Synthesis of coumarins linked with 1,2,3-triazoles under microwave irradiation and evaluation of their antimicrobial and antioxidant activity

A series of coumarin derivatives linked with 1,2,3-triazoles has been synthesized by utilizing the copper catalyzed azide-alkyne cycloaddition reaction and were screened for their antimicrobial and antioxidant properties. Some of the compounds displayed promising antibacterial activities (MIC ranging from 5-150 µg/mL) and moderate antifungal activities as compared to the respective standards. The compounds 4k and 4g displayed good antibacterial activity when compared with the standard, Ciprofloxacin, and 4n exhibited better antifungal activity when compared to other synthesized compounds. The in silico docking studies of the active compounds were carried out against the gyrase enzyme and from those studies, it was acknowledged that 4k possessed significant hydrogen bonding and hydrophobic interactions which could be the plausible reason for its superior activity as compared to the other synthesized compounds. The compounds 4h and 4q showed promising antioxidant activity when compared with the standard, BHT, which could be attributed to the presence of electron donating substituents. © 2020, Sociedad Química de México.Russian Foundation for Basic Research, RFBR: 170300641AThe authors are thankful to the Department of Industrial Chemistry, Kuvempu University for rendering all the facilities to carry out the experiments. Vasiliy Bakulev is thankful to Russian Foundation for Basic Research (Grant # 170300641A)

Anisotropic nanomaterials: structure, growth, assembly, and functions

Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications

Alkali promoted regio-selective hydrogenation of styrene oxide to β-phenethyl alcohol

The selective hydrogenation of styrene oxide to 2-phenyl ethanol (β-Phenethyl alcohol) has been investigated using different catalysts and supports. The effect of reaction conditions such as H2 pressure, agitation speed, concentration of substrate and temperature on the initial rate of reaction was investigated. The complete conversion of styrene oxide was obtained using 1% Pd/C, as a catalyst, under milder temperature (313K) and pressure (2.048 MPa) conditions. 2-phenyl ethanol was selectively formed when alkali was used as a promoter. A plausible mechanistic pathway has also been proposed for the hydrogenation of the styrene oxide to 2-phenyl ethanol

Reaction kinetics of the selective liquid phase hydrogenation of styrene oxide to β -phenethyl alcohol

Liquid phase hydrogenation of styrene oxide using 1% Pd/C and NaOH as a promoter was found to give selectively &#946;-phenethyl alcohol (PEA) under very mild conditions (313-333 K; 0.68-5.5 MPa). The kinetics of this system was investigated by collecting initial rate data in a batch slurry reactor. Rate of hydrogenation was found to decrease beyond a certain concentration of both hydrogen (&gt;3 MPa) and styrene oxide (&gt;0.5 kmol/m<SUP>3</SUP>). A Langmuir-Hinshelwood type rate equation has been proposed based on the initial rate data in the kinetic regime. The model predictions agree very well with the experimentally observed concentration-time data indicating the applicability of the proposed rate model

Role of a co-metal in bimetallic Ni-Pt catalyst for hydrogenation of m-dinitrobenzene to m-phenylenediamine

Bimetallic Ni-Pt catalysts supported on carbon were found to give very high turn over frequency numbers and almost complete selectivity to m-phenylenediamine in m-dinitrobenzene hydrogenation as compared to the monometallic nickel catalysts. The XRD and XPS characterization revealed that most of the nickel remains as Ni<SUP>2+</SUP> in a monometallic catalyst while, the addition of platinum leads to the stabilization of Ni<SUP>0</SUP> state, in case of bimetallic catalysts

Influence of alkali metal doping on selectivity behaviour of platinum catalysts for hydrogenation of 2-butyne-1,4-diol

Hydrogenation of 2-butyne-1,4-diol to 2-butene-1,4-diol (B<SUB>2</SUB>D) and butane-1,4-diol (B<SUB>1</SUB>D) using Pt catalysts doped with alkali metals was studied. These catalysts showed higher selectivity to the olefinic diol (B<SUB>2</SUB>D) compared to that with monometallic platinum catalyst. Among various alkali metals, Cs-doped catalyst showed highest selectivity (&gt;99%) to B<SUB>2</SUB>D. The selectivity to B<SUB>2</SUB>D increased (up to 99.9%) with increase in the concentration of Cs from 0.25% to 1%. The increase in the basic strength of alkali doped catalysts measured by CO<SUB>2</SUB>-TPD, would be responsible for the increase in electron density of Pt hence, faster desorption and higher selectivity to the intermediate olefinic diol (B<SUB>2</SUB>D). The reaction parameters, such as temperature, H<SUB>2</SUB> pressure and substrate concentration have strong influence on the catalyst activity but almost no effect on the selectivity to B<SUB>2</SUB>D

Shape-controlled preparation and catalytic activity of metal nanoparticles for hydrogenation of 2-butyne-1,4-diol and styrene oxide

Stable nanocluster catalysts prepared by chemical and γ-radiolytic reduction methods were found to give very high turn-over frequency numbers in hydrogenation of styrene oxide and 2-butyne-1,4-diol (BD) as compared to the conventional catalysts. A systematic study was carried out on the effects of different transition metals, their reduction methods, types of polymer used as a capping agent, and the concentration and composition of solvent used during catalyst preparation on the size and shape of nanoparticles. The reduction method of metal precursor directly influenced the morphology of the nanoparticles, affecting the catalyst activity considerably. The cubic-shaped nanoparticles (5-7 nm) were obtained in chemical reduction, while radiolytic reduction method gave spherical nanoparticles (1-7 nm)

Platinum catalyzed hydrogenation of 2-butyne-1,4-diol

Hydrogenation of 2-butyne-1,4-diol (B3D) using 1% Pt/CaCO3 catalyst was carried out to give 2-butene-1,4-diol (B2D) or butane-1,4-diol (B1D) selectively or a mixture of two diols eliminating the formation of acetal, aldehyde, and alcohols as side products. In presence of ammonia, nearly complete selectivity to B2D was obtained in a batch reactor while, in a fixed bed reactor total selectivity to B1D was obtained. Effect of concentration of ammonia, metal loading and catalyst pre-treatment on catalyst activity and selectivity has been investigated in a batch reactor. The formation of B1D and B2D is explained on the basis of associative or dissociative adsorption of B3D via carbene and carbyne type intermediates which react with adsorbed hydrogen to give the corresponding products. A kinetic model based on Langmuir-Hinshelwood (L-H) type mechanism has been proposed which shows a good agreement with experimental data

Selective hydrogenation of 2-butyne-1,4-diol to 2-butene-1,4-diol: roles of ammonia, catalyst pretreatment and kinetic studies

The selective hydrogenation of 2-butyne-1,4 diol to cis-2-butene-1,4 diol has been studied using different palladium-supported catalysts. With 1% Pd/C catalyst, the major product formed was 1,4-butanediol, along with other side products such as butenediol, &#947; -hydroxy butyraldehyde, n-butyraldehyde and n-butanol. Role of supports and ammonia was very significant in achieving a high selectivity to the intermediate, 2-butene-1,4-diol. A selective hydrogenation of 2-butyne-1,4-diol to give cis-2-butene-1,4-diol was achieved using 1% Pd/CaCO3-NH3 catalyst system. Effects of catalyst pretreatment with both 2-butyne-1,4-diol and H2 on the catalyst activity and selectivity were investigated. It was found that the catalyst activity increased substantially, while the selectivity to 2-butene-1,4-diol decreased slightly with hydrogen-pretreated catalyst. The effects of hydrogen pressure, catalyst loading, initial concentrations of 2-butyne-1,4-diol and ammonia on the initial rate of hydrogenation were also studied in a batch reactor in a temperature range of 323-353 K. All the data obtained were in the kinetic regime under the conditions of the present work, based on which a Langmuir-Hinshelwood (L-H) type rate model was proposed. To verify the applicability of the kinetic model over a wide range of conditions, a batch reactor model was also developed. The agreement between the predicted concentration vs. time profiles with the experimental results was excellent