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'On‐water' catalysis entails the significant enhancement of a chemical reaction by water, even when those reactions are known to be water‐sensitive. Here, the findings about the anionic ring opening polymerization of epoxides at the static interface between oil and alkaline water are shared. Unexpectedly, high molar mass fractions are observed with the interfacial system presented herein, albeit at very low conversions (< 5%). Styrene oxide, a notably unreactive epoxide, is chosen as the model compound to investigate the influence of several reaction parameters (i.e., pH, type of the initiator salt, polymerization time, interfacial area, solvent, shaking) on the polymerization. Poly(styrene oxide) (PSO) with an Mn of 5300 g mol−1 is observed via MALDI‐ToF MS, with species of at least 8000 g mol−1. The feasibility of expanding the system to (cyclic) aliphatic and aromatic epoxides, and glycidyl ethers is also explored. The system appears to promote polymerization of epoxides that position at the interface, in such a way that initiation and propagation can occur. A mechanistic interpretation of the interfacial polymerization is suggested. The surprising results obtained in this work urge to revisit the role of water in ionic polymerizations. [ABSTRACT FROM AUTHOR]

New chloride‐ and bromide‐modified metal–organic frameworks (MOFs) based on copper and 1,3‐bis (carboxymethyl)imidazole (bcmim) derivatives have been prepared via post–synthetic modification (PSM) or by a direct route, following a simple, effective, and sustainable protocol. These materials have been characterized, and their catalytic activity has been studied. Cu‐bcmim‐Cl and Cu‐bcmim‐Br materials have been shown to be more efficient acidic catalytic systems than nonmodified materials. The catalytic activity has been tested as a Lewis acid catalyst in the methanolysis of styrene oxide and in the synthesis of quinolines and acridines, with the recovery and recyclability of the catalysts being possible. Furthermore, the catalytic activity of the catalysts has been tested in the oxidative coupling of formamides and carboxylic acids. [ABSTRACT FROM AUTHOR]

The first synthesis of 3,4-diarylpyrimido[1,2-b]indazole derivatives from 3-aminoindazoles has been realized. The FeCl3-catalyzed intermolecular epoxide ring-opening reaction altered the order of annulation, with the free primary NH2 groups in 3-aminoindazoles preferentially reacting with styrene oxides instead of aromatic aldehydes. This protocol is further highlighted by its broad substrate compatibility, high chemo- and regioselectivities, and the late-stage modifications of bioactive molecules. Without aromatic aldehydes, the synthesis of 3-aryl-4-acylpyrimido[1,2-b]indazole derivatives can also be accomplished using alternative reaction conditions. [ABSTRACT FROM AUTHOR]

The fixation of carbon dioxide (CO2) with epoxide to form cyclic carbonates is industrially important because of the high economic value of the products. Quaternized carbon dots have great potential in CO2 cycloaddition under their high activity and facile synthesis without cocatalysts. Herein, novel quaternized carbon dots were synthesized through a microwave method using citric acid and ethanolamine with different amounts of (2-bromoethyl)trimethylammonium bromide (Br-CDs) or (2-chloroethyl)trimethylammonium chloride (Cl-CDs). All carbon dots were characterized by TEM, XPS, FT-IR, UV-vis and zeta potential analyses as well as elemental analysis. Br1-CD showed the best catalytic activity (99%) and selectivity (99%) for CO2 cycloaddition with styrene oxide to 4-phenyl-1,3-dioxolan-2-one under suitable conditions (120 °C, 8 h, and 0.1 MPa). Furthermore, the catalyst can be easily recycled up to five times. [ABSTRACT FROM AUTHOR]

Oxidation of styrene is a key reaction in the synthesis of pharmaceuticals and fine chemicals, and therefore oxidizing styrene with selective, efficient, and recyclable heterogeneous catalysts is significant from an environmental and economic standpoint. In this study, we report the transition Cr-based metal–organic framework [NH2-MIL-101(Cr)] as a heterogeneous photocatalyst, which efficiently promotes styrene epoxidation using H2O2 as a green oxidant, achieving high conversion efficiency (98%) and excellent selectivity (82%) under ambient conditions. Radical detection and quenching experiments reveal that the superoxide radical anion (O2˙−) acts as an active oxygen species, selectively promoting the oxidation of styrene to its oxidized form. This work provides insight into the development of a sustainable and cost-effective method for producing styrene oxide. [ABSTRACT FROM AUTHOR]

The document is the contents list for the journal "Chemical Communications" published on September 25, 2024. It includes various articles on topics such as responsive DNA hydrogels, lithium metal-based battery systems, and strategies in photochemical alcohol oxidation. The journal is published by The Royal Society of Chemistry, a leading chemistry community, and aims to connect the world with the chemical sciences. [Extracted from the article]

Chiral carbon nanodots (CNDs) were fabricated through the hydrothermal processing of sulfanilic acid and chiral tartaric acid, exhibiting outstanding catalytic performance for the chiral catalysis of the ring-opening reaction. Furthermore, the catalytic mechanism was proposed to understand the link between the chiral structure and the performance of the catalyst. [ABSTRACT FROM AUTHOR]

Tetradentate ONNO donor ligands H2hz(fp)2 (I), H2hz(butp)2 (II) and H2hz(bp)2 (III) synthesized by the reaction of hydrazine hydrate with 4‐formyl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (fp), 4‐butyryl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (butp) and 4‐benzoyl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (bp), respectively, react with [MoVIO2(acac)2] in 1 : 2 molar ratio in refluxing methanol to give binuclear complexes [(μ‐O){MoVIO2(H2O)}2hz(fp)2] (1) and [(μ‐O){MoVIO2(H2O)}2hz(butp)2] (2) and [(μ‐O){MoVIO2(H2O)}2hz(bp)2] (3). All ligands and complexes are characterized by several techniques that include, FT‐IR, UV/Vis, 1H NMR, 13C NMR spectroscopy, elemental and thermal analysis, and single crystal X‐ray analysis of 2 and 3. Ligands coordinate through a set of ON functionalities of the same ligand to two MoVIO2 groups attached through an oxido‐bridge. Additional coordination of water to each vanadium makes each of them to maintain an octahedral geometry. Azine moiety coordinates to two molybdenum through the symmetrical μ‐{η2‐(N−N)} fashion. Catalytic activity of these complexes was studied for the cycloaddition of CO2 with epoxides. A pressure of 4 bar CO2, 3.0 mg catalyst, 1 mmol of tetrabutylammonium bromide (TBAB) at 120 °C for 6 h were found to be most suited reaction condition for 10 mmol epoxide. Under the optimized reaction conditions, the product yield and selectivity of alkene carbonate for all complexes were investigated. As high as 96 % yield with almost 99 % selectivity for styrene carbonate under these optimized reaction conditions was achieved. [ABSTRACT FROM AUTHOR]

The epoxidation of olefins on Ag/O systems is a significant industrial‐scale process within heterogeneous catalysis. However, the details of the surface reaction remain controversial, and it has been highly challenging to reconcile the findings from cataltyic studies under reaction conditions with the highly detailed static studies under carefully controlled ultra‐high vacuum (UHV) conditions. In this study, we combine molecular beam surface scattering and ion imaging techniques to explore the partial oxidation of styrene. This experimental approach enhances the sensitivity to the extent that we can directly observe the partial oxidation product, styrene oxide, under UHV conditions. We note that partial oxidation exclusively occurs at high oxygen coverages, which we attribute to the reaction of styrene with electrophilic oxygen formed specifically at elevated coverages. [ABSTRACT FROM AUTHOR]

Rodent inhalation studies indicate styrene is a mouse lung-specific carcinogen. Mode-of-action (MOA) analyses indicate that the lung tumors cannot be excluded as weakly quantitatively relevant to humans due to shared oxidative metabolites detected in rodents and humans. However, styrene also is not genotoxic following in vivo dosing. The objective of this review was to characterize occupational and general population cancer risks by conservatively assuming mouse lung tumors were relevant to humans but operating by a non-genotoxic MOA. Inhalation cancer values reference concentrations for respective occupational and general population exposures (RfCcar-occup and RfCcar-genpop) were derived from initial benchmark dose (BMD) modeling of mouse inhalation tumor dose–response data. An overall lowest BMDL10 of 4.7 ppm was modeled for lung tumors, which was further duration- and dose-adjusted by physiologically based pharmacokinetic (PBPK) modeling to derive RfCcar-occup/genpop values of 6.2 ppm and 0.8 ppm, respectively. With the exception of open-mold fiber reinforced composite workers not using personal protective equipment (PPE), the RfCcar-occup/genpop values are greater than typical occupational and general population human exposures, thus indicating styrene exposures represent a low potential for human lung cancer risk. Consistent with this conclusion, a review of styrene occupational epidemiology did not support a conclusion of an association between styrene exposure and lung cancer occurrence, and further supports a conclusion that the conservatively derived RfCcar-occup is lung cancer protective. [ABSTRACT FROM AUTHOR]

The new homochiral 1D metal–organic coordination polymer {Cu[bdc-(N-MePro)H2O]·0.25H2O}n was synthesized using 2-[(1-methyl- L -prolyl)amino]terephthalic acid, which was obtained for the first time. The unique crystal structure of the new compound was determined using powder X-ray diffraction. The catalytic performance of {Cu[bdc-(N-MePro)H2O]·0.25H2O}n in the asymmetric ring opening reactions of styrene oxide and cyclohexene oxide with aniline was evaluated. [ABSTRACT FROM AUTHOR]

Crystalline zeolites have high acidity but limited utility due to microporosity, whereas mesoporous amorphous aluminosilicates offer better porosity but lack sufficient acidity. In this work, we investigated defect engineering to fine-tune the acidity of amorphous acidic aluminosilicates (AAS). Here we introduced oxygen vacancies in AAS to synthesize defective acidic aluminosilicates (D-AAS). 1H, 27Al, and 17O solid-state nuclear magnetic resonance (NMR) studies indicated that defects induced localized structural changes around the acidic sites, thereby modifying their acidity. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy studies substantiated that oxygen vacancies alter the chemical environment of Brønsted acidic sites of AAS. The effect of defect creation in AAS on its acidity and catalytic behavior was demonstrated using four different acid-catalyzed reactions namely, styrene oxide ring opening, vesidryl synthesis, Friedel-Crafts alkylation, and jasminaldehyde synthesis. The defects played a role in activating reactants during AAS-catalyzed reactions, enhancing the overall catalytic process. This was supported by in-situ FTIR, which provided insights into the molecular-level reaction mechanism and the role of defects in reactant activation. This study demonstrates defect engineering as a promising approach to fine-tune acidity in amorphous aluminosilicates, bridging the porosity and acidity gaps between mesoporous amorphous aluminosilicates and crystalline zeolites. Is it possible to fine-tune the acidity of amorphous aluminosilicates? Here authors use defect engineering as a method to optimize acidity, bridging the porosity and acidity gaps between amorphous aluminosilicates and crystalline zeolites. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([FeII(PBI)3](CF3SO3)2 (1), where PBI = 2-(2-pyridyl)benzimidazole), catalytic and stoichiometric aziridination of styrenes using PhINTs ([(N-tosylimino)iodo]benzene), highlighting the importance of reaction conditions including the effects of the solvent, co-ligands (para-substituted pyridines), and substrate substituents on the product yields, selectivity, and reaction kinetics. The aziridination reactions with 1/PhINTs showed higher conversion than epoxidation with 1/PhIO (iodosobenzene). However, the reaction with PhINTs was less selective and yielded more products, including styrene oxide, benzaldehyde, and 2-phenyl-1-tosylaziridine. Therefore, the main aim of this study was to investigate the potential role of water in the formation of oxygen-containing by-products during radical-type nitrene transfer catalysis. During the catalytic tests, a lower yield was obtained in a protic solvent (trifluoroethanol) than in acetonitrile. In the case of the catalytic oxidation of para-substituted styrenes containing electron-donating groups, higher yield, TON, and TOF were achieved than those with electron-withdrawing groups. Pseudo-first-order kinetics were observed for the stoichiometric oxidation, and the second-order rate constants (k2 = 7.16 × 10−3 M−1 s−1 in MeCN, 2.58 × 10−3 M−1 s−1 in CF3CH2OH) of the reaction were determined. The linear free energy relationships between the relative reaction rates (logkrel) and the total substituent effect (TE, 4R-PhCHCH2) parameters with slopes of 1.48 (MeCN) and 1.89 (CF3CH2OH) suggest that the stoichiometric aziridination of styrenes can be described through the formation of a radical intermediate in the rate-determining step. Styrene oxide formation during aqueous styrene aziridination most likely results from oxygen atom transfer via in situ iron oxo/oxyl radical complexes, which are formed through the hydrolysis of [FeIII(N•Ts)] under experimental conditions. [ABSTRACT FROM AUTHOR]

This study explored the catalytic performance of two robust zirconium-based metal–organic frameworks (MOFs), MIP-202(Zr) and UiO-66-(CO2H)2 in the ring-opening of epoxides using alcohols and amines as nucleophilic reagents. The MOFs were characterized by techniques such as FT-IR, PXRD, FE-SEM, and EDX. Through systematic optimization of key parameters (catalyst amount, time, temperature, solvent), MIP-202(Zr) achieved 99% styrene oxide conversion in 25 min with methanol at room temperature using 5 mg catalyst. In contrast, UiO-66-(CO2H)2 required drastically harsher conditions of 120 min, 60 °C, and four times the catalyst loading to reach 98% conversion. A similar trend was observed for ring-opening with aniline –MIP-202(Zr) gave 93% conversion in one hour at room temperature, while UiO-66-(CO2H)2 needed two hours at 60 °C for 95% conversion. The superior performance of MIP-202(Zr) likely stems from cooperative Brønsted/Lewis acid sites and higher proton conductivity enabling more efficient epoxide activation. Remarkably, MIP-202(Zr) maintained consistent activity over five recycles in the ring-opening of styrene oxide by methanol and over three recycles in the ring-opening of styrene oxide by aniline. Testing various epoxide substrates and nucleophiles revealed trends in reactivity governed by electronic and steric effects. The results provide useful insights into tuning Zr-MOF-based catalysts and highlight the promise of the cost-effective and sustainable MIP-202(Zr) for diverse epoxide ring-opening reactions on an industrial scale. [ABSTRACT FROM AUTHOR]

The conventional synthesis of (S)‐flurbiprofen, a valuable non‐steroidal anti‐inflammatory drug (NSAID), involves inefficient chiral resolution with low‐yielding multiple reaction steps, or asymmetric synthesis with low enantioselectivity and/or regioselectivity. Here, we developed high‐yielding, enantioselective, and sustainable synthesis of (S)‐flurbiprofen via two chemoenzymatic approaches from a simple alkene: (A) enzymatic epoxidation‐isomerization‐oxidation cascade and Pd‐catalyzed arylation; and (B) chemical epoxidation, enzymatic isomerization‐oxidation cascade, and Pd‐catalyzed arylation. Styrene oxide isomerase (SOI)‐catalyzed enantio‐retentive Meinwald rearrangement was the key step in the two pathways, but SOI suffers from low activity. SOI was engineered via two rounds of iterative saturation mutagenesis and screening with a three‐enzyme cascade assay, generating a double‐mutant SOIDM (N99A/D95A) with 5.5‐fold improvement in catalytic efficiency (kcat/KM). In Pathway A, cascade biotransformation of 3‐fluoro‐4‐bromo‐α‐methylstyrene with engineered E. coli strain expressing SOIDM, styrene monooxygenase (SMO) and aldehyde dehydrogenase (ALDH), and subsequent Pd‐catalyzed arylation afforded (S)‐flurbiprofen in 98% yield and 91% ee. In Pathway B, chemical epoxidation (Sharpless dihydroxylation and ring‐closing), cascade conversion using an engineered E. coli strain expressing SOIDM, ALDH and NADH oxidase (NOX), and Pd‐catalyzed arylation produced (S)‐flurbiprofen in 83% yield and 98% ee. Compared to conventional synthesis, the developed methods reduced reaction steps, minimized waste generation and improved enantioselectivity or overall yield. [ABSTRACT FROM AUTHOR]

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value‐added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br−/HOBr‐mediated method is developed to achieve a near‐quantitative selectivity and ≈100% FE of styrene oxide on α‐Fe2O3, in which low concentration of Br− as mediator and locally generated acidic micro‐environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH‐dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications. [ABSTRACT FROM AUTHOR]

We successfully synthesized a bifunctional alkaline catalyst (Co@CTS-1), on the one hand, which demonstrates exceptional catalytic performance in the aerobic oxidation of alkenes, particularly in the epoxidation of styrene, in the absence of both an initiator and a co-reducing agent, achieving a conversion rate of 74.94%, a selectivity of 71.84% for styrene oxide; on the other hand, the catalyst maintained its high activity throughout a cyclic reaction run lasting up to 2500 min, demonstrating exceptional stability in the epoxidation of styrene. The Co@CTS-1 catalyst utilizes TS-1 as the carrier, and it is modified with cobalt and cerium elements. Through the embedding of cobalt elements within the TS-1 cage, the catalyst gains the ability to activate O2, and by inserting cerium elements into the atomic positions of silicon, the conversion rate is further enhanced. This encapsulated structure stabilizes cobalt nanoparticles, overcoming the short lifespan issues caused by sintering and leaching in conventional supported catalysts. This work provides practical clues for the development and application of novel catalysts, and will inspire the advancement of olefin air epoxidation. [ABSTRACT FROM AUTHOR]

The redox mediated photoelectrochemical (PEC) or electrochemical (EC) alkene oxidation process is a promising method to produce high value‐added epoxides. However, due to the competitive reaction of water oxidation and overoxidation of the mediator, the utilization of the electricity is far below the ideal value, where the loss of epoxidation's faradaic efficiency (FE) is ≈50%. In this study, a Br−/HOBr‐mediated method is developed to achieve a near‐quantitative selectivity and ≈100% FE of styrene oxide on α‐Fe2O3, in which low concentration of Br− as mediator and locally generated acidic micro‐environment work together to produce the higher active HOBr species. A variety of styrene derivatives are investigated with satisfied epoxidation performance. Based on the analysis of local pH‐dependent epoxidation FE and products distribution, the study further verified that HOBr serves as the true active mediator to generate the bromohydrin intermediate. It is believed that this strategy can greatly overcome the limitation of epoxidation FE to enable future industrial applications. [ABSTRACT FROM AUTHOR]

The CaO-supported Pt nanoparticle catalysts, herein referred to as the Pt/CaO-P catalysts, were synthesized for the first time to catalyze the selective hydrogenation of styrene oxide. All previously reported Pt- and Pd-based catalysts were prepared and evaluated under identical conditions, with 2-phenylethanol (2-PEA) being identified as the primary product in the selective hydrogenation of styrene oxide. The comparative analysis of the catalytic performance of Pt/CaO-P, Pt/CaO (unpurified), Pt/Ca(OH)2, and Pt/CaCO3 revealed that the purity of CaO is crucial for enhancing the selectivity towards 1-phenylethanol (1-PEA). Notably, the highest selectivity of 1-PEA over Pt/CaO-P reached up to 39%. Our SO-TPD, CO2-TPD and ex situ FT-IR results further indicated that strong basic sites can modify the adsorption site of SO over Pt nanoparticles, leading to the higher selectivity of 1-PEA. A proposed reaction mechanism for the ring opening of styrene oxide suggests that the breakage of conjugation between the benzene ring and the adjacent carbon cation by strong basic sites plays an important role. [ABSTRACT FROM AUTHOR]

Developing efficient and earth‐abundant catalysts for CO2 fixation to high value‐added chemicals is meaningful but challenging. Styrene carbonate has great market value, but the cycloaddition of CO2 to styrene oxide is difficult due to the high steric hindrance and weak electron‐withdrawing ability of the phenyl group. To utilize clean energy (such as optical energy) directly and effectively for CO2 value‐added process, we introduce earth‐abundant Ti single‐atom into the mesoporous nitrogen, oxygen‐doped carbon nanosheets (Ti−CNO) by a two‐step method. The Ti−CNO exhibits excellent photothermal catalytic activities and stability for cycloaddition of CO2 and styrene oxide to styrene carbonate. Under light irradiation and ambient pressure, an optimal Ti−CNO produces styrene carbonate with a yield of 98.3 %, much higher than CN (27.1 %). In addition, it shows remarkable stability during 10 consecutive cycles. Its enhanced catalytic performance stems from the enhanced photothermal effect and improved Lewis acidic/basic sites exposed by the abundant mesopores. The experiments and theoretical simulations demonstrate the styrene oxide⋅+ and CO2⋅− radicals generated at the Lewis acidic (Tiδ+) and basic sites of Ti−CNO under light irradiation, respectively. This work furnishes a strategy for synthesizing advanced single‐atom catalysts for photo‐thermal synergistic CO2 fixation to high value products via a cycloaddition pathway. [ABSTRACT FROM AUTHOR]

The preparation of CO2-containing polymers with improved degradation properties is still very challenging. An elegant method for preparing these polymers is to use CO2-containing monomers in ring-opening polymerizations (ROP) which are particularly gentle and energy-saving methods. However, cyclic carbonates are required for this which are not readily available. This paper therefore aims to present the optimization and comparison of two synthesis methods to obtain cyclic carbonates for ROP. Within this work, cyclic styrene carbonate was synthesized from readily available raw materials by using a Jacobsen catalyst for the reaction of styrene oxide and carbon dioxide or an organocatalyst for the transesterification of methyl carbonate with 1-phenyl-1,2-ethanediol. The latter performed with 100% selectivity to the desired styrene carbonate, which was succesfully tested in ROP, producing an amorphous thermoplastic polymer with a TG of 185 °C. [ABSTRACT FROM AUTHOR]

The utilization of ionic liquids as versatile reaction media and catalysts has garnered significant attention in the field of green and sustainable chemistry. In this study, sum frequency generation vibrational spectroscopy (SFG-VS) is employed to investigate the interactions between l-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and styrene oxide (SO) at the air/liquid interface. Spectral analysis in the range of 1000 cm−1 to 3700 cm−1 reveals that only vibrational modes of C–H bonds are observed. Notably, the orientation of the epoxy ring of SO is found to be towards the bulk phase, while the three C–H groups on the imidazolium ring of the cation are parallel to the surface. Consequently, there are no observed interactions between the cation and SO. However, in the vibrational spectra of C–H bonds, interactions between the anion BF4- and the CH2 group of the epoxy ring result in blue shifts in the vibrations of CH (SO) and CH3 (cation). These findings support a proposed reaction mechanism where the ionic liquid catalyzes SO first and subsequently reacts with CO2 providing valuable insights into intermolecular interactions and molecular orientations at reaction interfaces. [ABSTRACT FROM AUTHOR]

Phenylacetaldehyde (PhA) is an aromatic aldehyde which has a hyacinth‐like floral, sweet and green‐leafy odour. PhA is used as a perfumery chemical and a rate‐controlling additive in cosmeceutical and polymer industries, respectively. The conventional process of PhA manufacturing in industries involve hazardous and costly feedstock and often lead to generation of substantial amount of waste. Moreover, usage of stoichiometric reagents often makes the processes economically impractical. This article illustrates the possibility of production of PhA from low‐cost feedstock styrene through a single‐step, one‐pot method wherein various metal oxides have been utilized as catalysts for styrene oxidation under the influence of cumene hydroperoxide (CHP). Ag2O is found to be the highest PhA‐yielding catalyst and a promising candidate for scaling up for its considerably good reusability up to 6 consecutive uses. A maximum of ~45% PhA selectivity has been observed at ~60% styrene conversion. Interestingly, this process does not require any alkaline/acid wash and hence does not produce any organic/inorganic liquid effluent stream. Furthermore, all the major byproducts found, that is styrene oxide, benzaldehyde and acetophenone, are themselves considered as valorized styrene derivatives. Overall, the metal oxide catalysed styrene oxidation has potential to take over the conventional industrial process(es) for sustainable selective production of PhA Along with a plausible mechanism of styrene oxidation over Ag2O, a conceptualized reaction–separation framework has been reported for intensified production of PhA from CHP‐based styrene oxidation. [ABSTRACT FROM AUTHOR]

Quaternary ammonium salts of metal derivatives of polyoxometalates [XW11O39M(H2O)]n− (X = P, Si; M = Cr, Mn, Co, Ni, Zn) were successfully tested instead of quaternary ammonium halides as catalysts in the cycloaddition of CO2 to styrene oxide. Remarkably, they gave very satisfactory yields of styrene carbonate at moderate temperature (80 °C). [ABSTRACT FROM AUTHOR]

Nanoconfinement within enzymes can increase reaction rate and improve selectivity under mild conditions. However, it remains a great challenge to achieve chemical reactions imitating enzymes with directional molecular motion, short reaction time, ≈100% conversion, and chiral conversion in artificial nanoconfined systems. Here, directional flow ring‐opening reactions of styrene oxide and alcohols are demonstrated with ≈100% conversion in <120 s at 22 °C using graphene oxide membrane nanoreactors. Dominant products have the same configuration as chiral styrene oxide in confined reactions, which is dramatically opposed to bulk reactions. The unique chiral conversion mechanism is caused by spatial confinement, limiting the inversion of benzylic chiral carbon. Moreover, the enantiomeric excess of same‐configuration products increased with higher alkyl charge in confined reactions. This work provides a new route to achieve rapid flow ring‐opening reactions with specific chiral conversion within 2D nanoconfined channels, and insights into the impact of nanoconfinement on ring‐opening reaction mechanisms. [ABSTRACT FROM AUTHOR]

Novel imidazolinium based materials were prepared by modification of MCM-41 and characterized by elemental analysis, nitrogen sorption, thermogravimetric analysis, UV–Vis, and X‑ray diffraction. The materials differed in the alkyl, or halide used (MeI, EtBr, PrI, BuBr, BuCl, and BnBr). The characterization methods confirmed the successful formation of desired materials containing iodide and bromide. In this research, the materials were examined as catalysts for the cycloaddition of carbon dioxide to styrene oxide to produce styrene carbonate. The influence of anion type and the length of the alkyl chain in the salt was discussed. The results show imidazolinium materials as efficient heterogeneous catalysts for the model reaction. Styrene carbonate was prepared with high selectivities in all cases. The highest conversion of styrene oxide (95%) was achieved using a material containing iodomethane (MCM-Im-MeI) under the following conditions: 1.2 MPa, 120 °C, solvent free. The catalysts were successfully reused without a significant decrease of their activity. [ABSTRACT FROM AUTHOR]

The selective fixation of CO2 and epoxides into cyclic carbonates offers an atom-economical approach towards promising utilization of anthropogenic CO2 gas. This work demonstrates the development of recyclable organic–inorganic hybrid TBAI@CuO catalyst containing quaternary ammonium (TBAI) salt as active organic groups and CuO flowers as the inorganic component. Initially, CuO flowers was synthesized using a simple oxidation-precipitation method followed by immobilization of TBAI groups using impregnation method. The impregnated TBAI groups functioned as the active basic centers, whereas CuO flowers with effective surface area provided heterogeneity, Lewis acidic sites, facilitated better dispersion and strong interaction of TBAI. Resultantly, hybrid TBAI@CuO catalyst consisted of dual-active sites which played a decisive role in manipulating catalytic activity without requirement of a co-catalyst. With styrene oxide and CO2 as model substrates, the present catalyst system delivered 95% conversion and 97% selectivity towards styrene carbonate under solvent-free and milder reaction conditions when compared to other single metal oxide catalysts. The homogeneously dispersed TBAI groups in strong interaction with CuO flowers provided simultaneous access to both Lewis acidic as well as basic sites and hence resulted in superior catalytic activity. Meanwhile, hybrid TBAI@CuO catalyst showed catalytic adequacy for various terminal and internal epoxides. This catalytic system also presented good reusability without prominent loss in activity and no leaching of active TBAI groups. Based on characterization results, a plausible reaction mechanism was predicted to support the cycloaddition reaction with hybrid TBAI@CuO catalyst. It was proposed that inorganic Lewis acidic CuO activated the epoxide whereas the immobilized TBAI groups activated the inert CO2 molecule and stabilized the epoxide after ring opening. Therefore, the CuO flowers acting in concert with the immobilized TBAI groups showed exceptional acid–base cooperativity and provided high selectivity towards cyclic carbonates. The hybrid TBAI@CuO catalyst in this effort bridges the gap between homogeneous and heterogeneous catalysis for sustainable transformation of CO2 and epoxides to cyclic carbonates under solvent-free and comparatively mild reaction conditions [ABSTRACT FROM AUTHOR]

Background: Germ cell tumors (GCTs) represent the most frequent solid malignancy in young men. This malignancy is highly curable by cisplatin (CDDP)-based chemotherapy. However, there is a proportion of patients having a poor prognosis due to refractory disease or its relapse. No reliable biomarkers being able to timely and accurately stratify poor prognosis GCT patients are currently available. Previously, we have shown that chemotherapy-naïve GCT patients with higher DNA damage levels in peripheral blood mononuclear cells (PBMCs) have significantly worse prognosis compared to patients with lower DNA damage levels. Methods: DNA damage levels in PBMCs of both chemotherapy-naïve and first cycle chemotherapy-treated GCT patients have been assessed by standard alkaline comet assay and its styrene oxide (SO)-modified version. These levels were correlated with clinico-pathological characteristics. Results: We re-confirm prognostic value of DNA damage level in chemotherapy-naïve GCT patients and reveal that this prognosticator is equally effective in GCT patients after first cycle of CDDP-based chemotherapy. Furthermore, we demonstrate that SO-modified comet assay is comparably sensitive as standard alkaline comet assay in case of patients who underwent first cycle of CDDP-based chemotherapy, although it appears more suitable to detect DNA cross-links. Conclusion: We propose that DNA damage levels in PBMCs before and after first cycle of CCDP-based chemotherapy are comparable independent prognosticators for progression-free and overall survivals in GCT patients. Therefore, their clinical use is highly advised to stratify GCT patients to identify those who are most at risk of developing disease recurrence or relapse, allowing tailoring therapeutic interventions to poor prognosis individuals, and optimizing their care management and treatment regimen. [ABSTRACT FROM AUTHOR]

Developing a highly efficient and environmentally friendly catalytic system for CO2 cycloaddition reactions is an attractive way to achieve carbon neutrality. In this work, tetrabutylammonium iodide (TBAI) and polyethylene glycol (PEG) were used to produce novel deep eutectic solvents (DESs), which could serve as both solvents and catalysts, displaying excellent activity to synthesis styrene carbonates from CO2 and styrene oxide under metal‐free, cocatalyst‐free, solvent‐free and mild conditions. A detailed study was undertaken on the effects of reaction parameters, recyclability, and substrate scope. Additionally, the H‐bond interaction between the substrate and TBAI/PEG200 was thoroughly investigated using FT‐IR and 1H NMR techniques. The synergistic interaction between the two components of the DES, TBAI, and PEG200, may be the key to the high catalytic activity of this system. The tetrabutylammonium iodide‐based system is an innovative strategy for the CO2 cycloaddition with epoxides, achieved by elaborately devising the H‐bonds of DESs to enhance reactivity. This provides a novel green strategy for potential industrial applications. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations at the M062X-D3/def2-TZVP//M062X-D3/def2-SVP level of theory were employed to reveal the mechanism of the reaction between CO2 and styrene oxide for cyclic carbonate, mediated by guanidine and tetrabutylammonium iodide (TBAI) co-catalysts. The noncatalytic reaction occurred via a concerted mechanism, with energy barriers as high as 64.1 and 78.0 kcal mol−1. Three elementary steps were included in the catalytic reaction, and epoxide ring-opening by nucleophilic attack of an iodide anion was predicted to be the rate-determining step (RDS). Guanidine acted as the H-bond donor to activate styrene oxide by (N)H⋯O interaction, facilitating epoxide ring-opening with a low activation barrier (ΔG≠ = 22.2–29.6 kcal mol−1). A good linear correlation between the acidity of the NH group in the guanidine and the energy barrier in the epoxide ring-opening step was observed. The introduction of an amide group could strengthen the hydrogen bonding ability of the guanidine catalyst toward a styrene oxide substrate, decreasing the activation barrier for the cyclic carbonate product. When the guanidine–Cu(I) complex was used as the Lewis acid catalyst, the styrene oxide was activated by O⋯Cu(I) coordination in organometallic catalysis. The energy barriers in the presence of guanidine–Cu(I)/TBAI catalysts could be decreased in contrast to the non-catalytic reaction. [ABSTRACT FROM AUTHOR]

Precise design of highly efficient, low metal load and eco‐friendly catalysts is the key to sustainable catalysis and green chemistry. In this work, we develop an ultra‐low loading of Mn(salen) complexes covalent grafted with lignin and applied in the selective epoxidation of olefins using O2 as an oxidant. Lignin not only provides the Mn(salen) graft sites but also promotes substrate enrichment via the π‐stacking interaction between substrate and supports. In particular, high turnover frequencies (TOF) of 1833 h−1 can be obtained for styrene epoxidation under mild conditions, which can be superior to most reported Mn(salen) supported catalysts. Compared with cellulose, the lignin‐based catalysts exhibit a higher selectivity toward styrene oxide during the epoxidation of styrene under mild conditions. Controlled experiments indicate that the synergistic effect between phenolic hydroxyl groups and the Mn(salen) complex can improve the conversion rate and selectivity during the selective epoxidation of styrene. This work designs a series of lignin‐based catalysts with ultra‐low Mn(salen) loading, which broadens the utilization of lignin and gives enlightenment for the rational design of lignin‐based catalysts. [ABSTRACT FROM AUTHOR]

Inexpensive dyes available at the industrial scale, namely, rhodamine B (RhB), rhodamine 6G (Rh6G) and methylene blue (MB), were investigated as organocatalysts for the cycloaddition of CO2 to styrene oxide to yield styrene carbonate under solvent-free conditions (80 °C, 10 bar CO2, 24 h). Each of these dyes consists of a bulky cation, and a chloride anion that can act as a nucleophilic catalytic species in the target reaction. In order to prepare additional catalysts, the Cl− containing dyes were ion-exchanged with KX (X = Br, I) to afford their counterparts with Br− or I− as the anion. Among this set of nine organocatalysts (three dyes, each with three types of halide), the highest yield of styrene carbonate was obtained with Rh6G-I, and trends were identified based on the nature of the organic cation and halide, with the latter having a much larger impact on the activity (I− > Br− > Cl−). Additionally, we explored the effect of adding H2O as a green, inexpensive hydrogen bond donor acting as a co-catalyst, further optimising the styrene carbonate yield (96% with RhB-I and Rh6G-I in the presence of 50 mg H2O). However, the activity of these organocatalysts was only modest if the reaction temperature was decreased to 45 °C. To tackle this limitation, we designed a tailored yet straightforward modification of RhB-I to synthesise a bifunctional organocatalyst bearing a hydrogen bond donor in proximity of the iodide anion (RhB-EtOH-I). This strategy proved successful and the RhB-EtOH-I catalyst achieved a major increase in styrene carbonate yield (29% after 18 h at 45 °C, 10 bar CO2) compared to the RhB-I/H2O catalytic system (7%). The RhB-EtOH-I catalyst was also versatile and promoted the conversion of a broad scope of epoxides with good to high cyclic carbonate yields under relatively mild reaction conditions (60 °C, 10 bar, 24 h). Although these dye organocatalysts were homogeneous, RhB-EtOH-I could be easily recovered by precipitation with diethyl ether and reused without any loss of catalytic activity. Additionally, we demonstrated that nanofiltration was an effective technique for removing the dye organocatalysts from the cyclic carbonate, affording a high purity product (≤0.1 ppm of RhB in propylene carbonate). The metal-free nature of the optimum organocatalyst (RhB-EtOH-I), its facile preparation and the low cost and commercial availability of its precursors, its promising activity under mild reaction conditions and its reusability are all assets in the context of green chemistry and for potential large-scale applicability. [ABSTRACT FROM AUTHOR]

Inexpensive dyes available at the industrial scale, namely, rhodamine B (RhB), rhodamine 6G (Rh6G) and methylene blue (MB), were investigated as organocatalysts for the cycloaddition of CO2 to styrene oxide to yield styrene carbonate under solvent-free conditions (80 °C, 10 bar CO2, 24 h). Each of these dyes consists of a bulky cation, and a chloride anion that can act as a nucleophilic catalytic species in the target reaction. In order to prepare additional catalysts, the Cl− containing dyes were ion-exchanged with KX (X = Br, I) to afford their counterparts with Br− or I− as the anion. Among this set of nine organocatalysts (three dyes, each with three types of halide), the highest yield of styrene carbonate was obtained with Rh6G-I, and trends were identified based on the nature of the organic cation and halide, with the latter having a much larger impact on the activity (I− > Br− > Cl−). Additionally, we explored the effect of adding H2O as a green, inexpensive hydrogen bond donor acting as a co-catalyst, further optimising the styrene carbonate yield (96% with RhB-I and Rh6G-I in the presence of 50 mg H2O). However, the activity of these organocatalysts was only modest if the reaction temperature was decreased to 45 °C. To tackle this limitation, we designed a tailored yet straightforward modification of RhB-I to synthesise a bifunctional organocatalyst bearing a hydrogen bond donor in proximity of the iodide anion (RhB-EtOH-I). This strategy proved successful and the RhB-EtOH-I catalyst achieved a major increase in styrene carbonate yield (29% after 18 h at 45 °C, 10 bar CO2) compared to the RhB-I/H2O catalytic system (7%). The RhB-EtOH-I catalyst was also versatile and promoted the conversion of a broad scope of epoxides with good to high cyclic carbonate yields under relatively mild reaction conditions (60 °C, 10 bar, 24 h). Although these dye organocatalysts were homogeneous, RhB-EtOH-I could be easily recovered by precipitation with diethyl ether and reused without any loss of catalytic activity. Additionally, we demonstrated that nanofiltration was an effective technique for removing the dye organocatalysts from the cyclic carbonate, affording a high purity product (≤0.1 ppm of RhB in propylene carbonate). The metal-free nature of the optimum organocatalyst (RhB-EtOH-I), its facile preparation and the low cost and commercial availability of its precursors, its promising activity under mild reaction conditions and its reusability are all assets in the context of green chemistry and for potential large-scale applicability. [ABSTRACT FROM AUTHOR]

Tandem catalysis as an exciting research frontier has recently aroused wide attention due to the eliminated intermediate work-up, improved production efficiency, decreased production cost and reduced waste discharge. The main challenge in this tandem catalytic approach is the exploiting of a bifunctional catalyst that can be effective for both reactions processed under the same reaction conditions in a single reactor. We herein report for the first time that in the presence of in-situ generated Co3O4/CuCo2O4 heterostructures (CCHS) as a heterogeneous catalyst, α-methoxyphenylacetic acid (MTPAA) can be produced via tandem catalysis from styrene and methanol by integrating the styrene epoxidation and subsequent nucleophilic ring-opening of styrene oxide (SO). The styrene conversion of 94.8% accompanied with a selectivity of 62.5% to MTPAA was achieved under the optimal reaction conditions. Consequently, a simple heterogeneous approach for the highly efficient and selective production of MTPAA has been established. This study highlights the great potential of bifunctional heterostructures composed of earth-abundant elements for the synthesis of valuable chemicals via tandem conversion of styrene and subsequent diverse SO ring-opening reactions. In the presence of in-situ generated Co3O4/CuCo2O4 heterostructures as a heterogeneous catalyst, α-methoxyphenylacetic acid can be produced via tandem catalysis from styrene and methanol by integrating the styrene epoxidation and subsequent nucleophilic ring-opening of styrene oxide. [ABSTRACT FROM AUTHOR]

Developing a simple and efficient heterogeneous catalyst for the cycloaddition of epoxides with CO2 under atmospheric pressure and cocatalyst-/metal-/solvent-free conditions remains a great challenge. Herein, poly(ionic liquid)s (P-[VRIm]Br-crosslinker-x) with unique adsorption-swelling ability toward epoxides are designed and facilely synthesized via free radical polymerization in water. The adsorption-swelling of epoxides by P-[VRIm]Br-crosslinker-x is controllable, reversible, and widespread, resulting from the strong interactions between the poly(ionic liquid)s and epoxide molecules, especially the hydrogenbonding interaction. Superior CO2 cycloaddition is realized in the P-[VRIm]Br-crosslinker-x catalyst through the adsorption-swelling effect. Specifically, P-[VC6Im]Br-C8-5% with 54.1 mmol g-1 adsorptionswelling ability toward styrene oxide achieves 89.3% yield and >99% selectivity in the cycloaddition of styrene oxide with CO2 to styrene carbonate under mild conditions (1 atm, 80 °C) without cocatalyst/metal/solvent consumption. Moreover, P-[VC6Im]Br-C8-5% can be easily recovered by deswelling, and shows good reusability and stability after five cycles for a total of 180 h. The adsorption-swelling property of P-[VRIm]Br-crosslinker-x to epoxides not only prompts the active centers to be fully exposed to the reactants but also induces the enrichment of epoxides during the whole catalytic process, thus accelerating the CO2 cycloaddition reaction rate. This work furnishes new insights for improving the activity of CO2 cycloaddition and would guide the design of efficient poly(ionic liquid) catalysts for atmospheric CO2 conversion. [ABSTRACT FROM AUTHOR]

[17] Our research group recently reported [17] the synthesis of 2,3-diarylquinolines using 10 mol% Cu(OTf) SB 2 sb in DMSO from arylamines, styrene oxide, and benzaldehyde. Arylamines, styrene oxides, aromatic aldehydes, 2,3-diaryl quinolines, environmentally benign synthesis, p -TSA-H 2 O, atomic economy, three-component reaction Keywords: arylamines; styrene oxides; aromatic aldehydes; 2,3-diaryl quinolines; environmentally benign synthesis; p -TSA-H 2 O; atomic economy; three-component reaction EN arylamines styrene oxides aromatic aldehydes 2,3-diaryl quinolines environmentally benign synthesis p -TSA-H 2 O atomic economy three-component reaction 3195 3203 9 09/11/23 20231004 NES 231004 Graph In recent times, multicomponent reactions approach has emerged as an important synthetic tool in modern organic chemistry for the total synthesis of natural products and synthetic building blocks. To further check the practicability of this protocol, the reaction was carried out at a 10 mmol scale with 3,4-dimethoxy aniline ( B 1a b ), benzaldehyde ( B 2a b ), and styrene oxide ( B 3a b ), under identical reaction conditions. [Extracted from the article]

Palladium nanoparticles on ethylenediamine-grafted functionalized chromium-based metal organic framework (Pd-ED-MIL-101) was tested for the hydrogenation of styrene oxide to 2-phenylethanol, the key ingredient of the rose essence. The catalyst was found as an excellent heterogeneous recyclable catalyst for selective hydrogenation of styrene oxide to 2-phenylethanol (100% conversion and ∼100% selectivity) within 2 h in methanol with a catalyst loading only 0.25 mol % palladium at ambient pressure and temperature under molecular hydrogen. If the catalyst loading increases to 0.50 mol % palladium, the conversion time reduces to 1 h. In repeated runs (tested for 5 cycles) showed no loss of activity and selectivity of the catalyst. To the best of our knowledge, the performance of the present catalyst is one of the best compared to all other reported catalysts in terms of conversion, selectivity, reaction time, reaction conditions, purification, catalyst stability, catalyst loading, catalyst recyclability, safety and convenience. [ABSTRACT FROM AUTHOR]

Toxicity assessment is a major problem in pharmaceutical candidates and industry chemicals development. However, due to the lack of practical analytical methods for DNA adduct analysis, the safety evaluation of drug and industry chemicals was severely limited. Here, we develop a DNAzyme-based method to detect DNA adduct damage for toxicity assessment of drugs and chemicals. Among 18 structural variants of G4 DNAzyme, EA2 DNAzyme exhibits an obvious DNA damaging effect of styrene oxide (SO) due to its unstable structure. The covalent binding of SO to DNAzyme disrupts the Hoogsteen hydrogen bonding sites of G-plane guanines and affects the formation of the G4 quadruplex. DNA damage chemicals reduce the peroxidase activity of the G4 DNAzyme to monitor the DNA adduct damage by disrupting the structural integrity of the G4 DNAzyme. Our method for genotoxic assessment of pharmaceutical candidates and industrial chemicals can elucidate the complex chemical pathways leading to toxicity, predict toxic effects of chemicals, and evaluate possible risks to human health.

A non-porous version of SU-101 (herein n-SU-101) was evaluated for the CO2 cycloaddition reaction. The findings revealed that open metal sites (Bi3+) are necessary for the reaction. n-SU-101 displays a high styrene oxide conversion of 96.6% under mild conditions (3 bar and 80 °C). The catalytic activity of n-SU-101 demonstrated its potential application for the cycloaddition of CO2 using styrene oxide. [ABSTRACT FROM AUTHOR]

Application of a binary Ga‐based catalyst system for the coupling of CO2 and aziridines to form oxazolidinones is presented. It has been possible to optimize the catalyst system for the selective formation of a single regioisomer, in excellent yield, under relatively mild reaction conditions. The optimized catalyst system has been successfully applied to a range of substituted aziridines derived from styrene oxide. It has been observed that aziridines bearing two aromatic substituents result in piperazine formation through an unexpected dimerization reaction. These piperazine products can be selectively formed in the absence of CO2 or are favored at lower reaction temperatures. A detailed DFT study into the reaction mechanism for the formation of both products has been carried out and an unusual ligand assistance in the case of oxazolidinone synthesis has been identified. More specifically, this ligand interaction promotes the initial ring‐opening of the aziridine and this work presents the first fully elucidated mechanism involving this intermediate. [ABSTRACT FROM AUTHOR]

The development of catalysts that can selectively and efficiently promote the alkene epoxidation at ambient temperatures and pressures is an important promising path to renewable synthesis of various chemical products. Here we report a new type of zerovalent atom catalysts comprised of zerovalent Ir atoms highly dispersed and anchored on graphdiyne (Ir0/GDY) wherein the Ir0 is stabilized by the incomplete charge transfer effect and the confined effect of GDY natural cavity. The Ir0/GDY can selectively and efficiently produce styrene oxides (SO) by electro-oxidizing styrene (ST) in aqueous solutions at ambient temperatures and pressures with high conversion efficiency of ∼100%, high SO selectivity of 85.5%, and high Faradaic efficiency (FE) of 55%. Experimental and density functional theory (DFT) calculation results show that the intrinsic activity and stability due to the incomplete charge transfer between Ir0 and GDY effectively promoted the electron exchange between the catalyst and reactant molecule, and realized the selective epoxidation of ST to SO. Studies of the reaction mechanism demonstrate that Ir0/GDY proceeds a distinctive pathway for highly selective and active alkene-to-epoxide conversion from the traditional processes. This work presents a new example of constructing zerovalent metal atoms within the GDY matrix toward selective electrocatalytic epoxidation. [ABSTRACT FROM AUTHOR]

Introducing organic groups into metal silicate catalysts and thus supposedly changing the surface hydrophobicity has been shown to enhance the catalyst performance in various reactions. However, the organic groups introduction does not unambiguously guarantee hydrophobicity control. Therefore, a thorough characterization is necessary to provide a complete view of the interaction between the catalyst surface, reactants, and products. Herein, an aluminosilicate catalyst with well‐dispersed Al atoms was prepared via the non‐hydrolytic sol‐gel method. This material was post‐synthetically modified with trimethylsilyl groups; their number on the catalyst surface was controlled via a temperature‐vacuum pretreatment. In such a way, aluminosilicate materials with similar porosity, structure, and acid site strength and quality were obtained. Notably, the water sorption measurements showed that trimethylsilylated aluminosilicates adsorb 2.5–3 times less water than the parent material (p/p0=0.3). The turn‐over‐frequency in epoxide ring opening and ethanol dehydration scaled up with the number of trimethylsilyl groups grafted on the catalyst surface. Particularly, the heavily trimethylsilylated sample achieved three to five times higher turnover‐frequency in styrene oxide aminolysis than the parent aluminosilicate material. To the best of the authors' knowledge, it exhibited the most active Al sites for epoxide aminolysis in the present literature. [ABSTRACT FROM AUTHOR]

A new biocatalyst MP8@MIL‐101(Cr/Fe) was prepared by immobilization of a heme octapeptide, Microperoxidase 8 (MP8) within a mixed metal MOF, MIL‐101(Cr/Fe). Both MIL‐101(Cr/Fe) and MP8@MIL‐101(Cr/Fe) were characterized by PXRD, FTIR spectroscopy and TGA. The catalytic activity of MP8@MIL‐101(Cr/Fe) for the oxidation of styrene by H2O2 and tBuOOH was then examined under various reaction conditions (nature of the co‐solvent and of the oxidant, concentration of the oxidant and of the substrate, time, pH) and compared to that of MP8 alone. Under the best conditions used, MP8@MIL‐101(Cr/Fe) was then shown to catalyze the oxidation of styrene about 3 times more efficiently than MP8 alone with approximately 50 % selectivity for styrene oxide. [ABSTRACT FROM AUTHOR]

Abstract Background (R)-mandelic acid (R-MA) is a highly valuable hydroxyl acid in the pharmaceutical industry. However, biosynthesis of optically pure R-MA remains significant challenges, including the lack of suitable catalysts and high toxicity to host strains. Adaptive laboratory evolution (ALE) was a promising and powerful strategy to obtain specially evolved strains. Results Herein, we report a new cell factory of the Gluconobacter oxydans to biocatalytic styrene oxide into R-MA by utilizing the G. oxydans endogenous efficiently incomplete oxidization and the epoxide hydrolase (SpEH) heterologous expressed in G. oxydans. With a new screened strong endogenous promoter P 12780 , the production of R-MA was improved to 10.26 g/L compared to 7.36 g/L of using P lac . As R-MA showed great inhibition for the reaction and toxicity to cell growth, adaptive laboratory evolution (ALE) strategy was introduced to improve the cellular R-MA tolerance. The adapted strain that can tolerate 6 g/L R-MA was isolated (named G. oxydans STA), while the wild-type strain cannot grow under this stress. The conversion rate was increased from 0.366 g/L/h of wild type to 0.703 g/L/h by the recombinant STA, and the final R-MA titer reached 14.06 g/L. Whole-genome sequencing revealed multiple gene-mutations in STA, in combination with transcriptome analysis under R-MA stress condition, we identified five critical genes that were associated with R-MA tolerance, among which AcrA overexpression could further improve R-MA titer to 15.70 g/L, the highest titer reported from bulk styrene oxide substrate. Conclusions The microbial engineering with systematic combination of static regulation, ALE, and transcriptome analysis strategy provides valuable solutions for high-efficient chemical biosynthesis, and our evolved G. oxydans would be better to serve as a chassis cell for hydroxyl acid production.

In this work, a series of new lignin-graft copolymers were successfully prepared through enzymatic hydrolytic lignin (EHL)-initiated ring-opening alternating copolymerization of 3,4-dihydrocoumarin (DHC) and epoxides (EPO) through organocatalysis. A series of EPOs, including styrene oxide (SO), propylene oxide (PO), cyclohexane oxide (CHO) and lignin-derived-2-(2-methoxy-4-methyl-phenoxy) (MPO), together with DHC, were selected as model compounds to prepare EHL-g-P(DHC-alt-EPO), demonstrating the tailor-made potential of this synthetic protocol. The reaction conditions were optimized and the structures and thermal properties of EHL-g-P(DHC-alt-EPO) were fully elucidated by 1H, 13C and 31P NMR, FTIR spectroscopy, MALDI-TOF MS and GPC, DSC, and TGA. It was found that EHL-g-P(DHC-alt-SO) with a monomer conversion of 81.52%, DP of 3.21 and Mn of 62.9 kDa was prepared at a molar ratio of 5 : 5 : 1, 140 °C and 24 h. The UV shielding properties, antioxidant activity and biocompatibility of the as-prepared EHL-g-P(DHC-alt-EPO) was systematically evaluated. As a 'proof of concept' application, the potential of EHL-g-P(DHC-alt-SO) as an active ingredient in sunscreen was demonstrated, and a high sun protection factor (SPF) of 22.42 was achieved at 5 wt% dosage of EHL-g-P(DHC-alt-SO) in the cream, and the possible mechanism for the outstanding performance is also discussed. [ABSTRACT FROM AUTHOR]

Styrene oxide isomerase (SOI) catalyzes the Meinwald rearrangement of aryl epoxides to carbonyl compounds via a 1,2‐trans‐shift in a stereospecific manner. A number of cascade biotransformations with SOI‐catalyzed epoxide isomerization as a key step have been developed to convert readily available substrates into valuable chiral chemicals. Cascade conversion of terminal or internal alkenes into chiral acids, alcohols or amines was achieved, which involved SOI‐catalyzed enantio‐retentive isomerization of terminal epoxides via 1,2‐H shift, or internal epoxides via 1,2‐methyl shift. SOI‐involved cascades were also developed to convert racemic epoxides into chiral acids or amines via dynamic kinetic resolution. Additionally, combining SOI‐catalyzed isomerization with enantioselective C−C bond forming enzymes enabled the synthesis of chiral amino acids or amino alcohols from racemic epoxides. Finally, integration of SOI‐involved cascades with biosynthesis pathways allowed for the direct utilization of renewable substrates for the sustainable synthesis of high‐value natural chemicals such as alcohols, acids, and esters. [ABSTRACT FROM AUTHOR]

A series of benzoylacetone‐imine ligands, PhCOCHCMeNHR (L1H, R = CH2Ph; L2H, R = CH2Ph‐4‐Me; and L3H, R = CH2Ph‐4‐OMe), are first synthesized following the condensation of benzoylacetone and 4‐substituted benzylamine. Later, reacting L1H–L3H with one equivalent of AlMe3 in toluene, the monomeric Al derivatives are generated, (PhCOCHCMeNR)AlMe2 (1, R = CH2Ph; 2, R = CH2Ph‐4‐Me; 3, R = CH2Ph‐4‐OMe). All the ligands and metal derivatives are characterized by 1H and 13C NMR spectroscopy. Single crystal X‐ray diffraction analysis reveals the geometry of all ligands and complex 2. As supporting catalysts, the Al derivatives, 1–3, are effective to initiate the coupling of CO2 and styrene oxide to form cyclic carbonates. Although employing TBAI (tetra‐n‐butylammonium iodide), TBAC, tetrabutylammonium chloride, and TBAB (tetra butyl ammonium bromide) as cocatalyst, the optimized catalytic system exhibits the best conversion of epoxide in presence of TBAI under the reaction temperature and time, respectively, 90°C and 6 hr, respectively. The ring opening polymerization of ε‐caprolactone is also appraised subjecting the Al derivatives, 1–3, as catalysts in presence of benzyl alcohol and all the conversions of ε‐caprolactone reach over 95% at the reaction condition of 100°C and 1 hr. [ABSTRACT FROM AUTHOR]

Novel tridentate N2O‐type ligands L1–L4 (((((X‐benzyl)pyridine‐2‐yl)methylamino)methyl)phenol); L1 for X=4‐CH3, L2 for X=H, L3 for X=2‐F, L4 for X=4‐CF3) and their dinuclear copper(II) complexes C1–C4 (C1 for [(L1)2Cu2(NO3)2], C2 for [(L2)2Cu2(NO3)2], C3 for [(L3)2Cu2(NO3)2] and C4 for [(L4)2Cu2(NO3)2]) was synthesized and verified by 1H NMR, IR, and ESI‐Mass. The structural forms of the copper complexes were determined by X‐ray crystallography. The dinuclear copper complexes C1–C4 showed efficient ring‐opening properties of epoxides with methanol under mild conditions. In particular, the copper complex C1 having electron‐donating group in the ligand showed the most efficient reactivity in the ring opening of epoxides. The sole attack at the benzylic carbon of styrene oxide and the less steric preference in 1,2‐epoxyhexane demonstrated that the regiochemistry of the ring opening catalyzed by dinuclear copper complexes might be dependent on the electronic feature of epoxide. [ABSTRACT FROM AUTHOR]

Herein, we present the synthesis of three new neutral aryl-BIAN ZnCl2 complexes (where aryl-BIAN = bis(aryl-imino)acenaphthene) with formulations [Zn(4-iPrC6H4-BIAN)Cl2] (1), [Zn(2-iPrC6H4-BIAN)Cl2] (2) and [Zn(4-NO2C6H4-BIAN)Cl2] (3) obtained through a green synthesis methodology. Compounds 1 and 2 were fully characterized by elemental analysis, ESI-LS mass spectrometry, FT-IR ATR mode, and multinuclear NMR spectroscopic techniques. Compound 3 was characterized by elemental analysis, ESI-LS mass spectrometry and FT-IR, ATR mode. The solid-state molecular structures of compounds 1 and 2 were determined by single crystal X-ray diffraction. The new complexes 1, 2 and 3, and the known complexes of formulations [Zn(2,6-iPr2C6H3-BIAN)Cl2] (4) and [Zn(2,4,6-Me3C6H2-BIAN)Cl2] (5) were tested as catalysts in the cycloaddition reaction of CO2 and epoxides using the tetrabutylammonium bromide salt as a co-catalyst. Primary studies revealed that complex 4 presented the highest catalytic activity among all synthetized complexes. Good reaction TOFs were obtained for the conversion of propylene oxide (112 h−1) after 3 hours and for the conversion of styrene oxide (23 h−1) after 8 hours, at 4 MPa and 333 K. For more sterically hindered cyclohexene oxide, no cyclic carbonate formation was observed, under the same operational conditions. Furthermore, the effect of reaction time (1–40 h), pressure (0.5–40 MPa) and nucleophile to metal ratio (0.5–100) on final cyclic carbonate formation was investigated. [ABSTRACT FROM AUTHOR]