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A series of Cs(NH4)xH3-xPMo11VO40 with different x values were synthesized to catalyze the selective oxidation of methacrolein to methacrylic acid. The effects of ammonium on both structure and catalytic activity were explored in this study. Compared with CsH3PMo11VO40, the surface area, amount of acid sites, and active species (V4+/VO2+) were found to be strongly dependent on the content of ammonium. The optimum structure of Cs(NH4) 1.5H1.5PMo11VO40 shows comparable large surface area of 50.33 m²/g, large amount of acid sites, and active species (V4+/VO2+), consequently offering a higher methacrolein conversion (83%) and methacrylic acid selectivity (93%). Furthermore, the steady activity of Cs(NH4)1.5H1.5PMo11VO40 was not affected much by the decomposition of ammonium, and the catalyst exhibited good stability. [ABSTRACT FROM AUTHOR]

In this work, we develop a modified mussel-inspired method to enhance interfacial adhesion of aramid fiber to a rubber matrix. Through a simple dip-coating procedure, catechol and polyamine could initially codeposit as a poly(catechol-polyamine) (PCPA) coating on the surface of the aramid fiber. Then, the PCPA layer could be further grafted with silane coupling agent γ-(glycidyloxypropyltrimethoxysilane) (GPTMS). Results indicated that GPTMS was successfully grafted onto the aramid fiber surface via the bridging of the PCPA layer. The interfacial adhesion between the aramid fibers and the rubber matrix was improved compared to that achieved by polydopamine in our previous study. In addition, this method is more applicable to the rubber industry than polydopamine coating because of its cost-effectiveness and short reaction time. [ABSTRACT FROM AUTHOR]

Many enzymes catalyzing biological redox chemistry depend on the omnipresent cofactor, nicotinamide adenine dinucleotide (NAD). NAD is also involved in various nonredox processes. It remains challenging to disconnect one particular NAD-dependent reaction from all others. Here we present a bioorthogonal system that catalyzes the oxidative decarboxylation of l-malate with a dedicated abiotic cofactor, nicotinamide flucytosine dinucleotide (NFCD). By screening the multisite saturated mutagenesis libraries of the NAD-dependent malic enzyme (ME), we identified the mutant ME-L310R/Q401C, which showed excellent activity with NFCD, yet marginal activity with NAD. We found that another synthetic cofactor, nicotinamide cytosine dinucleotide (NCD), also displayed similar activity with the ME mutants. Inspired by these observations, we mutated d-lactate dehydrogenase (DLDH) and malate dehydrogenase (MDH) to DLDH-V152R and MDH-L6R, respectively, and both mutants showed fully active with NFCD. When coupled with DLDH-V152R, ME-L310R/Q401C required only a catalytic amount of NFCD to convert l-malate. Our results opened the window to engineer bioorthogonal redox systems for a wide variety of applications in systems biology and synthetic biology. [ABSTRACT FROM AUTHOR]

A new series of degradable and water-swellable cross-linked PEG phosphoester polymers (CPPs) based on a facile cross-linked reaction between diphosphoesters of polyethylene glycol (P-PEG-P) and diglycidyl ether of polyethylene glycol (E-PEG-E) has been prepared and characterized. The molecular weights and ratios of the prepolymers played an important role for the properties of CPPs polymers, such as mechanical property, swelling, and degradation rates. In the curing process, the glycidyl ether was consumed by both hydroxyl of the phosphoester (P–OH) and hydroxyl generated from the opened glycidyl ethers (C–OH) with the presence of acid, which generated degradable phosphate esters as cross-linked points and ether bonds as the short branches, respectively. Drug entrapment and release test and biological cytotoxicity studies in vitro suggested that the polymers and generated hydrogels have great potential applications in drug delivery system and biological materials. [ABSTRACT FROM AUTHOR]

A tridentate cyclometalating ligand, 1,3-di(1,2,3-triazol-4-yl)benzene (dtab), has been prepared and used for the syntheses of a number of cyclometalated RuIIcomplexes. A comparison of the electrochemical and spectroscopic properties of cyclometalated complexes made from dtab or 1,3-di(2-pyridyl)benzene is presented as well. [ABSTRACT FROM AUTHOR]

Polystyrene-block-poly(ε-caprolactone)-block-poly(n-butyl acrylate) (PS-b-PCL-b-PBA) triblock copolymer was synthesized through the combination of atom transfer radical polymerization, copper-catalyzed Huisgen 1,3-dipolar cycloaddition and ring-opening polymerization. The PS-b-PCL-b-PBA ABC triblock copolymer was incorporated into epoxy to access the nanostructures in the thermoset. The microphase-separated morphology was investigated by means of atomic force microscopy (AFM), small-angle X-ray scattering (SAXS) and dynamic mechanical thermal analysis (DMTA). It was found that depending on the concentration of the triblock copolymer in the thermosets several kinds of nanodomains were formed and they were arranged in lamellar lattice. The formation of the nanostructures was ascribed to the tandem reaction-induced microphase separation of PBA and PS blocks in the thermosetting blends. The investigation of the model binary thermosetting blends showed that the phase separation of PBA occurred at the conversion much lower than that of PS. It is proposed that the PBA nanophases were formed prior to the PS nanophases in the thermosetting blends and the microdomains of PBA subchains could behave as the template for the demixing of PS blocks. The coupling of the two-stage reaction-induced microphase separation exerted a profound impact on the formation of nanostructures in the epoxy thermosets containing the ABC triblock copolymer. Thermal analysis shows that with the formation of the nanostructures in the thermosets a part of poly(ε-caprolactone) subchains were demixed from epoxy matrix; the fractions of demixed PCL blocks have been estimated according to the Tg-composition relation of the model binary blends of epoxy and PCL. [ABSTRACT FROM AUTHOR]

Photoinduced reactions of the 1,2-dicarbonyl compounds phenanthrenequinone (PQ), 1-acetylisatin (IS), and benzil (BZ) with the oxazoles 1a-j have been investigated. In photoreactions of PQ with the oxazoles, in addition to the 1,4-dioxins derived from [4 + 2] cycloaddition and the oxetanes from the Patemó-Büchi [2 + 2] reactions, [4 + 4] cycloaddition products are formed in the reactions with 1a, 1c, 1g, 1i, and 1j, with the quinone's dicarbonyl unit (O=C-C=O) and the oxazole's C=N-C=C moiety as two 4πr addends. Photoreactions of IS with the oxazoles If and 1g give the [4 + 4] cycloaddition products exclusively, while in photoreactions of IS with 1a, 1c, 1e, 1h, and 1i, [4 + 4] products are formed together with the [2 + 2] products. Reaction pathway partitioning in these photocycloaddtions strongly depends on the substitution pattern on the oxazole ring. The presence of a substituent at the oxazole's C2 atom hampers the [4 + 4] pathway by causing steric hindrance to radical pair recombination in the corresponding 1,7-diradical intermediate to form the [4 + 4] cycloaddition products. A substituent at the C4 atom results in steric hindrance for ring closure of the 1,4-diradicats in the [2 + 2] cycloaddition pathway, therefore favoring the [4 + 4] and [4 + 2] cycloaddition pathways. Regio- and diastereoselectivity in the [2 + 2] and [4 + 4] cycloadditions have been discussed based on the thermodynamic stability of the relevant triplet diradical intermediates and the conformations of these diradicals suitable for the intersystem crossing process. Photoreactions of BZ with the oxazoles afford only [2 + 2] cycloaddition products. [ABSTRACT FROM AUTHOR]

Polysulfides with narrow polydispersity and variable chain length and density of polymerizable units have been synthesized through the use of a methacrylate-bearing and thiol-reactive compound as an end-capper for episulfide anionic polymerization. These macromonomers have been photopolymerized to yield materials with controlled cross-linking density, which translates into a controlled number of cross-links, branching points, and dead-ends. The resulting networks show elastomeric behavior that can be easily described through a simple affine chain model; in the analysis of the network behavior we here also present the calculation of a solvent-independent parameter for rationalizing the behavior of the Flory−Huggins parameters. These materials combine simple preparation (→ in situ processes), easy description of the mechanical properties, and responsiveness (to oxidationnot studied here), features that could make them attractive for biomedical applications. [ABSTRACT FROM AUTHOR]

The article focuses on the synthesis of difluorodiazirine (DFD) and the absolute reactivity of difluorocarbene. It is stated that difluorocarbene (CF2) is the most stabilized of the dihalocarnes and its computed stabilization energy is 62.8 kilocalorie/mole (kcal/mol) which is greater than the stabilization energies of chlorofluorocarbene. Meanwhile, DFD generates CF2 upon photolysis or pyrolysis.

The article presents a study which reveals enthalpy versus entropy in chlorocarbene/alkene addition reactions. Researchers have reported the first activation parameters for additions of carbenes to alkenes by adding CCl2 and CClF to the moderately reactive alkenes cyclohexene and 1-hexene. Results prove that entropic factors control the additions of carbenes to the highly reactive alkene, tetramethylene.

A magnetically recyclable catalyst was prepared by embedding magnetic nanoparticle in poly(phosphotungstate-based ionic liquid) matrix. The obtained hybrid material was characterized by XRD, FT-IR, SEM, TEM, TGA, and VSM. The results indicated that Fe3O4 was successfully implanted in multilayer poly(ionic liquid), and the catalyst possessed open active sites (see SEM) to reactants and a high magnetization value. The combination of poly(ionic liquid) matrix with magnetic nanoparticle enhanced the structure stability and favored the separation performance. Esterification of oleic acid with ethanol was conducted in the presence of prepared catalyst, and the Box-Behnken response surface methodology was applied for maximizing the oleic acid conversion by optimizing process variables at 90 °C. Under the optimum conditions (reaction time, 5 h; catalyst amount, 13 wt %; alcohol/acid molar ratio, 12:1), the conversion of oleic acid reached 93.4%. Besides, the catalyst presented fine reusability after six runs and could be facilely recovered in magnetic field based on its superparamagnetism property. [ABSTRACT FROM AUTHOR]

Pentafluorophenylchlorocarbene and pentafluorophenylfluorocarbene are highly reactive species and effective carriers of fluorine labels via addition to alkenes and insertion into C–H bonds. [ABSTRACT FROM AUTHOR]

A room temperature decarboxylative ortho-acylation of acetanilides with α-oxocarboxylic acids has been developed via a novel Eosin Y with Pd dual catalytic system. This dual catalytic reaction shows a broad substrate scope and good functional group tolerance, and an array of ortho-acylacetanilides can be afforded in high yields under mild conditions. [ABSTRACT FROM AUTHOR]

Highly efficient nBu3P-catalyzeddesulfonylative [3 + 2] cycloadditions of allylic carbonates witharylazosulfones were developed for the synthesis of pyrazole derivatives.The reactions proceed smoothly under mild conditions to generate correspondingannulation products in good to excellent yields. [ABSTRACT FROM AUTHOR]

A noveland efficient electrophilic sulfenylation of indoles witharylsulfinic acids is realized. The reaction utilizes readily availablestarting materials in water under catalyst- and additive-free conditions,providing an alternative and attractive approach to 3-arylsulfinylindoleswith high yields. Preliminary mechanistic investigation suggestedthat the reaction is through an electrophilic substitution process. [ABSTRACT FROM AUTHOR]

Rare earth (RE) based coordination polymer (CP) submicrospheres have been prepared from pyridine-2,5-dicarboxylic acid and RE(NO3)3 via a facile microwave heating method in 5 min, with N,N-dimethylformamide (DMF) as solvent. The submicrospheres have diameters of 100-400 nm. Furthermore, the surface of the microspheres is smooth and the microspheres are solid. Several CP submicrospheres (RE = La, Gd, Y) were selected and calcined under different atmospheres (including air, N2, and NH3). After calcination in air at 550 °C for 4 h, rare earth oxide (RE2O3) submicrospheres were obtained. On calcination under an N2 atmosphere, LaN/La2O3/C composite spheres were obtained for La-based CPs. For Gd(Y)-based CPs, Gd2O3(Y2O3)/C composite spheres were obtained. Porous carbon submicrospheres were obtained after the removal of RE2O3 and REN from the composite spheres. Interestingly, under an NH3 atmosphere, La2O2CN2 submicrospheres were produced from the La-based CPs. In addition, the Gd-based and Y-based CPs submicrospheres gave Gd2O3/GdN/C and Y2O3/C submicrospheres, respectively. As examples of their potential applications, their upconversion properties and electrochemical properties of the as-prepared products were investigated. This facile microwave synthesis method may offer an attractive approach for the preparation of other RE-CP micro-/nanostructures, and many interesting materials may be derived. [ABSTRACT FROM AUTHOR]

A series of alkali metal complexes supported by two bulky tetraphenols were synthesized and characterized. The reactions of ɑ,ɑ,ɑ',ɑ'-tetra(3,5-di-ferf-butyl-2-hydroxyphenyl)-p-xylene(para-tetraphenol) with "BuLi, sodium, and KSi(NMe₂)₃ gave bimetallic complexes 1, 2, and 3, respectively. Treatments of the ɑ,ɑ,ɑ',ɑ'-tetra(3,5-di-ierf-butyl-2-hydroxyphenyl)-m-xylene(meta-tetraphenol) with 2 or 4 equiv of "BuLi afforded complexes 4 or 5, while the reactions of meta-tetraphenol with sodium and KSi(NMe₂)₃ gave only trimetallic complexes 6 and 7 for the additional p--π interaction. Complexes 1--7 were all characterized by single-crystal X-ray diffraction techniques. In the presence of benzyl alcohol, all complexes are active catalysts for the ring-opening polymerization of L-lactide. Comparatively, bimetallic complexes 1, 2, and 3 are more efficient catalysts because of their symmetric structures, in which complex 3 presents as a rare highly active potassium catalyst for the ring-opening polymerization of lactide, leading to polymers with good molecular weight control and narrow molecular weight distributions. [ABSTRACT FROM AUTHOR]

Benzo[b]furans were prepared in one pot based on the addition/palladium-catalyzed C–H bond functionalization of phenols with bromoalkynes. The addition reactions of phenols to bromoalkynes generated (Z)-2-bromovinyl phenyl ethers in high yields with excellent regio- and stereoselectivity. The obtained (Z)-2-bromovinyl phenyl ethers subsequently proceeded by intramolecular cyclization to afford 2-substituted benzo[b]furans in good yields through palladium-catalyzed direct C–H bond functionalizations. It is important to note that the transformation of phenols with bromoalkynes into benzo[b]furans could be carried out in one pot with a simple and efficient tandem procedure. [ABSTRACT FROM AUTHOR]

A metal-free novel, simple, and highly efficient method for the direct C2-alkylation of azoles with alcohols and ethers has been developed on the basis of an oxidative C–H activation process. The dehydrogenative C–C cross-coupling reactions of α-position sp3C–H in alcohols and ethers with the 2-position sp2C–H in azoles proceeded smoothly in the presence of tert-butyl hydroperoxide (TBHP) under neat reaction conditions, which generated the corresponding products in good yields. [ABSTRACT FROM AUTHOR]