CeCl3-promoted one-pot synthesis of multisubstituted bispyrano[2,3-c]pyrazole derivatives

One-pot Synthesis of Pyrano[2,3-c]pyrazole Derivatives via Multicomponent Reactions (MCRs) and their Applications in Medicinal Chemistry

Background:

Many pyrano[2,3-c]pyrazole derivatives display diverse biological activities and some of them are known as anticancer, analgesic, anticonvulsant, antimicrobial, anti-inflammatory, and anti-malarial agents. In recent years, easy convergent, multicomponent reactions (MCRs) have been adopted to make highly functionalizedpyrano[2,3-c]pyrazole derivatives of biological interest. The synthesis of 1,4-dihydropyrano[2,3-c]pyrazole (1,4-DHPP, 2), 2,4-dihydropyrano[2,3-c]pyrazole (2,4-DHPP, 3), 4-hydroxypyrano[2,3-c]pyrazole (4-HPP, 4) derivatives, 1,4,4-substitied pyranopyrazole (SPP, 5) were reported via two-, three-, four- and five-component reactions (MCRs).

Methods:

This review article compiles the preparation of pyrano[2,3-c]pyrazole derivatives, and it highlights the applications of various pyrano[2,3-c]pyrazole derivatives in medicinal chemistry.

Results:

Varieties of pyrano[2,3-c]pyrazole derivatives were achieved via “One-pot” multicomponent reactions (MCRs). Different reaction conditions in the presence of a catalyst or without catalysts were adapted to prepare the pyrano[2,3-c]pyrazole derivatives.

Conclusion:

Biologically active pyrano[2,3-c]pyrazole derivatives were prepared and used in drug discovery research.

Copper(II) Anchored on Amine-Functionalized MMT: A Highly Efficient Catalytic System for the One-Pot Synthesis of Bispyrano[2,3-c]pyrazole Derivatives

In this study, preparation of pyridine-2-carboimine copper complex immobilized on amine-functionalized nanoclay montmorillonite K10 was reported. The products were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TGA). The catalytic activity of this new nanocatalyst, as a natural, renewable, inexpensive, and heterogeneous catalyst, was very effective for the four-component condensation reaction of hydrazine hydrate (or phenyl hydrazine), malononitrile, β-ketoester, and terephthalaldehyde (or isophthalaldehyde) toward the synthesis of multisubstituted bispyrano[2,3-c]pyrazole derivatives. From the viewpoint of green chemistry, the advantages of this approach are accessibility, simplicity, and high yields synthesis. The catalyst was recycled and reused four times without significant loss of activity.

[DMImd-DMP]: A highly efficient and reusable catalyst for the synthesis of 4H-benzo[b]pyran derivatives

A series of substituted 4H-pyrans derivatives were synthesized by a one-pot, multi-component reaction of aromatic aldehydes, malononitrile, and pyrazolone derivatives or active methylene carbonyl compounds such as dimedone, in the presence of 1,3-dimethyl imidazolium dimethyl phosphate [DMImd-DMP] as a catalyst in aqueous ethanol. Recyclability of the catalyst, high yields, simple product isolation and high atom economy are the noteworthy aspects of this protocol.

Bispyranopyrazoles as Green Corrosion Inhibitors for Mild Steel in Hydrochloric Acid: Experimental and Theoretical Approach

In the present study, we have synthesized two novel corrosion inhibitors BP-1 and BP-2 and evaluated their corrosion inhibition property on mild steel (MS) in acid solution through weight loss and electrochemical corrosion techniques. The corrosion test results reveal that both compounds inhibit corrosion by an adsorption mechanism and display inhibition efficiency more than 95% at a low concentration of 1.72 × 10^-4 M. From the surface analysis of the protective film on MS, it was corroborated that adsorption of inhibitor molecules occurred on the MS surface through chemisorption, which further suppresses the corrosion rate. Density functional theory simulated data helps correlate the experimental trend with the theoretical study.

Synthesis of functionalized dihydro-2-oxopyrroles using graphene oxide as heterogeneous catalyst

A mild, efficient synthetic approach for the synthesis of highly functionalized dihydro-2-oxopyrroles is developed by using graphene oxide, a readily available and inexpensive material, as an eco-benign solid acid catalyst in ethanol at room temperature. The present methodology displays several advantages such as practical simplicity, high atom economy, easy workup procedure, and high yields of the products.

Ultrasound promoted facile one pot synthesis of highly substituted pyran derivatives catalyzed by silica-coated magnetic NiFe2O4nanoparticle-supported H14[NaP5W30O110] under mild conditions

Application of ultrasonic method as a green source of energy to reduce the reaction times compared to conventional processes. NiFe₂O₄@SiO₂–H₁₄[NaP₅W₃₀O₁₁₀] was used as magnetically separable catalyst for synthesis of pyrans with minimum work up.

Green synthesis of tetrahydrobenzo[b]pyrans, pyrano[2,3-c]pyrazoles and spiro[indoline-3,4′-pyrano[2,3-c]pyrazoles catalyzed by nano-structured diphosphate in water

Preparation of nanostructured diphosphate Na₂CaP₂O₇. Avoiding of any acid catalysts. The prepared catalyst is reusable and eco-friendly. The method is easy and contains simple experimental procedure.