Microwave-induced bismuth nitrate-catalyzed synthesis of dihydropyrimidones via Biginelli condensation under solventless conditions

Synthesis of dihydropyrimidinones via urea-based multicomponent reactions

Multicomponent reactions (MCRs) have emerged as powerful tools in organic chemistry, enabling the rapid and efficient assembly of complex molecular architectures. Urea-based multicomponent reactions have gained significant attention due to their versatility and broad applicability. In this review, we highlight recent developments in this area, with a focus on dihydropyrimidinones, and provide an in-depth analysis of the diverse synthetic pathways and applications of urea-based MCRs, shedding light on their fundamental mechanisms, reaction conditions, and potential for green and sustainable synthesis.

Synthesis, Molecular docking, and in silico ADME Studies of Dihydropyrimidine Derivatives using Tetrabutylphosphonium Methanesulphonate Ionic Liquid as a catalyst Under Solvent Free Conditions

This paper describes the synthesis and characterization of tetrabutylphosphonium methanesulphonate ionic liquid and its use for the first time as a catalyst in multicomponent reaction for one-pot synthesis of Dihydropyrimidine derivatives from various aromatic aldehydes, methyl or ethyl acetoacetate and urea or thio-urea under the solvent-free conditions at 120 oC. About twenty-one different dihydropyrimidine derivatives have been synthesized in excellent yields. The advantage of this method is a solvent-free condition, the requirement of a small amount of catalyst, shorter reaction time, easy workup procedure and non-involvement of any hazardous organic solvent and toxic catalyst. This catalyst was easily prepared and showed excellent level of reusability. Also the molecular docking study was performed to evaluate interactions between the active compounds with Leishmania Pteridine reductase 1(PTR1). Further the theoretical evaluation of ADME properties in silico was investigated for their oral bioavailability to predict the safer efficacy of the synthesized compounds.

Synthesis of dihydropyrimidinones via multicomponent reaction route over acid functionalized Metal-Organic framework catalysts

Multi component reactions over heterogeneous solid acid catalysts are extremely important owing to easy separation, amenable recycling, and prospective scaling up of the process. Here, we are reporting the synthesis of biologically important dihydropyrimidinones over postsynthetic modified Cr-based metal-organic framework materials as heterogeneous catalysts containing the bifunctional Lewis and Brønsted acid sites. Cr-based metal-organic frameworks contained coordinatively unsaturated metal sites as inherent Lewis acid sites, whereas postsynthetic modifications introduced the Brønsted acid sites in the framework. A direct one pot synthesis route was employed to produce the pristine MOF in pure aqueous medium without using any additives. The bulk structure, morphology, surface and bonding properties of the synthesized materials were thoroughly characterized with powder XRD, FTIR, XPS, FE-SEM, TGA, and N₂ sorption isotherms. A qualitative evolution of acid strength was carried out over the functionalized MOFs. Among the post synthetic functionalized materials, carboxylic acid functionalized framework exhibited a very high yield of dihydropyrimidinones under solvent less moderate reaction conditions. The catalyst also demonstrated a robust recyclability and wide substrate scope. Comparative study showed a very high catalytic activity of the postsynthetic modified MOFs in comparison to the reported literature. The reaction condition was optimized by varying parameters like solvent, temperature, reaction duration and catalyst loadings. The mechanistic studies indicated the involvement of both the Lewis and Brønsted sites acid sites of the catalysts in the multicomponent reaction.

A Brønsted acidic ionic liquid anchored to magnetite nanoparticles as a novel recoverable heterogeneous catalyst for the Biginelli reaction

In this study, simple and effective methods were used for the preparation of an ionic liquid that immobilized magnetite nanoparticles. Fe₃O₄ nanoparticles were prepared via a chemical co-precipitation method. Then, a SiO₂ shell was coated on the magnetic core via the Stober method. Finally, CPTES (chloropropyltriethoxysilane) and morpholine were coated on the SiO₂ shell. Morpholine sulfate, an acidic ionic liquid, was successfully bound to magnetite nanoparticles (Mag@Morph-AIL) and this was used as an efficient catalyst for the preparation of 3,4-dihydropyrimidinones. Compared to previous works, the easy separation of the nanocatalyst using an external magnet and the recyclability, non-toxicity, versatility, and high stability of the catalyst, combined with low reaction times and excellent yields, make the present protocol very useful for the synthesis of the title products. The synthesized products and catalyst were confirmed via ¹H-NMR, ¹³C-NMR, FT-IR, scanning electron microscope, X-ray diffraction, and elemental analysis.

Efficient synthesis of novel pyrazole-linked 1,2,4-triazolidine-3-thiones using bismuth on zirconium oxide as a recyclable catalyst in aqueous medium

The Bi₂O₃ loading on ZrO₂ as heterogeneous catalyst was established as an extremely efficient catalyst for the synthesis of a series of novel 5-(1-(2,4-dinitrophenyl)-3-substituted-phenyl-1H-pyrazol-4-yl)-1,2,4-triazolidine-3-thione derivatives (3a-o) with high yields (90-96%) by reaction of 1-(2,4-dinitrophenyl)-3-substituted-phenyl-1H-pyrazole-4-carbaldehydes and thiosemicarbazide using water as a greener solvent at 80 °C within 30-45 min. Materials with different percentages of Bi₂O₃ on ZrO₂ were prepared by simple wet impregnation method. The synthesized material has been characterized by various techniques (XRD, TEM, SEM, BET). 2.5% Bi₂O₃/ZrO₂ proved superior catalyst. The Bi₂O₃/ZrO₂ catalyst is easily recoverable and reused up to sixth run with no loss of activity. Excellent yields, short reaction time, avoidance of hazardous solvents, and no need for chromatographic purifications are the proven advantages.

Biginelli Reaction: Polymer Supported Catalytic Approaches

The Biginelli product, dihydropyrimidinone (DHPM) core, and its derivatives are of immense biological importance. There are several methods reported as modifications to the original Biginelli reaction. Among them, many involve the use of different catalysts. Also, among the advancements that have been made to the Biginelli reaction, improvements in product yields, less hazardous reaction conditions, and simplified isolation of products from the reaction predominate. Recently, solid-phase synthetic protocols have attracted the research community for improved yields, simplified product purification, recyclability of the solid support, which forms a special economic approach for Biginelli reaction. The present Review highlights the role of polymer-supported catalysts in Biginelli reaction, which may involve organic, inorganic, or hybrid polymers as support for catalysts. A few of the schemes involve magnetically recoverable catalysts where work up provides green approach relative to traditional methods. Some research groups used polymer-catalyst nanocomposites and polymer-supported ionic liquids as catalyst. Solvent-free, an ultrasound or microwave-assisted Biginelli reactions with polymer-supported catalysts are also reported.

Highly Efficient Synthesis of Substituted 3,4-Dihydropyrimidin-2-(1H)-ones (DHPMs) Catalyzed by Hf(OTf)₄: Mechanistic Insights into Reaction Pathways under Metal Lewis Acid Catalysis and Solvent-Free Conditions

In our studies on the catalytic activity of Group IVB transition metal Lewis acids, Hf(OTf)₄ was identified as a highly potent catalyst for "one-pot, three-component" Biginelli reaction. More importantly, it was found that solvent-free conditions, in contrast to solvent-based conditions, could dramatically promote the Hf(OTf)₄-catalyzed formation of 3,4-dihydro-pyrimidin-2-(1H)-ones. To provide a mechanistic explanation, we closely examined the catalytic effects of Hf(OTf)₄ on all three potential reaction pathways in both "sequential bimolecular condensations" and "one-pot, three-component" manners. The experimental results showed that the synergistic effects of solvent-free conditions and Hf(OTf)₄ catalysis not only drastically accelerate Biginelli reaction by enhancing the imine route and activating the enamine route but also avoid the formation of Knoevenagel adduct, which may lead to an undesired byproduct. In addition, ¹H-MMR tracing of the H-D exchange reaction of methyl acetoacetate in MeOH-d₄ indicated that Hf(IV) cation may significantly accelerate ketone-enol tautomerization and activate the β-ketone moiety, thereby contributing to the overall reaction rate.

A nanocrystalline CdS thin film as a heterogeneous, recyclable catalyst for effective synthesis of dihydropyrimidinones and a new class of carbazolyl dihydropyrimidinones via an improved Biginelli protocol

An improved Biginelli protocol for the efficient synthesis of a new class of carbazolyl dihydropyrimidinones mediated by CdS thin film nanoparticles deposited on the inner walls of a glass reactor as a recyclable, heterogeneous catalyst.

Recent developments in the synthesis and applications of dihydropyrimidin-2(1H)-ones and thiones

Dihydropyrimidin-2(1H)-ones/thiones (DHPMs) are important heterocyclic compounds owing to their excellent biological activities and have been widely utilized in pharmaceutical applications. Recently, numerous DHPM derivatives have been prepared. This review covers the synthesis of DHPMs and improved procedures for the preparation of DHPMs from 1995 to 2016.

Nanofibre Sepiolite Catalyzed Green and Rapid Synthesis of 2-Amino-4H-chromene Derivatives

Nanofibre sepiolite catalyzed the rapid, clean, and highly efficient synthesis of 2-amino-4H-chromene derivatives by a one-pot, three-component condensation of a series of aldehydes, various enolizable C–H bonds (such as dimedone, α-naphthol, resorcinol, and 4-hydroxy-2H-chromen-2-one), and malononitrile in a mixture of water/ethanol. The present method offers several advantages such as high to excellent yields, short reaction times, mild reaction conditions, simple procedure, use of inexpensive, non-toxic, and naturally available catalyst, easy isolation of the products, and no need for column chromatography. The catalyst could be easily separated from the reaction mixture and can be reused for many consecutive trials without a significant decline in its reactivity.

Recent synthetic and medicinal perspectives of dihydropyrimidinones: A review

Dihydropyrimidines are the most important heterocyclic ring systems which play an important role in the synthesis of DNA and RNA. Synthetically they were synthesized using Multi-component reactions like Biginelli reaction and Hantzschdihydropyridine. In the past decades, such Biginelli type dihydropyrimidones have received a considerable amount of attention due to the interesting pharmacological properties associated with this heterocyclic scaffold. In this review, we highlight recent developments in this area, with a focus on the DHPMs, recently developed as anti-inflammatory, anti-HIV, anti-tubercular, antifungal anticancer, antibacterial, antifilarial, antihyperglycemic, antihypertensive, analgesic, anti-convulsant, antioxidant, anti-TRPA1, anti-SARS, and anti-cancer activity and α_1a binding affinity.

•

This review is focused on synthetic prospective of dihydropyrimidinones.

•

This review is also focused on medicinal prospective of dihydropyrimidinones.

•

It includes structure-activity relationship study of different activities.

Synthesis of a BiFeO3 nanowire-reduced graphene oxide based magnetically separable nanocatalyst and its versatile catalytic activity towards multiple organic reactions

Herein, we report for the first time synthesis of a BiFeO₃ nanowire-reduced graphene oxide nanocatalyst (BFO–RGO) using a hydrothermal method.

An efficient synthesis of 3,4-Dihydropyrimidin-2(1H)-ones and thiones catalyzed by a novel Brønsted acidic ionic liquid under solvent-free conditions

We report here an efficient and green method for Biginelli condensation reaction of aldehydes, β-ketoesters and urea or thiourea catalyzed by Brønsted acidic ionic liquid [Btto][p-TSA] under solvent-free conditions. Compared to the classical Biginelli reaction conditions, the present method has the advantages of giving good yields, short reaction times, near room temperature conditions and the avoidance of the use of organic solvents and metal catalyst.

Bismuth nitrate-induced novel nitration of estradiol: an entry to new anticancer agents

Direct nitration of estradiol was carried out using metal nitrates on solid surfaces under mild condition, and a combination of bismuth nitrate pentahydrate impregnated KSF clay was found to be the best reagent to synthesize 2- and 4-nitroestradiol effectively. Furthermore, various basic side chains were introduced, through O-linker at C-3, to these nitroestradiols. The ability of these derivatives to cause cytotoxicity in Estrogen Receptor (ER)-positive and ER-negative breast cancer cell lines, as well as cancer cell lines of other origins, was examined. Qualitative structure activity relationship (SAR) has also been studied. We found that a basic side chain containing either a piperidine or morpholine ring, when conjugated to 2-nitroestradiol, was particularly effective at causing cytotoxicity in each of the cancer cell lines examined. Surprisingly, this effective cytotoxicity was even seen in ER-negative breast cancer cells.

A green approach toward quinoxalines and bis-quinoxalines and their biological evaluation against A431, human skin cancer cell lines

Background: The objective of this study was to develop a practical green procedure to synthesize quinoxalines and bis-quinoxalines and evaluate their inhibitory effects on the viability of A431 human epidermoid carcinoma cells. Method: A series of quinoxaline and bis-quinoxaline derivatives have been designed and synthesized following a microwave-assisted and bismuth nitrate-catalyzed eco-friendly route. A detailed comparison has been made between microwave-induced protocol with the reactions occurred at room temperature. The structure of the compounds have been elucidated by various spectroscopic methods and finally confirmed by x-ray crystallographic analyses. Results: Two quinoxaline derivatives, compounds 6 and 12 have demonstrated inhibitory effects on the viability of A431 human epidermoid carcinoma cells when compared with HaCaT nontumorigenic human keratinocyte cells. Conclusion: Notably, compound 6 inhibits Stat3 phosphorylation/activation in A431 skin cancer cells.

An Efficient Synthesis of 3,4-Dihydorpymidine(1H)-(thio)-Ones Catalyzed by Novel SO3H-Functionalized Ionic Liquids under Ultrasound Irradiation and Solvent Free Conditions

Novel SO3H-functionalized ionic liquids were successfully applied as catalysts for the one-pot three component Biginelli condensation under ultrasound irradiation without solvent. Various types of 3,4-dihydorpymidine(1H)-(thio)-ones were provided in 84-98% yields and conveniently separated from the reaction mixture by filtration, the dissolved catalyst could be reused with simple treatment. This novel synthetic method is especially favoured because it provides a synergy between ionic liquids and ultrasound irradiation which offers the advantages of high yields, short reaction times, simplicity, and easy workup compared to the conventional methods reported in the literature