An efficient regioselective bromination protocol of activated coumarins using 2,4,4,6-tetrabromo-2,5-cyclohexadienone

2013 ◽  
Vol 91 (11) ◽  
pp. 1155-1159 ◽  
Author(s):  
Nemai C. Ganguly ◽  
Subhasis Nayek ◽  
Sumanta Chandra
Keyword(s):  
Reaction Medium ◽  
Significant Loss ◽  
Electron Withdrawal ◽  
Wide Assortment

2,4,4,6-Tetrabromo-2,5-cyclohexadienone mediated bromination of a wide assortment of activated coumarins in acetonitrile has been accomplished with high regioselectivity and good to excellent yields. The selectivity and efficiency of bromination were found to be markedly dependent on electronic factors, particularly degree of electron withdrawal from electron-releasing 7-oxygenated substituents to the C-3 position of the α-pyrone moiety by vinylogous resonance and the presence of nucleophilic additives such as water and tetra-n-butylammonium bromide in the reaction medium. The sole by-product of the reaction was converted back to the reagent by oxidation with KBr−KBrO3, which was recycled three times without significant loss of efficiency.

scholarly journals Synthesis, Characterization of Chitosan-Aluminum Oxide Nanocomposite for Green Synthesis of Annulated Imidazopyrazol Thione Derivatives

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1160
Author(s):  
Abir S. Abdel-Naby ◽  
Sara Nabil ◽  
Sarah Aldulaijan ◽  
Ibtisam M. Ababutain ◽  
Azzah I. Alghamdi ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Aluminum Oxide ◽  
Reaction Medium ◽  
Thiol Group ◽  
Docking Studies ◽  
Significant Loss ◽  
Gram Negative Bacteria ◽  
Organic Catalyst ◽  
Group 1

Chitosan-aluminum oxide nanocomposite was synthesized, characterized, and used as a green heterogeneous catalyst to synthesize novel imidazopyrazolylthione derivatives. Nanocomposite polymeric material was characterized by EDS-SEM and XRD. The powerful catalytic activity, and its base character of the nanocomposite, was used to synthesize imidazopyrazolylthione (1) in a good yield compared to traditional cyclocondensation synthesis. Using the nanocomposite catalyst, substitution of the thiol group (1) afforded the corresponding thiourea (2) and the corresponding ester (3). The efficiency of the nanocomposite over the traditional base organic catalyst, Et3N and NaOH, makes it an effective, economic, and reproducible nontoxic catalyst. Moreover, the heterogeneous nanocomposite polymeric film was easily isolated from the reaction medium, and recycled up to four times, without a significant loss of its catalytic activity. The newly synthesized derivatives were screened as antibacterial agents and showed high potency. Molecular docking was also performed for a more in-depth investigation. The results of the docking studies have demonstrated that the docked compounds have strong interaction energies with both Gram-positive and Gram-negative bacteria.

Microwave-assisted Efficient One-pot Synthesis of Nitriles Using Recyclable Magnetite (Fe3O4) Nanoparticles as Catalyst and Water as Solvent: A Greener Approach

2020 ◽  
Vol 10 (4) ◽  
pp. 507-517
Author(s):  
Prashant Chavan ◽  
Suhas Pednekar ◽  
Ramesh Chaughule ◽  
Anushree Lokur
Keyword(s):  
Fe3o4 Nanoparticles ◽  
Reaction Medium ◽  
Chemical Yield ◽  
Significant Loss ◽  
Microwave Assisted Synthesis ◽  
Microwave Activation ◽  
One Pot ◽  
Microwave Assisted ◽  
Magnetite Fe3o4 ◽  
Water As Solvent

Background: There has been an increasing curiosity over the past few years to carry out organic reactions over heterogeneous nanocatalysts. Microwave activation coupled with a nanocatalyst along with water as a reaction medium makes the process further green. Microwave activation as a green process reduces reaction times, enhances product purity and improves chemical yield. Methods: Nitrile group chemistry has been explored by many researchers across the globe owing to its interesting properties and its importance in synthetic chemistry. Despite several methods being available for the synthesis of nitriles, microwave assisted synthesis of nitriles using Fe3O4 nanoparticles appears more promising. The present study is intended at developing a recyclable magnetite (Fe3O4) nanoparticles catalyzed protocol towards the synthesis of organonitrile derivatives using one pot reaction. Results: The above protocol incorporates the use of microwave for heating and water as reaction medium. Several substituted nitriles could be synthesized for excellent yields. The magnetite nanoparticles can be reused for new reaction without significant loss in activity. Conclusion: The experiment makes the protocol simple, environment friendly and economically feasible.

scholarly journals Switchable Access to Amines and Imines from Reductive Coupling of Nitroarenes with Alcohols Catalyzed by Biomass-Derived Cobalt Nanoparticles

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 116 ◽  
Author(s):  
Tao Song ◽  
Yanan Duan ◽  
Xiufang Chen ◽  
Yong Yang
Keyword(s):  
Heterogeneous Catalyst ◽  
Reaction System ◽  
Reaction Medium ◽  
Cobalt Nanoparticles ◽  
Significant Loss ◽  
Reductive Coupling ◽  
Hierarchical Porous ◽  
Borrowing Hydrogen ◽  
High Yields ◽  
First Time

Cobalt nanoparticles modified with N-doped hierarchical porous carbon derived from biomass are found to be a highly efficient, reusable heterogeneous catalyst for the coupling of nitroarenes with alcohols, selectively affording imines and amines via the borrowing hydrogen strategy for the first time. The product selectivity between imine and amine may be precisely tuned by simple alteration of the reaction conditions without changing the catalyst in one reaction system. In this study, a broad set of complex imines and amines was successfully synthesized in good to high yields with various functional groups tolerated for both nitroarenes and alcohols, highlighting the potentially practical utility of the protocol. This heterogeneous catalyst can be easily removed from the reaction medium by external magnet and can be reused at least four times without significant loss in activity and selectivity.

scholarly journals Preparation of Functionalized Superparamagnetic Fe3O4@Dopamine@Metal Ions (Cu+,Ru2+) Nanocomposites and its Catalytic Applications

2020 ◽  
Author(s):  
Renuka Singh ◽  
Shukla Majhi ◽  
Keshav Sharma ◽  
Mohd. Ali ◽  
Chandra Shekhar Pati Tripathi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Metal Ions ◽  
Photoelectron Spectroscopy ◽  
Reaction Medium ◽  
Significant Loss ◽  
Transfer Hydrogenation ◽  
Simple Method ◽  
Catalytic Systems ◽  
X Ray ◽  
Catalytic Applications

<p>In this work, we present a simple method for the synthesis of metal ions stabilized on dopamine modified iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>@DA@M<sup>x+</sup>) and their catalytic applications in important organic transformation reactions. Two different metal ions (Cu<sup>+1</sup> and Ru<sup>2+</sup>) are studied in this work. It is observed that both synthesized Fe<sub>3</sub>O<sub>4</sub>@DA@Cu<sup>+ </sup>and Fe<sub>3</sub>O<sub>4</sub>@DA@Ru<sup>2+ </sup>can effortlessly be separated from the reaction medium by positioning an external magnetic field. Dopamine, which is used as an anchor between Fe<sub>3</sub>O<sub>4</sub> and metal ions, increases the solubility of catalyst in reaction medium and prevents leaching of metal ions from the catalyst surface. Here Fe<sub>3</sub>O<sub>4</sub>@DA@Cu<sup>+ </sup>is used in the synthesis of 1,2,3-triazole derivatives via azide-alkyne cycloaddition reactions and Fe<sub>3</sub>O<sub>4</sub>@DA@Ru<sup>2+ </sup>is used for transfer hydrogenation reaction of various aryl ketones. The Fe<sub>3</sub>O<sub>4</sub>@DA@M<sup>x+</sup> nanocomposite is characterized via powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA) and vibrating-sample magnetometer (VSM). The Fe<sub>3</sub>O<sub>4</sub>@DA@M<sup>x+</sup> catalytic systems can be reused in the reaction mixture up to five times without significant loss in their catalytic activity.</p>

scholarly journals Preparation of Functionalized Superparamagnetic Fe3O4@Dopamine@Metal Ions (Cu+,Ru2+) Nanocomposites and its Catalytic Applications

2020 ◽  
Author(s):  
Renuka Singh ◽  
Shukla Majhi ◽  
Keshav Sharma ◽  
Mohd. Ali ◽  
Chandra Shekhar Pati Tripathi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Metal Ions ◽  
Photoelectron Spectroscopy ◽  
Reaction Medium ◽  
Significant Loss ◽  
Transfer Hydrogenation ◽  
Simple Method ◽  
Catalytic Systems ◽  
X Ray ◽  
Catalytic Applications

<p>In this work, we present a simple method for the synthesis of metal ions stabilized on dopamine modified iron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub>@DA@M<sup>x+</sup>) and their catalytic applications in important organic transformation reactions. Two different metal ions (Cu<sup>+1</sup> and Ru<sup>2+</sup>) are studied in this work. It is observed that both synthesized Fe<sub>3</sub>O<sub>4</sub>@DA@Cu<sup>+ </sup>and Fe<sub>3</sub>O<sub>4</sub>@DA@Ru<sup>2+ </sup>can effortlessly be separated from the reaction medium by positioning an external magnetic field. Dopamine, which is used as an anchor between Fe<sub>3</sub>O<sub>4</sub> and metal ions, increases the solubility of catalyst in reaction medium and prevents leaching of metal ions from the catalyst surface. Here Fe<sub>3</sub>O<sub>4</sub>@DA@Cu<sup>+ </sup>is used in the synthesis of 1,2,3-triazole derivatives via azide-alkyne cycloaddition reactions and Fe<sub>3</sub>O<sub>4</sub>@DA@Ru<sup>2+ </sup>is used for transfer hydrogenation reaction of various aryl ketones. The Fe<sub>3</sub>O<sub>4</sub>@DA@M<sup>x+</sup> nanocomposite is characterized via powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA) and vibrating-sample magnetometer (VSM). The Fe<sub>3</sub>O<sub>4</sub>@DA@M<sup>x+</sup> catalytic systems can be reused in the reaction mixture up to five times without significant loss in their catalytic activity.</p>

Dissociation of immunocomplexes by ionic shock for the development of immunosensors: application to measurement of alpha 1-fetoprotein.

1989 ◽  
Vol 35 (6) ◽  
pp. 1026-1031 ◽  
Author(s):  
J L Boitieux ◽  
M P Biron ◽  
G Desmet ◽  
D Thomas
Keyword(s):  
Reaction Rate ◽  
Enzymatic Reaction ◽  
Reaction Medium ◽  
Oxygen Electrode ◽  
Significant Loss ◽  
Oxygen Production ◽  
Protein Membrane ◽  
On Line ◽  
Immunological Process ◽  
Repeated Use

Abstract We report here our experimental results on the reaction rate of immunological complexes and on potential repeated use of membranes as a result of dissociation of the complexes between alpha 1-fetoprotein and catalase-labeled antibodies by different buffers with various ionic strengths. The measurement consists of an immunological process and an enzymatic reaction. The protein membrane activated by glutaraldehyde for the immobilization of antibodies is fixed over an oxygen electrode. After incubation with antibody/alpha 1-fetoprotein and antibody/alpha 1-fetoprotein antibodies coupled to catalase, the reaction medium is introduced into a continuous-flow cell. Oxygen production by the catalase is measured on-line, with the electrode in contact with hydrogen peroxide. This response is correlated to the alpha 1-fetoprotein concentration of the sample. We show a typical calibration curve between 0.5 and 120 micrograms/L. Replicate (n = 20) equilibrium measurement with the same membrane gave a CV of 2.2%. The reversible immunochemical sensor has been tested for 30 measurements without significant loss of activity.

A New AID for Interpolating and Assessing Collision Strengths and Rate Coefficients

1988 ◽  
Vol 102 ◽  
pp. 107-110
Author(s):  
A. Burgess ◽  
H.E. Mason ◽  
J.A. Tully
Keyword(s):  
Significant Loss ◽  
Impact Excitation ◽  
Rate Coefficients ◽  
Electron Impact Excitation ◽  
Graphical Display ◽  
Practical Procedure ◽  
Positive Ions ◽  
Allowed Transition ◽  
Computational Errors ◽  
Existing Data

AbstractA new way of critically assessing and compacting data for electron impact excitation of positive ions is proposed. This method allows one (i) to detect possible printing and computational errors in the published tables, (ii) to interpolate and extrapolate the existing data as a function of energy or temperature, and (iii) to simplify considerably the storage and transfer of data without significant loss of information. Theoretical or experimental collision strengths Ω(E) are scaled and then plotted as functions of the colliding electron energy, the entire range of which is conveniently mapped onto the interval (0,1). For a given transition the scaled Ω can be accurately represented - usually to within a fraction of a percent - by a 5 point least squares spline. Further details are given in (2). Similar techniques enable thermally averaged collision strengths upsilon (T) to be obtained at arbitrary temperatures in the interval 0 &lt; T &lt; ∞. Application of the method is possible by means of an interactive program with graphical display (2). To illustrate this practical procedure we use the program to treat Ω for the optically allowed transition 2s → 2p in ArXVI.

Effects of sterilization modes on the mechanical strengths of plaster of paris implants

1989 ◽  
Vol 47 ◽  
pp. 890-891
Author(s):  
K. Cowden ◽  
B. Giammara ◽  
T. Devine ◽  
J. Hanker
Keyword(s):  
Gamma Radiation ◽  
Calcium Sulfate ◽  
Significant Loss ◽  
Potassium Sulfate ◽  
Limiting Factors ◽  
Radiation Sterilization ◽  
Plaster Of Paris ◽  
Hardness Tester ◽  
Dry Heat ◽  
Calcium Sulfate Hemihydrate

Plaster of Paris (calcium sulfate hemihydrate, CaSO4. ½ H2O) has been used as a biomedical implant material since 1892. One of the primary limiting factors of these implants is their mechanical properties. These materials have low compressive and tensile strengths when compared to normal bone. These are important limiting factors where large biomechanical forces exist. Previous work has suggested that sterilization techniques could affect the implant’s strength. A study of plaster of Paris implant mechanical and physical properties to find optimum sterilization techniques therefore, could lead to a significant increase in their application and promise for future use as hard tissue prosthetic materials.USG Medical Grade Calcium Sulfate Hemihydrate Types A, A-1 and B, were sterilized by dry heat and by gamma radiation. Types A and B were additionally sterilized with and without the setting agent potassium sulfate (K2SO4). The plaster mixtures were then moistened with a minimum amount of water and formed into disks (.339 in. diameter x .053 in. deep) in polyethylene molds with a microspatula. After drying, the disks were fractured with a Stokes Hardness Tester. The compressive strengths of the disks were obtained directly from the hardness tester. Values for the maximum tensile strengths σo were then calculated: where (P = applied compression, D = disk diameter, and t = disk thickness). Plaster disks (types A and B) that contained no setting agent showed a significant loss in strength with either dry heat or gamma radiation sterilization. Those that contained potassium sulfate (K2SO4) did not show a significant loss in strength with either sterilization technique. In all comparisons (with and without K2SO4 and with either dry heat or gamma radiation sterilization) the type B plaster had higher compressive and tensile strengths than that of the type A plaster. The type A-1 plaster however, which is specially modified for accelerated setting, was comparable to that of type B with K2SO4 in both compressive and tensile strength (Table 1).

High-voltage cytochemistry for three-dimensional observation of nuclei and calculation of total numbers of nuclear pores in retinal Mueller glia

1990 ◽  
Vol 48 (3) ◽  
pp. 956-957
Author(s):  
H. Ishigooka ◽  
S. Ueno ◽  
L.M. Hjelmeland ◽  
M.B. Landers ◽  
K. Ogawa
Keyword(s):  
Nuclear Envelope ◽  
High Voltage ◽  
Three Dimensional ◽  
Reaction Medium ◽  
Nuclear Pores ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
G6pase Activity ◽  
Mueller Glia

Introduction: We have demonstrated that Glucose-6-phosphatase (G6Pase) activity is localized to the endoplasmic reticulum and nuclear envelope of Mueller glia in the normal and pathological guinea pig retina. Using a combination of this cytochemical technique and high voltage electron microscopy, the distribution of nuclear pores could be clearly observed on the nuclear envelope of Mueller glia because of their anatomical lack of reaction products. This technique was developed to study the three-dimensional structure of nuclei and to calculate total numbers of nuclear pores utilizing a computer graphic analysis system in the normal and pathological retina.Materials and methods: Normal and photocoagulated retina of pigmented adult guinea pigs were perfused with a cold mixture of 0.25% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer, and the enucleated globes were hemisected and immersed in the same fixative for 30 min. After sectioning and incubation in the reaction medium for the detection of G6Pase activity by the method of Wachstein-Meisel, the sections were postfixed, dehydrated and embedded in Spurr’s epoxy resin. Serial thick sections (1.0um) were prepared for the observation by a Hitachi high voltage electron microscope (H 1250-M) with an accelerating voltage of 1000 Kv. and pictures were analyzed and three-dimensionally reconstructed by TRI (RATOC Co., Ltd.).

Bidirectional Associations Between Self-Perceptions of Aging and Processing Speed Across 3 Years

GeroPsych ◽  
2017 ◽  
Vol 30 (2) ◽  
pp. 49-59 ◽  
Author(s):  
Anna L. Seidler ◽  
Julia K. Wolff
Keyword(s):  
Processing Speed ◽  
Personal Growth ◽  
Significant Loss ◽  
Path Model ◽  
Outcome Variable ◽  
Beneficial Effects ◽  
Self Perceptions ◽  
Chi Squared ◽  
Perceptions Of Aging ◽  
Bidirectional Associations

Abstract. Background: Previous studies point to a potential relationship between self-perceptions of aging (SPA) and cognitive performance. However, most of these studies are limited by their experimental design. Previous longitudinal studies looked solely at memory as an outcome variable without examining the directionality of effects. The present study examines the direction of effects between two domains of SPA (personal growth and physical losses) and processing speed (PS). Methods: The sample consists of 8,198 participants of the German Ageing Survey (DEAS), aged between 40 and 93 years. A cross-lagged path model was estimated to examine directions of relationships across 3 years via chi-squared difference tests for each domain of SPA. Results: In the unconstrained models, the effect of SPA domain personal growth in 2008 on PS in 2011 and vice versa were marginally significant. For SPA domain physical losses, the effect of SPA on PS was significant, whereas the other direction of the effect did not reach significance. However, the cross-lagged paths of both domains of SPA on PS and vice versa could be set equal without a significant loss of model fit. The resulting associations indicate a significant bidirectional relationship between both domains of SPA and PS. Discussion and conclusion: This study provides initial evidence that SPA can influence trajectories of cognitive decline and vice versa. The results emphasize the detrimental and beneficial effects that stereotypes can have on individuals and add further evidence to the theory of stereotype embodiment.

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