Core-shell assembly of ZrO2 nanoparticles with ionic liquid: a novel and highly efficient heterogeneous catalysts for Biginelli and esterification reactions

Imidazolium sulfonic acid chloride grafted ZrO₂ nanoparticles (ZrO₂-IL) were synthesized through facile post-treatment of the nanoparticles with the imidazolium-sulfonic acid chloride ionic liquid. The immobilization of the ionic liquid over the ZrO₂ nanoparticles was evident from the XRD, SEM, TEM, Raman, BET, and XPS analysis. The results obtained from the XRD analysis clearly show that the catalyst has an orthorhombic structure and from the BET analysis it is evident that the surface is mesoporous with uniform pore sizes and pore distribution. Further evidence of immobilization of ionic liquid over the ZrO₂ NPs was obtained from the SEM, TEM, XPS, and Raman analysis. Under mild conditions, the synthesized heterostructure was used in the acid-catalyzed esterification of different acids. The ZrO₂-IL catalyst converts 99% of the acid to ester with a 98.9% yield in 1h. The material was also shown to be highly efficient as catalyst for the Biginelli reaction under solvent-free conditions, with the catalyst for dihydropyrimidin-2(1H)-one (DHPMs) in 1h with 99.2% conversion and 99% yield. The synergy between the ionic liquid catalyst and the substrates increased the catalytic efficiency and resulted in high-yield product conversion. The mechanism of both transformation reactions was investigated, as well as the synergy between ionic liquid and ZrO₂ nanoparticles for better catalytic efficiency was established.

Biginelli Reaction: Polymer Supported Catalytic Approaches

The Biginelli product, dihydropyrimidinone (DHPM) core, and its derivatives are of immense biological importance. There are several methods reported as modifications to the original Biginelli reaction. Among them, many involve the use of different catalysts. Also, among the advancements that have been made to the Biginelli reaction, improvements in product yields, less hazardous reaction conditions, and simplified isolation of products from the reaction predominate. Recently, solid-phase synthetic protocols have attracted the research community for improved yields, simplified product purification, recyclability of the solid support, which forms a special economic approach for Biginelli reaction. The present Review highlights the role of polymer-supported catalysts in Biginelli reaction, which may involve organic, inorganic, or hybrid polymers as support for catalysts. A few of the schemes involve magnetically recoverable catalysts where work up provides green approach relative to traditional methods. Some research groups used polymer-catalyst nanocomposites and polymer-supported ionic liquids as catalyst. Solvent-free, an ultrasound or microwave-assisted Biginelli reactions with polymer-supported catalysts are also reported.

FeCl₃∙6H₂O/TMSBr-Catalyzed Rapid Synthesis of Dihydropyrimidinones and Dihydropyrimidinethiones under Microwave Irradiation

An efficient and practical protocol has been developed to synthesize dihydropyrimidinones and dihydropyrimidinethiones through FeCl₃∙6H₂O/TMSBr-catalyzed three-component cyclocondensation under microwave irradiation. This approach features high yields, broad substrate scope, short reaction time, mild reaction conditions, operational simplicity and easy work-up, thus affording a versatile method for the synthesis of dihydropyrimidinones and dihydropyrimidinethiones.

Carbon nanotube-based stimuli-responsive nanocarriers for drug delivery

In cancer therapy, smart nanocarriers are one of the most important nanoscale vectors of therapeutic agents.

The Biginelli reaction under batch and continuous flow conditions: catalysis, mechanism and antitumoral activity

Biginelli scaffolds have been synthesized using two new coordination polymer as catalysts under batch or continuous flow conditions. The mechanism of the reaction and the antitumoral activity of the obtained DHPMs were also evaluated.

Catalytic performance of bismuth pyromanganate nanocatalyst for Biginelli reactions

Bi₂Mn₂O₇ nano-powders were synthesized via a stoichiometric 1 : 1 Bi : Mn molar ratio hydrothermal method at 180 °C for 48 h in a 1 M NaOH aqueous solution.

Solid state synthesis, characterization, optical properties and cooperative catalytic performance of bismuth vanadate nanocatalyst for Biginelli reactions

Bi₂V₂O₇ nano powders were synthesized via a solid state reaction at 500 °C for 8 h using Bi(NO₃)₃ and VO(acac)₂ at stoichiometric 1 : 1 Bi : V molar ratio as raw materials.

High performance Pd catalyst using silica modified titanate nanotubes (STNT) as support and its catalysis toward hydrogenation of cinnamaldehyde at ambient temperature

A Pd/STNT catalyst, with silica modified titanate nanotubes as support, exhibited significantly enhanced activity towards hydrogenation of cinnamaldehyde.