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Sequential organocatalytic additions of 2-furanone and dihydroxyacetone derivatives to a crotonaldehyde lynchpin provide polyhydroxylated chains reminiscent of lactonized deoxo Kdn type sugars. Further homologation via Kulinkovich ring opening of the butyrolactone and acylation of the zinc homoenolate derived from the incipient cyclopropanol allows assembly of functionalized chain precursors to portimine. Our experiments probe the stability and reactivity of monosubstituted methylidene pyrrolines and generate advanced intermediates useful for exploring the biosynthesis and

The phenomenon that calcium alginate does not exhibit high adsorption capacity as a carrier material has not been reasonably explained or solved. In this paper, a new viewpoint that the orbital energy level of metal ions and the binding degree of the α-l-guluronate and β-d-mannuronate units affect the adsorption performance of the composite was innovatively proposed. Taking barium alginate (BA) as an example, the possibility of replacing calcium alginate is discussed. Barium alginate/graphene oxide (BA/GO) membranes and three-dimensional (3D) barium alginate-bentonite-graphene oxide derived (3D-BA) hydrogels were prepared by vacuum freeze-drying to remove methylene blue. The structure and morphology of the prepared adsorbents were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry and Fourier transform infrared spectroscopy. The effects of adsorbent dosage, doping ratio, temperature, contact time, pH value and initial dye concentration on the adsorption performance of BA composites were investigated. The adsorption capacities of the BA/GO and 3D-BA materials were 1011.3 and 710.3 mg/g, respectively. The BA/GO membrane exhibited stable filtration performance against high concentrations of dyes. Benefiting from the strong interaction between bentonite, sodium alginate and Ba

The past few years have witnessed a renaissance of electrochemistry in organic synthesis. This green technology replaces chemical oxidants or reductants with inexpensive electricity. Paired electrolysis refers to processes in which reactions at both electrodes are desirable. These maximize the energy economy by avoiding the waste of electrical power on sacrificial reactions. Convergent paired electrolysis is a special case in which reactive intermediates are generated simultaneously at both electrodes and then coupled. However, radical-based reactions of this type remain underexploited. The incorporation of transition-metal catalysis could be beneficial by modulating the formation and utilization of highly reactive radical species. In this article, we introduce our most recent successful implementations of this strategic design.1 Introduction2 Ce/Ni Dual-Catalytic Decarboxylative Arylation3 Fe/Ni Dual-Catalytic Esterification of Aryl Halides4 Conclusion.

4-Isocyanobut-1-ene reacted rapidly with acetyl bromide to afford an unstable imidoyl bromide adduct. Subsequent in situ cyclization under Heck conditions generated a stable prototropic isomer of 2-acetyl-3-methylpyrrole. The reactivity of this molecule toward ­acids, bases, and oxidants was explored, and its conversion into an α-methylidene γ-lactam was demonstrated. In protonated form, the molecule functioned as a reactive dienophile in Diels–Alder reactions.

An electrophotochemical dual metal-catalyzed protocol for decarboxylative arylation of simple aliphatic carboxylic acids with aryl halides is reported. The relative stabilities of catalytically active metal complexes simultaneously generated at anode and cathode are the key design elements for the success of this convergent paired electrolysis. This new electrophotocatalytic method is mild, robust, and most importantly, capable of accommodating simple primary aliphatic acids including acetic acid - ubiquitous and variegated structural motifs yet remain oddly challenging substrates - directly as native functional groups for decarboxylative C(sp

In this study, novel aerogels of Nicandra physaloides (L.) Gaertn seed gum (NPG) and Nicandra physaloides (L.) Gaertn seed gum/Carboxymethyl chitosan (NPG/CMC) were prepared by freeze-drying method for removing tetracycline (TC) from water. Scanning electron microscope (SEM), X-ray diffraction (XRD),Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) were used to characterize structure and morphology of NPG and NPG/CMC aerogels. The average pore diameter of NPG and NPG/CMC were 3.04 and 1.2 nm, the specific surface areas were 2.67 and 0.73 m2/g, respectively. The maximum adsorption capacity of NPG and NPG/CMC aerogels for TC based on Langmuir isotherm was 266.7 and 332.23 mg/g respectively. Through thermodynamic and kinetic studies, it was found that the adsorption processes of the two adsorbents were spontaneous and followed the pseudo-second-order kinetic model. And the process of NPG adsorption of TC was endothermic, while NPG/CMC was exothermic.

This research prepared a poly-functional material which has outstanding adsorption performance and easily recyclable for Congo red dye removal. The multifunctional gel yarn composed of calcium alginate and nano-magnesium oxide was prepared by wet spinning. For the morphology and structure of MgO/CA composite, the compound product was characterized by Field Emission Scanning Electron Microscope (FE-SEM), Fourier Transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA). Then, the adsorption performance of MgO/CA aerogel for Congo red was studied, including the influence of four factors (adsorbent dosage, pH, initial concentration, contact time), adsorption isotherm, adsorption kinetics and adsorption thermodynamics. The results show that the adsorption properties of MgO/CA aerogel on Congo red largely depend on these factors. The best contact time for MgO/CA aerogel to remove Congo red is 24 h. Besides, the maximum adsorption capacity of the adsorbents is usually very high (312.5, 322.6 and 344.8 mg/g at 303, 313 and 323 K, respectively). The adsorption kinetics can be best described by a pseudo second-order reaction, and the adsorption data agree well with the Langmuir model. Thermodynamic parameters including the changes in entropy (ΔS0), free energy (ΔG0) and enthalpy (ΔH0), and stated that adsorption by the MgO/CA aerogel was endothermic and spontaneous.

In this study, a novel composite aerogel of Nicandra physaloides(L.) Gaertn seed, gum/graphene oxide (NPG/GO), was prepared by using a vacuum freeze drying method for methylene blue (MB) adsorption. The techniques, including Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), were adopted for studying the structure and surface characteristics of NPG/GO, with thermogravimetric analysis (TGA) being adopted for testing thermal properties. The effects of pH value, initial dye concentration, temperature and adsorbent dosage on adsorption performance were elaborately analysed. The adsorption kinetic studies showed that the process of adsorption follows Langmuir isotherm and a pseudo-second-order kinetic model. When the mass ratio of NPG to GO was 1.25:1, the adsorption capacity was the highest. According to Langmuir isotherm, the maximum adsorption capacity of 408.16 mg/g was higher than that of NPG. The specific surface area and average pore diameter of NPG/GO was measured as 2.70 m2/g and 4.8 nm, respectively. Thermodynamic analysis revealed that the adsorption process of methylene blue on NPG/GO was a spontaneous and endothermic process. In general, the prepared nanocomposites were excellent candidates for adsorption and removal process because of simple synthesis, low cost, high efficiency, non-toxicity, environment protection and degradability.

Due to public concern about tetracycline (TC), it is imperative to eliminate this compound from the environment. This article describes the preparation of an efficient and low-cost porous copper alginate/graphene oxide (CA/GO) composite material by freeze-drying. The application of tetracycline removal in the presence of persulfate (PS) was studied. The effects of pH, PS, catalyst dosage and tetracycline concentration on adsorption and degradation were investigated. The synthesized composites were characterized by Scanning electron microscope (SEM), Fourier Transform infrared spectroscopy (FTIR) and Thermogravimetric analysis (TGA). The degradation rate of tetracycline increases with the increase of the compound dose, and decreases with the increase of the initial pH. The adsorption of tetracycline by this catalyst is suitable for Langmuir model. Under the optimum conditions, the removal efficiency of tetracycline was up to 98%. The high reactivity of the composite material is closely related to its redox ability. At the same time, the reusability of the material was studied. After being recycled four times under the same conditions, the removal rate of tetracycline reached about 85%.

In this study, novel composite aerogels of peach gum/activated carbon (PGAC) and peach gum/graphene oxide (PGGO) were synthesized by freeze-drying method for removing methylene blue (MB) from water. The methods of the scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and Brunauer–Emmett–Teller (BET) are used to characterize the adsorbents. It is important to study the effect of distinct factors on MB adsorption. Studies show that using the Langmuir model and Freundlich model can describe the equilibrium isotherms. The maximum adsorption capacities of PGAC and PGGO calculated by Langmuir model were 279.98 mg/g and 360.99 mg/g. Kinetic studies reveals that the kinetic behavior of PGAC and PGGO is more in line with the pseudo-second-order kinetic. The adsorption reaction of MB onto PGAC was endothermic, meanwhile PGGO was exothermic.

Callyspongiolide is a marine-derived macrolide that kills cells in a caspase-independent manner. NCI COMPARE analysis of human tumor cell line toxicity data for synthetic callyspongiolide indicated that its pattern of cytotoxicity correlated with that seen for concanamycin A, an inhibitor of the vacuolar-type H+-ATPase (V-ATPase). Using yeast as a model system, we report that treatment with synthetic callyspongiolide phenocopied a loss of V-ATPase activity including (1) inability to grow on a nonfermentable carbon source, (2) rescue of cell growth via supplementation with Fe2+, (3) pH-sensitive growth, and (4) a vacuolar acidification defect visualized using the fluorescent dye quinacrine. Crucially, in an in vitro assay, callyspongiolide was found to dose-dependently inhibit yeast V-ATPase (IC50 = 10 nM). Together, these data identify callyspongiolide as a new and highly potent V-ATPase inhibitor. Notably, callyspongiolide is the first V-ATPase inhibitor known to be expelled by Pdr5p.

In this study, novel aerogels of

In this study, a novel composite aerogel of

The cyclometalated rhodium, iridium, and ruthenium complexes of N-methoxy-4-nitrobenzamide were synthesized by treatment of N-methoxy-4-nitrobenzamide with [Cp*MCl2]2] (M = Rh and Ir) or [(p-cymene)RuCl2]2 via C–H bond activation. The molecular structures of all these complexes were determined by single-crystal X-ray diffraction analysis. When the cyclometalated rhodium and ruthenium complexes were used as catalysts in the C–H bond functionalization reactions reported before, the desired products were obtained in high yields, proving that these cyclometalated complexes were probably the key catalytic intermediates of the C–H bond functionalization reactions of N-methoxybenzamide derivatives. The stoichiometric reactions of the cyclometalated rhodium, iridium, and ruthenium complexes with diphenylacetylene afforded the corresponding seven-membered metallacycles with insertion of two molecules of diphenylacetylene in 24, 6, and 20% yields, respectively, through the tandem reaction. However, the cyclometalat...

An asymmetric synthesis of (-)-callyspongiolide is described. The route builds the macrolide domain atypically from a disaccharide and a monoterpene without passing through a seco-acid. Chiral iridium catalysis selectively joins fragments. Subsequent degradation of an imbedded butyrolactone via perhemiketal fragmentation affords a stereo- and regio-defined homoallylic alcohol that is engaged directly in a carbonylative macrolactonization. Further elaboration of the polyunsaturated appendage provides the natural product in a particularly direct and flexible manner.

By improving the synthesis process of MOF-525, MOF-525 was grown on the surface of graphene oxide (GO), and thus the MOF-525/GO composite was obtained for the adsorption of tetracycline (TC) in water. MOF-525 and GO can be identified on the surface of MOF-525/GO, and the BET surface area measured is up to 444.49 m2 g−1. MOF-525 and GO are bonded by coordination bonds, and the lattice structure of MOF-525 is retained in the composite. Both GO and MOF-525 have good adsorption properties, the maximum adsorption capacity is 236.7 mg g−1 and 371.5 mg g−1, respectively. The maximum adsorption capacity of MOF-525/GO reaches 413.6 mg g−1, indicating that GO does not weaken the adsorption performance of MOF-525, but further strengthens. The initial adsorption rate of MOF-525/GO for TC was very fast (the adsorption removal rate reached 47% within 2 min), and the adsorption removal amount is almost unchanged after 360 min. Elovich model and Sips model fitted the adsorption process well, revealing that the adsorption process was exothermic reaction dominated by chemisorption and the maximum adsorption capacity was 436 mg g−1. In addition, MOF-525/GO carries a negative charge, and the adsorption performance gradually decreases with the increase of pH value. The adsorption capacity of MOF-525/GO was mainly derived from π-π stacking and hydrogen bonding, and the complexation between Zr and TC was also involved in the rapid adsorption stage.

We describe the re-assignment of configuration previously ascribed to product diastereomers resultant from imidazolidinone-catalyzed conjugate addition of 2-trimethylsiloxyfuran to trans-crotonaldehyde. A modified procedure that uses a diphenylprolinol catalyst was subsequently developed to selectively provide the ‘syn’ diastereomeric product in high enantiomeric excess on decagram scales.

Colorimetric biosensors have been widely applied to mycotoxins testing. However, the colorimetric assay previously reported used a single color to detect one mycotoxin, and there were few reports on the simultaneous detection of multiple mycotoxins. In this work, a colorimetric biosensor for dual mycotoxins detection was developed. A Fe3O4/GO based platform for aflatoxins B1 (AFB1) detection and a Fe3O4@Au based platform for ochratoxin A (OTA) detection were fabricated. The quantification of OTA and AFB1 was respectively achieved by the release of thymolphthalein under alkaline conditions and 3,3′,5,5′-tetramethylbenzidine was catalyzed by Au NPs under acidic conditions. Because of different conditions, two sensing methods didn’t interfere with each other but could provide a higher detection efficiency. The detection range of AFB1 is 5–250 ng·ml−1 and that of OTA is 0.5–80 ng·ml−1. This biosensor has been successfully applied in real sample detection, which has a broad application prospect in fields of food safety.

The amidation reactions of 8-methylquinolines with azides catalyzed by a cationic rhodium(III) complex proceed efficiently to give quinolin-8-ylmethanamine derivatives in good yields via C(sp3)–H bond activation under external oxidant-free conditions. A catalytically competent five-membered rhodacycle has been isolated and characterized, revealing a key intermediate in the catalytic cycle.

Conditions for the title reaction of variously substituted NH isoquinolines with benzoquinone, 2,3-dimethylbenzoquinone or 1,4-naphthoquinone are elaborated which provide spiro compounds in most often quantitative yields.

The oxidative coupling reactions of NH isoquinolones with 1,4-benzoquinone proceeded efficiently to form spiro compounds in the presence of an Ir(III) catalyst through C–H activation. The reactions have a broad range of substrates, with nearly quantitative yields, without the use of external oxidants. For 1,4-naphthoquinone and other substituted 1,4-benzoquinone substrates the reactions also gave high yields with Cu(OAc)2·H2O as an external oxidant. A catalytically competent five-membered iridacycle has been isolated and structurally characterized, thus revealing a key intermediate in the catalytic cycle.

The amidation reactions of 8-methylquinolines with azides catalyzed by a cationic rhodium(III) complex proceed efficiently to give quinolin-8-ylmethanamine derivatives in good yields via C(sp3)–H bond activation under external oxidant-free conditions. A catalytically competent five-membered rhodacycle has been isolated and characterized, revealing a key intermediate in the catalytic cycle.

The amidation reactions of 8-methylquinolines with azides catalyzed by a cationic rhodium(III) complex proceed efficiently to give quinolin-8-ylmethanamine derivatives in good yields via C(sp(3))-H bond activation under external oxidant-free conditions. A catalytically competent five-membered rhodacycle has been isolated and characterized, revealing a key intermediate in the catalytic cycle.

To investigate quantitatively the cooperative binding ability of several beta-cyclodextrin oligomers bearing single or multiligated metal center(s), the inclusion complexation behavior of four bis(beta-cyclodextrin)s (2-5) linked by 2,2'-bipyridine-4,4'-dicarboxy tethers and their copper(II) complexes (6-9) with representative dye guests, i.e., methyl orange (MO), acridine red (AR), rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonic acid (ANS), and sodium 6-(p-toludino)-2-naphthalenesulfonate (TNS), have been examined in aqueous solution at 25 degrees C by means of UV-vis, circular dichroism, fluorescence, and 2D NMR spectroscopy. The results obtained indicate that bis(beta-cyclodextrin)s 2-5 can associate with one or three copper(II) ion(s) producing 2:1 or 2:3 bis(beta-cyclodextrin)-copper(II) complexes. These metal-ligated oligo(beta-cyclodextrin)s can bind two model substrates to form intramolecular 2:2 host-guest inclusion complexes and thus significantly enhance the original binding abilities of parent beta-cyclodextrin and bis(beta-cyclodextrin) toward model substrates through the cooperative binding of two guest molecules by four tethered cyclodextrin moieties, as well as the additional binding effect supplied by ligated metal center(s). Host 6 showed the highest enhancement of the stability constant, up to 38.3 times for ANS as compared with parent beta-cyclodextrin. The molecular binding mode and stability constant of substrates by bridged bis- and oligo(beta-cyclodextrin)s 2-9 are discussed from the viewpoint of the size/shape-fit interaction and molecular multiple recognition between host and guest.