Because sunlight and water are necessary for the process of photosynthesis, water-soluble metal-organic cages (WSMOCs) are ideal platforms for photo-responsive stimulation and photo-mediated transformation by simulating photosynthesis due to their defined sizes, shapes, and high modularization of metal centers and ligands. Therefore, the design and synthesis of WSMOCs with uncommon geometries embedded with functional building units is of immense importance for artificial photo-responsive stimulation and photo-mediated transformation. In this review, we introduce the general synthetic strategies of WSMOCs and their applications in this sparking field.

Efficient Synthesis of Imine-Carboxylic Acid Functionalized Compounds: Single Crystal, Hirshfeld Surface and Quantum Chemical Exploration

Two aminobenzoic acid based crystalline imines (HMBA and DHBA) were synthesized through a condensation reaction of 4-aminobenzoic acid and substituted benzaldehydes. Single-crystal X-ray diffraction was employed for the determination of structures of prepared Schiff bases. The stability of super molecular structures of both molecules was achieved by intramolecular H-bonding accompanied by strong, as well as comparatively weak, intermolecular attractive forces. The comparative analysis of the non-covalent forces in HMBA and DHBA was performed by Hirshfeld surface analysis and an interaction energy study between the molecular pairs. Along with the synthesis, quantum chemical calculations were also accomplished at M06/6-311G (d, p) functional of density functional theory (DFT). The frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), natural bond orbitals (NBOs), global reactivity parameters (GRPs) and natural population (NPA) analyses were also carried out. The findings of FMOs found that Egap for HMBA was examined to be smaller (3.477 eV) than that of DHBA (3.7933 eV), which indicated a greater charge transference rate in HMBA. Further, the NBO analysis showed the efficient intramolecular charge transfer (ICT), as studied by Hirshfeld surface analysis.

Ligand Modulation on the Various Structures of Three Zinc(II)-Based Coordination Polymers for Antibiotics Degradation

The efficient removal of organic contaminants from wastewater is, nowadays, a prominent area of study due to its biological as well as environmental significance. Antibiotics are now found in wastewater because of their high use, which has become a source of aquatic pollution. These antibiotics have dangerous implications for people’s health. Hence, effective pharmaceutical removal from wastewater and contaminated water bodies, especially the removal of antibiotics, is of major interest to global research organizations. This is why it is necessary to investigate this class of toxic material in wastewater discharge. We synthesized three different coordination polymers (CPs) in the presence of various assistant carboxylate linkers, namely, [Zn(Hbtc)(dip)]n (1), [Zn4(1,2-bdc)4(dip)4]n (2), and [Zn(1,4-bdc)(dip)]n (3) (3,5-di(1H-imidazol-1-yl)pyridine = dip, 1,3,5-benzenetricarboxylic acid = H3btc, 1,2-benzenedicarboxylic acid = 1,2-H2bdc, and 1,4-benzendicarboxylic acid = 1,4-bdc). These CPs were characterized by using different techniques, including single-crystal X-ray diffraction. The structural studies demonstrated that in 2, there are four Zn(II) centers and both centers are in different coordination environments (Zn2 has distorted tetrahedral geometry, whereas Zn1, Zn3, and Zn4 have square pyramidal geometry). Hirshfeld surfaces analysis revealed that different types of intermolecular interactions (C⋯C, H⋯C, H⋯H, O⋯C, N⋯H, and O⋯H) are present in the synthesized CPs. We examined the different antibiotics, such as metronidazole (MDZ), nitrofurazone (NFZ), dimetridazole (DTZ), sulfasalazine(SLA), and oxytetracycline (OXY), degradation behaviors of the synthesized CPs, which showed remarkable degradation efficiency. 1 showed photocatalytic behavior toward the NFZ antibiotic in an aqueous media. This study also showed that these catalysts are stable and reusable under mild conditions.

Effects of Different Lengths of Oligo (Ethylene Glycol) Side Chains on the Electrochromic and Photovoltaic Properties of Benzothiadiazole-Based Donor-Acceptor Conjugated Polymers

In recent years, donor-acceptor (D-A)-type conjugated polymers have been widely used in the field of organic solar cells (OSCs) and electrochromism (EC). Considering the poor solubility of D-A conjugated polymers, the solvents used in material processing and related device preparation are mostly toxic halogenated solvents, which have become the biggest obstacle to the future commercial process of the OSC and EC field. Herein, we designed and synthesized three novel D-A conjugated polymers, PBDT1-DTBF, PBDT2-DTBF, and PBDT3-DTBF, by introducing polar oligo (ethylene glycol) (OEG) side chains of different lengths in the donor unit benzodithiophene (BDT) as side chain modification. Studies on solubility, optics, electrochemical, photovoltaic and electrochromic properties are conducted, and the influence of the introduction of OEG side chains on its basic properties is also discussed. Studies on solubility and electrochromic properties show unusual trends that need further research. However, since PBDT-DTBF-class polymers and acceptor IT-4F failed to form proper morphology under the low-boiling point solvent THF solvent processing, the photovoltaic performance of prepared devices is not ideal. However, films with THF as processing solvent showed relatively desirable electrochromic properties and films cast from THF display higher CE than CB as the solvent. Therefore, this class of polymers has application feasibility for green solvent processing in the OSC and EC fields. The research provides an idea for the design of green solvent-processable polymer solar cell materials in the future and a meaningful exploration of the application of green solvents in the field of electrochromism.

Visible-Light-Promoted Dual Photoredox/Nickel-Catalyzed Chemoselective Reduction of Secondary and Tertiary Amides with Hydrosilanes in the Presence of an Ester

We report a one-step procedure to selectively reduce secondary and tert-amides to their corresponding amine derivatives in the presence of an ester. This was achieved via the synergistic combination of a photoredox, a nickel catalytic system, and phenyl silane as a reductant in the presence of blue light-emitting diode light (455 nm) at room temperature. Further, this mild light-promoted dual metallaphotoredox catalytic system was also successful in selectively reducing a lactam to the cyclic amines, without affecting the ester moiety present in the molecules.

Recent advances in the electrochemical applications of Ni-based metal organic frameworks (Ni-MOFs) and their derivatives

Nickel-based metal-organic skeletal materials (Ni-MOFs) are a new class of inorganic materials that have aroused attention of investigators during past couple of years. They offer advantages such as high specific surface area, structural diversity, tunable framework etc. This assorted class of materials exhibited catalytic activity and electrochemical properties and display wide range of applications in the fields of electrochemical sensing, electrical energy storage and electrocatalysis. In this context, the presented review focuses on strategies to improve the electrochemical performance and stability of Ni-MOFs through the optimization of synthesis conditions, the construction of composite materials, and the preparation of derivatives of precursors. The review also presents the applications of Ni-MOFs and their derivatives as electrochemical sensors, energy storage devices, and electrocatalysts. In addition, the challenges and further electrochemical development prospects of Ni-MOFs have been discussed.

Recent Advances of Silver-Based Coordination Polymers on Antibacterial Applications

With the continuous evolution of bacteria and the constant use of traditional antibiotics, the emergence of drug-resistant bacteria and super viruses has attracted worldwide attention. Antimicrobial therapy has become the most popular and important research field at present. Coordination Polymer (CP) and/or metal-organic framework (MOF) platforms have the advantages of a high biocompatibility, biodegradability, and non-toxicity, have a great antibacterial potential and have been widely used in antibacterial treatment. This paper reviewed the mechanism and antibacterial effect of three typical MOFs (pure Ag-MOFs, hybrid Ag-MOFs, and Ag-containing-polymer @MOFs) in silver-based coordination polymers. At the same time, the existing shortcomings and future views are briefly discussed. The study on the antibacterial efficacy and mechanism of Ag-MOFs can provide a better basis for its clinical application and, meanwhile, open up a novel strategy for the preparation of more advanced Ag-contained materials with antibacterial characteristics.

Reaction of Diisobutylaluminum Borohydride, a Binary Hydride, with Selected Organic Compounds Containing Representative Functional Groups

The binary hydride, diisobutylaluminum borohydride [(iBu)₂AlBH₄], synthesized from diisobutylaluminum hydride (DIBAL) and borane dimethyl sulfide (BMS) has shown great potential in reducing a variety of organic functional groups. This unique binary hydride, (iBu)₂AlBH₄, is readily synthesized, versatile, and simple to use. Aldehydes, ketones, esters, and epoxides are reduced very fast to the corresponding alcohols in essentially quantitative yields. This binary hydride can reduce tertiary amides rapidly to the corresponding amines at 25 °C in an efficient manner. Furthermore, nitriles are converted into the corresponding amines in essentially quantitative yields. These reactions occur under ambient conditions and are completed in an hour or less. The reduction products are isolated through a simple acid-base extraction and without the use of column chromatography. Further investigation showed that (iBu)₂AlBH₄ has the potential to be a selective hydride donor as shown through a series of competitive reactions. Similarities and differences between (iBu)₂AlBH₄, DIBAL, and BMS are discussed.

Combined KOH/BEt3 Catalyst for Selective Deaminative Hydroboration of Aromatic Carboxamides for Construction of Luminophores

The selective catalytic C-N bond cleavage of amides into value-added amine products is a desirable but challenging transformation. Molecules containing iminodibenzyl motifs are prevalent in pharmaceutical molecules and functional materials. Here we established a combined KOH/BEt₃ catalyst for deaminative hydroboration of acyl-iminodibenzyl derivatives, including nonheterocyclic carboxamides, to the corresponding amines. This novel transition-metal-free methodology was also applied to the construction of Clomipramine and luminophores.

Ru-Catalyzed ortho-Selective Diborylation of 2-Arylpyridines toward the Construction of π-Conjugated Functions

A ruthenium catalytic ortho-C-H diborylation of 2-arylpyridine derivatives, including challenging 2-phenoxypyridine functions, using a remarkably low catalyst loading and a low-cost and bench-stable boron source, has been developed. The novel strategy shows high activity with excellent selectivity and may offer a versatile and green alternative to currently employed high loadings of noble metals or extra additives for the selective borylations.

Transition-metal-free catalytic hydroboration reduction of amides to amines

The selective catalytic reduction of amides to value-added amine products is a desirable but challenging transformation.