Reaction Mode Research Articles

A novel route for microplastic mineralization: visible-light-driven heterogeneous photocatalysis and photothermal Fenton-like reaction

A synergic mode of heterogeneous photocatalysis and photothermal Fenton-like reaction for highly efficient microplastic degradation, utilizing α-Fe2O3 nanoflower on TiO2 with a hierarchical structure of inverse opal-like layer/nanotube arrays.

Optimization of ethyl oleate from oleic acid and ethanol with Dean-Stark trap technology by response surface methodology

This work evaluates the optimum condition of the esterification reaction of oleic acid (OA) and ethanol by Dean-Stark trap (DS) and without technology, as well as the effects of the various factors’ interaction on the conversion rate of OA. The influences of OA/ethanol molar ratio, concentration of catalyst, temperature reaction, and time reaction on the conversion rate of OA were investigated. The response surface method (RSM) is combined to optimize the experimental scheme. The results showed that the conversion rate of OA reached the peak of 98.78% when the molar ratio of ethanol/OA was 9:1, the concentration of catalyst was 3%, the temperature reaction was 90 oC, and the reaction time was 10 hours. Compared with the esterification reaction without DS, the conversion rate of OA was 54.96%. FTIR analysis confirmed the changes of a functional group for the response, and GC-MS was for confirmation of the fragmentation mode of the esterification reaction that occurs. The availability of ethyl oleate derived from palm oil, aimed at surfactant production, provides an excellent feedstock to produce surfactants for cosmetic applications.

Catalytically promoted green fuel with hydrogen peroxide: Effect of hypergolic combustion on atomization and flow characteristics using impinging jets

This study explores the jet impingement of a catalytically promoted hypergolic green fuel with High Test Peroxide (HTP). Experimental investigations were conducted using simultaneous high-speed visible, infrared and backlight imaging. Two major aspects were investigated. First, a study exploring the potential of decoupling the combustion phenomenon through the utilization of the fuel without a catalyst as a simulant, enabling a comparative analysis of the atomization process with the authentic hypergolic pair undergoing combustion. A Reynolds versus Weber numbers diagram was obtained for jets with equal momentum in the steady-state flow regime, and a novel breakup mode was observed. The named Reactive Foamy Segregation mode was found as a two phenomenological regime, where a reacting foam exists together with a segregation stream. An analysis of the liquid film velocity formed by impinging jets indicated that the hypergolic pair exhibited significantly lower speeds and corroborates with the introduced breakup mode. Second, an analysis about the transient and steady-state jet flow effects, revealing the existence of separate planes for the reacting foam and plumes, regions with different oxidizer to fuel ratios. This natural effect was intensified by the force generated from the exothermic reaction of hydrogen peroxide decomposition. Notably, the central region of the sheet exhibited the lowest temperature, indicating that the liquid-phase mixture and propellants’ residence time were insufficiently effective in decomposing the peroxide. These findings contribute to a deeper understanding of the complex fluid dynamics involved in catalytically promoted hypergolic reactions applied in liquid rocket engines.

Energy transfer photocatalysis: exciting modes of reactivity.

Excited (triplet) states offer a myriad of attractive synthetic pathways, including cycloadditions, selective homolytic bond cleavages and strain-release chemistry, isomerizations, deracemizations, or the fusion with metal catalysis. Recent years have seen enormous advantages in enabling these reactivity modes through visible-light-mediated triplet-triplet energy transfer catalysis (TTEnT). This tutorial review provides an overview of this emerging strategy for synthesizing sought-after organic motifs in a mild, selective, and sustainable manner. Building on the photophysical foundations of energy transfer, this review also discusses catalyst design, as well as the challenges and opportunities of energy transfer catalysis.

An efficient pyrrolysyl-tRNA synthetase for economical production of MeHis-containing enzymes.

Genetic code expansion has emerged as a powerful tool in enzyme design and engineering, providing new insights into sophisticated catalytic mechanisms and enabling the development of enzymes with new catalytic functions. In this regard, the non-canonical histidine analogue Nδ-methylhistidine (MeHis) has proven especially versatile due to its ability to serve as a metal coordinating ligand or a catalytic nucleophile with a similar mode of reactivity to small molecule catalysts such as 4-dimethylaminopyridine (DMAP). Here we report the development of a highly efficient aminoacyl tRNA synthetase (G1PylRSMIFAF) for encoding MeHis into proteins, by transplanting five known active site mutations from Methanomethylophilus alvus (MaPylRS) into the single domain PylRS from Methanogenic archaeon ISO4-G1. In contrast to the high concentrations of MeHis (5-10 mM) needed with the Ma system, G1PylRSMIFAF can operate efficiently using MeHis concentrations of ∼0.1 mM, allowing more economical production of a range of MeHis-containing enzymes in high titres. Interestingly G1PylRSMIFAF is also a 'polyspecific' aminoacyl tRNA synthetase (aaRS), enabling incorporation of five different non-canonical amino acids (ncAAs) including 3-pyridylalanine and 2-fluorophenylalanine. This study provides an important step towards scalable production of engineered enzymes that contain non-canonical amino acids such as MeHis as key catalytic elements.

N-Benzylhydroxylamine as a novel synthetic block in "C1N1" embedding reaction via α-C(sp3)-H activation strategy.

A novel process using N-benzylhydroxylamine hydrochloride as a "C1N1 synthon" in [2+2+1] cyclization for the construction of 1,2,5-trisubstituted imidazoles has been described for the first time. The key to realizing this process lies in capturing arylamines by in situ generated novel acyl ketonitrone intermediates. Subsequent tautomerization activates the α-C(sp3)-H of N-benzylhydroxylamines, and thus breaks through its inherent reaction mode and achieves N, α-C site-selective cyclization. Furthermore, this method enables scale-up synthesis and late-stage modification of complex molecules.

Theoretical study on the mechanochemical reactivity in Diels-Alder reactions.

Mechanochemical reactions sometimes give different yields from those under solvent conditions, and such mechanochemical reactivities depend on the reactions. This study theoretically elucidates what governs mechanochemical reactivities, taking the Diels-Alder reactions as an example. Applying mechanical force can be regarded as the deformation of molecules, and the deformation in an orthogonal direction to a reaction mode can lower the reaction barrier. Here, we introduce a dimensionless cubic force constant, a mechanochemical reaction constant. It tells us how easily the deformation can lower a reaction barrier and enables us to compare the mechanochemical reactivities of different reactions. The constants correlate positively with the yields of the mechanochemical Diels-Alder reactions.

DFT study on isothiourea-catalyzed C-C bond activation of cyclobutenone: the role of the catalyst and the origin of stereoselectivity.

The organocatalytic C-C bond activation strategy stands out as a new reaction mode for the release of ring strain and expands the scope of organocatalysts. Thus, disclosing the role of the organocatalyst in the C-C bond cleavage process would be of interest. Here, an isothiourea-catalyzed C-C bond activation/cycloaddition reaction of cyclobutenone is selected as a computational model to uncover the role of the catalyst. Based on the calculations, the electrocyclic cleavage of cyclobutenone is calculated to be energetically more favorable than the isothiourea-catalyzed C-C bond cleavage, which is different from the NHC-catalyzed C-C bond activation of cyclobutenone. The computational results show that the isothiourea promotes the reaction by increasing the nucleophilicity of vinyl ketene and thus lowers the energy barrier of the cycloaddition process. Moreover, NCI and AIM analyses are performed to disclose the origin of stereoselectivity.

Recent progress in the catalytic enantioselective reactions of 1,1-diborylalkanes.

Organoboron compounds are environmentally benign, have low toxicity and are versatile reagents that are extensively employed in organic synthesis, especially in the realm of asymmetric synthesis. The last several decades have witnessed a tremendous outburst of asymmetric reactions based on various organoboron compounds. Among them, 1,1-diborylalkanes, which contain two boryl groups at the same sp3-carbon atom, are regarded as some of the most versatile and powerful reagents for their unique structure and unusual reaction mode in organic synthesis. Moreover, owing to the stabilizing effect of the empty p-orbital of the neighboring boron atoms and the inherent good steric-hindrance, 1,1-diborylalkanes often exhibit extraordinary reactivity and stereoselectivity compared to other kinds of organoboron compounds in asymmetric synthesis. Herein, the present highlight summarizes and discusses the recent progress achieved in the catalytic enantioselective reactions of 1,1-diborylalkanes during the past decade.

Research on Demand side Reactive Power Compensation Operating Lease Mode to Adapt to the New Situation of Energy and Electricity

With the development of economy towards green and low-carbon, higher requirements are put forward for energy conservation and efficiency enhancement of power system. To solve the problem of high initial investment and high risk of demand side reactive power compensation, this paper proposes a demand side reactive power compensation operating lease model. Power grid companies and equipment manufacturers combine service providers to undertake different division of labor and jointly serve users. The cost-benefit model of each participant is established, Optimize service fees with the goal of maximizing the net income of both users and service providers, and solved by chaotic cat swarm algorithm, An asymmetric Nash negotiation model is established to allocate service fees between power grid companies and equipment manufacturers. Finally, an example is given to demonstrate the effectiveness of the proposed method.

Study on the characteristics parameters of magnesium dust explosion suppression by various inert gases

Alongside the extensive use of magnesium, dust explosion accidents have become increasingly frequent. Conducting research on suppressing magnesium dust explosions is of great significance for the healthy development of the magnesium industry. In this paper, the effects of four inert gases (CO2, N2, Ar, and He) on the explosion characteristics parameters of magnesium dust clouds with different concentrations were investigated using a closed explosion device. It was observed that at low volume fractions of inert gases in the explosion system, there were no significant differences in their effects on the explosion characteristics parameters and the combustion time of magnesium particles. In situations where there was a high level of oxygen, N2 was more effective than Ar in suppressing explosions. However, when the concentration of magnesium dust cloud was higher and the oxygen content was lower within the hybrids, N2 reacted with magnesium dust that was unable to react with oxygen. As a result, the explosion suppression effect gradually shifted from N2 being better than Ar to Ar being better than N2. Moreover, the differences in the effects of four inert gases on particle combustion time became increasingly prominent. However, in all operating conditions, CO2 demonstrated the most effective suppression of magnesium dust explosions, while He exhibited the least effective suppression effect. Furthermore, by employing a chemical reaction kinetics calculation model, it has been discovered that the content of inert gases significantly affected the combustion time and reaction mode of particle combustion, thereby causing variations in the propagation behavior of magnesium dust cloud flames.

Electrochemistry and Organic Synthesis: New Adventures with Olefin Coupling Reactions and Electrode Surfaces

Electrochemistry has long offered opportunities to explore new modes of reactivity, new approaches for introducing selectivity into synthetic reactions, and new strategies for the synthesis of everything from complex molecules to complex, addressable molecular surfaces. In the talk to be given, two aspects of our efforts along these lines will be detailed. In the first, we will take a look at recent efforts to use anodically-generated reactive intermediates to convert readily available small molecules into functionalized synthetic building blocks and natural product derivatives. Key to these efforts are oxidation reactions that generate reactive radical cation and radical intermediates. In one application, newly available chiral lactols synthesized using methodology developed by the Lin (Cornell) and Miller (Yale) groups are being transformed into C-glycoside and aza-C-glycoside derivatives. The reactions take advantage of oxidation reactions of either enol ether or vinylsulfide groups. The cyclization reactions and the subsequent deprotection strategy needed for converting the cyclization products into a useful synthetic building block will be highlighted. In a second application of an anodic cyclization, the role of thioamides in reactions targeting the chrysosoporazine family of natural products will be discussed. The reactions seek to provide an efficient method for converting lignin derived building blocks into molecules that reduce the efflux of anticancer drugs from cells. Initial cyclization attempts utilizing amide based N-radicals and anodic olefin coupling reactions were not successful. Those reactions consistently led to over-oxidation of the products that contain a highly electron-rich aryl ring. The use of thio-amide derived radicals provides a method to circumvent this problem.In the second topic to be discussed, the question of how one might begin to induce asymmetry into such electrochemical cyclizations will be highlighted. The chemistry focuses on efforts to influence the course of both electrochemical oxidation and reduction reaction and non-redox based transition metal catalyzed reactions with the surface of an electrode.

(Invited) Zn Batteries: Stable Anode and High Energy Cathodes

Our research focuses on a stable aqueous Zn-based battery with long cycling stability, decent energy density, and ultimate safety performance for large-scale energy storage. To achieve this purpose, we did systematic studies on the Zn metal anode, electrolytes, and new cathode development.For the anode side, we developed a few strategies, including pH value manipulation, ion redistribution coating, gradient coating, etc to induce stable stripping and plating of Zn. Moreover, we also found that a Zn initially plated can be much more stable than the one initially stripped during the subsequent deposition. We further utilize this observation to develop a pre-deposited Zn for Zn batteries with improved stability.For the electrolyte, we develop a reverse micelle electrolyte, with it, the Zn anode exhibits balanced merits including strong H2 coevolution suppression, prevention of dendritic and dead Zn, inhibition of corrosion, as well as relatively fast reaction kinetics. In a more extensive context, the new reverse micelle structure of electrolytes is expected to benefit other emerging battery chemistries, where a balance between fast ion transport and sufficient stabilization against side reactions is required.For the cathode with high energy density, we studied the critical research concerns and further potential developments of chalcogen/halogen-based batteries, primarily focusing on the electrochemically active chalcogen/halogen sources, reaction modes, soluble products, and electrolyte adaptability.For the cathode, we use iodine as the fixing agents working in highly concentrated electrolytes to successfully enable reversible Cl-based redox electrode. The interhalogen coordinating chemistry fixes Cl in a configuration of ICl3 -. Furthermore, we simultaneously exploit two redox centers of Cl and I to realize a novel three-electrons transfer electrode, in which the Cl-I electrode can deliver remarkably high capacity up to 612.5 mAh gI -1 and energy density as 905 Wh kgI -1. The as-obtained energy density is 387% higher compared to the traditional one-electrons transfer of ZnǁI2 battery system and superior cycling stability with capacity retention as 95.7% after 2,000 cycles.

Atroposelective hydroarylation of biaryl phosphines directed by phosphorus centres

Prized for their ability to generate chemical complexity rapidly, catalytic carbon–hydrogen (C–H) activation and functionalization reactions have enabled a paradigm shift in the standard logic of synthetic chemistry. Directing group strategies have been used extensively in C–H activation reactions to control regio- and enantioselectivity with transition metal catalysts. However, current methods rely heavily on coordination with nitrogen and/or oxygen atoms in molecules and have therefore been found to exhibit limited generality in asymmetric syntheses. Here, we report enantioselective C–H activation with unsaturated hydrocarbons directed by phosphorus centres to rapidly construct libraries of axially chiral phosphines through dynamic kinetic resolution. High reactivity and enantioselectivity are derived from modular assembly of an iridium catalyst with an endogenous phosphorus atom and an exogenous chiral phosphorus ligand, as confirmed by detailed experimental and computational studies. This reaction mode significantly expands the pool of enantiomerically enriched functional phosphines, some of which have shown excellent efficiency for asymmetric catalysis.

A New Reaction Mode of 3-Halooxindoles: Acting as C-C-O Three-Atom Components for (3+3) Cycloaddition to Access Indolenine-Fused 2H-1,4-Oxathiines.

Herein, we report an unprecedented implementation of 3-halooxindoles as C-C-O three-atom components for (3+3) cycloaddition with pyridinium 1,4-zwitterionic thiolates, affording structurally diverse indolenine-fused 2H-1,4-oxathiines in moderate to high yields. A combined experimental and computational mechanistic study suggests that the reaction proceeds through addition of a S conjugate to the o-azaxylylene intermediate, followed by O-Michael addition and a sequential retro-Michael addition/pyridine extrusion pathway.

Photothermal catalytic conversion of water and inert nitriles to amide activated by in-situ formed transition-metal-complex nanodots

Photothermal catalytic N-acetylation of aniline has been a promising strategy to synthesize amides, which combined the advantages of thermal catalysis and photocatalysis. Herein, we demonstrate a high-performance strategy to synthesize amides catalyzed by the in-situ formed first-row transition-metal (Fe, Co, Ni, Mn et al.) complexes nanodots (TMC NDs) under solar light excitation without using noble metals or strong acids. The dual-functional nitriles substrates acted as the ligands to coordinate with transition-metal salts affording photosensitive TMC NDs with high solar-to-thermal energy conversion efficiency. Intramolecular charge transitions reduced the energy barrier of nitriles activation by weakening CN bond and triggered near-field temperature rise via the electron–phonon scattering non-radiative pathway. The reaction system exhibited good tolerance to different functional groups, affording a series of amide derivatives. Such a dynamic coordination reaction mode and the in-situ formed TMC NDs opens new avenues toward solar-heat conversion via photon–phonon coupling in the field of chemical synthesis.

Accessing gold p-acid reactivity under electrochemical anode oxidation (EAO) through oxidation relay

The gold π-acid activation under electrochemical conditions is achieved. While EAO allows easy access to gold(III) intermediates over alternative chemical oxidation under mild conditions, the reported examples so far are limited to coupling reactions due to the rapid AuIII reductive elimination. Using aryl hydrazine-HOTf salt as precursors, the π-activation reaction mode was realized through oxidation relay. Both alkene and alkyne di-functionalization were achieved with excellent functional group compatibility and regioselectivity, which extended the versatility and utility of electrochemical gold redox chemistry for future applications.

Visible-Light-Driven α-C(sp3)–H Bond Functionalization of Glycine Derivatives

The glycine motif is widely prevalent in bioactive peptides. Thus, the direct and precise modification of glycine derivatives has attracted significant attention over the past few decades. Among various protocols for the modification of glycine derivatives, the visible-light-driven direct α-C(sp3)–H bond functionalization of glycine derivatives has emerged as a powerful tool to achieve this objective, owing to its merits in atom economy, selectivity, reaction simplicity, and sustainability. This review summarizes the recent advancements in visible-light-driven direct α-C(sp3)–H bond functionalization of glycine derivatives. The contents of this review are organized based on the photocatalysts employed and the various reaction modes in the functionalization process. The mechanism, the challenges encountered, and future trends are also discussed, enabling readers to understand the current developmental status in this field.

Construction of Bridged Benzazepines via Photo‐Induced Dearomatization

AbstractBridged benzazepine scaffolds, possessing unique structural and physicochemical activities, are widespread in various natural products and drugs. The construction of these skeletons often requires elaborate synthetic effort with low efficiency. Herein, we develop a simple and divergent approach for constructing various bridged benzazepines by a photocatalytic intermolecular dearomatization of naphthalene derivatives with readily available α‐amino acids. The bridged motif is created via a cascade sequence involving photocatalytic 1,4‐hydroaminoalkylation, alkene isomerization and cyclization. Interestingly, the diastereoselectivity can be regulated through different reaction modes in the cyclization step. Moreover, aminohydroxylation and its further bromination have also been demonstrated to access highly functionalized bridged benzazepines. Preliminary mechanistic studies have been performed to get insights into the mechanism. This method provides a divergent synthetic approach for construction of highly functionalized bridged benzazepines, which have been otherwise difficult to access.

Reaction of 3-Br-coumalate with alkynals

Coumalic acid derivatives represent greener and renewable sources for organic synthesis. We report a new reaction mode by the reaction of 3-Br-coumalate with alkynals, affording the racemic C5/C6 difunctionalized products with excellent diastereoselectivity and unusual Z-selectivity.