Copper‐Catalyzed Cyclization and Azidation of γ,δ‐Unsaturated Ketone O‐Benzoyl Oximes

An intramolecular imination/azidation sequence has been realized through the tetrakis(acetonitrile)copper(I) hexafluorophophate [Cu(CH₃CN)₄PF₆]‐catalyzed reaction of γ,δ‐unsaturated ketone O‐benzoyl oximes with trimethylsilyl azide (TMSN₃). The reaction proceeds via the copper‐mediated N O cleavage and subsequent C N forming 5‐exo cyclization. The thus formed intermediate is then azidated to afford the corresponding dihydropyrrole product. Preliminary mechanistic investigations suggest that the cyclization step does not involve a radical intermediate.

     

Structural elucidation and iron oxidation states in situ formed β‐Ca3(PO4)2/α‐Fe2O3 composites

A detailed structural analysis on the in situ synthesized β‐Ca₃(PO₄)₂/α‐Fe₂O₃ composites is demonstrated. Compositional ratios, the influence and occupancy of iron at the β‐Ca₃(PO₄)₂ lattice, oxidation state of iron in the composites are derived from analytical techniques involving XRD, FT‐IR, Raman, refinement of the powder X‐ray diffraction and X‐ray photoelectron spectroscopy. Iron exists in the Fe³⁺ state throughout the investigated systems and favors its occupancy at the Ca²⁺(5) site of β‐Ca₃(PO₄)₂ until critical limit, and thereafter crystallizes as α‐Fe₂O₃ at ambient conditions. Fe³⁺ occupancy at the β‐Ca₃(PO₄)₂ lattice yields a Ca₉Fe(PO₄)₇ structure that is isostructural with its counterpart. A strong rise in the soft ferromagnetic behavior of β‐Ca₃(PO₄)₂/α‐Fe₂O₃ composites is obvious that depends on the content of α‐Fe₂O₃ in the composites. Overall, the diverse level of iron inclusions at the calcium phosphate system with a Ca/P ratio of 1.5 yields a structurally stable β‐Ca₃(PO₄)₂/α‐Fe₂O₃ composites with assorted compositional ratios.     

Gold(I)‐Catalyzed Tandem Alkoxylation/Lactonization of γ‐Hydroxy‐α,β‐Acetylenic Esters

The formation of 4‐alkoxy‐2(5H)‐furanones was achieved via tandem alkoxylation/lactonization of γ‐hydroxy‐α,β‐acetylenic esters catalyzed by 2 mol% of [2,6‐bis(diisopropylphenyl)imidazol‐2‐ylidine]gold bis(trifluoromethanesulfonyl)imidate [Au(IPr)(NTf₂)]. The economic and simple procedure was applied to a series of various secondary propargylic alcohols allowing for yields of desired product of up to 95%. In addition, tertiary propargylic alcohols bearing mostly cyclic substituents were converted into the corresponding spiro derivatives. Both primary and secondary alcohols reacted with propargylic alcohols at moderate temperatures (65–80 °C) in either neat reactions or using 1,2‐dichloroethane as a reaction medium allowing for yields of 23–95%. In contrast to [Au(IPr)(NTf₂)], reactions with cationic complexes such as [2,6‐bis(diisopropylphenyl)imidazol‐2‐ylidine](acetonitrile)gold tetrafluoroborate [Au(IPr)(CH₃CN)][BF₄] or (μ‐hydroxy)bis{[2,6‐bis(diisopropylphenyl)imidazol‐2‐ylidine]gold} tetrafluoroborate or bis(trifluoromethanesulfonyl)imidate – [{Au(IPr)}₂(μ‐OH)][X] (X=BF₄, NTf₂) – mostly stop after the alkoxylation. Analysis of the intermediate proved the exclusive formation of the E‐isomer which allows for the subsequent lactonization.     

Binuclear Iron(III) Phthalocyanine(μ‐Oxodimer)‐Catalyzed Oxygenation of Aromatic Hydrocarbons with Iodosylbenzene Sulfate and Iodosylbenzene as the Oxidants

Two binuclear iron(III) phthalocyanine‐(μ‐oxodimer) complexes were tested in catalytic oxygenation reactions of several aromatic hydrocarbons using iodosylbenzene (PhIO)_n or oligomeric iodosylbenzene sulfate [(PhIO)₃SO₃]_n as the oxidants. Results of this study demonstrate that [(PhIO)₃SO₃]_n is the most reactive oxygenating reagent that can be used as a safe and convenient alternative to the thermally unstable and potentially explosive iodosylbenzene. The pyridine‐containing binuclear μ‐oxobis{iron(III)‐pyridino[3,4]‐9(10),16(17),23(24)‐tri‐tert‐butyltribenzoporphyrazine} is significantly more active as compared to the traditional μ‐oxobis[iron(III)‐2,9(10),16(17),23(24)‐tetra‐tert‐butylphthalocyanine].     

Synthesis and characterization of polyimide‐γ‐Fe2O3 nanocomposites

Novel polyimide‐γ‐Fe₂O₃ hybrid nanocomposite films (PI/γ‐Fe₂O₃) has been developed from the poly(amic acid) salt of oxydianiline with different weight percentages (5, 10, 15 wt %) of γ‐Fe₂O₃ using tetrahydrofuran (THF) and N,N‐dimethylacetamide (DMAc) as aprotic solvents. The prepared polyimide‐γ‐Fe₂O₃ nanocomposite films were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy (FTIR), scanning electron micrograph (SEM), transmission electron micrograph (TEM), X‐ray diffraction (XRD), ¹³C‐NMR, and thermal analysis (TGA/DSC) techniques. These studies showed the homogenous dispersion of γ‐Fe₂O₃ in the polyimide matrix with an increase in the thermal stability of the composite films on γ‐Fe₂O₃ loadings. Magnetization measurements (magnetic hysteresis traces) have shown very high values of coercive force indicating their possible use in memory devices and in other related applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 834–840, 2007     

Polyaniline doped with α, ω‐alkanedisulfonic acids: preparation and characterization

The use of α, ω‐alkanedisulfonic acid, HO₃S(CH₂)_nSO₃H (n = 1, 4, 6 and 12), as a dopant for polyaniline (PANi) was investigated. This series of disulfonic acids with varying chain lengths were synthesized and used in the doping of PANi. The doped polymers showed conductivity in the range 10^?2 to 10^?1 S cm^?1. Thermal studies showed that the doped polymers, depending on the chain length of α,ω‐alkanedisulfonic acid, were stable up to ca 300 °C and the thermal stability decreased with increasing dopant chain length. The thermal stability of α,ω‐alkanedisulfonic acid‐doped PANi was higher than that of alkanesulfonic acid‐doped PANi which typically degrades around 250 °C, suggesting a moderately broader processing window for α,ω‐alkanedisulfonic acid‐doped PANi for blending with other thermoplastics. Copyright © 2012 Society of Chemical Industry     

Mechanistic insights into methanol‐to‐olefin reaction on an α‐Mn2O3 nanocrystal catalyst

The synthesis and utilization of an α‐Mn₂O₃ nanocrystal catalyst for methanol‐to‐olefin reaction is described. A methanol conversion of 35% and a maximum selectivity of 80% toward ethylene were obtained at 250^°C. In particular, formaldehyde, a primary intermediate for the reaction, was used to produce ethylene via a coupling reaction. A conversion of 45% and a selectivity of 66% to ethylene were achieved at 150^°C in a formaldehyde stream. In situ diffuse reflectance infrared Fourier transform spectra reveal the formation of the surface CH₂‐containing species during reaction, which implies that the main pathway for formaldehyde coupling is probably through interactions of those intermediates. In addition, the weakly adsorbed oxygen on the α‐Mn₂O₃ nanocrystal surface was found to play an important role in this reaction. © 2012 American Institute of Chemical Engineers AIChE J, 2012     

Negative effect of stretching on the development of β‐phase in β‐nucleated isotactic polypropylene

On the premise that shear in the slit die of an extruder was minimized as far as possible, β‐nucleated isotactic polypropylene (iPP) was extruded. Simultaneously, once the extrudate (in the melt state) left the die exit, it was stretched at various stretching rates (SRs). For iPP with a low content of β‐nucleating agent (β‐NA), the crystallinity of β‐phase (X_β) initially increases with increasing SR, and then decreases slightly with further increase in SR. However, for iPP containing a higher content of β‐NA, with increasing SR, X_β decreases monotonically, indicating a negative effect of SR on β‐phase formation. Small‐angle X‐ray scattering and polarized optical microscopy experiments reveal that, when SR is less than 30 cm min^?1, the increasing amount of row nuclei induced by increasing SR is mainly responsible for the increase of X_β. In contrast, when SR exceeds 30 cm min^?1, the overgrowth of shish structures unexpectedly restrains the development of β‐phase, and spatial confinement is considered as a better explanation for the suppression of β‐phase. Copyright © 2011 Society of Chemical Industry     

The Synthesis of trans‐Perhydroindolic Acids and their Application in Asymmetric Domino Reactions of Aldehyde Esters with β,γ‐Unsaturated α‐Keto Esters

(2S,3aR,7aS)‐Perhydroindolic acid, the key intermediate in the synthesis of trandolapril, and its trans‐isomers, were readily prepared. These proline‐like molecules are unique in that they contain a rigid bicyclic structure, with two hydrogen atoms trans to each other at the bridgehead carbon atoms. These molecules were used successfully as chiral organocatalysts in asymmetric domino Michael addition/cyclization reactions of aldehyde esters with β,γ‐unsaturated α‐keto esters. They proved to have excellent catalytic behavior, allowing for the synthesis of multi‐substituted, enantiomerically enriched hemiacetal esters. Under optimal conditions (using 10 mol% catalyst loading), a series of β,γ‐unsaturated α‐keto esters was examined with up to 99% de, ee and yield, respectively. Additionally, the enantiomerically enriched hemiacetal esters could be readily transformed into their corresponding bioactive pyrano[2,3‐b]pyrans (possessing a multi‐substituted bicyclic backbone).     

Mechanistic study of Sn(Oct)2‐catalyzed ε‐caprolactone polymerization using Sn(Oct)2/BF3 dual catalyst

A novel method was used to investigate the mechanism of Sn(Oct)₂‐catalyzed ε‐caprolactone polymerization by using Sn(Oct)₂/BF₃ dual catalyst. The bulk polymerization was conducted at 110 and 130°C with different Sn(Oct)₂/BF₃ ratios. The polymerization kinetics was followed using gel permeation chromatography, and the molecular structures of the low‐molecular weight polymers were examined using ¹H‐nuclear magnetic resonance (NMR). A polymerization induction period was observed in polymerizations containing the Sn(Oct)₂ catalyst, but it was not observed in the system containing only BF₃. After the induction period, BF₃ and Sn(Oct)₂ initiated the polymerization separately. For Sn(Oct)₂ catalyst with no purposely added alcohol, the actual initiation species is a tin hydroxide species formed in situ by the reaction of Sn(Oct)₂ and adventitious water. For BF₃ catalyst, the active species is the protonic acid formed by the reaction of BF₃ with the adventitious water. When mixed, the Sn(Oct)₂ reacts with the adventitious water faster than the BF₃, preventing the BF₃ catalyzing any polymerizations during the induction period. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and Pharmacological Evaluation of α4β2 Nicotinic Ligands with a 3‐Fluoropyrrolidine Nucleus

Nicotinic acetylcholine receptors (nAChRs) play an important role in many central nervous system disorders such as Alzheimer’s and Parkinson’s diseases, schizophrenia, and mood disorders. The α₄β₂ subtype has emerged as an important target for the early diagnosis and amelioration of Alzheimer’s disease symptoms. Herein we report a new class of α₄β₂ receptor ligands characterized by a basic pyrrolidine nucleus, the basicity of which was properly decreased through the insertion of a fluorine atom at the 3‐position, and a pyridine ring carrying at the 3‐position substituents known to positively affect affinity and selectivity toward the α₄β₂ subtype. Derivatives 3‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)‐5‐(phenylethynyl)pyridine ( 11 ) and 3‐((4‐fluorophenyl)ethynyl)‐5‐(((2S,4R)‐4‐fluoropyrrolidin‐2‐yl)methoxy)pyridine ( 12 ) were found to be the most promising ligands identified in this study, showing good affinity and selectivity for the α₄β₂ subtype and physicochemical properties predictive of a relevant central nervous system penetration.     

Structural insights in Dy3+‐doped β‐Tricalcium phosphate and its multimodal imaging characteristics

A series of Dysprosium (Dy³⁺) doped β‐Tricalcium phosphate [β‐TCP, β‐Ca₃(PO₄)₂] were developed for applications in magnetic resonance imaging (MRI) and computed tomography (CT). Characterization studies confirmed the Dy³⁺ occupancy at Ca²⁺(1), Ca²⁺(2), and Ca²⁺(3) lattice sites of β‐Ca₃(PO₄)₂ and its substitution limit was determined as 4.35 mol%. The transitions from the ⁶H_15/2 ground state to various excited energy levels is validated by the characteristic absorption peaks of Dy³⁺. Luminescence studies inferred two intense bands at 480 and 572 nm due to ⁴F_9/2→⁶H_15/2 (blue) and ⁴F_9/2→⁶H_13/2 (yellow) transitions of Dy³⁺. The paramagnetic and nontoxic behavior of Dy³⁺‐doped β‐Ca₃(PO₄)₂ were confirmed from magnetic and MTT tests, respectively. Dy³⁺ in the host induces a high X‐ray absorption ability for X‐ray computed tomography (CT) and showed efficient contrast T₂‐enhancing modality. Thus the proposed system could be used as a promising probe for multimodality with optical imaging, computed tomography and magnetic resonance imaging.     

Synthesis and characterization of polyrotaxanes comprising α‐cyclodextrins and poly(ε‐caprolactone) end‐capped with poly(butyl methacrylate)s

Biodegradable polyrotaxane‐based triblock copolymers were synthesized via the bulk atom transfer radical polymerization (ATRP) of n‐butyl methacrylate (BMA) initiated with polypseudo‐rotaxanes (PPRs) built from a distal 2‐bromoisobutyryl end‐capped poly(ε‐caprolactone) (Br‐PCL‐Br) with α‐cyclodextrins (α‐CDs) in the presence of Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine at 45 ºC. The structure was characterized in detail by means of ¹H NMR, gel permeation chromatography, wide‐angle X‐ray diffraction, DSC and TGA. When the feed molar ratio of BMA to Br‐PCL‐Br was changed from 128 to 300, the degree of polymerization of PBMA blocks attached to two ends of the PPRs was in the range 382 ? 803. Although about a tenth of the added α‐CDs were still threaded onto the PCL chain after the ATRP process, the movable α‐CDs made a marked contribution to the mechanical strength enhancement, blood anticoagulation activity and protein adsorption repellency of the resulting copolymers. Meanwhile, they could also protect the copolymers from the attack of H₂O and Lipase AK Amano molecules, exhibiting a lower mass loss as evidenced in hydrolytic and enzymatic degradation experiments. © 2013 Society of Chemical Industry     

Bio‐Based Hybrid Magnetic Latex Particles Containing Encapsulated γ ‐Fe2O3 by Miniemulsion Copolymerization of Soybean Oil‐Acrylated Methyl Ester and Styrene

This work reports the use of acrylated fatty acid methyl ester (AFAME) as a biomonomer for the synthesis of bio‐based hybrid magnetic particles poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ produced by miniemulsion polymerization. Poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ can be tailored for use in various fields by varying the content of AFAME. The strategy employed is to encapsulate superparamagnetic iron oxide nanoparticles (SPIONs) as γ‐Fe₂O₃ into a styrene/AFAME‐based copolymer matrix. Raman spectroscopy is employed to ensure the formation of the SPIONs (γ‐Fe₂O₃) obtained by a co‐precipitation technique followed by oxidation of Fe₃O₄. The functionalization of SPIONs with oleic acid (OA) is carried out to increase the SPIONs–monomer affinity. The presence of OA on the surface of γ‐Fe₂O₃ is certified by identification of main absorption bands by fourier‐transform infrared spectroscopy (FTIR). Thermal analysis (differential thermogravimetry/differential thermo analysis and differential scanning calorimetry) results of poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ show an increase in AFAME content leading to a lower copolymer glass transition temperature (T _g). Dynamic light scattering (DLS) measurements result in poly(styrene‐co‐AFAME)/γ‐Fe₂O₃ particles with diameter in the range of 100–150 nm. It is also observed by transmission electron microscopy (TEM) and cryo‐TEM techniques that γ‐Fe₂O₃ particles are successfully encapsulated into the poly(styrene‐co‐AFAME) matrix.     

Optimisation and Evaluation of La0.6Sr0.4CoO3 – δ Cathode for Intermediate Temperature Solid Oxide Fuel Cells

In this work, La_0.6Sr_0.4CoO_{3 – δ}/Ce_{1 – x}Gd_xO_{2 – δ} (LSC/GDC) composite cathodes are investigated for SOFC application at intermediate temperatures, especially below 700 °C. The symmetrical cells are prepared by spraying LSC/GDC composite cathodes on a GDC tape, and the lowest polarisation resistance (R_p) of 0.11 Ω cm² at 700 °C is obtained for the cathode containing 30 wt.‐% GDC. For the application on YSZ electrolyte, symmetrical LSC cathodes are fabricated on a YSZ tape coated on a GDC interlayer. The impact of the sintering temperature on the microstructure and electrochemical properties is investigated. The optimum temperature is determined to be 950 °C; the corresponding R_p of 0.24 Ω cm² at 600 °C and 0.06 Ω cm² at 700 °C are achieved, respectively. An YSZ‐based anode‐supported solid oxide fuel cell is fabricated by employing LSC/GDC composite cathode sintered at 950 °C. The cell with an active electrode area of 4 × 4 cm² exhibits the maximum power density of 0.42 W cm^–2 at 650 °C and 0.54 W cm^–2 at 700 °C. More than 300 h operating at 650 °C is carried out for an estimate of performance and degradation of a single cell. Despite a decline at the beginning, the stable performance during the later term suggests a potential application.     

Preparation of γ‐Fe2O3 Catalysts and their deNOx Performance: Effects of Precipitation Conditions

Magnetic γ‐Fe₂O₃ catalysts were prepared by microwave‐assisted coprecipitation utilizing the direct‐titrate and back‐titrate precipitation technique with different precipitants, namely, (NH₄)₂CO₃, NaOH, Na₂CO₃, and NH₄OH, which were evaluated in the selective catalytic reduction of NO_x with NH₃. The optimum γ‐Fe₂O₃ catalyst preparation method was direct titration with NH₄OH as the precipitant, which exhibits high deNO_x efficiency. This direct titration was effective to maintain the proper crystallization degree of γ‐Fe₂O₃, improve the pore structure, and suppress the formation of α‐Fe₂O₃ phase, being advantageous to get tiny and uniform discrete γ‐Fe₂O₃ particles with high activity in selective catalytic reduction. NH₄⁺‐based precipitants in direct titration leads to an increase of the surface O/Fe atom ratio, and more lattice oxygen sites are exposed to the crystal surface.     

Synthesis of poly(β‐pinene)‐g‐polystyrene from allylic brominated poly(β‐pinene)

Poly(β‐pinene) was brominated by N‐bromosuccinimide on the allylic carbons. Then the brominated product was activated by AlEt₂Cl to initiate the polymerization of styrene to give a β‐pinene/styrene graft copolymer. AlEt₂Cl was selected because it alone could not initiate the polymerization of styrene. The obtained graft copolymer was characterized by GPC, ¹H‐NMR, and DSC measurements, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 599–603, 2000     

A comparative study on the selective hydrogenation of α,β unsaturated aldehyde and ketone to unsaturated alcohols on Au supported catalysts

The hydrogenation of trans,4-phenyl,3-buten,2-one (benzalacetone) and trans,3-phenyl, propenal (cinnamaldehyde) was carried out on Au supported on iron oxides catalysts. Commercial goethite (FeOOH), maghemite (γFe₂O₃) and hematite (αFe₂O₃) were used as supports. The catalytic activity of Au/Fe₂O₃ reference catalyst, supplied by the World Gold Council, was also investigated. Gold catalysts and the parent supports were characterized by BET, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of ammonia (NH₃-TPD) and high resolution transmission electron microscopy (HRTEM).Among the catalysts investigated Au supported on FeOOH shows the highest activity and selectivity to UA in the hydrogenation of unsaturated carbonyl compounds whereas Au supported on αFe₂O₃ are the less active and selective catalysts.The catalytic activity and selectivity to unsaturated alcohols (UA) in the hydrogenation of benzalacetone and cinnamaldehyde are less influenced by the morphology of gold particles and are mainly influenced by the nature of the support.A correlation between the reducibility of the catalysts and the activity and selectivity to UA has been found. Increasing the reducibility of the catalysts both the activity and selectivity to UA increase. These results let us to argue that active and selective sites are formed by negative gold particles formed through the electron transfer from the reduced support to the metal.     

Infrared spectra of γ‐irradiated poly(acrylic acid)–polyacrylamide complex

Samples of polyacrylamide (PAAm), poly(acrylic acid) (PAA), and their complex were γ‐irradiated at different doses, namely 48, 96, and 144 KGy. The examination of the infrared spectra of these samples showed that there are no significant observable changes in their spectral features apart from slight changes in the intensities of the absorption bands. The analysis of the absorbances ratios (A 1700 cm^?1/A 1450 cm^?1) and (A 1650 cm^?1/A 1450 cm^?1), denoted as R₁ and R₂, respectively, showed that these ratios depend on γ‐doses. It was found that in the case of PAA, R₁ assumed linear increase with increasing the dose to 96 KGy and then showed marked decrease. For the complex, R₁ increased slightly by increasing the dose to 96 KGy and then decreased. For PAAm, although irradiation with 48 KGy increases the values of R₂, irradiation with 96 and 144 KGy decreases its value. On the other hand, for the complex, R₂ suggested slight decrease on irradiation with 48 KGy followed by continued increases with increasing the dose up to 144 KGy. The increase in R₁ and R₂ may be due to crosslinking as a result of the formation of free radicals. The decrease in these ratios after irradiation with 96 KGy may be due to degradation. It was concluded that γ‐irradiation has a lower effect on the complex (i.e., the complex has a structure which is different from those of PAA and PAAm). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1619–1623, 2002     

Poly‐α,β‐(3‐hydroxypropyl)‐DL‐aspartamide: A new drug carrier

Poly‐α,β‐(3‐hydroxypropyl)‐DL ‐aspartamide (PHPA) was synthesized by the ring‐open reaction of polysuccinimide (PSI) and 3‐hydroxypropylamine. The polymer was characterized by ¹H‐NMR, ¹³C‐NMR, FTIR, and GPC. Mark–Houwink coefficients were obtained from viscometry and GPC measurements, K = 5.53 × 10⁻³ and α = 0.78 in water. The acute toxicity of PHPA was examined and it revealed no death in ICR mice up to the dose treated of 15.3 kg/kg, and hematological parameters showed no significant difference between treated and control animals. The potential use of PHPA as a drug carrier was also investigated. In a typical case, a contraceptive drug, norethindrone (NET), was bonded to PHPA, and the drug sustained released as long as 120 days an in vitro test. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2411–2417, 2000