Sulfated tungstate: An alternative, eco-friendly catalyst for Biginelli reaction

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.

Efficient and Recoverable Bio-Organic Catalyst Cysteine for Synthesis, Docking Study, and Antifungal Activity of New Bio-Active 3,4-Dihydropyrimidin-2(1H)-ones/thiones Under Microwave Irradiation

An eco-friendly green bio-organic catalyst and low-cost 3,4-dihydropyrimidin-2(1H)-ones/thione derivatives 4-7 have been synthesized using a high-yield, synthetic method via a one-pot, three-component process between 4-formylphenyl-4-methylbenzenesulfonate (1), thiourea, or urea and ethyl acetoacetate or acetylacetone under microwave irradiation in aqueous media of water and ethanol (3:1 ratio) as a green solvent in the presence of cysteine as a new green bio-organic catalyst. The reaction between compound 1, 4-(carbamothioylhydrazono) methyl]phenyl 4-methyl benzenesulfonate (3c), and ethyl acetoacetate or acetylacetone under the same condition afforded novel pyrimidines. Similarly, compound 1 was allowed to react with a mixture of 4-(carbamothioylhydrazono)methyl]phenyl 4-methyl benzenesulfonate (3c) and ethyl acetoacetate or acetylacetone under the same condition to afford pyrimidine derivatives 8 and 9. Excellent yields (90-98%) were obtained within short reaction times, and problems associated with the toxic solvents used (cost, safety, and pollution) were avoided. The structures of the new compounds were elucidated by elemental and spectral analyses. All compounds were studied using molecular docking, and their antifungal activity was investigated.

Niobium Oxides as Heterogeneous Catalysts for Biginelli Multicomponent Reaction

This study reports a simple, reusable, and recoverable niobium-based heterogeneous catalysts for Biginelli multicomponent reactions. Different methods of catalysts preparation were investigated. For this purpose, HY-340 (Nb₂O₅·nH₂O) and Nb₂O₅ were chemically and/or thermally treated and investigated as catalysts for dihydropyrimidinones (DHPMs) production. The catalysts were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, temperature-programmed desorption of NH₃, adsorption/desorption of N₂ at -196 °C, and thermogravimetric and differential thermal analysis. The characterization results showed that niobium oxides have the potential to be used as catalysts because of high crystallinity and large surface area. Among the tested catalysts, Nb₂O₅ chemically treated (Nb₂O₅/T) showed the best catalytic performance. In the absence of solvents, 94% yield of DHPMs was achieved. Also, Nb₂O₅/T can be reused three times without a significant yield decrease. Additionally, a feasible reaction pathway was suggested based on the Knoevenagel mechanism for DHPM synthesis using niobium-based catalysts.

One-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones catalyzed by SO3H@imineZCMNPs as a novel, efficient and reusable acidic nanocatalyst under solvent-free conditions

The synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives was accomplished efficiently via a three-component reaction between ethyl acetoacetate, various types of aldehydes, and urea in the presence of 10 mg SO₃H@imineZCMNPs as a novel, environment friendly, and reusable heterogeneous magnetic nanocatalyst under solvent-free conditions at 90 °C. The desired products were obtained with high quantitative yields. The catalyst was separated by simple isolation from the reaction mixture using a permanent magnet and reused several times without any significant loss of catalytic activity. The synthesized catalyst was fully characterized through various techniques including thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and the Hammett acidity test. This methodology tolerates most substrates and has the salient features of green reaction conditions, lower catalyst loading, high quantitative yields, low cost, the absence of solvents, and easy isolation and reusability of the catalyst.

Synthesis of 4-aryl-2-Thioxo-3,4-Dihydropyrimidines Using a Three-Component Reaction of Meldrum's Acid with Arylaldehydes and Acetylthiourea

A one-pot method for the preparation of new 4-aryl-2-thioxo-3,4-dihydropyrimidines via a three-component reaction of Meldrum's acid with arylaldehydes and acetylthiourea in the presence of p-toluenesulfonic acid as catalyst in CH3CN under reflux is reported.

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.

Sulfated polyborate: a new and eco-friendly catalyst for one-pot multi-component synthesis of 3,4-dihydropyrimidin-2(1H)-ones/thiones via Biginelli reaction

A highly efficient and improved synthetic methodology for the preparation of 3,4-dihydropyrimidin-2(1H)-one derivatives in good to excellent yield via Biginelli reaction of β-ketoesters/β-diketone, urea/thiourea and various aldehydes using new, efficient and recyclable sulfated polyborate catalyst under the solvent-free condition is reported.

Graphite catalyzed solvent free synthesis of dihydropyrimidin-2(1H)-ones/thiones and their antidiabetic activity

A solvent free three component condensation reaction between an aldehyde, ethyl acetoacetate and urea catalyzed by graphite, a green catalyst is described for the synthesis of dihydropyrimidin-2(1H)-ones. This protocol is scalable and the catalyst is reusable. This method is also applied for the synthesis of dihydropyrimidin-2(1H)-thiones. α-Amylase, a key enzyme in carbohydrate metabolism is generally targeted for management of type 2 diabetes. The therapeutic potential of the dihydropyrimidinones and dihydropyrimidinthiones to inhibit α-amylase activity was evaluated by in vitro assay. Of the synthesized compounds 3,4-dihydropyrimidin-2(1H)-thione (1k) demonstrated highest inhibition of α-amylase activity.

Phytic acid: a biogenic organocatalyst for one-pot Biginelli reactions to 3,4-dihydropyrimidin-2(1H)-ones/thiones

PhyA as a biogenic organocatalyst for Biginelli reactions under solvent-free conditions with good yields and by a plausible bifunctional mechanism.

Al(NO3)3 · 9H2O: An Efficient Catalyst for the One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Both under Reflux or Solvent-Free Conditions

Al(NO3)3 · 9H2O efficiently catalyzes the three-component Biginelli reaction between an aldehyde, aβ-dicarbonyl compound, and urea or thiourea in refluxing ethanol and solvent-free (SF) conditions to afford the corresponding dihydropyrimidinones in high yields. The advantages of this method involve the easy procedure, the environmentally friendly process, and the low cost of the Lewis acid catalyst.

Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones and Their Corresponding 2(1H)Thiones Using Trichloroacetic Acid as a Catalyst under Solvent-Free Conditions

Trichloroacetic acid was found to be a convenient catalyst for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones and their corresponding 2(1H)-thiones through a one-pot three-component reaction of aldehydes, alkyl acetoacetate, and urea or thiourea at 70°C under solvent-free conditions.