Synthesis of pyranopyrazoles using magnetic Fe3O4 nanoparticles as efficient and reusable catalyst

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.

Green multicomponent synthesis of pyrano[2,3-c]pyrazole derivatives: current insights and future directions

The past decade has witnessed significant progress in synthesizing structurally diverse and biologically relevant pyrano[2,3-c]pyrazole derivatives through the integration of green methodologies. This review summarizes the recent advances in the green multicomponent synthesis of pyrano[2,3-c]pyrazole and spiro-pyrano[2,3-c]pyrazole derivatives. These include the application of energy-efficient techniques such as microwave and ultrasound-assisted synthesis, benign catalysts and biodegradable composites, solvent selection with a focus on water as a renewable and non-toxic medium, and solvent-free conditions. The review consolidates the current knowledge and future research directions, providing a valuable resource for researchers dedicated to advancing green chemistry practices.

Water-SDS-[BMIm]Br composite system for one-pot multicomponent synthesis of pyrano[2,3-c]pyrazole derivatives and their structural assessment by NMR, X-ray, and DFT studies

Here, we report a simple, efficient, and green protocol for the one-pot synthesis of pyrano[2,3-c]pyrazole derivatives via a sequential three-component strategy using aromatic aldehydes, malononitrile and pyrazolin-5-one in a water-SDS-ionic liquid system. This is a base and volatile organic solvent-free approach that could be applicable to a wide substrate scope. The key advantages of the method over other established protocols are very high yield, eco-friendly conditions, chromatography-free purification and recyclability of the reaction medium. Our study revealed that the N-substituent present in pyrazolinone controls the selectivity of the process. N-unsubstituted pyrazolinone favours the formation of 2,4-dihydro pyrano[2,3-c]pyrazoles whereas under identical conditions N-phenyl substituent pyrazolinone favours the formation 1,4-dihydro pyrano[2,3-c]pyrazoles. Structures of the synthesized products were established by NMR and X-ray diffraction techniques. Energy optimized structures and energy gaps between the HOMO-LUMO of some selected compounds were estimated using density functional theory to explain the extra stability of the 2,4-dihydro pyrano[2,3-c]pyrazoles over 1,4-dihydro pyrano[2,3-c]pyrazoles.

Synthesis of steroidal dihydropyrazole derivatives using green ZnO NPs and evaluation of their anticancer and antioxidant activity

Zinc oxide nanoparticles (ZnO NPs) were synthesized by a green method using Azadirachta indica leaf extract. The structure of the prepared ZnO (NPs) were characterized by FT-IR, XRD, SEM-EDX and TEM analyses. The biosynthesized ZnO (NPs) were then used as a catalyst for the synthesis of steroidal dihydropyrazole derivatives through a one-pot multicomponent reaction involving phenyl acetylene and hydrazine derivatives. The anticancer activity of newly synthesized compounds were evaluated against three cancer cell lines namely HeLa (human cervical carcinoma), Hep3B (human hepatocellular carcinoma) and MCF7 (human breast adenocarcinoma) by MTT assay. The tested compounds were found to be active against all cancer cell lines and less toxic towards normal peripheral blood mononuclear cells (PBMCs). Antioxidant activity have also been investigated via free radical scavenging ability using DPPH, FRAP and ABTS assay. The tested compounds were found to exhibit moderate to good antioxidant activity which increases with increase in the concentration of steroidal dihydropyrazoles. Among all the tested steroidal dihydropyrazoles, compound 17 is found to be most active.

Magnetically Recoverable Silica-Decorated Ferromagnetic-Nanoceria Nanocatalysts and Their Use with O- and N-Butyloxycarbonylation Reaction via Solvent-Free Condition

Silica-decorated ferrite nanoparticles, a new kind, coated with ceric ammonium nitrate (CAN), have been prepared successfully by simple coprecipitation techniques. Powder X-ray diffraction spectroscopy (PXRD), Fourier transform-infrared spectroscopy (FT-IR), field emission-scanning electron microscope (FE-SEM), wavelength-dispersive X-ray spectroscopy (WDX), energy-dispersive spectroscopy (EDS), inductive coupled plasma-optical emission spectroscopy (ICP-OES), and thermogravimetric analysis (TGA) techniques were used to characterize these nanoparticles. The catalysts are further studied for catalytic activity in solvent-free conditions. Importantly, these nanoparticles have been collected from the reaction mixture using an external magnet and recycled up to minimum of 15 cycles with no substantial loss of catalytic characteristics.

Design, Green Synthesis and Tailoring of Vitamin E TPGS Augmented Niosomal Nano-Carrier of Pyrazolopyrimidines as Potential Anti-Liver and Breast Cancer Agents with Accentuated Oral Bioavailability

VEGF plays a crucial role in cancer development, angiogenesis and progression, principally liver and breast cancer. It is vital to uncover novel chemical candidates of VEGFR inhibitors to develop more potent anti-breast and anti-liver cancer agents than the currently available candidates, sorafenib and regorafenib, that face resistance obstacles and severe side effects. Herein, nine pyrazolopyrimidine derivatives were designed, synthesized as sorafenib and regorafenib analogues and screened for their in vitro cytotoxic and growth inhibition activities against four human cancer cell lines, namely breast cancer (Michigan Cancer Foundation-7 (MCF-7), hepatocellular carcinoma (HCC) type (HepG2), lung carcinoma (A-549) and human colorectal carcinoma-116 (HCT-116)). Among the tested compounds, compounds 1, 2a, 4b and 7 showed the uppermost cytotoxic activities against all aforementioned cell lines with IC₅₀ estimates varying from 6 to 50 µM, among which compound 7 showed the best inhibitory activity on all tested compounds. Stunningly, compound 7 showed the best significant inhibition of the VEGFR-2 protein expression level (72.3%) as compared to the control and even higher than that produced with sorafenib and regorafenib (70.4% and 55.6%, respectively). Modeling studies provided evidence for the possible interactions of the synthesized compounds with the key residues of the ATP binding sites on the hinge region and the “DFG out” motif of VEGFR-2 kinase. Collectively, our present study suggests that pyrazolopyrimidine derivatives are a novel class of anti-cancer drug candidates to inhibit VEGF-VEGFR function. Aspiring to promote constrained aqueous solubility, hence poor oral bioavailability of the developed lead molecule, 7 and 2a-charged D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) surface-coated niosomes were successfully constructed, adopting a thin film hydration technique striving to overcome these pitfalls. A 2³ full factorial design was involved in order to investigate the influence of formulation variables: type of surfactant, either Span 60 or Span 40; surfactant:cholesterol ratio (8:2 or 5:5) along with the amount of TPGS (25 mg or 50 mg) on the characteristics of the nanosystem. F2 and S2 were picked as the optimum formula for compounds 2a and 7 with desirability values of 0.907 and 0.903, respectively. In addition, a distinguished improvement was observed in the compound’s oral bioavailability and cytotoxic activity after being included in the nano-TPGS-coated niosomal system relative to the unformulated compound. The nano-TPGS-coated niosomal system increased the hepatocellular inhibitory activity four times fold of compound 7a (1.6 µM) and two-fold of 2a (3 µM) relative to the unformulated compounds (6 µM and 6.2 µM, respectively).

Synthesis and Toxicological Effect of Some New Pyrrole Derivatives as Prospective Insecticidal Agents against the Cotton Leafworm, Spodoptera littoralis (Boisduval)

Herein, a series of biologically active pyrrole derivatives, namely 2-[(3-cyano-5-aryl-1H-pyrrol-2-yl)thio]acetic acids 2a-c, 2-[(2-hydroxyethyl)-thio]-5-aryl-1H-pyrrole-3-carbonitriles 3a-c, and 2-[(2-amino-ethyl)thio]-5-aryl-1H-pyrrole-3-carbonitriles 4a-c, 2,2'-disulfanediylbis(5-aryl-1H-pyrrole-3-carbonitriles) 5a-c, 2-((3-cyano-5-aryl-1H-pyrrol-2-yl)thio)acetates 6a-c, 2-[(3-cyano-5-phenyl-1H-pyrrol-2-yl)thio]acetohydrazides 7a-c, and 2-{2-[(3-cyano-5-aryl-1H-pyrrol-2-yl)thio]acetyl}-N-phenyl-hydrazinecarbothioamides 8a-c, as insecticidal agents, were synthesized via adaptable, smoothly accessible 2-(2-oxo-2-arylylethyl)malononitriles 1a-c. The structures were proved using infrared (IR), nuclear magnetic resonance (NMR), and mass spectrum (MS) techniques. Under laboratory conditions, the toxicological characteristics were tested towards Spodoptera littoralis, cotton leafworm insect type. In respect to the LC₅₀ values, compounds 6a, 7a, 8c, and 3c possess the highest insecticidal bioefficacy, with values of 0.5707, 0.1306, 0.9442, and 5.883 ppm, respectively. The study paves the way towards discovering new materials for potential use as insecticidal active agents.

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.

Overview on magnetically recyclable ferrite nanoparticles: synthesis and their applications in coupling and multicomponent reactions

Nanocatalysis is an emerging area of research that has attracted much attention over the past few years. It provides the advantages of both homogeneous as well as heterogeneous catalysis in terms of activity, selectivity, efficiency and reusability. Magnetically recoverable nanocatalysts provide a larger surface area for the chemical transformations where the organic groups can be anchored and lead to decrease in the reaction time, increase in the reaction output and improve the atom economy of the chemical reactions. Moreover, magnetic nanocatalysts provide a greener approach towards the chemical transformations and are easily recoverable by the aid of an external magnet for their reusability. This review aims to give an insight into the important work done in the field of magnetically recoverable nanocatalysts and their applications in carbon-carbon and carbon-heteroatom bond formation.

Development of New Thiazole Complexes as Powerful Catalysts for Synthesis of Pyrazole-4-Carbonitrile Derivatives under Ultrasonic Irradiation Condition Supported by DFT Studies

In this study, we are interested in preparing Fe(III), Pd(II), and Cu(II) complexes from new thiazole derivatives. All syntheses were elaborately elucidated to estimate their molecular and structural formulae, which agreed with those of mononuclear complexes. The square-planer geometry of Pd(II) complex (MATYPd) was the starting point for its use as a heterocatalyst in preparing pyrazole-4-carbonitrile derivatives 4a-o using ultrasonic irradiation through a facile one-pot reaction. The simple operation, short-time reaction (20 min), and high efficiency (97%) were the special advantages of this protocol. Furthermore, this green synthesis strategy was advanced by examination of the reusability of the catalyst in four consecutive cycles without significant loss of catalytic activity. The new synthesis strategy presented remarkable advantages in terms of safety, simplicity, stability, mild conditions, short reaction time, excellent yields, and use of a H₂O solvent. This catalytic protocol was confirmed by the density functional theory (DFT) study, which reflected the specific characteristics of such a complex. Logical mechanisms have been suggested for the successfully exerted essential physical parameters that confirmed the superiority of the Pd(II) complex in the catalytic role. Optical band gap, electrophilicity, and electronegativity features, which are essential parameters for the catalytic behavior of the Pd(II) complex, are based mainly on the unsaturated valence shell of Pd(II).

Synthesis and Antibacterial Screening of Some Pyrazole Derivatives Catalyzed by Cetyltrimethylammoniumbromide (CTAB)

AIMS

In this article, we have developed an eco-friendly one-pot multi-component reaction methodology employed for the green synthesis of functionalized pyrazole derivatives viz cyclo-condensation of aromatic aldehydes, ethyl acetoacetate and phenyl hydrazine and/or hydrazine hydrate in the presence of cetyltrimethylammoniumbromide (CTAB) at 90°C temperature in an aqueous medium.

MATERIALS AND METHODS

In the present protocol, we developed a green method for the synthesis of functionalized pyrazole derivatives through one-pot, multi-component cyclo-condensation of aromatic aldehydes, phenyl hydrazine or hydrazine hydrate and ethyl acetoacetate using cetyltrimethylammoniumbromide (CTAB) as a catalyst in water as a solvent. Our methodology confers advantages such as short reaction time, atom economy, purification of the product without using column chromatographic and hazardous solvent. The reaction is being catalyzed by cetyltrimethylammoniumbromide (CTAB) and thus, products are formed under the green reaction conditions.

RESULTS AND DISCUSSION

Initially, the reaction of benzaldehyde and phenylhydrazine with ethyl acetoacetate was carried out in water at room temperature in the absence of the catalyst; no product was obtained after 24 h (Table 1 entry 1). When the reaction was carried out using L-proline as a catalyst in ethanol at 70°C, the yield of the product was 20%.

CONCLUSION

This research not only provides a green and efficient method for the synthesis of sulfinic esters but also shows new applications of electrochemistry in organic synthesis. We consider that this green and efficient synthetic protocol used to prepare sulfinic esters will have good applications in the future. In conclusion, we have developed successfully a green and efficient one-pot multi-component methodology for the synthesis of substituted pyrazoles using CTAB as a catalyst in water as a solvent with excellent yields. Purifications of compounds were achieved without the use of traditional chromatographic procedures. This methodology has advantages of operational simplicity, clean reaction profiles and relatively broad scope, which make it more attractive for the diversity oriented synthesis of these heterocyclic libraries. In this methodology, we suggest a further alternative possibility for the formation of substituted pyrazoles. The compound 7h can be used as an anticancer drug in the pharma industry.

L-Cysteine Catalyzed Environmentally Benign One-pot Multicomponent Approach Towards the Synthesis of Dihydropyrano[2,3-c]pyrazole Derivatives

BACKGROUND

The pyrano[2,3-c]pyrazole derivatives are important building blocks of many biologically active compounds owing to their diverse biological potential for example, anti-inflammatory, anticancer, anti-microbial and anti-oxidant properties.

OBJECTIVE

Keeping in mind the wide range of applications of pyrano[2,3-c]pyrazoles, herein we intended to develop a novel synthetic methodology for dihydropyranopyrazoles. We were also interested in determining the influence of amino acids and dipeptides as a catalyst on the synthesis of pyrano[2,3-c]pyrazole derivatives.

METHODS

To achieve our objectives, we used a one-pot multi-component reaction of ethyl 3-oxobutanoate, propanedinitrile, hydrazine monohydrate and several substituted benzaldehydes by using different catalysts and solvents to synthesize our desired products in the presence of various catalysts.

RESULTS AND DISCUSSION

We found that optimal conditions for the preparation of pyrano[2,3-c]pyrazoles were L-cysteine (0.5 mol) in the presence of water:ethanol (9:1) at 90 °C. Various 1,4-dihydropyrano[2,3- c]pyrazoles were afforded by using several substituted benzaldehydes in 66-97% yields.

CONCLUSION

We described a green and environmentally benign method to synthesize pyrano[2,3-c]pyrazoles in a one-pot four component reaction of ethyl 3-oxobutanoate, propanedinitrile, hydrazine monohydrate and different substituted benzaldehyde in the presence of L-cysteine in aqueous ethanol (9:1) at 90 oC. Excellent yields of the products, simple work-up, easily available starting materials, use of green solvents, naturally occurring catalyst, non-toxicity, non-chromatographic purification and environmentally benign reaction conditions are some main advantages of this protocol.

Green Method for the Synthetic Ugi Reaction by Twin Screw Extrusion without a Solvent and Catalyst

This study describes the solvent and catalyst-free Ugi reaction by way of twin screw extrusion (TSE). Multicomponent chemical synthesis can be converted into a single process without repeated use of solvents through TSE. High synthetic yields are achieved in short reaction times and produced in solvent-free conditions, which lead to a more environmentally friendly process.

Cascade annulation reaction (CAR): highly diastereoselective synthesis of pyranopyrazole scaffolds

An unprecedented domino protocol for the novel synthesis of highly diverse and functionalized tetrahydro pyranopyrazole scaffolds using chalcone epoxide has been reported for the first time. This synthetic protocol generates three consecutive stereogenic centres in a highly diastereoselective manner with the formation of vicinal diol and a quaternary carbon centre. A wide range of substrates were utilized for the scope of this methodology and provided very good yields of pyranopyrazoles. The pyranopyrazoles were also transformed into densely functionalized tetrasubstituted olefins.

An unprecedented domino protocol for the novel synthesis of highly diverse and functionalized tetrahydro pyranopyrazole scaffolds using chalcone epoxide has been reported.

Four-component green synthesis of benzochromene derivatives using nano-KF/clinoptilolite as basic catalyst: study of antioxidant activity

An efficient procedure for the synthesis of benzochromene derivatives employing 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone (euparin), aldehydes, alkyl bromides, dialkyl acetylenedicarboxylate and triphenylphosphine in the presence of KF/CP NPs as a heterogeneous base nano-catalyst in water at 80 °C is investigated. Also, the antioxidant activity of some synthesized compounds was studied. The workup of mixture of reaction is simple, and the products can be separated easily by filtration. KF/CP NPs showed a good improvement in the yield of the product and displayed significant reusable activity.

Core–shell structured magnetic silica supported propylamine/molybdate complexes: an efficient and magnetically recoverable nanocatalyst

A novel core–shell structured magnetic silica supported propylamine/molybdate complex (Fe₃O₄@SiO₂/Pr-NMo[Mo₅O₁₈]) is prepared, characterized and applied as an effective and easily recoverable nanocatalyst in the synthesis of pyrano-pyrazole derivatives.

Green synthesis of α-aminophosphonates using ZnO nanoparticles as an efficient catalyst

Synthesis of α-aminophosphonate derivatives via the Kabachnik–Fields reaction is described using 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone, extracted from rhizomes of Petasites hybridus, primary amines and trialkyl phosphites in the presence of ZnO nanoparticles in water at room temperature. This procedure has advantages such as using natural products as precursors, employing water as a green solvent, good yields and easy separation of products.