Alkylene Oxide Research Articles

Ru Active Centers Incorporated on Ce‐MOFs as an Efficient Heterogeneous Catalyst for Oxidation of Alkylarenes to Carbonyls

AbstractIn recent years, the construction of the carbonyl group which can be extensively found in various important chemicals have attracted great interest of researchers. In this study, a strategy of coordination is employed to synthesize Ru‐UiO‐66‐NH2 (Ce) with uniformly dispersed Ru ions in UiO‐66‐NH2 (Ce) MOFs as an efficiently heterogenous catalyst for the catalytic oxidation of benzyl sp3 C─H bond to the carbonyl group in water. The characterized results indicate that the active Ru centers were successfully incorporated via the coordination with the amino group in UiO‐66‐NH2 (Ce) MOFs. This strategy could furnish more catalytic active sites to improve the catalytic performance of Ru‐UiO‐66‐NH2 (Ce). A series of alkylarenes could be efficiently oxidized to ketones with Ru‐UiO‐66‐NH2 (Ce) catalyst under mild conditions. Furthermore, the catalyst's recyclability demonstrated that its catalytic performance remained robust, with no significant loss in the catalytic activity observed after being recycled seven times.

Silica coated N-doped carbon modified with ruthenium nanoparticles: An effective waste derived carbon nanocatalyst in oxidation reactions and also its evaluation by DFT and anti-bacterial studies

This report presents the development of an inexpensive mesoporous nanocatalyst i.e. silica coated N-doped carbon modified with ruthenium nanoparticles (Ru/RuO2@NSAC). The carbon and nanosilica components were derived from waste materials namely waste tea extract and rice husk respectively highlighting the sustainable approach to the synthesis process. The nanocatalyst was thoroughly characterized using various advanced techniques such as Fourier transform infrared spectroscopy (FTIR), Powder X-ray diffraction (P-XRD), Field emission gun-scanning electron microscopy (FEG-SEM), Energy dispersive X-ray analysis (EDX), High resolution-transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis, X-ray resonance fluorescence (XRF) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). These characterizations provided comprehensive insights into the structural features of the nanocatalyst. XPS analysis confirmed the presence of both metallic ruthenium and Ru (IV) on the nanocatalytic support. The particle size of Ru/RuO2@NSAC was determined using Scherrer's equation and came out to be 21.37 nm. This nanocatalyst demonstrated remarkable performance as a robust heterogeneous catalyst for the oxidation of alkylarenes and alcohols to their corresponding carbonyl compounds. It exhibited excellent recyclability, maintaining its activity for up to five consecutive runs. Post-recycling, the catalyst was again characterized by P-XRD and FEG-SEM to ensure its structural integrity. Additionally, the antibacterial activity of Ru/RuO2@NSAC was evaluated against both Gram-positive and Gram-negative bacteria. A density functional theory study was also conducted to support the experimental findings, providing a theoretical basis for the observed catalytic behavior.

Jeffamine-based diblock copolymer nanoparticles via reverse sequence polymerization-induced self-assembly in aqueous media

Jeffamines® are commercially available amine-capped poly (alkylene oxides) that have been used for various applications. In this study, a weakly hydrophobic monoamine-capped propylene oxide-rich Jeffamine® (M2005) is derivatized to introduce a trithiocarbonate end-group via amidation. This precursor is then dissolved using N,N′-dimethylacrylamide (DMAC), 2-(N-acryloyloxy)ethyl pyrrolidone (NAEP) or N-acryloylmorpholine (NAM) as a co-solvent to produce a concentrated aqueous reaction mixture containing 20 % w/w water. Subsequently, reversible addition-fragmentation chain transfer (RAFT) polymerization is used to prepare Jeffamine®-core diblock copolymer nanoparticles by reverse sequence polymerization-induced self-assembly (PISA). At intermediate conversion, additional degassed water is added and each polymerization continues to almost full conversion (>99 %) within 4 h at 60 °C, resulting in a 10–20 % w/w aqueous dispersion of sterically-stabilized Jeffamine®-core nanoparticles. Efficient chain extension of the Jeffamine® precursor is achieved in most cases and relatively narrow molecular weight distributions are obtained (Mw/Mn < 1.30) as judged by GPC analysis. Transmission electron microscopy studies confirm a polydisperse spherical morphology and dynamic light scattering studies report hydrodynamic diameters ranging from 145 to 312 nm. Finally, aqueous electrophoresis studies indicate essentially neutral nanoparticles over a wide range of solution pH, as expected for the three types of non-ionic steric stabilizer chains selected for this study.

Self-Photocatalyzed Oxidation of Alkylarenes to Carbonyls with Water

Self-Photocatalyzed Oxidation of Alkylarenes to Carbonyls with Water

Emerging pollutants in textile wastewater: an ecotoxicological assessment focusing on surfactants.

Water and several chemicals, including dyestuffs, surfactants, acids, and salts, are required during textile dyeing processes. Surfactants are harmful to the aquatic environment and induce several negative biological effects in exposed biota. In this context, the present study aimed to assess acute effects of five surfactants, comprising anionic and nonionic classes, and other auxiliary products used in fiber dyeing processes to aquatic organisms Vibrio fischeri (bacteria) and Daphnia similis (cladocerans). The toxicities of binary surfactant mixtures containing the anionic surfactant dodecylbenzene sulfonate + nonionic fatty alcohol ethoxylate and dodecylbenzene sulfonate + nonionic alkylene oxide were also evaluated. Nonionic surfactants were more toxic than anionic compounds for both organisms. Acute nonionic toxicity ranged from 1.3mg/L (fatty alcohol ethoxylate surfactant) to 2.6mg/L (ethoxylate surfactant) for V. fischeri and from 1.9mg/L (alkylene oxide surfactant) to 12.5mg/L (alkyl aryl ethoxylated and aromatic sulfonate surfactant) for D. similis, while the anionic dodecylbenzene sulfonate EC50s were determined as 66.2mg/L and 19.7mg/L, respectively. Both mixtures were very toxic for the exposed organisms: the EC50 average in the anionic + fatty alcohol ethoxylate mixture was of 1.0mg/L ± 0.11 for V. fischeri and 4.09mg/L ± 0.69 for D. similis. While the anionic + alkylene oxide mixture, EC50 of 3.34mg/L for D. similis and 3.60mg/L for V. fischeri. These toxicity data suggested that the concentration addition was the best model to explain the action that is more likely to occur for mixture for the dodecylbenzene sulfonate and alkylene oxide mixtures in both organisms. Our findings also suggest that textile wastewater surfactants may interact and produce different responses in aquatic organisms, such as synergism and antagonism. Ecotoxicological assays provide relevant information concerning hazardous pollutants, which may then be adequately treated and suitably managed to reduce toxic loads, associated to suitable management plans.

Constructing Cu+ and Lewis acid sites enabling the generation of highly reactive N‑oxyl radical for the efficient aerobic oxidation of alkylarenes

Developing heterogeneous catalytic systems with high performance for the oxygenation of C(sp3)–H bonds to carbonyls using molecular oxygen as the oxidant is highly desirable. In the present research, active Cu+ sites have been efficiently constructed based on layered double hydroxides (LDHs) through in-situ reduction during the coprecipitation. Simultaneously, the formed CuZn(Mg)Al-LDH(R) catalysts demonstrated the characters of increased amount of oxygen vacancy and surface Lewis acid site. The newly synthesized catalysts exhibited higher catalytic performance than the samples prepared via conventional method, and up to 49.4% improvement in specific activity was observed in the aerobic oxidation of ethylbenzene. The mechanism study including a series of control experiments, semi-in-situ FT-IR analysis, and EPR analysis, demonstrated that reactive •O2– species generated via the acceleration of Cu+ species, and activated the NHPI (N-hydroxyphthalimide) molecule to form active PINO (phthalimide N-oxyl) species. The oxygen vacancy was verified to be able to activate O2 molecule and promote the formation of active 1O2 species. The surface Lewis acid site was proposed to interact with NHPI molecule, enabling the generation of highly active PINO species. The catalytic system also has the advantages of catalytical and structural stability, recyclability, and tolerance of wide substrate scope. We believe that the synergistic effect between the highly active sites and Lewis acid sites in catalyst can open up new opportunities for the activation of inert C–H bonds via O2/NHPI system.

Diazene-Catalyzed Oxidative Alkyl Halide-Olefin Metathesis.

The first platform for oxidative alkyl halide-olefin metathesis is described. The procedure employs diazenes as catalysts, which effect the cyclization of alkenyl alkyl halides to generate cyclic olefins and carbonyl products. The synthesis of phenanthrene, coumarin, and quinolone derivatives is demonstrated as well as the potential to apply this strategy to other electrophiles.

Cyclic ether and anhydride ring opening copolymerisation delivering new ABB sequences in poly(ester-alt-ethers).

Poly(ester-alt-ethers) are interesting as they combine the ester linkage rigidity and potential for hydrolysis with ether linkage flexibility. This work describes a generally applicable route to their synthesis applying commercial monomers and yielding poly(ester-alt-ethers) with variable compositions and structures. The ring-opening copolymerisation of anhydrides (A), epoxides (B) and cyclic ethers (C), using a Zr(iv) catalyst, produces either ABB or ABC type poly(ester-alt-ethers). The catalysis is effective using a range of commercial anhydrides (A), including those featuring aromatic, unsaturated or tricyclic monomers, and with different alkylene oxides (epoxides, B), including those featuring aliphatic, alkene or ether substituents. The range of effective cyclic ethers (C) includes tetrahydrofuran, 2,5-dihydrofuran (DHF) or 1,4-bicyclic ether (OBH). In these investigations, the catalyst:anhydride loadings are generally held constant and deliver copolymers with degrees of copolymerisation of 25, with molar mass values from 4 to 11 kg mol-1 and mostly with narrow dispersity molar mass distributions. All the new copolymers are amorphous, they show the onset of thermal decomposition between 270 and 344 °C and variable glass transition temperatures (-50 to 48 °C), depending on their compositions. Several of the new poly(ester-alt-ethers) feature alkene substituents which are reacted with mercaptoethanol, by thiol-ene processes, to install hydroxyl substituents along the copolymer chain. This strategy affords poly(ether-alt-esters) featuring 30, 70 and 100% hydroxyl substituents (defined as % of monomer repeat units featuring a hydroxyl group) which moderate physical properties such as hydrophilicity, as quantified by water contact angles. Overall, the new sequence selective copolymerisation catalysis is shown to be generally applicable to a range of anhydrides, epoxides and cyclic ethers to produce new families of poly(ester-alt-ethers). In future these copolymers should be explored for applications in liquid formulations, electrolytes, surfactants, plasticizers and as components in adhesives, coatings, elastomers and foams.

Retraction: Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature.

Retraction of 'Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature' by Mojtaba Mahyari et al., Chem. Commun., 2014, 50, 7855-7857, https://doi.org/10.1039/C4CC01406E.

Paired electrocatalysis enabled oxidative coupling of styrenes with alkyl radicals.

A paired electrocatalysis strategy for intermolecular oxidative cross-dehydrocoupling between styrenes and ethers or p-methylphenol derivatives using ketone as a mild oxidant is described. This approach enables the generation of Csp3 carbon-centered radicals through anodic oxidation, followed by reductive coupling of ketones at the cathode, ultimately yielding valuable oxidative alkylation products.

Kinetic analysis of aerobic oxidation catalyzed by a hybrid heterogeneous-homogeneous system containing supported Mn and V oxides and N-hydroxyphthalimide

The activities of transition metal oxide (TMO) heterogeneous catalysts based on individual components such as VOX, and MnOX supported on TiO2 and TiO2-SiO2 as cocatalysts in catalytic systems complemented with N-hydroxyphthalimide (NHPI) in the processes of aerobic liquid-phase radical chain oxidation of alkylarenes (RH) was investigated. The mechanisms of catalysis by NHPI in a liquid phase and participation of TMO in the chain initiation stage were discussed. Catalytic activities of Mn- and V-oxide catalysts were compared with the results of molecular hydrogen temperature programmed reduction profiles (H2-TPR) of the catalysts, revealing correlation between them. Reaction enthalpies calculated via a semi-empirical method for model structures of catalytic centers explained the obtained experimental results. Finally, catalytic cumene oxidation was presented using a reactions scheme identifying the concomitant role of heterogeneous initiation and homogeneous propagation and termination steps for the oxidation process proceeding via a free-radical mechanism.

Photo- and Metal-Mediated Deconstructive Approaches to Cyclic Aliphatic Amine Diversification.

Described herein are studies toward the core modification of cyclic aliphatic amines using either a riboflavin/photo-irradiation approach or Cu(I) and Ag(I) to mediate the process. Structural remodeling of cyclic amines is explored through oxidative C-N and C-C bond cleavage using peroxydisulfate (persulfate) as an oxidant. Ring-opening reactions to access linear aldehydes or carboxylic acids with flavin-derived photocatalysis or Cu salts, respectively, are demonstrated. A complementary ring-opening process mediated by Ag(I) facilitates decarboxylative Csp3-Csp2 coupling in Minisci-type reactions through a key alkyl radical intermediate. Heterocycle interconversion is demonstrated through the transformation of N-acyl cyclic amines to oxazines using Cu(II) oxidation of the alkyl radical. These transformations are investigated by computation to inform the proposed mechanistic pathways. Computational studies indicate that persulfate mediates oxidation of cyclic amines with concomitant reduction of riboflavin. Persulfate is subsequently reduced by formal hydride transfer from the reduced riboflavin catalyst. Oxidation of the cyclic aliphatic amines with a Cu(I) salt is proposed to be initiated by homolysis of the peroxy bond of persulfate followed by α-HAT from the cyclic amine and radical recombination to form an α-sulfate adduct, which is hydrolyzed to the hemiaminal. Investigation of the pathway to form oxazines indicates a kinetic preference for cyclization over more typical elimination pathways to form olefins through Cu(II) oxidation of alkyl radicals.

Rigid tertiary amine/saccharin adduct as halide-free organocatalyst for the cycloaddition of CO2 into epoxides

Metal- and halide-free catalyst DABCO·HSac, i.e., the binary adduct of 1,4-diazabicyclo[2.2.2]octane (DABCO) and saccharin (HSac), in an ionic pair structure of DABCO-H+·Sac- is shown mild and efficient in promoting the cycloaddition of CO2 into epoxides (CCE) reactions. Under comparatively low temperature of 60 °C, ambient pressure of 0.1 MPa, and 10 mol% catalyst loading, DABCO·HSac catalyzed the cycloaddition of epichlorohydrin into CO2 with the conversion of 96% in 24 h. Terminal epoxides including epibromohydrin, glycidyl ethers, and alkylene oxides received 83–99% conversions, however, cyclohexene oxide and stilbene oxide were not viable under these mild reaction conditions. A catalytic cycle initiated by the saccharinate anion of its nucleophilic attack on methylene carbon of an epoxide ring with the iminolate oxygen was proposed as the key step, in which the Sac- anion functioned similarly to halide X- in other ring-opening mechanisms. The tertiary amine DABCO was protonated into an onium cation DABCO-H+ that worked as a hydrogen-bond donor in coordinating and activating the epoxide. A cocatalysis mechanism was suggested and validated by NMR titrations. Further control experiments by switch cation or anion of DABCO-H+·Sac- in structural analog cocatalysts certified both the onium DABCO-H+ and the saccharinate Sac- was indispensable in the catalytic cycle. The design of ionic pair organocatalysts illustrated the possibility of non-halide anions as the nucleophiles in wider halide-free catalyst discovery.

Visible-Light Copper Catalysis for the Synthesis of α-Alkyl-Acetophenones by the Radical-Type Ring Opening of Sulfonium Salts and Oxidative Alkylation of Alkenes.

Direct difunctionalization of simple alkenes has been treated as a powerful synthetic strategy for the construction of highly functionalized skeletons. In this study, direct oxidative coupling of sulfonium salts with alkenes was achieved under mild conditions by a blue-light-driven photoredox process using a copper complex as a photosensitizer. This protocol allows regioselective synthesis of aryl/alkyl ketones from simple sulfonium salts and aromatic alkenes via selective C-S bond cleavage of sulfonium salts and oxidative alkylation of aromatic alkenes using dimethyl sulfoxide (DMSO) as a mild oxidant.

Selective Oxidation of Alkylarene in H2O Catalyzed by the Polyoxometalate Supported Chromium Catalyst

AbstractThe selective oxidation of alkylarene is a quite straightforward and appealing way for production of aromatic aldehydes, ketones and aromatic acid derivatives. We synthesized Cr(III) catalyst, (NH4)3[CrMo6O18(OH)6], with reasonable activity towards selective oxidation of alkylarenes under mild conditions. The catalyst is supported by a central chromium mononucleus and a cyclic inorganic ligand composed of six MoVIO6 octahedra, avoiding the disadvantages of expensive and non‐recyclable organic ligand. It is efficient, green and can be recycled at least six times with high activity. At the same time, a wide range of substituted alkylarenes were found to be compatible, providing the corresponding carbonyl compounds in moderate‐to‐high yield.

Photocatalytic direct oxygen-isotopic labelings of carbonyls in ketones and aldehydes with oxygen-isotopic waters

Oxygen-isotopic labelings play important roles in identifying and understanding chemical and biological processes. Direct C=O to C=18O or C=17O conversion in a single step leading to labeled compounds can alleviate synthetic burdens without the need for resynthesis. Here we describe a photocatalytic oxygen-isotopic labeling protocol that can efficiently and selectively install 18O and 17O on carbonyls of ketones and aldehydes via oxygen isotope exchange with oxygen-isotopic waters (H218O or H217O) as the sources of oxygen isotopes, in which light and oxygen-enabled sodium alkanesulfinates catalyzed this process. This strategy was extended to the in-situ formed ketones from the photocatalytic aerobic oxidation of alkyl arenes and secondary alcohols. Furthermore, reduction of the oxygen-isotopically labeled aldehydes with NaBH4 provided the corresponding oxygen-isotopically labeled primary alcohols. We believe that the oxygen-isotopically labeling method will be widely used in chemistry, biology and medicine fields.

RuO2 supported on MOF-derived CeO2 as an efficient catalyst for selective C–H oxidation of alkylarenes in water at room temperature

Recently, MOFs as an important class of porous crystalline materials are widely utilized as carriers or catalysts in various catalytic systems. In this work, using Ce-BTC supported RuCl3 as a precursor, RuO2–CeO2 composites with high catalytic performance and excellent morphology were successfully synthesized by pyrolysis under ambient atmosphere. An efficient oxidation method for benzyl sp3 C–H bond using the synthesized composites as a heterogeneous catalyst was developed, which could effectively catalyze the selective oxidation of alkylarenes in water at room temperature, and successfully provide a variety of aryl ketone products in high yields with low catalyst dosage. The characterized results indicate that the existence of Ru (IV) is supported. The synthesized RuO2–CeO2 exhibits high activity for the gram-scale oxidation of indane with the lower ruthenium loading (3,837 h−1 TOF based on Ru). Furthermore, the heterogeneous catalyst could be utilized at least six cycles without significant loss of catalytic activity.

Reduced MgFe hydrotalcite efficiently catalyzes the aerobic oxidation of alkylarenes

A new catalyst containing redox couple Fe2+/ Fe3+ and oxygen vacancies has been developed via reduction of MgFe hydrotalcite (MgFe-LDH) by NaBH4. It has been found that oxygen vacancies positively influence the catalytic property of reductive MgFe-LDH (MgFe-LDH(R)). MgFe-LDH(R) showed excellent catalytic activity in the alkylarenes oxidation with molecular oxygen in the absence of additives. Various alkylarenes were compatible with the MgFe-LDH(R) catalytic system with high conversions and selectivities. The kinetic study, controlled experiments, TPD experiments and DFT study demonstrated that the positive catalytic activity were related to a greater number of oxygen vacancies, the capacity to produce singlet oxygen and superoxide radicals and increased amount of low valent states of iron.

Novel resorbable bone wax containing β-TCP and starch microspheres for accelerating bone hemostasis and promoting regeneration.

Traditional non-resorbable bone wax has been used in clinical surgery for more than 100years. However, residual bone wax has been proven to cause numerous complications. In this study, a novel resorbable bone wax was designed to overcome the disadvantages of traditional non-resorbable bone wax. Alkylene oxide copolymers were used as the main component of resorbable bone wax; additionally, β-tricalcium phosphate and starch microspheres were added to enhance bone regeneration and hemostatic ability. This novel resorbable bone wax has a high potential for clinical translation and is expected to be developed as a substitute for traditional bone wax.

A safe production process of alkylene oxide from alkylene carbonates

Alkylene oxides of low molecular weight, ethylene, and propylene oxides, have a widespread use in industry. They are used to produce other chemicals and products such as solvents, surfactants, antifreeze, adhesives, polyurethane foams, and pharmaceuticals. They are also used as fumigants in agricultural products and as sterilant for medical equipment and supplies. Unfortunately, it is worth noting that alkylene oxides also possess several physical and health hazards that merit special attention. They are flammable,explosive and their storage and transportation warrant stringent safety rules. The obvious solution to reduce the risk is to generate them from intermediate safety materials only when and only where they are necessary. The literature suggests that correspondent carbonates are very stable precursors. The scope of our study is that of identifying the optimal conditions to generate ethylene and propylene oxide in the moment just before their reaction and uses. The patent deals with some equipment and process conditions that guarantee a fast and reliable dissociation of carbonates in their correspondent oxides. The natural output of the patent is a unit able to provide the dangerous material in situ, under controlled conditions . As a results, all the risks related to transportation and storage are eliminated.