Electrochemically mediated decarboxylative acylation of N-nitrosoanilines with α-oxocarboxylic acids

An efficient palladium-catalyzed electrooxidation C–H acylation reaction of N-nitrosoanilines with α-oxocarboxylic acids was developed. The anodic oxidation of the Pd(Ⅱ) intermediate was found to be the key to complete the reaction. In this case, the N-nitroso group was observed to be an effective directing group for C–H activation reaction. Moreover, the synthetic transformation of derivatives of natural products(L-menthol, dehydroepiandrosterone, and pregnenolone) was successfully realized. Fi...     

Two-dimensional correlation analysis of continuous online in situ ATR-FTIR on the adsorption of butyl xanthate at the surface of α-PbO

The adsorption behavior of butyl xanthate on the surface of lead oxide was investigated using continuous online in situ attenuated total reflectance Fourier transform infrared(ATR-FTIR) spectroscopy technique and two dimensional(2D) correlation analysis.The adsorbed layer studied was prepared by coating α-PbO particles onto the surfaces of the ZnSe crystal.The appearance of spectral peaks at 1203 cm~(-1),1033 cm~(-1) and their red shift indicated the formation and aggregation of xanthate at the surface of α-PbO.According to 1R intensity changes after rinsing with deionized water and a NaOH solution,the adsorption was proved to be a chemisorption type.The competition between xanthate and OH for the surfaces leads to desorption of xanthate at higher pH.The technique of 2D correlation ATR-FTIR spectroscopy was used to evaluate the changing order of spectral intensities in the adsorption process,and the results indicated that xanthate micelles were formed at the surfaces.The adsorption kinetics of butyl xanthate was found to be a pseudo-second-order reaction model and the adsorption capacity of butyl xanthate at α-PbO was as high as 281 mg g~(-1) after 150 min.     

Multi-walled carbon nanotubes as a ligand in nickel α-diimine based ethylene polymerization

Two novel heterogeneous nickel ?-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall(s) in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PE?mmol?1 Ni?h?1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 g?mol?1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.     

Enantiomeric separation of α-phenylethylamine and its derivatives by series coupled open tubular columns

A series coupled fused-silica open tubular columns of a chiral and an achiral stationary phase were used to achieve the enantiomeric separation of a-phenylethylamine, o,m,p-methyl-and o,m,p-methoxy-a-phenylethylamine. A simplified equation describing the retention values of series coupled columns was derived, which relates the capacity factors of series coupled columns to the capacity factor of individual columns, their lengths, inlet and outlet pressure. Very good agreement was obtained both between calculated values by this equation and those by Krupcik's equation and between values measured experimentally and calculated theoretically. By means of this simplified equation a computer program was developed in locating the operating range of optimum amin, enantiomeric separation of all a-phenylethylamine and its derivatives were achieved in a single run.     

Distribution of α-, β-, and γ-Phases in a Multi-flow Injection-molded Hierarchical Structure

In the current work, a custom-made vibration injection molding device that can provide oscillatory pressure was utilized to create an injection-molded hierarchical structure. Growth competition among α, β, and γ phases in the injection-molded structure can be studied because of the presence of this hierarchical structure, wherein shish-kebab and spherulite layers were arranged alternately along the thickness direction. The γ crystals only existed in layers subjected to high pressure and shear stress, whereas β crystals formed between the shear layers. The change in trend of the γ fraction was similar to that of parent-to-daughter ratio. In addition, this hierarchical and alternating crystal structure can sharply increase the mechanical properties.     

Effect of Temperature-responsive Solution Behavior of PNIPAM-bPPEOMA-b-PNIPAM on Its Inclusion Complexation with α-Cyclodextrin

The effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with α-cyclodextrin was studied. The triblock polymer was prepared by reversible addition-fragmentation chain transfer(RAFT) polymerization and formed inclusion complexes(ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of α-CD units. For comparison, PPEOMA homopolymer was prepared and the inclusion complexation with α-CD was also studied. The ICs were prepared with α-CD when the polymer was in different conformations by changing the temperature, and the formed ICs were characterized by XRD, 1H-NMR, TGA and DSC. The solutions of the ICs show temperature-responsive clear/turbid transition or fluidic emulsion/gel transition depending on the concentration of the α-CD added, and the stoichiometry determined by 1H-NMR and TGA indicates that the stoichiometry of EO to α-CD of the resulted ICs increases with increasing of temperature.     

Synthesis of unnatural N-glycosyl α-amino acids via Petasis reaction

A convenient and efficient protocol for the synthesis of unnatural N-glycosyl a-amino acids was developed.Condensation of 1,3,4,6-tetra-O-actyl-β-D-glucosamine hydrochloride,alkenyl boronic acid,and glyoxylic acid was achieved in CH_2C1_2 to give the derivatives of 2-(N-glycosyl)aminobut-3-enoic acid which may find applications in glycobiology research and medicinal chemistry.     

FLUORESCENCE SPECTRA OF EXCIPLEX BETWEEN α,ω-GLYCOL DIBENZOATES AND PROTON

In this paper, the interaction between α, ω-glycol dibenzoates and trifluoroacetic acid has been studied. It has been demonstrated by absorption spectra that charge transfer complex does not form between them in the ground state. But in the excited state, exciplex was formed between excited a, ω-glycol dibenzoates and trifluoroacetic acid. By means of isotopic effect, changing of trifluoroacetic acid by phosphoric acid and adding buffer solution etc., it was proved that exciplex was formed between excited α, ω-glycol dibenzoates and proton. It is very interesting to observe that not only exciplex was formed but triple exciplex was formed also.     

The Mobility of Threaded α-Cyclodextrins in PR Copolymer and Its Influences on Mechanical Properties

The methylated polyrotaxane(Me PR) copolymer was prepared via the methylation of hydroxyl of threaded α-cyclodextrin(α-CDs) in polyrotaxane(PR) copolymer by CH_3I/Na H. Its structure was characterized by GPC, IR and NMR. The WXRD and TGA measurements showed the destruction of channel-like crystalline structure in Me PR copolymer. The sliding of threaded α-CDs along PEG axis in PR and Me PR copolymers was demonstrated by their dielectric spectra that also evidenced the presence of rotating of threaded α-CDs around PEG axis in Me PR copolymer. The frequent and vigorous molecular mobility in Me PR and PR copolymers was also verified by dynamic mechanical analysis(DMA) and rheological measurement, which was possibly assigned to the sliding and rotating of threaded α-CDs. DMA and rheological results showed that the mobility of α-CDs could simultaneously strengthen and toughen PR copolymer proved by stress-stain curves. In this paper, we report the CD mobility in PR and Me PR copolymers. The macroscopic behaviors of PR copolymer, such as mechanical properties in solid state, were also found to be benefited from CD mobility.     

Noncompetitive enzyme immunoassay for α-fetroprotein using flow injection chemiluminescence

A novel, direct noncompetitive flow injection enzyme immunoassay for α-fetoprotein (AFP) was developed by enhanced chemiluminescence detection. The method was based on off-line incubation of AFP and horseradish peroxidase (HRP)-labeled anti-AFP, and then trapping of the unbound enzyme conjugate by an immunoaffinity column filled with AFP-modified Sepharose. The immunocomplex formed in incubation passed through the column and then was directly detected by a postcolumn chemiluminescence technique. The optimal conditions for the immunoassay procedure and chemiluminescence detection were established. At a 1:10 dilution of enzyme conjugate solution, the linear range for chemiluminescence detection of AFP was from 2.0 to 75 ng/mL with a correlation coefficient of 0.993 and a coefficient of variation of 2.67% at 30 ng/mL. The detection limit was 0.5 ng/mL. This method was flexible, sensitive, and rapid. The immunoaffinity column of 200 μL could be repeatedly used 100 times without a single decrease. The whole assay time including the preincubation step was only 30 min for one sample.     

A NEW BIFUNCTIONAL CHELATING AGENT α,ε-N,N''''-BIS(L-CYSTEINYL)-L-LYSINE FOR RADIOLABELLING OF MONOCLONAL ANTIBODIES WITH TECHNETIUM-99M

α,ε-N,N'-bis(L-cysteinyl)-L-lysine was synthesized and char-acterized for the first time.It was then employed as a bifunctional chelatingagent to chelate technetium-99m and subsequently conjugated to fragmentF(ab')_2 of anti-gastric tumor monoclonal antibody 3G9.The radiolabelledantibody was satisfactorily stable and immunoreactive.     

Microwave-assisted synthesis of α-hydroxy aromatic ketones from α-bromo aromatic ketones in water

A reaction ofα-bromo aromatic ketones in water with microwave irradiation gave the correspondingα-hydroxy aromatic ketones in good yields.The use of microwaves was found to significantly improve yields and shorten the reaction time.This reaction afforded a very clean,convenient method for the synthesis ofα-hydroxy aromatic ketones.     

Utilization of α-olefins obtained by pyrolysis of waste high density polyethylene to synthesize α-olefin-succinic-anhydride based cold flow improvers

A new route of utilization of α-olefin rich hydrocarbon fractions obtained by waste polymer pyrolysis was investigated. α-olefin-succinic-anhydride intermediate-based pour point depressant additives for diesel fuel were synthesized, in which reactions needed α-olefins were obtained by pyrolysis of waste high-density polyethylene (HDPE). Fraction of α-olefins was produced by the de-polymerization of plastic waste in a tube reactor at 500℃ in the absence of catalysts and air. C17～22 range of mixtures of olefins and paraffins were separated for synthesis and then, these hydrocarbons were reacted with maleic-anhydride (MA) for formation of α-olefin-succinic-anhydride intermediates. The olefin-rich hydrocarbon fraction contained approximately 60% of olefins, including 90%～95% α-olefins. Other intermediates were produced in the same way by using commercial C20 α-olefin instead of C17～22 olefin mixture. The two different experimental intermediates with number average molecular weights of 1850g/mol and 1760g/mol were reacted with different alcohols: 1-butanol, 1-hexanol, 1-octanol, i-butanol, and c-hexanol to produce their ester derivatives. The synthesized ten experimental pour point depressants were added in different concentrations to conventional diesel fuel, which had no other additive content before. The structure and efficiency of experimental additives were followed by different standardized and non-standardized methods. Results showed that the experimental additives on the basis of the product of waste pyrolysis were able to decrease not only the pour but also the cloud point and cold filter plugging point (CFPP) of diesel fuel, whose effects could be observed even if the concentration of additives was low. Furthermore, all additives had anti-wear and anti-friction effects in diesel fuel.     

A simple and convenient method for direct α-chlorination of ketones with ammonium chloride and Oxone~

When ketones were treated with ammonium chloride and Oxone~ in MeOH at room temperature,a directα-chlorination of ketones was occurred and a series of the corresponding a-chloroketones were obtained in moderate to good yields after 24 h.In this reaction,ammonium chloride was used as the source of chlorine and Oxone~ was used as an oxidant.This method was simple, convenient and providing a novel procedure for preparation of a-chloroketones.     

Enhanced conversion of α-cellulose to 5-HMF in aqueous biphasic system catalyzed by FeCl_3-CuCl_2

This study was to investigate the optimal additions of the cellulose decomposition reaction to obtain the most yield of 5-HMF and other furan derivatives in various biphasic systems with FeCl_3-CuCl_2 mixed catalysts,and explore its depolymerization kinetics.A series of controllable reactions have been performed under mild environmentally friendly atmosphere.The experiment results showed that49.13 wt% of 5-HMF was the maximum production along with 2.98 wt% other furan derivatives catalyzed by mixed Lewis acid FeCl_3-CuCl_2 under the two phases which included high concentration NaCl aqueous phase and n-butanol organic phase at 190℃ for 45 min.The conclusion suggested that two-phase systems benefited the yield of 5-HMF,furan derivatives via extracting the target products from reaction phase to organic phase to avoid rehydration of 5-HMF.The kinetic calculation revealed the conversion with mixed catalysts had lower reaction apparent activation energy(21.65 kJ/mol,190-230℃) and the reaction rate was faster than that with acid-based catalysts.Based on experiment exploration,the probable mechanism of cellulose decomposition with FeCl_3-CuCl_2 was proposed.     

Conformation Disturbance of CopC by α-Naphthylamine

It is known that urea and guanidine hydrochloride(GuHCl) induce conformational change of proteins in a certain range of molar ratios. In our research,α-naphthylamine(NA) above 10-4 mol/L at pH 7.0 was discovered to perturb the conformation of CopC,a copper resistant protein with a Greek β-barrel motif; this was reflected by the greater fluorescence quenching and red-shifted emission peak of CopC. The conformation change of CopC was also verified in acrylamide collision experiment by comparing quenching leve...     

Quantitative High-Performance Liquid Chromatographic Determination of Neurotoxin β-ODAP and α- isomer in Grass Pea(Lathyrus sativus)

Grass pea (Lathyrus sativus) is leguminous crop cultivated in India,Bangladesh and Ethiopia, where it is a major protein source for people in the lowest income groups[1] .However, excessive ingestion of this pulse can lead to irreversible paralysis of the legs-a disease known as neurolathyrism or lathyrism.the causative agent was reported to be the non-protein amino acids,β-N-L-oxalyl-α,β-diaminopropionic acid (β-ODAP, sometimes, referred to as BOAA)[2]. The α-isomer of ODAP, α-N-oxaly 1-α,β-diaminopropionic acid, has been shown to be nontoxic to chicks and mice[3]. Lathyrus sativus shows good adaptation to the low rainfall conditions of northwestern China. It grows also in poor soil and is resistant to salt and flood. Our group was exploring to breed low or zero toxin varieties of Lathyrus sativus as grain crops for human consumption and as protein-rich feed for animals. So it is necessary to develop a method to detemine the toxin suitablefor differenth pu rpose.     

Synthesis of α-Bromine- Terminated Polystyrene Macroinitiator and Its Initiation of MMA Polymerization by ATRP

In the present paper the synthesis of block copolymers via the transformation from living anionic polymerization (LAP) to atom transfer radical polymerization (ATRP) was described. Α-Bromine-terminated polystyrenes(PStBr) in the LAP step was prepared by using n-BuLi as initiator, tetrahydrofuran (THF) as the activator, α-methylstyrene (α-MeSt) as the capping group and liquid bromine (Br2) as the bromating agent. The effects of reaction conditions such as the amounts of α-MeSt, THF, and Br2 as well as molecular weight of polystyrene on the bromating efficiency (BE) and coupling extent (CE) were examined. The present results show that the yield of PStBr obtained was more than 93.8% and the coupling reaction was substantially absent. PStBr was further used as the macroinitiator in the polymerization of methyl-methacrylate(MMA) in the presence of copper(Ⅰ) halogen and 2,2-bipyridine(bpy) complexes. It was found that the molecular weight of the resulted PSt-b-PMMA increased linearly with the increase of the conversion of MMA and the polydispersity was 1.2-1.6. The structures of PStBr and P(St-b-MMA) were characterized by 1H NMR spectra.     

Study on the α-cyclodextrin/poly(ethylene glycol) self-assembly supramolecular nanoparticles for drug delivery

This paper reports the synthesis and drug delivery properties of a novel supramolecular nanoparticle.α-Cyclodextrins(α-CD) were threaded on cinnamic acid modified poly(ethylene glycol) to form inclusion complex nanoparticles by supramolecular self-assemble.The anti-tumor drug doxorubicin was loaded in the nanoparticles and released in vitro to study the drug release behavior and the anti-tumor effects.The structure and morphology of the nanoparticles were characterized by nuclear magnetic resonance,X-ray di...     

Preparation of porous α-Fe2O3-supported Pt and its sensing performance to volatile organic compounds

Porous α-Fe2O3 was synthesized by a simple hydrothermal treatment of FeCl3 aqueous solution followed by a calcination process. In the synthesis of porous α-Fe2O3, no templates or pore-directing agents were used. The as-prepared porous α-Fe2O3 was further employed as a support for loading Pt nanoparticles. The gas sensing performance of the obtained porous α-Fe2O3-supported Pt to VOCs was investigated. The sensor presented a high response and fast response-recovery characteristic to several VOCs including acetone, ether, methanol, ethanol, butanol and hexanol. Meanwhile, it exhibited a much higher response than the pure α-Fe2O3 at the operating temperature of 260°C. The enhanced sensing properties may be related to the unique porous structure of the α-Fe2O3 support and the promoting effect of active Pt nanoparticles for the sensing reactions.