Magnetic nanoparticles functionalized ethane sulfonic acid (MNESA): as an efficient catalyst in the synthesis of coumarin derivatives using Pechmann condensation under mild condition

Carbon nanofiber/taurine-catalyzed synthesis of coumarin and 1,2,4,5-tetra-substituted imidazole derivatives under metal-free conditions

The main subject of this research is the development of a suitable, efficient, and biocompatible carbon nanofiber-based catalytic system for the synthesis of coumarin and 1,2,4,5-tetra-substituted imidazoles. Brønsted acid carbon nanofiber/taurine catalyst was made during three steps: acid treatment, acylation, and then amination. The basic principles and general advantages of the synthesis method are elaborated. The acidity of the prepared nano-catalyst was investigated using the Hammet acidity technique and UV-Vis spectroscopy, and the H0 value for 5 × 10-2 mg/mL of CNF/T in 0.3 mM 4-nitroaniline solution was determined to be 1.47. The structure of the catalyst was successfully characterized using FT-IR, TGA, FESEM, XRD, TEM, EDX, EDS-MAP, BET, and XPS techniques. Here, we report the ability of carbon nanofiber/taurine as a Brønsted acid catalyst for the synthesis of coumarins and 1,2,4,5-tetra-substituted imidazole through a metal-free, cost-effective, and biocompatible multicomponent route. Among the advantages of this protocol are reaction time, excellent efficiency, reusability, and high activity of the catalyst.

A review on convenient synthesis of substituted coumarins using reuseable solid acid catalysts

Due to growing concern about chemicals and their impact on the environment, cleaner reaction conditions are needed to be incorporated into chemical synthetic procedures. Recently, the use of heteropolyacid catalysts, mainly reuseable solid acid catalysts, has gained a leading role in organic synthesis due to their environmental and economic considerations and industrial utilization. The high catalytic activity, moisture sensitivity, reusability and inexpensive makes solid supported reagents attractive substituents to conventional Lewis acids. Nowadays synthesis of coumarins and their derivatives has attracted considerable attention from organic and medicinal chemists for many years as a large number of natural products contain this heterocyclic nucleus. In continuation with our investigations into the synthesis of substituted coumarins and due to several advantages of heterogeneous catalysts viz. cost-effective, no side products, high yield of desired products and no toxic waste material, here we report a new approach for the synthesis of substituted coumarins using solid acid catalysts.

Fe3O4@C@OSO3H as an efficient, recyclable magnetic nanocatalyst in Pechmann condensation: green synthesis, characterization, and theoretical study

Novel sulfonated carbon-coated magnetic nanoparticles (SCCMNPs; Fe₃O₄@C@OSO₃H) were designed, synthesized, characterized, and applied as an efficient nanocatalyst for green synthesis of coumarin derivatives through Pechmann condensation. The Fe₃O₄@C@OSO₃H was manufactured through a simple and inexpensive two-step procedure and characterized by FTIR, EDX, XRD, SEM, TEM, DLS, VSM, and TGA techniques. It was identified as an efficient heterogeneous catalyst in the Pechmann condensation of phenol derivatives and β-ketoesters, leading to high-yield coumarin derivatives under solvent-free conditions. The Fe₃O₄@C@OSO₃H removed after reaction finishing point by an external magnet, and it was reused fifteen times at the same conditions. Besides, theoretical studies were carried out using B3LYP/6-311++G(d,p) to more consideration of the reaction mechanism. The study of the frontier molecular orbitals, NBO atomic charges, molecular electrostatic potential of reactants, as well as Pechmann condensation mechanism was known very useful in suitable reactant choice. The reaction was performed through the electrophilic attack, dehydration, and trans-esterification, respectively.