Selective Transformation Research Articles

Insights into solvent effect on selective production of furfural and 5-hydroxymethylfurfural from fructose

Selective transformation of biomass-based feedstocks into value-added energy chemical is one of the most critical steps in biorefinery process. Herein, we gave insight into solvent effect on selective production of furfural or 5-hydroxymethylfurfural (HMF) from fructose with the combination of experiments, nuclear magnetic resonance (NMR) and molecular dynamics (MD) simulation. It was found that the selective formation of furfural and HMF was mainly dominated by solvent polarity and basicity, and solvent properties could change the reaction pathway of fructose. High polarity-high basicity solvent promoted HMF formation, while high polarity-low basicity solvent was conductive to furfural formation. The preferential arrangement of solvents around fructose tautomers, especially on different C-OH, consequently led to the different products. High yields of furfural (76.2%) and HMF (90.5%) were obtained in the solvents of γ-butyrolactone (GBL)–H2O and dimethyl sulfoxide (DMSO)–H2O.

Selective transformation and removal of As(III) by constructed Fe−N bonds: The generation of singlet oxygen from the photoexcitation of MnPc leads to abundant ZnFe−LDH interface OH radical

In this study, MnPc intercalated Zn/Fe layered double hydroxides (MnPc/ZF−LDH) were synthesized by pillared intercalation modification with different MnPc intercalation amounts and used for the selective transformation and removal of As(III) from the arsenate-phosphate mixed solution. Fe−N bonds were constructed by the complexation of MnPc and iron ions on the Zn/Fe layered double hydroxides (ZF−LDH) interface. The DFT calculation results show that the binding energy of Fe−N bonded to arsenite (−3.75 eV) was higher than that of phosphate (−3.16 eV), resulting in MnPc/ZnFe−LDH exhibiting high As(III) selective adsorption performance and anchoring it rapidly in the arsenite -phosphate mixed solution. The maximum adsorption capacity of 1MnPc/ZF−LDH for As(III) could reach 180.7 mg·g−1 under dark conditions. MnPc also acts as a photosensitizer to provide more active species for the photocatalytic reaction. A series of experiments demonstrated that MnPc/ZF−LDH exhibits high As(III) selective photocatalytic performance. A total of 10 mg·L−1 of As(III) was completely removed in the reaction system within 50 min in a single As(III) environment. In an environment with As(III) and PO43−, it achieved 80.0 % removal efficiency of As(III) and showed a good reuse effect. The introduction of MnPc could improve the utilization of visible light by the MnPc/ZnFe−LDH. The singlet oxygen generated from photoexciting MnPc leads to abundant ZnFe−LDH interface OH. In addition, MnPc/ZnFe−LDH shows good recyclability, making it a promising multifunctional material for the purification of arsenic-polluted sewage.

(NNC)Ru(II) Complex Catalyzed Selective Functionalization of Ketones with Methanol: Understanding the Role of Ancillary Ligands

Employing a single catalyst and substrate, the selective synthesis of all probable products upon varying the reaction conditions is uniquely challenging and exciting to explore. Utilizing methanol, cyclometalated (NNC)Ru(II) complex catalyzed selective transformation of a wide variety of ketones to the corresponding alcohols, β-methylated alcohols, and α-methylated ketones is disclosed. Notably, by changing the reaction parameters, the selective synthesis of all the probable products for the reactions of ketones with methanol was achieved. For these transformations, the role of different ancillary ligands (DMSO, CH3CN and PPh3) coordinated to the Ru(II) center was investigated. This protocol was successfully applied for the functionalization of a few pharmaceutically important molecules and to sterically hindered α, α′-disubstituted and α, α′, α′′-trisubstituted ketones. Several control experiments, kinetic studies, Hammett studies, and DFT calculations were carried out to understand this catalytic process.

Selective Transformation of Micropollutants in Saline Wastewater by Peracetic Acid: The Overlooked Brominating Agents.

Peracetic acid (PAA) is an emerging alternative disinfectant for saline waters; HOBr or HOCl is known as the sole species contributing to halogenation reactions during PAA oxidation and disinfection. However, new results herein strongly indicated that the brominating agents (e.g., BrCl, Br2, BrOCl, and Br2O) are generated at concentrations typically lower than HOCl and HOBr but played significant roles in micropollutants transformation. The presence of Cl- and Br- at environmentally relevant levels could greatly accelerate the micropollutants (e.g., 17α-ethinylestraiol (EE2)) transformation by PAA. The kinetic model and quantum chemical calculations collectively indicated that the reactivities of bromine species toward EE2 follow the order of BrCl > Br2 > BrOCl > Br2O > HOBr. In saline waters with elevated Cl- and Br- levels, these overlooked brominating agents influence bromination rates of more nucleophilic constituents of natural organic matter and increase the total organic bromine. Overall, this work refines our knowledge regarding the species-specific reactivity of brominating agents and highlights the critical roles of these agents in micropollutant abatement and disinfection byproduct formation during PAA oxidation and disinfection.

Selective hydrogenolysis of 5-hydroxymethylfurfural to 5-methylfurfural over Au/TiO2

5-Methylfurfural (MF) is a critical commodity chemical used as food additive and synthetic intermediate. Opening a sustainable route towards highly selective synthesis of MF from 5-hydroxymethylfurfural (HMF) is of great significance, but has demonstrated extremely challenging. Herein, we report an efficient process for the selective production of MF from HMF over an anatase-supported gold catalyst (Au/a-TiO2). During the hydrogenolysis of HMF, the desired CO bond is maintained and MF can be obtained in a high yield of 83.1 %, exhibiting excellent stability both in batch and flow operation. A combination of experimental and theoretical analyses attribute the superior performance of Au/a-TiO2 to the synergistic effect of limited H access, low adsorption of reactants, and avoiding condensation, driven by the high concentration of oxygen vacancies in the support. This study highlights a novel approach of tailoring the coverage of active species for the selective transformation of renewable compounds into high-value-added chemicals.

Elaborating E/Z‐Geometry of Alkenes via Cage‐Confined Arylation Catalysis of Terminal Olefins

AbstractA visible light photosensitizing metal‐organic cage is applied as an artificial supramolecular reactor to control the reaction of aryl radicals with terminal olefins under green light/solvent conditions, which facilitates selective transformation in the confined enzyme‐mimicking environment to give a series of geometrically defined E/Z‐alkenes. The hydrophobic cage displays good host–guest inclusion with aromatic substrates, promoting Meerwein arylation and protecting E‐isomeric products during reaction; while a small amount of benzonitrile can turn on efficient E→Z isomerization. Besides π–π stacking, the hydrogen bonding and halogen bonding interactions also act as control forces for the arylation of aliphatic terminal olefins known as poor acceptors in classic Meerwein arylation. The application of this switchable cage‐confined arylation catalysis has been demonstrated by the syntheses of Tapinarof and a marine natural product from the same substrate via controllable E/Z selectivity.

Elaborating E/Z-Geometry of Alkenes via Cage-Confined Arylation Catalysis of Terminal Olefins.

A visible light photosensitizing metal-organic cage is applied as an artificial supramolecular reactor to control the reaction of aryl radicals with terminal olefins under green light/solvent conditions, which facilitates selective transformation in the confined enzyme-mimicking environment to give a series of geometrically defined E/Z-alkenes. The hydrophobic cage displays good host-guest inclusion with aromatic substrates, promoting Meerwein arylation and protecting E-isomeric products during reaction; while a small amount of benzonitrile can turn on efficient E→Z isomerization. Besides π-π stacking, the hydrogen bonding and halogen bonding interactions also act as control forces for the arylation of aliphatic terminal olefins known as poor acceptors in classic Meerwein arylation. The application of this switchable cage-confined arylation catalysis has been demonstrated by the syntheses of Tapinarof and a marine natural product from the same substrate via controllable E/Z selectivity.

Facile Hydrogenation of Furfural by MOF-Derived Graphitic Carbon Wrapped FeCo Bimetallic Catalysts.

A catalytic system for selective transformation of furfural into biofuel is highly desirable. However, selective hydrogenation of the C=O group over the furan ring of furfural to produce ether in one step is challenging. Here, we report the preparation of a series of magnetically recoverable FeCo@GC nano-alloys (37-40 nm). Fe3 O4 (3-5 nm) and MOF-71 (Co), used as the Co and C source, were mixed together in a range of Fe/Co ratios, and then encapsulated in a graphitic carbon (GC) shell to prepare such alloys. STEM-HAADF shows the darker core made of FeCo and the shell of graphitic carbon. Furfural is hydrogenated to produce >99% isopropyl furfuryl ether in isopropanol with >99% conversion at 170 °C under 40 bars of H2 , whereas n-chain alcohol, such as ethanol, produces corresponding ethyl levulinate in 93%. The synergistic effect due to the charge transfer from Fe to Co leads to higher reactivity of FeCo@GC. The catalyst, which can be separated from the reaction medium using a simple magnet without significant damage to the surface or composition, retained its reactivity and selectivity for up to four consecutive cycles.

Regulating the catalytic activities of Ni and Pd through doping on Fe2O3HT for selective hydrogenation of conjugated aldehyde (citral) in lemongrass essential oil to organoleptically superior monoterpene alcohols (geraniol/nerol)

Fe2O3 was modified by doping Ni and Pd to obtain 3%Ni-1.5%Pd/Fe2O3HT catalyst via the hydrothermal process for selective hydrogenation of citral to nerol and geraniol. This catalyst was prepared by different techniques like co-precipitation, wet impregnation, and hydrothermal process, and their activity towards citral hydrogenation was thoroughly studied. The prepared catalysts were thoroughly characterized. Various parameters such as pressure, temperature, reaction time, and metal weight (%) have been optimized through the RSM-BBD module to attain high selectivity towards nerol and geraniol. The optimal reaction conditions of 6.45 bar pressure, 3%Ni-1.5%Pd loading at 72.1 °C for 84 min, the citral (>99%) was converted to nerol/geraniol with 97.2% of selectivity. The modified catalyst activated the oxygen species of the carbonyl atom and thus favours the selective hydrogenation of the CO bond without reducing the CC bond. This process is very effective for the selective transformation of citral (75%) in lemongrass essential oil to organoleptically superior nerol/geraniol-rich oil using 3%Ni-1.5%Pd/Fe2O3HT catalyst.

Selective Plasmon-Induced Oxidation of 4-Aminothiophenol on Silver Nanoparticles

Selectivity in plasmonic chemistry is typically achieved using bimetallic nanostructures. Herein, we show that monometallic silver nanoparticles can also drive highly selective interfacial transformations, oxidation reactions particularly. This is illustrated through a close inspection of tip-enhanced Raman spectral images of 4-aminothiophenol (ATP)-functionalized Au vs Ag nanoparticles. We find that whereas the thoroughly described dimerization reaction to form 4,4′-dimercaptoazobenzene dominates the response on Au, highly selective oxidation on Ag nanoparticles exclusively leads to 4-nitrothiophenol. We explore the origin of the distinct reaction pathways on Ag vs Au nanostructures.

The Direct Conversion of Esters to Ketones Enabled by a Traceless Activating Group.

We report here the design and development of a method for the single-step conversion of esters to ketones with simple reagents. The selective transformation of esters to ketones, rather than tertiary alcohols, is made possible by the use of a transient sulfinate group on the nucleophile that activates the adjacent carbon toward deprotonation to form a carbanion that adds to the ester, followed by a second deprotonation to prevent further addition. The resulting dianion undergoes spontaneous fragmentation of the SO2 group upon quenching with water to reveal the ketone product.

Electrocatalytic Reduction of CO2 to Value‐Added Chemicals via C–C/N Coupling

The efficient conversion and utilization of CO2 is imminent due to the increase of global CO2 emissions year by year, so the strategy of electrocatalytic CO2 reduction to high value‐added chemicals comes into being. The CO2 reduction reaction (CO2RR) can yield diversified products, including C1 (like CO, CH4, etc.), C2 (like C2H4, C2H5OH, etc.), and other multicarbon compounds. Thereinto, selective transformation to C2 compounds is relatively significative by reason of high industrial value but being greatly challenging, particularly involving complex CC coupling. Herein, the reaction mechanisms of several C2 products (including C2H4, C2H5OH, and H2C2O4) and corresponding latest research progress are summarized and discussed. Besides, N atoms, from N2, nitrates, and nitrites, are integrated into CO2RR to yield nitrogen‐containing organics (like urea, amides, and amines), broadening the application field of CO2RR. Therefore, the part on the electrocatalytic coupling of CO2 and nitrogen sources (including N2, NO3−, NO2−) by CN bonds is also delved in this review, including recent advances, reaction mechanisms, and related key intermediates.

Aromatics production from catalytic pyrolysis of waste cassava residue using La and P modified ZSM-5: Experimental and kinetic study

In the present study, selective transformation of waste cassava residues into aromatics via catalytic pyrolysis over as-prepared La and P modified ZSM-5 was systematically investigated, especially in the aspects of product regulation and kinetic analysis. Comprehensive physicochemical characterizations were undertaken for unveiling the essential structural properties of La and P modified ZSM-5. The introduction of La and P species significantly enriched the Lewis and Brønsted acid sites in ZSM-5, thus facilitating the directional pyrolysis of waste cassava residues into aromatics. Higher apparent activation energy for aromatics formation from waste cassava residues pyrolysis in the presence of La and P modified ZSM-5 might be due to the fact that the catalytic pyrolysis belonged to diffusion-controlled gas-solid reaction. In comparison with that of the parent ZSM-5, LaP2/ZSM exhibited better performance towards aromatics formation in waste cassava residues pyrolysis, wherein the relative content of aromatics reached 83.3% at a temperature of 650 °C. Gratifyingly, the relative content of aromatics was increased to 90.5% for the catalytic pyrolysis of acid pretreated cassava residue, in the case of LaP1/ZSM catalyst.

Uniform segmented platelet micelles with compositionally distinct and selectively degradable cores

The creation of nanoparticles with controlled and uniform dimensions and spatially defined functionality is a key challenge. The recently developed living crystallization-driven self-assembly (CDSA) method has emerged as a promising route to one-dimensional (1D) and 2D core–shell micellar assemblies by seeded growth of polymeric and molecular amphiphiles. However, the general limitation of the epitaxial growth process to a single core-forming chemistry is an important obstacle to the creation of complex nanoparticles with segmented cores of spatially varied composition that can be subsequently exploited in selective transformations or responses to external stimuli. Here we report the successful use of a seeded growth approach that operates for a variety of different crystallizable polylactone homopolymer/block copolymer blend combinations to access 2D platelet micelles with compositionally distinct segmented cores. To illustrate the utility of controlling internal core chemistry, we demonstrate spatially selective hydrolytic degradation of the 2D platelets—a result that may be of interest for the design of complex stimuli-responsive particles for programmed-release and cargo-delivery applications.

Selective transformation of carbohydrates to 5-ethoxymethylfurfural over tungstophosphoric acid supported on activated carbon derived from orange peel

A series of tungstophosphoric acid supported on activated carbon derived from left-over orange-peel catalysts (TPA/OAC) have been prepared. These catalysts were examined for one-pot catalytic transformation of fructose/glucose to 5-ethoxymethylfurfural. Physico-chemical properties of the catalytic materials were executed by using various characterization methods. Spectroscopic analysis results propose that TPA was finely distributed on the high surface area carbon support with persistent Keggin ion structure. The EMF yield is depended on the content of active component TPA on support and also on the reaction conditions. The catalyst with 25 wt% TPA on OAC presented highest activity towards EMF synthesis from fructose. Although, the catalyst 25 wt% TPA/OAC showed low activity towards EMF synthesis from glucose, higher yields of ethyl glucopyranoside could be formed from glucose in EtOH. Activated carbon was synthesized by carbonization of orange peel treated with H3PO4, which was used as a good support for HPAs. The catalysts are quite stable and recyclable for the dehydrative alkylation of fructose.

Cross- and Multi-Coupling Reactions Using Monofluoroalkanes.

Carbon-fluorine bonds are stable and have demonstrated sluggishness against various chemical manipulations. However, selective transformations of C-F bonds can be achieved by developing appropriate conditions as useful synthetic methods in organic chemistry. This review focuses on C-C bond formation at monofluorinated sp3 -hybridized carbons via C-F bond cleavage, including cross-coupling and multi-component coupling reactions. The C-F bond cleavage mechanisms on the sp3 -hybridized carbon centers can be primarily categorized into three types: Lewis acids promoted F atom elimination to generate carbocation intermediates; nucleophilic substitution with metal or carbon nucleophiles supported by the activation of C-F bonds by coordination of Lewis acids; and the cleavage of C-F bonds via a single electron transfer. The characteristic features of alkyl fluorides, in comparison with other (pseudo)halides as promising electrophilic coupling counterparts, are also discussed.

Selective CO2 Electroreduction to Formate on Polypyrrole-Modified Oxygen Vacancy-Rich Bi2 O3 Nanosheet Precatalysts by Local Microenvironment Modulation.

Challenges remain in the development of highly efficient catalysts for selective electrochemical transformation of carbon dioxide (CO2 ) to high-valued hydrocarbons. In this study, oxygen vacancy-rich Bi2 O3 nanosheets coated with polypyrrole (Bi2 O3 @PPy NSs) are designed and synthesized, as precatalysts for selective electrocatalytic CO2 reduction to formate. Systematic material characterization demonstrated that Bi2 O3 @PPy precatalyst can evolveintoBi2 O2 CO3 @PPy nanosheets with rich oxygen vacancies (Bi2 O2 CO3 @PPy NSs) via electrolyte-mediated conversion and function as the real active catalyst for CO2 reduction reaction electrocatalysis. Coating catalyst with a PPy shell can modulate the interfacial microenvironment of active sites, which work in coordination with rich oxygen vacancies in Bi2 O2 CO3 and efficiently mediate directional selective CO2 reduction toward formate formation. With the fine-tuning of interfacial microenvironment, the optimized Bi2 O3 @PPy-2 NSs derived Bi2 O2 CO3 @PPy-2 NSs exhibit a maximum Faradaic efficiency of 95.8% at -0.8V (versus.reversible hydrogen electrode) for formate production. This work might shed some light on designing advanced catalysts toward selective electrocatalytic CO2 reduction through local microenvironment engineering.

Selective Synthesis and Structural Transformation of a 4-Ravel Containing Four Crossings and Featuring Cp*Rh/Ir Fragments.

Intricately interwoven topologies have been continually synthesized and are ultimately equally versatile and significant at the nanoscale level; however, reports concerning ravel structures, which are highly entwined new topological species, are extremely rare and fraught with tremendous synthesis challenges. To solve the synthesis problem, a tetrapodontic pyridine ligand L1 with two types of olefinic bond units and two Cp*M-based building blocks (E1, M=Rh; E2, M=Ir) featuring large conjugated planes was prepared to perform the self-assembly. Two unprecedented [5+10] icosanuclear molecular 4-ravels containing four crossings were obtained by parallel-displaced π···π interactions in a single-step strategy. Remarkably, reversible structural transformations between 4-ravel and the corresponding metallocage could be realized by concentration changes and solvent- and guest-induced effects. X-ray crystallographic data and NMR spectroscopy provide full confirmation of these phenomena.

Selective Synthesis and Structural Transformation of a 4‐Ravel Containing Four Crossings and Featuring Cp*Rh/Ir Fragments

AbstractIntricately interwoven topologies are continually being synthesized and are ultimately equally versatile and significant at the nanoscale level; however, reports concerning ravel structures, which are highly entwined new topological species, are extremely rare and fraught with tremendous synthesis challenges. To solve the synthesis problem, a tetrapodontic pyridine ligand L1 with two types of olefinic bond units and two Cp*M‐based building blocks (E1, M=Rh; E2, M=Ir) featuring large conjugated planes was prepared to perform the self‐assembly. Two unprecedented [5+10] icosanuclear molecular 4‐ravels containing four crossings were obtained by parallel‐displaced π⋅⋅⋅π interactions in a single‐step strategy. Remarkably, reversible structural transformations between the 4‐ravel and the corresponding metallocage could be realized by concentration changes and solvent‐ and guest‐induced effects. X‐ray crystallographic data and NMR spectroscopy provide full confirmation of these phenomena.

Innenrücktitelbild: Selective Synthesis and Structural Transformation of a 4‐Ravel Containing Four Crossings and Featuring Cp*Rh/Ir Fragments (Angew. Chem. 20/2023)

Two unprecedented [5+10] icosanuclear molecular 4-ravels containing four crossings were designed rationally and synthesized successfully using a single-step strategy by Li-Long Dang, Guo-Xin Jin et al. in their Research Article (e202301516). This new topology is achieved by utilizing parallel-displaced π⋅⋅⋅π interactions with carefully selected naphthoquinoyl Cp*M building blocks and X-shaped pyridyl ligand.