Well-Dispersed Trifluoromethanesulfonic Acid-Treated Metal Oxide Nanoparticles Immobilized on Nitrogen-Doped Carbon as Catalysts for Friedel-Crafts Acylation

Introducing a protic ionic liquid from aminoethyl piperazine and triflic acid immobilized on pectin as a reusable nanocatalyst for the selective Schmidt synthesis of nitriles

Preparation of reusable protic ionic liquid, triflic acid-immobilized aminoethyl piperazine-modified pectin (Pec-AEP-TfOH), with excellent activity and selectivity in modified Schmidt synthesis of nitriles from aldehydes and Si(CH3)3N3 has been described. The structure of the catalyst was characterized using FT-IR, XRD, FE-SEM, EDX-mapping, and TGA-DTA. The reaction demonstrated a broad substrate scope for a variety of benzaldehyde derivatives with electron withdrawing/donating substituents and heterocyclic aldehydes with yields between 85 and 96 % at room temperature. Also, the Pec-AEP-TfOH showed an excellent selectivity for the nitriles in which no formanilide was obtained. Furthermore, the Pec-AEP-TfOH revealed a remarkable chemoselectivity for aldehydes in the presence of acids or ketones. It is worth noting that TfOH as a precious superacid was immobilized for the first time in the selective Schmidt synthesis of nitriles to improve the eco-friendliness and economic efficiency of the process. Furthermore, the catalyst was cost-effective, metal-free, safe, scalable, and reusable (5 times) and its heterogeneity was confirmed by hot-filtration test.

Mechanism of Friedel-Crafts Acylation Using Metal Triflate in Deep Eutectic Solvents: An Experimental and Computational Study

In this paper, we develop a method for Friedel-Crafts acylation using metal triflate in deep eutectic solvents. Various metal triflates were tested and provided good to excellent yields of corresponding ketone products. The density functional theory calculation revealed the metal effects on the formation of active intermediate acylium triflate as well as the acidic condition. The metal triflate in the deep eutectic solvent can be recovered and reused with a little loss in the catalytic activity.

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.

Development of Trifluoromethanesulfonic Acid-Immobilized Nitrogen-Doped Carbon-Incarcerated Niobia Nanoparticle Catalysts for Friedel-Crafts Acylation

Heterogeneous trifluoromethanesulfonic acid-immobilized nitrogen-doped carbon-incarcerated niobia nanoparticle catalysts (NCI-Nb-TfOH) that show excellent catalytic performance with low niobium loading (1 mol %) in Friedel-Crafts acylation have been developed. These catalysts exhibit higher activity and higher tolerance to catalytic poisons compared with the previously reported TfOH-treated NCI-Ti catalysts, leading to a broader substrate scope. The catalysts were characterized via spectroscopic and microscopic studies.