Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

In this review, we comprehensively describe catalyzed multicomponent reactions (MCRs) and the multiple roles of catalysis combined with key parameters to perform these transformations. Besides improving yields and shortening reaction times, catalysis is vital to achieving greener protocols and to furthering the MCR field of research. Considering that MCRs typically have two or more possible reaction pathways to explain the transformation, catalysis is essential for selecting a reaction route and avoiding byproduct formation. Key parameters, such as temperature, catalyst amounts and reagent quantities, were analyzed. Solvent effects, which are likely the most neglected topic in MCRs, as well as their combined roles with catalysis, are critically discussed. Stereocontrolled MCRs, rarely observed without the presence of a catalytic system, are also presented and discussed in this review. Perspectives on the use of catalytic systems for improved and greener MCRs are finally presented.

Ultrasound-Assisted, ZnCr2O4 Nanocatalyzed Synthesis of Substituted Tetrahydroquinolines via Povarov Reaction

Eco-friendly, reusable ZnCr2O4 Nano catalyzed tetrahydroquinoline derivatives are prepared via Povarov reaction route from aromatic aldehydes, α-amino naphthalene, and 2,3-dihydrofuran under reflux/ultrasonic irradiation methods. This several affords several benefits like good to excellent yields, a higher percentage of atom economy. Substituted tetrahydroquinolines have been shown great biological potential.

Microstructural Design of Ba0.5La0.5Co0.5Fe0.5O3 Perovskite Ceramics

Ba0.5La0.5Co0.5Fe0.5O3−δ was synthesized in the solid-state reaction route. The influence of ball milling parameters (such as milling media size, angular velocity, and time), pelletizing pressure, and annealing parameters on the microstructure was studied. The grain size distribution and density or specific surface area changes were investigated in each approach while the individual parameters were changed. The evaluation of BLCF synthesis parameters enables tailoring the microstructure to various applications. It was observed that with lowering the size of milling balls and increasing the angular velocity the material will be porous and thus more appropriate as electrode material in proton ceramic fuel cell or electrolyzer. An increase of time, balls diameter, and/or angular velocity of milling enables one to densify the material in case of membrane application in, e.g., as a gas sensor. The significant influence on densification has also annealing temperature increase. Applying 1200 °C during annealing leads to dense material, while at 1100 °C shows visible porosity of the product. In this work, we present the results of the BLCF synthesis parameters change allowing the selection of appropriate parameter values depending on the further application as PCCs.

Synthesis and characterization of manganese ferrite from low grade manganese ore through solid state reaction route

Manganese ferrite spinel has been synthesized by using low grade manganese ore and ferric oxide as sources of manganese oxide and iron oxide through solid state reaction route by taking manganese and iron mole ratio of 1:2 respectively. The impact of sintering temperature on phase composition and particle size is investigated. Similarly, the impact of frequency on dielectric constant, dielectric loss, AC (alternating current) conductivity and tangent losses is also investigated. The results shows the presence of spinel structure manganese ferrite (MnFe2O4) as the major phase for the sample sintered at 1200 °C. It has been established that the crystallite size increase with rise in sintering temperature. The surface morphology of the sample sintered at 1200 °C show pyramidal and triangular shape grains. The dielectric constant (εʹ) and dielectric losses (εʹʹ) were observed to decrease with increasing the sintering temperature and frequency. Furthermore, the AC (alternating current) conductivity was found to rise with rise in applied frequency. On the other hand, the tangent losses falls considerably with rise in applied frequency.

Evidence of Finite Magneto-electric Coupling in SmFeO3 – PbTiO3 Solid Solutions

Present work investigates the detailed multiferroic properties of Pb1 − xSmxTi1−xFexO3, (x = 0.21, 0.22, 0.23, 0.24 and 0.25) synthesize through solid state reaction route. The structural, dielectric, ferroelectric and magnetic properties were measured. A sincere study is carried out to detect the magneto-electric coupling in all the samples through magneto-dielectric, magnetization after electric poling and magneto-pe response. The maximum value of coupling coefficient (γ) and magneto-dielectric response (MDR) of sample x = 0.24 has shown by magneto-dielectric properties and magnetization after electric poling whereas magneto-pe has shown that all the samples possess multiferroic nature.