Mild Conditions Research Articles

Performance of metakaolin-based geopolymer molecular sieve microspheres on dynamic recovery of Cu (II)

This study reports the in-situ transformation of geopolymers into molecular sieve using a method with mild conditions. The application of geopolymer zeolites for dynamic adsorption in continuous fixed beds has been less studied, and the application of adsorbents after adsorption has been less studied. Different metakaolin-based geopolymer molecular sieve microspheres (NaA-MSM, SOD-MSM) were prepared by in-situ conversion of metakaolin as raw material and NaOH as an alkali activator. The continuous fixed-bed adsorption performance was evaluated by varying the influent flow rate, initial metal concentration, and adsorbent dosage. The maximum adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 698.14 and 523.84 mg·g−1, respectively. In the simulated solution of real lake water, the adsorption capacities of NaA-MSM and SOD-MSM for Cu (II) were 202.94 and 154.97 mg·g−1, respectively. The results show that the synthesized molecular sieve is an excellent adsorbent for Cu (II)-containing wastewater, and the application design of recycling heavy metals in wastewater by adsorption technology and degrading dyes has been successfully constructed.

Photocatalyzed Acylmethylation/Cyclization of Unactivated Alkenes with Sulfoxonium Ylides towards Acylmethylated Polycyclic Quinazolinones

AbstractThe synthesis of acylmethylatated pyrrolo‐quinazolinones was developed via photo‐induced cascade radical addition/cyclization of N‐(but‐3‐enyl)quinazolin‐4(3H)‐ones with sulfoxonium ylides using 4CzIPN as the photocatalyst. This approach was also suitable for the construction of acylmethylatated piperidino‐quinazolinones. This protocol features with mild conditions, convenient operation, broad substrate scope and good functional group compatibility.

Room-Temperature Cascade Electrophilic Addition/Cyclization/Oxidation Reactions: Divergent Selective Synthesis of Brominated 2H-Chromenes, 2H-Chromen-2-ols and 2H-Chromen-2-ones.

The room temperature metal-free cascade electrophilic addition/cyclization/oxidation reactions of (3-phenoxyprop-1-yn-1-yl)benzenes to divergently synthesize various brominated benzopyran derivatives (3-bromo-2H-chromenes, 3-bromo-2H-chromen-2-ols and 3-bromo coumarins) by tuning the amount of Br2 and H2O have been developed. The method exhibited high selectivity, mild reaction conditions, broad substrate scope, high efficiency, and the applicability for derivatization of the brominated products. The importance of the strategies provides a great advantage for selective synthesis of brominated benzopyran derivatives.

Electrochemically‐Enabled Construction of N‐Acyl Iminophosphoranes

AbstractN‐acyl iminophosphoranes have shown significant potentials in various areas. This paper presents two electrochemical strategies for the successful construction of a series of substituted N‐acyl iminophosphoranes using electrochemical activation of hydroxylamines or dioxazolones to generate unprotected amide radicals and radical anions. The simple undivided cell with inexpensive electrode setups (graphite felts, carbon rods, and copper sheets) provides excellent substrates tolerance under mild conditions. This simple electrochemical construction of N‐acyl iminophosphoranes also has good scalability, practicability and extensibility. Furthermore, synthetic transformations of the N‐acyl iminophosphorane products have demonstrated the application potentials of the P=N bond.

Photoinduced Remote Selective C(sp3)−H Alkylation Mediated by Cesium Formate

AbstractHerein, we developed a photoinduced remote selective C(sp3)−H alkylation of protected amines in the presence of cesium formate. The protected amines were synthesized from commercially available inexpensive 2‐iodo benzoyl chloride. Under mild reaction conditions, the in situ generated aryl radical is converted to α‐amidoalkyl radical via [1,5]‐HAT process, which combines with different Michael acceptors and affords corresponding alkylation products in good yields. Preliminary mechanistic studies revealed that formate anion acts as a source of carbon dioxide radical anion (CO2⋅−) and hydrogen atom donor was directly confirmed by isotope‐labeling studies.

Highly Enantioselective Lewis Acid Catalyzed Conjugate Addition of Imidazo[1,2-a]pyridines to α,β-Unsaturated 2-Acylimidazoles under Mild Conditions.

A highly enantioselective protocol for the conjugate addition of 2-arylimidazo[1,2-a]pyridines and other imidazo derivatives to α,β-unsaturated 2-acylimidazoles is described. The method uses a previously reported chiral-at-metal rhodium catalyst and provides the corresponding adducts in yields of 25-98% with enantioselectivities up to er > 99:1. Additionally, the transformation proceeds under mild conditions using ethanol as the solvent at room temperature.

Intramolecular Hosomi-Sakurai Reaction for the Synthesis of Benzoxasiloles.

A Lewis acid-catalyzed intramolecular Hosomi-Sakurai reaction of o-(allylsilyl)benzaldehyde/ketone has been developed. The reaction proceeds through simultaneous C-Si bond cleavage and C-C bond reconstruction. This protocol provides a rapid approach for the synthesis of allyl-substituted benzoxasiloles under mild conditions.

The effects of climate and climate change on electric vehicle charging demand in Toronto, Canada

Battery electric vehicles (BEVs) influence total and peak electricity demand, but few studies account for climate when studying these effects. This study quantifies BEV charging demand in the Greater Toronto and Hamilton Area using a detailed trip level approach, accounting for the effect of present and future temperatures on BEV energy consumption. The impact of temperature on charging demand was largest in winter. In 2019, charging demand increases by 52% on an average January day, and up to 82% on extreme days (relative to mild weather conditions). At 30% penetration, BEVs increase peak demand on January’s coldest day by 600–3600 MW (3%–5%), of which 300–700 MW is driven by temperature, depending on the charging scenario. Climate change introduces small changes, increasing summer and decreasing winter charging demand. These results highlight the importance of adjusting for regional climate variation and temperature extremes when analyzing the impact of BEVs on the grid.

Synthesis of Functionalized 4-Hydroxy Carbazoles and Carbazole Alkaloids via Ring Expansion of Indole Cyclopentanone.

The exploration of a ring expansion reaction from indole cyclopentanone to generate a range of diversely functionalized 4-hydroxyl carbazole frameworks, representing the core structure of numerous carbazole alkaloids, has been conducted under mild reaction conditions. This approach exhibits broad functional group tolerance and moderate to good yields. The practical applicability of this strategy has been demonstrated through the concise syntheses of carbazomycins A, D, and G.

Synthesis of Multisubstituted 2,3-Allenamides via Palladium-Catalyzed Carbonylation of Propargylic Esters.

2,3-Allenamides are an important class of unsaturated group-substituted carbonyl compounds. A palladium-catalyzed aminocarbonylation of propargyl acetates with amines for the synthesized tri-/tetrasubstituted 2,3-allenamides has been developed. A broad range of tri-/tetrasubstituted 2,3-allenamides have been prepared from propargyl acetates in good to excellent yields. The reaction featured mild reaction conditions and good functional group tolerance. The applicability of this methodology was further highlighted by the late-stage modification of several natural products and pharmaceuticals.

Progress in Photocatalyzed Trifluoromethylthiolation and Trifluoromethylselenolation Reactions

AbstractThe trifluoromethylthio (SCF3) and trifluoromethylselanyl (SeCF3) groups possess high electron-withdrawing ability, excellent lipophilicity, good stability, and bioavailability, and they are promising structural motifs in drug design and development. Photoredox catalysis has clear benefits; it is a mild and sustainable methodology for the modification of chemical structures that enables a variety of chemical reactions that are unattainable using classical ionic chemistry. This review focuses on light-initiated trifluoromethylthiolation and trifluoromethylselenolation reactions with diverse SCF3 and SeCF3 reagents. Representative transformations either using photocatalysts or through EDA complexes, as well as possible reaction mechanisms, are all discussed in this article.1 Introduction2 Photocatalyzed Trifluoromethylthiolation2.1 Photocatalyzed Trifluoromethylthiolation with MSCF3 (M = H, [Me4N], Ag)2.2 Photocatalyzed Trifluoromethylthiolation with XSCF3 (X = Cl, CF3S)2.3 Photocatalyzed Trifluoromethylthiolation with ArSO2SCF3 2.4 Photocatalyzed Trifluoromethylthiolation with N–SCF3 Reagents2.5 Photocatalyzed Trifluoromethylthiolation with Other Reagents3 Photocatalyzed Trifluoromethylselenolation3.1 Photocatalyzed Trifluoromethylselenolation with [Me4N][SeCF3]3.2 Photocatalyzed Trifluoromethylselenolation with ArSO2SeCF3 4 Summary

Palladium-Catalyzed Cyanations of Aryl Imidazolylsulfonates with K4[Fe(CN)6]: A Pragmatic Approach to Benzonitriles from Phenols

AbstractA general Pd-catalyzed approach for the conversion of phenols into benzonitriles via aryl imidazolylsulfonates with a non-toxic cyanide source, potassium ferrocyanide, has been developed. Salient features of this method include low palladium precatalyst loadings (as low as 1.0 mol% total Pd), mild reaction conditions, and environmentally benign by-products compared to other (pseudo)halide aryl electrophiles. The initial scope of the reaction on a range of phenolic precursors is demonstrated including a one-pot, two-step approach to convert phenols directly into benzonitriles.

Eco-evolutionary dynamics of cooperative antimicrobial resistance in a population of fluctuating volume and size

Antimicrobial resistance to drugs (AMR), a global threat to human and animal health, is often regarded as resulting from cooperative behaviour. Moreover, microbes generally evolve in volatile environments that, together with demographic fluctuations (birth and death events), drastically alter population size and strain survival. Motivated by the need to better understand the evolution of AMR, we study a population of time-varying size consisting of two competing strains, one drug-resistant and one drug-sensitive, subject to demographic and environmental variability. This is modelled by a binary carrying capacity randomly switching between mild and harsh environmental conditions, and driving the fluctuating volume (total amount of nutrients and antimicrobials at fixed concentration), and thus the size of the community (number of resistant and sensitive cells). We assume that AMR is a shared public good when the concentration of resistant cells exceeds a fixed concentration cooperation threshold, above which the sensitive strain has a growth advantage, whereas resistant cells dominate below it. Using computational means, and devising an analytical treatment (built on suitable quenched and annealed averaging procedures), we fully characterise the influence of fluctuations on the eco-evolutionary dynamics of AMR, and notably obtain specific strain fixation and long-lasting coexistence probabilities as a function of the environmental variation rate and cooperation threshold. We find that microbial strains tend to coexistence, but demographic fluctuations eventually lead to the extinction of resistant or sensitive cells for small or large values of the concentration cooperation threshold, respectively. This also holds for dynamic environments, whose specific properties determine the extinction timescale.

Esterification and Etherification of Aliphatic Alcohols Enabled by Catalytic Strain-Release of Donor-Acceptor Cyclopropane.

We herein disclose a highly efficient protocol for the esterification and etherification of alcohols, leveraging a Sc(OTf)3-catalyzed ring-strain release event in the meticulously designed, chromatographically stable mixed anhydrides or benzyl esters that incorporate an intramolecular donor-acceptor cyclopropane (DAC). This versatile method facilitates the straightforward functionalization of sugar, terpene, and steroid alcohols under mild acidic conditions, as showcased by the single-catalyst-driven, dual protection of sugar diol.

Macrocrowding of Polyethylene Glycol Facilitates the Formation of Polydopamine Nanoparticles and Derivatives via Depletion Stabilization

AbstractMussel‐inspired polydopamine nanoparticles (PDA NPs) show promise in biosensing, drug delivery, and energy storage. However, it is still difficult to obtain monodispersed PDA NPs and metal‐containing PDA NPs in mild aqueous conditions. Herein, we report a facile strategy to modulate the growth and formation of PDA NPs in a macrocrowding condition using inert polymers as crowders. Our results show that both high concentrations and molecular weights are important for polymer‐enabled particle stabilization. Importantly, we demonstrate that only polyethylene glycol (PEG) with a weak interaction with PDA could facilitate NPs formation. Lastly, we show that this strategy could be extended to metal‐containing PDA derivatives, and enzyme‐encapsulated PDA NPs. Overall, our findings offer a simple and effective approach for producing uniform biocompatible nanomaterials, while also shedding light on the role of depletion forces in nanoparticle stabilization.

Efficient Glucose Isomerization to Fructose using Photoregenerable MgSnO3 Catalyst with Cooperative Acid-Base Sites.

The isomerization of glucose to fructose plays a crucial role in the food industry and the production biomass-derived chemicals in biorefineries. However, the catalyst used in this reaction suffers from low selectivity and catalyst deactivation due to carbon or by-product deposition. In this study, MgSnO3 catalyst, synthesized via a facile two-step process involving hydrothermal treatment and calcination, was used for glucose isomerization to fructose. The catalyst demonstrated outstanding catalytic performance, achieving a fructose equilibrium yield of 29.8% with a selectivity exceeding 90% under mild conditions owing to its acid-base interaction. Notably, spent catalysts can be regenerated by photoirradiation to remove surface carbon, thereby avoiding the changes in properties and subsequent loss of activity associated with conventional calcination regeneration method. This novel approach eliminates the energy consumption and potential structural aggregation associated with traditional calcination regeneration methods. The acid-base active sites of the catalyst, along with their corresponding catalytic reaction mechanism and photoregeneration mechanism were investigated. This study presents a demonstration of the comprehensive utilization of catalytic material properties, i.e., acid-base and photocatalytic functionalities, for the development of a green and sustainable biomass thermochemical conversion system.

2+1] Cycloadditions Modulate the Hydrophobicity of Ni-N4 Single-Atom Catalysts for Efficient CO2 Electroreduction.

Microenvironment regulation of M-N4 single-atom catalysts (SACs) is a promising way to tune their catalytic properties toward the electrochemical CO2 reduction reaction. However, strategies that can effectively introduce functional groups around the M-N4 sites through strong covalent bonding and under mild reaction conditions are highly desired. Taking the hydrophilic Ni-N4 SAC as a representative, we report herein a [2+1] cycloaddition reaction between Ni-N4 and in-situ generated difluorocarbene (F2C:), and enable the surface fluorocarbonation of Ni-N4, resulting in the formation of a super-hydrophobic Ni-N4-CF2 catalyst. Meanwhile, the mild reaction conditions allow Ni-N4-CF2 to inherit both the electronic and structural configuration of the Ni-N4 sites from Ni-N4. Enhanced electrochemical CO2-to-CO Faradaic efficiency above 98% is achieved in a wide operating potential window from -0.7 V to -1.3 V over Ni-N4-CF2. In-situ spectroelectrochemical studies reveal that a highly hydrophobic microenvironment formed by the -CF2- group repels asymmetric H-bonded water at the electrified interface, inhibiting the hydrogen evolution reaction and promoting CO production. This work highlights the advantages of [2+1] cycloaddition reactions on the covalent modification of N-doped carbon-supported catalysts.

Pyridinium‐Yne Click Polymerization: A Facile Strategy toward Functional Poly(Vinylpyridinium Salt)s with Multidrug‐Resistant Bacteria Killing Ability

AbstractPolymeric materials with antibacterial properties hold great promise for combating multidrug‐resistant bacteria, which pose a significant threat to public health. However, the synthesis of most antibacterial polymers typically involves complicated and time‐consuming procedures. In this study, we demonstrate a simple and efficient strategy for synthesizing functional poly(vinylpyridinium salt)s via pyridinium‐yne click polymerization. This click polymerization could proceed with high atom economy under mild conditions without any external catalyst, yielding soluble and thermally stable poly(vinylpyridinium salt)s with satisfactory molecular weights and well‐defined structures in excellent yields. Additionally, the incorporation of luminescent units such as fluorene, tetraphenylethylene, and triphenylamine into the polymer backbone confers excellent aggregation‐enhanced emission properties upon the resulting polymers, rendering them suitable for bacterial staining. Moreover, the existence of pyridinium salt imparts intrinsic antibacterial activity against multidrug‐resistant bacteria to the polymers, enabling them to effectively inhibit wound bacterial infection and significantly expedite the healing process. This work not only provides an efficient method to prepare antibacterial polymers, but also opens up the possibility of various applications of polymers in healthcare and other antibacterial fields.

Modelling Photocatalytic N2 Reduction: Where We Stand and Where We Are Going.

Artificial ammonia synthesis via the Haber-Bosch process is environmentally problematic due to the high energy consumption and corresponding CO2 emissions, produced during the reaction and before hand in hydrogen production upon methane steam reforming. Photocatalytic nitrogen fixation as a greener alternative to the conventional Haber-Bosch process enables us to perform nitrogen reduction reaction (NRR) under mild conditions, harnessing light as the energy source. Herein, we systematically review first-principles calculations used to determine the electronic/optical properties of photocatalysts, N2 adsorption and to expound possible NRR mechanisms. The most commonly studied photocatalysts for nitrogen fixation are usually modified with dopants, defects, co-catalysts and Z-scheme heterojunctions to prevent charge carrier recombination, improve charge separation efficiency and adjust a band gap to for utilizing a broader light spectrum. Most studies at the atomistic level of modeling are grounded upon DFT calculations, wholly foregoing excitation effects paramount in photocatalysis. Hence, there is a dire need to consider methods beyond DFT to study the excited state properties more accurately. Furthermore, a few studies have been examined, which include higher level kinetics and macroscale simulations. Ultimately, we show there is still ample room for improvement with regard to first principles calculations and their integration in multiscale models.

Pyridinium-Yne Click Polymerization: A Facile Strategy toward Functional Poly(Vinylpyridinium Salt)s with Multidrug-Resistant Bacteria Killing Ability.

Polymeric materials with antibacterial properties hold great promise for combating multidrug-resistant bacteria, which pose a significant threat to public health. However, the synthesis of most antibacterial polymers typically involves complicated and time-consuming procedures. In this study, we demonstrate a simple and efficient strategy for synthesizing functional poly(vinylpyridinium salt)s via pyridinium-yne click polymerization. This click polymerization could proceed with high atom economy under mild conditions without any external catalyst, yielding soluble and thermally stable poly(vinylpyridinium salt)s with satisfactory molecular weights and well-defined structures in excellent yields. Additionally, the incorporation of luminescent units such as fluorene, tetraphenylethylene, and triphenylamine into the polymer backbone confers excellent aggregation-enhanced emission properties upon the resulting polymers, rendering them suitable for bacterial staining. Moreover, the existence of pyridinium salt imparts intrinsic antibacterial activity against multidrug-resistant bacteria to the polymers, enabling them to effectively inhibit wound bacterial infection and significantly expedite the healing process. This work not only provides an efficient method to prepare antibacterial polymers, but also opens up the possibility of various applications of polymers in healthcare and other antibacterial fields.