Synthesis of Pyrano [2,3-c] Pyrazole Derivatives Using a Novel Ionic-Liquid Based Nano-Magnetic Catalyst (Fe3O4@SiO2@(CH2)3NH@CC@Imidazole@SO3H+Cl−)

Review on advancements of pyranopyrazole: synthetic routes and their medicinal applications

Pyranopyrazoles are among the most distinguished, biologically potent, and exciting scaffolds in medicinal chemistry and drug discovery. Synthesis and design of pyranopyrazoles using functional modifications via multicomponent reactions (MCRs) are thoroughly found in synthetic protocols by forming new C-C, C-N, and C-O bonds. This review aims to focus on the biological importance of pyranopyrazoles as well as on a diverse synthetic approach for their synthesis using various catalytic systems such as acid-catalyzed, base-catalyzed, ionic liquids and green media-catalyzed, nano-particle-catalyzed, metal oxide-supported catalysts, and silica-supported catalysts. In this review, we have summarized data on the advancements in synthesizing pyranopyrazole from the last two decades to the mid-2023 and research papers describing the importance of these scaffolds. This review will be significant for synthetic organic chemists and researchers working in organic chemistry.

A green protocol ball milling synthesis of dihydropyrano[2,3-c]pyrazole using nano-silica/aminoethylpiperazine as a metal-free catalyst

BACKGROUND

Ball mill is an effective, and green method for the synthesis of heterocyclic compounds in very good yields. This method is a simple, economical, and environmentally friendly process. In this work, an efficient approach for the synthesis of pyranopyrazoles (PPzs) using ball milling and metal-free nano-catalyst (Nano-silica/aminoethylpiperazine), under solvent-free conditions was reported.

RESULTS

The new nano-catalyst silica/aminoethylpiperazine was prepared by immobilization of 1-(2-aminoethyl)piperazine on nano-silica chloride. The structure of the prepared nano-catalyst was identified by FT-IR, FESEM, TGA, EDX, EDS-map, XRD, and pH techniques. This novel nano-catalyst was used for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives under ball milling and solvent-free conditions.

CONCLUSIONS

Unlike other pyranopyrazoles synthesis reactions, this method has advantages including short reaction time (5-20 min), room temperature, and relatively high efficiency, which makes this protocol very attractive for the synthesis of pyranopyrazoles derivatives.

Chlorosulfonic acid coated on porous organic polymer as a bifunctional catalyst for the one-pot three-component synthesis of 1,8-naphthyridines

The synthesis of six-membered oxygen- and nitrogen-containing heterocycles has been regarded as the most fundamental issue in organic chemistry and the chemical industry because these heterocycles are used in producing high-value products. In this study, an efficient, economic, sustainable, and green protocol for their multicomponent synthesis has been developed. The one-pot direct Knoevenagel condensation-Michael addition-cyclization sequences for the transformation of aromatic aldehydes, malononitrile, and 2-aminopyridine generate the corresponding 1,8-naphthyridines over a novel mesoporous bifunctional organocatalyst supported cholorosulfonic acid [poly(triazine-benzene sulfonamide)-SO3H (PTBSA-SO3H)] under ambient conditions. The catalyst was used for the formation of 1,8-naphthyridine derivatives for six runs. The current strategy provided a wider substrate range, and short reaction times.