AN ECO-FRIENDLY ONE-POT SYNTHESIS OF 4,4'-(ARYLMETHYLENE)BIS(1H-PYRAZOL-5-OLS) USING [Et3NH][HSO4] AS A RECYCLABLE CATALYST

Abstract

A simple and efficient procedure for synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) by one-pot three-component condensation of aromatic aldehydes, ethyl acetoacetate, and phenylhydrazine/hydrazine hydrate under solvent-free conditions in the presence of [Et 3 NH][HSO 4 ] as catalyst is described. The present protocol offers several advantages such as using a reusable and cost-effective ionic liquid, high yields, simple procedure, easy work-up and eco-friendly reaction conditions.

Pyrazolone-type compounds: synthesis andin silicoassessment of antiviral potential against key viral proteins of SARS-CoV-2

“…Generally, the literature on these particular types of compounds is relatively scarce, and the research is mainly focused on the development of novel eco-friendly synthetic methods employing various catalysts, mostly ionic liquids and nanoparticles. [45][46][47][48][49][50][51][52] Following such a trend, the synthesis of pyrazolone analogues a-t was accomplished in the reactions of 5-methyl-2,4-dihydro-3H-pyrazol-3-one with different aromatic aldehydes in the presence of diethanolamine as a catalyst, and in ethanol and under reux. To optimise reaction conditions, the model reaction between benzaldehyde and 5-methyl-2,4-dihydro-3Hpyrazol-3-one was investigated in the presence of various catalysts and solvents (Table 1).…”

Brønsted Acidic Dicationic Ionic Liquid Immobilized on Fe3O4@SiO2 Nanoparticles as an Efficient and Magnetically Separable Catalyst for the Synthesis of Bispyrazoles

“…and aryl aldehydes (1 eq.) is a certified used way for synthesizing 4,4′‐(arylmethylene) bis(1H‐pyrazol‐5‐ol)s. Therefore, a wide variety of catalysts were developed for this protocol such as [Et 3 NH][HSO 4 ], Fe 3 O 4 based on vanadic acid, ceric ammonium nitrate, Sulfonated Honeycomb Coral, PEG‐SO 3 H, silica‐bonded S‐sulfonic acid . Though these protocols are quite satisfactory in many instances, most of them are associated with limitations such as long reaction times, harsh reaction conditions, application of toxic organic solvents as reaction media, as well as non‐recoverability of the catalyst.…”

Greener and practical synthesis of 4,4′‐(arylmethylene)bis(3‐methyl‐1‐phenyl‐1H‐pyrazol‐5‐ol)s through a conventional heating and a mechanochemical procedure

“…The catalyst‐free preparation of 4,4′‐(arylmethylene)bis(1 H ‐pyrazol‐5‐ol)s has been reported through pseudo‐three component condensation of aldehydes and 3‐methyl‐1‐phenyl‐2‐pyrazolin‐5‐one 11–13 . Although the synthesis of these valuable heterocycles has also been reported using various catalysts and methods through pseudo‐five‐component reaction, 5,14–19 numerous reported methods were not employed owing to their limitations/drawbacks in practical processes.…”