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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]

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]

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]

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]

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]

To produce metal-organic framework (MOF) catalysts with both high activity and durability is interesting but challenging. We report an amorphous MOF (NH2-MIL-68), which combines the advantages of (1) a large number of open metal sites, (2) the basic building blocks and connectivity of crystalline NH2-MIL-68, and (3) hierarchically meso- and microporous structure. It exhibits high performances in electrocatalytic reduction of CO2 and photochemical cycloaddition of CO2 under mild conditions. For the former reaction, the maximum Faradaic efficiency for product formic acid (FEHCOOH) reaches 93.3% with a current density of 34.2 mA·cm−2 at −2.05 V vs. Ag/Ag+ catalyzed by amorphous NH2-MIL-68, while the crystalline NH2-MIL-68 shows FEHCOOH of 67.7% with considerable productions of CO and H2 at the same experimental conditions. For the photochemical cycloaddition of CO2 with styrene oxide, the yield by amorphous NH2-MIL-68 can reach 94.1% at 12 h, which is higher than the reported value under similar conditions. The structure—efficiency relationship of the catalyst for the two reactions was investigated. This work opens up new possibility for designing high-performance MOF and MOF-based catalysts. [ABSTRACT FROM AUTHOR]

Pyridinium halide modified MCM-41 was used as a catalyst for the model reaction of styrene oxide with carbon dioxide. The modification was performed in two steps—first, the modification of MCM-41 by halogenopropyl triethoxy silane followed by the reaction with pyridine. The process was successful for the production of pyridinium bromide and iodide. The modification by chlorine was problematic. The prepared materials were characterized by available methods—XRF, XRD, EA, TPH, DVS, FTIR, UV/Vis, TGA, and nitrogen physisorption—confirming the successful formation of the desired material. For the catalysis, the strong interaction of pyridinium ion was necessary. The prepared materials containing bromine and iodine were used as efficient catalysts for the formation of styrene carbonate from styrene oxide. The achieved selectivity was up to 99% with TONs 5800 (calculated on the amount of loaded pyridine) under 1.2 MPa, 120 °C, without any solvent. Solvents negatively influenced the reaction rate. Dependently on halogen, the rate increased in the row Cl < Br < I modified MCM-41. The catalysts might be reused with only a slight loss of activity in the three following cycles. These materials represent simple, available, and promising catalysts for the reaction of epoxides with carbon dioxide. [ABSTRACT FROM AUTHOR]

We describe a system that allows for biocatalyzed in vivo synthesis of α-hydroxy ketones from racemic epoxide starting material by in vivo co-expression of native and engineered epoxide hydrolase and alcohol dehydrogenases. The constructed expression system exploits the host cell metabolism for supply and regeneration of precious nicotinamide dinucleotide coenzyme. Racemic styrene oxide added to growth medium passively enters the cells and is hydrolyzed into (1R)-phenylethane-1,2-diol, which is subsequently oxidized to the acyloin 2-hydroxyacetophenone. Produced 2-hydroxyacetophenone escapes the cells via passive diffusion into the growth medium. Thus, co-expression of potato epoxide hydrolase and engineered alcohol dehydrogenase variants can be employed for robust and facile production of 2-hydroxyacetophenone from racemic styrene oxide. [ABSTRACT FROM AUTHOR]

Three new guanylated cyclophosphazenes G1–G3 have been synthesized through the catalytic guanylation of three different bi, tetra and hexa (p-aminophenoxy)-cyclophosphazenes by using N,N'-diisopropylcarbodiimide as guanylating agent, ZnEt2 as catalyst and dry tetrahydrofuran as solvent. The resulting products have been characterized by 1H, 13C{1H} and 31P{1H} NMR spectroscopy. The hexaguanylated cyclophosphazenes exhibit a deep purple colour, unusual for this type of compounds. The electronic structure of these compounds was investigated by carrying out density functional calculations at PBE-D3(BJ)/TZP level of theory. The molecular structural analysis reveals that aromatic rings are stacked and time dependent density functional calculations show that a charge transfer electronic transition occurs between the aromatic rings which absorb light around 500–700 nm. Finally, the catalytic usefulness of guanylated cyclophosphazene compounds G1–G3 has been proven by the preparation of styrene carbonate from the reaction between styrene oxide and carbon dioxide. [ABSTRACT FROM AUTHOR]

A condensed excited matter called Rydberg Matter (RM) have been studied experimentally for 30 years, but have not sparked widespread attention yet, unlike ordinary Rydberg atoms. RM formed by clusters of Rydberg atoms at a solid surface have a longer lifetime compared to Rydberg atoms, and is liquid-like. This review describes how the RM state is generated, and its potential applications. These include using RM for research into catalysis, space phenomena and sensor applications, or for producing environmentally friendly energy. A background on RM is presented, with its structure and special properties, and the working principle of RM generation. The experimental set-ups, materials, and detectors used are discussed, together with methods to improve the amount of RM produced. The materials used for the catalysts are of special interest, as this should have a large influence on the energy of the RM, and therefore also on the applications. Currently most of the catalysts used are potassium doped iron oxide designed for styrene production, which should give the possibility of improvements. And as there is little knowledge on the exact mechanisms for RM formation, suggestions are given as to where research should start. [ABSTRACT FROM AUTHOR]

Cycloadditions of epoxides and carbon dioxide into corresponding cyclic carbonates were performed over mesoporous Ta–W composite oxides prepared by a modified hydrolytic method. The best yields of styrene carbonate were obtained when the Ta/W mole ratio was 2:1 (labeled as Ta0.67W0.33Os). Under optimal reaction conditions, the conversion of styrene oxide and selectivity of styrene carbonate reached 95 and 97%, respectively. These Ta–W composite oxides have been extensively characterized by several techniques. X-ray diffraction (XRD) patterns and Transmission Electron Microscope (TEM) revealed that Ta2O5 was completely dispersed in WOx. Scanning electron microscopy (SEM) exhibited that the particle size distributions become more and more uniform with increment of tungsten content. CO2 and NH3 temperature-programmed desorption (CO2 and NH3-TPD) revealed that Ta0.67W0.33Os catalyst had the strongest acid and base strength. X-ray photoelectron spectroscopy (XPS) shows that the strongest acid–base sites of Ta0.67W0.33Os catalyst origin from its highest lattice oxygen concentration and W 4f5/2 species with Bronsted acidity. We discussed the reaction kinetics and proposed a possible mechanism, indicating the excellent catalytic activity is attributed to the cooperative action of acidic and neighboring basic sites on the catalyst surface. Cycloaddition reactions of carbon dioxide with epoxides into corresponding cyclic carbonates were performed over mesoporous Ta–W composite oxides prepared by a modified hydrolytic method. The best yields for cyclic carbonates were obtained when the Ta/W mole ratio was 2:1 (denoted as Ta0.67W0.33Os). Acid-base synergy, specific surface area and mesoporous structure could be ascribed to the main reasons for the highest catalytic activity of Ta0.67W0.33Os catalyst. Meanwhile, reaction kinetics was discussed and a possible reaction pathway was proposed. [ABSTRACT FROM AUTHOR]

Three dimensional (3D) cubic cage like Im3m mesoporous SBA-16 was synthesized by one pot hydrothermal method using Pluronic F127 as structure directing agent and Tetraethylorthosilicate as silica precursor. Different weight percentages (1 wt%, 3 wt% and 5 wt%) of manganese nitrate tetrahydrate were homogeneously mixed with the same weight percentages of ammonium tungsten oxide hydrate respectively and dispersed on SBA-16 by incipient wet impregnation method. Structural identification and the particle arrangement for as-synthesized SBA-16 materials were analyzed using low and high angle X-ray diffraction. Surface area, pore-diameter, pore volume and pore size distribution were observed using the N2 adsorption isotherm technique with H2 hysteresis loop. The topography of the catalyst was characterized by TEM. The chemical valence state and elemental composition were characterized by high-resolution XPS respectively. The thermal stability of the catalyst was characterized by Thermogravimetric analysis. The synthesized materials MnWO4/SBA-16 were tested for epoxidation of styrene with environmentally benign TBHP as an oxidant. Various parametric investigations were performed and reported. From the above investigation, it is inferred that the major product of styrene oxide was obtained with maximum selectivity of about 75% using MnWO4 (3 wt%)/SBA-16. [ABSTRACT FROM AUTHOR]

Selective photochemical oxidation of styrene was performed in an active acetonitrile medium, using H2O2 with or without ultraviolet (UV) light radiation. Pyrithione metal complexes (M–Pth: M = Cu(II), Ni(II), Ru(II); Pth = 2-mercaptopyridine-N-oxide) were used as catalysts. Catalytic testing measurements were done by varying the time, chemical reaction temperature and H2O2 concentration with or without UV energy. Epoxide styrene oxide (SO), benzaldehyde and acetophenone were the major synthesized products. A high batch rate, conversion and selectivity towards SO was shown in the presence of UV. A minor constant formation of CO2 was observed in the stream. Coordinated Ru-based compounds demonstrated the highest process productivity of SO at 60 °C. The effect of the functional alkyl substituent on the ligand Pth, attached to the specific ruthenium(II) centre, decreased the activity of the substance. Ni-Pth selectively yielded benzaldehyde. The stability of the catalysts was examined by applying nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis coupled with mass spectrometry. Tested metal complexes with pyrithione (M–Pth) exhibited excellent reuse recyclability up to 3 cycles. [ABSTRACT FROM AUTHOR]

Cesium hydroxide monohydrate (CsOH·H2O) activated by cation complexing agents, i.e., 18C6 or C222 was applied as initiator of monosubstituted oxiranes polymerization. Propylene oxide (PO), 1,2-butylene oxide (BO), styrene oxide (SO) and some glycidyl ethers were used as monomers. All processes were carried out in tetrahydrofuran solution at room temperature. Such polymers, as PPO-diols, PBO-diols and PSO-diols, are unimodal and have molar masses Mn = 2000–5100. Their dispersities are rather high (Mw/Mn = 1.17–1.33). Moreover, PPO-diols and PSO-diols are not contaminated by monools with unsaturated starting groups. Poly(glycidyl ether)s are, in general, polymodal. For example, poly(isopropyl glycidyl ether)-diols are bi- or trimodal, whereas poly(allyl glycidyl ether)-diols possess two or even six fractions. Molar masses of main fraction are 4200–6400, and the second fraction is much lower, namely 600–2600. Dispersities of some fractions are very low (Mw/Mn = 1.01–1.07). Polymodality of polymers obtained was discussed in terms of the formation of two or more species propagating with different rate constants. [ABSTRACT FROM AUTHOR]

This work describes the synthesis of magnetic graphene oxide (MGO), where iron oxide (Fe3O4) nanoparticles were uniformly deposited over the sheets of the graphene oxide (GO). Further, the introduction of aminopropyltrimethoxysilane (APTMS) on the surface of MGO was successfully done and results in the formation of amine-functionalized magnetic graphene oxide (MGO–NH2). The synthesized heterogeneous magnetic nanocomposite was characterized by numerous physicochemical and morphological techniques such as powder X-ray diffraction, Fourier transform infrared, thermogravimetric analysis, transmission electron microscopy, vibrating sample magnetometer, scanning electron microscopy, CHN analyzer, and energy-dispersive X-ray analysis. The synthesized nanocomposite was proved to be an effectual catalyst in the nucleophilic ring opening reactions of styrene oxide with derivatives of amines under green solvent. The present catalyst displayed good catalytic activity, short reaction time, higher regioselectivity, excellent yields and could be reutilized up to seven catalytic rounds with no substantial loss in its activity. The excellent properties of the catalyst are due to the dual character of acidic groups (existence of carboxyl groups on the sheet edges) and basic groups (amine groups anchored on the surface of GO). On completion of the reaction, the prepared nanocomposite could be effortlessly recovered from the reaction mixture by utilizing an external magnet, owing to the ferromagnetic property of Fe3O4. [ABSTRACT FROM AUTHOR]

The chemical fixation of CO2 into epoxides to afford cyclic carbonates has received considerable attention due to the 100% atom economy, which is in accordance with the concept of green chemistry and sustainable development. Here, we develop a facile and high-output strategy to fabricate cobalt phthalocyanine-based nanodots (CoPc-NDs) by the carbonization of citric acid and cobalt phthalocyanine complex. Due to the high thermal stability of phthalocyanine, the macrocycle is well preserved in the core of nanodots under the controlled hydrothermal temperature. The as-prepared CoPc-NDs disperse well in water with a nanoscale size about 70 nm. The morphology and chemical composition of CoPc-NDs are characterized by transmission electron microscopy, dynamic laser scattering, X-ray powder diffraction, X-ray energy spectrum, and absorption spectrum. Compared with the organometallic complex, such as cobalt tetra-nitrophthalocyanine and cobalt tetra-aminophthalocyanine, CoPc-NDs show better catalytic performance for the conversion of epoxides into carbonates. The kinetic experiments of three catalysts are investigated and compared under the same conditions using styrene oxide as substrate. Finally, a tentative mechanism for the catalysis was proposed and described. [ABSTRACT FROM AUTHOR]

Sphingorhabdus sp. YGSMI21, a novel microbial strain with an enantioselective epoxide hydrolase activity, was isolated from tidal samples contaminated by accidental oil spills subjected to enriched culture with polycyclic aromatic hydrocarbon. This strain was able to optically decompose (R)-styrene oxide (SO) and showed 100% optical purity. In addition, it showed a good enantioselectivity for the derivatives of (S)-SO, (S)-2-chlorostyrene oxide (CSO), (S)-3-CSO and (S)-4-CSO. For (S)-2-CSO, (S)-3-CSO and (S)-4-CSO, 99.9%ee was obtained with the yield of 26.2%, 24.8%, and 11.0%, respectively, when using 10 mg cells of Sphingorhabdus sp. YGSMI21 at pH 8.0 with 4 mM racemic substrates at pH 8.0 and 25°C. The values obtained in this study for (S)-2-CSO, particularly the yield of 26.2%, is noteworthy, considering that obtaining an enantiomerically pure form is difficult. Taken together, Sphingorhabdus sp. YGSMI21 can be regarded as a whole-cell biocatalyst in the production of various (S)-CSO with the chlorine group at a different position. [ABSTRACT FROM AUTHOR]

Chiral molecular recognition is a pivotal phenomenon in biomolecular science, governed by subtle balances of intermolecular forces that are difficult to quantify. Non-covalent interactions involving aromatic moieties are particularly important in this realm, as recurring motifs in biomolecular aggregation. In this work, we use high-resolution broadband rotational spectroscopy to probe the dynamic conformational landscape enclosing the self-pairing topologies of styrene oxide, a chiral aromatic system. We reach a definite assignment of four homochiral and two heterochiral dimers using auxiliary quantum chemistry calculations as well as structure-solving methods based on experimental isotopic information. A complete picture of the dimer conformational space is obtained, and plausible routes for conformational relaxation are derived. Molecular structures are discussed in terms of conformational flexibility, the concerted effort of weak intermolecular interactions, and their role in the expression of the molecular fit. Chiral molecular recognition is critical in many natural processes, but probing the conformational landscape of chiral aromatic systems can be challenging. Here, high-resolution broadband rotational spectroscopy data is combined with quantum chemical computations to reveal the dynamic self-pairing topologies of the chiral molecule styrene oxide. [ABSTRACT FROM AUTHOR]

Flower-like NiO microspheres with an average size of ⁓ 3 μm and nanoflakes size ⁓ 10–100 nm were synthesized by surfactant-assisted chemical precipitation method, using Ni(CH3CO2)2·4 H2O as a nickel source, diethanolamine as a complexing agent, and cetyltrimethylammonium bromide as a surfactant. The obtain material was characterized by SEM, EDX, HR-TEM, XRD, and TGA. The obtained results confirmed the formation of highly ordered flower-like NiO nanoparticles. The catalytic activity of the obtained material was evaluated in the epoxidation reaction of styrene under ambient conditions, using meta-chloroperoxybenzoic acid (m-CPBA) as an oxidant. The obtained results revealed an immediate conversion of styrene to styrene oxide, with high conversion (87%), medium selectivity (65%), and high turnover-frequency (TOF) (243 s−1). However, when bulk NiO was applied only 62% conversion with 68% selectivity and TOF = 174 s−1 were obtained. Furthermore, this catalyst is was easily separable and recyclable. Moreover, a possible reaction mechanism is also proposed. [ABSTRACT FROM AUTHOR]

The fast absorption of molecular oxygen by a system including styrene oxide, copper(II) chloride, and α-naphthol (strong inhibitor of oxidation) was found and studied by the volumetric method. A low value of the activation energy of oxidation and a complicated concentration dependence of the reaction rate indicate that the oxidation proceeds via the formation of a ternary system, possibly, via a complex of three reactants. The thermolabile activity of the copper catalyst of oxidation was found for the oxidation of this system in a 85 vol.% ButOH + + 15 vol.% H2O solution. [ABSTRACT FROM AUTHOR]

The synthesis of solid acids with strong zeolite-like acidity and textural properties like amorphous aluminosilicates (ASAs) is still a challenge. In this work, we report the synthesis of amorphous "acidic aluminosilicates (AAS)", which possesses Brønsted acidic sites like in zeolites and textural properties like ASAs. AAS catalyzes different reactions (styrene oxide ring-opening, vesidryl synthesis, Friedel−Crafts alkylation, jasminaldehyde synthesis, m-xylene isomerization, and cumene cracking) with better performance than state-of-the-art zeolites and amorphous aluminosilicates. Notably, AAS efficiently converts a range of waste plastics to hydrocarbons at significantly lower temperatures. A Cu-Zn-Al/AAS hybrid shows excellent performance for CO2 to fuel conversion with 79% selectivity for dimethyl ether. Conventional and DNP-enhanced solid-state NMR provides a molecular-level understanding of the distinctive Brønsted acidic sites of these materials. Due to their unique combination of strong acidity and accessibility, AAS will be a potential alternative to zeolites. The synthesis of solid acids with strong zeolite-like acidity and textural properties like amorphous aluminosilicates (ASAs) is still a challenge. Here the authors synthesized "acidic amorphous aluminosilicates", with Brønsted acidic sites like in zeolites and textural properties like ASAs for catalyzing various reactions. [ABSTRACT FROM AUTHOR]

In the present study, the cobalt (II) complex [Co-HMBED] has been prepared and characterized by spectrochemical techniques, which confirmed its square planar structure. The catalytic activity of the cobalt complex was evaluated towards solvent-free conversion of CO2 and styrene oxide into cyclic styrene carbonate and polymerization of lactide. This perspective describes the synthesis, characterization and catalytic studies of Co-HMBED complex; towards coupling of styrene oxide and CO2 to produce cyclic styrene carbonates and polymerization of lactide. [ABSTRACT FROM AUTHOR]

A heterogeneous palladium(II) catalyst anchored to modified metal-organic framework has been synthesized and characterized. The performance of the catalyst has been tested for the hydrogenation of styrene oxide at ambient temperature and pressure. The catalyst showed an excellent activity and selectivity for the preparation of 2-phenylethanol from styrene oxide with 100% conversion and 98% selectivity. The catalyst is very stable and easily recyclable for several times without loss of activity. [ABSTRACT FROM AUTHOR]

Several new random copolyethers of styrene oxide (SO) and other monosubstituted oxirane as comonomer, i.e., propylene oxide (PO), isopropyl glycidyl ether (IPGE) or allyl glycidyl ether (AGE), were synthesized in THF solution at room temperature. As initiator monopotassium salt of dipropylene glycol activated by 18-crown-6 complexing agent was used. Synthesized copolyether-diols were characterized by SEC, 13C NMR and MALDI-TOF techniques. They were unimodal and had Mn = 3500–4600 and relatively low dispersity (Mw/Mn = 1.16–1.18). Low unsaturation of the products resulted from chain transfer reaction to styrene oxide. Composition of SO/PO-diol, SO/IPGE-diol and SO/AGE-diol copolymers was determined by MALDI-TOF mass spectrometry. Homopolymers were not formed during the processes. [ABSTRACT FROM AUTHOR]

Pd(II) ions were introduced into Mg0.7Al0.3(OH)2(CO3)0.15·mH2O through the co-precipitation of the corresponding nitrate salts at a constant pH value. The presence of Pd in the brucite-like layers affects an increased surface area and decreased crystal domain of the Mg–Al hydrotalcite catalysts. Pd(II) ions may exist in both intra- and extra- brucite-like layers and exhibit different roles in the oxidation of styrene with t-BuOOH, depending on the amount of palladium. The insertion of Pd(II) into the hydrotalcite lattice has significantly improved the catalyst stability. The highest conversion of styrene is about 80% for the production of styrene oxide and benzaldehyde at low temperatures. [ABSTRACT FROM AUTHOR]

Phase-pure interpenetrated MOF-5 ([Zn4(O)(BDC)3]) was synthesized by pH* control in a reaction medium, and its stability in the presence of epoxides was confirmed by powder X-ray diffraction analysis. Interpenetrated MOF-5/tetra-n-butylammonium bromide (int-MOF-5/n-Bu4NBr) showed a high catalytic activity toward CO2 fixation to epoxide to synthesize cyclic carbonates. The conversions of propylene oxide (PO) and styrene oxide (SO) by int-MOF-5/n-Bu4NBr were almost two times higher than those by MOF-5/n-Bu4NBr under the same conditions. From a kinetics point of view, the coupling reaction rate of PO and CO2 was much higher than that of SO and CO2, which may be due to steric effects. The optimized geometries by the density functional theory calculation revealed that Lewis acidic Zn(II) sites of tetranuclear {Zn4O} clusters can work as the catalytic center to bind epoxides to open the rings by a nucleophilic attack. This co-catalyst system may be useful for the synthesis of cyclic carbonate by CO2 fixation. [ABSTRACT FROM AUTHOR]

Under conventional conditions of styrene oxide conversion catalyzed by perchloric acid in an alcohol solution (ButOH-chlorobenzene (9 : 1 by vol.), 343 K), an iminium ylide absorption band (λmax ≈ 460–470 nm) was recorded in the presence of pyridine trap, which corresponds to the adduct of pyridine and phenylmethylene. In the presence of oxygen, another intermediate product was detected, the absorption band of which (λmax ≈ 400 nm) coincides with the corresponding carbonyl oxide absorption. A similar observation was made earlier for the acid-catalyzed conversion of styrene oxide in the presence of p-toluenesulfonic acid in alcohol and acetonitrile solutions. Thus, the obtained results confirm formation of active intermediate species of carbene nature in two epoxide-acid systems. [ABSTRACT FROM AUTHOR]

A new organic–inorganic hybrid compound contained bi-capped Bi Keggin anion, [biim][PMo1VMo11VIBi1.24O40]·3H2O (1) (biim = biimidazole) has been firstly synthesized and characterized by IR, UV–Vis, XRD, XPS, elemental analyses, fluorescent spectrum and TG analysis. Compound 1 exhibits a novel 2-D supramolecular network structure constructed from {PMo1VMo11VIBi1.24O40} anions by O···O interactions, and further extends a 3-D supramolecular framework by bridges of biimidazole with N–H···O hydrogen bonding interactions. The compound 1 performs well catalytic property for epoxidation of styrene to styrene oxide. Moreover, compound 1 displays excellent photodegradation activity for methyl orange dye. [ABSTRACT FROM AUTHOR]

In this study we have combined the bioreduction of α-bromoketones using carrot root as biocatalyst and click chemistry for the preparation of enantiopure β-hydroxytriazoles in excellent enantiomeric excesses and yields. Moreover, we have utilized chiral α-halohydrins for the synthesis of enantiopure styrene oxides in very good yields and enantiomeric excesses. Structural assignments of the products were based on their 1H and 13C NMR data and their optical rotations. The enantiomeric excess of the chiral products was obtained by HPLC analysis. [ABSTRACT FROM AUTHOR]

In a mixed tert-butanol-chlorobenzene (9 : 1 vol) solution, the consumption of oxygen by a styrene oxide-aniline-copper(II) chloride ternary system is studied. For the first time, the formation of free radical particles is detected in copper(II) salt-catalyzed reaction of styrene oxide with the amine. [ABSTRACT FROM AUTHOR]

Abstract: The controllable synthesis of efficient supported non-noble with fitting chemical state for styrene epoxidation is of great significance to save scarce resources and improve the atom economy. Herein, a series of Ce modified CuO/CoAl-hydrotalcite catalysts was prepared using deposition-precipitation (DP) method. The appropriate addition of Ce (Ce/Cu = 0.2) could contribute to the dispersion of CuO on the surface of support. Moreover, the chemical state of CuO could be finely tuned by the introduction of Ce additives: Ce interacted with CuO and maked CuO surface enrichment of electrons, while CeO2 weakened the interaction between CuO and CoAl-HT support, increasing the percentage of Cu2+ ions (CuA2+) in metal oxides. Therefore, the obtained CuO-0.2CeO2/CoAl-HT catalyst, possessing maximum CuA2+, exhibited optimal styrene oxide yield in styrene epoxidation reaction at similar condition to date, achieving 79.5% selectivity at 99.6% styrene conversion.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: The new halohydrin dehalogenase-like gene (HheB8) in the genome of Bradyrhizobium erythrophlei was identified, synthesized and expressed in Escherichia coli. The encoded protein (HheB8) was purified to homogeneity as a molecular mass of 26 kDa and characterized using the model substrate of 1,3-dicholoro-2-propanol (1,3-DCP). The purified HheB8 was optimally active at pH 9.5 and 45 °C, and highly stable at pH 6.0-8.0 and 40 °C or below. The enzyme displayed a very broad substrate specificity, exhibiting good enantioselectivity for the transformation of prochiral 1,3-DCP and 1,3-dibromo-2-propanol to (R)-ECH (92.3% enantiomeric excess ee) and (R)-epibromohydrin (81.3% ee). For all tested epoxides, except styrene oxide, the (R)-enantiomer was converted first, affording (S)-isomer in 99% ee. Furthermore, the potential for using a single HHDH to enantioselectively produce both enantiomers of ECH was analyzed. The bioconversion process for production of (R)-ECH from 1,3-DCP by the recombinant HheB8 was developed and a maximum ee of 93.4% was achieved. Kinetically resolved racemic ECH (30 mM) to provide (S)-ECH with 99% ee and 33.4% yield. To the best of our knowledge, this is the first report of HheB8 used as biocatalyst in the production of enantiopure ECH. Therefore, this recombinant HHDH could be a potential candidate for application in the synthesis of chiral chemicals from prochiral halohydrins and racemic epoxides.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Development of environmentally benign green processes for utilization of carbon dioxide to synthesize value-added compounds using heterogeneous catalysis is desirable. One such proposed process is the cycloaddition of styrene oxide with carbon dioxide to synthesize styrene carbonate, synthesis of which has been well studied using various homogenous catalysts. The aim of the current work was to develop an active, selective and reusable heterogeneous catalyst for the cycloaddition of carbon dioxide to styrene oxide. Various solid catalysts such as 0.1% Li/MgO, calcined hydrotalcite (CHT), La–Zr mixed oxide (1:3 La/Zr), 0.1% La/MgO and ZrO2 were employed for cycloaddition of carbon dioxide to styrene oxide. Carboxylation of styrene oxide with carbon dioxide is enhanced by catalysts having both strong basic sites and weak acidic sites. Lanthanum–zirconia mixed oxide was prepared by combustion method using different compositions and evaluated for this reaction. La/Zr ratio of 1:3 was found to be the best among all studied and gave 90% conversion of styrene oxide with 100% selectivity of styrene carbonate at moderate temperature and pressure conditions in 3 h. The catalyst was characterized by various techniques to understand its textural properties. The catalyst was reused over three cycles without any loss of activity. The optimum reaction conditions were obtained by studying all process parameters in a laboratory batch stirred tank reactor (speed of agitation-1000 rpm, catalyst loading-2 × 10−2 g/cm3, 0.01 mol styrene oxide, DMF as solvent (total volume 30 mL), CO2 pressure-2.5 MPa, 130 °C). A detailed mathematical model was developed using Langmuir–Hinshelwood-Hougen–Watson mechanism in the absence of any transport resistances. The activation energy was calculated as 19.1 kcal/mol. The process is green and clean. [ABSTRACT FROM AUTHOR]

N-(2-Aminoethyl)-N-(2-hydroxy-2-phenylethyl)carboxamides were synthesized from styrene oxide by ring opening with N,N-disubstituted ethylenediamines followed by N-acylation. Synthesized compounds have pronounced antiarrhythmic activity and low toxicity. [ABSTRACT FROM AUTHOR]

Objectives: To prepare ( R)-phenyl-1,2-ethanediol (( R)-PED) with high enantiomeric excess ( ee ) and yield from racemic styrene oxide ( rac-SO) at high concentration by bi-enzymatic catalysis. Results: The bi-enzymatic catalysis was designed for enantioconvergent hydrolysis of rac-SO by a pair of novel epoxide hydrolases (EHs), a Vigna radiata EH3 ( VrEH3) and a variant ( AuEH2) of Aspergillus usamii EH2. The simultaneous addition mode of VrEH3 and AuEH2, exhibiting the highest average turnover frequency (aTOF) of 0.12 g h g, was selected, by which rac-SO (10 mM) was converted into ( R)-PED with 92.6% ee and 96.3% yield. Under the optimized reaction conditions: dry weight ratio 14:1 of VrEH3-expressing E. coli/ vreh3 to AuEH2-expressing E. coli/ Aueh2 and reaction at 20 °C, rac-SO (10 mM) was completely hydrolyzed in 2.3 h, affording ( R)-PED with 98% ee . At the weight ratio 0.8:1 of rac-SO to two mixed dry cells, ( R)-PED with 97.4% ee and 98.7% yield was produced from 200 mM (24 mg/ml) rac-SO in 10.5 h. Conclusions: Enantioconvergent hydrolysis of rac-SO at high concentration catalyzed by both VrEH3 and AuEH2 is an effective method for preparing ( R)-PED with high ee and yield. [ABSTRACT FROM AUTHOR]

It was stated that initiation in ring opening polymerization of styrene oxide depends on the kind of potassium alkoxide activated by 18-crown-6 used. In the presence of potassium methoxide the oxirane ring opening occurs exclusively in the β-position and not in the β or α position, i.e., contrary to the previous data. A similar result was obtained in the systems initiated with potassium t-butoxide, 2-methylpropoxide and 1-phenylethoxide. Unexpectedly, potassium i-propoxide and 1-methylpropoxide open the oxirane ring in the β or α position. In all polymerizations, deprotonation of methine group in the monomer takes place under the influence of the initiator and in chain transfer reaction to the monomer. It leads to the formation of macromolecules with unsaturated starting group. However, deprotonation of methylene group in the monomer does not occur. Applying of potassium hydroxyalkoxides, i.e., monopotassium salt of dipropylene glycol or tripotassium salt of 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol it was possible to synthesize PSO-diols and PSO-pentols without unsaturation. Molar masses of polymers ( M = 1700-4800 Da) are much higher than reported in literature for other anionic systems. Dispersity of polymers is rather low ( M / M = 1.07-1.15) indicating relatively high rate of initiation and cation exchange reaction. [ABSTRACT FROM AUTHOR]

The catalytic performance of the isomerization of styrene oxide to phenyl acetaldehyde was investigated over different modified beta catalysts under gas-phase atmosphere free of solvents. The physicochemical properties were characterized by a combination of X-ray diffraction (XRD), N adsorption, Fourier transform infrared spectroscopy (FT-IR), Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR), NH-Temperature programmed desorption (NH-TPD) and thermo gravimetric analysis (TGA), etc. Acid sites with stronger strength are responsible for the formation of condensation products and fast deactivation of catalysts. The obtained results also demonstrate that the introduction of boron atoms can create suitable acid strength and acid distribution without significantly destroying its microporous structures. Therefore, BAl-BEA sample is highly active and selective for the rearrangement of styrene oxide as well as very stable to deactivation. Graphical Abstract: [ABSTRACT FROM AUTHOR]

A new efficient heterogeneous catalyst was introduced for the epoxidation of styrene. The catalyst was obtained from deposition of gold nanoparticles on the cellulose aerogel. The catalyst was characterized with XRD, TGA, EDX, BET, FAAS and SEM. High yield and excellent selectivity were achieved for the epoxidation of styrene in solvent-free conditions at room temperature using HO as a green oxidant during 1 h. The reaction has some advantages such as solvent-free and mild reaction conditions, low catalyst loading, high yield, excellent selectivity, green oxidant and short reaction duration. In addition, the catalyst is recyclable and applicable for six times without decrease in yield. [ABSTRACT FROM AUTHOR]

Cyclocondensation of O- n-propylated eugenol with cyanoacetamides was used to synthesize 2-[3-methyl-6-methoxy-7-( n-propoxy)-3,4-dihydroisoquinolin-1]ethanoic acid amides. The hydrochlorides of these compounds were tested for antihelminthic and insecticidal activity. The most active compounds were amides containing a cyclic amine fragment (pyrrolidine, piperidine, morpholine), which had greater activity than Pyrantel. Compounds without substituents at the amide nitrogen and the N-ethylamide had insecticidal activity at the levels of diazinon and pirimiphos. [ABSTRACT FROM AUTHOR]

The gas phase isomerization of styrene oxide (STO) into phenylacetaldehyde (PhAD) in good yield and selectivity has been achieved using a steel tube reactor as catalyst in an efficient and environmentally friendly process. Under semi-optimized conditions (240 °C, N flow) a steel tube reactor filled with steel balls gave a selectivity of PhAD of 99% at 98% STO conversion. Use of an equivalent glass reactor as a control gave conversions of <5% under similar reaction conditions and revealed that the isomerization is catalyzed by both the steel reactor wall as well as the steel balls. The reactor is cheap to manufacture, and does not require re-activation before reuse. A possible mechanism for the reaction is proposed. [ABSTRACT FROM AUTHOR]

A new support for Pd(II) was synthesized via the functionalization of FeO nanoparticles with N-(2-aminoethyl)acetamide. PdCl was anchored to the support for obtaining a heterogeneous magnetically recoverable catalyst for Pd(II). High yield and excellent selectivity were obtained for the green epoxidation of styrene derivatives using HO as a green oxidant in HO as the solvent at 100 °C. Also, the recovered catalyst is applicable for four times without significant decrease in yield. [ABSTRACT FROM AUTHOR]

Enantiopure styrene oxide (SO) and its derivatives are important building blocks for chiral synthesis. In this study, we developed an attractive '1-pot, 2-step' chemoenzymatic approach for producing enantiopure SO with 100 % theoretical yield. This approach involved asymmetric reduction of α-chloroacetophenone by an alcohol dehydrogenase (ADH; step 1), followed by base-induced ring closure (epoxidation) of enantiopure 2-chloro-1-phenylethanol produced by the ADH (step 2). By-product formation during epoxidation was suppressed to <1 % by adding methyl tert-butyl ether (MTBE) as the second phase. Therefore, with this optimized approach, ADH from Lactobacillus kefir (LkDH) successfully produced 1 M ( S)-SO, with 99 % analytical yield and 97.8 % enantiomeric excess ( ee). In the preparation of ( R)-SO, a semi-rational strategy of active pocket iterative saturation mutagenesis (ISM) was successfully used to inverse the enantioselectivity of LkDH (muDH2, F147L/Y190P/A202F/M206H/V196L/S96D/K97V), which produced the opposite enantiomer ( R)-2-chloro-1-phenylethanol. Through the optimized chemoenzymatic approach, muDH2 was successfully used to prepare 1 M ( R)-SO, with 98.1 % ee and 99.0 % analytical yield. Our results indicated that this optimized chemoenzymatic approach could be used to produce both enantiomers of SO at concentrations as high as 120 g/L within 14 h, which is the highest concentration as far as we know. MuDH2 obtained through ISM also showed reversed enantioselectivity toward another 13 aromatic ketones, compared with wild-type (WT) LkDH. Furthermore, a molecular docking experiment demonstrated that muDH2 inverted the binding orientation of the substrate, which may be the reason for its inverse enantioselectivity. [ABSTRACT FROM AUTHOR]

Palladium-decorated chitosan catalyst was synthesized by an impregnation method by varying the Pd loading in the range of 1-6 %, and was evaluated for the regioselective hydrogenation of styrene oxide. In order to correlate the chemical and textural properties with the catalytic activity, all the prepared catalysts were characterized by techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron spectroscopy, thermo-gravimetric analysis, temperature-programmed desorption of NH, and CO and N physisorption. The synthesized catalysts were utilized for the efficient and regioselective ring opening of styrene oxide by hydrogenation under different conditions. The complete conversion of styrene oxide with 65 % selectivity for 2-phenyl ethanol and 33 % for 1-phenyl ethanol were obtained using 4 % Pd/CS catalyst at 70 °C temperature and 3 MPa pressure. The mechanism for the regio selective ring opening of styrene oxide to 1- and 2-phenyl ethanol was also proposed on the basis of properties of the catalyst support, catalytic activity and selectivity. These results indicated that the catalytic activity and selectivity of the catalysts were affected by the nature of support. Further, the basic properties of the support play an important role in the selectivity of the styrene oxide hydrogenation reaction. [ABSTRACT FROM AUTHOR]

Based on an entropy-driven principle, new macroporous helical silica rods were synthesized by using mild templates in sol-gel, then functionalized for immobilizing Co-salen complexes to catalyze enantioselective hydrolytic kinetic resolution of epoxides. Characterization revealed both silica supports and heterogeneous Co-salen complexes were macroporous helical materials with affirmative chirality. Catalysis revealed enantioselective adsorption of substrate on silica supports dominated major configuration of resolution products rather than configuration of Co-salen. The ( S)-amino alcohol-doped silica and Co-( R, R)salen comprised the most enantioselective combination, which proved chiral synergy between support and Co-salen did exist. This work would contribute to the design of new support materials for asymmetric catalysis. [ABSTRACT FROM AUTHOR]

The antioxidant activity of aromatic nitroxides in the oxidation of styrene was studied using a complex of kinetic methods in combination with quantum chemical calculations and kinetic modeling. During oxidation of styrene and its saturated analog, ethylbenzene, aromatic nitroxides terminate oxidation chains via the reaction with both alkyl and peroxyl radicals. The mechanism of the process was proposed, which explains multiple chain termination by the interaction of peroxyl and nitroxide radicals revealed in the investigation of styrene oxidation. [ABSTRACT FROM AUTHOR]

The addition of ZnI drastically accelerated the cycloaddition of carbon dioxide to styrene oxide catalyzed by pyrrolidinopyridinium iodides. In the presence of ZnI, the styrene carbonate yield reached up to 89 % in 7 h at 100 °C under 1 atm of CO. The rate constant increased by greater than three-fold by the addition of ZnI. Studies of reaction kinetics in addition to high resolution mass and NMR analysis demonstrated that the primary active species consists of two or more pyrrolidinopyridinium cations combined with ZnI anion. [ABSTRACT FROM AUTHOR]

( S)-Styrene oxide, ( S)-2-chlorostyrene oxide (CSO), ( S)-3-CSO and ( S)-4-CSO with 99.9 % ee were obtained with a yield of 20.6, 39.3, 28.7 and 26.8 % from 4 mM corresponding racemic substrates using 10 mg cells of a newly-isolated Sphingopyxis sp. at pH 8.0 and 25 °C in 1 ml 100 mM Tris/HCl buffer after 420, 100, 120 and 55 min, respectively. For racemic 2CSO, well-known for one of the racemates that is difficult to obtained in enantiomerically pure form, ( S)-2-CSO with 99.9 % ee, 39.3 % yield (theoretical yield 50 %) and enantiomeric ratio of 42.1 was obtained. The newly-isolated strain can thus be used as whole-cell biocatalyst in the production of various ( S)-CSO with a chlorine group at different positions. [ABSTRACT FROM AUTHOR]

CuO nanorodes, CuO nanoplates and Ag/CuO nanoparticles were synthesized in the presence of polyethylene glycol by depositional in alkaline environment. Oxide nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared absorption spectra (FT-IR). CuO and Ag/CuO nanoparticles show high catalytic activity for the selective epoxidation of styrene to styrene oxide by TBHP. Under the optimized reaction condition, the oxidation of styrene catalyzed by CuO nanorods gave 100% conversion with 60 and 35% styrene oxide and benzaldehyde, respectively. Ag/CuO gave 99% conversion and styrene oxide (71%) and benzaldehyde (12%) being the major product. [ABSTRACT FROM AUTHOR]

Opening of racemic styrene oxide with p-toluidine catalyzed by chiral BINOL-derived polyols proceeded regioselectively mainly with the formation of 2-phenyl-2-( p-tolylamino)-ethanol with low ee values. [ABSTRACT FROM AUTHOR]