Chemo-/regioselective synthesis of 6-unsubstituted dihydropyrimidinones, 1,3-thiazines and chromones via novel variants of Biginelli reaction

Recent advances in transition metal-free annulation toward heterocycle diversity based on the C-N bond cleavage of enaminone platform

The enaminones and analogous stable enamines are well known as platform building blocks in organic synthesis for construction of heterocyclic compounds, especially N-heterocycles. To date, especially enaminones have been successfully...

Specific TLR4 Blocking Effect of a Novel 3,4-Dihydropyrimidinone Derivative

Background: Toll-like receptor 4 (TLR4) initiates both innate and adaptive immune responses, which plays an important protective role in self-defense mechanisms. Excessive or inappropriate TLR4 activation causes the development of many autoimmune diseases. Dihydropyrimidinone derivatives are medicinally important molecules with diverse pharmacological activities, including anti-inflammatory activity. The present study focused on novel synthesized 3,4-dihydropyrimidinone derivatives and evaluated their inhibitory effects on TLR4.

Methods: A series of 3,4-dihydropyrimidinone derivatives were recently synthesized and evaluated for their TLR4 inhibition activities and cytotoxic on HEK-Blue^TM hTLR4 cells with the help of QUANTI-Blue assay and MTS assay. Selected compound 3 was analyzed for its molecular docking with TLR4 by using Autodock vina 1.1.2. Its effect on the TLR4 pathway related cytokines was also evaluated in THP-1 cells and human peripheral blood mononuclear cells by using real-time PCR, ELISA and western blot.

Results: Five compounds were synthesized and characterized for effectiveness based on 3,4-dihydropyrimidinone. Compound 3 was found to be the potent hybrid among the synthesized compounds, with high TLR4 inhibition activities and low cytotoxic activities against HEK-Blue^TM hTLR4 cells. Molecular docking analysis showed that two hydrogen bonds between compound 3 and residues Asp209(TLR4) and Asp99(MD-2) mainly contribute to the TLR4 inhibition. In addition, compound 3 suppressed LPS-induced of the mRNA expression of TLR4, IP-10, TNF-α, IL-6, IL-12A, and IL-12B, the protein expression of pIRF3 and pNFκB and the secretion of IP-10, TNF-α in THP-1 cell line. Compound 3 also inhibited LPS-induced expression of TNF-α, IL-6, and IL-1β but increased IP-10 at mRNA levels in human peripheral blood mononuclear cells.

Conclusion: Our study reveals compound 3, a novel 3,4-dihydropyrimidinone derivative, is a potential TLR4 antagonist, which opens up new research avenues for the development of promising therapeutic agents for inflammatory and autoimmune diseases.

The construction of fluorophoric thiazolo-[2,3-b]quinazolinone derivatives: a multicomponent domino synthetic approach

Acid-mediated one-pot domino reactions of substituted 2-amino thiazoles, substituted benzaldehydes and cyclic diketones have been developed for the synthesis of novel and architecturally unique thiazolo[2,3-b]quinazolinone derivatives under microwave irradiation. In this protocol, a series of thiazolo[2,3-b]quinazolinone derivatives have been synthesized and the excellent fluorescence behaviors of some of the molecules have been reported based on the incorporation of different electron-donating and electron-withdrawing substituents on the aryl moieties of the target molecules.

A library of unique fluorophoric thiazolo[2,3-b]quinazolinones were synthesized under acid catalyzed one pot microwave irradiation technique.

An unorthodox metal-free synthesis of dihydro-6H-quinoline-5-ones in ethanol/water using a non-nucleophilic base and their cytotoxic studies on human cancer cell line

One-pot metal-free catalysed green methodology for dihydro-6H-quinoline-5-ones and their biological activities in HeLa cells.

An efficient synthesis of 4,5-diaryl-3,4-dihydropyrimidin-2(1H)-one via a cesium carbonate-promoted direct condensation of 1-aryl-2-propanone with 1,1′-(arylmethylene)diurea

An efficient method for the synthesis of 4,5-diaryl-3,4-dihydropyrimidin-2(1H)-one by using 1,1′-(arylmethylene)diurea and 1-aryl-2-propanone as substrates was developed. The reactions proceeded efficiently in the presence of Cs₂CO₃ to give the desired products in moderate to good yields with wide substrate scope and good functional group tolerance, serving as an attractive alternative or complement to the previously reported methods for the facile assembly of biologically and pharmaceutically active 3,4-dihydropyrimidin-2(1H)-ones.

A Cs₂CO₃-promoted efficient method for the synthesis of 4,5-diaryl-3,4-dihydropyrimidin-2(1H)-one by using 1,1′-(arylmethylene)diurea and 1-aryl-2-propanone as substrates was developed.

Toward C2-nitrogenated chromones by copper-catalyzed β-C(sp2)–H N-heteroarylation of enaminones

The synthesis of C2-nitrogenated chromones has been performed via reactions of enaminones and nitrogen nucleophiles based on an unconventional β-C–H bond functionalization and a featured chromone annulation of enaminones.

Visible-light-mediated arylation of ortho-hydroxyarylenaminones: direct access to isoflavones

The first visible-light-promoted direct synthesis of isoflavones following the arylation of ortho-hydroxyarylenaminones by aryl onium salts was developed.

Cesium-Carbonate-Mediated Benzalation of Substituted 2-Aryl-3-nitro-2 H-chromenes with Substituted 4-Benzylidene-2-phenyloxazol-5(4 H)-ones

Cs₂CO₃-mediated domino benzalation reaction with a variety of 2-aryl-3-nitro-2 H-chromenes and 4-benzylidene-2-phenyloxazol-5(4 H)-ones has been realized. The reaction proceeds smoothly with a broad substrate scope, thus providing a variety of substituted ( Z)-4-(( Z)-benzylidene)chroman-3-one oximes in moderate to high yields, which were easily transformed into biologically important 4 H-chromeno[3,4- c]isoxazoles.

Copper(i)-catalyzed N–H olefination of sulfonamides for N-sulfonyl enaminone synthesis

A novel approach for synthesis of N-sulfonyl enaminones in one-step from saturated ketones and provide an entry into accessing functionalization at α- and β-position of carbonyl group simultaneously.

Synthesis of quinolines via copper-catalyzed domino reactions of enaminones

Enaminones showcase synthetic utility for the synthesis of quinoline derivatives via copper-catalyzed domino reactions involving C–N bond formation, aldol reaction and dehydration.

Recent developments in chemical reactivity of N,N-dimethylenamino ketones as synthons for various heterocycles

This review demonstrates the high number of synthetic applications of enaminones in the preparation of acyclic, carbocyclic, heterocyclic and fused heterocyclic compounds.

Practical synthesis of symmetrical thioureas and heterocyclic thiones in water

A simple and practical protocol for the synthesis of symmetric thioureas and heterocyclic thiones has been developed. It involves the reaction of amines with phenyl chlorothionoformate in water to afford the symmetrical thioureas or heterocyclic thiones in good to excellent yields. Various amines including aromatic, aliphatic and chiral amines survived the reaction conditions. Mild conditions, simple work-up and high yields as well as using water as solvent are the major advantages of this protocol.

A Novel Mechanistic Study on Ultrasound-Assisted, One-Pot Synthesis of Functionalized Benzimidazo[2,1-b]quinazolin-1(1H)-ones

Ultrasound-assisted synthesis of benzimidazo[2,1-b]quinazolin-1(1H)-ones was achieved via piperidine-catalyzed three-component reaction of 2-aminobenzimidazoles, an aromatic aldehyde, and 1,3-dione in aqueous isopropanol. This mechanism was first suspected following our identification of unusual reaction intermediates in a one-pot reaction. An unprecedented coupling reaction, it involved a nucleophilic attack by 2-aminobenzimidazole on in situ generated Michael adduct, followed by electrocyclic ring formation reaction. In contrast to the commonly accepted mechanism, that the direct reaction of 2-amino benzimidazole with a Knoevenagel adduct cannot deliver target compounds.

A facile strategy for accessing 3-alkynylchromones through gold-catalyzed alkynylation/cyclization of o-hydroxyarylenaminones

A strategy based on tandem alkynylation ofo-hydroxyarylenaminones followed by intramolecular cyclization has been developed to generate a diverse array of 3-alkynyl chromones.

Synthesis of β,β-diaryl propiophenones via palladium-catalyzed domino arylboronation, elimination and enone hydroarylation of enaminones

The first example of a domino reaction involving enaminone C–N conversion-based arylation has been realized as an efficient new route toward the synthesis of β,β-diaryl propiophenones.

Regioselective three-component reactions of enaminones, 2-aminopyridines and enals for the synthesis of 1,2-dihydropyridines

A novel regioselective, metal-free and broadly applicable three-component approach for the synthesis of 1,2-dihydropyridines has been established.

General solvent-free ionic liquid catalyzed C–N/C–C coupled cyclization to diverse dihydropyrimidinones and new organic materials: Langmuir–Blodgett film study

An ionic liquid catalyzed dual C–N/C–C coupled cyclization under solvent-free green conditions to DHPMs and their innovative new organic materials by LB film study are demonstrated.

Secondary amine-initiated three-component synthesis of 3,4-dihydropyrimidinones and thiones involving alkynes, aldehydes and thiourea/urea

The three-component reactions of aldehydes, electron deficient alkynes and ureas/thioureas have been smoothly performed to yield a class of unprecedented 3,4-dihydropyrimidinones and thiones (DHPMs). The reactions are initiated by the key transformation of an enamine-type activation involving the addition of a secondary amine to an alkyne, which enables the subsequent incorporation of aldehydes and ureas/thioureas. This protocol tolerates a broad range of aryl- or alkylaldehydes, N-substituted and unsubstituted ureas/thioureas and alkynes to yield the corresponding DHPMs with specific regioselectivity.

Metal-free synthesis of cyano acrylates via cyanuric chloride-mediated three-component reactions involving a cascade consists of Knoevenagel condensation/cyano hydration/esterification

The synthesis of cyano acrylates has been achieved via an organocatalytic domino Knoevenagel reaction, hydration and esterification under metal-free conditions without using any additional solvent.

Metal-free synthesis of 1,3,5-trisubstituted benzenes by the cyclotrimerization of enaminones or alkynes in water

The trimeric cyclization reactions of enaminones proceed efficiently in water to provide C3 symmetric benzenes in the presence of lactic acid.

Efficient synthesis of dihydropyrimidinones via a three-component Biginelli-type reaction of urea, alkylaldehyde and arylaldehyde

A one-pot three-component synthesis of dihydropyrimidinones via a molecular iodine-catalyzed tandem reaction of simple readily available mono-substituted urea, alkylaldehyde, and arylaldehyde has been developed. The reaction proceeds with high chemo- and regioselectivity to give highly diverse dihydropyrimidinones in reasonable yields under mild reaction conditions. Moreover, the first catalytic enantioselective version of this reaction was also realized by using chiral spirocyclic SPINOL-phosphoric acids.